Patent Description:
Graphene is a hexagonal monolayer structure composed of carbon (C) atoms. Graphene is structurally and chemically stable and has good electrical and physical characteristics. For example, graphene has a charge mobility (e.g., about <NUM>×<NUM><NUM> cm<NUM>/Vs) that is at least <NUM> times or higher than the charge mobility of silicon (Si), and a current density (e.g., about <NUM><NUM> A/cm<NUM>) that is at least <NUM> times higher than the current density of copper (Cu). Furthermore, graphene may have a very high Fermi velocity (VF). Graphene may include a monoatomic layer, or multilayer graphene may be formed by stacking several monoatomic layers on one another. As a result, graphene has drawn attention as a next-generation material that may overcome the limits of the materials in the related art.

Because of the various merits of graphene, research into applying graphene to several electronic devices has been conducted. In this connection, graphene needs to have semiconductor characteristics. However, it may be difficult to form graphene including a pn junction having good characteristics according to existing methods.

<CIT> discloses a graphene layer and a method of forming the graphene layer. <CIT> discloses a graphene-based device formed with a substrate having a trench therein. <NPL>, discloses a single-step doping method to fabricate n- and p-type multilayer graphene. <NPL>, discloses a back-gate graphene p-n junction. <CIT> discloses a semiconductor device using multi-layered graphene wires.

One or more exemplary embodiments provide a multilayer graphene having good characteristics and physical properties, and a method of forming the multilayer graphene.

One or more exemplary embodiments also provide a multilayer graphene having good pn junction properties, and a method of forming the multilayer graphene.

One or more exemplary embodiments also provide a multilayer graphene having a narrow depletion region existing at a pn junction boundary, and a method of forming the multilayer graphene.

One or more exemplary embodiments also provide a patterned multilayer graphene and a method of forming the patterned multilayer graphene.

One or more exemplary embodiments also provide a multilayer graphene having a defect-free edge portion, and a method of forming the multilayer graphene.

One or more exemplary embodiments also provide a device (graphene-containing device) including the multilayer graphene.

One or more exemplary embodiments also provide a method of manufacturing the device including the multilayer graphene.

According to an aspect of the invention, a method of forming a multilayer graphene is provided in accordance with claim <NUM>.

The method may further comprise forming a second multilayer graphene on a second area of the first graphene adjacent to the first area at a third temperature by using a third source gas, the second multilayer graphene comprising a portion of the first graphene corresponding to the second area, wherein the second temperature is different from the third temperature, or wherein the second source gas is different from the third source gas.

The first graphene may be a monolayer graphene. As another example, the first graphene may be a bilayer graphene, or a multilayer graphene including three or more layers.

At least one of the first multilayer graphene and the second multilayer graphene may be a bilayer graphene.

One of the first multilayer graphene and the second multilayer graphene may be of a p-type and the other may be of an n-type, and the first multilayer graphene and the second multilayer graphene may form a pn junction, wherein the p-type multilayer graphene is formed due to a doping effect of the underlayer, and the n-type multilayer graphene is formed due to an n-type dopant included in the first or second source gas.

The second source gas and the third source gas may be the same. Each of the second source gas and the third source gas may include a nitrogen (N)-containing hydrocarbon compound. The N-containing hydrocarbon compound may include pyridine (C<NUM>H<NUM>N). The second temperature may be <NUM> or greater, and the third temperature may be <NUM> or less.

The first multilayer graphene may be a p-type, and the second multilayer graphene may be an n-type.

The first multilayer graphene may be formed as a p type as a result of the doping effect of the underlayer, and the second multilayer graphene may be formed as an n-type due to an n-type dopant present in the second source gas.

The first source gas and the second source gas may be different from each other. For example, one of the first source gas and the second source gas may include a first hydrocarbon compound and the other may include a second hydrocarbon compound. The first hydrocarbon compound may not contain N, and the second hydrocarbon compound may contain N.

The method may further include forming a third multilayer graphene directly joined or indirectly joined to the first multilayer graphene or the second multilayer graphene, and the third multilayer graphene may be of a p type or an n type. For example, the first through third multilayer graphenes may form a pnp or npn structure.

The first multilayer graphene and the second multilayer graphene may both be of a p-type conductive type or an n-type conductive type and may have different doping concentrations from each other. The first second gas and the third source gas may be the same. Each of the second source gas and the third source gas may include an N-containing hydrocarbon compound. The N-containing hydrocarbon compound may include pyridine (C<NUM>H<NUM>N). The second temperature may be <NUM> to <NUM>, and the third temperature may be <NUM> or less. The first graphene may be formed at the first temperature by using the first source gas. The first multilayer graphene may be of an n-type, and the second multilayer graphene may be of an n+-type.

The first multilayer graphene may be formed using a first mask that exposes the first area of the first graphene, and the second multilayer graphene may be formed using a second mask that exposes the second area of the first graphene. Alternatively, the first and second multilayer graphenes may be randomly distributed.

The underlayer may include a catalyst metal. For example, the catalyst metal may include platinum (Pt) or gold (Au). As another example, the catalyst metal may include Al, Ag, Cu, Ti, Co, Ni, or Pd.

The forming of the underlayer may include forming a first material layer on a substrate and forming a plurality of underlayers spaced apart from one another by patterning the first material layer.

According to another aspect of the invention, a method of manufacturing a graphene-containing device is provided in accordance with claim <NUM>.

The multilayer graphene may be formed on a first substrate, and the device unit may be formed on a second substrate after the multilayer graphene is transferred from the first substrate to the second substrate. Alternatively, the multilayer graphene may be formed on the first substrate, and the device unit may also be formed on the first substrate.

According to another aspect of the invention, a graphene-containing device is provided in accordance with claim <NUM>.

The graphene-containing device may be a diode, and the graphene-containing device may further include a first electrode connected to the first multilayer graphene and a second electrode connected to the second multilayer graphene.

The graphene-containing device may be a transistor, and the multilayer graphene may be used as a channel layer. The multilayer graphene may have a pnp or npn structure.

The graphene-containing device may include one of a tunneling device, a binary junction transistor (BJT), a barristor, a field effect transistor (FET), a memory device, a solar cell, a photodetector, a sensor, and a light-emitting device.

The above and/or other aspects will become apparent and more readily understood from the following description of exemplary embodiments, taken in conjunction with the accompanying drawings in which:.

A multilayer graphene, a method of forming the same, a device including the multilayer graphene, and a method of manufacturing the device will now be described in detail with reference to the accompanying drawings. Like reference numerals in the drawings denote like elements, and, in the drawings, the sizes of elements may be exaggerated for clarity and for convenience of explanation. It will be understood that when a material layer is referred to as being "formed on" or "adjacent to" a substrate, an area, an item, or another layer, it can be directly or indirectly formed on or adjacent to the substrate, area, item, or other layer. That is, for example, intervening substrates, areas, items, or layers may be present. Materials that constitute each layer in exemplary embodiments below are exemplary, and thus the other materials may be used.

<FIG> are cross-sectional views illustrating a method of forming a multilayer graphene, according to an exemplary embodiment.

Referring to <FIG>, a substrate <NUM> having an underlayer <NUM> formed thereon is prepared. The substrate <NUM> may be, for example, a silicon (Si) substrate, but may be any other suitable substrate. The underlayer <NUM> may be a material layer including a catalyst for forming graphene on the material layer. The catalyst may be a metal. Accordingly, the underlayer <NUM> may be referred to as a catalyst metal layer. For example, the underlayer <NUM> may include platinum (Pt) as the catalyst. In such a case, the underlayer <NUM> may be a Pt layer.

Next, a graphene forming process may be conducted at a first temperature T10 by using a first source gas <NUM>. The first source gas <NUM> may be injected into a chamber including the substrate <NUM> to adsorb the material of the first source gas <NUM> to an exposed area (namely, a first area) of the underlayer <NUM>. The substrate <NUM> or the chamber may be heated to the first temperature T10. The injection of the first source gas <NUM> may be followed by the heating, or the heating may be followed by the injection of the first source gas <NUM>. Alternatively, the heating and the injection may be conducted simultaneously. As a result, as shown in <FIG>, a first graphene <NUM> may be formed on the underlayer <NUM>. The first graphene <NUM> may be formed as a monolayer (a monoatomic layer) by, for example, adjusting the duration of the heating.

A process of forming the first graphene <NUM> in <FIG> may be a sort of chemical vapor deposition (CVD). The formation of the first graphene <NUM> by using the first source gas <NUM> and the first temperature T10 will be described later in more detail.

Referring to <FIG>, a first mask layer <NUM> may be formed on the substrate <NUM> so as to leave open a first area A1 of the first graphene <NUM> and so as to cover the remaining area thereof. The first mask layer <NUM> may be formed from metal, a metal compound, oxide, nitride, or the like, or may be formed from polymer that is usable at a relatively high temperature (for example, about <NUM> or greater).

Next, a first multilayer graphene forming process may be conducted at the first temperature T10 by using the first source gas <NUM>. The first source gas <NUM> may be injected into the chamber, and the substrate <NUM> or the chamber may be heated to the first temperature T10. Similar to the aforementioned example, the injection of the first source gas <NUM> may be followed by the heating, or the heating may be followed by the injection of the first source gas <NUM>, or the heating and the injection may be conducted simultaneously. Consequently, the material of the first source gas <NUM> may be adsorbed to the underlayer <NUM> via a first graphene 141a (see <FIG>) of the first area A1 to thereby form additionally a second graphene <NUM> (see <FIG>). Accordingly, a first multilayer graphene 140a may be formed in the first area A1. The second graphene <NUM> formed in the first area A1 may also be a monolayer graphene. In this case, the first multilayer graphene 140a may be a bilayer graphene.

Next, as shown in <FIG>, the first mask layer <NUM> of <FIG> is removed.

Next, as shown in <FIG>, a second mask layer <NUM> is formed on the first multilayer graphene 140a so as to cover the first multilayer graphene 140a. The second mask layer <NUM> exposes a second area A2 of the first graphene <NUM>, the second area A2 including no first multilayer graphenes 140a. The second area A2 may be adjacent to the first area A1.

Next, a second graphene forming process may be conducted on the second area A2 of the first graphene <NUM>, which is not covered with the second mask layer <NUM> and which is exposed, by using a second source gas <NUM> at a second temperature T20.

The second source gas <NUM> may be injected into the chamber including the substrate <NUM>, and the substrate <NUM> or the chamber may be heated to the second temperature T20. The injection of the second source gas <NUM> may be followed by the heating, or the heating may be followed by the injection of the second source gas <NUM>, or the heating and the injection may be conducted simultaneously. Consequently, the material of the second source gas <NUM> may be adsorbed to the underlayer <NUM> via a first graphene 141b (see <FIG>) of the second area A2 to thereby form a third graphene <NUM> (see <FIG>). Accordingly, as shown in <FIG>, a second multilayer graphene 140b may be formed in the second area A2. The third graphene <NUM> formed in the second area A2 may also be a monolayer graphene. In this case, the second multilayer graphene 140b may be a bilayer graphene.

Since the first and second multilayer graphenes 140a and 140b are respectively formed in the first and second areas A1 and A2 adjacent to each other, the first and second multilayer graphenes 140a and 140b contact each other on the same plane. In other words, the second multilayer graphene 140b may be joined to a lateral surface of the first multilayer graphene 140a.

According to the present exemplary embodiment, the first source gas <NUM> of <FIG> may be the same as the second source gas <NUM> of <FIG>. In this case, the first source gas <NUM> and the second source gas <NUM> may include a nitrogen (N)-containing hydrocarbon compound. The N-containing hydrocarbon compound may include, for example, pyridine (C<NUM>H<NUM>N). In other words, both the first source gas <NUM> and the second source gas <NUM> may be a pyridine (C<NUM>H<NUM>N) gas. Even when the same source gases <NUM> and <NUM> are used as described above, first and second multilayer graphenes 140a and 140b having different semiconductor types may be formed, as will be described later, by using different process temperatures T10 and T20. The first temperature T10 for forming the first graphene <NUM> or the first multilayer graphene 140a may be about <NUM> or greater, and the second temperature T20 for forming the second multilayer graphene 140b may be about <NUM> or less. In more detail, the first temperature T10 may be about <NUM> to about <NUM>, and the second temperature T20 may be about <NUM> to about <NUM>.

In <FIG>, when the first source gas <NUM> includes pyridine (C<NUM>H<NUM>N) and the first temperature T10 is about <NUM> or greater, not only the hydrogen (H) in pyridine, but also the N in pyridine may be dissolved and removed at this high temperature. Accordingly, the first multilayer graphene 140a of <FIG> may not include N atoms. Since N atoms may serve as an n-type dopant for graphene, the N atoms may not be included in the first multilayer graphene 140a. In this case, the first multilayer graphene 140a may be p-type graphene as a result of a doping effect caused by the underlayer <NUM>.

<FIG> is a diagram showing the structure of a dominant energy band of a bilayer graphene. The Fermi level was set to zero. Referring to <FIG>, the bilayer graphene has a bandgap structure. This may be understood as having a bandgap while the symmetry of the electrical interaction of carbon (C) atoms is collapsed as the graphene forms a bilayer. When the bilayer graphene is formed on Pt, the intermediate value of the bandgap of the bilayer graphene increases by several hundreds of mV (for example, about <NUM> mV) with respect to the Fermi level due to the Pt. As described above, the first multilayer graphene 140a may be a bilayer graphene. In this case, as shown in <FIG>, the first multilayer graphene 140a (bilayer graphene) may have bandgap opening with p-type semiconductor characteristics. Many Si-based semiconductor devices use the bandgap property of semiconductors. However, a monolayer graphene has a zero bandgap because the π-band and the π+-half-filled band meet at the Dirac points, and, even when the Dirac points are moved upwards or downwards from the Fermi level by doping the monolayer graphene, the zero bandgap is continuously maintained. Accordingly, there is a limit in applying, without changes, such a monolayer graphene to many existing Si-based semiconductor devices. However, a multilayer graphene <NUM> (bilayer graphene) (see, e.g., <FIG>) manufactured according to the present exemplary embodiment opens a bandgap as a result of a bilayer structure, and thus existing bandgap characteristics of semiconductors that have been used in the existing art may also be used. In <FIG>, when the second source gas <NUM> includes pyridine and the second temperature T20 is about <NUM> or less, the N in the pyridine may not be removed at this relatively low temperature, and may be used together with C to form the third graphene <NUM> of <FIG>. Even when the first temperature T10 is about <NUM> or greater, and thus most of the N atoms of the first graphene <NUM> are removed in <FIG>, the N of the pyridine permeates into the first graphene <NUM> of the second area A2 in the second multilayer graphene forming process of <FIG>, and thus, as shown in <FIG>, the first graphene 141b of the second area A2 is doped with N atoms. Accordingly, the second multilayer graphene 140b of <FIG> may include N atoms. Since the N atoms may be an n-type dopant, the second multilayer graphene 140b may have n-type semiconductor characteristics due to the N atoms. Similar to the above description, the second multilayer graphene 140b may be formed as a bilayer. In this case, the second multilayer graphene 140b may have a bandgap structure as a result of a bilayer effect. In other words, the second multilayer graphene 140b may have bandgap opening with n-type semiconductor characteristics.

By adjusting the second temperature T20, the doping concentration of the second multilayer graphene 140b may be adjusted, because the amount of N atoms included in the second multilayer graphene 140b varies depending on the second temperature T20. As the second temperature T20 decreases (for example, being closer to about <NUM>), the n-doping concentration of the second graphene 140b may increase. On the other hand, as the second temperature T20 increases (for example, being closer to about <NUM>), the n-doping concentration of the second multilayer graphene 140b may decrease. Accordingly, the doping concentration of the second multilayer graphene 140b may be easily controlled by adjusting the second temperature T20 within a predetermined range.

As such, since one type of source gas is used, but different process temperatures are used in a graphene growth operation, p-type and n-type multilayer graphenes (i.e., 140a and 140b) may be very easily formed. Since one type of source gas is used, the process is simplified, leading to reductions in manufacturing costs and manufacturing duration. A junction, namely, a pn junction, between the p-type and n-type multilayer graphenes (i.e., 140a and 140b) formed according to a method as described above may have good characteristics. Since the p-type and n-type multilayer graphenes (i.e., 140a and 140b) may have a defect-free structure or a structure having little defect, the multilayer graphene <NUM> including the p-type and n-type multilayer graphenes 140a and 140b may have good characteristics and physical properties. The crystalline structure and features of the multilayer graphene <NUM> will be described in more detail later with reference to <FIG> and the like.

When the first multilayer graphene 140a is formed and in this state the second multilayer graphene 140b is formed using the second source gas <NUM> and the second temperature T20, C atoms move toward the most energetically stable place. In this respect, the second multilayer graphene 140b may grow from the lateral surface of the first multilayer graphene 140a. Accordingly, the boundary between the first multilayer graphene 140a and the second multilayer graphene 140b may have no or little defects. In other words, the bond between the first multilayer graphene 140a and the second multilayer graphene 140b may approximate to a chemical bond. Accordingly, the first multilayer graphene 140a and the second multilayer graphene 140b may be considered to form a pn junction. The first multilayer graphene 140a and the second multilayer graphene 140b may constitute the multilayer graphene <NUM> of <FIG>. In other words, the multilayer graphene <NUM> may be considered to have a pn junction structure.

Although the underlayer <NUM> includes Pt as a catalyst material in the present exemplary embodiment, embodiments of the present disclosure are not limited thereto. For example, even when the underlayer <NUM> includes gold (Au) as a catalyst, the bandgap of the first multilayer graphene 140a may increase with respect to the Fermi level due to the Au in the underlayer <NUM>, and thus the first multilayer graphene 140a may have a p-type conductivity.

As another example, when the underlayer <NUM> includes a metal catalyst such as Al, Ag, Cu, Ti, Co, Ni, or Pd, the bandgap of the first multilayer graphene 140a may decrease with respect to the Fermi level and thus the first multilayer graphene 140a may have an n-type conductivity. In this case, by appropriately selecting the second source gas <NUM> and the second temperature T20, the first multilayer graphene 140a and the second multilayer graphene 140b may have a n-n+ junction or an np junction.

<FIG> is a perspective view of the multilayer graphene <NUM> completely formed using the method according to the present exemplary embodiment. Referring to <FIG>, the multilayer graphene <NUM> includes the first and second multilayer graphenes 140a and 140b. The multilayer graphene <NUM> may be formed on the underlayer <NUM> on the substrate <NUM>. As described above, the first and second multilayer graphenes 140a and 140b may be cemented together in a lateral direction. The first multilayer graphene 140a may be a first type semiconductor, and the second multilayer graphene 140b may be a second type semiconductor. As described above, since the first multilayer graphene 140a has a bandgap-open p-type conductivity and the second multilayer graphene 140b has a bandgap-open n-type conductivity, the first and second multilayer graphenes 140a and 140b may form a pn junction.

According to the present exemplary embodiment, the first graphene <NUM> is a monolayer graphene, and the first multilayer graphene 140a and the second multilayer graphene 140b are bilayer graphenes. However, the embodiments of the present disclosure are not limited thereto. Thus, the first graphene <NUM> may be grown as a bilayer or a multilayer of three or more layers by, for example, adjusting the duration of the heating process. Similarly, each of the second and the third graphenes <NUM> and <NUM> may be grown as a bilayer or a multilayer of three or more layers. When the first graphene <NUM> is a bilayer graphene and each of the second and the third graphenes <NUM> and <NUM> is a monolayer graphene, the first multilayer graphene 140a and the second multilayer graphene 140b may be trilayer graphenes. Alternatively, when the first graphene <NUM> is a monolayer graphene and each of the second and the third graphenes <NUM> and <NUM> is a bilayer graphene, the first multilayer graphene 140a and the second multilayer graphene 140b may be trilayer graphenes. The electrical characteristics of such a trilayer graphene vary with the stacking order. For example, a Bernal (ABA stack type) trilayer graphene has semi-metallic characteristics having a tunable band. Also, a rhombohedral (ABC stack type) trilayer graphene has semiconductor characteristics having a tunable bandgap. As another example, the first graphene <NUM> may be formed as a monolayer graphene and the second and the third graphenes <NUM> and <NUM> may be formed as multilayer graphenes, or the first graphene <NUM> may be formed as a multilayer graphene and the second and the third graphenes <NUM> and <NUM> may be formed as monolayer graphenes, or all of the first graphene <NUM> and the second and the third graphenes <NUM> and <NUM> may be multilayer graphenes. As another example, the number of layers included in the first multilayer graphene 140a may be different from the number of layers included in the second multilayer graphene 140b. It will be understood by one of ordinary skill in the art that the number of layers included in the first graphene <NUM> and the number of layers included in each of the second and the third graphenes <NUM> and <NUM> may be appropriately selected according to desired characteristics.

According to the present exemplary embodiment, the p-type and n-type multilayer graphenes (i.e., 140a and 140b) are formed using the same source gases <NUM> and <NUM>. However, according to another exemplary embodiment, the p-type and n-type multilayer graphenes (i.e., 140a and 140b) may be formed using different source gases. This exemplary embodiment is illustrated in <FIG>.

<FIG> are cross-sectional views illustrating a method of manufacturing a multilayer graphene, according to another exemplary embodiment.

Referring to <FIG>, a substrate <NUM> on which an underlayer <NUM> is formed is prepared. The underlayer <NUM> may include a catalyst such as Pt, Ni, Cu, Ir, or the like. As shown in <FIG>, a first graphene <NUM> is formed on the underlayer <NUM> by using a first source gas <NUM> at a first temperature T11. The first graphene <NUM> may be formed as a monolayer (monoatomic layer) by, for example, adjusting the duration of a heating process. The first graphene <NUM> may also be grown as a bilayer or a multilayer of three or more layers by, for example, extending the duration of the heating process.

Next, referring to <FIG>, a first mask layer <NUM> may be formed so as to open a first area B1 of the first graphene <NUM> and cover the remaining area thereof. This may be similar to the structure of <FIG> in which the underlayer <NUM> and the first mask layer <NUM> are formed on the substrate <NUM>. The first mask layer <NUM> may be formed from metal, a metal compound, oxide, nitride, or like, or may be formed from a polymer. Next, a first multilayer graphene forming process may be conducted at a second temperature T21 by using a second source gas <NUM>.

As a result of the first multilayer graphene forming process of <FIG>, as shown in <FIG>, the area of the first graphene <NUM> not covered with the first mask layer <NUM>, namely, the first area B1, may become a first multilayer graphene 240a. In other words, the material of the second source gas <NUM> may be adsorbed to the underlayer <NUM> via the exposed first area B1 of the first graphene <NUM> to thereby form a second graphene <NUM> (see <FIG>). Accordingly, the first multilayer graphene 240a may be formed in the first area B1. The second graphene <NUM> formed in the first area B1 may also be a monolayer graphene. In this case, the first multilayer graphene 240a may be a bilayer graphene. Alternatively, the second graphene <NUM> may be grown as a bilayer or a multilayer of three or more layers. In this case, the first multilayer graphene 240a may be a multilayer graphene including three or more layers.

Referring to <FIG>, after the first mask layer <NUM> of <FIG> is removed, a second mask layer <NUM> may be formed on the first multilayer graphene 240a. The second mask layer <NUM> may be formed from metal, a metal compound, oxide, nitride, or like, or may be formed from a polymer. The second mask layer <NUM> exposes a second area B2 of the first graphene <NUM>, the second area B2 including no first multilayer graphenes 240a. A second multilayer graphene forming process may be conducted on the second area B2 at a third temperature T31 by using a third source gas <NUM>. Consequently, the material of the third source gas <NUM> is adsorbed to the underlayer <NUM> via a first graphene 241b of the second area B2 to thereby form a third graphene <NUM> (see <FIG>). The third graphene <NUM> formed in the second area B2 may also be a monolayer graphene. In this case, a second multilayer graphene 240b (see <FIG>) may be a bilayer graphene. Alternatively, the third graphene <NUM> may be grown as a bilayer or a multilayer of three or more layers. In this case, the second multilayer graphene 240b may be a multilayer graphene including three or more layers.

Consequently, as shown in <FIG>, the second graphene bilayer 240b joined with the first graphene bilayer 240a may be formed in the second area B2. The third graphene <NUM> formed in the second area B2 may also be a monolayer graphene. In this case, the second multilayer graphene 240b may be a bilayer graphene. The first multilayer graphene 240a and the second multilayer graphene 240b may constitute a multilayer graphene <NUM>. As described above, the first multilayer graphene 240a and the second multilayer graphene 240b may be bilayers. In this case, the multilayer graphene <NUM> may be a bilayer graphene.

According to the present exemplary embodiment, the second source gas <NUM> of <FIG> may be different from the third source gas <NUM> of <FIG>. For example, the second source gas <NUM> may include a first hydrocarbon compound, and the third source gas <NUM> may include a second hydrocarbon compound. The first hydrocarbon compound may not contain N, and the second hydrocarbon compound may contain N. For example, the second source gas <NUM> may include a hydrocarbon compound, such as benzene (C<NUM>H<NUM>), ethylene (C<NUM>H<NUM>), or acetylene (C<NUM>H<NUM>). The hydrocarbon compound may be composed of only C and H. The second source gas <NUM> may include a boron (B)-containing hydrocarbon compound, for example, triethylborane (C<NUM>H<NUM>B). Accordingly, the second source gas <NUM> may include at least one of the hydrocarbon compounds including benzene (C<NUM>H<NUM>), ethylene (C<NUM>H<NUM>), acetylene (C<NUM>H<NUM>), and triethylborane (C<NUM>H<NUM>B). The third source gas <NUM> may include a N-containing hydrocarbon compound, for example, pyridine (C<NUM>H<NUM>N). As such, when the second source gas <NUM> and the third source gas <NUM> are different, the second temperature T21 and the third temperature T31 may be different from each other or may be the same as each other. The second temperature T21 may be higher than the third temperature T31, or vice versa. In some cases, the two temperatures T21 and T31 may be equal to each other or may be similar to each other.

In <FIG>, when the second source gas <NUM> includes benzene (C<NUM>H<NUM>), ethylene (C<NUM>H<NUM>), or acetylene (C<NUM>H<NUM>), the second temperature T21 may be about <NUM> to about <NUM>. When the second source gas <NUM> includes triethylborane (C<NUM>H<NUM>B), the second temperature T21 may be about <NUM> to about <NUM>. Under this condition, the first multilayer graphene 240a of <FIG> may have a p-type conductivity. Accordingly, the second temperature T21 may have a wide range of about <NUM> to about <NUM>. When the second source gas <NUM> includes a hydrocarbon compound such as benzene (C<NUM>H<NUM>), ethylene (C<NUM>H<NUM>), or acetylene (C<NUM>H<NUM>), the first multilayer graphene 240a may be composed of only C atoms and may have p-type semiconductor characteristics due to the underlayer <NUM>. When the second source gas <NUM> includes a hydrocarbon compound such as triethylborane (C<NUM>H<NUM>B), the first multilayer graphene 240a may include B atoms and may have p-type semiconductor characteristics due to the B atoms. B may serve as a p-type dopant for graphene. As described above, the first multilayer graphene 240a may be a bilayer. In this case, the first multilayer graphene 240a may be p-type bilayer graphene having bandgap opening.

The first source gas <NUM> of <FIG> may be the same as or different from the second source gas <NUM> of <FIG>. For example, the first source gas <NUM> of <FIG> may be the same as the second source gas <NUM> of <FIG>, and the first temperature T11 may be equal to the second temperature T21. As another example, the first source gas <NUM> and the first temperature T11 of <FIG> may be the same as the first source gas <NUM> and the first temperature T10 of <FIG>.

In <FIG>, when the third source gas <NUM> includes pyridine (C<NUM>H<NUM>N), the third temperature T31 may be about <NUM> or less. In this case, the formed second multilayer graphene 240b of <FIG> may be an n-type multilayer graphene including N atoms, which is the same as presented above with respect to the second multilayer graphene 140b with reference to <FIG>. The third temperature T31 may be in a range of about <NUM> to about <NUM>. As described above, the second multilayer graphene 240b may be a bilayer. In this case, the second multilayer graphene 240b may be an n-type bilayer graphene having bandgap opening.

Consequently, the bandgap of the multilayer graphene <NUM> formed according to the present exemplary embodiment is open, and the multilayer graphene <NUM> may be a pn-junctioned bilayer graphene. By appropriately selecting the number of layers included in the first graphene <NUM> and the number of layers included in each of the second and the third graphenes <NUM> and <NUM> according to desired characteristics, the multilayer graphene <NUM> may be a multilayer graphene including three or more layers.

According to the exemplary embodiment of <FIG>, the first multilayer graphene 240a may be a p-type and the second multilayer graphene 240b may be an n-type. According to another exemplary embodiment, an n-type multilayer graphene may be formed first, and a p-type multilayer graphene may then be formed. For example, by reversing the first multilayer graphene forming process of <FIG> and the second multilayer graphene forming process of <FIG>, the n-type multilayer graphene may be first formed, and the p-type multilayer graphene may then be formed. In this case, to prevent damage to the n-type multilayer graphene during formation of the p-type multilayer graphene, the temperature for forming the p-type multilayer graphene may be less than or equal to the temperature for forming the n-type multilayer graphene.

Referring to <FIG>, a substrate <NUM> on which an underlayer <NUM> is formed is prepared. The substrate <NUM> and the underlayer <NUM> may be the same as or similar to the substrate <NUM> and the underlayer <NUM> of <FIG> or the substrate <NUM> and the underlayer <NUM> of <FIG>.

As shown in <FIG>, a first graphene <NUM> is formed on the underlayer <NUM> by using a first source gas <NUM> at a first temperature T13. The process of <FIG> may be the same as or similar to the first graphene forming process of <FIG> or <FIG>.

Next, referring to <FIG>, a first mask layer <NUM> may be formed so as to open a first area C1 of the first graphene <NUM> and so as to cover the remaining area thereof. This may be similar to the structure of <FIG> in which the underlayer <NUM> and the first mask layer <NUM> are formed on the substrate <NUM>. The first mask layer <NUM> may be formed from metal, a metal compound, oxide, nitride, or like, or may be formed from a polymer. Next, a first multilayer graphene forming process may be conducted on the first area C1 at a second temperature T23 by using a second source gas <NUM>.

The second source gas <NUM> and the second temperature T23 may correspond to the first source gas <NUM> and the first temperature T10 of <FIG>, respectively, or may correspond to the second source gas <NUM> and the second temperature T21 of FIG. 3C, respectively.

As a result of the first multilayer graphene forming process of <FIG>, as shown in <FIG>, a first multilayer graphene 340a including a first graphene 341a of the first area C1 and a second graphene <NUM> may be formed. The first multilayer graphene 340a may be, for example, a p-type bilayer graphene including a bandgap opening.

Referring to <FIG>, after the first mask layer <NUM> of <FIG> is removed, a second mask layer <NUM> may be formed. A second area C2 of the first graphene <NUM> may not be covered by the second mask layer <NUM> and may be exposed. Next, a second multilayer graphene forming process may be conducted on the second area C2 at a third temperature T33 by using a third source gas <NUM>. The third source gas <NUM> and the third temperature T33 may correspond to the second source gas <NUM> and the second temperature T20 of <FIG>, respectively, or may correspond to the third source gas <NUM> and the third temperature T31 of FIG. 2E, respectively.

As a result of the second multilayer graphene forming process of <FIG>, as shown in <FIG>, a second multilayer graphene 340b including a first graphene 341b of the second area C2 and a third graphene <NUM> may be formed. The second multilayer graphene 340b may be, for example, an n-type bilayer graphene including a bandgap opening.

Referring to <FIG>, after the second mask layer <NUM> of <FIG> is removed, a third mask layer <NUM> may be formed. A third area C3 of the first graphene <NUM> may not be covered with the third mask layer <NUM> and may be exposed. Next, a third multilayer graphene forming process may be conducted on the exposed third area C3 of the first graphene <NUM>. At this time, a fourth source gas <NUM> and a fourth temperature T43 may be used. The fourth source gas <NUM> may include a boron (B)-containing hydrocarbon compound, for example, triethylborane (C<NUM>H<NUM>B), or include a hydrocarbon compound, such as benzene (C6H6), ethylene (C<NUM>H<NUM>), or acetylene (C<NUM>H<NUM>). When the second multilayer graphene 340b formed by the third source gas <NUM> is an n-type and a third multilayer graphene 340c of <FIG> formed by the fourth source gas <NUM> is a p-type, the fourth temperature T43 for forming the third multilayer graphene 340c may be less than or equal to the third temperature T33 for forming the second multilayer graphene 340b. This may be to prevent damage to the second multilayer graphene 340b during formation of the third multilayer graphene 340c. For example, the fourth temperature T43 may be less than about <NUM> or less than about <NUM>.

As a result of the third multilayer graphene forming process of <FIG>, as shown in <FIG>, a third multilayer graphene 340c including a first graphene 341c of the third area C3 and a fourth graphene <NUM> may be formed. The third multilayer graphene 340c may be, for example, a p-type bilayer graphene including a bandgap opening.

In <FIG>, the first through third multilayer graphenes 340a, 340b, and 340c may constitute a multilayer graphene <NUM>. The multilayer graphene <NUM> may be considered to have a pnp junction structure. As described above, the first through third multilayer graphenes 340a, 340b, and 340c may be bilayers. In this case, the multilayer graphene <NUM> may have a bandgap. Sizes and shapes of the first through third multilayer graphenes 340a, 340b, and 340c may vary. By appropriately selecting the number of layers included in the first graphene <NUM> of <FIG> and the number of layers included in each of the second, the third, and the fourth graphenes <NUM>, <NUM>, and <NUM> of <FIG>, and <FIG> according to desired characteristics, the multilayer graphene <NUM> may be a multilayer graphene including three or more layers.

Although <FIG> illustrate and describe a method of forming the multilayer graphene <NUM> having a pnp structure, it will be understood by one of ordinary skill in the art that a multilayer graphene having an npn structure may also be formed.

As shown in <FIG>, a first graphene <NUM> is formed on the underlayer <NUM> by using a first source gas <NUM> at a first temperature T14. The process of <FIG> and <FIG> may be the same as or similar to the first graphene forming process of <FIG> or <FIG>. The first graphene <NUM> may be formed as a monolayer by, for example, adjusting the duration of the heating process. The first graphene <NUM> may also be grown as a bilayer or a multilayer of three or more layers by, for example, extending the duration of the heating process.

Next, referring to <FIG>, a mask layer <NUM> may be formed so as to cover a portion of the first graphene <NUM>. The mask layer <NUM> may be formed from metal, a metal compound, oxide, nitride, or like, or may be formed from a polymer. Next, a multilayer graphene forming process may be conducted at a second temperature T24 by using a second source gas <NUM>. The multilayer graphene forming process of <FIG> may be the same as the first multilayer graphene forming process of <FIG> or the second multilayer graphene forming process of <FIG>. The multilayer graphene forming process of <FIG> may be the same as the first multilayer graphene forming process of <FIG> or the second multilayer graphene forming process of <FIG>.

As a result of the multilayer graphene forming process of <FIG>, as shown in <FIG>, the area of the first graphene <NUM> not covered with the mask layer <NUM> may become a multilayer graphene <NUM>. In other words, the material of the second source gas <NUM> may be adsorbed to the underlayer <NUM> via an exposed first graphene 441a to thereby form a second graphene <NUM>. Accordingly, the multilayer graphene <NUM> may be formed in the area not covered with the mask layer <NUM>. Similar to the above description, the multilayer graphene <NUM> may be, for example, a p-type bilayer graphene including bandgap opening or an n-type bilayer graphene including a bandgap opening. When the first graphene <NUM> or the second graphene <NUM> is a bilayer or a multilayer of three or more layers, the multilayer graphene <NUM> may be a multilayer graphene including three or more layers.

The first graphene 441b that remains without the multilayer graphene <NUM> being formed thereon in <FIG> may have a p-type or n-type conductivity due to a doping effect of the underlayer <NUM>. For example, when the underlayer <NUM> includes Pt or Au and the first graphene <NUM> is formed as a monolayer as described above, the remaining first graphene 441b may have a closed bandgap and have an energy band structure in which Dirac points have simply moved upward from the Fermi level, namely, the p-type conductivity.

Thus, the remaining first graphene 441b and the multilayer graphene <NUM> may form a pn junction or a pp junction, and may form a junction of a zero-bandgap structure and a non-zero bandgap structure. By appropriately selecting the number of layers included in the first graphene <NUM> and the number of layers included in the second graphene <NUM> according to desired characteristics, the multilayer graphene <NUM> may possess a junction structure between multilayer graphenes including different layers.

<FIG> are cross-sectional views illustrating a method of manufacturing a multilayer graphene, according to another exemplary embodiment. <FIG> is a plan view of a multilayer graphene randomly formed according to the method according to the exemplary embodiment of <FIG>.

A first graphene <NUM> of <FIG> is formed on the underlayer <NUM> by using a first source gas <NUM> at a first temperature T15. The process of <FIG> may be the same as or similar to the first graphene forming process of <FIG> or <FIG>. The first graphene <NUM> may be formed as a monolayer by, for example, adjusting the duration of the heating process. The first graphene <NUM> may also be grown as a bilayer or a multilayer of three or more layers by, for example, extending the duration of the heating process.

Next, as shown in <FIG>, a process of forming a first multilayer graphene 540a of <FIG> may be conducted at a second temperature T25 by using a second source gas <NUM>. The process of <FIG> of forming the first multilayer graphene 540a may be conducted without any masks, and the size of the first multilayer graphene 540a may be controlled by adjusting the duration of the process. Since no masks are used, the material of the second source gas <NUM> may be adsorbed to a random area on the first graphene <NUM> to thereby form additionally second graphenes <NUM> (see <FIG>). Accordingly, a first multilayer graphene 540a (see <FIG>) may be randomly and irregularly formed on the underlayer <NUM>. Since the process of forming the first multilayer graphene 540a is stopped before the second graphene <NUM> expands on the entire area of the underlayer <NUM>, the second graphene <NUM> may be a monolayer graphene. The second graphene <NUM> and a first graphene 541a located thereon constitutes the first multilayer graphene 540a. The process of forming the first multilayer graphene 540a may be similar to the first multilayer graphene forming process of <FIG> or the first multilayer graphene forming process of <FIG> except that no masks are used.

Next, as shown in <FIG>, a process of forming a second multilayer graphene 540b of <FIG> may be conducted at a third temperature T35 by using a third source gas <NUM>. The process of <FIG> of forming the second multilayer graphene 540b may be conducted without any masks, and the size of the second multilayer graphene 540b may be controlled by adjusting the duration of the process. When the first multilayer graphene 540a is formed and in this state a third graphene <NUM> is formed using the third source gas <NUM> and the third temperature T35, C atoms move toward the most energetically stable place. Thus, the third graphene <NUM> may grow from a lateral surface of the second graphene <NUM>. The third graphene <NUM> and a first graphene 541b located thereon constitutes the second multilayer graphene 540b. Since the process of forming the second multilayer graphene 540b is stopped before the third graphene <NUM> invades the area of the second graphene <NUM>, the third graphene <NUM> may be a monolayer graphene.

Consequently, as shown in <FIG>, the first multilayer graphene 540a and the second multilayer graphene 540b are joined together at an arbitrary interface and constitute a multilayer graphene <NUM>. When the first graphene <NUM> is a monolayer, the multilayer graphene <NUM> may be a bilayer.

As shown in <FIG>, multilayer graphenes <NUM> may be randomly distributed on the underlayer <NUM>, and the first graphene <NUM> may remain on some areas of the underlayer <NUM>. By appropriately adjusting the durations for forming the first and second multilayer graphenes 540a and 540b, the first and second multilayer graphenes 540a and 540b may be randomly distributed over the entire surface of the underlayer <NUM> and may be densely formed.

Various devices including multilayer graphenes such as the multilayer graphene <NUM> having the above random structure, either on the same substrate or having been transferred to another substrate may be manufactured.

As shown in <FIG>, a first graphene <NUM> is formed on the underlayer <NUM> by using a first source gas <NUM> at a first temperature T16. The process of <FIG> may be the same as or similar to the first graphene forming process of <FIG> or <FIG>. The first graphene <NUM> may be formed as a monolayer by, for example, adjusting the duration of the heating process. The first graphene <NUM> may also be grown as a bilayer or a multilayer of three or more layers by, for example, extending the duration of the heating process.

Next, referring to <FIG>, a first mask layer <NUM> may be formed so as to open a first area D1 of the first graphene <NUM> and so as cover the remaining area thereof. This may be similar to the structure of <FIG> in which the underlayer <NUM> and the first mask layer <NUM> are formed on the substrate <NUM>. The first mask layer <NUM> may be formed from metal, a metal compound, oxide, nitride, or like, or may be formed from a polymer. Next, a first multilayer graphene forming process may be conducted at a second temperature T26 by using a second source gas <NUM>.

As a result of the first multilayer graphene forming process of <FIG>, as shown in <FIG>, an area of the first graphene <NUM> not covered with the first mask layer <NUM>, namely, the first area D1, may become a first multilayer graphene 640a. In other words, the material of the second source gas <NUM> may be adsorbed to the underlayer <NUM> via the exposed first area D1 of the first graphene <NUM> to thereby form a second graphene <NUM> (see <FIG>). Accordingly, the first multilayer graphene 640a may be formed in the first area D1.

Referring to <FIG>, after the first mask layer <NUM> of <FIG> is removed, a second mask layer <NUM> may be formed on the first multilayer graphene 640a. The second mask layer <NUM> may be formed from metal, a metal compound, oxide, nitride, or like, or may be formed from a polymer. The second mask layer <NUM> exposes a second area D2 of the first graphene <NUM>, the second area D2 including no first multilayer graphene 640a. A second multilayer graphene forming process may be conducted on the second area D2 at a third temperature T36 by using a third source gas <NUM>.

As a result of the second multilayer graphene forming process of <FIG>, as shown in <FIG>, a second multilayer graphene 640b joined with the first multilayer graphene 640a may be formed. The first multilayer graphene 640a and the second multilayer graphene 640b may constitute a multilayer graphene <NUM>.

According to the present exemplary embodiment, the first multilayer graphene 640a and the second multilayer graphene 640b may have the same type of conductivity and different doping concentrations. The first multilayer graphene 640a may be, for example, an n-type bilayer graphene having an open bandgap, and the second multilayer graphene 640b may be, for example, an n+-type bilayer graphene having an open bandgap. Alternatively, the first multilayer graphene 640a may be, for example, an n+-type bilayer graphene having an open bandgap, and the second multilayer graphene 640b may be, for example, an n-type bilayer graphene having an open bandgap. As another example, the first multilayer graphene 640a may be, for example, a p-type bilayer graphene having an open bandgap, and the second multilayer graphene 640b may be, for example, a p+-type bilayer graphene having an open bandgap. Alternatively, the first multilayer graphene 640a may be, for example, a p+-type bilayer graphene having an open bandgap, and the second multilayer graphene 640b may be, for example, a p-type bilayer graphene having an open bandgap.

For example, the second source gas <NUM> and the third source gas <NUM> may include a N-containing hydrocarbon compound, for example, pyridine (C<NUM>H<NUM>N). When forming the first multilayer graphene 640a, the second temperature T26 may be set below <NUM> (for example, <NUM> to <NUM>) so that some amount of N remains in the first multilayer graphene 640a. When forming the second multilayer graphene 640b, the third temperature T36 may be set to be <NUM> or less so that a higher amount of N remains in the second multilayer graphene 640b than in the first multilayer graphene 640a. In other words, by setting a doping concentration of the second multilayer graphene 640b to be higher than that of the first multilayer graphene 640a, a multilayer graphene <NUM> having a bandgap-open nn+ junction structure may be formed.

By appropriately selecting the number of layers included in the first graphene <NUM> of <FIG> and the number of layers included in the second graphene <NUM> of <FIG> according to desired characteristics, the multilayer graphene <NUM> may have a structure in which multilayer graphenes having the same type of conductivity and each including three or more layers are cemented together.

<FIG> are perspective views illustrating a method of manufacturing a multilayer graphene, according to another exemplary embodiment.

Referring to <FIG>, a first material layer <NUM> may be formed on a substrate <NUM>. The substrate <NUM> may be formed from a material that is the same as or similar to that used to form the substrates <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> of <FIG>. The first material layer <NUM> may be formed from a material that is the same as or similar to that used to form the underlayers <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> of <FIG>. The first material layer <NUM> may be a catalyst material layer. The catalyst material layer may be a metal layer.

Referring to <FIG>, the first material layer <NUM> may be patterned to form a plurality of underlayers <NUM> spaced apart from one another. Each of the plurality of underlayer <NUM> may be the same as or similar to the underlayers <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> of <FIG>.

Referring to <FIG>, a multilayer graphene <NUM> may be formed on each of the plurality of underlayers <NUM>. The multilayer graphene <NUM> may include a first multilayer graphene 740a and a second multilayer graphene 740b. The first multilayer graphene 740a and the second multilayer graphene 140b may be cemented together. For example, one of the first multilayer graphene 740a and the second multilayer graphene 740b may have a bandgap-open p-type conductivity, the other may have a bandgap-open n-type conductivity, and the multilayer graphene <NUM> may be a bilayer graphene having a bandgap-open pn junction structure. The method of forming the multilayer graphene <NUM> may be the same as or similar to the method of <FIG> of forming the multilayer graphene <NUM>, the method of <FIG> of forming the multilayer graphene <NUM>, the method of <FIG> of forming the multilayer graphene <NUM>, the method of <FIG> of forming the multilayer graphene <NUM>, and the method of <FIG> of forming the multilayer graphene <NUM>. Although the multilayer graphene <NUM> has a pn structure in <FIG>, the multilayer graphene <NUM> may have a pnp structure or an npn structure. When the multilayer graphene <NUM> has a pnp or npn structure, the method of forming the multilayer graphene <NUM> may be the same as or similar to that described above with reference to <FIG>.

As shown in the method of <FIG>, when the plurality of underlayers <NUM> are formed by patterning the first material layer <NUM>, and then the multilayer graphene <NUM> is formed on each of the plurality of underlayers <NUM>, a plurality of multilayer graphenes <NUM> patterned in a desired shape may be easily manufactured.

If a single graphene sheet is formed on (or transferred onto) a substrate and then a plurality of multilayer graphenes spaced apart from one another are formed by patterning (etching) the single graphene sheet, an edge portion of each multilayer graphene may be damaged due to the patterning (etching). A portion of photoresist (PR) that is used during the patterning (etching) may remain in the multilayer graphenes, and thus the physical properties of the multilayer graphenes and the characteristics of a device including the multilayer graphenes may degrade. Controlling the shapes or sizes of the multilayer graphenes according to a method of directly patterning the graphene sheet may be difficult. However, according to an exemplary embodiment of the present disclosure, since the plurality of multilayer graphenes <NUM> are formed on the plurality of pre-patterned underlayers <NUM>, damage to edge portions of the multilayer graphenes <NUM> may be prevented, and the problem of photoresist remaining behind may also be prevented. Moreover, since etching (patterning) the first material layer <NUM> may be easier than directly etching (patterning) a graphene sheet, when the first material layer <NUM> is etched (patterned) and then patterned multilayer graphenes <NUM> are formed on a resultant structure, it may be easy to control the size and shape of the multilayer graphenes <NUM>.

<FIG> is a plan view of a structure of a multilayer graphene 840A according to an exemplary embodiment.

Referring to <FIG>, the multilayer graphene 840A may be formed on an underlayer <NUM>. The multilayer graphene 840A may include a p-type multilayer graphene 840p and an n-type multilayer graphene 840n. The n-type multilayer graphene 840n may be joined to a lateral surface of the p-type multilayer graphene 840p. The p-type multilayer graphene 840p and the n-type multilayer graphene 840n may each have a structure in which a plurality of monolayer graphenes are stacked.

A plurality of monolayer graphenes that constitute the n-type multilayer graphene 840n have a hexagonal crystal structure comprised of C atoms. In the crystal structure, some of the C atoms are replaced with first atoms. The first atoms may be, for example, N atoms. N atoms may serve as an n-type dopant. According to the present exemplary embodiment, both N atoms and C atoms constitute a hexagonal crystal structure. However, atoms other than N atoms may be used. A plurality of monolayer graphenes that constitute the p-type multilayer graphene 840p may have a hexagonal crystal structure comprised of only C atoms. The p-type multilayer graphene 840p may have p-type semiconductor characteristics due to a doping effect of the underlayer <NUM> disposed below the p-type multilayer graphene 840p. The underlayer <NUM> may include Pt as a catalyst metal. However, the material used to form the underlayer <NUM> is not limited to Pt, and various modifications may be made thereto.

According to the present exemplary embodiment, a depletion region (DR) formed at a boundary between the p-type multilayer graphene 840p and the n-type multilayer graphene 840n may have an extremely small width, for example, about <NUM> or less. The width of the depletion region DR may be about <NUM> or less. According to the present exemplary embodiment, the n-type multilayer graphene 840n may have n-type semiconductor characteristics due to the replacement of C atoms with the first atoms (for example, N atoms). In this case, the first atoms (for example, N atoms) may be uniformly or relatively uniformly distributed within the n-type multilayer graphene 840n. The p-type multilayer graphene 840p may have p-type semiconductor characteristics due to a change (increase) in a bandgap due to the underlayer <NUM>. In this case, the junction between the p-type multilayer graphene 840p and the n-type multilayer graphene 840n may have a size (width) on an atomic scale, and the depletion region DR having an extremely small width may be formed between the p-type multilayer graphene 840p and the n-type multilayer graphene 840n. As described above, the width of the depletion region DR may be about <NUM> or less or about <NUM> or less. An n-doping effect due to N atoms may disappear when further from locations of N atoms by about <NUM> or greater. Thus, the width of the depletion region DR may be about <NUM> or less. No or little defects may be generated at the boundary between the p-type multilayer graphene 840p and the n-type multilayer graphene 840n formed according to the methods as described above. As such, since the depletion region DR formed between the p-type graphene 840p and the n-type graphene 840n has a small width and no or little defects exist on the boundary therebetween, the multilayer graphene 840A may have good characteristics and physical properties.

Manufacturing a multilayer graphene having a narrow depletion region at a pn junction according to existing methods or methods according to comparative examples may be difficult. For example, when a p-type doped region and an n-type doped region are formed on a graphene sheet by making different organic material layers (molecular layers) in contact with the graphene sheet, it is difficult to control the boundary between the p-type doped region and the n-type doped region at a small scale, and thus the boundary may not be pronounced and the pn junction characteristics may degrade. The boundary between the p-type doped region and the n-type doped region may have a width of several tens of µm or greater, for example, about <NUM>. Thus, it is difficult to obtain good pn junction characteristics, and it is also difficult to manufacture a graphene device having a small size (width) that is <NUM> or less. These problems may equally (or similarly) occur even when a pn junction is formed by forming a metal oxide layer on a portion of a graphene sheet via deposition. However, according to an exemplary embodiment, since the boundary (depletion region) between the p-type multilayer graphene 840p and the n-type multilayer graphene 840n may be formed at an extremely small scale of several nm or less, good pn junction characteristics may be obtained, and a small graphene device may be easily manufactured.

Moreover, according to an exemplary embodiment, the entire edge portion of the multilayer graphene 840A may have a defect-free crystalline structure. For example, the entire edge portion of the multilayer graphene 840A may have a defect-free zigzag structure. Since the multilayer graphene 840A is formed on the patterned underlayer <NUM> instead of directly patterning (etching) a graphene sheet, the edge portion of the multilayer graphene 840A may have a defect-free crystal structure. Thus, the multilayer graphene 840A may provide good characteristics, and a graphene device including the multilayer graphene 840A may have good performance.

The width w1 of the multilayer graphene 840A may be several nm to several hundreds of nm. Width w1 denotes a width of the multilayer graphene 840A in a shorter-axis direction. The width w1 of the multilayer graphene 840A may be, for example, about <NUM> or less or about <NUM> or less. When the patterned underlayer <NUM> is formed and then the multilayer graphene 840A is formed thereon, a multilayer graphene 840A having a width w1 of about <NUM> or less or about <NUM> or less and a defect-free edge portion may be easily formed. Forming a multilayer graphene having a width of about <NUM> or less according to an existing method, for example, by directly etching (patterning) a graphene sheet may be difficult, and the multilayer graphene may have degraded characteristics due to defects of an edge portion thereof. Since PR that is used during the etching (patterning) remains on the multilayer graphene, the characteristics of the multilayer graphene may also be degraded. According to an exemplary embodiment, these problems may be prevented or addressed, and a multilayer graphene having good characteristics may be easily formed.

In addition, when a plurality of underlayers corresponding to a formed pattern are formed and then a plurality of multilayer graphenes are formed thereon (see <FIG>), the size and shape of each of the multilayer graphenes may be easily controlled, and the interval between two adjacent multilayer graphenes may also be easily controlled to several tens of nm or several nm. Thus, the methods and the structures according to the present disclosure are usefully applicable to a device using two adjacent multilayer graphenes (for example, a device of <FIG> which will be described later).

<FIG> is a plan view of a structure of a multilayer graphene 840B according to another exemplary embodiment.

Referring to <FIG>, the multilayer graphene 840B may include a p-type multilayer graphene 841p and an n-type multilayer graphene 841n. The n-type multilayer graphene 841n may have substantially the same crystal structure as that of the n-type multilayer graphene 840n of <FIG>. In other words, a plurality of monolayer graphenes that constitute the n-type multilayer graphene 841n have a hexagonal crystal structure comprised of C atoms. In the crystal structure, some of the C atoms may be replaced with first atoms. The first atoms may be, for example, N atoms. A plurality of monolayer graphenes that constitute the p-type multilayer graphene 841p have a hexagonal crystal structure comprised of C atoms. In the crystal structure, some of the C atoms may be replaced with second atoms that are different from the first atoms. The second atoms may be, for example, B atoms. B atoms may serve as a p-type dopant. An underlayer may be disposed below the p-type and n-type multilayer graphenes 841p and 841n. The underlayer may include a catalyst metal. The catalyst metal may include, for example, Pt, Cu, Ni, or Ir.

According to the present exemplary embodiment, a depletion region DR having a very small width may be formed at a boundary between the p-type multilayer graphene 841p and the n-type multilayer graphene 841n. The width of the depletion region DR may be, for example, about <NUM> or less or about <NUM> or less. Each of the p-type multilayer graphene 841p and the n-type multilayer graphene 841n may have good doping uniformity. The entire edge portion of the multilayer graphene 840B may have a defect-free crystalline structure, for example, a defect-free zigzag structure. The width w1 of the multilayer graphene 840B in a shorter-axis direction may be several nm to several hundreds of nm, for example, about <NUM> or less or about <NUM> or less.

The multilayer graphenes 840A or 840B of <FIG> or <FIG> may correspond to one of the multilayer graphenes of <FIG>. In other words, at least a portion of one of the multilayer graphenes of <FIG> may have the structure of the multilayer graphenes 840A or 840B of <FIG> or <FIG>. For example, the first multilayer graphene 140a and the second multilayer graphene 140b of <FIG> may respectively correspond to the p-type multilayer graphene 840p and the n-type multilayer graphene 840n of <FIG>. The first multilayer graphene 240a and the second multilayer graphene 240b may respectively correspond to the p-type graphene 840p and the n-type graphene 840n of <FIG> or may respectively correspond to the p-type multilayer graphene 841p and the n-type multilayer graphene 841n of <FIG>.

For reference, the honeycomb unit structure that constitutes the hexagonal structure of each of the multilayer graphenes 840A and 840B of <FIG> and <FIG> has a size that is arbitrarily determined for convenience, and the ratio between the actual length of the depletion region DR and the actual size of the honeycomb unit structure may be different from that shown in <FIG> and <FIG>. In other words, although the depletion region DR has a size corresponding to about two honeycomb unit structures in <FIG> and <FIG>, the actual size of the depletion region DR may be different from the size illustrated in <FIG> and <FIG>. In addition, the ratio between the size of the honeycomb unit structure and the width w1 of each of the multilayer graphenes 840A and 840B may be different from the actual ratio.

A method of manufacturing a device including a multilayer graphene (i.e., a graphene-containing device) according to an exemplary embodiment will now be described.

<FIG> are perspective views illustrating a method of manufacturing a graphene-containing device, according to an exemplary embodiment.

Referring to <FIG>, after an underlayer <NUM> is formed on a first substrate <NUM>, a multilayer graphene <NUM> having a pn junction structure may be formed on the underlayer <NUM>. The multilayer graphene <NUM> may include a first multilayer graphene <NUM> and a second multilayer graphene <NUM>. The first multilayer graphene <NUM> may be a p-type multilayer graphene, and the second multilayer graphene <NUM> may be an n-type multilayer graphene. The first and second multilayer graphenes <NUM> and <NUM> may be bilayer graphenes each having a bandgap. According to desired characteristics, the first and second multilayer graphenes <NUM> and <NUM> may be multilayer graphenes including three or more layers. The method of forming the multilayer graphene <NUM> on the first substrate <NUM> may be the same as or similar to the methods described with reference to <FIG>.

Referring to <FIG>, the multilayer graphene <NUM> of the first substrate <NUM> may be transferred to a second substrate <NUM>. The method of transferring the multilayer graphene <NUM> from the first substrate <NUM> to the second substrate <NUM> may any well-known graphene transferring method. The second substrate <NUM> may be a semiconductor substrate or an insulative substrate. The semiconductor substrate may be, for example, a silicon substrate. When a semiconductor substrate is used, an insulating layer may be formed on the semiconductor substrate, and then the multilayer graphene <NUM> may be transferred onto the insulating layer. A conductive substrate may also be used as the second substrate <NUM>. In such a case, after an insulating layer is formed on the conductive substrate, the multilayer graphene <NUM> may be transferred onto the insulating layer.

Referring to <FIG>, a device unit including the multilayer graphene <NUM> may be formed on the second substrate <NUM>. For example, a first electrode <NUM> may be connected to (contact) the first multilayer graphene <NUM>, and a second electrode <NUM> may be connected to (contact) the second multilayer graphene <NUM>. Since the multilayer graphene <NUM> has a pn junction structure, the multilayer graphene <NUM> and the first and second electrodes <NUM> and <NUM> in contact with the multilayer graphene <NUM> may constitute a diode device <NUM>. As described above, the multilayer graphene <NUM> may be a bilayer graphene having a bandgap. In this case, the diode device <NUM> may secure the characteristics of a pn-junction semiconductor device having a bandgap.

<FIG> are cross-sectional views illustrating a method of manufacturing a graphene-containing device, according to another exemplary embodiment.

Referring to <FIG>, an underlayer <NUM> and a multilayer graphene <NUM> may be formed on a first substrate <NUM>. The multilayer graphene <NUM> may be a bilayer graphene having a bandgap. According to desired characteristics, the multilayer graphene <NUM> may be a multilayer graphene including three or more layers. The method of forming the underlayer <NUM> and the multilayer graphene <NUM> on the first substrate <NUM> may be the same as or similar to the method described with reference to <FIG>.

Referring to <FIG>, the multilayer graphene <NUM> of the first substrate <NUM> may be transferred to a second substrate <NUM>. This may be the same as or similar to the transferring method described with reference to <FIG>. The second substrate <NUM> may be formed from a material that is the same as or similar to that used to form the second substrate <NUM> of <FIG>.

Referring to <FIG>, a device unit including the multilayer graphene <NUM> may be formed on the second substrate <NUM>. According to the present exemplary embodiment, a source electrode <NUM> and a drain electrode <NUM> may be formed to contact both ends of the multilayer graphene <NUM>, respectively. Then, a gate insulating layer <NUM> may be formed to cover the source electrode <NUM>, the drain electrode <NUM>, and the multilayer graphene <NUM> therebetween, and a gate electrode <NUM> may be formed on the gate insulating layer <NUM>. The gate electrode <NUM> may be disposed above or directly above the multilayer graphene <NUM>.

The device <NUM> of <FIG> may be a transistor, and the multilayer graphene <NUM> may be used as a channel layer in the transistor. The multilayer graphene <NUM> may have a pnp or npn junction structure. When the multilayer graphene <NUM> has a pnp junction structure, the source electrode <NUM> and the drain electrode <NUM> may contact different p-type regions of the multilayer graphene <NUM>, respectively. When the multilayer graphene <NUM> has an npn junction structure, the source electrode <NUM> and the drain electrode <NUM> may contact different n-type regions of the multilayer graphene <NUM>, respectively. The device <NUM> of <FIG> may be a top-gate transistor in which the gate electrode <NUM> is disposed over the multilayer graphene (in this example, a channel layer) <NUM>.

Referring to <FIG>, an underlayer <NUM> and a multilayer graphene <NUM> may be formed on a first substrate <NUM>. This structure is the same as or similar to the structure of <FIG>.

Referring to <FIG>, after a gate electrode <NUM> is formed on the second substrate <NUM> and a gate insulating layer <NUM> is formed to cover the gate electrode <NUM>, the multilayer graphene <NUM> of the first substrate <NUM> may be transferred to the gate insulating layer <NUM>. The method of transferring the multilayer graphene <NUM> may be the same as or similar to the transferring method described above with reference to <FIG>.

Referring to <FIG>, a source electrode <NUM> and a drain electrode <NUM> may be formed on the gate insulating layer <NUM> to contact both ends of the multilayer graphene <NUM>, respectively. The device <NUM> of <FIG> may be a bottom-gate transistor, and the multilayer graphene <NUM> may be a channel layer in the bottom-gate transistor. The multilayer graphene <NUM> may have a pnp or npn junction structure.

Referring to <FIG>, a plurality of underlayers <NUM> may be formed on a first substrate <NUM>, and a plurality of multilayer graphenes <NUM> may be formed on the plurality of underlayers <NUM>. Each multilayer graphene <NUM> may be a bilayer graphene having a bandgap. According to desired characteristics, the multilayer graphene <NUM> may be a multilayer graphene including three or more layers. The structure of <FIG> may be obtained using a method that is the same as or similar to that described above with reference to <FIG>.

Referring to <FIG>, the plurality of multilayer graphenes <NUM> of the first substrate <NUM> may be transferred to a second substrate <NUM>. This may be the same as or similar to the transferring method of <FIG>.

Referring to <FIG>, a device unit including the plurality of multilayer graphenes <NUM> may be formed on the second substrate <NUM>. According to the present exemplary embodiment, after a tunneling layer <NUM> is formed to fill an area between the plurality of multilayer graphenes <NUM>, a gate insulating layer <NUM> may be formed on the tunneling layer <NUM> and the plurality of multilayer graphenes <NUM>. Then, a gate electrode <NUM> may be formed on the gate insulating layer <NUM>, and a source electrode <NUM> and a drain electrode <NUM> may be electrically connected to (contact) to the multilayer graphenes <NUM>, respectively. The tunneling layer <NUM> may have a material and width that enable Fowler-Nordheim (F-N) tunneling of charge to occur. For example, the tunneling layer <NUM> may have a width of several nm to several tens of nm.

A device of <FIG> may be a field effect transistor (FET) using a tunneling effect. In this respect, the device <NUM> of <FIG> may be referred to as a sort of tunneling device.

According to an exemplary embodiment, since the interval between two multilayer graphenes <NUM> may be easily controlled up to a level of several tens of nm to several nm, a device having a structure as shown in <FIG> may be easily manufactured. Since the two multilayer graphenes <NUM> are grown on a patterned underlayer (i.e., the underlayers <NUM> of <FIG>), the edge portions of the two multilayer graphenes <NUM> may have defect-free crystal structures, and accordingly the device may have an improved performance.

Although the method of transferring a multilayer graphene from a first substrate to a second substrate and then manufacturing a graphene-containing device on the second substrate has been illustrated and described with respect to <FIG>, the graphene-containing device may be manufactured on the first substrate without a transferring operation. This case is illustrated in <FIG>.

Referring to <FIG>, an underlayer <NUM> and a multilayer graphene <NUM> may be formed on a first substrate <NUM>. This structure is the same as or similar to the structure of <FIG>. The underlayer <NUM> may be a conductive layer (e.g., a metal layer), and the multilayer graphene <NUM> may be a semiconductor layer including a pn junction. Hereinafter, the underlayer <NUM> is referred to as a first conductive layer.

Referring to <FIG>, a device unit including the multilayer graphene <NUM> may be formed on the first substrate <NUM>. The multilayer graphene <NUM> may be a bilayer graphene having a bandgap. According to desired characteristics, the multilayer graphene <NUM> may be a multilayer graphene including three or more layers. According to the present exemplary embodiment, a second conductive layer <NUM>, an insulating layer <NUM>, and a third conductive layer <NUM> may be sequentially formed on the multilayer graphene <NUM>.

The device of <FIG> may be a tunneling device. The multilayer graphene <NUM> may be a tunneling layer. The first conductive layer (i.e., the underlayer <NUM>) may be a drain electrode, the second conductive layer <NUM> may be a source electrode, and the third conductive layer <NUM> may be a gate electrode. The insulating layer <NUM> may be a gate insulating layer. The third conductive layer <NUM> may control the electrical characteristics of the multilayer graphene <NUM> or control electrical characteristics of an interface between the second conductive layer <NUM> and the multilayer graphene <NUM>. Due to the tunneling of a charge via the multilayer graphene <NUM>, current may flow between the first conductive layer (i.e., the underlayer <NUM>) and the second conductive layer <NUM>.

A multilayer graphene according to exemplary embodiments is applicable to various devices (such as semiconductor devices and electronic devices) for several purposes. For example, a multilayer graphene according to an exemplary embodiment is applicable to various devices, such as diodes, transistors, tunneling devices, memory devices, solar cells, photodetectors, sensors, light emitting devices, logic devices, energy storage devices, and display devices. The transistors may include field effect transistors (FET), thin film transistors (TFT), binary junction transistors (BJT), barrier transistors (i.e., a barristor), or the like. The sensors may be, for example, light sensors, gas sensors, or sensors using a graphene array. The multilayer graphene according to an exemplary embodiment is applicable to any device using a pn junction, and may be used instead of Si in an existing Si-using device. The multilayer graphene is applicable to, for example, a stackable device, a flexible device, or a transparent device. Since the multilayer graphene according to an exemplary embodiment may be flexible and may have transparent characteristics, the multilayer graphene is usefully and favorably applicable to flexible devices and transparent devices. A device including the multilayer graphene according to an exemplary embodiment is also applicable to various integrated circuits.

<FIG> is a scanning tunneling microscopy (STM) image showing a Ni-doped monolayer graphene formed according to the above-described exemplary embodiments. Referring to <FIG>, the graphene monoatomic layer is doped with Ni.

<FIG> is an STM image showing a Ni-doped bilayer graphene formed on a monolayer graphene layer according to the above-described exemplary embodiments.

<FIG> show chemical structures of various source gases that may be used to form a multilayer graphene in certain exemplary embodiments.

<FIG> shows the chemical structure of pyridine (C<NUM>H<NUM>N), <FIG> shows the chemical structure of benzene (C<NUM>H<NUM>), <FIG> shows the chemical structure of ethylene (C<NUM>H<NUM>), <FIG> shows the chemical structure of acetylene (C<NUM>H<NUM>), and <FIG> shows the chemical structure of triethylborane (C<NUM>H<NUM>B). Materials as shown in <FIG> may be used in the multilayer graphene forming methods described above with reference to <FIG>. However, the material (source gas) that may be used in an exemplary embodiment is not limited to those shown in <FIG>, and various other materials may be used.

Claim 1:
A method of forming a multilayer graphene, the method comprising:
forming a first graphene on an underlayer at a first temperature by using a first source gas; and
forming a first multilayer graphene on a first area of the first graphene at a second temperature by using a second source gas, the first multilayer graphene comprising a portion of the first graphene corresponding to the first area,
wherein the first temperature used to form the first graphene is different from the second temperature, or a first source gas used to form the first graphene is different from the second source gas.