Abstract:
This invention is particularly addressing a novel method to grow two dimensional carbon nanomaterials. Using our technologies, only solid state carbon sources are used as feedstock to grow this kind of carbon nanomaterials, while no hydrocarbon gases or other carbon contained gases are required as feedstock. This invention can also be applied to grow non-carbon-based two dimensional nanomaterials, with obvious advantages of reducing manufacturing cost and enhancing growth rate.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This is the Nonprovisional application for a former provisional application with the same title, submitted on Jan. 6, 2016. EFS ID: 24538619, Application No. 62/275,307 
     
    
     BACKGROUND 
       [0002]    Two dimensional (2D) carbon nano-materials (or nanomaterials) are carbon crystals in a scale of nanometers. The 2D carbon nanomaterials are made of a single to a few layers of graphene. If a carbon nanomaterial is being thickened to more than tens of nanometers, it has graphitic crystal structure. 
         [0003]    This invention is particularly addressing to free-standing two dimensional carbon nanostructures, which include but are not only limited to Fluffy Graphene, Carbon Nanosheets, Carbon Nanowalls, Carbon Nanoflakes, Vertically Free-standing Graphene, Graphene Flowers, or Petals made of Graphene. 
         [0004]    This invention can also be applied to grow non-carbon-based two dimensional nanomaterials, with obvious advantages of reducing manufacturing cost and enhancing growth rate. 
       SUMMARY OF THE INVENTION 
       [0005]    This invention teaches how to grow free-standing two-dimensional carbon nanomaterials, especially vertically free-standing graphene, via non-conventional methods. Using our technologies, no more hydrocarbon gases or other carbon contained gases are necessarily required to grow the graphene materials. 
         [0006]    Simply modifying our invented technologies, a man familiar with plasma technology can use this invention to grow other two-dimensional nanomaterials via a solid-state feedstock (a.k.a. precursor). 
         [0007]    It is well known that free-standing carbon nanomaterials can be synthesized via methods of Chemical Vapor Deposition (CVD). Feedstock precursors are introduced into a process chamber in vapor phase. To enhance growth reaction, plasma technology is usually applied. This process is called plasma enhanced CVD (PE-CVD) method. Radio-Frequency (RF) electromagnetic wave, microwave, direct current (DC), hot filaments, parallel plates can generate plasma during reaction processes. 
         [0008]    Conventional methods must use expensive and flammable gases, such as a hydrocarbon gas as feedstock. Carbon atoms are extracted from those hydrocarbon gases to grow graphene materials. Usually, hydrogen or other reductive gases are required during the process. 
         [0009]    Our novel methods only use a carbon solid as feedstock. None of carbon based feedstock gas is required. Furthermore, neither hydrogen nor other reductive gases is required during our invented processes. 
         [0010]    Choosing a solid-state feedstock has tremendous advantages over a gas feedstock. To manage gas flow and process pressure, it increases process cost and requires extra engineering hardware and labors. 
         [0011]    Carbon bulk materials in solid-state are abundant in natural resources, and is easy-to-adopt as a feedstock. Carbon atoms are extracted from the solid-state carbon bulk materials directly. 
         [0012]    The method to grow free-standing carbon nanometerials which only uses solid-state feedstock, has never been reported in academic or industry articles. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  is a schematic cross-sectional view of an apparatus, which uses a planar-coil-antenna to generate Inductive-Coupled-Plasma (ICP). The apparatus can manufacture two-dimensional carbon nanomaterials. 
           [0014]      FIG. 2  shows more possible positions, where solid-state carbon sources can be disposed in the planar-coil-antenna-incorporated apparatus, beside one position in  FIG. 1 . 
           [0015]      FIG. 3  is a schematic cross-sectional view of an apparatus, which uses a helical-coil-antenna to generate Inductive-Coupled-Plasma (ICP). The apparatus can manufacture two-dimensional carbon nanomaterials. 
           [0016]      FIG. 4  shows more possible positions, where solid-state carbon sources can be disposed in the helical-coil-antenna-incorporated apparatus, beside one position in  FIG. 3 . 
           [0017]      FIG. 5  is a schematic cross-sectional view of an apparatus, which uses a planar-plate-antenna to generate Capacitive-Coupled-Plasma (CCP). The apparatus can manufacture two-dimensional carbon nanomaterials. 
           [0018]      FIG. 6  shows more possible positions, where solid-state carbon sources can be disposed in the planar-plate-antenna-incorporated apparatus, beside one position in  FIG. 5 . 
           [0019]      FIG. 7  is a schematic cross-sectional view of an apparatus, which uses microwave field in transverse magnetic (TM) mode to generate plasma. The apparatus can manufacture two-dimensional carbon nanomaterials. 
           [0020]      FIG. 8  shows more possible positions, where solid-state carbon sources can be disposed in the TM mode microwave waveguide incorporated apparatus, beside one position in  FIG. 7 . 
           [0021]      FIG. 9  is a schematic cross-sectional view of an apparatus, which uses microwave field in transverse electric (TE) mode to generate plasma. The apparatus can manufacture two-dimensional carbon nanomaterials. 
           [0022]      FIG. 10  shows more possible positions, where solid-state carbon sources can be disposed in the TM mode microwave waveguide incorporated apparatus, beside one position in  FIG. 9 . 
           [0023]      FIG. 11  is a schematic cross-sectional view of an apparatus, which uses microwave field in transverse electromagnetic (TEM) mode to generate plasma. The apparatus can manufacture two-dimensional carbon nanomaterials. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0024]      FIG. 1  is a schematic cross-sectional view showing structure of a planar-coil ICP plasma apparatus to manufacture the two-dimensional carbon nanomaterials. With reference to  FIG. 1 , the apparatus  100  includes a vacuum chamber  101 , an exhaust port  102 , a gas inlet  103 , a shield box  104 , a RF power radiation window  105 , a substrate  111 , a holder  112 , a heater  113 , a planar-coil antenna to radiate RF power  121 , a RF power source with matching circuit  122 , and a solid-state carbon source  131 . 
         [0025]    The vacuum chamber  101  is made of metal and connected to a vacuum pump via the exhaust port  102 . The vacuum chamber  101  is electrically grounded. 
         [0026]    The gas inlet  103  supplies a non-hydrocarbon gas, such as Argon (Ar) gas, from a gas container (not shown), into the vacuum chamber  101 . 
         [0027]    The shield box  104  is made of metal and positioned on the upper side of the vacuum chamber  101 . The shield box  104  makes contact with the top plate of vacuum chamber  101  and electrically grounded. 
         [0028]    The RF power window  105  is made of RF electromagnetic wave transparent material, such as quartz glass, etc. The RF window  105  makes contact with the vacuum chamber  101  via a vacuum sealing. 
         [0029]    The holder  112  is disposed in the vacuum chamber  101 . The heater  113  is positioned in the holder  112 . The substrate  111  is disposed on top of the holder  112 . The holder  112  supports the substrate  111 . The heater  113  heats the substrate  111  to a desired temperature. 
         [0030]    The planar-coil antenna  121  to radiate RF power is positioned in the shield box  105 , and on the upper side of the RF window  105 . The planar-coil RF antenna  121  is connected the RF power source with matching circuit  122 . 
         [0031]    The RF power source with matching circuit  122  supplies a high frequency electromagnetic wave of 13.56 MHz, for example, to the planar-coil antenna  121 , and suppresses reflection of the high frequency electromagnetic wave backward from the planar antenna  121 . 
         [0032]    The solid-state carbon source  131  is positioned in the vacuum chamber  101 , and between RF window  105  and substrate  111 . 
         [0033]    In the apparatus  100 , plasma  141  is generated in the vacuum chamber  101 , and under the RF window  105 . That is, as shown in  FIG. 1 , when the RF electromagnetic wave is generated around the RF antenna  121 , electrons are accelerated by the induced electric field, and the gas in the vacuum chamber  101  is ionized. The plasma  141  is generated under the RF window, and reacts with the substrate  111 . 
         [0034]      FIG. 2  shows more possible positions of solid-state carbon sources, beside the one disposed in  FIG. 1 . The positions of solid-state carbon source can be selected from position  131 ,  132 ,  133 ,  134 ,  135 ,  136 , and a combination thereof. 
         [0035]      FIG. 3  is a schematic cross-sectional view showing structure of a helical-coil ICP plasma apparatus to manufacture the two-dimensional carbon nanomaterials. With reference to  FIG. 3 , the apparatus  200  includes a vacuum chamber  201 , a gas exhaust port  202 , inlet  203 , a shield box  204 , a tube  205 , a substrate  211 , a holder  212 , a heater  213 , a helical RF antenna  221 , a RF power source with matching circuit  222 , and a solid-state carbon source  231 . 
         [0036]    The vacuum chamber  201  is made of metal and connected to a vacuum pump via the exhaust port  202 . The vacuum chamber  201  is electrically grounded. 
         [0037]    The gas inlet  203  supplies a non-carbon gas, such as Argon (Ar) gas, from a gas container (not shown), into the vacuum chamber  201 . The gas inlet  203  makes contact with the tube  205  via a vacuum sealing. 
         [0038]    The tube  205  is made of RF electromagnetic wave transparent material, such as quartz glass, etc. The tube  205  makes contact with the vacuum chamber  201  via a vacuum sealing. 
         [0039]    The shield box  204  is made of metal and positioned on the upper side of the vacuum chamber  201 , and outside of the helical RF antenna  221 . The shield box  205  makes contact with the top plate of vacuum chamber  201  and electrically grounded. 
         [0040]    The holder  212  is placed in the vacuum chamber  201 . The heater  213  is positioned in the holder  212 . The substrate  211  is disposed on top of the holder  212 . The holder  212  supports the substrate  211 . The heater  213  heats the substrate  211  to a desired temperature. 
         [0041]    The helical RF antenna  221  is positioned in the shield box  205 , and on the outside of the tube  205 . The helical RF antenna  221  is connected to the RF power source with matching circuit  222 . 
         [0042]    The RF power source with matching circuit  222  supplies a high frequency electromagnetic wave of  13 . 56  MHz, for example, to the helical RF antenna  221 , and suppresses reflection of the high frequency electromagnetic wave back from the helical RF antenna  221 . 
         [0043]    The solid-state carbon source  231  is positioned in the tube  205 , or in the vacuum chamber  201 . 
         [0044]    In the apparatus  200 , plasma  241  is generated in the tube  205 , and transported into the vacuum chamber  201  via gas pressure. That is, as shown in  FIG. 3 , when the RF electromagnetic wave is generated around the RF antenna  221 , electrons are accelerated by the induced electric field and the gas in the tube  205  is ionized. The plasma  241  is transported into the vacuum chamber  201  via gas pressure, and can reach the substrate  211 . 
         [0045]      FIG. 4  shows more possible positions of solid-state carbon sources, beside the one disposed in  FIG. 3 . The positions of solid-state carbon source can be selected from position  231 ,  232 ,  233 ,  234 ,  235 ,  236 , and a combination thereof. 
         [0046]      FIG. 5  is a schematic cross-sectional view showing structure of a CCP plasma apparatus to manufacture the two-dimensional carbon nanomaterials. With reference to  FIG. 5 , the plasma apparatus  300  includes a vacuum chamber  301 , an exhaust port  302 , a gas inlet  303 , a substrate  311 , a holder  312 , a heater  313 , a RF electrode  321 , a RF power source with matching circuit  322 , a RF transmission line  323 , a RF connector  324 , and a solid-state carbon source  331 . 
         [0047]    The vacuum chamber  301  is made of metal and connected to a vacuum pump via the exhaust port  302 . The vacuum chamber  301  is electrically grounded. 
         [0048]    The gas inlet  303  supplies a non-carbon gas, such as Argon (Ar) gas, from a gas container (not shown), into the vacuum chamber  301 . 
         [0049]    The holder  312  is placed in the vacuum chamber  301 . The heater  313  is positioned in the holder  312 . The substrate  311  is disposed on top of the holder  312 . The holder  312  supports the substrate  311 . The heater  313  heats the substrate  311  to a desired temperature. 
         [0050]    The RF electrode  321  is positioned in the vacuum chamber  301 , and parallel to the holder  312 . The RF electrode  321  is electrically connected to the RF power source with matching circuit  322  via RF transmission line  323 . 
         [0051]    The RF connector  324  is made of insulator. The RF transmission line  323  is positioned through the RF connector  324 , and makes contact with the RF connector  324  via a vacuum sealing. The RF connector is positioned on the wall of the vacuum chamber  301 , and in contact with the vacuum chamber  301  via vacuum sealing. 
         [0052]    The RF power source with matching circuit  322  supplies a high frequency electromagnetic wave of  13 . 56  MHz, for example, to the RF electrode  321 , and suppresses reflection of the high frequency electromagnetic wave backward from the RF electrode  321 . 
         [0053]    The solid-state carbon source  331  is positioned in the vacuum chamber  301 , and around the holder  312  and planar RF electrode  321 . 
         [0054]    In the plasma apparatus  300 , plasma  341  is generated in the vacuum chamber  301 , and between the RF electrode  321  and the substrate  311 . That is, as shown in  FIG. 5 , when the RF electromagnetic wave is generated around the RF electrode  321 , electrons are accelerated by the coupled electric field, and the gas in the vacuum chamber  301  is ionized. The plasma  341  is generated between the RF electrode  321  and the substrate  311 , and can reach the substrate  311 . 
         [0055]      FIG. 6  shows more possible positions of solid-state carbon sources, beside the one disposed in  FIG. 5 . The positions of solid-state carbon source can be selected from position  331 ,  332 ,  333 ,  334 , and a combination thereof. 
         [0056]      FIG. 7  is a schematic cross-sectional view showing structure of a TM microwave plasma apparatus to manufacture the two-dimensional carbon nanomaterials. With reference to  FIG. 7 , the plasma apparatus  400  includes a vacuum chamber  401 , an exhaust port  402 , a gas inlet  403 , a microwave window  404 , a substrate  411 , a holder  412 , a heater  413 , a microwave power source  421 , a microwave waveguide  422 , a match tuner  423 , a load tuner  424 , a microwave adapter  425 , and a solid-state carbon source  431 . 
         [0057]    The vacuum chamber  401  is made of metal and connected to a vacuum pump via the exhaust port  402 . The vacuum chamber  401  is electrically connected to a ground node. 
         [0058]    The gas inlet  403  supplies a non-carbon gas, such as Argon (Ar) gas, from a gas container (not shown), into the vacuum chamber  401 . 
         [0059]    The microwave window  404  is made of microwave transparent material, such as quartz glass, etc. The microwave window  404  makes contact to the vacuum chamber  401  via a vacuum sealing. 
         [0060]    The holder  412  is placed in the vacuum chamber  401 . The heater  413  is positioned in the holder  412 . The substrate  411  is disposed on top of the holder  412 . The holder  412  supports the substrate  411 . The heater  413  heats the substrate  411  to a desired temperature. 
         [0061]    The microwave power source  421  supplies a microwave of  2 . 45  GHz, for example, to the microwave waveguide  422 . The microwave adapter  425  transmits the microwave from the microwave waveguide  422  into the vacuum chamber  401  via the microwave window  404 . In the vacuum chamber  401 , microwave field is in a TM mode. 
         [0062]    The match tuner  423  and load tuner  424  suppress reflection of the microwave backward from the microwave adapter  425 . 
         [0063]    The solid-state carbon source  431  is positioned around the substrate  411  in the vacuum chamber. 
         [0064]    In the plasma apparatus  400 , the plasma  441  is generated under the microwave window  404  in the vacuum chamber  401 . That is, as shown in  FIG. 7 , when the microwave is generated from microwave power source  421 , and transmitted via the microwave waveguide  422  and microwave adapter  425  electrons are accelerated by the TM mode microwave, and the gas in the vacuum chamber  401  is ionized. The plasma  441  is generated under the microwave window, and can reach the substrate  411 . 
         [0065]      FIG. 8  shows more possible positions of solid-state carbon sources, beside the one disposed in  FIG. 7 . The positions of solid-state carbon source can be selected from position  431 ,  432 ,  433 ,  434 ,  435 , and a combination thereof. 
         [0066]      FIG. 9  is a schematic cross-sectional view showing structure of a TE microwave plasma apparatus to manufacture the two-dimensional carbon nanomaterials. With reference to  FIG. 9 , the plasma apparatus  500  includes a vacuum chamber  501 , an exhaust port  502 , a gas inlet  503 , a microwave input window  504 , a microwave load window  505 , a substrate  511 , a holder  512 , a heater  513 , a solid-state carbon source  531 , a microwave power source  521 , a microwave input waveguide  522 , a microwave load waveguide  523 , a match tuner  524 , a load tuner  525 , and a solid-state carbon source  531 . 
         [0067]    The vacuum chamber  501  is made of metal and connected to a vacuum pump via the exhaust port  502 . The vacuum chamber  501  is electrically grounded. 
         [0068]    The gas inlet  503  supplies a non-carbon gas, such as Argon (Ar) gas, from a gas container (not shown), into the vacuum chamber  501 . 
         [0069]    The microwave input window  504  and microwave load window  505  are made of microwave transparent material, such as quartz glass, etc. The microwave input window  504  and microwave load window  505  make contact with the vacuum chamber  501  via a vacuum sealing. 
         [0070]    The holder  512  is placed in the vacuum chamber  501 . The heater  513  is positioned in the holder  512 . The substrate  511  is disposed on top of the holder  512 . The holder  512  supports the substrate  511 . The heater  513  heats the substrate  511  to a desired temperature. 
         [0071]    The microwave power source  521  supplies a microwave of  2 . 45  GHz, for example, to the microwave input waveguide  522 . The microwave input waveguide makes contact with the microwave input window  504 . The microwave input waveguide  522  transmits the microwave into the vacuum chamber  501  via the microwave input window  504 . In the vacuum chamber  501 , microwave field is in a TE mode. 
         [0072]    The microwave load waveguide  523  makes contact with the microwave load window  505 . The match tuner  524  and load tuner  525  suppress reflection of the microwave back from the vacuum chamber  501 . 
         [0073]    The solid-state carbon source  531  is positioned around the substrate  511  in the vacuum chamber  501 . 
         [0074]    In the plasma apparatus  500 , plasma  541  is generated between the microwave input window  504  and microwave load window  505  in the vacuum chamber  501 . That is, as shown in  FIG. 9 , when the microwave is generated from microwave power source  521 , and transmitted via the microwave waveguide  522  and microwave input window  504 , electrons are accelerated by the TE mode microwave, and the gas in the vacuum chamber  501  is ionized. The plasma  541  is generated between the microwave input window  504  and microwave load window  505 . The plasma  541  is transported to the surface of the substrate  511  via gas pressure. 
         [0075]      FIG. 10  shows more possible positions of solid-state carbon source, beside the one disposed in  FIG. 9 . The positions of solid-state carbon source can be selected from position  531 ,  532 ,  533 ,  534 ,  535 ,  536 , and a combination thereof. 
         [0076]      FIG. 11  is a schematic cross-sectional view showing structure of a TEM microwave plasma apparatus to manufacture the two-dimensional carbon nanomaterials. With reference to  FIG. 11 , the plasma apparatus  600  includes a vacuum chamber  601 , an exhaust port  602 , a gas inlet  603 , a microwave waveguide tube  604 , a substrate  611 , a holder  612 , a heater  613 , a microwave power source  621 , a microwave input waveguide  622 , a match tuner  623 , a microwave adapter  624 , a cylindrical antenna  625 , and a solid-state carbon source  631 . 
         [0077]    The vacuum chamber  601  is made of metal and connected to a vacuum pump via the exhaust port  602 . The vacuum chamber  601  is electrically grounded. 
         [0078]    The gas inlet  603  supplies a non-carbon gas, such as Argon (Ar) gas, from a gas container (not shown), into the vacuum chamber  601 . 
         [0079]    The microwave waveguide tube  604  is made of microwave transparent material, such as quartz glass, etc. The waveguide tube  604  is positioned in the vacuum chamber  601  and makes contact with the vacuum chamber  601  via a vacuum sealing. 
         [0080]    The holder  612  is placed in the vacuum chamber  601 . The heater  613  is positioned in the holder  612 . The substrate  611  is disposed on top of the holder  612 . The holder  612  supports the substrate  611 . The heater  613  heats the substrate  611  to a desired temperature. 
         [0081]    The microwave power source  621  supplies a microwave of  2 . 45  GHz, for example, to the microwave input waveguide  622 . The microwave adapter  624  transmits microwave from the microwave input waveguide  622  to the cylindrical antenna  625 . The cylindrical antenna  625  radiates microwave to the vacuum chamber  601  via the waveguide tube  604 . In the vacuum chamber  601 , microwave field is in a TEM mode. 
         [0082]    The match tuner  623  suppresses reflection of the microwave backward from the vacuum chamber  601 . 
         [0083]    The solid-state carbon source  631  is positioned in the vacuum chamber  601 , and face to the substrate  611 . 
         [0084]    In the plasma apparatus  600 , plasma  641  is generated around the microwave waveguide tube  604  in the vacuum chamber  601 . That is, as shown in  FIG. 10 , when the microwave is generated around the cylindrical antenna  625 , electrons are accelerated by the TEM mode microwave, and the gas in the vacuum chamber  601  is ionized. The plasma  641  is generated around the microwave tube  604  and can reach the substrate  611  and solid-state carbon source  631 .