Patent Description:
The computer industry aims at a continuous miniaturization of devices to reduce the energy required for storing or switching a piece of information such as a logical bit. For this purpose, the existing computing circuits employ the standard binary logic for storage and processing information. These circuits are reaching their fundamental limitations set by the atomic size miniaturization and by the fundamental Landauer principle of energy dissipation per bit processing.

<NPL>, discloses a conventional ferroelectric memory.

<CIT> discloses a variable-capacitance electrical capacitor with a state-change material providing a conductive and a non-conductive state.

In view of the technical problems laid out above, there is a need for a multi-value logic device. In the context of this disclosure, the term multi-value logic device may refer to a device that provides at least three states, such as at least three switchable and/or individually addressable logic states or at least three switchable and/or individually addressable polarization states. In other words, the multi-value logic device may be considered a non-binary logic device. The multi-value logic device is therefore distinct from a binary logic device, which provides two states (i. e, two logic states or polarization states, which are switchable and/or individually addressable).

Employing a multi-value logic device may reduce energy losses and permit an unprecedentedly high information density of the device, and thus overcome the binary tyranny of conventional devices. Exploring the multi-value logics is crucial for realizing non-von Neumann computing. Despite an active search for systems capable to realize switchable multi-value logics, a practically viable physical implementation of a multi-value logic device has previously remained an unresolved daunting task.

Existing implementations of pseudo-multi-level logic units, that are currently used in solid-state drives and flash memories, actually comprise a combination of individual binary (i. , bit) logic devices. Therefore, they require the analogue methods of bit writing, which may lead to erratic behavior of the logic cells due to stochastic loss of information.

The present disclosure relates to a ferroelectric nanoparticle capacitor-device according to independent claim <NUM>, a use of a ferroelectric nanoparticle capacitor-device according to independent claim <NUM>, and to a method for operating a ferroelectric nanoparticle capacitor-device according to independent claim <NUM>. The dependent claims relate to preferred embodiments.

In a first aspect of the present disclosure, a ferroelectric nanoparticle capacitor-device comprises a pair of conductive elements electrically insulated from each other, and ferroelectric nanoparticles arranged between the conductive elements of the pair. The ferroelectric nanoparticles are adapted to provide at least three polarization states with different total ferroelectric polarizations.

The ferroelectric nanoparticle capacitor-device according to the first aspect therefore provides a multi-value logic device, or an implementation of a multi-value logic, respectively.

The ferroelectric nanoparticle capacitor-device is adapted to selectively set the ferroelectric nanoparticles to any of the at least three polarization states. For example, the ferroelectric nanoparticle capacitor-device may be adapted to receive a preselected voltage or a preselected charge at one of the conductive elements of the pair to selectively set the ferroelectric nanoparticles to any of the at least three polarization states, in particular wherein the other conductive element of the pair is adapted to carry a constant electrical charge. In other words, the polarization states of the ferroelectric nanoparticles can be individually addressed. Addressing a polarization state refers to setting the ferroelectric nanoparticles to the respective polarization state.

The ferroelectric nanoparticle capacitor-device therefore constitutes a multi-value logic device, where each polarization state serves as a state (e. , as a memory level) of the multi-value logic, and the switching by the application of the charge represents the transition between the states, or between the memory levels, respectively.

The ferroelectric nanoparticles may be adapted to provide at most <NUM> discrete polarization states with different total ferroelectric polarizations, in particular at most <NUM> discrete polarization states with different total ferroelectric polarizations, in particular at most <NUM> discrete polarization states with different total ferroelectric polarizations, in particular at most <NUM> discrete polarization states with different total ferroelectric polarizations, in particular at most <NUM> discrete polarization states with different total ferroelectric polarizations.

To individually address any of the polarization states, or switch between any pair of polarization states, the ferroelectric nanoparticle capacitor-device may provide a respective route, wherein the route is well-defined and specific to the polarization state to be addressed, or to the pair of polarization states to be switched between, respectively. In the context of this disclosure, the term route may refer to a charge to be applied to at least one of the conductive elements, or to charges (i. , different, such as by total value and/or sign) to be sequentially applied to the at least one of the conductive elements.

The at least three polarization states may be at least three remanent polarization states. In other words, the ferroelectric nanoparticles may be adapted to preserve any of the at least three polarization states and/or to preserve the set one of the at least three polarization states, in particular when no charge or voltage is applied to the conductive elements.

This allows one to implement memory levels of a multi-value logic.

The polarization states refer to overall polarization states of the ferroelectric nanoparticles, or, in other words, to polarization states of the entirety of the ferroelectric nanoparticles; for example, in contrast to an individual polarization state of an individual ferroelectric nanoparticle of the ferroelectric nanoparticles.

The polarization state(s) refer(s) to ferroelectric polarization state(s).

The polarization states are discrete polarization states. For example, the at least three polarization states may be at least three discrete polarization states.

The ferroelectric nanoparticles are adapted to provide respective individual polarization states, in particular discrete individual polarization states such as a respective individual polarized-up and a respective individual polarized-down state.

The individual polarization state(s) refer(s) to individual ferroelectric polarization state(s).

The ferroelectric nanoparticle capacitor-device may be adapted to switch an individual polarization state of an individual ferroelectric nanoparticle of the ferroelectric nanoparticles. The ferroelectric nanoparticle capacitor-device may be adapted to preserve the individual polarization states of the remaining ferroelectric nanoparticles while switching the individual polarization state of the individual ferroelectric nanoparticle.

The ferroelectric nanoparticles may have an identical material composition.

This may facilitate an economic fabrication of the device.

The conductive elements may refer to electrically conductive elements.

The conductive elements may be conductive layers and/or conductive plates.

A (in particular, each) ferroelectric nanoparticle of the ferroelectric nanoparticles may be arranged between first sections of the conductive elements. In other words, the first sections of the conductive elements may correspond to projections of the ferroelectric nanoparticle onto the conductive elements. The ferroelectric nanoparticle (or the ferroelectric nanoparticles, respectively) and the (respective) first sections of the conductive elements may define a ferroelectric capacitor (or ferroelectric capacitors, respectively).

At most <NUM> ferroelectric nanoparticles may be arranged between the conductive elements of the pair, or at most <NUM> ferroelectric nanoparticles, or at most <NUM> ferroelectric nanoparticles, or exactly <NUM> ferroelectric nanoparticles, or exactly <NUM> ferroelectric nanoparticles.

Respective limited numbers of nanoparticles may improve the reliability of the switching between the polarization states.

Sections of the conductive elements sandwiching one of the ferroelectric nanoparticles may define a respective ferroelectric capacitor. In other words, the ferroelectric nanoparticles and the sections of the conductive elements sandwiching the ferroelectric nanoparticles may define ferroelectric capacitors.

The conductive elements of the pair may comprise respective surfaces facing each other, and respective surface areas of the respective surfaces may each exceed an overall surface-projected area of the ferroelectric nanoparticles.

In other words, the conductive elements may comprise respective excess portions without a ferroelectric nanoparticle in between them.

In corresponding embodiments, the surface areas of the conductive elements exceeding the overall surface projected area of the ferroelectric nanoparticles (or sections of the respective surfaces without a ferroelectric nanoparticle in between them, respectively; or the excess portions of the conductive elements, respectively) may define a dielectric capacitor or a capacitance of a dielectric capacitor. The dielectric capacitor may be adapted to provide the dielectric capacitance. Sections of the respective surfaces without a ferroelectric nanoparticle in between them may refer to sections of the respective surfaces, wherein the ferroelectric nanoparticles fill less than <NUM>%, in particular less than <NUM>%, in particular less than <NUM>%, in particular less than <NUM>%, or in particular less than <NUM>% of the distance between the respective surfaces.

The dielectric capacitor may be arranged electrically in parallel and/or in series to the ferroelectric capacitors. The dielectric capacitor and the ferroelectric capacitors, (or the capacitance of the dielectric capacitor and the capacitance of the ferroelectric capacitors, respectively) may be adapted to together define the routes between the at least three polarization states and/or to define a number of remanent polarization states.

The overall surface-projected area of the ferroelectric nanoparticles may correspond to an area of a projection of the ferroelectric nanoparticles onto one of the respective surfaces.

The respective surfaces of the conductive elements of the pair may each be continuous, e. with a round or elliptical or rectangular or polygonal or rounded polygonal shape.

The ferroelectric nanoparticles are arranged between the respective surfaces.

The respective surfaces may comprise and/or define lateral directions parallel to the respective surfaces. In other words, the respective surfaces may extend laterally.

Each of the respective surface areas may exceed an overall surface-projected area of the ferroelectric nanoparticles by at least <NUM>% or by at least <NUM>% or by at least <NUM>% or by at least <NUM>% or by at least a factor of two.

The ferroelectric nanoparticles may be spaced apart from each other and/or a dielectric separator material may be arranged between the ferroelectric nanoparticles.

Corresponding embodiments may ensure discrete polarization states and/or discrete individual polarization states.

In corresponding embodiments, the dielectric separator material may be comprised in the dielectric capacitor and/or provide a dielectric of the dielectric capacitor.

At least a section of the dielectric separator material may be arranged between second sections of the conductive elements. In other words, the second sections of the conductive elements may correspond to projections of the at least section of the dielectric separator material onto the conductive elements. The at least section of the dielectric separator material and the second sections of the conductive elements may (i. , according to an alternative definition) define the dielectric capacitor.

The dielectric separator material may be adapted to separate the conductive elements and/or to electrically insulate the conductive elements from each other.

The dielectric separator material may encircle at least one of the ferroelectric nanoparticles or encircle the ferroelectric nanoparticles, in particular laterally (i. , along the lateral directions).

The conductive elements of the pair may comprise respective surfaces. The respective surfaces may be spaced apart by a distance. The ferroelectric nanoparticles may extend along at least <NUM>% of the distance, or along at least <NUM>% of the distance, or along at least <NUM>% of the distance, or along the entire distance. Alternatively, or in addition, the respective surfaces may be connected by a reference line, and the ferroelectric nanoparticles may extend along the reference line. The distance may correspond to a length of the reference line.

The ferroelectric nanoparticles may be spaced apart from each other laterally (i. , along the lateral directions).

A first ferroelectric nanoparticle of the ferroelectric nanoparticles may have a first size. A second ferroelectric nanoparticle of the ferroelectric nanoparticles may have a second size. The first size may be larger than the second size, in particular by at least <NUM>% or by at least <NUM>% or by at least <NUM>% or by at least a factor of two.

The first size (or the second size, respectively) may refer to the maximum extension of the first ferroelectric nanoparticle (or of the second ferroelectric nanoparticle, respectively). In other words, the first size (or the second size, respectively) may refer to a size of the first ferroelectric nanoparticle (or of the second ferroelectric nanoparticle, respectively) along a direction, along which it is the largest.

Alternatively, the first size (or the second size, respectively) may refer to the volume of the first ferroelectric nanoparticle (or of the second ferroelectric nanoparticle, respectively).

The first (and/or second) ferroelectric nanoparticle may be arranged between first (and/or second) first sections of the conductive elements. In other words, the first (and/or second) first sections of the conductive elements may correspond to projections of the first (and/or second) ferroelectric nanoparticle onto the conductive elements. The first (and/or second) ferroelectric nanoparticle and the first (and/or second) first sections of the conductive elements may define a first (and/or a second) ferroelectric capacitor. The first (and/or second) ferroelectric capacitor may be adapted to provide a respective capacitance.

According to embodiments, respective sizes of the ferroelectric nanoparticles along any direction do not exceed <NUM>, in particular not exceed <NUM> or not exceed <NUM> or not exceed <NUM> or not exceed <NUM> or not exceed <NUM>. In the context of this disclosure, ferroelectric nanoparticles with sizes of up to <NUM> may also be referred to as ferroelectric nanodots.

Respective sizes of the ferroelectric nanoparticles may be beneficial for ensuring the monodomain ferroelectric states of the ferroelectric nanoparticles. In particular, defining the sizes of the ferroelectric nanoparticles may result in controlled coercive fields of the respective nanoparticles, and controlling the sizes thus gives control over the routes for addressing or switching between the polarization states. This is an advantage, for example, of using ferroelectric nanoparticles over using ferroelectric films in which ferroelectric domains form randomly, without good control over their size distribution. For the ferroelectric nanoparticles, narrow size tolerances or narrow size distributions may be achieved.

The respective sizes may correspond to the maximum extension or to the sizes of the ferroelectric nanoparticles along the direction, along which they are the largest, as described above in the context of the first size and the second size.

Respective minimum sizes of the ferroelectric nanoparticles along any direction may not be smaller than <NUM> or not be smaller than <NUM> or not be smaller than <NUM> or not be smaller than <NUM>.

The ferroelectric nanoparticles may comprise respective monodomain ferroelectric states. The at least three polarization states may correspond to combinations of the respective monodomain ferroelectric states of the ferroelectric nanoparticles.

The respective monodomain ferroelectric states of the ferroelectric nanoparticles may be remanent and/or discrete polarization states.

A first conductive element of the pair is electrically floating.

The ferroelectric nanoparticle capacitor-device further comprises a charge control device adapted to change a charge on a second conductive element of the pair.

The ferroelectric nanoparticle capacitor-device may further comprise a transistor, wherein a channel of the transistor forms the first conductive element or the second conductive element.

The charge control device comprises an additional conductive element electrically insulated from the pair of conductive elements. The charge control device is adapted to apply a voltage between the additional conductive element and the second conductive element.

The additional conductive element and the second conductive element may be arranged on opposite sides of the first conductive element.

The additional conductive element may be separated from the first conductive element by a dielectric spacer.

The dielectric spacer may form a gate dielectric of the transistor.

The conductive elements and/or the additional conductive element may comprise or be composed of metal material or semiconductor material.

The at least three polarization states may be associated with respective voltage levels.

The respective voltage levels may refer to voltage levels of the first conductive element and/or of the second conductive element, or to a voltage difference between the first conductive element and the second conductive element.

The ferroelectric nanoparticle capacitor-device may further comprise a voltage readout element adapted to determine a voltage of the first conductive element and/ or a voltage of the second conductive element, or a voltage difference between the first conductive element and second conductive element, such as to identify the respective voltage levels associated with the at least three polarization states.

The ferroelectric nanoparticle capacitor-device may further comprise a temperature-control element adapted to control and/or change a temperature of the ferroelectric nanoparticles. Alternatively, or in addition, the ferroelectric nanoparticle capacitor-device may comprise a force control element adapted to control and/or change a mechanical force applied to the ferroelectric nanoparticles.

The temperature-control element and/or the force control element may allow for a post-adjustment of the routes for addressing and/or switching the polarization states. For example, the temperature-control element and/or the force control element may allow for addressing a polarization state, such as a polarization state with a net polarization of zero, which may not be addressable by applying a charge or voltage to at least one of the conductive elements, e. at ambient temperature or without a force applied by force control element.

A second aspect relates to the use of the ferroelectric nanoparticle capacitor-device described above as a multi-logical-level data-storage device.

A third aspect relates to a method for operating a ferroelectric nanoparticle capacitor-device. The ferroelectric nanoparticle capacitor-device comprises a pair of conductive elements electrically insulated from each other, and ferroelectric nanoparticles arranged between the conductive elements of the pair. The ferroelectric nanoparticles are adapted to provide at least three polarization states with different total ferroelectric polarizations, comprising a minimum-ferroelectric-polarization state, a maximum-ferroelectric-polarization state, and at least one intermediate-ferroelectric-polarization state. The method comprises selecting an intermediate-ferroelectric-polarization state; selecting a first voltage or charge according to the selected intermediate-ferroelectric-polarization state; applying the first voltage or charge to a conductive element of the pair to set the ferroelectric nanoparticles to the selected intermediate-ferroelectric-polarization ; and keeping the other conductive element of the pair at a constant electrical charge.

The method may implement a multi-value logic.

The method further comprises keeping the other conductive element of the pair (i. , the first conductive element) at a constant electrical charge.

Preferably, the first voltage or charge refers to a charge. In other words, the method may refer to selecting a first charge according to the selected intermediate-ferroelectric-polarization state; and applying the first charge.

The selecting the intermediate-ferroelectric-polarization state may refer to selecting an intermediate-ferroelectric-polarization state of the at least one intermediate-ferroelectric-polarization state.

The maximum-ferroelectric-polarization state may provide a maximum ferroelectric polarization of the at least three polarization states. In other words, no polarization state of the at least three polarization states may have a ferroelectric polarization larger than the maximum-ferroelectric-polarization state.

The minimum-ferroelectric-polarization state may provide a minimum ferroelectric polarization of the at least three polarization states. In other words, no polarization state of the at least three polarization states may have a ferroelectric polarization smaller than the maximum-ferroelectric-polarization state.

A ferroelectric polarization of the intermediate-ferroelectric-polarization state may be larger than the minimum ferroelectric polarization and smaller than the maximum ferroelectric polarization.

In the context of this disclosure, a magnitude of a ferroelectric polarization may be determined by a component of the respective ferroelectric polarization along a reference axis. In other words, a negative (e. , with respect to a reference axis) ferroelectric polarization may be considered smaller than a ferroelectric polarization of zero. The reference axis may intersect the conductive elements and at least one of the ferroelectric nanoparticles.

The conductive element of the pair that the first voltage or charge is applied to may correspond to the second conductive element of the pair described above in the context of the ferroelectric nanoparticle capacitor-device. The other conductive element of the method may correspond to the first conductive element of the pair described above in the context of the ferroelectric nanoparticle capacitor-device.

The ferroelectric nanoparticle capacitor-device further comprises an additional conductive element electrically insulated from the pair of conductive elements. The applying the first voltage or charge to the conductive element of the pair (i. , to the second conductive element) comprises applying a voltage between the additional conductive element and the conductive element of the pair (i. , the second conductive element). The additional conductive element is comprised in a charge control device of the ferroelectric nanoparticle capacitor-device.

The method may further comprise, prior to applying the first voltage or charge to set the ferroelectric nanoparticles to the selected intermediate-ferroelectric-polarization state: Providing the ferroelectric nanoparticles in a first polarization state of the at least three polarization states; selecting a second voltage or charge according to the selected intermediate-ferroelectric-polarization state and/or according to the first polarization state; and applying the second voltage or charge to the conductive element of the pair to set the ferroelectric nanoparticles from the first polarization state to a second polarization state of the at least three polarization states. The first polarization state may be different from the selected intermediate-ferroelectric-polarization state. The second polarization state may be different from both the first polarization state and the selected intermediate-ferroelectric-polarization state.

In terms of their respective absolute values, the second voltage or charge may exceed the first voltage or charge.

A sign of the second voltage or charge may be opposite to a sign of the first voltage or charge. The method may further comprise, prior to applying the second voltage or charge to set the ferroelectric nanoparticles to the selected intermediate-ferroelectric-polarization state: Providing the ferroelectric nanoparticles in a third polarization state of the at least three polarization states; selecting a third voltage or charge according to the selected intermediate-ferroelectric-polarization state and/or according to the first polarization state; and applying the third voltage or charge to the conductive element of the pair to set the ferroelectric nanoparticles from the first polarization state to a third polarization state of the at least three polarization states. The third polarization state may be different from the first polarization state, the second polarization state, and from the selected intermediate-ferroelectric-polarization state.

In terms of their respective absolute values, the third voltage or charge may exceed the second voltage or charge.

A sign of the third voltage or charge may be opposite to a sign of the second voltage or charge. The selected intermediate-ferroelectric-polarization state may be a remanent state. Alternatively, or in addition, the method may comprise reducing the voltage or charge applied to the conductive element, and thereby preserving the set intermediate-ferroelectric-polarization state; in particular reducing the voltage by at least <NUM>%, by at least a factor of <NUM>, by at least a factor of <NUM>, by at least a factor of <NUM>, by at least a factor of <NUM>, or by at least a factor of <NUM>.

The method may further comprise heating the ferroelectric nanoparticles and/or applying a mechanical force to the ferroelectric nanoparticles, such as to change their polarization state and/or to modify a relationship between the selected intermediate-ferroelectric-polarization state and the applied voltage or charge.

The method may comprise heating the ferroelectric nanoparticles to change their polarization state to a polarization state with a ferroelectric polarization of zero.

The method may further comprise detecting a current polarization state of the ferroelectric nanoparticles based on a voltage of at least one of the conductive elements.

The method may comprise detecting the current polarization state of the ferroelectric nanoparticles based on a change of the voltage of at least one of the conductive elements, such as by counting jumps of the voltage of at least one of the conductive elements.

The first polarization state and/or the second polarization state may be a remanent state.

The techniques of the present disclosure and the advantages associated therewith will be best apparent from a description of exemplary embodiments in accordance with the accompanying drawings, in which:.

<FIG> is a schematic illustration of a ferroelectric nanoparticle capacitor-device <NUM> according to a first embodiment.

The ferroelectric nanoparticle capacitor-device <NUM> comprises two conductive elements <NUM>, <NUM> in the form of conductive layers <NUM>, <NUM>, and ferroelectric nanoparticles 104a, 104b between them.

The conductive layers <NUM>, <NUM>, or their respective surfaces <NUM>, <NUM>, respectively, each extend along the horizontal, lateral directions x, y, and are thus parallel to each other along those directions x, y.

Along the perpendicular, vertical direction z the conductive layers <NUM>, <NUM> or their respective surfaces <NUM>, <NUM>, respectively, are spaced apart from each other by a distance d of <NUM> to <NUM>.

The conductive layers comprise a noble metal (such as Cu or Au) as well as tantalum and/or titanium or its respective nitride and/or may comprise other metallic or semiconducting materials.

The ferroelectric nanoparticles 104a, 104b are composed of respective ferroelectric materials. In the depicted embodiments, the ferroelectric nanoparticles 104a, 104b are composed of the same ferroelectric material.

The ferroelectric material is a material characterized by the nonlinear dependence of its polarization on the electric field, P = ±Ps + ε<NUM>εfE, where ±Ps is the spontaneous polarization, directed parallel or antiparallel to the electric field E respectively, ε<NUM> is the vacuum permittivity, and εf is the dielectric constant of the ferroelectric material. The switching between the different directions of spontaneous polarization in ferroelectric material occurs at the coercive electric field Ec. For the sake of brevity, the coercive electric field is also referred to as the coercive field.

The ferroelectric material of the ferroelectric nanoparticles comprises Pb(Zr,Ti)O<NUM>, PbTiO<NUM>, or other ferroelectric oxides, HfO<NUM>, in particular doped HfO2, comprising, e.g., zirconium, BaTiO<NUM>, Ba(Sr,Ti)O<NUM>, or other ferroelectric oxides, P(VDF-TrFE. Alternatively, or in addition, it comprises a hyperferroelectric material, LiZnAs, LiBeSb, NaZnSb, LiBeBi. In the hyperferroelectric materials, the coercive field can achieve values substantially larger than the depolarization electric field, which enable an easy selection of the desirable relative strengths of Qc and Qs, for example, while temperature and strain are controlled to tune the system.

Each of the ferroelectric nanoparticles 104a, 104b is sufficiently small to support a monodomain ferroelectric state. For this purpose, the ferroelectric nanoparticles 104a, 104b are formed with their maximum extensions (namely, bulk diagonals) no larger than <NUM>, <NUM>, <NUM>, <NUM> or <NUM>, depending on the ferroelectric material of the ferroelectric nanoparticles 104a, 104b. Typical sizes of the ferroelectric nanoparticles 104a, 104b are <NUM>, <NUM>, <NUM>, <NUM>, or <NUM>.

The depicted ferroelectric nanoparticles 104a, 104b are in one of three possible ferroelectric polarization states <NUM>, in the following also referred to as polarization states <NUM> for the sake of brevity.

The polarization state <NUM> refers to the overall polarization state <NUM> of the ferroelectric nanoparticles 104a, 104b, i. to the combination of the individual (i. , ferroelectric) polarization states of the ferroelectric nanoparticles 104a, 104b.

More specifically, the polarization state <NUM> refers to the projection of the total (net, overall) polarization of the total (i. , ferroelectric) polarization of the ferroelectric nanoparticles 104a, 104b onto the axis z. In other words, the polarization state <NUM> refers to the z-component of the total polarization.

Correspondingly, the individual polarization states refer to the projections of the individual polarizations of the ferroelectric nanoparticles 104a, 104b onto the axis z.

The depicted polarization state <NUM> is characterized by antiparallel individual polarization states of the ferroelectric nanoparticles 104a, 104b, with the individual polarization of the ferroelectric nanoparticle 104a along (i. , parallel to) the axis z, and the individual polarization of the ferroelectric nanoparticle 104b antiparallel to the axis z. The same polarization state, i. with a same z-component of the total polarization, is realized when the individual polarization of the ferroelectric nanoparticle 104b is along the axis z, and the individual polarization of the ferroelectric nanoparticle 104a is antiparallel to the axis z. In the depicted embodiment, these two configurations are equivalent as the ferroelectric nanoparticles 104a are equivalent, i. with the same individual polarizations. The two configurations therefore establish a first one of the polarization states <NUM>.

A second polarization state <NUM> is realized when the individual polarizations of the ferroelectric nanoparticles 104a, 104b are both along the axis z.

A third polarization state <NUM> is realized when the individual polarizations of the ferroelectric nanoparticles 104a, 104b are both antiparallel to the axis z.

The ferroelectric nanoparticle 104a is sandwiched between the first first sections 110a, 120a of the conductive layers <NUM>, <NUM>. Vice versa, the first first sections 110a, 120a of the conductive layers <NUM>, <NUM>, or of their corresponding surfaces, respectively, correspond to projections of the ferroelectric nanoparticle 104a onto the conductive layers <NUM>, <NUM>.

The first first sections 110a, 120a of the conductive layers <NUM>, <NUM> and the ferroelectric nanoparticle 104a form a first ferroelectric capacitor <NUM>.

Correspondingly, second first sections 110b, 120b of the conductive layers <NUM>, <NUM> are associated with the ferroelectric nanoparticle 104b. The second first sections 110b, 120b of the conductive layers <NUM>, <NUM> and the ferroelectric nanoparticle 104b form a second ferroelectric capacitor <NUM>.

The first sections 110a, 110b of the first conductive layer <NUM> have a total area <NUM> which corresponds to the projection of the ferroelectric nanoparticles 104a, 104b onto the first conductive layer <NUM>, or onto its surface <NUM>, respectively. In the context of this disclosure, this area <NUM> is referred to as the overall surface-projected area of the ferroelectric nanoparticles 104a, 104b.

The overall surface-projected area <NUM>, <NUM> of the ferroelectric nanoparticles 104a, 104b is alternatively defined by the projection <NUM> of the ferroelectric nanoparticles 104a, 104b onto the second conductive layer <NUM>. Alternatively, the surface-projected area <NUM>, <NUM> of the ferroelectric nanoparticles 104a, 104b is defined by the sum of the areas of the ferroelectric capacitors <NUM>, <NUM> defined by the ferroelectric nanoparticles 104a, 104b.

The area of each of the conductive layers <NUM>, <NUM> exceeds the overall surface-projected area <NUM>, <NUM> of the ferroelectric nanoparticles 104a, 104b. Consequently, excess portions <NUM>', <NUM>' of the conductive layers <NUM>, <NUM> extend beyond the first sections 110a, 110b, 120a, 110b.

These excess portions <NUM>', <NUM>' form a dielectric capacitor <NUM>, i. a capacitor with linear charge-voltage characteristics or without a (significant) hysteresis.

In the depicted embodiment, the dielectric capacitor <NUM> comprises a dielectric material <NUM> arranged between second portions <NUM>', <NUM>' of the conductive layers <NUM>, <NUM>. In the depicted embodiment, the dielectric material <NUM> fills the entire space between the excess portions <NUM>', <NUM>' of the conductive layers <NUM>, <NUM>, such that the second portions <NUM>', <NUM>' are identical to the excess portion <NUM>', <NUM>' of the conductive layers <NUM>, <NUM>.

The dielectric material <NUM> is characterized by a linear dependence of its polarization on an applied electric field, P = ε<NUM>εdE, where εd is the dielectric constant of the dielectric material <NUM>. According to embodiments, the dielectric material comprises a high-κ dielectric such as Al<NUM>O<NUM>, Li<NUM>O, HfSiO<NUM>, Sc<NUM>O<NUM>, SrO, ZrO<NUM>, Y<NUM>O<NUM>, BaO, Ta<NUM>O<NUM>, BaO, WO<NUM>, MoO<NUM>, TiO<NUM>, SrTiO<NUM>, DyScO<NUM>. A dielectric material <NUM> may also comprise a low-κ dielectric such as SiO2 or an organic dielectric. In alternative embodiments, the dielectric material <NUM> is implemented as an air gap, which may be filled with a substitutional gas or vacuum.

In the depicted embodiment, the dielectric material <NUM> serves as a dielectric separator material <NUM> to separate the ferroelectric nanoparticles 104a, 104b from one another. For this purpose, the dielectric material <NUM> is arranged between the ferroelectric nanoparticles 104a, 104b and encircles the ferroelectric nanoparticles 104a, 104b individually in the horizontal/lateral plane x, y.

The ferroelectric nanoparticle capacitor-device <NUM> is manufactured using existing nano-manufacturing procedures, in particular nano-manufacturing procedures developed in the context of semiconductor industries. These procedures allow to fabricate complex designs with precision and reliability. For example, advances in fabrications enable the creation of three-dimensional design of the ferroelectric nanoparticle capacitor-device <NUM> on a suitable substrate support. An exemplary single crystal semiconducting substrate of a selected type doping, or conductivity, respectively (for example, n-conductivity) is available commercially from various sources. A proper geometric design is achieved by the appropriate lithography and etching techniques, for example, electron beam lithography and ion etching. The conductive elements <NUM>, <NUM> are created by CVD and PVD methods and/or other suitable processes. After deposition of a first conductive element <NUM>, <NUM>, a ferroelectric layer is disposed, thereover, using, for example, an ALD approach and/or other suitable processes. The constitutive ferroelectric nanoparticles 104a, 104b are structured individually or together from the ferroelectric layer, e. in a single structuring step. In the former case, the geometric configuration at each stage is designed using appropriate lithography techniques, for example, extreme ultraviolet or electron beam lithography. The dielectric material <NUM> is optionally grown over the first conductive element <NUM>, <NUM> by the, for example, ALD technique. A second conductive element <NUM>, <NUM> is deposited. Optional interconnecting structures are formed on or in the substrate to form gate, source and drain wire connection, for example by CVD and PVD methods. The patterning and architecture of the device <NUM> is to be implemented by the, for example, Cadence Allegro software package and/or other suitable packages.

To illustrate the working mechanism of the ferroelectric nanoparticle capacitor-device <NUM>, <FIG>, <FIG> refer to the situation of a single ferroelectric nanoparticle 104a between conductive elements <NUM>, <NUM>, with a charge control device <NUM> electrically connected 114a to one of the conductive elements <NUM>, <NUM>.

As shown in <FIG>, the ferroelectric nanoparticle 104a is uniformly polarized and is confined between the two conductive elements <NUM>, <NUM> carrying the electric charge <NUM>. It can stay in either of two individual (ferroelectric) polarization states 106a: a state (+<NUM>), having the polarization directed "up" along the z-axis, and a state (-<NUM>) having the polarization directed "down". The single ferroelectric nanoparticle 104a between conductive elements <NUM>, <NUM> thus implements two corresponding logical levels, |+<NUM>) and |-<NUM>).

Consequently, the individual polarization state 106a may be controlled by the charge applied to the conductive elements <NUM>, <NUM>. The single ferroelectric nanoparticle 104a of <FIG>, confined between the conductive elements <NUM>, <NUM>, therefore implements a binary (i. , two-level) logic device with the logical levels |+<NUM>) and |-<NUM>).

Here, and in the following, a charge control device <NUM> with an electrical connection 114a to at least one of the conductive elements <NUM>, <NUM> is used to control the charge of the respective conductive element(s) <NUM>, <NUM> and thus the individual polarization state 106a of the ferroelectric nanoparticle 104a or the polarization state <NUM> of <FIG>. This approach is distinct from conventional techniques, which control the voltages at conductive elements. Advantageously, through the charge control and the charge control device <NUM>, the nanoparticle 104a or the nanoparticles 104a, 104b of <FIG> and their respective polarization states 106a, <NUM> are addressed much more reliably than in conventional techniques based on the voltage control.

Importantly, the effective electric field, E, operating the polarization of the ferroelectric nanoparticle 104a includes not only the field induced by the charge <NUM> on the conductive plates, but also by the depolarization field, induced by the bound charge, Qs = SPs, emerging at the polarization field lines' termination points located at the interface between the ferroelectric nanoparticle 104a and the conductive elements <NUM>, <NUM>. Herein, Ps refers to the spontaneous polarization of the ferroelectric nanoparticle associated with the polarization state 106a. The voltage-charge relation for the single ferroelectric nanoparticle capacitor is given by Cf V = Q ± Qs, where V is the voltage and Cf= ε<NUM>εfS/d is the capacitance of the ferroelectric material and the sign ± corresponds to the "up" (+<NUM>) or "down" (-<NUM>) orientation of the polarization 106a.

<FIG> exemplifies the electrostatic energies, W± = (Q ± Qs)<NUM>/<NUM>Cf corresponding to the (+<NUM>) and (-<NUM>) polarization states 106a of <FIG>, as functions of the applied charge Q. They are shifted over ±Qs with respect to Q = <NUM>, and the minima correspond to situations where the charge on the conductive elements <NUM>, <NUM> precisely compensates the bound charge resulting in the zero internal field. The terminal points N<NUM> (corresponding to the critical charges Q<NUM>,<NUM>) of parabolas correspond to the situation where a polarization states 106a with a given polarization direction becomes unstable with respect to switching to the polarization states 106a with the opposite polarization direction. The critical charges N<NUM> corresponding to the switching (-<NUM>) → (+<NUM>) and (+<NUM>)→ (-<NUM>) are given by Q<NUM>,<NUM> = ±(Qs- Qc) respectively, where Qc = CfEcd. This energy profile results in the charge-voltage two-branch switching hysteresis loop V(Q) with upper and lower branches <MAT> corresponding to the polarization states 106a, or logical levels |+<NUM>) and |-<NUM>), respectively.

<FIG> shows an effective electric circuit of the ferroelectric nanoparticle capacitor-device <NUM> of <FIG>. The ferroelectric nanoparticle capacitor-device <NUM> includes the two ferroelectric capacitors <NUM>, <NUM>, each with a capacitance Cf. It further comprises a dielectric capacitor <NUM> with a capacitance Cd, connected in parallel to the ferroelectric capacitors <NUM>, <NUM>.

The effective electric circuit further comprises a charge-control element <NUM> in electrical contact 114a with at least one of the conductive elements <NUM>, <NUM>. The charge-control element <NUM> is adapted to apply a charge Q to the conductive element(s) <NUM>, <NUM> it is connected to.

Importantly, the charge Q applied to the conductive elements <NUM>, <NUM> can be distributed nonuniformly over the conductive elements <NUM>, <NUM>, forming the charge Qa in the region of the first ferroelectric nanoparticle 104a (or on first first sections 110a, 120a of the conductive elements <NUM>, <NUM> corresponding to the first ferroelectric capacitor <NUM>, respectively), the charge Qb in the region of the second ferroelectric nanoparticle 104b (or on sections 110b, 120b of the conductive elements <NUM>, <NUM> corresponding to the second ferroelectric capacitor <NUM>, respectively), and the charge Qd in the region of the dielectric material <NUM> (or on the second portions or the excess portions <NUM>', <NUM>' of the conductive layers <NUM>, <NUM>, respectively, corresponding to the dielectric capacitor <NUM>).

The charges Qa, Qb, and Qd of the corresponding capacitors <NUM>, <NUM>, <NUM> are determined by the equality of the potential at the plates of the capacitors and are determined by the condition: <MAT>, taking into account that Qa + Qb + Qd = Q. Here every particular combination of pluses and minuses corresponds to a polarization state <NUM> of the system, Cf = ε<NUM>εfSf/d is the capacitance of the ferroelectric material and Cd = ε<NUM>εd(S - <NUM>f)/d is the capacitance of the dielectric spacer. From the above condition, one obtains Qa,b = (Cf/Ceff)Q ± Qs, Qd = (Cd/Ceff)Q, where <MAT> is the effective capacitance of the entire system.

<FIG> illustrates the emerging polarization states <NUM> and their total energies W.

In the following, the term "level" refers to a logical level, the two terms are used equivalently.

The levels are represented by the polarization states <NUM> of the ferroelectric nanoparticles 104a, 104b, and vice versa. In other words, the polarization states <NUM> provide the levels. For this reason, the terms "level" and "polarization states" may be used equivalently.

The polarization states <NUM> are preferentially discrete polarization states <NUM>, e. in a sense that a switching between two different polarization states <NUM> is characterized by a subtle, abrupt change of the ferroelectric polarization. In other words, the ferroelectric nanoparticles 104a, 104b are adapted to not assume any stable ferroelectric polarization between the one of the discrete polarization states <NUM>.

The polarization states <NUM> are determined by minimization of the total energy <MAT> <MAT>, that gives the energies corresponding to either of three above states <NUM> defining logic levels, |-<NUM>), |o), and |+<NUM>). Namely, W-<NUM> = (Q - <NUM>Os)<NUM>/<NUM>Ceff, W<NUM> = Q<NUM>/<NUM>Ceff, and W+<NUM> = (Q + 2Qs)<NUM>/<NUM>Ceff. The switching between the logical levels takes place when the field inside the corresponding ferroelectric nanoparticle 104a, 104b exceeds the coercive field Ec. It occurs at four distinct values of the total charge of the capacitor Q<NUM>,<NUM> = ±Qc for level |<NUM>), Q<NUM> = <NUM>Qs - Qc for level |-<NUM>), and Q<NUM> =-<NUM>Qs + Qc for level |+<NUM>), where Qc = CeffEcd.

<FIG>, <FIG>, and <FIG> present the abovementioned energy profiles, W+<NUM>(Q), Wo(Q), W-<NUM>(Q) for the polarization states <NUM>, |-<NUM>), |o), and |+<NUM>). <FIG>, <FIG>, and <FIG> present corresponding three-branch hysteresis loops, and routes for addressing the polarization states <NUM>, |-<NUM>), |o), and |+<NUM>), or switching between them, respectively. The polarization states <NUM>, |-<NUM>), |o), and |+<NUM>) are associated with three branches of the charge-voltage characteristics <MAT> and <MAT>.

<FIG>, <FIG>, <FIG> represent the three existing distinct regimes of topology of the hysteresis loops, determined by the relative strength of the effective charge parameters Qc and Qs.

The energy profile of polarization states <NUM>, |-<NUM>), |o), and |+<NUM>) and transition sequence are exemplified in <FIG> for the case <NUM>Qs > Qc > 2Qs. The terminal points, N<NUM>, correspond to the switching instability of one of the ferroelectric nanoparticles 104a, 104b towards the lowest-energy state with the opposite polarization <NUM>. The corresponding hysteresis loop with sequential switching between the logical levels |-<NUM>), |o), and |+<NUM>) at the said critical charges Q<NUM>, Q<NUM>, Q<NUM>, and Q<NUM> is demonstrated in <FIG>.

<FIG> present the energy profile and charge-voltage characteristics realized under the condition Qc > <NUM>Qs. Although it has three logic levels |-<NUM>), |o), and |+<NUM>) realized at Q=o, the intermediate-ferroelectric-polarization state, |o), is topologically unstable in a sense that once the switching from this logical level to either |-<NUM>) or |+<NUM>) has occurred, the system can never be switched back to the |o) logical level, and a two-branch hysteresis loop with switching between the minimum-ferroelectric-polarization state |-<NUM>) and the maximum-ferroelectric-polarization state |+<NUM>) becomes the only effective regime. The switching of the system to the "hidden" logical level, |o), can be achieved, however, by variation of external parameters, different from the charge, for instance by thermal cycling, involving passing through a high temperature paraelectric state.

<FIG> present the energy profiles and charge-voltage characteristics realized under the condition Qc < <NUM>Qs. There is only one logic level, |o), at zero charge, but hysteretic switching occurs at finite charges, implementing, thus, a three-position relay element, also known as the Schmitt trigger.

Importantly, the hysteresis loops shown in <FIG>), <FIG>) and <FIG>) realize all the topologically possible sets of switching in the <NUM>-levels logic [<NPL>)]. In our embodiment, it is the relation of the material-depended critical parameters, Qs and Qc that determine which type of the logic is realized. The specific switching properties/protocols can be achieved by the selection of the desirable ratio between parameters, Qs and Qc, or by appropriately selecting the size and material composition of the ferroelectric nanoparticles 104a, 104b, respectively.

<FIG> presents an embodiment of a ferroelectric nanoparticle capacitor-device <NUM> similar to the one of <FIG>, alternatively implementing the hysteresis loops shown in <FIG>), <FIG>) and <FIG>).

As compared to <FIG>, the ferroelectric nanoparticle capacitor-device <NUM> of <FIG> is formed with various modifications: It comprises a charge control device <NUM>, consisting of an additional conductive element <NUM> and a dielectric spacer <NUM>. In addition, the ferroelectric nanoparticle capacitor-device <NUM> of <FIG> comprises a temperature-control element <NUM>. It also comprises a force-control element <NUM>. According to various embodiments (not shown), the ferroelectric nanoparticle capacitor-device <NUM> is formed with any, any combination, or all of the described modifications (charge control device <NUM> and/or temperature-control element <NUM> and/or force-control element <NUM>).

The charge control device <NUM> comprises an additional conductive element <NUM> arranged below the first conductive element <NUM>, opposite to the second conductive element <NUM> which is arranged above the first conductive element <NUM>.

The charge control device <NUM> further comprises a dielectric spacer <NUM>, formed as a layer <NUM> of dielectric material between the first conductive element <NUM> and the additional conductive element <NUM> to electrically insulate them from each other. The dielectric spacer <NUM> is composed of one of the dielectric materials described above, and preferentially contains SrTiO3, SiO2, Si3N4, or HfO2.

The charge control device <NUM> is operated by applying a voltage between the additional conductive element <NUM> and the second conductive element <NUM> while the first conductive element <NUM> is kept at a fixed charge (e. , electrically floating), resulting in the application of a charge to the second conductive element <NUM>.

The temperature-control element <NUM> is implemented as a heater <NUM>, more specifically as an Ohmic heater <NUM>. The heater <NUM> is arranged below a conductive element <NUM>, <NUM>, to heat the respective conductive element <NUM>, <NUM> and thus the ferroelectric nanoparticles 104a, 104b.

A temperature variation of the ferroelectric nanoparticles 104a, 104b can be of the range <NUM> - <NUM> Kelvin.

The ferroelectric nanoparticle capacitor-device <NUM> of <FIG> further comprises a substrate <NUM> to support the ferroelectric nanoparticle capacitor-device <NUM>.

The substrate is arranged below the conductive elements <NUM>, <NUM>, and below the additional conductive element <NUM> if present. The substrate is in thermal contact with one of the (first, second, or additional) conductive elements <NUM>, <NUM>, <NUM>; e. via a direct physical contact or an indirect contact via a heat-conducting material such as a metal or a sufficiently thin (< <NUM> or < <NUM>) intermediate layer.

Heating the substrate <NUM> using the heater <NUM> leads to a mechanical deformation <NUM> in the form of an expansion <NUM>, that generates strains in the ferroelectric nanoparticles 104a, 104b. Alternatively, the strain can also be induced by the piezoelectric effect developing when the electric field is applied to the substrate <NUM>. For example, the generated strain can lie in the range of <NUM>-<NUM>% of the crystal lattice constant.

The temperature-control element <NUM> and/or the force-control element <NUM> permit to tune the interrelation between the parameters Qs and Qc by the external stimuli temperature and/or strain. They thus allow for an on-the-fly modification of the switching logic of the said device <NUM>. This tuning can be done by accounting for different temperature and strain dependences of these parameters. The so-called hyperelectric materials, for example, LiZnAs, LiBeSb, NaZnSb, and LiBeBi, present the particular interest for implementation of the ferroelectric nanoparticles 104a, 104b, because in these materials the coercive field can achieve values substantially larger than the depolarization electric field, and the relative strengths of the parameters, Qs and Qc can vary over fairly wide ranges.

<FIG> shows an equivalent electric circuit of the ferroelectric nanoparticle capacitor-device <NUM> of <FIG>. The additional conductive element <NUM> and the dielectric spacer <NUM> form an additional capacitor <NUM> with the capacitance Ci. The additional capacitor <NUM> shares the first conductive element <NUM> with the capacitors <NUM>, <NUM>, <NUM>. The equivalent electric circuit therefore comprises the capacitors <NUM>, <NUM>, <NUM> (defined by the conductive elements <NUM>, <NUM>) and the additional capacitor <NUM> (defined by the conductive elements <NUM>, <NUM>) connected in series. The second conductive element <NUM> and the additional conductive element <NUM> receive the incoming voltage Vin between them. The charge at the conductive elements <NUM>, <NUM> induced by the voltage Vin is given by the equation Vin = Q/Ci+V(Q), where V(Q) is the voltage determined by the charge - voltage characteristics such as exemplified in <FIG>, <FIG>, <FIG>. This relation becomes particularly simple and transforms to Q ≈ Ci Vin when the effective capacitance of the parallel arrangement of the capacitors <NUM>, <NUM>, <NUM> substantially exceeds the capacitance of the additional capacitor <NUM>. The charge that controls the polarization state <NUM> of the ferroelectric nanoparticles 104a, 104b is directly tuned by the voltage Vin applied to the second conductive element <NUM> and the additional conductive element <NUM>.

<FIG> illustrates the integration of the ferroelectric nanoparticle capacitor-device <NUM> into a field-effect transistor <NUM>, alternatively implementing the hysteresis loops shown in <FIG>), <FIG>) and <FIG>). <FIG> shows an equivalent electric circuit of the device <NUM> of <FIG>.

The field-effect transistor <NUM> comprises source/drain regions <NUM>, <NUM>, a channel <NUM> extending between the source/drain regions <NUM>, <NUM>, and a gate stack <NUM> arranged over the channel <NUM>. The field-effect transistor <NUM> further comprises a body electrode <NUM>, which is grounded.

The channel <NUM> serves as the additional conductive element <NUM> described in the context of <FIG>.

The gate dielectric <NUM> is a high-κ dielectric layer, preventing a charge leakage between the first conductive element <NUM> and the channel <NUM>.

The gate stack comprises the gate dielectric <NUM>, provided by the dielectric spacer <NUM>, and at least one electrode. In the depicted embodiment, the at least one electrode of the gate stack <NUM> is provided by a ferroelectric nanoparticle capacitor-device <NUM> similar to the one of <FIG>. More specifically, the second conductive element <NUM> of the ferroelectric nanoparticle capacitor-device <NUM> serves as a gate electrode of the transistor <NUM> and is connected to an external voltage source to receive the driving voltage Vin. Preferably, the driving voltage Vin is applied between the second conductive element <NUM> and the additional conductive element (channel) <NUM>, <NUM>, implementing the charge control device <NUM> described above in the context of <FIG>.

As described above in the context of previous embodiments, the first conductive element <NUM> is kept at a constant charge, e. kept electrically isolated and floating. It thus serves to stabilize the polarization <NUM> of the ferroelectric nanoparticles 104a, 104b. Furthermore, the floating first conductive element <NUM> makes the potential along the interface between the ferroelectric nanoparticles 104a, 104b and the first conductive element <NUM> even, maintaining, therefore, a uniform electric field across the gate stack <NUM> and the substrate <NUM>.

The stepwise switching of the voltage, Vout, operating the current in the channel <NUM>, under the appropriate protocol for the variation of the driving voltage Vin realizes the multilevel logic switching sequence corresponding to the one of the topologically possible hysteresis loops (see <FIG>). The logic levels switching order can be modified by the external stimuli, for example, by the temperature or strain, as described above in the context of <FIG>, allowing for the on-fly modification of the switching logics of the ferroelectric nanoparticle capacitor-device <NUM>.

According to different embodiments, the ferroelectric nanoparticle capacitor-device <NUM> is formed with the temperature-control element <NUM> and/or the force-control element <NUM> described above in the context of <FIG>, e. instead of the substrate <NUM>, integrated into the substrate <NUM> or below the substrate <NUM>. In the latter embodiments, a substrate <NUM> with a high heat conductivity is applied.

<FIG> present embodiments of the ferroelectric nanoparticle capacitor-device <NUM> for implementing a topologically configurable <NUM>-level logical unit. <FIG> show the respective polarization states <NUM> representing the <NUM> logical levels.

<FIG> shows a ferroelectric nanoparticle capacitor-device <NUM> with three identical, for example, cylindrical ferroelectric nanoparticles 104a, 104b, 104c between the conductive elements <NUM>, <NUM>. The ferroelectric nanoparticles 104a, 104b, 104c provide equal coercive fields and equal cross-sections.

In the depicted embodiment, a dielectric separator material <NUM> fills the residual space between the conductive elements <NUM>, <NUM>.

The system is driven and controlled by an electric charge, Q, placed onto at least one of the conductive elements <NUM>, <NUM>, using a charge control element <NUM> as described above.

As illustrated in <FIG>, the ferroelectric nanoparticle capacitor-device <NUM> of <FIG> provides the polarization states, (+++), (++-) (or equivalently, (+-+) and (-++)), (+--), or equivalently, (-+-) and (--+), and, finally, (---), wherein arrows down (or up) in <FIG> represent negative "-" or positive "+" polarization with respect to the z axis.

Consequently, the ferroelectric nanoparticle capacitor-device <NUM> of <FIG> realizes a <NUM>-level logic, characterized by the logic levels | +<NUM>), |+<NUM>), |-<NUM>), and |-<NUM>), respectively.

<FIG> shows another embodiment of a ferroelectric nanoparticle capacitor-device <NUM> for implementing a <NUM>-level logic device. Here, two non-equivalent ferroelectric nanoparticles 104a, 104b are disposed between the conductive elements <NUM>, <NUM> and coated by a dielectric separator material <NUM>. The ferroelectric nanoparticles 104a, 104b can be made from different ferroelectric materials and may have different sizes.

<FIG> illustrates the polarization states <NUM> of the ferroelectric nanoparticles 104a, 104b of <FIG>, which are similar to the polarization states <NUM> of <FIG> associated with the ferroelectric nanoparticles 104a, 104b, 104c of <FIG>. However, in <FIG>, since the states (+-) and (-+) are not equivalent, the four polarization states <NUM> implement the logical levels of a <NUM>-level logic unit, namely, (--) ↔ |-<NUM>), (-+) ↔ |-<NUM>), (+-) ↔ |+<NUM>), and (++) ↔ |+<NUM>).

Except for the number or the size/material composition of the ferroelectric nanoparticles 104a, 104b, 104c, the embodiments of <FIG> are similar to the embodiment of <FIG>. In alternative embodiments (not depicted), the ferroelectric nanoparticles 104a, 104b, 104c described in the context of <FIG> (i. , with the respective number or with the respective size/material composition) are applied in a ferroelectric nanoparticle capacitor-device <NUM> similar to the embodiment of <FIG> or <FIG>.

<FIG>, <FIG> illustrate charge-voltage hysteresis loops associated with the polarization states <NUM> of ferroelectric nanoparticle capacitor-devices <NUM> similar to the ones of <FIG>.

Considerations similar to those given above for the <NUM>-level logic units, show that the hysteresis loops V(Q) for the said <NUM>-level configurations of the ferroelectric nanoparticles 104a, 104b have four branches corresponding to the logical levels <NUM>, |+<NUM>), | +<NUM>), |-<NUM>), and |-<NUM>). <FIG>, <FIG> present all possible hysteresis loops with different switching sequences in <NUM>-level logic [Baudry, L. , Lukyanchuk, I. , and Vinokur, V. <NUM>, <NUM> (<NUM>)].

<FIG> shows a charge-voltage hysteresis loop with the sequential switching between the logical levels/polarization states <NUM>, |+<NUM>), | +<NUM>), |-<NUM>), and |-<NUM>), driven by changing the charge Q at the conductive elements <NUM>, <NUM>.

The charge-voltage hysteresis loops in <FIG> correspond to different switching sequences between logical levels/polarization states <NUM>, |+<NUM>), |+<NUM>), |-<NUM>), and |-<NUM>) that can be used or the design of the four-level logic memories or other processing protocols with different topological ways of accessing the information stored at these logical levels/polarization states <NUM>, |+<NUM>), | +<NUM>), |-<NUM>), and |-<NUM>).

The charge-voltage hysteresis loops of <FIG> comprise "hidden" logical levels |-<NUM>), |<NUM>). Such protocols can be used if the information, stored at the "hidden levels" |-<NUM>), |<NUM>) needs to be protected from undesirable change and other interferences. Any attempt to access these levels | -<NUM>), |<NUM>) will immediately switch the corresponding information unit to another level |-<NUM>), |<NUM>) with no possibility of the back restoring. Therefore, the said charge-voltage hysteresis loops provide the security protection of the ferroelectric nanoparticle capacitor-device <NUM>, which is an especially novel feature of our disclosure.

The charge-voltage hysteresis loops of <FIG> implement the multilevel Schmitt trigger, required for multiple applications in electronics.

The ferroelectric nanoparticle capacitor-device <NUM> of <FIG>, via selection of appropriate sizes and material compositions of the ferroelectric nanoparticles 104a, 104b, 104c, enables the implementation of any preselected charge-voltage hysteresis loop of the charge-voltage hysteresis loops represented in <FIG>, <FIG>.

Controlling external stimuli, for instance, the temperature or strain, as described above in the context of <FIG>, <FIG>, the charge-voltage hysteresis loop and the switching sequence between the logical levels/polarization states <NUM>, |+<NUM>), | +<NUM>), |-<NUM>), and |-<NUM>) can be selected and modified on-the-fly, i. after fabrication of the ferroelectric nanoparticle capacitor-device <NUM> with given sizes and material compositions of the ferroelectric nanoparticles 104a, 104b, 104c.

Similarly, the charge-voltage hysteresis loop can be controlled for a ferroelectric nanoparticle capacitor-device <NUM> comprising more than three, for example, four, five, or any larger number of ferroelectric nanoparticles104a, 104b, 104c. The charge-voltage hysteresis loop can be controlled initially via selection of an appropriate number of appropriate ferroelectric nanoparticles 104a, 104b, 104c and their sizes and material compositions. A later, on-the-fly control is achieved by incorporating a temperature-control element <NUM> or a force-control element as described above. To ensure a sufficient spacing between the polarization states <NUM> in terms of total energy W, voltage V and/or charge Q, a smaller number of ferroelectric nanoparticles 104a, 104b, 104c such as up to <NUM>, <NUM>, <NUM> or three ferroelectric nanoparticles104a, 104b, 104c is preferable. In other words, the number of polarization states <NUM> should be limited, e. to up to <NUM>, <NUM>, <NUM>, <NUM>, or <NUM> polarization states <NUM>. A smaller number of ferroelectric nanoparticles 104a, 104b, 104c and/or number of polarization states <NUM> improves the reliability of the switching and of the readout of the polarization state <NUM>.

Embodiments with more than three ferroelectric nanoparticles 104a, 104b, 104c use the (ferroelectric and/or dielectric) materials described above, as well as the temperature and/or strain ranges described above; also the remaining device parameters are similar to the ones described above. Devices comprising any other number of the nanoparticles and their configuration realize multilevel logic units possessing more complicated routes for the charge-voltage hysteresis loops enabling, therefore, even higher levels of the neuromorphic computing.

<FIG> illustrates a method <NUM> for operating the ferroelectric nanoparticle capacitor-device <NUM>.

The ferroelectric nanoparticle capacitor-device <NUM> is similar to one of the ferroelectric nanoparticle capacitor-devices <NUM> described above in the context of <FIG>, <FIG>, <FIG>, <FIG>. Any of those ferroelectric nanoparticle capacitor-devices <NUM> provides a maximum-ferroelectric-polarization state (and a minimum-ferroelectric-polarization state) with a maximum (and a minimum) ferroelectric polarization, such that no polarization state of the at least three polarization states has a ferroelectric polarization larger (or smaller, respectively) than the maximum-ferroelectric-polarization state (or the minimum-ferroelectric-polarization state). Moreover, any of those ferroelectric nanoparticle capacitor-devices <NUM> provides an intermediate-ferroelectric-polarization state with a polarization between the minimum ferroelectric polarization and the maximum ferroelectric polarization.

At step <NUM>, the method <NUM> comprises selecting an intermediate-ferroelectric-polarization state.

At step <NUM>, the method <NUM> comprises selecting a first voltage or charge according to the selected intermediate-ferroelectric-polarization state.

At step <NUM>, the method <NUM> comprises applying the first voltage or charge to a conductive element <NUM>, <NUM> of the pair to set the ferroelectric nanoparticles 104a, 104b, 104c to the selected intermediate-ferroelectric-polarization state.

Preferentially, the current polarization state <NUM> of the ferroelectric nanoparticles 104a, 104b, 104c is detected based on a voltage of at least one of the conductive elements <NUM>, <NUM>. For this purpose, the voltage between the conductive elements <NUM>, <NUM> is measured, which corresponds to the voltage in the charge-voltage hysteresis loop described above. For a given device, the measured voltage is thus directly associated with the polarization state <NUM>.

Alternatively, the current polarization state <NUM> of the ferroelectric nanoparticles 104a, 104b, 104c is detected based on a change of the voltage of at least one of the conductive elements <NUM>, <NUM>, such as by counting jumps of the voltage of at least one of the conductive elements <NUM>, <NUM>. For this purpose, the voltage measurement is performed continuously to identify the change of the voltage.

Amongst the two options of selecting a first voltage or charge, the selecting the first charge is preferred. Correspondingly, applying the first charge is preferred.

The other conductive element <NUM>, <NUM> of the pair is kept at a constant electrical charge.

Preferably, the first voltage or charge is applied between one of the conductive elements (i. , the second conductive element <NUM> described above) and the additional conductive element <NUM>, <NUM> described above, preferably using the charge control device <NUM> described above.

When applied to a ferroelectric nanoparticle capacitor-device <NUM> with a charge-voltage hysteresis loop as illustrated in <FIG>, the voltage or charge applied to the conductive element <NUM>, <NUM> is continuously increased until the first voltage or charge is reached. To reach a polarization state <NUM> with a larger or smaller (i. , more negative) polarization, a larger or smaller voltage or charge is applied to the conductive element <NUM>, <NUM>.

Thereafter, the voltage or charge applied to the conductive element <NUM>, <NUM> may be reduced to zero whereupon the polarization state <NUM> remains preserved. The ferroelectric nanoparticle capacitor-device <NUM> thus implements a non-volatile memory, which can be used to store information without external power, voltage, or charge support.

When applied to a ferroelectric nanoparticle capacitor-device <NUM> with a charge-voltage hysteresis loop as illustrated in <FIG>, to reach the intermediate-ferroelectric-polarization state |+<NUM>), the voltage or charge applied to the conductive element <NUM>, <NUM> first needs to be increased to a positive value sufficient to reach state |+<NUM>). Thereafter, the applied voltage is decreased until the negative first voltage or charge is reached, setting the polarization to state |+<NUM>). An inverse voltage or charge sequence is applied to the conductive element <NUM>, <NUM> to reach the intermediate-ferroelectric-polarization state |-<NUM>).

When applied to a ferroelectric nanoparticle capacitor-device <NUM> with a charge-voltage hysteresis loop as illustrated in <FIG>, to reach the intermediate-ferroelectric-polarization state |+<NUM>), the voltage or charge applied to the conductive element <NUM>, <NUM> first needs to be increased to a positive value sufficient to reach state |+<NUM>). Thereafter, the applied voltage is decreased to a negative value until the ferroelectric nanoparticles 104a, 104b, 104c switch to the state |-<NUM>). Thereafter, the applied voltage is increased until the positive first voltage or charge is reached, setting the polarization <NUM> to state |+<NUM>). An inverse voltage or charge sequence is applied to the conductive element <NUM>, <NUM> to reach the intermediate-ferroelectric-polarization state |-<NUM>).

In a ferroelectric nanoparticle capacitor-device <NUM> with a "hidden state", such as illustrated in the context of <FIG>, <FIG>, heating the ferroelectric nanoparticles 104a, 104b, 104c and/or applying a mechanical force to the ferroelectric nanoparticles 104a, 104b, 104c can be used to set the polarization state <NUM> of the ferroelectric nanoparticles 104a, 104b, 104c to the hidden state.

Alternatively, heating the ferroelectric nanoparticles 104a, 104b, 104c and/or applying a mechanical force to the ferroelectric nanoparticles 104a, 104b, 104c is used to modify the charge-voltage hysteresis loop of the ferroelectric nanoparticle capacitor-device <NUM>.

Claim 1:
A ferroelectric nanoparticle capacitor-device (<NUM>), comprising:
a pair of conductive elements (<NUM>, <NUM>) electrically insulated from each other, wherein a first conductive element (<NUM>) of the pair is electrically floating;
a charge control device (<NUM>) adapted to change a charge on a second conductive element (<NUM>) of the pair; and
ferroelectric nanoparticles (104a, 104b) arranged between the conductive elements (<NUM>, <NUM>) of the pair and adapted to provide respective individual polarization states;
wherein the ferroelectric nanoparticles (104a, 104b) are adapted to provide at least three polarization states (<NUM>) with different total ferroelectric polarizations, wherein the at least three polarization states (<NUM>) refer to combinations of the individual polarization states of the ferroelectric nanoparticles (104a, 104b);
wherein the charge control device (<NUM>) comprises an additional conductive element (<NUM>) electrically insulated from the pair of conductive elements (<NUM>, <NUM>); and
wherein the charge control device (<NUM>) is adapted to apply a voltage between the additional conductive element (<NUM>) and the second conductive element (<NUM>).