A method for preparing a sidewall two-dimensional electron gas and applications thereof

Abstract

The application discloses a preparation method and application of a sidewall two-dimensional electron gas, and belongs to the technical field of oxide electronics and micro-nano devices. The method comprises the following steps: growing a BaTiO3 ferroelectric film on a SrTiO3 substrate; preparing source-drain electrodes by using photolithography and magnetron sputtering; forming a sidewall structure by using photolithography and ion bombardment process, and inducing the formation of a two-dimensional electron gas at a BaTiO3 / SrTiO3 interface; and forming a conductive channel at a domain wall by regulating BaTiO3 ferroelectric polarization through an external electric field. Through the synergistic regulation of the sidewall structure and the ferroelectric domain wall, the spatial controllable distribution of the interface two-dimensional electron gas is realized, the electrons are directionally aggregated in the domain wall region, and thus a stable conductive path is constructed on a nanometer scale. The method has simple preparation process, good repeatability, is compatible with existing thin film growth and micro-nano processing technology, and can be applied to the fields of multi-value storage, reconfigurable logic circuits and neuromorphic computing.

Description

Technical Field

[0001] This invention belongs to the field of oxide electronics and micro / nano device technology, specifically relating to a method for preparing and applying a two-dimensional electron gas with sidewalls. Background Technology

[0002] Ferroelectric domain wall conductive devices, as a novel type of nanoscale functional electronic device, can realize localized conductive channels by utilizing the nanoscale domain walls inside ferroelectric materials. With advantages such as dynamic electric field control over domain wall location and conductivity state, small size, low power consumption, and high integration, they show great application potential in cutting-edge fields such as high-density information storage, reconfigurable electronics, neuromorphic computing, and synaptic-like devices. Unlike traditional bulk conductive semiconductor devices, ferroelectric domain walls are only a few to tens of nanometers wide, allowing for dynamic construction, erasure, and reconstruction of conductive channels through external field control, thus meeting the miniaturization, low power consumption, and multifunctionality requirements of next-generation micro / nanoelectronic devices.

[0003] However, existing ferroelectric domain wall conductive devices still face several core technological bottlenecks in practical applications: First, domain wall conductivity is highly dependent on the accumulation of local defect carriers, and the number of carriers supplied by defects such as oxygen vacancies is limited, resulting in weak domain wall conductivity and poor transport stability; Second, traditional domain wall conductivity mainly relies on the random aggregation of oxygen vacancies, and the spatial distribution of defects is highly random, causing uneven morphology and uncontrollable position of conductive channels, making it difficult to guarantee the uniformity and repeatability of devices; Third, ferroelectric domain structures are susceptible to environmental temperature fluctuations, external electric field disturbances, and mechanical stress interference, which can cause domain wall drift and polarization reversal, leading to significant fluctuations in conductivity and insufficient long-term device reliability; Fourth, existing control methods are mostly concentrated on two-dimensional planar interfaces, lacking the spatial constraint and coupling of three-dimensional structures on the interface electron gas, making it difficult to achieve precise directional control of conductive channels.

[0004] Recent studies have confirmed that high carrier density two-dimensional electron gases can be formed at oxide heterojunctions, possessing excellent electron transport properties and providing a stable and continuous electron source for conductive channels. Furthermore, by combining geometric structure manipulation to optimize the spatial distribution of the two-dimensional electron gas, a synergistic gain effect can be achieved with ferroelectric domain wall conductivity. However, current technologies lack a method for stably forming a two-dimensional electron gas and achieving efficient coupling between it and ferroelectric domain walls; the synergistic control mechanism between the two-dimensional electron gas and domain wall conductivity under sidewall three-dimensional structures remains undeveloped. Therefore, developing a method for fabricating sidewall two-dimensional electron gas-based ferroelectric domain wall conductive devices that combines high stability, high uniformity, spatial controllability, and dynamic reconfigurability is a key technological challenge that urgently needs to be overcome in this field. Summary of the Invention

[0005] Technical Problem Solved: To address the aforementioned technical problems, this invention provides a method for preparing and applying a two-dimensional electron gas with sidewalls. By epitaxially growing a BaTiO3 ferroelectric thin film on a SrTiO3 substrate, and combining the construction of a three-dimensional sidewall structure with ion bombardment-induced oxygen vacancies to form an interfacial two-dimensional electron gas, a stable electron source is constructed at the BaTiO3 / SrTiO3 interface. Simultaneously, an external electric field is used to modulate the BaTiO3 ferroelectric domain structure, forming an electron potential well through the local electric field at the domain walls, inducing the directional enrichment of electrons in the two-dimensional electron gas, and forming a continuous and controllable one-dimensional conductive channel at the nanoscale domain walls. The sidewall structure further strengthens the spatial coupling between the two-dimensional electron gas and the domain walls, improving the continuity and stability of electron transport. This effectively solves the defects of existing ferroelectric domain wall conductive devices, such as insufficient carrier supply, random and uncontrollable conductive channels, poor stability, and limited controllability.

[0006] Technical solution: In a first aspect, the present invention provides a method for preparing a two-dimensional electron gas with sidewalls, comprising the following steps: Step 1: BaTiO3 ferroelectric thin films are grown on SrTiO3 substrates by physical vapor deposition to form a functional layer with ferroelectric polarization characteristics. Physical vapor deposition can achieve precise control of the crystal structure and orientation of the thin film by adjusting parameters such as deposition temperature, oxygen partial pressure, and deposition rate, thereby obtaining a thin film with stable ferroelectric polarization performance. Step 2: Source and drain electrodes are prepared using photolithography and magnetron sputtering: The photolithography process includes spin coating of photoresist, pre-baking, masking, alignment, exposure and development, etc., to define source and drain electrode patterns on the surface of BaTiO3 ferroelectric thin film, and then gold electrodes are deposited by magnetron sputtering. Step 3: The structure is processed by photolithography and ion bombardment to form a three-dimensional structure with sidewalls. At the same time, by controlling the ion energy and bombardment conditions, ions are made to penetrate the BaTiO3 ferroelectric film and act on the SrTiO3 interface, generating oxygen vacancies and releasing electrons at the interface, which provides the basis for the formation of a two-dimensional electron gas. Step four involves polarizing a BaTiO3 ferroelectric thin film to form a domain structure. This generates a local electric field at the charged domain walls, causing electrons in the two-dimensional electron gas to gather towards the domain wall region, thereby forming a conductive channel in the originally insulating region and establishing a conductive path.

[0007] Preferably, the specific process for preparing the BaTiO3 ferroelectric thin film in step one is as follows: S1-1, the SrTiO3 substrate is treated by a surface treatment method of ultrasonic cleaning combined with high temperature annealing to form an atomically flat surface structure terminated by TiO2. S1-2 uses pulsed laser deposition to achieve single-crystal oriented growth of BaTiO3 thin films on SrTiO3 substrates by controlling the deposition temperature, oxygen partial pressure and deposition rate. S1-3, BaTiO3 films were annealed in an environment with an oxygen partial pressure of 0.5 atmospheres to obtain an atomically smooth surface and stable ferroelectric polarization characteristics.

[0008] Furthermore, the SrTiO3 substrate is a (001) oriented single crystal substrate, and is subjected to ultrasonic and high-temperature annealing treatment to obtain an atomically flat surface.

[0009] Furthermore, the BaTiO3 ferroelectric thin film is grown by pulsed laser deposition (PLD) and the thickness of the ferroelectric thin film is 5-150 nm, preferably 10-50 nm, to ensure the stable existence of ferroelectric polarization.

[0010] Preferably, in step two, the magnetron sputtering conditions are 5 × 10⁻⁶. -6 ~8×10 -6 Deposition was performed at mbar gas pressure and 50–100 W power for 3–10 minutes; the source and drain electrodes were gold electrodes with a thickness of 60–100 nm.

[0011] Preferably, the specific process of step three is as follows: S3-1. Define the device region using photolithography based on the source and drain electrode positions; S3-2. Anisotropic etching of BaTiO3 thin films is performed by ion bombardment to form three-dimensional channels with sidewall structures; S3-3. By controlling the ion energy and bombardment time, some ions can penetrate the BaTiO3 film and act on the BaTiO3 / SrTiO3 interface, inducing the formation of oxygen vacancy defects in the interface region.

[0012] Furthermore, the ion bombardment employs Ar... + Ions bombarded at energies of 0.5–5 keV for 10–300 s, and oxygen vacancy defects were induced in the interfacial region by controlling the ion energy and bombardment time.

[0013] Preferably, in step four, different voltages are applied between the electrode and the two-dimensional electron gas according to the sidewall height. When the sidewall height is 10 to 150 nm, the applied voltage is 10V to 80V.

[0014] In a second aspect, the present invention provides a conductive device with a two-dimensional electron gas on the sidewalls prepared by the preparation method described in the first aspect, comprising a SrTiO3 substrate, a BaTiO3 ferroelectric thin film, and source / drain electrodes; wherein a two-dimensional electron gas is formed at the BaTiO3 / SrTiO3 interface, and a conductive channel is formed in the domain wall region by means of the sidewall structure and the ferroelectric domain wall regulation.

[0015] Preferably, the conductive device exhibits three switchable conductive states under the control of an applied electric field: an insulating state, a rectifying state, and a linear conducting state. Specifically, under negative bias, the device is in the insulating state with a current less than 4 pA. As the forward voltage increases to the range of 10–30 V, the device switches to the rectifying state, with a forward bias current reaching 50–1000 μA, while the reverse current is less than 10 μA, and the rectification ratio is greater than 10. When the applied voltage is further increased to 30–50 V, the device enters the linear conducting state, with a current reaching 500 μA–10 mA, and exhibits approximately ohmic conductivity characteristics.

[0016] Furthermore, in the linear conduction state, a high-density two-dimensional electron gas is formed at the BaTiO3 / SrTiO3 interface, with a surface carrier concentration of approximately 5 × 10⁻⁶. 12 ~2×10 13 cm -2 The carrier mobility is approximately 1–10 cm⁻¹. 2 ·V -1 ·s -1 Under a relatively high applied electric field (30–50 V), the interface electrons are significantly enriched and form a continuous conductive channel, which makes the device exhibit near-ohmic transport characteristics and has a high current carrying capacity (1–10 mA) and good electrical stability.

[0017] Thirdly, the present invention provides the application of the conductive device described in the second aspect in the field of novel electronic devices. The conductive device utilizes the ferroelectric domain walls to regulate the distribution of charge carriers at the interface, thereby achieving multi-state switching from the insulating state and the rectified state to the linear conducting state. It also has reconfigurable conductive channels and local controllability, and can be applied to fields such as multi-valued storage devices, reconfigurable logic circuits, neuromorphic computing devices, and low-power information processing systems.

[0018] The core of this invention involves forming a two-dimensional electron gas at the SrTiO3 interface within a BaTiO3 / SrTiO3 heterostructure through sidewall structure design and ion modulation. This constructs domain structures within the BaTiO3 ferroelectric thin film, and the effective coupling between the two-dimensional electron gas and the ferroelectric domain walls is achieved using the sidewall geometry. Initially, the ferroelectric thin film is in an insulating state. Under the influence of an applied electric field and interfacial electron supply, electrons directionally accumulate at the charged domain walls, gradually activating the originally insulating domain wall regions and transforming them into conductive channels. This achieves a controllable transition from an insulating to a conductive state. These conductive channels are not pre-existing but dynamically formed through interfacial electron injection and localized electric field modulation, exhibiting excellent tunability and stability.

[0019] This invention controls ion bombardment conditions to allow ions to penetrate ferroelectric thin films and act on the STO interface, introducing oxygen vacancies and forming a two-dimensional electron gas. This two-dimensional electron gas acts as an electron source, continuously supplying charge carriers to the domain wall regions. Simultaneously, the localized electric field generated by the ferroelectric domain walls forms a potential well structure, inducing electrons to accumulate at the domain walls. This breaks the original insulating state, "opening up" conductive channels at the nanoscale and forming stable one-dimensional conductive paths. The sidewall structure further enhances the spatial coupling and transport continuity of electrons, creating a synergistic conductive network between the interface two-dimensional electron gas and the domain wall conductive channels.

[0020] This structure exhibits significant reversible controllability: under conditions without an external electric field, or after a certain period of relaxation, and after external heat treatment (such as heating to near or above the Curie temperature of BaTiO3, which is approximately 120°C), the ferroelectric polarization gradually weakens or reverses, the original domain structure is reconstructed, leading to the disappearance or alteration of local potential wells at the domain walls, thereby gradually closing the formed conductive channels and restoring the system to a high-resistance insulating state. Subsequently, by reapplying an external electric field to polarize the BaTiO3 film, the formation of domain structures and charged domain walls can be induced again at specific locations, and the conductive channels can be reconstructed under the supply of two-dimensional electron gas at the interface, realizing the "erasure-rewrite" cycle operation of the conductive path.

[0021] The process exhibits good cyclic stability and repeatability, giving the system memristor-like behavior and reconfigurable electronic channel characteristics, which can be applied to programmable nanoelectronic devices, neuromorphic computing, and high-density information storage.

[0022] Beneficial effects: 1) This invention introduces oxygen vacancies at the BaTiO3 / SrTiO3 interface by ion bombardment, constructs a high-density two-dimensional electron gas, provides a continuous and stable electron source for the domain wall conductive channel, completely solves the technical pain points of traditional domain wall conductivity relying on random defects, insufficient carrier supply, and weak conductivity, and fundamentally improves the conductivity consistency and long-term reliability of the device. 2) This invention achieves precise control of the position and morphology of conductive channels through three-dimensional sidewall structure constraints and local electric field modulation of ferroelectric domain walls, abandoning the traditional conductive mechanism of random aggregation of oxygen vacancies; the device can realize the reversible cycle of "construction-erasure-reconstruction" of conductive channels through electric field, thermal excitation and time relaxation, and has memristor-like characteristics, which are suitable for the core needs of reconfigurable electronics, multi-value storage and neuromorphic computing. 3) Achieving continuous and adjustable insulation, rectification, and linear conduction states within a single device, with current ranging from pA to mA, spanning multiple orders of magnitude, significantly improving information carrying capacity and device functional integration, and providing a new technical path for multi-valued logic, multi-functional micro-nano devices, and in-memory computing hardware; 4) This invention employs mature micro-nano fabrication processes such as pulsed laser deposition, photolithography, ion etching, and magnetron sputtering. The fabrication process is simple, has good repeatability, and is highly compatible with existing oxide electronics and semiconductor manufacturing processes. It can realize device arraying and large-scale integration, and has broad prospects for engineering applications. 5) Breaking through the traditional technical bias that domain wall conductivity depends on random defects and is limited to two-dimensional plane, a new paradigm of synergistic coupling regulation of three-dimensional sidewall structure, two-dimensional interface electron gas, and ferroelectric domain wall was established for the first time, extending the regulation of interface electrons from two-dimensional plane to quasi-three-dimensional space; it was confirmed that the synergistic effect of two-dimensional electron gas and domain wall electric field can take into account both high conductivity and high controllability, providing a new physical mechanism and realization path for charge regulation of oxide electronics. 6) By utilizing the local electric field of ferroelectric domain walls to efficiently bind and control charge carriers, rapid switching of the conduction state can be achieved at a lower driving voltage, taking into account both low power consumption and fast response characteristics, which is in line with the development direction of next-generation low-power and miniaturized electronic devices. Attached Figure Description

[0023] Figure 1 This is a flowchart of the fabrication method of a two-dimensional electron gas domain wall conductive device based on the BaTiO3 / SrTiO3 interface provided in the embodiments of the present invention; Figure 2 This is a schematic diagram of the sidewall structure and interface two-dimensional electron gas formation process provided in the embodiment of the present invention; wherein, (a) epitaxial growth forms a heterostructure, (b) ion bombardment induces the generation of oxygen vacancies, and (c) oxygen vacancies release electrons and form a two-dimensional electron gas at the interface. Figure 3 These are electrical performance diagrams of the device provided in the embodiments of the present invention, wherein: (a) a schematic diagram of the device structure; (b) current-voltage characteristic curves before and after polarization; (c) current-voltage characteristic curves of the device in three conduction states; and (d) electrical switching characteristics of the device in three negative conduction states. Figure 4 This is a schematic diagram of the coupling mechanism between two-dimensional electron gas and ferroelectric domain walls provided in the embodiments of the present invention, wherein: (a) device structure and ion bombardment; (b) schematic diagram of band structure; (c) oxygen vacancy migration and enrichment; (d) coupled conductive network. Detailed Implementation

[0024] The present invention will be described in detail below with reference to specific embodiments: Example 1

[0025] like Figures 1-2 As shown, a method for preparing a two-dimensional electron gas with sidewalls includes the following steps: First, BaTiO3 ferroelectric thin films were prepared on SrTiO3 single crystal substrates by epitaxial growth: Specifically, the (001) oriented SrTiO3 substrates were pretreated by ultrasonic cleaning with deionized water, acetone and ethanol in sequence for 10 minutes each time, and annealed at 700°C for 3 hours in an oxygen atmosphere to obtain an atomically flat surface with TiO2 termination; then, BaTiO3 thin films were grown by pulsed laser deposition (PLD) at 750°C and oxygen pressure of 0.05 mbar, and annealed at 700°C for 1.5 hours in an oxygen partial pressure of 0.5 atm to stabilize their ferroelectric polarization performance, and the film thickness was controlled at 30 nm.

[0026] Secondly, source and drain electrodes were fabricated using standard photolithography and magnetron sputtering: positive photoresist was spin-coated onto the BaTiO3 thin film at a spin speed of 4000 r / min for 45 s, followed by pre-baking at 95℃ for 1.5 minutes and an exposure dose of 200 mJ / cm². 2 The development time is 45 seconds. After exposure and development, the electrode pattern is defined and then applied to a 6×10⁻⁶ area. -6 A gold electrode approximately 60 nm thick was sputtered at mbar pressure and 80 W power to form the source-drain structure of the device. The source-drain electrode spacing was 10 μm and the width was 3 μm.

[0027] Subsequently, Ar was combined through photolithography. + Ion bombardment constructs sidewall structures and induces the formation of two-dimensional electron gas at the interface: (1) Define the device channel region (width 0.5 mm, length 0.6 mm), and then bombard it with Ar at an energy of 5 keV for a bombardment time of 300 s. + Ions were used for anisotropic etching at an 80° incident angle to form a three-dimensional structure with distinct sidewalls in the BaTiO3 film. The sidewall height was 30 nm, and the perpendicularity deviation did not exceed 3°. Simultaneously, by controlling the ion energy, some ions were allowed to penetrate the BaTiO3 film, inducing oxygen vacancies at the BaTiO3 / SrTiO3 interface. The oxygen vacancy concentration was 5 × 10⁻⁶. 19 cm -3 This releases electrons and constructs a two-dimensional electron gas with a high carrier density of 1×10⁻⁶. 13 cm -2 The carrier mobility is 5cm 2 ·V -1 ·s -1 .

[0028] Figure 2(a) is a schematic diagram of the heterojunction structure formed by epitaxial growth. The BaTiO3 film is deposited on the surface of the SrTiO3 substrate, and the two form an atomic-level contact structure at the interface. The figure also shows the oxygen vacancies, electrons and lattice atomic arrangement, which provides a structural basis for the subsequent two-dimensional electron gas formation mechanism. Figure 2 (b) is a schematic diagram of the process of oxygen vacancy generation induced by ion bombardment, in Ar + Under the action of an ion beam, a large number of oxygen vacancy defects are generated near the BaTiO3 / SrTiO3 interface, accompanied by electron release and migration. The formation of oxygen vacancies changes the local potential distribution of the interface, providing conditions for electrons to accumulate at the interface. Figure 2 (c) is a schematic diagram of the release of electrons from oxygen vacancies and the formation of a two-dimensional electron gas at the interface. The electrons released from the oxygen vacancies are locally bound by the interface potential well and form a high-mobility two-dimensional electron gas (2DEG) along the interface direction. The band structure shows that the electrons are confined to the region near the interface, thereby realizing the formation of the interface conductive channel.

[0029] Through the above steps, a stable two-dimensional electron gas can be constructed at the BaTiO3 / SrTiO3 interface, and its effective coupling with the ferroelectric domain walls can be achieved by combining the sidewall structure. This enables the construction and extension of conductive channels along the sidewall direction, extending interface control from a two-dimensional plane to a quasi-three-dimensional space, providing a new paradigm for complex device structure design and multi-dimensional transport control. Through the synergistic mechanism of "stable supply of two-dimensional electron gas at the interface + precise control of the ferroelectric domain structure," deterministic construction of conductive paths is achieved, fundamentally reducing randomness and improving device consistency and engineering controllability, which has a significant promoting effect on scalable applications. Ferroelectric polarization can be weakened or reversed through time relaxation or thermal excitation, thereby closing the conductive channel; the conductive path can be restored through repolarization. This "dynamic generation-elimination-reconstruction" mechanism extends the traditional static conductive structure into a programmable and evolvable electronic system, which has significant implications for the development of reconfigurable electronics and neuromorphic computing hardware.

[0030] Example 2

[0031] The specific fabrication process of a multi-state domain wall conductive device based on a two-dimensional electron gas on the sidewalls (prepared in Example 1) is as follows: Polarization of the BaTiO3 ferroelectric thin film was controlled by applying an external electric field. A DC voltage of 30 V was applied for 30 s, forming ferroelectric domain structures with different orientations. Charged domain walls were formed between adjacent domains, and the local electric field generated potential wells in the sidewall regions. This caused electrons in the two-dimensional electron gas at the interface to migrate directionally towards the domain walls and accumulate, thereby forming a continuous one-dimensional conductive channel in the originally insulating region. This enabled the controllable transition of the device from an insulating state to a conductive state.

[0032] Figure 3Image (a) is a schematic diagram of the two-dimensional electron gas domain wall conductive device provided in this embodiment and its electrical characteristic curves. This device exhibits significant multi-state transport behavior under applied voltage regulation; see also... Figure 3 In (b), the device exhibits significantly different current-voltage characteristics before and after polarization; it is in an insulating state at low voltage, with current in the pA range; see also Figure 3 In step (c), as the forward voltage increases to the range of 10–20 V, the device switches to a rectifier state, with a forward current reaching 50–1000 μA and a rectification ratio greater than 10. 3 When the voltage is further increased to 20-30 V, the device enters the linear conduction state, the current reaches 500 μA-10 mA, and it exhibits near-ohmic contact characteristics.

[0033] Figure 4 (a) is a schematic diagram of the two-dimensional electron gas distribution at the interface; Figure 4 (b) shows the ferroelectric domain structure and the electric field distribution of the domain walls. It can be seen that there is an obvious local electric field enhancement region at the domain walls. Figure 4 Figure (c) shows that under the influence of the local electric field, electrons are enriched at the domain walls and form conductive channels; the experimental results show that the conductive channels are continuously distributed along the sidewall direction, demonstrating good spatial controllability. Figure 4 Figure (d) shows a schematic diagram of the coupled conductive network. Under the combined action of the local electric field and the domain wall conductivity effect, the two-dimensional electron gas on the sidewall is coupled to the conductive channel on the domain wall to form a continuous conductive network structure. Among them, the electrons mainly come from the two-dimensional electron gas at the STO interface and are transported along the conductive path, indicating that there is a stable and controllable conductive coupling behavior inside the device.

[0034] The two-dimensional electron gas device on the sidewalls of this embodiment exhibits an insulating state current below 4 pA, a rectified state current of 50–1000 μA, and a high conduction state current reaching 10 mA, with conductivity variations spanning seven orders of magnitude; the surface carrier concentration of the interface two-dimensional electron gas is 2 × 10⁻⁶. 13 cm -2 The migration rate is approximately 10 cm. 2 ·V -1 ·s -1 The device exhibits good stability and repeatability, with no significant attenuation of conductivity during multiple cycles. After 1000 hours of continuous operation at room temperature, the conductivity degradation does not exceed 5%.

[0035] Based on the results of the interface electron gas distribution and ferroelectric domain structure characterization, this embodiment proposes that the conductivity mechanism of the device originates from the synergistic effect of "interface two-dimensional electron gas supply - domain wall local electric field modulation": the two-dimensional electron gas provides a stable electron source, while the domain wall potential well spatially confines and modulates the electrons, thereby realizing the dynamic construction and control of the conductive channel.

[0036] Comparative Example To verify the effect of the two-dimensional electron gas structure on the conductivity of the device, a conventional BaTiO3 / SrTiO3 ferroelectric device without an interface two-dimensional electron gas and sidewall coupling structure was fabricated as a comparative example. Specifically, only a BaTiO3 ferroelectric thin film was grown on a SrTiO3 substrate, and the source and drain electrodes were formed using the same photolithography and electrode fabrication process, but no sidewall structure etching was performed, nor was ion bombardment-induced oxygen vacancy operation performed. Therefore, no two-dimensional electron gas was formed at the BaTiO3 / SrTiO3 interface. Subsequently, polarization treatment was performed under the same conditions as in Example 2.

[0037] Test results show that the comparative device consistently exhibits typical PN junction rectification transport characteristics under forward bias, with its current-voltage curve showing a significant nonlinear change. Within the 10–30 V bias range, the device current is approximately 10–50 μA. In the negative bias range, the comparative device maintains a high-resistance insulation state, with a current below 10 pA, and no significant conduction state switching behavior was observed. In contrast, the device of this application also exhibits rectification transport characteristics at lower voltages, but as the applied voltage increases further, the device can transition from a rectification state to a stable linear conduction state. When the bias voltage increases to 30–50 V, the device exhibits significant near-ohmic linear transport characteristics in both the positive and negative directions, with a conduction current reaching 500 μA–10 mA, an improvement of approximately 1–2 orders of magnitude compared to the comparative device. Simultaneously, the negative current increases from below 4 pA in the insulation state to above 10 mA, with a conduction change spanning more than 7 orders of magnitude. In particular, the comparative device maintained the nonlinear rectification characteristics of the PN junction throughout the entire test process, while the device of this application was able to achieve the transition from the rectified state to the linear ohmic contact state by adjusting the applied voltage. This indicates that the synergistic effect of the sidewall structure and the two-dimensional electron gas at the interface significantly enhances the continuous transport capability of the interface carriers, enabling the device to break through the limitation of traditional planar ferroelectric structures that can only maintain rectified transport, and realize stable and adjustable multi-state transport and linear conduction behavior.

[0038] The above results show that this application not only improves the conductivity of the device, but more importantly, it realizes the adjustable transition from "rectified state to linear ohmic state" which is difficult to achieve in traditional ferroelectric devices, providing a new realization path for multi-state logic devices, reconfigurable electronic devices and novel in-memory computing devices.

[0039] Example 3

[0040] By combining the two-dimensional electron domain wall conductive device prepared in Example 2 with a neuromorphic computational model, a synaptic-like functional device can be constructed. Continuous changes in the conductive state can be achieved by adjusting the applied voltage, thereby simulating the synaptic weight update process and supporting multi-value storage and reconfigurable computation at the hardware level.

[0041] First, a device array structure (10×10 array) is constructed and electrically trained. During training, an external voltage (30V) is applied to establish and modulate the conductive channels, and feature extraction and weight mapping are performed on the input signal. After repeated training, the device can perform information processing and pattern recognition through a forward electrical signal. Because the two-dimensional electron gas on the sidewalls provides a stable source of charge carriers, and the domain wall conductive channels have spatial controllability, this system exhibits excellent performance in terms of computational speed, energy efficiency, and stability, and can be applied to fields such as multi-value storage, reconfigurable logic circuits, and intelligent information processing.

[0042] Based on the coupling mechanism between the two-dimensional electron gas at the BaTiO3 / SrTiO3 interface and the ferroelectric domain walls, the device of this invention can achieve adjustable operation across multiple conduction states, including insulating, rectified, and linearly conducting states. Compared to traditional single-conductivity-mode devices, this significantly improves information carrying capacity and functional integration, providing a hardware foundation for multi-value storage and complex logic. By constructing a two-dimensional electron gas at the interface as a stable electron source, the uncertainty caused by relying on random defects (such as oxygen vacancy migration and aggregation) is avoided, fundamentally improving the device's conductivity consistency, cycle stability, and long-term operational reliability. Utilizing the efficient control of charge carriers by the local electric field of the ferroelectric domain walls, conduction state switching can be achieved at lower driving voltages, effectively reducing energy consumption while ensuring fast response, meeting the needs of next-generation low-power electronic devices. Relying on the natural nanoscale characteristics of the ferroelectric domain walls, the "on-demand generation" and spatially controllable modulation of conductive channels are realized, which is beneficial for device miniaturization and high-density integration, providing a path for ultra-high integration electronic systems. The device possesses reversible controllability with a "write-erase-rewrite" capability: under time relaxation or thermal excitation (such as near the Curie temperature), the conductive path can be shut down and restored to an insulating state, and can be reconstructed after repolarization. This characteristic enables the device to combine non-volatile storage and dynamic reconfiguration capabilities, providing support for in-memory computing architectures.

[0043] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a two-dimensional electron gas with sidewalls, characterized in that, Includes the following steps: Step 1: Prepare BaTiO3 ferroelectric thin films on SrTiO3 substrates using epitaxial growth methods; Step 2: Fabricate source and drain electrodes using photolithography and magnetron sputtering; Step 3: The sidewall structure is formed by photolithography and ion bombardment, and a two-dimensional electron gas is induced to form at the BaTiO3 / SrTiO3 interface; Step four: Polarization of the BaTiO3 ferroelectric thin film is controlled by an external electric field to form conductive channels at the domain walls.

2. The preparation method according to claim 1, characterized in that, The specific process for preparing the BaTiO3 ferroelectric thin film in step one is as follows: S1-1, The SrTiO3 substrate is pretreated to form an atomically flat surface structure terminated by TiO2. S1-2, BaTiO3 thin film is epitaxially grown on SrTiO3 substrate using pulsed laser deposition method; S1-3, BaTiO3 films were annealed in an environment with an oxygen partial pressure of 0.5 atmospheres to obtain an atomically smooth surface and stable ferroelectric polarization characteristics.

3. The preparation method according to claim 1, characterized in that: The SrTiO3 substrate is a (001) oriented single crystal substrate, and the thickness of the BaTiO3 ferroelectric thin film is 5–150 nm.

4. The preparation method according to claim 1, characterized in that: In step two, the magnetron sputtering conditions are 5 × 10⁻⁶. -6 ~8×10 -6 Deposition was performed at mbar gas pressure and 50–100 W power for 3–10 minutes; the source and drain electrodes were gold electrodes.

5. The preparation method according to claim 1, characterized in that: In step three, a three-dimensional channel with a sidewall structure is formed by anisotropic etching; oxygen vacancies are introduced at the BaTiO3 / SrTiO3 interface by controlling the ion bombardment conditions, thereby forming a two-dimensional electron gas.

6. The preparation method according to claim 1, characterized in that: In step three, the ion bombardment uses Ar. + Ions, bombarded with energies of 0.5–5 keV and bombarded for 10–300 s.

7. The preparation method according to claim 1, characterized in that: In step four, the ferroelectric domain walls generate a local electric field, forming a potential well structure in the domain wall region, causing electrons in the two-dimensional electron gas to aggregate in a directional manner and form a conductive channel.

8. A conductive device comprising a two-dimensional electron gas on the sidewalls prepared by the method according to any one of claims 1-7, characterized in that, It includes an SrTiO3 substrate, a BaTiO3 ferroelectric thin film, and source / drain electrodes; wherein, a two-dimensional electron gas is formed at the BaTiO3 / SrTiO3 interface, and a conductive channel is formed in the domain wall region through sidewall structure and ferroelectric domain wall regulation.

9. The conductive device according to claim 8, characterized in that: The surface carrier concentration of the two-dimensional electron gas is 5 × 10⁻⁶. 12 ~2×10 13 cm -2 .

10. The application of the conductive device according to claim 8 or 9 in the fabrication of multi-valued storage devices, reconfigurable logic circuits, or neuromorphic computing devices.

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