Photoelectric logic gate

Abstract

The invention discloses a photoelectric logic gate, which relates to the technical field of photoelectric logic gates, and is characterized in that a Bi2Se3 film is arranged on a substrate, two metal electrodes are arranged on the Bi2Se3 film at intervals, the two metal electrodes are connected with current testing equipment, and a channel is formed between the two metal electrodes and the current testing equipment; the two metal electrodes are connected, current flowing through the two metal electrodes serves as output, optical signals with different illumination intensities smaller than 468nm irradiate a Bi2Se3 thin film of a channel part to form an OR logic gate or AND logic gate through modulation, and irradiation under different combination conditions of two groups of optical signals larger than 468nm serves as signal input; for an NOT logic gate or an NOR logic gate or an NAND logic gate, optical signals with different illumination intensities larger than 468nm can be modulated, and irradiation under different combination conditions of two groups of optical signals smaller than 468nm is used as signal input. The structure is simple, and integration of the multifunctional logic gate is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of photoelectric logic gates, and in particular to a photoelectric logic gate. Background Art

[0002] A logic gate is a basic physical unit in a digital circuit that performs a logical operation on an input circuit signal (0, 1) and produces a single binary output signal. Logic gates are usually made of pn diodes or metal oxide semiconductor field effect transistors (MOSFETs), which are the most important components of digital electronics. There are five basic logic gates corresponding to the basic logic operations: OR, AND, NOT, NOR, and NAND gates. It is usually necessary to combine several transistors or design a complex structure to obtain several logic gates on a device, and the preparation process is relatively difficult. In an era of explosive growth in information, existing electronic logic gates are gradually unable to meet the needs of large-scale data processing due to their low performance, and the development of new logic gates is imperative.

[0003] Optoelectronic logic gates (OELGs) are considered to be an important component of future integrated circuits and are expected to enable faster and more accurate information processing, thus attracting widespread attention. Common optoelectronic devices (such as silicon (Si), gallium nitride (GaN), gallium arsenide (GaAs), and indium gallium arsenide (InGaAs)) rely on positive photoconductivity (PPC), in which the conductivity of the material increases with increasing light intensity. In contrast, the decrease in the conductivity of the material with increasing light intensity is called negative photoconductivity (NPC), which has been reported in a variety of inorganic materials (doped silicon, two-dimensional materials), organic materials (graphene, carbon nanotubes), and hybrid organic-inorganic materials (halide perovskites).

[0004] At present, a back-to-back photodiode composed of MAPbI3 and FA is proposed. 0.5 MA 0.5 Pb 0.4 Sn 0.6 I3, which demonstrated for the first time five logic gates (AND, OR, NAND, NOR, and NOT gates) without applying a bias voltage. In addition, there are also studies proposing devices (ITO / PEDOT:PSS / MAPbI3 / PCBM / FA 0.5 MA 0.5 Pb 0.4 Sn 0.6I3 / Spiro-MeOTAD / Au), the device structure is more complex, which is very demanding in the preparation process. There are also studies that propose bidirectional photoresponsive carbon-based graphene / graphene (GDY / Gr), which exhibits positive and negative optical responses under negative and positive bias (-1mV, 1mV). Through the integrated preparation of Au / GDY / Gr / Au devices, optical logic gates AND, OR and XOR gates are realized.

[0005] However, in summary, existing logic gates require multiple layers of materials to produce bidirectional light responses in order to produce the five basic logic gates (OR, AND, NOT, NOR, and NAND), and the structure is very complex. Summary of the invention

[0006] Based on this, it is necessary to provide a photoelectric logic gate to address the above technical problems.

[0007] The present invention adopts the following technical solutions:

[0008] The present invention provides a photoelectric logic gate, comprising: a substrate, a Bi2Se3 film, and two metal electrodes;

[0009] The Bi2Se3 film is disposed on the substrate, the two metal electrodes are disposed on the Bi2Se3 film at intervals, a channel is formed between the two metal electrodes, the two metal electrodes are connected, and the current flowing through the two metal electrodes is used as output;

[0010] The Bi2Se3 thin film in the channel part between the two metal electrodes uses light signals with different illumination intensities less than 468nm as gate modulation signals to form an OR logic gate or an AND logic gate, and the Bi2Se3 thin film in the channel part is irradiated with different combinations of two groups of light signals greater than 468nm as signal input, and generates different current conditions flowing through the two metal electrodes based on the bipolar light response as output;

[0011] The Bi2Se3 thin film in the channel part between the two metal electrodes uses light signals greater than 468nm with different illumination intensities as gate modulation signals to form a NOT logic gate, a NOR logic gate or a NAND logic gate. The Bi2Se3 thin film in the channel part is irradiated with different combinations of two groups of light signals less than 468nm as signal input, and generates different current conditions flowing through the two metal electrodes as output based on the bipolar light response.

[0012] Optionally, the Bi2Se3 thin film in the channel portion between the two metal electrodes will generate two opposite response currents when irradiated by a light signal less than 468nm and a light signal greater than 468nm; wherein, when a light signal with a wavelength less than 468nm is used as input, the current value flowing through the two metal electrodes decreases; and when a light signal with a wavelength greater than 468nm is used as input, the current value flowing through the two metal electrodes increases.

[0013] Optionally, the Bi2Se3 film in the channel portion between the two metal electrodes is heated at 18.4 to 42.7 mW / cm 2 The 405nm ultraviolet light of the illumination intensity is used as the gate modulation signal to form an OR logic gate;

[0014] Two groups of 808nm near-infrared light with different combinations were used as signal input; the illumination intensity of 808nm near-infrared light was 0mW / cm 2 As a "0" logic signal input, the illumination intensity of 808nm near-infrared light is 30.5mW / cm 2 Input as a "1" logic signal.

[0015] Optionally, the Bi2Se3 film in the channel portion between the two metal electrodes is 42.8-54.3 mW / cm 2 The 405nm ultraviolet light of the illumination intensity is used as the gate modulation signal to form an AND logic gate;

[0016] Two groups of 808nm near-infrared light with different combinations were used as signal input; the illumination intensity of 808nm near-infrared light was 0mW / cm 2 As a "0" logic signal input, the illumination intensity of 808nm near-infrared light is 30.5mW / cm 2 Input as a "1" logic signal.

[0017] Optionally, the Bi2Se3 film in the channel portion between the two metal electrodes is 6.7-18.1 mW / cm 2 The 808nm near-infrared light of the illumination intensity is used as the gate modulation signal to form a NOT logic gate;

[0018] A set of different combinations of 405nm ultraviolet light is used as the signal input; among them, the 405nm ultraviolet light illumination intensity is 0mW / cm 2 As a "0" logic signal input, the intensity of 405nm ultraviolet light illumination is 23.6mW / cm 2 Input as a "1" logic signal.

[0019] Optionally, the Bi2Se3 film in the channel portion between the two metal electrodes is 6.7-18.1 mW / cm2 The 808nm near-infrared light of the illumination intensity is used as the gate modulation signal to form a NOR logic gate;

[0020] Two groups of 405nm ultraviolet light with different combinations were used as signal input; the 405nm ultraviolet light illumination intensity was 0mW / cm 2 As a "0" logic signal input, the intensity of 405nm ultraviolet light illumination is 23.6mW / cm 2 Input as a "1" logic signal.

[0021] Optionally, the Bi2Se3 film in the channel portion between the two metal electrodes is heated at 18.2 to 34.7 mW / cm 2 The 808nm near-infrared light of the illumination intensity is used as the gate modulation signal to form a NAND logic gate;

[0022] Two groups of 405nm ultraviolet light with different combinations were used as signal input; the 405nm ultraviolet light illumination intensity was 0mW / cm 2 As a "0" logic signal input, the intensity of 405nm ultraviolet light illumination is 23.6mW / cm 2 Input as a "1" logic signal.

[0023] Optionally, the substrate is a transparent substrate;

[0024] The Bi2Se3 thin film in the channel portion between the two metal electrodes receives top incidence / bottom incidence of an optical signal smaller than 468 nm or an optical signal larger than 468 nm from the metal electrode side / substrate side.

[0025] At least one of the above technical solutions adopted by the present invention can achieve the following beneficial effects:

[0026] The photoelectric logic gate of the present invention includes a substrate, a Bi2Se3 film, and two metal electrodes, wherein the Bi2Se3 film is arranged on the substrate, and the two metal electrodes are arranged on the Bi2Se3 film at intervals, a channel is formed between the two metal electrodes, the two metal electrodes are connected and the current flowing through the two metal electrodes is used as the output. In application, the Bi2Se3 film in the channel part is modulated by irradiating light signals less than 468nm with different illumination intensities to form an OR logic gate or an AND logic gate, and irradiating with different combinations of two groups of light signals greater than 468nm as signal input, so that it can generate different current conditions flowing through the two metal electrodes based on the bipolar light response as output; for a NOT logic gate, a NOR logic gate, or a NAND logic gate, it can be modulated by light signals greater than 468nm with different illumination intensities, and irradiated with different combinations of two groups of light signals less than 468nm as signal input.

[0027] The present invention forms a photoelectric logic gate based on a Bi2Se3 thin film. The Bi2Se3 thin film has both positive and negative photoconductivity under external light of different wavelengths. Based on this, different photoelectric logic gates are formed by modulating external light of different wavelengths. The structure is simple and the integration of multifunctional logic gates is realized. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0029] Figure 1a A schematic diagram of a photoelectric logic gate provided by the present invention;

[0030] Figure 1b A schematic diagram of an application of a photoelectric logic gate provided by the present invention;

[0031] Figure 2 A schematic diagram of the preparation of a Bi2Se3 photoconductive detector provided by the present invention;

[0032] Figure 3 A schematic diagram of the atomic structure of Bi2Se3 provided by the present invention;

[0033] Figure 4 A schematic diagram of the XPS spectrum of Bi2Se3 provided by the present invention;

[0034] Figure 5 A schematic diagram of UV-Vis-NIR spectrum analysis results provided by the present invention;

[0035] Figure 6 A schematic diagram of positive and negative photoconductivity observed in a Bi2Se3 device provided by the present invention;

[0036] Figure 7 A schematic diagram of the absorption spectrum of Bi2Se3 provided by the present invention;

[0037] Figure 8 A schematic diagram of the stability of a device provided by the present invention under 808nm and 405nm light;

[0038] Fig. 9 A schematic diagram of the response time of a device under 808nm and 405nm light provided by the present invention;

[0039] Fig.10 A schematic diagram of the corresponding mechanism of the light response behavior under different laser irradiation provided by the present invention;

[0040] Fig.11A schematic diagram of the atomic structure of Bi2Se3 provided by the present invention;

[0041] Fig.12 A schematic diagram of a transmission characteristic curve of a device provided by the present invention;

[0042] Fig.13 A schematic diagram of measuring photocurrent after ultraviolet treatment for 30 minutes in vacuum and then re-exposing to the environment provided by the present invention;

[0043] Fig.14 A schematic diagram of the relationship between a response rate and illumination intensity provided by the present invention;

[0044] Fig.15 A schematic diagram of implementing five basic logic gates by a single device provided by the present invention;

[0045] Fig.16 A schematic diagram of logic gate operation of a PD array provided by the present invention;

[0046] Fig.17 A schematic diagram of an optical imaging platform provided by the present invention;

[0047] Fig.18 A schematic diagram of an optical imaging platform provided by the present invention;

[0048] Fig.19 A 405nm and 532nm 5 logic gate operation provided by the present invention;

[0049] Fig. 20 A schematic diagram of image pixel processing based on logic gates provided by the present invention;

[0050] Fig.21 A schematic diagram of obtaining a random key provided by the present invention;

[0051] Fig. 22 A schematic diagram of encryption and decryption provided by the present invention;

[0052] Fig.23 A schematic diagram of an encryption process and a decryption process provided by the present invention. DETAILED DESCRIPTION

[0053] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the specific embodiments of the present invention and the corresponding drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0054] At present, nanoscale silicon-based devices are affected by short-channel effects such as quantum tunneling, which leads to serious performance degradation as the size of transistors continues to shrink. Traditional CMOS technology, which relies on shrinking size to increase integration density, is facing severe challenges. In order to overcome the limitations of silicon materials and promote the development of the post-Moore era, two-dimensional materials with atomic-level thickness have attracted widespread attention. On the one hand, two-dimensional materials still show good carrier mobility and gating performance at nanometer size; on the other hand, two-dimensional materials can be non-uniformly integrated with other semiconductor materials such as silicon, perovskite, and organic, and have good compatibility; in addition, two-dimensional materials also have excellent specific surface area, surface activity and optoelectronic properties, and have outstanding potential in the fields of sensing, new optoelectronic devices, etc. In summary, two-dimensional materials have broad prospects in promoting Moore's Law to more Moore, more than Moore, and beyond Moore, and provide opportunities to overcome the limitations of current silicon-based devices and promote the limitations of microelectronics technology.

[0055] Materials with both positive and negative photoconductivity can easily achieve bidirectional photocurrent response by simply switching the incident light of different wavelengths. In recent years, wavelength-dependent bidirectional photodetectors based on heterostructure design have been studied, such as Bi2O2Se / graphene hybrid structure, Pyr-GDY / Gr / PbS-QD, graphene / C 60 / pentacene heterojunction, AlGaN / GaN, and PtSe 2-x At the same time, the devices can be fabricated on flexible substrates, which means they have broad development prospects in multifunctional and flexible platforms such as wearable devices.

[0056] This paper proposes a multifunctional logic gate based on a two-dimensional material photodetector. The two-dimensional material Bi2Se3 has both positive and negative photoresponse behaviors under external light of different wavelengths. The polarity of the photocurrent can be achieved by co-modulating the light signal less than 468nm and the light signal greater than 468nm, and the signal output of five logic gates (OR, AND, NOT, NOR and NAND) is realized in one photodetector. In practical applications, an 8×8 logic gate array example is proposed, the reproducibility of the photoelectric logic gate is verified, and some exploratory work is carried out on its imaging and image logic processing.

[0057] The technical solutions provided by various embodiments of the present invention are described in detail below in conjunction with the accompanying drawings.

[0058] Fig. 1 is a schematic diagram of a photoelectric logic gate in the present invention. As can be seen from Fig. 1, the photoelectric logic gate includes: a substrate, a Bi2Se3 film, and two metal electrodes.

[0059] The Bi2Se3 film is arranged on the substrate, two metal electrodes are arranged on the Bi2Se3 film at intervals, a channel is formed between the two metal electrodes, the two metal electrodes are connected, and the current flowing through the two metal electrodes is used as output.

[0060] Among them, the Bi2Se3 film in the channel part between the two metal electrodes uses light signals less than 468nm with different illumination intensities as gate modulation signals to form an OR logic gate or an AND logic gate. The Bi2Se3 film in the channel part is irradiated with different combinations of two groups of light signals greater than 468nm as signal input, and generates different current conditions flowing through the two metal electrodes based on the bipolar light response as output.

[0061] The Bi2Se3 thin film in the channel part between the two metal electrodes uses light signals with different illumination intensities greater than 468nm as gate modulation signals to form a NOT logic gate, a NOR logic gate or a NAND logic gate. The Bi2Se3 thin film in the channel part is irradiated with different combinations of two groups of light signals less than 468nm as signal input, and generates different current conditions flowing through the two metal electrodes as output based on the bipolar light response.

[0062] Furthermore, in one or more embodiments of the present invention, the Bi2Se3 thin film in the channel portion between the two metal electrodes will generate two opposite response currents when being irradiated by a light signal with a wavelength less than 468nm and a light signal with a wavelength greater than 468nm; wherein, when a light signal with a wavelength less than 468nm is used as input, the current value flowing through the two metal electrodes decreases; and when a light signal with a wavelength greater than 468nm is used as input, the current value flowing through the two metal electrodes increases.

[0063] In one or more embodiments of the present invention, when different combinations of 808 nm near-infrared light are used as signal input, the illumination intensity of 808 nm near-infrared light is 0 mW / cm 2 As a "0" logic signal input, the illumination intensity of 808nm near-infrared light is 30.5mW / cm 2 As a "1" logic signal input. When irradiated with different combinations of 405nm ultraviolet light as signal input, the 405nm ultraviolet light illumination intensity can be 0mW / cm 2 As a "0" logic signal input, the intensity of 405nm ultraviolet light illumination is 23.6mW / cm 2 Input as a "1" logic signal.

[0064] Figure 1bThis is a schematic diagram of an application of a photoelectric logic gate in the present invention. In one or more embodiments of the present invention, the substrate may be a transparent substrate, and the Bi2Se3 thin film in the channel portion between the two metal electrodes may receive a light signal less than 468nm or a light signal greater than 468nm from the top incident from the metal electrode side; or, the Bi2Se3 thin film in the channel portion between the two metal electrodes may receive a light signal less than 468nm or a light signal greater than 468nm from the bottom incident from the substrate side.

[0065] Figure 1b Taking top incidence as an example, four external lasers can be used to irradiate the channel Bi2Se3 film in different conditions to modulate the optoelectronic logic gate.

[0066] In one or more embodiments of the present invention, the Bi2Se3 film in the channel portion between the two metal electrodes is 18.4-42.7 mW / cm 2 The 405nm ultraviolet light with high illumination intensity is used as the gate modulation signal to form an OR logic gate. At this time, different combinations of two 808nm near-infrared lights can be used as signal input.

[0067] In one or more embodiments of the present invention, the Bi2Se3 film in the channel portion between the two metal electrodes is 42.8-54.3 mW / cm 2 The 405nm ultraviolet light with high illumination intensity is used as the gate modulation signal to form an AND logic gate. At this time, different combinations of two 808nm near-infrared lights can be used as signal input.

[0068] In one or more embodiments of the present invention, the Bi2Se3 film in the channel portion between the two metal electrodes is 6.7-18.1 mW / cm 2 The 808nm near-infrared light with high illumination intensity is used as the gate modulation signal to form a NOT logic gate. At this time, different combinations of 405nm ultraviolet light can be used as signal input, and the other ultraviolet laser can be disabled.

[0069] In one or more embodiments of the present invention, the Bi2Se3 film in the channel portion between the two metal electrodes is 6.7-18.1 mW / cm 22 The 808nm near-infrared light with high illumination intensity is used as the gate modulation signal to form a NOR logic gate. At this time, different combinations of two 405nm ultraviolet lights can be used as signal input.

[0070] In one or more embodiments of the present invention, the Bi2Se3 film in the channel portion between the two metal electrodes is 18.2 to 34.7 mW / cm 2The 808nm near-infrared light with high illumination intensity is used as the gate modulation signal to form a NAND logic gate. At this time, two different combinations of 405nm ultraviolet light can be used as signal input. The output of the photoelectric logic gate obtained by using 405nm ultraviolet light and 808nm near-infrared light as the gate modulation signal or optical signal input is more stable.

[0071] In one or more embodiments of the present invention, the photoelectric logic gate can be considered to be made based on a Bi2Se3 photoconductive detector. In order to analyze the bipolar photoresponse behavior of a small number of layers of Bi2Se3 thin films, a low-pressure chemical vapor deposition method can be used to prepare the thin film, such as Figure 2 As shown, Figure 2 It is one of the present invention. Figure 2 Part (a) shows the preparation of Bi2Se3 on sapphire by CVD: Bi2Se3 thin films were synthesized using a low-pressure vapor deposition furnace and a horizontal quartz tube. The quartz tube was evacuated and flushed with pure argon to provide an oxygen-free environment. Se and Bi2O3 powders were placed as precursors in the center region and upstream of the chamber, respectively. Using argon and hydrogen as growth carrier gases, the evaporated precursors were transported to the downstream sapphire growth substrate. The sapphire substrate was a 0.3 mm thick c-axis sapphire (dimensions 1 cm × 1 cm), suitable for promoting lateral 2D growth, and was placed 5 cm below Bi2O3. The growth environment conditions were as follows. The temperature of the selenium source was 300 °C, 700 °C in the center, and 500 °C on the substrate. The system pressure was 100 Torr, the argon flow rate was 200 sccm, and the hydrogen was 15 sccm. The growth time was 15 min. After deposition, the furnace was cooled to room temperature and the quartz tube was refilled with argon to atmospheric pressure.

[0072] Figure 2 Part b and Figure 2 The AFM scan of part c shows the 2D and 3D morphologies. The thickness of the Bi2Se3 film is 4.998nm ( Figure 2 Part d), according to the five-layer theory (thickness ≈ 0.998 nm), the thickness of the film is about 5 layers, such as Figure 3 As shown, Figure 3 Schematic diagram of the atomic structure of Bi2Se3 in the present invention.

[0073] In Raman spectroscopy ( Figure 2 In the e part of Bi2Se3, E g Peak and A 1g The peaks are located at 132.5 cm -1 and 175.1cm -1 This is consistent with previous reports. Figure 2 In part f, B i2 Se3 thin film shows The phase structure with consistent space group is shown by the (00L) (L=3, 6, 9, 12, 15) diffraction peak along the c-axis in the X-ray diffraction diagram. Figure 2 As shown in part g, the rocking curve of the (006) plane shows a half-maximum width (FWHM) of 0.571°, indicating that the crystal has a high crystalline quality. Figure 2 The illustration in part g is a photo of a Bi2Se3 thin film, which has a smooth and flat surface and metallic luster. X-ray photoelectron spectroscopy (XPS) tests were also performed, such as Figure 4 As shown, Figure 4 This is a schematic diagram of the XPS spectrum of Bi2Se3 in the present invention.

[0074] The binding energy peaks of Bi 4f are located at 163.41 and 158.02 eV respectively. The binding energy peaks of Se 3d are 54.32 eV and 53.51 eV respectively. The atomic percentage of Se / Bi is 1.496, indicating that the composition of the prepared film is accurate. The UV-Vis-NIR spectral analysis results are shown in Figure 5 As shown, it can be seen that the Bi2Se3 layer has good light absorption ability at a wavelength of 300-1000nm.

[0075] The present invention also prepares a photoconductive device to study the bipolar photoresponse behavior of the Bi2Se3 photodetector. The schematic diagram and simplified circuit are shown in Figure 6 As shown, Figure 6 Schematic diagram of positive and negative photoconductivity observed in a Bi2Se3 device in the present invention. Figure 6 Part a shows the gold contacts made using vacuum evaporation technology (patterned Au electrodes (280 nm) are plated on the Bi2Se3 film. The channel width between the gold electrodes is 100 μm and the length is 1 mm. The vacuum evaporation condition is 5 mPa).

[0076] The Bi2Se3 photodetector exhibits bipolar photoresponse behavior, positive photoconductivity, and negative photoconductivity under illumination at wavelengths of 355nm, 375nm, 405nm, 532nm, 808nm, and 1064nm, e.g. Figure 6 As shown in part b of the figure. Positive photoconductivity (PPC) is usually caused by illumination, which leads to an increase in the conductivity of the semiconductor due to the excitation of more charges from the valence band to the conduction band. In contrast, negative photoconductivity (NPC) refers to the decrease in the conductivity of the semiconductor under illumination. Figure 6 Part c shows the device in the dark, 405 and 808nm (power density 30mW / cm 2 ) at an open circuit voltage of 0.11, 0.51 and -0.12 mV, respectively, and the dark current and bipolar photoresponse current (405 and 808 nm).

[0077] Under 808nm illumination, the measured 2 The photoresponse of the Bi2Se3 device under different illumination intensities. Figure 6 As shown in part d, the photocurrent increases with the increase of light intensity, indicating the existence of PPC behavior. Figure 6 As shown in part e, under 405nm illumination, the current decay of the device changes with the light intensity from 1.5 to 64.1mW / cm 2 The continuous operation stability of the device is shown in Figure 2. Figure 7 As shown, Figure 7 The figure is a schematic diagram of the absorption spectrum of Bi2Se3 in the present invention. The rise (fall) time of the device is defined as the time interval for the current to increase from 10% to 90% (from 90% to 10%) of the final value. Under pulse illumination of 808nm and 405nm, the rise (fall) time is 352 / 314ms and 397 / 431ms respectively. Figure 8 and Fig. 9 As shown, Figure 8 Schematic diagram of the stability of a device under 808nm and 405nm light in the present invention, Fig. 9 The following is a schematic diagram of the response time of a device under 808nm and 405nm illumination in the present invention. Under 405nm illumination, the current decrease and recovery trends are slower, which can be attributed to the desorption and adsorption process of oxygen molecules on the surface.

[0078] Among them, the abundant surface selenium defects in Bi2Se3 play a key role in the mechanism of wavelength-selective bipolar photoresponse behavior. Under short-wavelength laser irradiation, the desorption of oxygen molecules near selenium vacancies leads to the NPC behavior of two-dimensional metal selenide materials. Fig. 9 A schematic diagram of the mechanism of a wavelength-selective bipolar light response behavior in the present invention.

[0079] The corresponding mechanisms of the photoresponse behaviors under different laser irradiation are as follows Fig.10 As shown in Figure 1, where part a is the free electrons from Bi2Se3 under dark conditions are attracted by the adsorbed oxygen molecules, leaving holes inside the material. Under short-wavelength laser irradiation, the desorption process of oxygen molecules is greatly accelerated. Electrons are transferred from oxygen molecules to Bi2Se3 and recombine with holes. The conductivity of the material decreases, resulting in NPC behavior. The energy barrier for the desorption of O2 molecules was simulated using the density functional theory (DFT) method, as shown in Figure 1. Fig.11 , Fig.12 and Fig.13 shown.

[0080] Fig.11This is a schematic diagram of the atomic structure of Bi2Se3 in the present invention, wherein part a corresponds to no defects and part b corresponds to a selenium defect. Fig.12 It is a schematic diagram of a transmission characteristic curve of a device in the present invention. Fig.13 This is a schematic diagram of measuring the photocurrent after ultraviolet treatment in a vacuum for 30 minutes and then re-exposure to the environment according to the present invention.

[0081] The binding energy of chemically adsorbed O2 molecules on two layers of Bi2Se3 is calculated to be -2.702eV, with photon energies between 1.53eV (808nm laser) and 3.06eV (405nm laser), providing evidence that the oxygen desorption bipolar reaction is self-consistent. In addition, Fig.10 Parts b, c, and d show that the removal of O2 molecules exposes selenium vacancies in Bi2Se3. These vacancies generate localized states close to the conduction band, increasing the n-doping effect and raising the Fermi level (E f ). Therefore, it can be concluded that illumination with different photon energies controls the adsorption / desorption process of intrinsic Se vacancies and O2 molecules, leading to the wavelength-selective bipolar photoresponse behavior of Bi2Se3 with good reproducibility. In addition, this behavior can also be observed in Bi2Se3 devices on Si / SiO2 substrates, and the transfer curves generated by the mutual conversion of p-type and n-type behaviors are observed, which provides broad prospects for the development of controllable multimodal transistor devices. As shown in Table 1:

[0082] Table 1 Calculated binding energy of selenium defects and oxygen molecules

[0083]

[0084] All calculations were performed in the density functional theory framework using the projector-augmented plane wave method with a plane wave cutoff energy set to 450 eV. In the iterative solution of the Kohn–Sham equation, the energy criterion was set to 10 -5 eV. To avoid mirror interaction, a A 2×2×1 supercell structure of two layers of Bi2Se3 was then constructed, and a Se vacancy was introduced on the surface to study the adsorption of O2. The Brillouin zone integration was performed using a 3×3×1 k-path. All structures were relaxed until the residual forces on the atoms dropped to less than

[0085] UV irradiation can significantly reduce oxidation-related defects caused by desorption of surface absorbing molecules on two-dimensional materials. It is expected that long-term exposure of defective Bi2Se3 films to 375nm UV light (photon energy = 3.31eV, power = 600mW / cm2) in a vacuum environment will reduce the oxidation-related defects caused by desorption of surface absorbing molecules on two-dimensional materials. 2) can change the photoresponse behavior of the device. On this basis, the photoresponse of UV-treated Bi2Se3 in a vacuum environment was compared with that of untreated Bi2Se3 in ambient conditions.

[0086] Fig.13 It was shown that the Bi2Se3 device exhibited NPC behavior when exposed to 355nm, 375nm, and 405nm illumination under ambient conditions. After UV treatment in a vacuum environment for 30 minutes, the device showed PPC behavior. When the vacuum UV-treated device was exposed to ambient conditions again for 15 minutes, the negative photoreaction behavior reappeared. The above experiments and DFT confirmed that NPC in Bi2Se3 films is due to the adsorption and desorption of oxygen molecules at Se vacancies.

[0087] In characterizing the photoresponse of Bi2Se3 detectors, two important performance parameters of photodetectors are the responsivity (R) and the specific detectivity (D * ). The responsivity (R) measures the photocurrent generated per unit area per incident illumination, and the R of a photodetector can be obtained by the following equation:

[0088]

[0089] In the formula, I ph is the photocurrent, which is the total current observed by the Bi2Se3 detector under illumination, I dark is the current measured in the dark, P is the illumination intensity, and S is the effective area (0.9×10 -2 cm 2 ), I illuminated is the current intensity of the Bi2Se3 detector when it is illuminated by light, I dark is the current intensity of the Bi2Se3 detector under dark conditions.

[0090] Fig.14 This is a schematic diagram of the relationship between the response rate and the illumination intensity in the present invention. When the density of 405nm illumination is 0.5mW / cm 2 When the density of 808nm illumination is 7mW / cm 2 When the density increases, the responsivity increases and remains at 0.0047A / W. When the light intensity increases, the photodetector has a lower responsivity to the increasing number of photoexcited carrier complexes.

[0091] In addition, the specific detectivity D of the proposed photodetector can be calculated according to the following formula: * :

[0092]

[0093] Where e is the charge.

[0094] Depend on Fig.14 It can be seen that D * It also decreases with the increase of light intensity, with -2.9×10 8 and 1.87×10 7 Jones(1Jones=1cmHz 1 / 2 W -1 ). In the absence of bias voltage, the above response rate (R) and specific detection rate (D) were calculated. * ) measurement value.

[0095] The present invention also provides demonstration examples of five basic logic gates. In order to demonstrate the multifunctional logic gates using only one bipolar photodetector, the key is two incident light signals that need to be illuminated at different wavelengths and intensities, and they have opposite light response behaviors.

[0096] This embodiment is based on the bipolar photoresponse behavior of the coexistence of positive and negative photoconductivity in the Bi2Se3 photodetector, 405 and 808 nm illumination are selected as optical signals and gate modulators to operate logic gates, and five basic logic gates ("OR", "AND", "NOT", "NAND" and "NOR") can be modulated in one device.

[0097] After receiving laser irradiation, the semiconductor material in the channel of the photoelectric logic gate can transmit the current model to the test system through the gold electrode. Among them, when 405nm ultraviolet light is used as a gate modulator and 808nm near-infrared light is used as a signal input, the modulation of "OR" and "AND" logic gates can be realized.

[0098] 808nm near-infrared light is used as the gate modulator, and 405nm ultraviolet light is used as the signal input to realize the modulation of "NOR", "NAND" and "NOT" logic gates, such as Fig.15 As shown, Fig.15 It is a schematic diagram of realizing five basic logic gates by a single device in the present invention. Fig.15 Part b is the modulation of the five logic gates of the two wavelengths of light corresponding to the truth table, where “0” and “1” represent the input optical signal “off” and “on” and the level of the output signal.

[0099] The switching between the "OR" and "AND" gates depends on the change in 405nm illumination intensity, which can be referred to Fig.15 The middle c part corresponds to 18.4 to 42.7 mW / cm 2 and 42.8~54.3mW / cm 2 . Fig.15 Parts d and e show the transient photocurrent of the "OR" gate and the "AND" logic gate when the input light signal ("00", "01", "10", "11") is applied. The "0", "1" input signal corresponds to 0mW / cm 2 , 30.5mW / cm 2 The 808nm input light of the OR gate and the 405nm light of the AND gate are 23.6mW / cm 2 and 48.8mW / cm 2 The switching between the "NOR" ("NOT") and "NAND" gates depends on the change in the intensity of the 808nm illumination ( Fig.15 f part), corresponding to 6.7~18.1mW / cm 2 and 18.2~34.7mW / cm 2 . Fig.15 Part g in the middle shows the “NOT” gate at the signals (“0” and “1”). Fig.15 Parts h and i show the transient photocurrents of the "NOR" and "NAND" gates when the input light signals ("00", "01", "10", "11") are applied. For the "NOR" ("NOT") and "NAND" gates, the "0" and "1" input signals are 0 mW / cm2 of 405 nm input light. 2 and 23.6mW / cm 2 , gate light is 808nm (9.5 to 19.5mW / cm 2 ).

[0100] The present invention also provides a demonstration example of Bi2Se3 detector pixel array, such as Fig.16 As shown, Fig.16 It is a schematic diagram of the logic gate operation of a PD array in the present invention.

[0101] In order to realize the practical application of the prepared Bi2Se3 logic gates, an integrated logic gate 8×8 array was built and the accuracy of its operation was explored. Fig.16 Part a in the middle is a schematic diagram of an 8×8 array prepared by sandwiching a Bi2Se3 thin film between a gold electrode and a sapphire substrate. Eight channels are formed between the nine Au electrodes, with a channel length of 100 μm and an electrode width of 0.9 mm. Fig.16 As shown in part b, the currents of 64 pixels are obtained by reading the channel current point by point.

[0102] Fig.17 is a schematic diagram of an optical imaging platform in the present invention, Fig.18This is a schematic diagram of an optical imaging platform in the present invention. The incident laser in the test system is collimated and expanded by the beam expansion system to evenly expand the light spot and cover the entire array. During the test, the current data of 64 pixels were collected. The results are as follows: Fig.16 As shown in part c. Red and purple represent positive and negative photocurrents, respectively, and gray represents the baseline level of 0nA. All pixels maintain 100% accuracy in all five logic operations. Similarly, 5 logic gate operations were successfully modulated using 405nm and 532nm light, as shown in Figure 2. Fig.19 As shown, Fig.19 This is a 5-logic gate operation at 405nm and 532nm in the present invention.

[0103] The present invention also provides an example of logical processing of an image, such as Fig. 20 As shown, Fig. 20 The figure is a schematic diagram of image pixel processing based on logic gates in the present invention.

[0104] The implementation of five basic logic gates on the array demonstrates the device’s ability to act as an image processing unit. The “OR” logic gate is an example of an image processing workflow, and the other logic gates work similarly. Fig. 20 As shown in part a, the incident light on the Bi2Se3 array is illuminated through a mask with a specific pattern, and the light illumination of the input light signal is 1, and the no light illumination is 0. The threshold current 0nA is used to distinguish between the output signals 1 and 0. Two different test image inputs 1 and 2 can be processed by logic or get a complete image output, performing various logic functions ("OR", "AND", "NOR (NOT)" and "NAND"). Different output results can be achieved, such as Fig. 20 As shown in part b.

[0105] In addition, the present invention also provides a simple data encryption method based on XOR encryption. By using the reversibility of the XOR operation, the image encryption and decryption process is as follows: Fig. 20 As shown in part c. First, use the Matlab program to generate a random 8×8 binary matrix as a random key, as shown in Fig.21 As shown, Fig.21 A schematic diagram of obtaining a random key in the present invention.

[0106] The encryption process is achieved by performing an XOR operation on the original image and the random key. The original image is incident from 405nm (808nm) light, and the random key is incident from 808nm (405nm) light. The encrypted image is obtained through the XOR logic operation. In addition, the encrypted image is incident from 405nm (808nm) light, and the random key is incident from 808nm (405nm) light. The decrypted image is obtained through the XOR logic operation, such as Fig. 22As shown, Fig. 22 This is a schematic diagram of encryption and decryption in the present invention. The current test data of all images involved in the above process is as follows: Fig.23 As shown, Fig.23 The figure is a schematic diagram of an encryption process and a decryption process in the present invention.

[0107] In one or more embodiments of the present invention, the material and device characterization tests used a microscope to observe the optical image of the Bi2Se3 photodetector array. The surface morphology and thickness of the Bi2Se3 film were measured using an atomic force microscope. The Raman spectrum of the Bi2Se3 film was characterized using a 532nm laser (DXR confocal microscopy Raman system, Thermo Fisher). The crystal structure of Bi2Se3 between 5° and 55° was characterized using XRD (D8ADVANCE X-ray diffractometer, Bruker), with a scanning step (2θ) of 0.02°. XPS measurements were performed using a Scale XL analysis system connected to a monochromatic Al X-ray source.

[0108] The conditions for the spot measurements were ambient temperature and 50% humidity. The optoelectronic data of the device were measured using a digital source meter. The response time of the device was measured using an oscilloscope with a pulse source. The synaptic plasticity was studied using an input laser beam and a modulated laser beam. The response time of the device was measured by an oscilloscope with a pulse source, and the rise and fall time process from 10% to 90% was defined as the device's τ on and τ off .

[0109] The present invention provides a multifunctional logic gate based on a two-dimensional material Bi2Se3 photodetector. The two-dimensional material Bi2Se3 has both positive and negative photoconductivity under external light of different wavelengths. The polarity of the photocurrent can be achieved by co-modulation of ultraviolet (405nm) and NIR (808nm) light, and the signal output of five logic gates (OR, AND, NOT, NOR and NAND) is realized in a single photodetector. The "0" and "1" signal outputs are defined by negative photocurrent or positive photocurrent, respectively, and do not rely on traditional reference levels, which greatly improves the accuracy and stability of the logic gate. The photoelectric logic gate system achieves 100% in repeated stability tests. In practical applications, an 8×8 logic gate array was constructed as an example to verify the repeatability of the photoelectric logic gate, and some exploratory work was done in image imaging and logic processing. The single-layer two-dimensional material photodetector constitutes a logic gate, which has a very simple structure compared to existing photoelectric logic gate devices, greatly simplifies the processing process, and controls the cost. Multiple logic gates can be implemented in one device, which is more space- and cost-efficient than logic circuits composed of traditional electronic transistors in integrated chips. It has broad potential in future optical communications, all-optical computers, and optoelectronic storage devices. This work not only constructs optoelectronic logic gates, but also provides a reliable solution for the development of future multifunctional image processing units.

[0110] It should also be noted that the terms “comprises”, “includes” or any other variations thereof in the present invention are intended to cover non-exclusive inclusion, that is, in addition to the elements listed in the present invention, other elements not explicitly listed may also be included.

[0111] The various embodiments of the present invention are described in a progressive manner, and the same or similar parts between the various embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments.

[0112] The above description is only an embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent substitution, improvement, etc. made within the spirit and principle of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A photoelectric logic gate, characterized in that: include: Substrate, Bi2Se3 thin film, two metal electrodes; The Bi2Se3 film is disposed on the substrate, the two metal electrodes are disposed on the Bi2Se3 film at intervals, a channel is formed between the two metal electrodes, the two metal electrodes are connected, and the current flowing through the two metal electrodes is used as output; The Bi2Se3 thin film in the channel part between the two metal electrodes uses light signals with different illumination intensities less than 468nm as gate modulation signals to form an OR logic gate or an AND logic gate, and the Bi2Se3 thin film in the channel part is irradiated with different combinations of two groups of light signals greater than 468nm as signal input, and generates different current conditions flowing through the two metal electrodes based on the bipolar light response as output; The Bi2Se3 thin film in the channel part between the two metal electrodes uses light signals greater than 468nm with different illumination intensities as gate modulation signals to form a NOT logic gate, a NOR logic gate or a NAND logic gate. The Bi2Se3 thin film in the channel part is irradiated with different combinations of two groups of light signals less than 468nm as signal input, and generates different current conditions flowing through the two metal electrodes as output based on the bipolar light response.

2. The multifunctional optoelectronic logic gate according to claim 1, characterized in that: When the Bi2Se3 thin film in the channel part between the two metal electrodes is irradiated by a light signal less than 468nm and a light signal greater than 468nm, two opposite response currents will be generated; wherein, when a light signal with a wavelength less than 468nm is used as input, the current value flowing through the two metal electrodes decreases; when a light signal with a wavelength greater than 468nm is used as input, the current value flowing through the two metal electrodes increases.

3. The optoelectronic logic gate according to claim 1, characterized in that The Bi2Se3 film in the channel between the two metal electrodes is 18.4-42.7 mW / cm 2 The 405nm ultraviolet light of the illumination intensity is used as the gate modulation signal to form an OR logic gate; Two groups of 808nm near-infrared light with different combinations were used as signal input; the illumination intensity of 808nm near-infrared light was 0mW / cm 2 As a "0" logic signal input, the illumination intensity of 808nm near-infrared light is 30.5mW / cm 2 Input as a "1" logic signal.

4. The optoelectronic logic gate according to claim 1, characterized in that: The Bi2Se3 film in the channel between the two metal electrodes is 42.8-54.3 mW / cm 2 The 405nm ultraviolet light of the illumination intensity is used as the gate modulation signal to form an AND logic gate; Two groups of 808nm near-infrared light with different combinations were used as signal input; the illumination intensity of 808nm near-infrared light was 0mW / cm 2 As a "0" logic signal input, the illumination intensity of 808nm near-infrared light is 30.5mW / cm 2 Input as a "1" logic signal.

5. The optoelectronic logic gate according to claim 1, characterized in that: The Bi2Se3 film in the channel between the two metal electrodes is 6.7-18.1 mW / cm 2 The 808nm near-infrared light of the illumination intensity is used as the gate modulation signal to form a NOT logic gate; A set of different combinations of 405nm ultraviolet light is used as the signal input; among them, the 405nm ultraviolet light illumination intensity is 0mW / cm 2 As a "0" logic signal input, the intensity of 405nm ultraviolet light illumination is 23.6mW / cm 2 Input as a "1" logic signal.

6. The optoelectronic logic gate according to claim 1, characterized in that: The Bi2Se3 film in the channel between the two metal electrodes is 6.7-18.1 mW / cm 2 The 808nm near-infrared light of the illumination intensity is used as the gate modulation signal to form a NOR logic gate; Two groups of 405nm ultraviolet light with different combinations were used as signal input; the 405nm ultraviolet light illumination intensity was 0mW / cm 2 As a "0" logic signal input, the intensity of 405nm ultraviolet light illumination is 23.6mW / cm 2 Input as a "1" logic signal.

7. The optoelectronic logic gate according to claim 1, characterized in that: The Bi2Se3 film in the channel between the two metal electrodes is 18.2-34.7 mW / cm 2 The 808nm near-infrared light of the illumination intensity is used as the gate modulation signal to form a NAND logic gate; Two groups of 405nm ultraviolet light with different combinations were used as signal input; the 405nm ultraviolet light illumination intensity was 0mW / cm 2 As a "0" logic signal input, the intensity of 405nm ultraviolet light illumination is 23.6mW / cm 2 Input as a "1" logic signal.

8. The optoelectronic logic gate according to claim 1, characterized in that: The substrate is a transparent substrate; The Bi2Se3 thin film in the channel portion between the two metal electrodes receives top incidence / bottom incidence of an optical signal smaller than 468 nm or an optical signal larger than 468 nm from the metal electrode side / substrate side.

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