Photoelectron synapse element having optical active layer containing quantum dot-transition metal dichalcogenide heterogeneous bonding

Abstract

To provide a photoelectron synapse element having an optical active layer indicating a neuromorphic feature as well as enabling an optical responce of an infrared wavelength in order to be a recognition of a correct event, and provide a manufacturing method of them.SOLUTION: A photoelectron synapse element comprises an optical active layer in which a heterogeneous bonding is formed by contacting an inorganic quantum dot with a transition metal dichalcogenide of a secondary semiconductor material indicating a synapse characteristic by a light stimulus. Thus, a synapse reaction in responce to an optical signal of a near infrared wavelength can be made. By realizing a visual-brain function toe function of a human indicating the neuromorphic feature by an optical responce (a visual reaction) of the infrared wavelength in a single element with an optical detection feature that it is sensitively reacted at a high speed in the infrared wavelength signal, it can be easily adopted in an autonomous traveling mobility field.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an optoelectronic synaptic device, and more particularly to an optoelectronic synaptic device comprising a photoactive layer including a quantum dot-transition metal dichalcogenide heterojunction.

Background Art

[0002] Efforts in research related to autonomous driving have been underway since the 1970s. Entering the 2010s, with the emergence of deep learning technology, the technology has been developing rapidly. After experiencing the severe period of the COVID-19 pandemic, the technology related to autonomous driving is developing at an even faster pace. In order to meet the "artificial intelligence" and "safety", which are the core technologies of the future smart mobility industry, the importance of an artificial neural network processing device equipped with a sensing element technology for recognizing lanes and obstacles in front of the vehicle and a neuromorphic technology for performing cognitive-perceptual-computational information processing simultaneously and in parallel like the neuron structure and operation of the human brain for performing ultra-high-speed information processing such as recognition / judgment / control / arithmetic has been maximized.

[0003] At present, the avoidance of mobility risk sources and the detection of risk sources in autonomous driving functions are carried out using optical signals (LiDAR; Light Detection and Ranging, detection and ranging by light) or electromagnetic waves (RADAR; Radio Detection and Ranging, detection and ranging by radio). However, although LiDAR is specialized in the 900 nm region based on InGaAs, there is a problem that the recognition rate decreases due to the overlap with visible light. Therefore, in order to avoid crosstalk by visible light in the normal atmospheric environment and for accurate recognition of things, the need for a photodetector element that is sensitive and responsive to infrared wavelength signals of 900 nm or more is increasing. Furthermore, in order to ensure the safety of passengers and luggage and to achieve stable autonomous operation, a series of processes such as risk recognition - calculation - judgment - response must be performed at ultra-high speed, and in order to improve the efficiency of driving the mobility system, there is a need for such a series of processes to be developed as a single element driven at low power.

Summary of the Invention

Problems to be Solved by the Invention

[0004] The present invention was created to solve the above-mentioned problems, and its purpose is to provide a optoelectronic synaptic element including a photoactive layer capable of infrared wavelength optical response for accurate recognition of things and exhibiting neuromorphic characteristics, and a manufacturing method thereof.

Means for Solving the Problems

[0005] In order to achieve the above object, an optoelectronic synaptic element according to a preferred embodiment of the present invention may be provided on a substrate, and may include a photoactive layer including an inorganic quantum dot and a two-dimensional semiconductor material, and a plurality of electrodes provided on the photoactive layer and arranged apart from each other.

[0006] The inorganic quantum dot and the two-dimensional semiconductor material may be in direct contact to form a heterojunction.

[0007] The wavelength of light that can be received in the photoactive layer may include the wavelength range of visible light to near-infrared light.

[0008] The two-dimensional semiconductor material may be a single layer or a multi-layer of two or more layers in a layered form.

[0009] The two-dimensional semiconductor material may include transition metal dichalcogenides.

[0010] The transition metal dichalcogenide is represented by the chemical formula MX 2 where M is a transition metal element and includes Mo, W, Nb, V, Ta, Ti, Zr, Hf, Tc, Re, Ru, Co, Pd, Pt, Cu, Ga, In, Sn, Ge, Pb, or a combination of two or more selected from these, and X is a chalcogen element and may include S, Se, Te, or a combination of two or more selected from these.

[0011] The transition metal dichalcogenide is MoS 2 , MoSe 2 , MoTe 2 , WS 2 , WSe 2 , WTe 2 , ZrS 2 , ZrSe 2 , HfS 2 , HfSe 2 , NbSe 2 , ReSe 2 , PdTe 2 or may include a combination of two or more selected from these.

[0012] The inorganic quantum dots may have a bandgap of 1.2 eV or less.

[0013] The inorganic quantum dots may include InAs, PbS, CdS, GaAs, InGaAs, InP, GaInP, and a combination of two or more selected from these.

[0014] The electrode contains a metal or a metal compound, and the metal or the metal compound may contain a metal element including Ti, Ni, Cr / Au, Ag, and a combination of two or more selected from these.

[0015] In addition, in order to achieve the above object, a method for manufacturing a optoelectronic synaptic device according to a preferred embodiment of the present invention includes a step of synthesizing a two-dimensional semiconductor material on a silicon oxide substrate, a step of transferring the two-dimensional semiconductor material onto another semiconductor substrate to form a two-dimensional semiconductor material layer, a step of depositing a plurality of metal layers arranged apart from each other on a part of the two-dimensional semiconductor material layer to form an electrode layer, and a step of applying an inorganic quantum dot colloid solution and a ligand solution on the surface of another part of the two-dimensional semiconductor material layer, coating, and then drying to form a photoactive layer.

[0016] The two-dimensional semiconductor material layer may be a single layer or a multi-layer of two or more layers.

[0017] The transfer step may be a wet transfer.

[0018] The ligand solution is a mixed solution in which an organic ligand and an organic solvent are mixed. The organic ligand substance may have a short carbon chain or ring of C1 to C8 and may contain any one or more functional groups selected from a thiol group, an amine group, a carboxyl group, and combinations thereof.

[0019] The organic ligand may include thiol-based ligands such as 1,2-ethanedithiol (EDT), 3-mercaptopropionic acid (MPA), benzenedithiol (BZT); amine-based ligands such as ethylenediamine (EDA), ammonium thiocyanate (SCN); and at least a combination of two or more selected from these.

[0020] The step of forming the photoactive layer may be performed at room temperature.

Advantages of the Invention

[0021] According to the present invention as described above, an optoelectronic synapse device according to a preferred embodiment of the present invention includes a photoactive layer in which an inorganic quantum dot that receives a near-infrared optical signal and a transition metal dichalcogenide as a two-dimensional semiconductor material that exhibits synaptic characteristics by optical stimulation are directly in contact with each other to form a heterojunction. As a result, there is an effect that a synaptic reaction to an optical signal in the near-infrared wavelength band becomes possible. Therefore, not only visible light signals but also infrared wavelength signals can be used for accurate object recognition. In addition to the light detection characteristics that are sensitive and fast in response to infrared wavelength signals, a human vision-brain function simulation function that exhibits neuromorphic characteristics by an infrared wavelength light response (visual response) is realized in a single element, making it possible to be easily applied in the field of autonomous driving mobility.

[0022] The effects of the present invention are not limited to the effects mentioned above at all, and are clearly understandable to those skilled in the art from the description throughout the specification, and include other effects not explicitly mentioned.

Brief Description of the Drawings

[0023]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Mode for Carrying Out the Invention

[0024] Hereinafter, preferred embodiments of the present invention will be described in more detail with reference to the accompanying drawings. The advantages and features of the present invention, and the methods for achieving them, will become even more apparent by referring to the embodiments described in detail in conjunction with the accompanying drawings. However, the technical idea of the present invention is not limited to the embodiments disclosed below, and can be embodied in various different forms. Merely, the following embodiments complete the technical idea of the present invention and are provided to fully inform those with ordinary knowledge in the technical field to which the present invention belongs of the scope of the present invention. The present invention is only defined by the scope of the claims. The same reference numerals throughout the specification indicate the same components.

[0025] Also, unless otherwise specified or clearly inconsistent with the context in this specification, all terms used in this disclosure, including technical and scientific terms, can be used with the same meaning commonly understood by those with ordinary knowledge in the technical field to which the present invention pertains. Terms generally used and defined in a dictionary are not to be construed in an ideal or overly formal sense unless clearly defined in this application. The terms used in this specification are merely for the purpose of explaining the embodiments and are not intended to limit the present invention. In this specification, singular expressions include plural expressions unless clearly having a different meaning from the context.

[0026] Expressions such as "comprises" and / or "comprising" used in this specification do not exclude the presence or addition of the recited components, steps, operations, and / or elements.

[0027] Optoelectronic synaptic device comprising a photoactive layer including a heterojunction of an inorganic quantum dot - two - dimensional semiconductor material

[0028] FIG. 1 is a schematic diagram showing a cross-section of a optoelectronic synaptic device according to an embodiment of the present invention.

[0029] Referring to FIG. 1, the optoelectronic synaptic device 100 may be provided on a substrate 10 and include an optoactive layer 40 containing inorganic quantum dots 20 and a two-dimensional semiconductor material 30, and a plurality of electrodes 50 provided on the optoactive layer 40 and arranged apart from each other.

[0030] As the substrate 10, semiconductor substrates such as silicon and SOI (Silicon-on-insulator) can be used as the semiconductor material. Also, silicon carbide (SiC), gallium nitride (GaN), gallium oxide (Ga 2 O 3A semiconductor substrate having a wide bandgap (WBG) such as etc. can be used. As the substrate 10, one further doped with a dopant can also be used.

[0031] The electrode 50 may contain a metal or a metal compound. The metal or metal compound may contain a metal element including Ti, Ni, Cr / Au, Ag, and a combination of two or more selected from these, and any type of metal element suitable for electronic devices such as metal electrodes and metal interconnections can be used without limitation as long as it is of a type containing such metal elements.

[0032] The photoactive layer 40 may include inorganic quantum dots 20 and a two-dimensional semiconductor material 30 as a light-receiving layer that receives an applied optical signal. In particular, the photoactive layer 40 can be easily used as a channel layer of a photoelectronic synapse device capable of reacting to an optical signal including a near-infrared wavelength by directly contacting the inorganic quantum dots 20 that receive a near-infrared optical signal and the two-dimensional semiconductor material 30 that exhibits synaptic characteristics upon optical stimulation to form a heterojunction.

[0033] Specifically, when an infrared optical signal is irradiated onto the inorganic quantum dot 20 layer of the photoactive layer 40, charges are excited from the valence band to the conduction band of the quantum dots, and the excited charges are sent to the channel layer of the two-dimensional semiconductor material 30 in contact with the quantum dots, enabling a current to flow through the semiconductor channel layer. At this time, a portion of the charges are trapped / detrapped at the interface between the transition inorganic quantum dots 20 and the two-dimensional semiconductor material 30, making it possible to reversibly control the conductivity of the semiconductor channel. Through this, by controlling the conductivity of the channel of the two-dimensional semiconductor material 30 by applying an infrared signal, it becomes possible to variably control the concentration of the trapped charges and realize the memory, learning, and forgetting characteristics related to infrared stimulation. In particular, the optoelectronic synaptic device according to a preferred embodiment of the present invention adopts a vertical heterojunction structure between an infrared-sensitive zero-dimensional material (inorganic quantum dots 20) and a two-dimensional semiconductor material 30 of the semiconductor channel layer, making it possible to reversibly control the charge trapping / detrapping behavior at the junction interface of the light (infrared)-sensitive layer - semiconductor channel layer. Different from a single-material-based neural network device without a heterojunction structure, it becomes possible to realize even higher memory and learning capabilities.

[0034] First, the inorganic quantum dots 20 can be a material capable of reacting to an optical signal, for example, an optical pulse, and capable of absorbing and emitting light in the visible light to the entire near-infrared wavelength region, for example, in the wavelength region of 380 nm to 1500 nm. In particular, the wavelength region capable of accepting the inorganic quantum dot 20 material according to a preferred embodiment of the present invention may include the near-infrared wavelength range, specifically, the wavelength range of 800 nm to 1500 nm, and more specifically, the wavelength range of 900 to 1200 nm.

[0035] The inorganic quantum dot 20 material is a zero-dimensional (0D) material and is a homogeneous circular inorganic particle having a nanoscale diameter, which can have a diameter of 0.1 to 10 nm, specifically, can have a diameter of 0.5 to 7 nm, and more specifically, can have a diameter of 1 to 5 nm, but is not limited thereto.

[0036] Also, the inorganic quantum dot 20 material according to a preferred embodiment of the present invention is a semiconductor material that absorbs and emits light in the near-infrared region, and may be a material having a band gap of 1.2 eV or less. The inorganic quantum dot 20 material may include, for example, InAs, PbS, CdS, GaAs, InGaAs, InP, GaInP, and combinations of two or more selected from these. In one aspect, it may include InAs, but is not limited thereto. In particular, InAs quantum dots as the inorganic quantum dot 20 material are semiconductor materials capable of absorbing and emitting light in the near-infrared wavelength range, while complying with the Restriction of Hazardous Substances (RoHS) directive, and may be materials that can easily replace lead-chalcogenide quantum dots containing highly toxic heavy metals, such as PdS, CdS, etc. InAs quantum dots can mainly exhibit n-type characteristics.

[0037] Furthermore, the inorganic quantum dot 20 may be covered with an organic ligand or the like, which will be described later, for passivation due to the charge trapping effect.

[0038] On the other hand, the inorganic quantum dot 20 may be further doped or alloyed for the effective light absorption ability of the quantum dot, specifically, the absorption ability of infrared light. Two or more types of inorganic quantum dots may be combined, or may be manufactured in a core-shell structure for effective passivation.

[0039] Next, the two-dimensional (2D) semiconductor material 30 can have a structure in which strong covalent bonds are formed within a single layer and are bonded with relatively weak Vander Waals forces between layers. Different from ordinary optoelectronic devices, the 2D semiconductor material 30 can be directly used as the channel layer of an optoelectronic device by itself using its direct transition property, which has the merit of simplifying the device structure.

[0040] The 2D semiconductor material 30 may be provided as extremely ultrathin film-like or extremely ultrathin plate-like particles, such as flakes, having a layered structure within the photoactive layer 40, and may be provided as a monolayer or a multilayer of two or more layers. Specifically, the 2D semiconductor material 30 may be provided in a multi-layer structure of several layers. Although the 2D semiconductor material 30 exhibits indirect transition characteristics in a bulk or normal film-thickness thin-film state, it exhibits direct transition characteristics when the film thickness is within a single layer or several layers, has excellent optical responsiveness, is transparent, and moreover, has flexible characteristics, so it can be effectively applied as an optoelectronic device.

[0041] In addition, the 2D semiconductor material 30 has a layered structure in which each layer retains a very strong covalent bond between constituent atoms and is bonded by weak Vander Waals forces between the layers. Since there are no dangling bonds extending outside the layer and there are only two-dimensional interactions with the constituent atoms in principle, the carrier transport shows a ballistic transport mode, different from that of ordinary thin films and bulk materials. Thus, it can be applied as a semiconductor with high mobility, high speed, and low power.

[0042] In addition, the two-dimensional semiconductor material 30 can be hetero-bonded with various materials due to its homogeneous surface characteristics, and through this, it is applicable to synaptic elements in the form of a bonding structure. In particular, the two-dimensional semiconductor material 30 has the merit that it can have a photoelectronic reaction sensitive to an extremely small amount of optical stimulation due to its thin layered structure at the atomic scale level. Therefore, by reacting sensitively to the application of pulsed optical stimulation, it becomes possible to exhibit memory / learning ability with increased conductivity and forgetting characteristics due to electrical stimulation.

[0043] The two-dimensional semiconductor material 30 may include a transition metal dichalcogenide (TMD). Specifically, the transition metal dichalcogenide material has the chemical formula MX 2 where M is a transition metal element, for example, Mo, W, Nb, V, Ta, Ti, Zr, Hf, Tc, Re, Ru, Co, Pd, Pt, Cu, Ga, In, Sn, Ge, Pb, or a combination of two or more selected from these, and X is a chalcogen element, which may include S, Se, Te, or a combination of two or more selected from these. Specifically, the transition metal dichalcogenide material is MoS 2 , MoSe 2 , MoTe 2 , WS 2 , WSe 2 , WTe 2 , ZrS 2 , ZrSe 2 , HfS 2 , HfSe 2 , NbSe 2 , ReSe 2 , PdTe 2 or a combination of two or more selected from these. More specifically, the transition metal dichalcogenide material is MoS 2 , MoSe 2 , WS 2 , WSe 2 or a combination of two or more selected from these. In one aspect, WSe 2It may be included, but is not limited thereto in any way.

[0044] The crystal structure of the transition metal dichalcogenide material has a covalent bond between M which is a transition metal and X which is a chalcogen element, and based on this, it can have a hexagonal structure in the plane direction. It is also possible to cause mutations in the crystal structure through further phase change steps or doping steps.

[0045] Method for manufacturing an optoelectronic synaptic device comprising a photoactive layer including a heterojunction of an inorganic quantum dot - two - dimensional semiconductor material

[0046] In the manufacturing method of the optoelectronic synaptic device according to an embodiment of the present invention, first, a step of preparing a two-dimensional semiconductor material on a silicon oxide (silicon dioxide) substrate may be performed.

[0047] In the step of preparing the two-dimensional semiconductor material, specifically, a chemical vapor deposition (CVD) method can be used. This may mean that a quartz boat containing a precursor material is placed at a certain interval and heated in a chemical vapor deposition equipment provided with a plurality of, for example, two heating zones, so that the two-dimensional semiconductor material grows or deposits on the surface of the silicon oxide substrate. However, the step of preparing the two-dimensional semiconductor material is not limited to the method described above, and those skilled in the art can appropriately adjust the experimental conditions or process according to the intended purpose to manufacture a two-dimensional semiconductor material with desired physical properties or crystals.

[0048] Next, a step of transferring the two-dimensional semiconductor material onto another semiconductor substrate to form a two-dimensional semiconductor material layer may be performed. The semiconductor substrate is a semiconductor substrate such as silicon or SOI (Silicon-on-insulator), and can be used as a substrate different from the above-mentioned silicon oxide substrate which is a bulk insulator. Note that silicon carbide (SiC), gallium nitride (GaN), gallium oxide (Ga 2 O 3A semiconductor substrate having a wide bandgap (WBG) such as etc. can be used. As the semiconductor substrate, one further doped with a dopant can also be used.

[0049] The two-dimensional semiconductor material layer can be in direct contact with the semiconductor substrate to form a van der Waals (vdW) bond by van der Waals force. Specifically, the bond between the silicon lattice on the surface of the semiconductor substrate and the two-dimensional semiconductor material layer can be formed by a bond due to van der Waals force. The atoms of each layer do not cross or penetrate each other, but a gap is formed so that each interface can be physically clearly distinguished, that is, a van der Waals gap may be formed between the semiconductor substrate and the two-dimensional semiconductor material layer. In particular, in the manufacturing process of the two-dimensional semiconductor material layer, specifically, by applying a transfer process, and more specifically, a wet transfer process, a thin film with a uniform film thickness can be formed while minimizing physical damage to the surface. It should be noted that by providing the two-dimensional semiconductor material layer formed by van der Waals bonding, the dangling bonds with high reactivity on the surface of the semiconductor substrate are removed, and the physical properties inherent to the substrate can be preserved, so it can be advantageously applied to the realization of high-performance devices.

[0050] Thereafter, a step of forming an electrode layer by depositing a plurality of metal layers disposed apart from each other on a part of the two-dimensional semiconductor material layer may be performed. The metal layer may contain a metal or a metal compound. For example, returning to FIG. 1, metal electrodes 50 may be formed on both sides of the two-dimensional semiconductor material layer 30, and inorganic quantum dots 20 described later may be formed in openings where the metal electrodes 50 are not formed. The metal or metal compound may contain Ti, Ni, Cr / Au, Ag, and metal elements including combinations of two or more selected from these, and any type that contains metal elements of a type suitable for use in electronic devices such as metal electrodes and metal interconnections can be used without limitation.

[0051] The method for manufacturing a optoelectronic synaptic device according to an embodiment of the present invention may include a step of applying an inorganic quantum dot colloidal solution and a ligand solution to the surface of another part of the two-dimensional semiconductor material layer and the above-described opening, coating, and then drying to form a photoactive layer.

[0052] The inorganic quantum dots may be the same as the inorganic quantum dots 20 used in the above Optoelectronic synaptic device comprising a photoactive layer including a heterojunction of an inorganic quantum dot - two - dimensional semiconductor material described above.

[0053] The ligand solution may be a mixed solution in which an organic ligand and an organic solvent are mixed. The organic ligand may have a short carbon chain or ring of C1 to C8 for effective passivation of the inorganic quantum dots, and may contain any one or more functional groups selected from thiol groups, amine groups, carboxyl groups, and combinations thereof. Specifically, the organic ligand may be a thiol-based ligand such as 1,2-ethanedithiol (EDT), 3-mercaptopropionic acid (MPA), benzenedithiol (BZT); an amine-based ligand such as ethylenediamine (EDA), ammonium thiocyanate (SCN); and at least two or more combinations selected therefrom. In one aspect, 1,2-ethanedithiol (EDT) can be used as the organic ligand, but it is not limited thereto.

[0054] The photoactive layer is a channel layer of a optoelectronic device capable of reacting to near-infrared wavelength light, and may include a heterojunction formed by direct contact between the inorganic quantum dots and the two-dimensional semiconductor material. The two-dimensional semiconductor material is likely to form a heterojunction with the inorganic quantum dots due to its uniform surface characteristics, and through this, it is applicable to a synaptic device in the form of a 0-dimensional (0D)-2-dimensional (2D) material junction structure. In particular, the two-dimensional semiconductor material has the merit that a photoelectronic reaction sensitive to even a very small amount of optical stimulation becomes possible due to its thin layered structure at the atomic scale level, and thus, by reacting sensitively to the application of a pulsed optical stimulation, it is possible to exhibit a memory / learning ability in which conductivity increases and a forgetting characteristic due to an electrical stimulation.

[0055] Hereinafter, the present invention will be described in more detail using examples and comparative examples. However, the following examples and comparative examples are only for illustration of the present invention, and the scope of the present invention is not limited thereto at all.

[0056] Manufacturing example: WSe 2Synthesis step

[0057] Tungsten selenide (tungsten selenide) (WSe 2 ) To synthesize, a chemical vapor deposition (CVD) apparatus with two heating zones is used. First, silicon oxide (SiO 2 ) is used as the substrate, and a quartz boat containing 480 mg of selenium (Se) (99.5%, manufactured by Sigma-Aldrich) powder is placed in the primary heating furnace, and 40 mg of NaCl (99%, manufactured by Sigma-Aldrich) and tungsten oxide (WO 3 )(99.9%, manufactured by Sigma-Aldrich) A quartz boat containing 240 mg of the mixed powder was placed in the secondary heating furnace. After that, with the distance between the two quartz boats set to 34 cm, the temperature increase rate in the primary heating furnace was 10.9 °C / min and the growth temperature was 600 °C, and the temperature increase rate in the secondary heating furnace was 14.5 °C / min and the growth temperature was 600 °C to grow Se and WO 3 / NaCl. In the synthesis step, the flow rates of Ar and H 2 gases as carrier gases were 100 sccm and 20 sccm respectively. After the synthesis was completed, natural cooling was performed to finally obtain a multilayer flake-shaped WSe 2 layer with a layer thickness of about 50 - 70 nm.

[0058] Example: QD / WSe 2 Manufacture of an optoelectronic synaptic device including a heterojunction as a photoactive layer

[0059] To use the WSe produced by the method of Production Example 1 as the photoactive layer, it was transferred onto a silicon / silicon oxide (Si / SiO 2 ) substrate. After that, 50 nm of nickel (Ni) was deposited using an electron beam evaporator to form metal electrodes. As a result, WSe was separated from each other 2 ) 2A plurality of electrode layers stacked on top of it, that is, a metal (Ni) electrode having a WSe2 / Ni interface was fabricated. Subsequently, an InAs quantum dot colloidal solution was applied onto the WSe2 photoactive layer in the opening where the metal electrode was not formed, spin-coated under the condition of 2,000 rpm for 30 seconds, then a ligand solution EDT (1,2-ethanedithiol) was dropped and left for 30 seconds. After that, it was rotated at 2,000 rpm for 30 seconds, and the process of applying an acetonitrile solution (2,000 rpm) for 5 seconds was repeated twice. Finally, it was rotated at 2,000 rpm for 30 seconds and then baked in a vacuum at a temperature of 150 °C for 30 minutes.

[0060] Comparative example: WSe 2 Manufacture of an optoelectronic synaptic device including as a light signal receiving part

[0061] WSe 2 A optoelectronic synaptic device was fabricated in the same manner as the above example, except that the InAs quantum dot colloidal solution was not applied onto the photoactive layer.

[0062] Figure 2 is a (a) transmission electron microscope (TEM) photograph and (b) X-ray diffraction (XRD) graph of inorganic quantum dots contained in the photoactive layer of an integrated structure for optical signal sensing according to an embodiment of the present invention.

[0063] Referring to Figure 2, it can be confirmed that uniform circular particles having a diameter of approximately 3 - 4 nm are prepared as a colloidal solution in order to apply inorganic quantum dots InAs as a photoactive layer.

[0064] Figure 3 is a (a) schematic diagram, (b) responsivity and detectivity associated with a laser output at a wavelength of 1060 nm, and (c) and (d) I-V graphs of an optoelectronic synaptic device according to an embodiment of the present invention.

[0065] Referring to FIG. 3, after applying an infrared laser with a wavelength of 1060 nm to the photoactive layer of the optoelectronic synaptic device, when the current in the OFF region of the device increased to confirm the responsivity and detectivity, it was confirmed that the dark current characteristics with respect to infrared stimulation were enhanced.

[0066] FIG. 4 shows the results of the conductance according to the number of (a) and (d) pulses, the PPF index of (b) and (c), the nonlinearity according to the presence or absence of a quantum dot - two - dimensional semiconductor heterojunction with the laser output in (e), and the synaptic weight value according to the number of pulses of the optoelectronic synaptic device according to an embodiment of the present invention.

[0067] Referring to FIG. 4, it can be confirmed that the memory·learning (potentiation) and forgetting (depression) characteristics are realized by applying an infrared laser with a wavelength of 1060 nm to the photoactive layer of the optoelectronic synaptic device. Also, it can be confirmed that spike - timing - dependent plasticity (STDP), excitatory postsynaptic current (EPSC), inhibitory postsynaptic current (IPSC), paired - pulse facilitation (PPF), and the forgetting characteristics of information with low power consumption are realized, enabling the realization of neuromorphic technology. Furthermore, it can be confirmed that the optoelectronic synaptic device of the present invention has the potential to be an in - sensor computing device capable of performing signal recognition - processing - operation in a single device.

[0068] Using a probe station (Probe station (M5VC, manufactured by MS TECH, Korea)) and a laser oscillator, the transfer and output characteristics were measured. At this time, the existing P - type characteristic WSe 2Compared with the element, InAs / WSe 2 It was confirmed that N-type characteristics can be obtained from the element. When the responsivity and detectivity were examined under a wavelength of 1060 nm, they were 2.2 A / W and 9.0×10 10 Jones were measured. After that, when irradiating with a single pulse, it can be confirmed that the photoresponse current shows a response characteristic with an improvement of about 60% compared with the comparative example (shown in WSe 2 ).

[0069] InAs / WSe 2 In order to confirm the usability of a vision sensor that mimics the human retina using a heterojunction structure, neuromorphic characteristics were measured. When using visible light and infrared laser wavelengths of 405 nm and 1060 nm, and applying 100 pulses at 0.5, 1, 2, 3 mW and 5, 10, 15 mW respectively at a frequency of 0.5 Hz, potentiation and depression characteristics were respectively manifested. Based on this, when analyzing the non-linearity characteristics, it was confirmed that there was a 5% increase compared with the existing WSe 2 element. In addition, by manifesting paired pulse facilitation (PPF) and paired pulse depression (PPD), it was confirmed that there is a possibility of neural imitation.

[0070] Figure 5 is a (a) schematic diagram, (b) IV graph according to the ON / OFF of light, and (c) graph measuring the potentiation and depression characteristics according to the application of light pulses of a optoelectronic synaptic device according to an embodiment of the present invention.

[0071] Referring to FIG. 5, it can be confirmed that the photosensitivity and plasticity of the synaptic device are improved as light with an infrared wavelength (1060 nm) is applied as a pulsed stimulus. After visible light was pulsed applied to the optoelectronic synaptic device of the present invention, the conductivity increased with the application of the pulse, and then, electrical depression using a back gate was demonstrated to observe the plasticity of the synaptic device. Therefore, it can be confirmed that the optoelectronic synaptic device of the present invention can also confirm neuromorphic characteristics along with the visual response by light stimulation, and thereby it is possible to realize the technical characteristics of the visual-brain function simulation technology.

[0072] As described above, the embodiments of the present invention have been described with reference to the accompanying drawings. However, those having ordinary knowledge in the technical field to which the present invention pertains can understand that the present invention can also be implemented in other specific forms without changing its technical idea and essential features. Therefore, the above-described embodiments are merely exemplary in all respects and not restrictive.

Description of Reference Numerals

[0073] 100: Optoelectronic synaptic device 10: Substrate 20: Inorganic quantum dots 30: Two-dimensional semiconductor material 40: Photoactive layer 50: Electrode

Claims

1. a photoactive layer provided on the substrate, the photoactive layer including inorganic quantum dots and a two-dimensional semiconductor material; a plurality of electrodes disposed on the photoactive layer and spaced apart from one another; Equipped with the inorganic quantum dots and the two-dimensional semiconductor material are in direct contact with each other to form a heterojunction; At least a portion of the surface of the inorganic quantum dot, except for a region where a heterojunction with the two-dimensional semiconductor material is formed, is covered with an organic ligand.

1. An optoelectronic synapse element comprising:

2. The wavelengths of light that are acceptable to the photoactive layer include the visible to near infrared wavelength range. The optoelectronic synapse device of claim 1 .

3. The two-dimensional semiconductor material may be a single layer or a multi-layer structure having two or more layers. The optoelectronic synapse device of claim 1 .

4. The two-dimensional semiconductor material includes a transition metal dichalcogenide. The optoelectronic synapse device of claim 1 .

5. The transition metal dichalcogenide has the formula MX ２ It is expressed as The M is a transition metal element, and includes Mo, W, Nb, V, Ta, Ti, Zr, Hf, Tc, Re, Ru, Co, Pd, Pt, Cu, Ga, In, Sn, Ge, Pb, or a combination of two or more selected from among these; The X is a chalcogen element, and includes S, Se, Te, or a combination of two or more selected from the above. The optoelectronic synapse device according to claim 4 .

6. The transition metal dichalcogenide is MoS ２ , MoSe ２ , MoTe ２ , W.S. ２ , WSe ２ , W.T.e ２ , ZrS ２ , ZrSe ２ , HfS ２ , HfSe ２ , NbSe ２ ,ReSe ２ , PdTe ２ or a combination of two or more selected from these The optoelectronic synapse device according to claim 4 .

7. The inorganic quantum dots have a band gap of 1.2 eV or less. The optoelectronic synapse device of claim 1 .

8. The inorganic quantum dots include InAs, PbS, CdS, GaAs, InGaAs, InP, GaInP, and combinations of two or more selected from these. The optoelectronic synapse device of claim 1 .

9. the electrode comprises a metal or a metal compound; The metal or metal compound includes metal elements including Ti, Ni, Cr / Au, Ag, and combinations of two or more selected from the above. The optoelectronic synapse device of claim 1 .

10. synthesizing a two-dimensional semiconductor material on a silicon oxide substrate; wet transferring the two-dimensional semiconductor material onto another semiconductor substrate to form a two-dimensional semiconductor material layer; forming an electrode layer by depositing a plurality of metal layers spaced apart from one another on a portion of the two-dimensional semiconductor material layer; applying an inorganic quantum dot colloid solution and a ligand solution to another surface of the two-dimensional semiconductor material layer, coating the surface, and then drying the surface to form a photoactive layer; Including, the inorganic quantum dots and the two-dimensional semiconductor material layer are in direct contact with each other to form a heterojunction; The ligand solution is a mixed solution in which an organic ligand and an organic solvent are mixed, and the organic ligand material has a short carbon chain or ring of C1 to C8 and includes at least one functional group selected from a thiol group, an amine group, a carboxyl group, and combinations thereof; At least a portion of the surface of the inorganic quantum dot, except for a region where a heterojunction with the two-dimensional semiconductor material is formed, is covered with the organic ligand.

2. A method for producing an optoelectronic synapse element comprising the steps of:

11. The wavelengths of light that are acceptable to the photoactive layer include the visible to near infrared wavelength range. A method for manufacturing the optoelectronic synapse device according to claim 10.

12. The inorganic quantum dots have a band gap of 1.2 eV or less. A method for manufacturing the optoelectronic synapse device according to claim 10.

13. The inorganic quantum dots include InAs, PbS, CdS, GaAs, InGaAs, InP, GaInP, and combinations of two or more selected from these. A method for manufacturing the optoelectronic synapse device according to claim 10.

14. The two-dimensional semiconductor material includes a transition metal dichalcogenide. A method for manufacturing the optoelectronic synapse device according to claim 10.

15. The transition metal dichalcogenide has the formula MX ２ It is expressed as The M is a transition metal element, and includes Mo, W, Nb, V, Ta, Ti, Zr, Hf, Tc, Re, Ru, Co, Pd, Pt, Cu, Ga, In, Sn, Ge, Pb, or a combination of two or more selected from among these; The X is a chalcogen element, and includes S, Se, Te, or a combination of two or more selected from the above. A method for producing the optoelectronic synapse device according to claim 14.

16. The two-dimensional semiconductor material layer may be a single layer or a multi-layer of two or more layers. A method for manufacturing the optoelectronic synapse device according to claim 10.

17. The organic ligand includes thiol-based ligands such as 1,2-ethanedithiol (EDT), 3-mercaptopropionic acid (MPA), and benzenedithiol (BZT); amine-based ligands such as ethylenediamine (EDA) and ammonium thiocyanate (SCN); and combinations of at least two of these. A method for manufacturing the optoelectronic synapse device according to claim 10.

18. The step of forming the photoactive layer is performed at room temperature. A method for manufacturing the optoelectronic synapse device according to claim 10.

19. The electrode layer comprises a metal or a metal compound, The metal or metal compound includes metal elements including Ti, Ni, Cr / Au, Ag, and combinations of two or more selected from the above. A method for manufacturing the optoelectronic synapse device according to claim 10.

Images