KR20200073027A - New two-terminal synapse device - Google Patents

Abstract

The present invention relates to a SyNAPSE device with a novel two-terminal structure. According to the present invention, the SyNAPSE device with a novel two-terminal structure comprises: an upper electrode; an active layer; a storage layer; and a lower electrode, wherein the upper electrode has a thickness of 50 nm, and the lower electrode has a thickness of 100 nm. According to the present invention, the performance of a hardware-based neuromorphic system can be improved.

Description

New two-terminal synapse device

The present invention relates to a synapse (Systems of Neuromorphic Adaptive Plastic Scalable Electronics) device having a two-terminal structure, and more specifically, a synapse device having a two-terminal structure includes an upper electrode, an active layer and a storage layer, and a lower electrode. And a storage layer capable of storing dopant ions extracted from the active layer according to the change in conductivity according to the concentration of ions in the active layer and the application of an external electric field. ions).

The SyNAPSE (Systems of neuromorphic adaptive plastic scalable electronics) project has been conducted by HRL Labs, IBM Labs, HP Labs and Stanford University, Cornell University, Columbia University, University of Wisconsin, University of California, University of Michigan and Boston University since 2008. It is a research project involving researchers in the fields of engineering, materials engineering, physics, medicine, and neuroscience.

The synapse of a biological system detects a change in synaptic weight in the process of processing signals transmitted from neurons in neuron-synapse in biological systems, thereby exerting learning and memory functions. An ion such as Ca2+ or Na+ moves from a synapse to a presynaptic neuron by an electrical signal, and a signal is processed by allowing a neurotransmitter, a signal transduction substance in the neuron, to move to a postsynaptic neuron through a synapse. In this process, the distribution of ions in the synapse changes, and the synaptic weight changes as the receptor concentration of the neurotransmitter in the postsynaptic neurons changes. This change in synaptic weight can be said to be a characteristic corresponding to a resistive random access memory (ReRAM) that stores information according to a change in resistance.

1 is a schematic cross-sectional view of a synaptic device for application of a conventional neuromorphic system.

Synaptic devices for neuromorphic system applications may include a substrate 100, a first electrode 200, a tunneling barrier layer 300, a resistance change layer 400, and a second electrode 500. have.

The substrate 100 may be any material that can serve as a supporting substrate. For example, the substrate 100 may be a silicon substrate. The substrate 100 may be omitted in some cases.

The first electrode 200 is positioned on the substrate. The first electrode 200 may include Pt or W. The first electrode 200 may be formed by sputtering, RF sputtering, RF magnetron sputtering, pulse laser deposition, chemical vapor deposition, plasma enhanced chemical vapor deposition, atomic layer deposition, or molecular beam epitaxy deposition.

The tunneling barrier layer 300 is positioned on the first electrode. The tunneling barrier layer 300 is characterized by realizing a nonlinear characteristic by acting as a barrier layer for electron movement.

The tunneling barrier layer 300 may include a metal oxide or metal-insulator transition material.

The metal oxide may include TiOx, TixOy, HfOx, HfxOy, AlOx, AlxOy, TaOx, TaxOy, VOx, VxOy, NbxOy, NbOx, FexOy, FeOx, WxOy, or WOx. X and Y at this time are real numbers greater than zero. On the other hand, when the same material is used as the material of the resistance change layer 400 and the tunneling barrier layer 300, which will be described later, the oxygen composition of the material of the tunneling barrier layer 300 is set larger than that of the resistance change layer 400. It is desirable to do.

In addition, the tunneling barrier layer 300 may be formed of at least two metal oxide layers having different oxygen compositions. For example, the tunneling barrier layer 300 includes a Ti0x layer and a TiOy layer positioned on the Ti0x layer, where y> x. By forming the tunneling barrier layer 300 as a multi-layer, a very high nonlinearity can be obtained as described in detail below.

The titanium oxide film (TiOx) employed as the tunneling barrier layer has a higher nonlinear value than TaOx or AlOx, which can be described as a band structure. In the present invention, band gap engineering was performed by controlling the thickness and oxygen distribution for the titanium oxide film (TiOx). This is because the optimum thickness of the titanium oxide film can effectively reduce the current in the 1/2 Vread region, and the oxygen distribution can control the tunnel barrier properties of the titanium oxide film to exhibit reliable nonlinear behavior. Oxygen annealing oxidized from the surface of the titanium oxide film (TiOx) to the bulk region to produce insulating ultra-thin TiOy. This can provide a highly integrated synaptic device without a selection device.

In recent years, since the computing system has been greatly improved by low power consumption, error tolerance, and parallel data processing [1], to efficiently process a large amount of data, the neuromorphic computing system is a memory and computing. Extremely parallel computing, as well as devices, is more attractive than the Phon-Neumann computing system.

The performance of a neuromorphic system is highly dependent on a synapse device, a key part of the neuromorphic system.

For this reason, resistive random access memory, ferroelectric random access memory, and the like have been proposed. However, no optimized technology has been found, and researchers have attempted to create synaptic devices with new concepts.

Recently, a hardware-based brain-inspired neuromorphic system has been spotlighted as one of the next generation methods to process vast and unstructured information. In order to build such a system as hardware, one of the core components, the Synapse (Systems of Neuromorphic Adaptive Plastic Scalable Electronics) device, is required, and the properties of the synapse device must be able to control various conductivity.

Synapse devices can generally be fabricated by using non-volatile memory devices. Non-volatile memory devices are classified into three-terminal devices and two-terminal devices in a large class, but among them, the two-terminal device is attracting attention as a synapse device because it has advantages such as simple process and excellent integration. So far, two-terminal devices having various mechanisms for synapse devices have been studied, and examples thereof include phase shift memory (PRAM), resistance shift memory (RRAM), and ferroelectric memory (FeRAM).

Phase-change memory (PRAM) is an abbreviation of phase-change RAM. It is a RAM that combines the advantages of flash memory and DRAM, and is a non-volatile memory semiconductor that stores data using non-volatile phase change materials instead of conventional silicon. .

RRAM is an abbreviation of Resistive Random Access Memory, and when a sufficiently high voltage is applied to a non-conductive material, a passage through which a current flows is generated and resistance is reduced. Once the passage is created, it can be easily removed or regenerated by applying a voltage. RRAMs using materials such as perovskite or transition metal oxide and chalcogenide have been developed.

Ferroelectric memory (FeRAM) is a next-generation semiconductor that has the advantages of a large memory data storage function of Ferroelectric Random Access Memory DRAM, a high-speed operation function of SRAM, and a flash memory semiconductor that does not erase recorded data even when the power is turned off. The ferroelectric material is sensitive to low electric shock. Since FeRAM is manufactured using materials that are sensitive to electric shock, it provides the functions of D-RAM, S-RAM, and flash memory in one cell that stores data, and the speed of recording and removing information is the same as that of existing flash memory or EEP ROM. More than 1000 times faster.

However, despite the active progress of the synapse device and its research, the optimized synapse device is not provided mainly due to the rapid change in conductivity due to the limitations of each mechanism. Therefore, research on a synapse device having a new structure and mechanism is required.

Patent registration number 10-1588980 (Registration date January 20, 2016), "Synaptic device and method for manufacturing neuromorphic system", Pohang University of Science and Technology

[1] Kuzum, D, et al (2013) "Synaptic electronics: materials, devices and applications" Nanotechnology 24(38):382001. [2] Mai, V H, et al (2015) "Memristive and neuromorphic behavior in a LixCoO2 nanobattery" Scientific reports 5:7761

An object of the present invention for solving the above-described problems is that a two-terminal synapse device is composed of an upper electrode, an active layer and a storage layer, and a lower electrode, and the concentration of ions in the active layer Provides a two-terminal synapse device using a storage layer capable of storing extracted ions that can store dopant ions extracted from the active layer according to the change in conductivity according to ions and the application of an external electric field do.

In order to achieve the object of the present invention, a new two-terminal synaptic device includes an upper electrode to which an external electric field is applied (+) or (-); Dopant ions are moved to the storage layer according to the application of a (+) or (-) external electric field to the lower electrode and the upper electrode, and an active layer in which the conductivity of the synaptic device increases or decreases depending on the concentration of the dopant ions ; Dopant ions moved from the active layer upon application of a (+) external electric field to the upper electrode are stored, and dopant ions exit the storage layer upon application of a (-) external electric field to the upper electrode, and dopant ions move to the active layer, A storage layer made of a material that stably stores the shifted dopant ions to have inactive memory characteristics; And provides a two-terminal synaptic device comprising a lower electrode,

A material that allows the storage layer to have the inactive memory characteristic is a-Si or graphene.

A new two-terminal synapse device having an upper electrode, an active layer and a resistive layer, and a lower electrode of the present invention is composed of an upper electrode, an active layer and a storage layer, and a lower electrode, and the ion of the active layer Provides a synapse device with a two-terminal structure using a storage layer capable of storing extracted ions that can store dopant ions extracted from the active layer according to the application of an external electric field and a change in conductivity according to concentration of ions do.

The two-terminal synaptic device with a new structure and mechanism, despite being a prototype, showed excellent synaptic properties such as very gradual and linear conductivity changes. These excellent properties can contribute to improving the performance of a hardware-based neuromorphic system. In addition, since the dopant ion included in the active layer of the proposed synaptic device can apply various ions (Cu, Ag, etc.) other than Li, the range of materials used is also expected to vary.

The synapse device of a two-terminal structure using a storage layer capable of storing the extracted ion and the conductivity change characteristic according to the concentration of ions in the active layer is a hardware-based neuromorphic system, a multi-level memory ( It is used as a multi-level memory device. It can be applied to artificial intelligence-based IoT systems and pattern recognition systems.

1 is a schematic cross-sectional view of a synaptic device for existing neuromorphic system applications.
Figure 2 is (left) the structure of the fabricated two-terminal synapse device: a two-terminal synapse device including a lower electrode/storage layer/active layer/upper electrode, Ti/ LiCoO2 (active layer)/ a-Si (storage layer)/Ni (right) This is a picture showing the mechanism of a two-terminal synaptic device of the present invention.
3 is a view showing a change in conductivity according to a positive voltage application (potentiation process) and a negative voltage application (depression process) of the fabricated two-terminal structure synapse device.

Hereinafter, with reference to the accompanying drawings, preferred embodiments of the present invention will be described in detail the configuration and operation of the invention.

The present invention proposes a new two-terminal synapse device having an upper electrode, an active layer and a storage layer, and a lower electrode.

The new two-terminal synapse device includes an upper electrode, an active layer and a storage layer, and a lower electrode. This study is a layer capable of storing extracted ions that can store the dopant ions extracted from the active layer according to the application of an external electric field and the change in conductivity according to the concentration of ions of the dopant ions in the active layer. A synapse device with a two-terminal structure was developed.

The conductivity of the active layer is changed by the ion concentration of the active layer according to the application of a (+)/(-) electric field to the upper electrode of the synaptic device, and the conductivity in the active layer is increased. Or is reduced.

The synapse device of the new two-terminal structure of the present invention is characterized in that two core layers, an active layer and a storage layer, are required.

First, the conductivity of an active layer of a two-terminal synaptic device increases/decreases depending on the concentration of dopant ions that act as a dopant by application of an external electric field to the upper and lower electrodes. As a different layer, an active layer is used to control the conductivity of the synaptic device.

In this case, the active layer acts as a dopant, but dopant ions move to the active layer->storage layer when a different layer ((+) field is applied to the upper electrode according to the application of an external electric field to the upper and lower electrodes of the synaptic device; Alternatively, dopant ions (dopant ions: Li, Cu, Ag, Mg, etc.) that can be moved from the storage layer to the active layer when the (-) electric field is applied to the upper electrode must be included.

When a (+) electric field is applied to the upper electrode of a two-terminal synaptic device, dopant ions moved by an external electric field are received, and dopant ions move from an active layer to a storage layer and are stored in a storage layer. , The conductivity of the active layer increases.

Concentration of dopant ions in the active layer when the dopant ions of the active layer move to another layer by external electric fields (+) and (-) applied to the lower and upper electrodes of the synaptic device Decreases, and the conductivity of the active layer changes (increase or decrease in conductivity), thereby controlling the conductivity of the synapse device.

Second, when the (+) electric field is applied to the upper electrode of the two-terminal synaptic device, the dopant ions are moved by moving dopant ions from the active layer to the storage layer by an external electric field ( dopant ions) are stored in the storage layer, and the conductivity of the active layer increases.

At this time, by storing the dopant ions extracted from the active layer in the storage layer, in the absence of an external electric field, it is possible to prevent the re-migration from the storage layer to the active layer, thereby the ratio of conductivity of the synaptic device It has the characteristics of non-volatile memory.

From a structure having two layers, an active layer and a storage layer, a two-terminal synapse according to a (+) or (-) external electric field (having different polarities) applied to a lower electrode and an upper electrode of a two-terminal synaptic device It is possible to obtain a reversible operating characteristic that can increase or decrease the conductivity of the device.

For example, when a positive electric field (positive bias) is applied to the lower electrode and the upper electrode of the synaptic device, the conductivity of the synapse device increases as a result of the dopant ions in the active layer moving to the storage layer.

Conversely, when a negative electric field (negative bias) is applied to the lower electrode and the upper electrode of the synaptic device, dopant ions stored in the storage layer escape, and dopant ions are injected from the storage layer back into the active layer and conductivity Reduced, it is possible to adjust the conductivity of the synaptic element back to its original state.

(active layer)/ a-Si (storage layer)/Ni (우) 제작된 본 발명의 2단자 구조의 시냅스 소자의 메커니즘을 보인 그림이다. Figure 2 (left) the structure of the fabricated two-terminal synapse device: a two-terminal synapse device comprising a lower electrode/storage layer/active layer/upper electrode, Ti/

(active layer)/ a-Si (storage layer)/Ni (right) It is a picture showing the mechanism of a two-terminal synaptic device of the present invention.

In an embodiment, the new two-terminal synaptic device of the present invention comprises: an upper electrode receiving an external electric field (+) or (-); It is formed on the resistive layer, and dopant ions move to the storage layer according to the application of an external electric field (+) or (-) to the lower electrode and the upper electrode, and the conductivity of the synaptic device according to the concentration of the dopant ions Active layer that increases or decreases; It is formed on the lower electrode and stores dopant ions moved from the active layer according to the application of a (+) external electric field to the upper electrode, and a storage layer according to the application of a (-) external electric field to the upper electrode. A storage layer composed of a material (a-Si, graphene, etc.) that escapes from the dopant ions and moves to the active layer, and stably stores the transferred dopant ions to have non-volatile memory characteristics (a-Si, graphene, etc.). ; And a lower electrode.

A material that allows the storage layer to have the inactive memory characteristic is a-Si or graphene.

In the two-terminal synaptic device, dopant ions moved from the active layer to the storage layer are stored when an external electric field is applied to the upper electrode, and the conductivity of the active layer increases, and the upper electrode (-) When an external electric field is applied, dopant ions escape from the storage layer and move back to the active layer, so that the conductivity of the active layer decreases.

The upper electrode was formed to a thickness of 50 nm, and Li was used.

active layer로써, 40 nm 두께로 형성되며, 리튬 코발트 산화물 인

를 사용하였다.The active layer

As an active layer, it is formed with a thickness of 40 nm, and lithium cobalt oxide phosphorus

Was used.

The storage layer was formed to a thickness of 40 nm, and a-Si was used.

The lower electrode was formed to a thickness of 100 nm, and Ti was used.

In addition, various materials (Pt, Au, TiN, Ir, Pd, etc.) may be used for the upper electrode and the lower electrode.

The dopant ions contain Li, Cu, Ag, and Mg that can be moved from the active layer to the storage layer/from the storage layer to the active layer by external electric fields applied to the lower and upper electrodes of the two-terminal synaptic device. The metal oxide to be used is used.

을 활성층(active layer)으로 사용하였으며, amorphous Si을 저장층(storage layer)으로 사용하였다. The proposed two-terminal synapse device is lithium cobalt oxide.

Was used as an active layer, and amorphous Si was used as a storage layer.

활성층 내의 Li ion은 도펀트 이온(dopant ion)의 역할을 하며, Li ion의 농도가 감소하면

활성층 내 vacancy[dorpant ion들(Li ions)이 저장층으로 이동하여 생긴 자리]가 형성되므로

활성층 내의 전도도가 증가한다. a-Si은 Li ion들을 저장할 수 있는 물질로 널리 알려져 있으며, 추출된 Li ion들을 a-Si 저장층에 저장함으로써, 시냅스 소자가 활성층에서 조절된 전도도의 비-휘발성 메모리 특성을 얻을 수 있다. The detailed structure of the fabricated two-terminal synapse device is shown in FIG. 2 (left). According to previous studies,

Li ion in the active layer acts as a dopant ion, and when the concentration of Li ion decreases

Since vacancy in the active layer (a place created by the migration of dopant ions (Li ions) to the storage layer) is formed,

The conductivity in the active layer increases. a-Si is widely known as a material capable of storing Li ions, and by storing the extracted Li ions in the a-Si storage layer, the synaptic device can obtain a non-volatile memory characteristic of controlled conductivity in the active layer.

활성층 내의 Li를 이온화시키고 양전하를 갖는 Li ion들을

활성층으로부터 a-Si 저장층의 방향으로 이동시킬 수 있다. 이 결과

활성층 내에 vacancy(Li ions, 즉 dorpant ion들이 이동하여 생긴 자리)가 형성되므로 전도도가 증가한다. a-Si은 Li을 저장할 수 있는 물질로 널리 알려져 있으며 추출된 Li을 저장함으로써 조절된 전도도의 비-휘발성 메모리 특성을 얻을 수 있다. Therefore, in order to increase the conductivity of the two-terminal synaptic device, a positive (+) positive field (positive bias) is applied to the upper electrode as in the operation method of FIG. 2(right). The positive and negative electric fields applied to the lower and upper electrodes of the two-terminal synaptic device

Li ion in the active layer and positively charged Li ions

It can be moved in the direction of the a-Si storage layer from the active layer. This result

Since the vacancy (Li ions, i.e., the site created by the movement of dorpant ions) is formed in the active layer, conductivity increases. a-Si is widely known as a material capable of storing Li, and by storing extracted Li, non-volatile memory characteristics of controlled conductivity can be obtained.

는 활성층(active layer)으로 사용하였으며, amorphous Si은 저장층(storage layer)으로 사용하였다. The two-terminal synapse element is lithium cobalt oxide

Was used as an active layer, and amorphous Si was used as a storage layer.

내의 Li ion들은 도펀트 이온(dopant ion)의 역할을 하며, Li ion의 농도가 감소하면

활성층 내 vacancy(Li ions, 즉 dorpant ion들이 이동하여 생긴 자리)가 형성되어 활성층 내의 전도도가 증가하며, 이는 시냅스 소자 전체의 전도도의 증가를 야기한다.

활성층으로부터 이동된 Li ion들을 a-Si 저장층에 저장됨으로써, 외부 전계를 제거하더라도

활성층 내로 Li ion들의 재이동이 발생되지 않는다. 그 결과, 2단자 구조의 시냅스 소자는 조절된 전도도의 비-휘발성 메모리 특성을 기대할 수 있다. The structure of the fabricated two-terminal synapse device is shown in detail in FIG. 2 (left). According to previous studies

Li ions in the inside act as dopant ions, and when the concentration of Li ions decreases,

The vacancy in the active layer (ie, the site created by the movement of the dorpant ions) is formed to increase the conductivity in the active layer, which leads to an increase in the conductivity of the entire synaptic device.

Li ions moved from the active layer are stored in the a-Si storage layer, so that even if the external electric field is removed

Re-ion of Li ions into the active layer does not occur. As a result, the two-terminal synaptic device can expect non-volatile memory characteristics of controlled conductivity.

활성층(active layer) 내로 다시 주입되게 된다. 그 결과로, 활성층 내의 vacancy들이 채워짐으로써 시냅스 소자의 전도도가 다시 감소하게 된다. Conversely, when a reverse electric field (negative bias) is applied to the upper electrode of the two-terminal synaptic device, Li ions stored in the a-Si storage layer are ionized and Li ions released from the a-Si storage layer

It is injected again into the active layer. As a result, the conductivity of the synaptic device is reduced again by filling the vacancy in the active layer.

FIG. 3 is a diagram showing a change in conductivity according to a positive voltage application (potentiation process) and a negative voltage application (depression process) to an upper electrode and a lower electrode of a new 2-terminal structured synaptic device.

To evaluate the properties of the proposed two-terminal synaptic device, the conductivity response of the synaptic device according to the application of positive and negative voltages to the lower and upper electrodes was evaluated.

First, a positive voltage pulse (8V) was applied, and a read voltage (3v) was applied to detect the changing conductivity, thereby detecting the change in conductivity (FIG. 3). When a positive voltage pulse was applied a total of 50 times, the conductivity was gradually observed to be very linear. From the perspective of a hardware-based neuromorphic system, this linear conductivity change under pulses of the same magnitude is one of the very desirable characteristics (simplification of the construction circuit and increase of system performance).

Therefore, the proposed two-terminal synaptic device shows excellent synaptic properties of the mechanism. Again, 50 negative voltage pulses were applied to reduce the conductivity of the synaptic device, and as a result, a gradual decrease in conductivity was observed.

The two-terminal synaptic device with the novel structure and mechanism of the present invention, despite being a prototype-type, exhibits excellent synaptic properties such as a very gradual and linear change in conductivity. These excellent properties can contribute to the performance improvement of hardware-based neuromorphic systems. In addition, as suggested, since various dopants (Cu, Ag, etc.) with different dopant ions included in the active layer of the synaptic device can be applied, the range of materials to be used is also expected to vary.

The synapse device of a two-terminal structure using a storage layer capable of storing the extracted ions and the conductivity change characteristics according to the concentration of ions in the active layer is a hardware-based neuromorphic system, multi It is used as a multi-level memory device. It can be applied to artificial intelligence-based IoT systems and pattern recognition systems.

As described above, the present invention has been described with reference to preferred embodiments of the present invention, but the present invention is within the scope not departing from the technical spirit and scope of the present invention described in the following claims by those of ordinary skill in the art. It will be understood that various modifications or variations can be carried out.

Claims (11)

An upper electrode receiving an external electric field (+) or (-);
Dopant ions move to the storage layer according to the application of an external electric field (+) or (-) to the lower electrode and the upper electrode, and the active layer increases/decreases the conductivity of the synaptic device according to the concentration of the dopant ions. ;
Dopant ions moved from the active layer upon application of a (+) external electric field to the upper electrode are stored, and dopant ions exit the storage layer upon application of a (-) external electric field to the upper electrode, and dopant ions move to the active layer, A storage layer made of a material that stably stores the shifted dopant ions to have inactive memory characteristics; And
It provides a two-terminal synaptic device comprising a lower electrode,
A new two-terminal synaptic device, wherein a-Si or graphene is used as a material that allows the storage layer to have the inactive memory characteristic. According to claim 1,
The upper electrode is formed with a thickness of 50 nm and Li is used, and the lower electrode is formed with a thickness of 100 nm and uses Ti, a new two-terminal synapse device. According to claim 1,
The upper electrode and the lower electrode are Pt, Au, TiN, Ir, Pd using a material of any one, a new two-terminal synaptic device structure. According to claim 1,
The active layer is formed to a thickness of 40 nm, lithium cobalt oxide phosphorus

Using a new two-terminal synaptic device. According to claim 1,
The storage layer is formed to a thickness of 40 nm, using a-Si, a new two-terminal synaptic device. According to claim 1,
The dopant ions contain Li, Cu, Ag, and Mg that can be moved from the active layer to the storage layer/from the storage layer to the active layer by external electric fields applied to the lower and upper electrodes of the two-terminal synaptic device. A new two-terminal synaptic device using a metal oxide. According to claim 1,
When a (+) external electric field is applied to the upper electrode, dopant ions moved from the active layer to the storage layer are stored, and the conductivity of the active layer increases, and the negative electrode of the (-) external electric field is applied to the upper electrode. A new two-terminal synaptic device in which dopant ions escape from the storage layer upon application and move back to the active layer to decrease the conductivity of the active layer. According to claim 1,
The two-terminal synaptic element

An active layer and an amorphous Si storage layer were used,
In order to increase the conductivity of the synaptic device of the two-terminal structure, a positive (+) positive field (positive bias) is applied to the upper electrode, and a positive (+) positive field applied to the upper electrode of the synaptic device is

Li ion in the active layer and Li ions with positive charge

Moving from the active layer in the direction of the a-Si storage layer, this result

The conductivity increases because vacancy (a place created by the movement of dopant ions (Li ions)) is formed in the active layer, and a-Si is widely known as a material capable of storing Li and the ratio of the controlled conductivity by storing extracted Li -A new two-terminal synaptic device capable of obtaining volatile memory characteristics. The method of claim 8,
Of the two-terminal synaptic device

Li ions in the active layer act as dopant ions, and when the concentration of Li ions decreases,

Since the vacancy in the active layer (a place created by the movement of dopant ions (Li ions)) is formed, the conductivity in the active layer increases, and a-Si is a material that can store Li ions, and the extracted Li ions are stored in the a-Si storage layer. Stored in, a new two-terminal synaptic device, wherein the synaptic device has a non-volatile memory characteristic of controlled conductivity. The method of claim 8,
When a reverse electric field (negative bias) is applied to the upper electrode of the synaptic device of the two-terminal structure, Li ions stored in the a-Si storage layer are ionized to release Li ions from the a-Si storage layer.

A new two-terminal synaptic device, in which the conductivity of the synaptic device is reduced again by filling the vacancy in the active layer. The method of claim 7,
A synaptic device of a two-terminal structure using a storage layer capable of storing the extracted ions and a conductivity change characteristic according to the concentration of ions in the active layer is a hardware-based neuromorphic system, a multi-level memory A new two-terminal synaptic device used as a device.

Images