Jiabin Wang

Top-Gate Electric-Double-Layer IZO-Based Synaptic Transistors for Neuron Networks

In this letter, top-gate electric-double- layer (EDL) indium–zinc-oxide (IZO)-based synaptic transistors were demonstrated. A silicon oxide solid electrolyte film was used as the insulator, which was deposited by the plasma-enhanced chemical vapor deposition method at room temperature. A low operation voltage of 1 V was achieved due to the formation of the EDL layer at the SiO2/IZO interface. In the top-gate synaptic transistors, paired-pulse facilitation and high-frequency filter were mimicked, which are the short-term synaptic behaviors. Standard microfabrication processes were used to pattern, which could be used for large integration in the future.

Carbon Nanotube Transistor with Short-Term Memory

Short-Term Memory (STM) is a primary capability of the human brain. Humans use STM to remember a small amount of information, like someones phone number, for a short period of time. Usually the duration of STM is less than 1 minute. Synapses, the connections between neurons, are of vital importance to memory in biological brains. For mimicking the memory function of synapses, Carbon Nanotube (CNT) networks based thinfilm transistors with Electric Double Layers (EDL) at the dielectric/channel interface were researched in this work. A response characteristic of pre-synaptic potential pulses on the gate electrode of this CNT synaptic transistor was shown remarkably similar to Excitatory Post-Synaptic Current (EPSC) of biological synapses. Also a multi-level modulatable STM of CNT synaptic transistors was investigated. Post-synaptic current was shown with tunable peak values, on-off ratio, and relaxation time.

Simultaneously Detecting Subtle and Intensive Human Motions Based on a Silver Nanoparticles Bridged Graphene Strain Sensor

There is a growing demand for flexible electronic devices. In particular, strain sensors with high performance have attracted more and more attention, because they can be attached on clothing or human skin for applications in the real-time monitoring of human activities. However, monitoring human-body motions that include both subtle and intensive motions, and many strain sensors cannot meet the diverse demands simultaneously. In this work, a silver nanoparticles (Ag NPs) bridged graphene strain sensor is developed for simultaneously detecting subtle and intensive human motions. Ag NPs serve as many bridges to connect the self-overlapping graphene sheets, which endows the strain sensor with many excellent performances. Because of the high sensitivity, with a large gauge factor (GF) of 475 and a strain range of >14.5%, high durability of the sensor has been achieved. Besides, the excellent consistency and repeatability of the fabrication process is verified. Furthermore, the model for explaining the working mechanism of the strain sensor is proposed. Most importantly, the designed wearable strain sensor can be applied in human motion detection, including large-scale motions and small-scale motions.

A Ferroelectric Thin Film Transistor Based on Annealing-Free HfZrO Film

A ferroelectric thin film transistor (Fe-TFT) based on annealing-free hafnium zirconium oxide (HfZrO) is demonstrated in this paper. Indium zinc oxide was used as channel semiconductor. The as-deposited 30-nm HfZrO film implemented as gate dielectric was proved to be crystallized with a mixture of monoclinic, tetragonal, and orthorhombic phases and showed ferroelectricity naturally. Thus, high temperature annealing process was avoided. The transfer characteristic of this Fe-TFT was demonstrated with operating voltage that was smaller than 3 V, memory window about 1 V, and small subthreshold slope (SS) about 82 mV/dec. The charge trapping phenomenon in this device was explored by characterizing the transfer curves with different ranges of gate voltages. This HfZrO-based device with low processing thermal budget and small SS has high potential for Fe-TFT memory which can be used in oxide semiconductor-based systems and applications.

Low-Voltage Unipolar Inverter Based on Top-Gate Electric-Double-Layer Thin-Film Transistors Gated by Silica Proton Conductor

In this letter, low-voltage unipolar inverter based on solid-state silica electric-double-layer (EDL) top-gate thin-film transistors was fabricated. A silicon oxide film deposited by the plasma-enhanced chemical vapor deposition method at room temperature was used as inorganic electrolyte insulator. Due to the formation of the EDL, the inverter can work at low voltages that are less than 1 V. The voltage transfer curves and the dynamic switching behaviors at different switching frequencies were investigated. The inverters can be integrated with low-voltage applications, such as biosensors, portable electronics, and synaptic devices, which work at low operation voltages and relatively low speeds.

Synaptic Computation Demonstrated in a Two-Synapse Network Based on Top-Gate Electric-Double-Layer Synaptic Transistors

In this letter, a two-synapse network with synaptic computation function is demonstrated. Solid-state electric-double-layer indium-zinc oxide-based synaptic transistors gated by silicon oxide electrolyte are used as artificial synapses. The short-term synaptic plasticity of the synaptic transistors is utilized to achieve high-frequency filter, processing frequency coding spike stimulus. The filtering characteristics of one synapse are controlled by the other one. Furthermore, we conducted synaptic computation in the two-synapse network, which demonstrates how synaptic transistors perform computational functions in neural networks.

Simulation of SiO2 etching in an inductively coupled CF4 plasma

Plasma etching technology is an indispensable processing method in the manufacturing process of semiconductor devices. Because of the high fluorine/carbon ratio of CF4, the CF4 gas is often used for etching SiO2. A commercial software ESI-CFD is used to simulate the process of plasma etching with an inductively coupled plasma model. For the simulation part, CFD-ACE is used to simulate the chamber, and CFD-TOPO is used to simulate the surface of the sample. The effects of chamber pressure, bias voltage and ICP power on the reactant particles were investigated, and the etching profiles of SiO2 were obtained. Simulation can be used to predict the effects of reaction conditions on the density, energy and angular distributions of reactant particles, which can play a good role in guiding the etching process.

Simulation and experimental verification of silicon dioxide deposition by PECVD

Deposition of silicon dioxide in high-density plasma is an important process in integrated circuit manufacturing. A software named CFD-ACE was used to simulate the mechanism of plasma in the chamber of plasma enhanced chemical vapor deposition (PECVD) system, and the evolution of the feature profile was simulated based on CFD-TOPO. Simulation and experiment of silicon dioxide that deposited in SiH4/N2O mixture by PECVD system was researched. The particle density, energy and angular distribution in the chamber were simulated and discussed. We also studied how the depth/width ratio affected the step coverage of the trench and analyzed the deposition rate of silicon dioxide on the feature scale. X-ray photoelectron spectroscopy (XPS) was used to analyze the elemental composition of thin films. Images of the feature profiles were taken by scanning electron microscope (SEM). The simulation results were in good agreement with experimental, which could guide the semiconductor device manufacture.

Novel memory devices based on nanostructured carbon materials

Nanostructured carbon materials, such as graphene and carbon nanotube, based novel memory devices are introduced in this paper. A dynamic synaptic device based on twisted bilayer graphene is showed enabling modulatable plasticity. Gate-controlled graphene-electrode resistive memory device is found out to have tunable SET window. Carbon nanotube based transistor is presented mimicking short-term memory of human brain. Peculiar memory characteristics of these devices are demonstrated and discussed, which may stimulate new inspiration for both nanomaterial based electronics and memory devices.