Stretchable Transistor-Structured Artificial Synapses for Neuromorphic Electronics.

Stretchable synaptic transistors, a core technology in neuromorphic electronics, have functions and structures similar to biological synapses and can concurrently transmit signals and learn. Stretchable synaptic transistors are usually soft and stretchy and can accommodate various mechanical deformations, which presents significant prospects in soft machines, electronic skin, human-brain interfaces, and wearable electronics. Considerable efforts have been devoted to developing stretchable synaptic transistors to implement electronic device neuromorphic functions, and remarkable advances have been achieved. Here, this review introduces the basic concept of artificial synaptic transistors and summarizes the recent progress in device structures, functional-layer materials, and fabrication processes. Classical stretchable synaptic transistors, including electric double-layer synaptic transistors, electrochemical synaptic transistors, and optoelectronic synaptic transistors, as well as the applications of stretchable synaptic transistors in light-sensory systems, tactile-sensory systems, and multisensory artificial-nerves systems, are discussed. Finally, the current challenges and potential directions of stretchable synaptic transistors are analyzed. This review presents a detailed introduction to the recent progress in stretchable synaptic transistors from basic concept to applications, providing a reference for the development of stretchable synaptic transistors in the future.

The Stability of Metallic MoS2 Nanosheets and Their Property Change by Annealing.

Highly pure 1T MoS2 nanosheets were grown at 200 °C by a hydrothermal process. The effects of mild annealing on the structural and physical properties of the MoS2 were studied by heating the nanosheets in air and vacuum up to 350 °C. It was found that the annealing leads to an increase in resistivity for the nanosheets by 3 orders of magnitude, the appearance of two absorption bands in the visible range, and a hydrophilic to hydrophobic change in the surface wetting properties. Monitoring of the annealing process by Raman spectroscopy indicates that the material property changes are associated with a 1T to 2H MoS2 phase transition, with activation energies of 517 meV in air and 260 meV in vacuum. This study provides another way to control the electrical, optical, and surface properties of MoS2 nanosheets for fulfilling the needs of various applications.

Morphology and Microstructure of As-Synthesized Anodic TiO2 Nanotube Arrays.

The as-grown structure of electrochemically synthesized titania nanotube arrays is investigated by scanning electron microscope (SEM) in combination with transmission electron microscope (TEM) as well as X-ray diffraction (XRD). The analysis reveals a preferred growth direction of the nanotubes relative to the substrate surface and the well control on the nanotube arrays morphology. The crystal structure of the anatase phase is detected and exists in the tube walls without any thermal treatment, which makes it possible to realize the application of as-formed TiO2 nanotubes avoiding the degradation of the nanotube structures when sintering. In addition, a new growth, layered model of the anodic TiO2 nanotubes is presented to obtain further understanding of the growth mechanism.

Study on optical constants of ITO:Ag nanocompsite films.

Indium tin oxide (ITO) thin films doped with a volume ratio of 0.3% Ag were prepared by sputtering and subsequently annealed in temperatures of 200, 260, 300, 360, and 400 degrees C. The annealed films show increased transmittance in the visible wavelength range. The refractive index n and extinction coefficient k were extracted from simulating the transmittance spectra by using spectroscopic ellipsometry analysis method. The n values apparently increased in the whole wavelength range, but the k values were found to have almost no change in the near ultraviolet region after Ag doping. It is, therefore, proposed that the ITO:Ag combined with an ITO multilayer structure can be applied in special optical devices.

[Model building and optimization of ultrathin silver films by spectroscopic ellipsometry].

Ultrathin silver films (4.0, 6.2, 12.5, 26.2, 30.0 and 40.6 nm) were prepared by direct current sputtering deposition. The thicknesses and optical constants of the films were studied by spectroscopic ellipsometry. The Drude model combined with Lorentz Oscillator model was used in the optimization of the ellipsometric data. The results show that surface plasma resonance absorption (SPR) peaks appear in the spectra of extinction coefficient k for samples 1, 2, 3 and 4. The peak shifts to shorter wavelength with the reduction in film thickness. The wavelengths of the SPR for different films were calculated by the SPR theory and also compared with the experimental data.