The Switching mechanism of a-Si memristor is based on the electrochemical metallization (ECM) effect. After application of a constant bias, the metal ions oxidized on the surface of the electrode migrates to the amorphous silicon layer, which not only lead to the resistive switching behavior, but also the change of optical parameters of switching material. Here, a novel film memristor with optical readout functionality has been set up by combining a silicon prism with Ag/a-Si/Al structure. The attenuation of the reflected light from the device dependence on surface plasmon resonance (SPR) effect on interface of silver layer which is sensitive to the refractive index of the a-Si layer. The change of the reflectance spectrum of the memristor under different bias voltages was simulate by means of finite-difference time-domain (FDTD) method, and the influence of the thickness of the amorphous silicon film and the silver film on the intensity of the reflected light was analyzed.
Vanadium oxide (VOx) thin films were prepared on unheated glass substrate by pulsed dc reactive magnetron sputtering using different pulse frequency. Field emission scanning electron microscopy (FESEM), x-ray photoelectron spectroscopy (XPS) and spectroscopic ellipsometry (SE) measurements were made on the deposited VOx films to characterize the microstructure, composition and optical properties, respectively. It was found that under the same discharge power and argon-oxygen atmosphere, with the increase of pulse frequency, the vertical column-like structure in the films will gradually disappear and the ratio of high-valent VOx to low-valent VOx will obviously elevate. Optical parameters of the VOx films have been obtained by fitting the ellipsometric data (Ψ andΔ) using the Tauc-Lorentz dispersion relation and a multilayer model (air/roughness layer/VOx/glass). The results demonstrated that pulse frequency plays a critical role in determining the transmittance, refractive index, extinction coefficient and optical band gap etc. The correlations between the microstructure, composition, optical properties and pulse frequency are also given by our experiment results. And the mechanisms for the evolution of the microstructure, composition and optical properties with pulse frequency have been discussed. Overall, due to the pulse frequency had a great effect not only on the growth characteristics but also on the optical properties of the VOx films, thus through variation of the pulse frequency during deposition which provide a convenient and efficient approach to control and optimize the performances of the VOx films.
Vanadium oxide (VOx) films were deposited onto well cleaned glass substrates by bipolar pulsed reactive magnetron
sputtering at room temperature. Dependence of the structure, composition, optical and electrical properties of the films
on the pulsed power’s duty cycle has been investigated. The results from the X-ray diffraction (XRD) analysis show that
there was no remarkable change in the amorphous structure in the films with duty cycle can be observed. But chemical
analysis of the surface evaluated with x-ray photoelectron spectroscopy (XPS) indicates that decrease the duty cycle
favors to enhance the oxidation of the vanadium. The optical and electrical properties of the films were characterized by
spectroscopic ellipsometry and temperature dependent resistivity measurements, respectively. The evolution of the
transmittance, optical band gap, optical constants, resistivity and temperature coefficient of resistance (TCR) of the
deposited films with duty cycle was analyzed and discussed. In comparison with conventional DC sputtering, under the
same discharge atmosphere and power level, these parameters of the VOx films can be modified over a broad range by
duty cycle. Therefore adjusting the duty cycle during deposition, which is an effective way to control and optimize the
performances of the VOx film for various optoelectronic devices applications.
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