On the Molecular, Crystal Structure and Optical Properties of Sodium Tungstate Doped PVA Composite Films for Fabrication of Ag/Na2WO4 Doped PVA/p-Si/Al Memory Devices

Abstract

Herein, sodium tungstate doped PVA composite films are manufactured using spin-coating to investigate the structural and optical properties. The molecular structure of the fabricated films and the utilized PVA and Na₂WO₄ powder were characterized by FT-IR and XPS, and then the crystal structure was investigated by X-ray diffractometry (XRD). The investigated analyzed cell parameters of Na₂WO₄ in powder form have a cubic unit cell with a = 9.12974 and space group Fd\(\overline{3 }\)m. The optical absorption coefficient based on Transmission and Reflection is evaluated to investigate the optical transition of the fabricated Na₂WO₄ doped PVA. The absorption coefficient was improved after the additives of Na₂WO₄ in the ultraviolet region. The characteristic transition of the pure PVA films was indirect, and the Na₂WO₄ doped PVA films were directly transitioned with different energy gaps (4.660, 3.879 and 4.143 eV). The nonlinear Cauchy and Sellimeier models were used to analyze and simulate observed optical dispersion coefficients. The estimated oscillator energy of 8.575, 6.908, and 6.844 eV for the fabricated PVA films was indirect, and the Na₂WO₄ doped PVA films. Moreover, anomalies hysteric (I–V) cyclic curves are recorded for the Ag/Na₂WO₄@PVA(1)/p-Si/Al devices. The fabricated Ag/Na₂WO₄@PVA(1)/p-Si/Al devices were examined by oscillating applied potential according to the samples’ conductance and series resistances at different frequencies (f = 5 and 10 kHz), and showed a stable window area and three different State-Levels dependent on frequency 5 and 10 kHz.