Charge trapping and ac-electrical conduction in nanocrystalline erbium manganate film on Si substrate

Thin film of nanocrystalline ErMnO3 was prepared by thermal annealing of Er-Mn oxide film deposited on p-Si(1 0 0) substrates. The X-ray fluorescence (XRF) and X-ray diffraction (XRD) technique were used to investigate the structure of the prepared Er-Mn oxide films. XRD study shows that films pre-annealed at 400 deg. C have amorphous structure and they were crystallised forming ErMnO3 compound under pre-annealing at 800 deg. C or more. Moreover, in the prepared Er-Mn oxide films, Er oxide or Mn oxide cannot be crystallised each alone, but instead they interact chemically with each other forming ErMnO3 compound. A comprehensive study on electrical properties was carried on. The ac-conductance and capacitance as a function of gate voltage, frequency, and temperature were studied on samples made in form of metal/oxide film/Si MOS devices. The fixed charge and interface state densities were determined and their variation with annealing process was studied and explained. It was found that the 'correlated barrier hopping' CBH model controls the frequency dependence of the ac-conductivity, while Kramers-Kronig (KK) relations explain the frequency dependence of the relative permittivity. The parameters of CBH model were determined showing that the ac-conduction is realised by bipolaron hopping mechanism. dc conduction properties were also studied through the voltage and temperature dependence of the leakage dc-current density. The obtained dc-data follow a space charge limited current (SCLC) mechanism