Electrical properties of antimony sulphoiodide (SbSI) thin films

Abstract

Electrical conduction in Ferroelectrics has several special features which are primarily associated with polarization, phase transitions and domain structures. The majority of the reported works on conduction processes in ferroelectrics have been confined to either room temperature or above. There is very little reported data available on low temperature conduction processes in ferroelectrics probably due to the high impedance of the samples. However, Ferroelectrics in thin film form can provide an ideal alternative due to their relatively low impedance. In this paper, we report the electrical properties of SbSI thin films. The investigations were performed interms of dc conductivity and thermoelectric power in the temperature range 80–400K and 300–450K respectively on a large number of films with various thicknesses in the range of 0.3μm to 1.0μm. SbSI was chosen as the ferroelectric material due to its several interesting ferroelectric and semiconducting properties and also due to its convenient transition point of 20°C, which facilitates the measurements both in ferroelectric and paraelectric phases. The d.c. conductivity studies performed on a Au-SbSI-Au sandwich structures indicated ohmic conduction in the low fields (V < IV), and Space charge limited conduction (SCLC) in the high field region (V > 2V). Analysis of the SCLC indicated an discrete trap distribution in the forbidden gap of SbSI. The low temperature conductivity data was found to be in good agreement with tunnel hopping mechanism. The measured conductivity exhibited a kink around the transition point (20°C) of SbSI confirming ferroelectricity in SbSI films. The calculated activation energies both in ferroelectric and paraelectric phases were found to be thickness dependent. The thermoelectric power in SbSI films indicated holes as the majority carriers and the temperature dependence of thermo ε.m.f indicated polaronic conduction in the paraelectric phase.