DC Conductivity of Composite Silicon Thin Films

Amorphous-nano-crystalline silicon composite thin films (a-nc-Si:H) samples were synthesized by Plasma Enhanced Chemical Vapor Deposition technique. The measurement of DC conductivities was accomplished using Dielectric spectroscopy (Impedance Spectroscopy) in wide frequency and temperature range. In analysis of impedance data, two approaches were tested: the Debye type equivalent circuit with two parallel R and CPEs (constant phase elements) and modified one, with tree parallel R and CPEs including crystal grain boundary effects. It was found that the later better fits to experimental results properly describes crystal grains dielectric effect and hydrogen concentration indicating presence of strain. The amorphous matrix showed larger resistance and lower capacity than nano-crystal phase. Also it was found that composite silicon thin film cannot be properly described by equivalent circuit only with resistors and constant phase elements in serial relation.