Investigations of the conduction mechanism and relaxation properties of semiconductor Sm doped a-Se films

Abstract

The ac and dc conductivities (σac and σdc) of amorphous semiconductor Sm doped Se (namely, SeSm0.005) films, prepared by thermal evaporation, were measured under vacuum in a wide range of frequency and temperature. The ac conductivity versus frequency plots were analysed by considering a power law: σac ∝ ωs (s ⩽ 1). A comparison between values of the index s with those numerically calculated from different conduction models reveals that correlated barrier hopping (CBH) is a fairly good model to describe the dominant ac conduction mechanism. The concept of the Meyer–Neldel (MN) rule in the expression of the relaxation time is considered for both ac and dc experimental data. The validity of the CBH model based on the MN (normal and inverted) rule is studied and discussed. Besides, results of the real dielectric constant (ε′), loss factor (ε′) and loss tangent (tan δ) together with the Cole–Cole diagrams and the optical (ε∞) and static (εs) dielectric constants for a-SeSm0.005 films are given and discussed.