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

The ac and dc conductivities (sigma(ac) and sigma(dc)) 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: sigma(ac) alpha omega(s)(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 (epsilon') loss factor (epsilon'') and loss tangent (tan delta) together with the Cole-Cole diagrams and the optical (epsilon(infinity)) and static (epsilon(s)) dielectric constants for a-SeSm0.005 films are given and discussed.