Effects of composition and substrate temperature on the a.c. properties of co-evaporated Mn/SiOx thin films

Capacitance, a.c. conductance and loss factor have been measured in Cu-Mn/SiOx-Cu sandwich structures with compositions 1, 3, 5 and 10 at% Mn in the frequency range 10–106 Hz between temperatures of 110 and 500 K. The capacitance has a weak minimum at 1.0 MHz for all temperatures, whilst the a.c. conductance increases between four and eight orders of magnitude for temperatures of 150 and 473 K, respectively. Various a.c. conduction models have been considered, and it has been concluded that correlated barrier hopping best describes the results. The Goswami-Goswami model was used to describe the variation of loss factor with temperature and composition.