1/f- and random telegraph noise of thermoelectric CoSb3 skutterudite thin films

We present resistance, Hall effect and fluctuation spectroscopy measurements on thermoelectric CoSb₃ skutterudite thin films in a broad temperature range. Mott variable range hopping is discussed as the dominating transport process at low temperatures. Noise measurements provide further insight into the electronic transport properties. While 1/f-like noise dominates over nearly the entire temperature range, thermally-activated Lorentzian-type spectra are observed in a narrow temperature region around 150 K. Characteristic values of the activation energy are determined to be of the same order of magnitude as the energy gap of CoSb₃. We suggest excitations of defect states between valence and conduction band to be the underlying process for the observed noise behavior and discuss the possible exchange of electrons between donor traps and the rest of the conducting media.