Low temperature electrical conductivity and seebeck coefficient of nanostructured CuSe thin films with Ga addition

Abstract

Electrical conductivity and Seebeck coefficient of nanostructured Ga added p-type CuSe thin films are investigated in the temperature range 6–300 K. The films prepared by vacuum co-evaporation method and characterized by various tools like X-ray diffraction, scanning electron microscopy and energy dispersive analysis of X-rays, for their structural, morphological and compositional studies, have agglomerated grains forming particles of size ranging from about 24 nm to 121 nm and lattice constants a = 4.046 Å and c = 1.717 Å. The analysis of conductivity data suggests Mott's variable range hopping in the range 10–120 K, Seto's grain boundary effect in 120–195 K and Arrenhius' thermal activation in 195–300 K, while Seebeck coefficient data corroborates well with Hall and hot probe observations of p-type conductivity. These films have high conductivity of 903 ± 3% S/m at 300 K with the Fermi level lying ∼6 meV above valence band maximum (VBM) within a direct band gap of 1.99 ± 0.03 eV.