Adsorption induced changes in the conductivity of amorphous Ge films

In order to understand the considerable irreversible ageing, annealing and adsorption effects on the various physical properties of amorphous (a-) Ge films, the effect of adsorption of N2, O2, Ar and air on the transport properties of obliquely deposited a-Ge films has been studied. The resistivity increases parabolically with time for about 30 minutes and thereafter increases slowly. Similarly, the resistivity rises rapidly with increasing pressure, upto ~10-2 Torr. The largest effect is observed with oxygen. The resistivity changes are drastically enhanced with increasing angle of oblique deposition. The temperature dependence of the resistivity is qualitatively similar for films with and without adsorption effects. This paper will discuss the various observations and their interpretation in terms of adsorption induced microstructural rearrangement of anisotropic films