Physical properties and inversion of conductivity type in nanocrystalline PbTe films

This work is concerned with the effect of the nanostructure on the electrical conductivity of n-type In-doped PbTe thin films. Nanostructured thin films were prepared by varying the rate of nucleation as a function of the nature and temperature of the substrates. On low-temperature substrates, the increased rate of nucleation and the limited mobility of the atoms give rise to a nanostructured deposit with a 50 nm grain size. The broken bonds at the grain boundaries generate acceptor states in n-type films, capture electrons from the interior of the grains and give rise to p-type inversion layers between adjacent grains. In the nanostructured n-type films with the high density of grain boundaries, thermally activated hole conductivity becomes dominant and leads to its inversion from n to p type. The experimental results confirm the physical model put forward by Neustroev and Osipov [L. N. Neustroev and V. V. Osipov, Sov. Phys. Semicond. 20, 34 (1986)] regarding the creation of inversion channels (p-type co...