Pyrite FeS2 films obtained by sulphuration of iron pre-deposited films

FeS2 thin films crystallised in the cubic pyrite-type structure have been obtained by sulphuration of iron pre-deposited films. The iron films have been sulphurated at Ta=823 K for ta=6 h. The lattice constant deduced from XRD measurements is a=5.42 Å. The binding energy values measured by XPS of the S 2p3/2 and Fe 2p3/2 are 162.3 and 707.12 eV, respectively. All these results are in good agreement with reference data. Scanning electron study shows that the grains are as thick as the films, however, the surface visualisation put in evidence that the crystallite sizes are roughly distributed in two distributions, the first with an average size of about 150 nm, the other one being about 500 nm. Such large distribution in the crystallite size justifies that the barrier height, which controls the conductivity of the films varies from one point to another one. Moreover, a high density of impurity states is present in the grains of the films. All this justifies the high carrier density and the small carrier mobility measured in the films.