Low-temperature spray-pyrolysis of FeS$_2$ films and their electrical and optical properties

Iron disulfide (FeS$_2$) films with a wide range of electrical resistivities 100 $\Omega$ cm $\le\rho\le$ 800 k $\Omega$ cm, a high adhesion to the substrate, and a resistance to aggressive media have been prepared by the spray pyrolysis of aqueous solutions of the salts FeCl$_{3}$ $\cdot$ 6H$_{2}$O and (NH$_{2}$)$_{2}$CS at low temperatures in the range 150 $\le T_{S}\le$ 400$^\circ$C. It has been found that the FeS$_2$ films have a high transmittance $T\approx$ 60–70% and are characterized by a sharp transmission edge. It has been shown that the optical band gap for direct ($E_{g}^{\operatorname{op}}$ = 2.19–2.78 eV) and indirect ($E_{g}^{'\operatorname{op}}$ = 1.26–1.36 eV) optical transitions depends on the conditions of film preparation.