STRUCTURAL, OPTICAL AND ELECTRICAL-PROPERTIES OF POLYCRYSTALLINE IRON PYRITE LAYERS DEPOSITED BY REACTIVE DC MAGNETRON SPUTTERING

Thin iron disulphide pyrite (FeS2) films (5 - 100 nm) were prepared by reactive d.c. magnetron sputtering from an iron target in an Ar/H2S atmosphere. Optimum deposition was obtained with a sputtering power of 100 W in an 80% H2S gas mixture at a total pressure of 5 Pa. Iron pyrite films were successfully deposited on different glass substrates, at substrate temperatures up to 350-degrees-C. Higher temperatures led to sulphur loss of the films. X-ray diffraction measurements have shown that the films are polycrystalline with a grain size up to 50 nm. Rutherford backscattering analysis yielded an overall stoichiometry of FeS1.95 in the best films. From the optical transmission and reflection an optical absorption coefficient of 5 x 10(5) cm-1 for lambda < 560 nm was calculated. The films show p-type conductivity. A hole concentration up to 1 x 10(20) cm-3 and a mobility up to 25 cm2 V-1 s-1 at room temperature was determined by Hall measurements. The conductivity type is also supported by UV photoelectron spectroscopy where the position of the Fermi level was found to be very close to the valence band edge.