Effects of film thickness on microstructure and electrical properties of the pyrite films

The cubic FeS2 (pyrite) films with thickness in 70–600 nm were prepared by sulfurizing iron films at 673 K. The microstructure, electrical conductivity and carrier behavior were investigated. Fine and uniform FeS2 crystallites form in sulfurizing process. With film thickness increasing up to 300 nm, FeS2 crystallite size decreases and maintains roughly constant as film thickness over 300 nm. There is significant lattice distortion for the films with 130–300 nm in thickness. The conductivity shows a maximum in the film 130 nm in thickness. The carrier concentration generally decreases with film thickness. The carrier mobility increases with film thickness increasing from 70 to 300 nm and decreases as film thickness greater than 300 nm. The changes of the density of crystal defects, level of phase transformation stress and integrity of film bulk can be responsible for the changes of the electrical properties with film thickness.