Near-infrared optical properties of CoSi2 thin films

Abstract

Transmission and reflection measurements in the energy range 0.5–1 eV have been performed on thin CoSi₂ films grown by molecular‐beam epitaxy on Si(111). For film thicknesses above 200 Å, the transmission factor decreases exponentially with film thickness, with an optical attenuation length of 180 Å nearly independent of photon energy. Deviations from this law for film thicknesses below 200 Å are explained by reflection effects. These data, supplemented by reflection measurements, can be fitted by theoretical calculations of the transmission and reflection factors, thus leading to the determination of the CoSi₂ optical indexes. The energy dependence of the real and imaginary indexes is found to be consistent with the Drude model. Some interesting aspects of this intraband absorption either in ultrathin films or at low temperature are presented.