The structural features of dimorphite thin films grown by thermal evaporation and cathodic magnetron sputtering

Abstract

Dimorphite (As₄S₃) is a rare arsenic sulfide compound of growing interest for optoelectronic applications. The present work reports the structural characterization of two types of dimorphite thin films prepared by thermal evaporation of As₄S₃ powder and RF magnetron sputtering from a pressed As₄S₃ powder target. The films obtained via thermal evaporation in vacuum ~10-5 Torr have been grown onto quartz or titanium (Ti) substrates using a quartz crucible, heated by a tungsten coil. The velocity of film growth was controlled varying the temperature of the crucible from 120 to 180 oC, which allowed to vary the deposition rates in the range of 0.2÷8 μm/h. The set-up allowed us to grow dimorphite layers with different thickness (0.1÷10 μm) without breaking the vacuum. It was established that As4S3 sublimes at a pressure of 10-5 Torr and temperature around 120 oC. Shown by scanning electron microscopy (SEM), the films obtained via sublimation are fibrillar with a high porosity. The fibrils are randomly distributed and are around 1-2 μm in length. At advanced crucible temperatures dimorphite evaporates and the grown films are dispersive and homogeneous.