Spin-coated As33S67−xSex thin films: the effect of annealing on structure and optical properties

Abstract

The spin-coating method was used for the preparation of amorphous chalcogenide As33S67−xSex films, where x=0, 17, 33.5, 50 and 67 at.%. The films were stabilized in a vacuum furnace at 70°C for 10 hours. The compositions of the films, established by Energy-Dispersive X-ray analysis, were similar to the composition of the glass used for the preparation of the solutions. The optical transmission measurements indicated that the optical band gap decreases with increasing Se-content in the films. Raman spectroscopy showed the films structure i.e. As–S bonds at 344 and 376cm−1, S-rings at 495cm−1 and appearance of As–Se bonds at 225cm−1, Se chains at 254cm−1 and S–Se bonds at 416cm−1 with increasing Se-content. MIR transmission spectra revealed the presence of solvent residua in spin-coated films i.e. N–H bonds at 3395–3300cm−1, C–H bonds at 2980–2850cm−1. Further annealing of the films (150°C, 0–60min) caused decrease of N–H and C–H stretching vibration intensities. Raman spectra showed that the annealed films were more structurally ordered in contrast to the as-deposited material. The shift of the films optical absorption edge to lower energies was observed during annealing procedure. Potential application of the films is expected in optical recording and new types of memories.