Investigations on Structural, Optical and X-Radiation Responsive Properties of a-Se Thin Films Fabricated by Thermal Evaporation Method at Low Vacuum Degree

Amorphous selenium (a-Se) thin films with a thickness of 1200 nm were successfully fabricated by thermal evaporation at a low vacuum degree of 10-2 Pa. The structural properties involving phase and morphology showed that a-Se thin films could be resistant to 60 °C in air. Also, a transformation to polycrystalline Selenium (p-Se) was shown as the annealing temperature rose to 62 °C and 65 °C, with obvious changes in color and surface morphology. Moreover, as the a-Se transformed to p-Se, the samples' transmittance decreased significantly, and the band gap declined dramatically from 2.15 eV to 1.92 eV. Finally, the X-radiation response of a-Se was investigated as an important property, revealing there is a remarkable response speed of photogeneration current both X-ray on and X-ray off, with a requirement of only a very small electrical field.