A study on photo-induced crystallization in Ga10Se78Tl12 thin films

Abstract

This paper reports the photo-induced crystal- lization in glassy Ga10Se78Tl12 thin films. The glassy na- ture of the bulk material was confirmed by non-isothermal differential scanning calorimetry measurements. The pho- to-induced crystallization in Ga10Se78Tl12 films was done by exposing to light (using 2000 W tungsten lamp) at various illumination times under the fixed ambient tem- perature at 358 K. Virgin and photo-induced Ga10Se78Tl1 thin films were characterized by X-rays diffraction, scan- ning electron microscopy, optical and electrical measure- ments. The photo-induced crystallization is associated to the change in structure of Ga10Se78Tl12 thin films which initiated the significant change in the optical constants. The detailed examination of the optical absorption results indicated that the optical transition was indirect. The op- tical band gap of Ga10Se78Tl12 thin films were decreased while the absorption and the extinction coefficients in- creased with the increase of illumination time. From dark conductivity results, the dark conductivities of thin films continuously heightened and the activation energy turned to be lower as increasing the illumination time. The low- ering in optical band gap and activation energy might be due to the occurrence of photo crystallization with the in- crement of illumination time.