Structural and optical properties of photocrystallized Se films

Structural and optical properties of photocrystallized Se films have been studied using x-ray diffraction (XRD), spectroscopic ellipsometry (SE), and ex situ atomic force microscopy (AFM) techniques. The amorphous (a-) Se films used are deposited by vacuum evaporation on glass substrates at 300 K. Photocrystallization is performed using a linearly polarized 488.0-nm line of an Ar laser. For comparison, thermocrystallized films at 100 ^∘{}C for 1 h in a dry N₂ atmosphere are studied. The XRD pattern shows that the photocrystallized film is characterized by a polycrystalline structure with which the (1010) plane is preferentially grown. The SE data also give that the c axis is perpendicular to the direction of the polarization of the illuminating light. The thermocrystallized film, on the other hand, shows an unoriented polycrystalline nature. The dielectric functions for these two films are considerably smaller than those for a bulk, single-crystalline Se. This is mainly due to the roughened surfaces of the photo- and thermocrystallized films. The change in surface morphology after photo- and thermocrystallization is independently assessed by the AFM.