Crystallization of amorphous Se<inf>80</inf>Te<inf>20</inf> alloy thin films

Electron-beam-induced crystallization of amorphous thin films of an Se80Te20 alloy has been studied in the electron microscope. Se80Te20 alloy thin films vacuum deposited onto glass substrates at room temperature are initially amorphous. It was reported earlier that the amorphous alloy crystallized instantaneously (explosive crystallization) at room temperature in the presence of an intense electron beam. Therefore, to check the beam sensitivity of the amorphous alloy films electron microscopy studies were carried out at constant temperature (from 173 to 295 K) as a function of time using a cryo specimen holder. The crystallization occurs-first by formation of nuclei which grow subsequently and coalesce, forming well-defined grain boundaries. These films were noticed to be resistant to spontaneous crystallization, in that no isothermal growth was observed even at room temperature in the absence of the electron beam. There is no specific crystallization temperature as has been claimed earlier. The grains before coalescence are single crystals and have bright and dark contours indicating internal stress in the grains, which disappear as the stress is relieved at higher temperatures. The crystallization time is a function of temperature, decreasing with increasing temperature.