A transmission electron microscope study of metal/chalcogenide amorphous thin films

Thin bilayer films of Cu/a-GeSe2 and Ag/a-GeSe have been studied in the transmission electron microscope (TEM) for different metal concentrations. It has been observed that samples of Cu/a-GeSe2 crystallise locally when the electron beam is fully focused in a particular region. It is also found that it is possible to pattern regions of crystallized and non-crystallized material. The increase in copper concentration in Cu/a-GeSe2 samples increases the sensitivity of these thin films to the electron beam. In the case of Ag/a-GeSe samples, we have observed that electron beam irradiation results in the migration of silver away from electron irradiated regions. The depletion of silver has been confirmed by energy dispersive X-ray (EDX) microanalysis. It has been observed that silver tends to accumulate in the surrounding non-irradiated regions forming dendritic silver filaments, the number and velocity of formation of these filaments increases with increase in electron dose. The phenomenon is fully reversible and by placing the electron beam on a silver filament, it is possible to observe how the filament dissolves to leave a region depleted of silver. Additionally, small particles of nanometric size have been observed to grow naturally on Ag/a-GeSe thin films on samples supported on NaCl and silicon substrates. # 2004 Published by Elsevier B.V.