Annealing crystallization of a-Ge/Al/Si and a-Ge/Si thin films

This work describes the temperature-induced crystallization of amorphous Ge (a-Ge) as a function of the thickness of the a-Ge films (in the 12-2600 nm range), which were deposited both onto c-Si substrates and c-Si substrates covered with aluminium. After deposition, the samples were submitted to cumulative thermal annealing treatments. It is shown that the temperature of crystallization depends on the thickness of the a-Ge films and to the presence (or not) of the Al layer. For an annealing temperature (T-a) of similar to 700 degrees C, for example, the Raman spectra of films thinner than similar to 1000 nm and deposited onto c-Si substrates are completely dominated by the sharp phonon mode of crystalline Si. Films with thicknesses equal to 300, 1000 and 2600 nm, deposited onto Al/c-Si, and treated at T-a = 600 degrees C, on the other hand, clearly display two additional peaks at 405 and 490 cm(-1). They correspond to the Raman modes of Si-Ge and Si-Si modes, suggesting the formation of a SiGe alloy during the thermal anneal of the films. (c) 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.