Effect of the amorphous germanium film thickness on the process of gold-induced crystallization
A.O. Zamchiy1, V.A. Nepomnyashchikh2,3, V.O. Konstantinov1, E.M. Starinskaya1, V.A. Volodin3,4, E.A. Baranov1
1Kutateladze Institute of Thermophysics SB RAS, Novosibirsk, Novosibirsk, Russia
2Kutateladze Institute of Thermophysics SB RAS, Novosibirsk, Russia
3Novosibirsk National Research State University, Novosibirsk, Russia
4Rzhanov Institute of Semiconductor Physics SB RAS, Novosibirsk, Russia
Keywords: thin films, gold-induced crystallization, polycrystalline germanium, hillocks
Abstract
Results of an experimental study of gold-induced crystallization of thin films of amorphous germanium (a-Ge) are reported. The Raman spectroscopy and optical microscopy are applied to study the influence of the initial thickness of the a-Ge film on the morphology of the material obtained by means of annealing of bilayer Au/a-Ge structures. The a-Ge/Au thickness ratios equal to 1.1 and 2.3 are considered. Low-temperature annealing in quartz/Au/a-Ge samples is performed in a high-vacuum atmosphere (10-4 Pa) at a temperature of 300 °С for 24 h. The Raman spectroscopy results show that annealing of the samples results to complete crystallization of a-Ge with formation of polycrystalline germanium (poly-Ge) in both lower and higher layers of the samples. For the sample with a-Ge/Au = 2.3, a continuous poly-Ge film is obtained on the substrate owing to implementation of the layer exchange mechanism. In this case, poly-Ge hillocks are formed in the upper layer of the sample due to a-Ge crystallization in the presence of Au. For the sample with a-Ge/Au = 1.1, a non-continuous poly-Ge film with a coverage ratio of 30% is formed in the lower layer. The poly-Ge material is formed in the upper layer owing to the processes of “explosive” crystallization and also secondary crystallization induced by Au.
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