Melnyk V. Tin influence on silicon nanocystalls formation in films of Si1-xSnx alloys and a-Si/Sn layered structures.

Crystallization of amorphous silicon caused by tin induced and laser irradiation stimulated in films of Si1-xSnx alloys and a-Si/Sn layered structures was investigated. The methods of Raman scattering, X-ray fluorescence microanalysis and Auger spectroscopy at ion etching was used. Lack of influence dispersively dissolved Sn atoms on thermal crystallization of amorphous Si has been shown. However, the presence of common interface amorphous Si - metallic Sn at temperatures above the tin melting point causes the transition of silicon from an amorphous to a crystalline state. This transition appears because of cyclic alternation of the formation and decomposition processes for "Si in Sn" solution. Solution formation is a Si-Sn eutectic creation based on Si, dissolved in Sn liquid. And solution decomposition is a Si crystals precipitation from eutectic. Because of these processes, Si crystals with size 2-8 nm are forming at the temperature range 300-400 ℃. Interface amorphous Si - metallic Sn may be realized as layered a-Si/Sn structures or as Sn microdroplets inside amorphous Si matrix by simultaneous deposition of these elements from the gas phase. The crystallization mechanism and its theoretical model has been suggested. It describes experimental results and confirms the ability of full Si transformation from the amorphous to the nanocrystalline state under adiabatic conditions. It was first detected the essential acceleration of metal induced crystallization of amorphous silicon for a-Si/Sn/a-Si film structures while heating it by laser irradiation with power over 104 W/sm2, comparing to film heating without irradiation. The laser irradiation using for simultaneously controlling condition for metal induced crystallization of amorphous silicon and measuring the parameters of formed nanocrystals has been shown.