Study of the phase transition in heteroepitaxially grown films of αSn by Raman spectroscopy

The transition in heteroepitaxially grown films of tin from the semiconducting (α) phase to the metallic (β) phase depends on the film thickness and the surface orientation. Investigations of the optical Raman phonon of α-Sn demonstrate that αSn films grown on InSb(001) surfaces show a sharp α ↔ β transition at a temperature T^* which depends on the film thickness. For a film thickness of less than 60 nm the transformation occurs at T^* = 115°C, which is much higher than the bulk T^* value of 13.2°C. Evidence for the formation of β-Sn on (110) and (111) surfaces is given from Raman and reflection high energy electron diffraction investigations.