Study on Pressure Working Time and Releasing Rate for Phase Transformation of Ge

Abstract

The direct transformation from Ge-I to Ge-III has been investigated by Raman spectroscopy measurements. The Ge sample, which consisted of the Ge-I phase at atmospheric pressure, did not transform to another phase under a pressure of 6 GPa for 10 days. After the slow release of pressure at a rate of 1 GPa/h to atmospheric pressure, a peak around 302 cm—1 and two indistinct peaks around 274 and 285 cm—1 have been noted. The sample was thought to consist of a mixture of Ge-I, wurtzite, and Ge-III phases. After 4 h, the peak corresponding to Ge-III almost disappeared. The presence of both Ge-I and Ge-III phases has also been noted in photo-oxidized Ge nanocrystalline films using ultraviolet light exposure.