Study on pressure working time and releasing rate for phase transformationof Ge

The direct transformation from Ge-I to Ge-III has been investigated by Rama n spectroscopy measurements. The Gc sample, which consisted of the Ge-I pha se at atmospheric pressure. did not transform to another phase under a pres sure 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 indistinc t peaks around 274 and 285 cm(-1) have been noted. The sample was thought t o consist of a mixture of GU-I, wurtzite, and Gc-III phases. After 4 h, the peak corresponding to Ge-III almost disappeared. The presence of both Ge-I and Gc-III phases has also been noted in photo-oxidized Ge nanocrystalline films using ultraviolet light exposure.