EXAFS measurements for liquid Ge-Si alloys

EXAFS measurements around the Ge-K edge have been carried out for liquid Ge -Si alloys for the first time to investigate the local structure around a G e atom. To perform the EXAFS measurements for the liquid alloys with high m elting temperatures, a new sapphire cell have been developed. The measureme nts were carried out for the liquid alloys from 10% to 60% of Si and the cr ystalline ones from 10% to 70% of Si as a reference. EXAFS oscillations, x( k), are observed even at 1480 degreesC for liquid Ge0.4Si0.6. The position of the first peak in the radial distribution function obtained from Fourier transform of x(k) is shifted towards smaller distance for liquid and cryst alline alloys with increasing Si concentration. The results of a curve-fit analysis in a harmonic approximation show that Ge-Ge and Ge-Si bonds in the liquid alloys become long with increasing Si concentration while those bec ome slightly short in the crystalline ones.