Formation mechanism of Ge nanocrystals embedded in SiO2 studied by fluorescence x-ray absorption fine structure

This paper reports that the Ge nanocrystals embedded in SiO2 matrix are grown on Si（100） and quartz-glass substrates, and the formation mechanism is systematically studied by using fluorescence x-ray absorption fine structure （XAFS）. It is found that the formation of Ge nanocrystals strongly depends on the properties of substrate materials. In the as-prepared samples with Ge molar content of 60%, Ge atoms exist in amorphous Ge （about 36%） and GeO2 （about 24%） phases. At the annealing temperature of 1073 K, on the quartz-glass substrate Ge nanocrystals are generated from crystallization of amorphous Ge, rather than from the direct decomposition of GeO2 in the as-deposited sample. However, on the Si（100） substrate, the Ge nanocrystals are generated partly from crystallization of amorphous Ge, and partly from GeO2 phases through the permutation reaction with Si substrate. Quantitative analysis reveals that about 10% of GeO2 in the as-prepared sample are permuted with Si wafer to form Ge nanocrystals.

Formation mechanism of Ge nanocrystals embedded in SiO2 studied by fluorescence x-ray absorption fine structure

This paper reports that the Ge nanocrystals embedded in SiO$_{2}$matrix are grown on Si(100) and quartz--glass substrates, and theformation mechanism is systematically studied by using fluorescencex-ray absorption fine structure (XAFS). It is found that theformation of Ge nanocrystals strongly depends on the properties ofsubstrate materials. In the as-prepared samples with Ge molar contentof 60{%}, Ge atoms exist in amorphous Ge (about 36{%}) and GeO$_{2}$ (about 24{%}) phases. At the annealing temperature of 1073 K, onthe quartz--glass substrate Ge nanocrystals are generated fromcrystallization of amorphous Ge, rather than from the directdecomposition of GeO$_{2}$ in the as-deposited sample. However, onthe Si(100) substrate, the Ge nanocrystals are generated partly fromcrystallization of amorphous Ge, and partly from GeO$_{2}$ phasesthrough the permutation reaction with Si substrate. Quantitativeanalysis reveals that about 10{%} of GeO$_{2}$ in the as-preparedsample are permuted with Si wafer to form Ge nanocrystals.