荧光EXAFS研究镶嵌在SiO2中的Ge纳米晶的局域结构

用荧光扩展X射线吸收精细结构(EXAFS)研究了磁控溅射法制备的镶嵌在SiO2中的Ge纳米晶的局域结构.结果表明,在Ge的摩尔分数为25%和60%的初始样品中,Ge原子主要是以非晶GeO2和Ge物相存在,其中在Ge的摩尔分数为25%的样品中,以GeO2物相为主.经1073 K退火后,样品中生成了Ge纳米晶.在Ge的摩尔分数为25%的样品中,Ge纳米晶只是来源于初始样品中的非晶Ge,而在Ge的摩尔分数为60%的样品中Ge纳米晶除了来源于初始样品中的非晶Ge外还来自于部分GeO2.进一步分析表明在Ge的摩尔分数为60%的样品中,有摩尔分数为20%的GeO2与来自衬底的Si发生还原反应生成Ge纳米晶.

Local structure of Ge nanocrystals embedded in SiO2 studied by Fluorescence EXAFS technique

The fluorescence extended X-ray absorption fine structure (EXAFS) technique was used to study the local structure of Ge nanocrystals embedded in SiO2 matrix, which were synthesized by the magnetron sputtering co-deposition. It is revealed that in the as-prepared samples, Ge atoms mainly exist in the form of amorphous phases of Ge and GeO2. The sample with Ge mole fraction of 25% is mainly composed of the GeO2 phase. Upon annealing at 1073 K, Ge nanocrystals are formed. In the sample of 25% Ge (mole fraction), Ge nanocrystals come from amorphous Ge phase; while in the sample of 60% Ge (mole fraction), Ge atoms come from both GeO2 and amorphous Ge phase. A further analysis of the sample containing 60% Ge (mole fraction) shows that about 20% GeO2 (mole fraction) is turned into Ge nanocrystals due to the reduction reaction with Si atoms coming from the substrate.