自组装Ge量子点热扩散效应的XAFS研究  

Thermal diffusion effect of self-assembled Ge quantum dots probed by fluorescence X-ray absorption fine structure

作　　者：潘志云[1] 王科范[1] 刘金锋[1] 徐彭寿[1] 孙治湖[1] 闫文盛[1] 韦世强[1] 

机构地区：[1]中国科学技术大学国家同步辐射实验室,安徽合肥230029

出　　处：《中国科学技术大学学报》2007年第4期549-553,共5页JUSTC

基　　金：国家自然科学基金(10375059;10404023);北京同步辐射实验室与合肥国家同步辐射实验室合作项目资助

摘　　要：利用荧光X射线吸收精细结构(X-ray absorption fine structure,XAFS)方法研究了分子束外延生长的自组装Ge/Si(001)量子点的扩散效应.原子力显微镜结果表明,在550℃的生长温度下形成了面密度为5.2×1011cm-2的高密度小尺寸量子点.XAFS结果表明,生长的Ge量子点样品覆盖Si层后在550℃温度退火,对Ge/Si之间的热扩散混合的影响较小.随着退火温度升高到800℃,Ge原子的第一近邻配位壳层中的Ge-Si配位的无序度由4.0×10-5nm2降低到2.9×10-5nm2,配位数由3.3升高到3.8,这表明Ge量子点样品中的Ge原子的近邻主要为Si配位原子,高温退火显著增加了Ge原子在Si层中的扩散.The fluorescence X-ray absorption fine structure （XAFS） technique was used to study the diffusion effect of self-assembled Ge/Si（001） quantum dots grown by molecular beam epitaxy （MBE）. The atomic force microscopy （AFM） image shows that Ge quantum dots with high area density of 5.2×10^11 cm^-2 are grown at the substrate temperature of 550 ℃. The XAFS result shows that the annealing treatment at 550 ℃ for the Si-capped Ge quantum dots can hardly affect the thermal diffusion between Ge and Si atoms. With the annealing temperature increasing from 550 ℃ to 800 ℃, a drastic change of local structure around Ge atoms can be observed. The coordination numbers of the nearest Ge-Si pair increase from 3.3 to 3.8, and the Debye-Waller factor decreases from 4.0 to 2.9 × 10.5 nm^2. This indicates that the Ge atoms have been dominantly surrounded by Si atoms and that the annealing at observably increases the diffusion of Ge atoms from the quantum dots into the Si capping layer.

关 键 词：XAFS GE量子点 局域结构 热扩散 

分 类 号：O722.8[理学—晶体学]