Si(001)表面分子束外延生长的小尺寸Ge量子点

Small-size Ge/Si(001) Quantum Dots Grown by Molecular Beam Epitaxy

通过调节生长参数,在Si(001)衬底表面利用分子束外延(MBE)方法生长得到尺寸小于10nm的高密度Ge量子点.扩展的X射线吸收精细结构(EXAFS)的研究结果表明,在500℃和550℃制备的小尺寸量子点内,GeSi合金的含量分别为75%和80%.经热力学分析,在量子点生长完成后的退火过程中,可能存在Si原子从衬底表面向量子点表面扩散,并和Ge原子通过表面偏析发生混合的过程.另一方面,小尺寸量子点较高的高宽比,也会导致形成较高含量的GeSi合金.

High density of Ge quantum dots （QDs） with size of less than 10 nm were obtained on Si（001） surface by optimizing the growth parameters. The results of extended X-ray absorption fine structure （EXAFS） showed that the contents of GeSi alloy in these QDs fabricated at 500 ℃ and 550 ℃ were 75% and 80%, respectively. According to thermodynamics analysis, it was believed that during the annealing process after the QDs＇ growth, Si atoms might diffuse from the substrate surface to the QDs surface, then intermix with Ge atoms by surface segregation. On the other hand, the higher heighi/diameter ratio might also induce high content of GeSi alloy in small size of Ge QDs.