Microscopic Study of Si-Ge Heteroepitaxial Growth by STM/STS

异质外延生长的薄膜在实现创新器件方面具有很大潜力。Si-Ge超晶格结构是最有吸引力的候选结构之一，但由于Si和Ge之间4.2%的拉特失配引起的应变使生长变得复杂，从而导致覆盖Ge的表面变得粗糙，导致超晶格的非突发性。本研究用超高真空扫描隧道显微镜/扫描隧道显微镜研究了Ge原子在Si(001)表面的表面形貌和表面电子态。在衬底温度300,400和500ﾟC时，Ge原子以小于1ML到8ML的量在Si(001)上沉积。在高于IML的覆盖率下，缺失的二聚体行被引入到显示带或贴片结构的GE Overayr中。沉积3ml的Ge后，HUT团簇由4个面的{015}面组成，在300ﾟC的温度下，整个表面覆盖黄铜后，HUT团簇结合在一起。在400ﾟC下改变了生长模式，其中具有4个面的宏观团簇在高于5ML处生长，在500ﾟC时，另一种类似穹顶的宏观团簇生长为6.5ML。对于在400ﾟC下生长的5mLGe覆盖层，还研究了500ﾟCFOR 5min下的退火效应。复杂的团簇生长，团簇的底部有{015}面，胸部有{113}面，重构的(001)表面有许多台阶。HUT团簇在退火过程中消失，就像宏观团簇吸收了HUT团簇，然后转变为复杂的团簇。在小屋星团消失后，复杂星团之间的斑块结构开始形成。具有贴片结构的层可以通过强连接到衬底，并且HUT Custer可以松散地结合到衬底。讨论了在TE界面附近的{015}面的稳定性。

Heteroepitaxially grown films have much potentials to achieve innovative devices. A Si-Ge superattice structure is one of the most attractive candidates But the strain nduced by a 4.2% lattce mismatch between Si and Ge makes the growth complicated, and then Ge-covered surfaces become rough, causing the non-abruptness of the superlattice In this study, the surface topotraphy and the surface electronic states of Ge overlayrs on Si(001) were investigated by a UHB-STM/STS.Ge atoms were deposited on Si(001) at substrate temperatures of 300, 400 and 500ﾟC by the amount from less than IML to 8ML.The deposited Ge atoms dimerize on Si(001). At a coverage higher than IML, the missing dimer rows are introduced in the Ge overayr exhibiting belt or patch structures. The hut clusters with 4 facets of {015} planes grow after the Ge deposition of 3ML, and the hut clusters coalesce at 300ﾟC after the whole surface is covered with the custers. The GROWTH MODE IS CHANGED AT 400ﾟC, where the macroscpic clusters with 4 facets of {113} planes grow at higher than 5ML.At 500ﾟC another type of macroscopic clusters ike a dome grows an 6.5ML.Annealing effects at 500ﾟCfor 5min were also investigated for the 5ML Ge overlayr grown at 400ﾟC.Complircated clusters grow, with the {015} facets on the foot of the clusters, the {113} facets on the breast, and the 2x1 reconstructed (001) surface with many steps on the top. The hut clusters disappear by the annealing as if the macroscopic clusters absorb the hut clusters, then are transformed into the complicated clusters. After the hut clusters disappear, the patch structures rcappear between the complicated clusters. The layr with the patch structures may by strongly connected to the substrate, and the hut custer may be loosey bound to the substrate. The stability of the {015} surface close to te interface was discussed.