Thin Film Growth around Misfit Dislocations

近年来，Si/Ge异质结构在硅基二维电子和空穴的限制以及量子点的自组装方面受到了广泛的关注。这些应用的一个关键是控制应变异质界面的生长模式。然而，关于在Si_(1-x)&Gt；Ge_x(001)表面上生长硅层的细节还没有得到很好的研究。本文报道了我们用扫描电子显微镜研究了在Si_(001)衬底上生长的Si_(1-x&Gt；Ge_x)/Si(001)表面的硅层。在2x1重建中，0.46 nm厚的Sil-xGex层的表面包含许多二聚体空位。然而，台阶密度很小，足以使表面保持平坦，作为Si(001)衬底。随着厚度的增加，二聚体空位沿线排列，释放了Si_x_x；Ge_x(001)表面的压应变。二聚体空位线之间的距离减少到8a(a是su…在1.38 nm厚的Si_1-x&Gt；Ge_x层上，在有二聚体空位线的表面上，堆积了小阶梯，使表面不平坦。与Si(001)2x1表面相比，Sa台阶变得粗糙，Sb台阶变直。在厚度大于2 nm的Sil-xGex层表面，观察到了具有(105)晶面的锥形3D岛的形核，在0.46 nm厚的Si_&lt；1-x&Gt；Ge_x(001)层上，二聚体空位消失，初期出现许多小阶梯。随着硅的进一步沉积，阶梯尺寸变大，表面恢复平整。在厚度为1.38 nm的Si_(1-x)&Gt；Ge_x(001)层上，片状小阶梯消失，表面变得更加光滑。但是，当Si覆盖率达到1 nm时，二聚体空位线仍然存在，这可能是由于Ge的分离所致。在这次会议上，我们将详细介绍生长在Si_1-x&Gt；Ge_x(001)表面上的硅层的形态变化，并将从生长前沿应变的积累和释放以及Ge的向外扩散的角度进行讨论。较少

Si/Ge hetero-structure has been paid much attention in Si-based two-dimensional confinement of electrons and holes, and also in self assembling of quantum dots recently. A key of these applications is the control of the growth mode at the strained hetero-interfaces. However, a detail of the Si layers growth on the Si_<1-x>Ge_x (001 ) surface is still not well investigated. Here, we report our study on the growth of Si layers on Si_<1-x>Ge_x/Si (001) surfaces using STM.First, we observed the surface morphology of the Si_<1-x>Ge_x (001) layers of various thickness grown on the Si (001) substrates. The surface of the 0.46nm thick Sil-xGex layer include many dimer vacancies in the 2x1 reconstruction. However, the step density was small enough to keep the surface flat as the Si (001) substrate. Increasing the thickness, the dimer vacancies aligned to lines to release the compressive strain on the Si_<1-x>Ge_x (001) surface. The distance between dimer vacancy lines reduced to 8a (a is the su … More rface unit cell length) on the Si_<1-x>Ge_x layer of 1.38nm thickness.On the surface with dimer vacancy lines, small terraces stacked to make the surface uneven. SA step tended to be rough while SB step became straight in contrast to the Si (001) 2x1 surface. At the surface of the Sil-xGex layer with the thickness over 2nm, pyramidal 3D islands with (105) facets were observed to nucleate.In Si deposition, the dimer vacancies disappeared and many small terraces appeared in the initial stage on the Si_<1-x>Ge_x (001) layer of 0.46nm thickness. The terrace size became larger and the surface recovered smoothness in further deposition of Si. On the Si_<1-x>Ge_x (001) layer of 1.38nm thickness, patchy small terraces disappeared and the surface became smoother in the Si deposition. But, the dimer vacancy lines still persisted for the Si coverage up to 1nm, probably due to the segregation of Ge. In the conference, more details of the morphological change on the Si layers grown on the Si_<1-x>Ge_x (001) surface will be presented, and will be discussed from the viewpoints of the accumulation and release of stain and Ge out-diffusion on the growth front. Less