Nucleation and growth of Ge on Si(1 1 1) by MBE with additional atomic hydrogen irradiation studied by scanning tunneling microscopy

Abstract

We have studied the influence of atomic hydrogen (H) on the nucleation and growth of Ge films on Si(1 1 1) surfaces grown by molecular beam epitaxy (MBE) using scanning tunneling microscopy (STM). The substrate temperature dependence of two-dimensional (2D) nucleus density has two different activation energies, which depend on the surface structure change by H irradiation. In addition, the 2D nucleus density is proportional to the square root of the amount of atomic H flux density. We have discussed and proposed a model on the influence of H adsorption on the surface migration of Ge atoms. Moreover, the activation energy of nucleation is also increased by the H atoms, which arises from the addition of the activation energy of H desorption, indicated by a simple migration model. The model can also explain the H-flux dependence of the nucleus density.