Epitaxial growth is essential for producing high-quality films and structures of advanced materials. Being an important tool for investigation of epitaxial growth, the image properties of the Low Energy Electron Microscopy (LEEM) were studied. Two kinds of contrast, step contrast and quantum size contrast, were investigated by comparing real image contrast to the simulation results of constructed theoretical models under different conditions. With the unique characteristics of images, LEEM was used to investigate the kinetic processes involved in crystal growth, which can be the dominant factor on the final morphology. When compared with other techniques such as Reflected Electron Microscopy (REM) and Scanning Tunneling Microscopy (STM), LEEM imaging does not have the problems of foresh...[ Read more ]

Epitaxial growth is essential for producing high-quality films and structures of advanced materials. Being an important tool for investigation of epitaxial growth, the image properties of the Low Energy Electron Microscopy (LEEM) were studied. Two kinds of contrast, step contrast and quantum size contrast, were investigated by comparing real image contrast to the simulation results of constructed theoretical models under different conditions. With the unique characteristics of images, LEEM was used to investigate the kinetic processes involved in crystal growth, which can be the dominant factor on the final morphology. When compared with other techniques such as Reflected Electron Microscopy (REM) and Scanning Tunneling Microscopy (STM), LEEM imaging does not have the problems of foreshortening in images, time delay in getting images, and difficulties in imaging at high temperature. These allow the real time detail studies of 2D islands nucleation growth and step flow growth on Si(111)-(7x7) under different temperatures. Normally, crystal growth is in three dimensions while epitaxial growth is in two dimensions. Direct studies on the 3D or 2D growth involve very complicate combined effect of the 3D and 2D geometry. The study of step flow growth and island nucleation in straight steps have advantages over prior work because this platform is effective in 1D geometry. This allows the study of the step orientation dependence of the asymmetry and the critical terrace width. With the advantage of real time imaging at high temperature, the Arrhenius behavior of critical terrace width at high temperature, which was not seen before, was found to be different from that at low temperature. By restricting the studies in 1D geometry, one of the kinetic processes investigated was the ratio of step attachment rate of adatoms from terrace trailing and leading an advancing step which was experimentally determined to be equal to 1.19± 0.04 at 8OOK on Si(111)-(7x7) surface by using two independent experimental approaches. They are direct measurements of step flow velocity on surface with different terrace widths and measurements of island nucleation positions on critical terrace width. These measurements are the first experimental observations on the step attachment rate. The asymmetry found indicates that adatoms from trailing terraces are easier to attach to steps than those from leading terraces on Si(111)-(7x7) surface. This asymmetric step attachment is shown to be one of the possible causes of step bunching. By varying the incident flux and substrate temperature, the morphology of epitaxial growth can be selected. Their relationship is demonstrated in the study of nother kinetic process - competing desorption, which was investigated in Cu/W(110) growth which forces the growth to proceed in step flow growth like. In order to describe the behavior of the kinetic process, a mean-field growth model was developed which explained the divergence of the critical temperature of desorption. This opens up a new method to determine the desorption energy and attempt frequency by examining the balance of incident and desorption fluxes.