Dynamics of monoatomic steps on the Si(100) surface during MBE growth and post-growth annealing

The dynamics of monoatomic steps on the Si(100) vicinal surface during molecular beam epitaxy (MBE) growth and annealing is studied based on the analysis of reflection high-energy electron diffraction intensity variations. During growth, the initially equally spaced A- and B-steps are getting closer: the width of the A-terraces decreases to a certain minimum value, which increases with increasing growth temperature. The number of Si monolayers deposited until the minimum distance between the A- and B steps is reached increases monotonically with increasing temperature. After interrupting the Si deposition flux (during annealing) the width of the A-terrace gradually increases to the initial value. The time of such relaxation to the initial configuration of the steps decreases with increasing temperature and increasing miscut angle. The observed behavior of the steps during annealing is in good agreement with the available theoretical models of the step dynamics and is explained by the presence of an exchange flux of Si atoms between the A- and B-steps due to the elastic interaction of the steps caused by the anisotropy of the elastic stress tensor on the reconstructed Si(100) surface. However, the available models fail to explain the experimentally observed monotonically increasing temperature dependence of the number of Si monolayers deposited until the steps approach each other during growth, which indicates the need to modify the model of incorporation of Si adatoms into steps in the case of high temperatures.