Step bunching phenomena on Si(001) surface induced by DC heating during sublimation and Si deposition

Using in situ ultrahigh vacuum reflection electron microscopy and ex situ atomic force microscopy, we have investigated the influence Si deposition on the step bunching on the Si(0 0 1) surface under direct current (DC) sample heating in 950-1150 degrees C temperature range. During sublimation time scaling exponents of the average distance between the bunches are about 0.3 for both step-up and step-down DC directions at all temperatures. We have found that the shape of the step bunches becomes straight, and the number of step pairs between the bunches increases at a temperature above 1050 degrees C for fixed annealing time. We have established that the step bunching rate during step-up DC heating is characterized by 0.24 eV effective activation energy under sublimation conditions. The mean bunch separation changes non-monotonically when net growth rate (R) rises and it decreases as R-1/2 near equilibrium conditions.