Peculiarities of step bunching on Si 001/surface induced by DC heating

An evolution of the stepped Si 001. surface, induced by the electric current heating the crystal, has been observed directly by an in situ ultra-high vacuum reflection electron microscopy UHV REM.. Two scenarios of the initial stages of step bunching, depending on the average step–step distance, were detected: monatomic step coupling and polycentric nucleation of large terraces. From the successive REM images of step bunching, the step number in the bunch was accounted to depend on the annealing time as a power-law function with a scaling exponent equal to 0.53"0.05. Also, the average distance between coupled steps in the bunch was measured as a root-square dependence on the number of the coupled steps in this bunch. In spite of essential difference in the structural properties of Si 001.and Si 111.surfaces, the monatomic step behavior seems to be described by