Direct current heating effects on Si(111) vicinal surfaces

Study on new types of step instability on a Si(111) vicinal surface induced by the direct current heating effect by reflection electron microscopy and optical microscopy is reviewed. One step instability is in-phase step wandering and the other is a periodic step density wave (PSDW). The former is due to electromigration of Si adatoms and steps are aligned in phase without changing mean step-step distance. This instability occurs at temperatures between 1000 and 1200degreesC, under the step-down current heating condition. Steps are in the sinusoidal shape and their wavelength is in the micron order. The wavelength does not depend on the mean step-step distance or off-angle of the vicinal surface nor annealing time. The latter is induced by Au adsorption under step-down current heating at temperature between 830 and 930degreesC where extremely straight step bands and Si(111) terraces are aligned periodically. The driving force of the PSDW is the modification of step structure due to electromigration of Au adatoms. These phenomena might be useful for micro-fabrication of surface from the industrial point of view as well as interesting from the fundamental point of view.