Effect of alternation of kinetic coefficients on step instabilities on Si(0 0 1) vicinal face

With taking account of alternation of kinetic coefficients, we study the possibility of step instabilities on a Si(0 0 1) vicinal face. In sublimation, a step with large kinetic coefficient recedes faster than that with small kinetic coefficient, and step pairs are formed. The upper side step in the step pair is the step with large kinetic coefficient. An equidistant array of the pairs is unstable against bunching. Number of steps NmaxNmax in bunches increases with time as Nmax∼tβNmax∼tβ. The exponent β=0.5β=0.5 when the bunch grows via successive collisions of step pairs, and β≈1.2β≈1.2 when the bunch grows via coalescence of bunches.