THE EFFECT OF EXTERNAL STRESS ON SI SURFACES

To study the effect of strain on surface properties, we had externally applied a continuously variable stress by loading cantilevered bars. The first experiments1 on nominally flat Si (100) produced asymmetries in the population of 2 × 1 and 1 × 2 domains which depended on the strain and not the gradient. The kinetics for the production and annealing of the asymmetry were identical and thermally activated, but the final steady state was temperature independent. The sense of the asymmetry is that the domain compressed along the dimer bond is favored. Alerhand et al2. have suggested that the mechanism is the reduction of the energy in long range strain field due to the intrinsic surface stress. In this paper we compare the experimental observations and the expectation of the theory. We have now done the same experiments on a vicinal surface miscut by 1°. We have also observed the changes in the step (domain boundary) configurations in the STM. With an inadvertant miscut of 0.1°, the steps remain single height and generally correspond to the local optimization in Ref. 2, i.e., the sum of widths of adjacent minority and majority domains is unchanged. Similar experiments on Si(111) 7x7 induced no structural change with 0.3% uniaxial strain. © 1990, American Vacuum Society. All rights reserved.