Direct Observation of Strained Layer Formation at the Initial Stage of In Thin Film Growth on Si(100)

The growth of In thin films on Si(100)2×1 substrates at room temperature has been investigated mainly by scanning tunneling microscopy (STM). In this study, we found that In atoms form a mixed reconstruction phase of n×3 periodicity with 2×2 phase at coverage between 0.5 and 1.0 monolayer (ML), which has not been observed so far. In atoms begin to form flat two-dimensional (2D) islands above 1 ML. These islands have an apparent height of about 7 Å and exhibit 2×1 periodicity associated with the lattice constant of Si bulk crystal, indicating the formation of a strained In layer. With increasing In coverage, the area of the islands increases. At coverage above 3 ML, however, this layer still does not dominate the entire surface and 2×2 and n×3 phases still remain. We suppose that this layer plays an important role as the intermediate structure from 2D growth to 3D growth.