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 x 1 substrates at room temperature has been investigated mainly by scanning tunneling microscopy (STM). In thi s study, we found that In atoms form a mixed reconstruction phase of n x 3 periodicity with 2 x 2 phase at coverage between 0.5 and 1.0 monolayer (ML) , which has not been observed so far. In atoms begin to form fiat two-dimen sional (2D) islands above I ML. These islands have an apparent height of ab out 7 Angstrom and exhibit 2 x 1 periodicity associated with the lattice co nstant of Si bulk crystal, indicating the formation of a strained In layer. With increasing In coverage, the area of the islands increases. At coverag e above 3 ML, however, this layer still does not dominate the entire surfac e and 2 x 2 and n x 3 phases still remain. We suppose that this layer plays an important role as the intermediate structure from 2D growth to 3D growt h.