A STRAIN-RELIEVE TRANSITION IN EPITAXIAL-GROWTH OF METALS ON SI(111)(7X7)

RHEED intensity oscillations observed during growth of several metals (Cu, Al, Ba, Sr, Pb) on Si(111)(7 x 7) substrates at 100 K show that the growth mechanism is layer-by-layer like. The growth behaviour, although rather complicated, follows the same pattern for all metals. Initially the oscillations are rather irregular and damped. At higher coverages the amplitude of the oscillations increases and the period becomes much more regular. This phenomenon is explained by assuming a transition from a rather imperfect substrate-matched to a relaxed bulk metal phase. This explanation is supported by diffraction data.