THE ROTATIONAL DISORDER OF PB W(112)

Using high-resolution low-energy electron diffraction, we have observe d the rotational disorder of Pb/W(112) during MBE growth. Pb atoms gro w on W(112) substrate in a typical 3D fashion, forming Pb(111) islands as the thickness of the Pb layers increases. While the surface normal of the Pb(111) islands aligns with that of the W(112), the lateral la ttice orientation within the Pb(111) plane is not unique with respect to the W(112) substrate. Depending on the growth rate, the Pb overlaye r may have different morphologies. At the lower deposition rate, rando m orientations as well as six discrete orientations are observed. At t he medium deposition rate, four discrete orientations are observed. At the higher deposition rate, only one orientation is observed but with certain lateral deviations. These orientations can be attributed to t he substrate geometry, lattice matching at the interface and the symme try principle for epitaxial rotation.