GROWTH-PROCESS OF TWINNED EPITAXIAL LAYERS ON SI(111)ROOT-3X-ROOT-3-BAND THEIR THERMAL-STABILITY

We investigated the growth of twinned epitaxial Si layers on a Si(111) root 3 X root 3 -B surface. In the initial growth stages, untwinned bi layer-high (BL-high) and twinned 2-BL-high islands are nucleated, and the ratio of the number of Si atoms included in the twinned 2-BL-high islands to the number of the total deposited Si atoms increases as the surface B concentration increases. Preferred nucleation of Si islands occurs at domain boundaries of the root 3 X root 3 reconstruction. Mo reover, BL-high islands rather than 2-BL-high islands nucleate there. Coalescence of 2-BL-high islands causes the domain boundary density on the first two bilayers to be much larger than that on the substrate. Therefore, after completion of the first twinned two bilayers, BL-high islands are formed predominantly. BL-high islands follow the stacking sequences of the twinned two bilayers. Thus, grown layers are totally twinned. We also investigated the thermal stability of twinned epitax ial layers. The temperature at which twinned epitaxial layers are tran sformed into untwinned layers strongly depends on the thickness. (C) 1 998 Elsevier Science B.V. All rights reserved.