AVS 49th International Symposium
    Surface Science Wednesday Sessions
       Session SS+EL-WeM

Paper SS+EL-WeM3
High Resolution Large Area STM Analysis of Nucleationless Island Formation in SiGe/Si(100)

Wednesday, November 6, 2002, 9:00 am, Room C-110

Session: Nucleation & Growth of Semiconductors
Presenter: P. Zahl, Colorado School of Mines
Authors: P. Zahl, Colorado School of Mines
P.W. Sutter, Colorado School of Mines
J.S. Palmer, Colorado School of Mines
E.A. Sutter, Colorado School of Mines
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We present an STM analysis of quantum dot (QD) island self-assembly in lattice-mismatched heteroepitaxy. A primary objective of recent research on QD growth is the creation of long-range ordered arrays of QDs of uniform size, a major technological milestone that would pave the way for application of these nanostructures in electronic and optoelectronic devices. The formation of epitaxial QD islands is generally assumed to involve nucleation, a statistical process that would severely impede QD organization. Our recent observations by atomically resolved large area STM document the complete transition from initial surface roughening to the formation of faceted QDs in the heteroepitaxial SiGe/Si(100) system. QD self-assembly occurs in a coninuous process that avoids nucleation.@footnote 1,2@ Combining growth with in-situ STM, we analyze the surface morphology evolution with increasing coverage. The key aspect of this analysis is the capability of our system to acquire very large STM scans (up to 400nm x 1000nm with 0.1nm resolution), with an unprecedented combination of image detail and statistics. The 2xn reconstruction and step meandering are analyzed at lower coverages, with the goal of identifying mechanisms that induce long-range order in the nucleationless islanding process. Statistical information is extracted using a SPA-LEED@footnote 3,4@ like analysis of STM images in reciprocal space. At higher coverages the surface gets micro-rough and a transition to 3D growth of faceted, pyramid shaped QDs occurs. The arrangement and influence of the surrounding micro-rough area is analyzed in detail, depending on germanium concentration and growth conditions. @FootnoteText@ @footnote 1@ P. Sutter and M.G. Lagally, Phys. Rev. Lett. 84, 4637 (2000)@footnote 2@ R.M. Tromp, F.M. Ross, and M.C. Reuter, Phys. Rev. Lett. 84, 4641 (2000)@footnote 3@ Spot Profile Analysing-LEED @footnote 4@ M. Horn-von Hoegen, Z. f. Kristallographie 214, 591, 727 (1999), I+II.