Mobile Point Defects and Atomic Basis for Structural Transformations of a Crystal Surface

doi:10.1126/science.265.5171.490

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Science 22 July 1994:
Vol. 265. no. 5171, pp. 490 - 496
DOI: 10.1126/science.265.5171.490

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Mobile Point Defects and Atomic Basis for Structural Transformations of a Crystal Surface

Ing-Shouh Hwang ¹, Silva K. Theiss ², and J. A. Golovchenko ³

¹ Division of Applied Sciences, Harvard University, Cambridge, MA 02138, USA.
² Department of Physics, Harvard University, Cambridge, MA 02138, USA
³ Department of Physics and Division of Applied Sciences, Harvard University, Cambridge, MA 02138, and Rowland Institute for Science, Cambridge, MA 02142, USA.

Structural transformations on elemental semiconductor surfacestypically occur above several hundred degrees Celsius, and theatomic motions involved are extremely rapid and difficult toobserve. However, on the (111) surface of germanium, a few leadatoms catalyze atomic motions so that they can be observed witha tunneling microscope at temperatures below 80°C. Masstransport and structural changes are caused by the creationand propagation of both vacancy-like and interstitial-like pointdefects within the crystal surface. The availability of danglingbonds on the surface is critical. A detailed atomic model forthe observed motions has been developed and is used to explainthe structural phase transition Ge(111)-c(2x8) $harr$ 1x1, which occursnear 300°C.

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