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Letter

Thermodynamics of Coherently-Strained Ge_xSi₁_-_x Nanocrystals on Si(001): Alloy Composition and Island Formation

Gilberto Medeiros-Ribeiro*^†^‡ and R. Stanley Williams^†

Hewlett-Packard Laboratories, 1501 Page Mill Rd., Palo Alto, California 94304, Laboratorio Nacional de Luz Sncrotron, P.O. Box 6192, Campinas SP 13084-971, Brazil

Nano Lett., 2007, 7 (2), pp 223–226

DOI: 10.1021/nl062530k

Publication Date (Web): January 25, 2007

Corresponding author. E-mail: gmedeiros@lnls.br.

†

Hewlett-Packard Laboratories.

‡

Laboratorio Nacional de Luz Síncrotron.

Abstract

We determined the enthalpic and entropic contributions to the thermodynamics of coherently strained nanocrystals grown via deposition of pure Ge on Si(001) surfaces at 600 and 700 °C by analyzing their composition profile and local strain. We found that the free energy associated with the entropy of mixing, which drives Ge_xSi₁_-_x alloy formation, was significantly larger than the relaxation enthalpy that produces the islands. Thus, entropy plays a significant role in the evolution of the size and shape of the islands during growth through the strong thermodynamic drive to form an alloy.

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History

Published In Issue February 14, 2007
Received October 26, 2006
Revised Manuscript Received January 9, 2007

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Letter

Thermodynamics of Coherently-Strained Ge_xSi₁_-_x Nanocrystals on Si(001): Alloy Composition and Island Formation