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Thermodynamics of Coherently-Strained Ge(x)()Si(1)(-)(x)() Nanocrystals on Si(001): Alloy Composition and Island Formation.

Medeiros-Ribeiro G, Williams RS

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

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 degrees C by analyzing their composition profile and local strain. We found that the free energy associated with the entropy of mixing, which drives GexSi1-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.

Published 14 February 2007 in Nano Lett, 7(2): 223-6.
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