Surface reconstruction stability and configurational disorder on Bi-terminated GaAs(001)

Joanna Millunchick

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joannamm@umich.edu

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Adam Duzik, John C Thomas, der VA van, and Joanna M Millunchick (2013)

PHYSICAL REVIEW B, 87(3).

We developed a rigorous and exhaustive method for calculating the 0 Ksurface phase diagram of Bi/GaAs(001) by using density functional theoryin conjunction with the cluster expansion formalism. In a search forground- state alloy configurations of low energy surface structureprototypes, we found that the (2 x 1), alpha 2(2 x 4), and beta 2(2 x 4)structures possess only a few stable configurations, though each isstable over a wide range of chemical potential. In contrast, the c(4 x4) and (4 x 3) structures exhibit many stable configurations, suggestingtheir tendency towards configurational disorder at finite temperature.Monte Carlo simulations confirm a continuous disordering of the (4 x 3)reconstruction with increasing temperature that comes to completion wellbelow typical MBE growth conditions, in contrast to the (2 x 1)structure, which remains ordered at high temperature. The calculatedzero Kelvin phase diagram and finite temperature Monte Carlo results arein excellent agreement with STM in this work and experimentalobservations seen elsewhere. Furthermore, these results provideimportant insights into challenges posed by growth of GaAsBi alloys,namely Bi incorporation, CuPtB ordering, and Bi clustering. DOI:10.1103/PhysRevB.87.035313

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