| Autor: |
D’Arcy-Gall, J., Gall, D., Petrov, I., Desjardins, P., Greene, J. E. |
| Předmět: |
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| Zdroj: |
Journal of Applied Physics; 10/15/2001, Vol. 90 Issue 8, p3910, 9p, 1 Black and White Photograph, 2 Diagrams, 6 Graphs |
| Abstrakt: |
Epitaxial metastable Ge[sub 1-y]C[sub y] alloy layers with y≤0.035 were grown on Ge(001) from hyperthermal Ge and C atomic beams at deposition temperatures T[sub s] of 250 and 300 °C. The use of hyperthermal beams allows us to controllably vary the concentration of C incorporated as Ge–C split interstitials. Ge[sub 1-y]C[sub y] layers grown with incident Ge-atom energy distributions corresponding to ≤0.14 lattice displacement per incident atom (dpa) are in a state of in-plane tension and contain significant concentrations of C atoms incorporated in substitutional sites. Increasing the dpa to 0.24 yields layers in compression with C incorporated primarily as Ge–C split interstitials. Ab initio density functional calculations of the formation energies and strain coefficients associated with C atomic arrangements in Ge show that configurations containing multiple C atoms, referred to collectively as C nanoclusters, are energetically more favorable than substitutional C and Ge–C split interstitials and yield a nearly zero average strain. In contrast, substitutional C and Ge–C split interstitials produce large tensile and compressive strains, respectively. Using the calculated strain coefficients, measured layer strains obtained from high-resolution reciprocal lattice maps, and substitutional C concentrations determined by Raman spectroscopy, we obtain the fraction of C atoms incorporated in substitutional, Ge–C split interstitial, and nanocluster sites as a function of the total C concentration y and T[sub s]. We find that at low y and T[sub s] values, all C atoms are incorporated in single-C configurations: substitutional C and Ge–C split interstitials. Their relative concentrations are controlled by the dpa through the production of near-surface Ge self-interstitials which are trapped by substitutional C atoms to form Ge–C split interstitials. Increasing y and T[sub s], irrespective of the dpa, leads to... [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
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