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Greene, Joseph E. D'arcy-Gal, Julie 2015-09-25T20:52:31Z 2015-09-25T20:52:31Z 10000-01-01 2001 2001 Epitaxial metastable Ge1-yCy alloy layers with y ≤ 0.035 were grown on Ge(001) from hyperthermal Ge and C atomic beams at deposition temperatures 250 ≤ Ts ≤ 550°C. I show that the use of hyperthermal beams allows me to controllably vary the concentration of C incorporated as Ge-C split interstitials. Ge1-y Cy layers grown with incident Ge-atom energy distributions corresponding to ≤0.14 lattice d&barbelow;isplacement p&barbelow;er incident a&barbelow;tom (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, I calculate 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 Ts. I find that at low y and Ts 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 Ts, irrespective of the dpa, leads to an increase in the fraction of C nanoclusters, while the fractions of substitutional C and Ge-C split interstitials decrease, due to the higher C-C encounter probability at the growth surface. Made available in DSpace on 2015-09-25T20:52:31Z (GMT). No. of bitstreams: 2 license.txt: 4848 bytes, checksum: 96035ab3f5e1c23cc7138a224ce498bd (MD5) 3017061.pdf: 3328999 bytes, checksum: 5735f51af6d1e08de00455a57b40c622 (MD5) Previous issue date: 2001 Embargo set by: Seth Robbins for item 83978 Lift date: Forever Reason: Restricted to the U of I community idenfinitely during batch ingest of legacy ETDs Restricted to the U of I community idenfinitely during batch ingest of legacy ETDs U of I Only 90 p. Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2001. http://hdl.handle.net/2142/82697 (MiAaPQ)AAI3017061 eng Physics, Condensed Matter Carbon Incorporation During Growth of Epitaxial Germanium(1-Y)carbon(y) Layers on Germanium(001) Substrates text Materials Science and Engineering Materials Science and Engineering University of Illinois at Urbana-Champaign Dissertation Ph.D.