ISSN:
1662-9779
Source:
Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
Topics:
Physics
Notes:
The interstitial carbon impurity (CI) vibrational modes in monocrystalline Si-rich SiGewere investigated by Fourier Transform Infra Red spectroscopy and density functional modelling.The two absorption bands of CI are found to be close to those in silicon, but show shifts in oppositedirections with increasing Ge content. The transversal mode band at 932 cm-1 shifts slightly to thehigh frequency side, while the longitudinal mode at 922 cm-1 suffers a pronounced red-shift. EachCi-related band is found to consist of two components. An annealing of CI in Si1-xGex occures intwo stage. During the first stage (210-250 K) the main components of bands anneals and revealedcomponents grow in intensity. At T〉250 K all components disappear. Two component structure ofbands is suppose most likely correspond to different combinations of Si and Ge atoms in theneighbourhood of the carbon atom. The interstitial carbon defect was modelled by a supercelldensity-functional pseudopotential method (AIMPRO) for alloys with 4.69% Ge concentration.From energetics, it has been found that each Ge-C bond costs at least 0.4 eV in excess of a Si-Cbond. However, structures where Ge atoms are second neighbors to the C atom are marginallybound, and may explain the two-component band structure in the absorption measurements. Thevibrational mode frequencies taken from several randomly generated SiGe cells produce theobserved opposite shifts for the transverse and longitudinal modes
Type of Medium:
Electronic Resource
URL:
http://www.tib-hannover.de/fulltexts/2011/0528/02/24/transtech_doi~10.4028%252Fwww.scientific.net%252FSSP.131-133.59.pdf
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