Scanning tunneling microscopy: principle, construction and applications

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Thermal stability of strained silicon/silicon-germanium/silicon structures

The thermal stability of strained Si1-xGex layers grown epitaxially by molecular beam epitaxy on Si(100) and capped by a Si top layer was studied using Rutherford backscattering spectrometry. Diffusion coefficients were evaluated from the Ge scattering profiles of a 50 nm SiGe film, capped with 50 nm Si, for anneal temperatures between 850 degrees C and 1010 degrees C. The diffusion coefficient, calculated from the increase in signal in the tail of the Ge profile, proved to be comparable with the value for Ge in bulk Si. An enhanced decrease in signal at the centre of the Ge profile indicated a faster diffusion within the SiGe layer. This was confirmed by analysis of the FWHM of the Ge profile, from which a diffusion coefficient was derived which was up to 20 times higher

Diffusion and strain relaxation in silicon/silicon-germanium/silicon structures studied with Rutherford backscattering spectrometry

The thermal stability of strained Si/Si1-xGex/Si structures grown by molecular beam epitaxy was investigated by resistive heating and in situ Rutherford backscattering spectrometry. Ge profiles obtained from a 50 nm Si1-xGex layer on a Si(100) substrate capped with 50 nm Si were evaluated for different Ge concentrations after sequential heating periods at a particular temperature between 850 and 1010° C. The diffusion coefficients, calculated from the increase in signal in the tail of the Ge profile, proved to be comparable to the value for Ge in bulk Si. A more pronounced decrease of the signal at the center of the Ge profile indicated a faster diffusion within the SiGe layer which was confirmed by analysis of the FWHM of the Ge profile. Ion channeling measurements were used to characterize tetragonal strain in the buried SiGe layers. Angular scans through the 111 direction were interpreted with Monte Carlo channeling calculations and used to study strain relaxation in dislocation-free and partially relaxed layers

Precipitation of antimony delta-doping layers in Si studied with channeling Rutherford backscattering spectrometry

Antimony 5-doping layers in Si have been prepared using molecular beam epitaxy. First of all, a crystalline buffer layer was deposited at 700°C, followed by Sb deposition from a Knudsen cell. After cooling down to room temperature, amorphous Si was deposited on top and subsequently crystallized using solid phase epitaxy (SPE). The thermal stability of the 8-doping layers was studied in the temperature range of 625-725°C which is only slightly above the SPE temperature. Lateral Sb redistribution was followed by measurement of the Sb minimum yield in channeling Rutherford backscattering spectrometry. An increase in minimum yield was found and was correlated with the formation of precipitates as measured with transmission electron microscopy. The high diffusion coefficients required to explain the observed precipitation are qualitatively in agreement with a diffusion model, based on percolation theory, proposed before for Sb diffusion in heavily doped Si