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The electron yield from SiOz films on Si was measured as a function of oxide thickness and ion energy for 150 -300 keV H+, He+, N+, Ne+, Ar+, Kr+, and Xe+ ions. For oxide films thicker than 200 A, the electron yield was found to be approximately independent of oxide thickness. The electron yield from the thick oxide increased as a function of the energy deposited D in electronic excitations with approximately the form D ' and not D as expected from theory. Close to the Si02/Si interface, unexpected variations in the electron yield with oxide thickness, dependent on ion mass and energy, were found. Experiments were performed to investigate whether or not the oxide surface was charged by the ion beam, but such effects could not be observed. However, a satisfactory interpretation of the data could be obtained with a model previously suggested for explaining the dependence of the electron yield on the angle of ion incidence. In this model, the positive charge left behind in the oxide by the liberated electrons within the electron cascades of individual ions, causes the probability of escape of electrons to decrease with increasing electron yield.

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The goal of this study is to investigate the effect of carbon incorporation upon thermal oxidation of Si1−xGex alloys and its role on strain compensation in Si1−xGex alloys. Si1−xGex and Si1−x−yGexCy alloys on Si(100) are grown by combined ion and molecular beam deposition and are then oxidized at 1000 °C in a dry oxygen ambient for two h. The thickness and the composition of all samples before and after oxidation are measured by Rutherford backscattering spectrometry (RBS) combined with ion channeling at 2.0 MeV and carbon nuclear resonance analysis at 4.3 MeV using 4He++ ions. In agreement with previously reported results of dry oxidation on Si1−xGex thin films, 2.0 MeV RBS analysis shows that a layer of SiO2 is formed on the top surface of both Si1−xGex and Si1−x−yGexCy thin films, while Ge segregates towards the top surface and at the SiO2/Si1−xGex and SiO2/Si1−x−yGexCy interfaces. However, it is observed for the first time that dry oxidation rates of Si1−xGex thin films decrease with increasing Ge fraction x for x≳0.20 and with increasing minimum yield. Ion channeling analysis and strain measurements indicate that the incorporation of C rather than the amount of C itself affects the dry oxidation mechanism because of its strong influence on film strain and crystalline quality. These results are discussed in conjunction with observations by secondary ion mass spectrometry, high resolution transmission electron microscopy, Fourier transform infrared spectrometry, and tapping mode atomic force microscopy.