We present x-ray Si K, Si L, and 0 I( emission bands of hydrogenated amorphous SiO"alloy films covering the concentration range 0 & x~2.2. All spectral features in the emission bands were identified and attributed to Si 3s, Si 3p, and 0 2s, 2p derived states. With increasing x, the shape and the energy position of the main features of the Si E and Si L emission bands change significantly, particularly in the concentration interval 0.5 &x &1.5. A comparison with available ultraviolet (UPS) and x-ray (XPS) photoemission spectra demonstrates that x-ray emission bands for a-SiO are more sensitive to sample composition than UPS and/or XPS spectra. The random-bonding model and the random-mixture model of the structure of SiO"alloys are discussed in view of the x-ray emission spectra. For x =2, the Si X, Si L, and 0 K spectra are very similar to those observed for cx-quartz (c-Si02). This justifies interpretation of all features of a-Si02:H on the basis of c-SiO&. We therefore performed self-consistent pseudopotential calculations of the total density of states and the local partial density of states of Si 3s, Si 3p, Si 3d, 0 2s, and 0 2p of cr-quartz. The calculations confirm that due to the high electronegativity of oxygen nonbonding, Si 3d-like states are created which, for high values of x, clearly show up in the Si L emission bands. Finally, we discuss the long-standing so-called d-orbital controversy about Si02 and give an explanation of it.
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