We report on the analysis of the composition and internal structure of SiOx layers deposited on powder particles by using HMDSO as monomer, different oxygen admixtures in argon, and a dielectric barrier surface discharge under atmospheric pressure. Composition and structure of the deposited layers with special regard to silicon, carbon, and hydrocarbon bonding were studied by FTIR and XPS measurements and compared with previous investigations from the literature. For correlation of the layer composition and the plasma gas phase we used mass spectrometric analysis of the exhaust gas. The stoichiometric ratios of the deposited layers are remarkably influenced by the Ar/O2 ratio and the discharge conditions.