A method is presented to analyze XPS spectra recorded from thin (<5 nm) oxide layers with known thickness on corresponding metal substrates. With this method, the contribution of the oxide overlayer can be separated from the metal substrate for the metal core level line, even when the difference in binding energy between metallic and oxidic electrons is small. This method involves the fitting of Doniach-Sunjic (DS) line shapes for the metallic and oxidic state to the measured spectrum, where the area ratio between the metallic and oxidic contribution is fixed through the known thickness.The method was applied to ruthenium single crystals with a (0001) surface that were oxidized in a ultra-high vacuum (UHV) chamber at a temperature of 673 K and an oxygen pressure between 1×10 −4 and 1×10 −2 Pa. Analysis of the oxidic contribution to the Ru 3p 3/2 line shows that two different types of oxides can be formed in the oxidation process.

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Surface passivation is of vital importance for next generation solar cells. Outstanding properties of atomic layer deposition (ALD) can be employed to passivate Si surface with very good uniformity over large areas, excellent step coverage on non-planar surfaces and precise thickness control of nano-thick layers. The challenge is to apply ALD in a cost effective way acceptable for PV industry. In this work we report on the development of atmospheric pressure spatial ALD for (inline) deposition of Al 2 O 3 layers with a throughput of 2000-3600 wafers/hour and low TMA precursor consumption. Layers with a thickness of 6-10 nm are optimal for rear side passivation, resulting in effective chemical and field-effect passivation without delamination (blistering) at the contact annealing step. This passivation is implemented in mass production and gives an efficiency improvement of 0.4-0.8% for PERC type solar cells.

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