Abstract
Chemical etching of the (100) face of p-type Si by aqueous K2Cr2O7 was investigated with a contactless transient photoconductivity method, i.e. the time-resolved microwave conductivity (TRMC) method, after ns laser pulse excitation and with XPS, UPS, and LEED. TRMC transients after etching show a much slower decay that is explained by a decrease of surface recombination velocity. XPS indicates the formation of a mixed oxide of SiIII and Crv. During heating to ∼600°C this layer first transforms to a SiIV-CrIII oxide. After heating to 1200°C the oxide and Cr at the surface have disappeared, as indicated by UPS (He I and He II) and LEED (sharp 2×1 LEED pattern). However, XPS still shows the presence of Cro which evidently is diffused into the bulk. This can also be deduced from the transient photoconductivity measurements as TRMC transients at this stage show a fast decay rate that must be due to an increased bulk decay rate of excess charge carriers.
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