Behavior of gold (Au) on n-type Si(100) surface dipped in Au aqueous solution and thermally oxidized have been studied using by atomic force microscope (AFM), X-ray photoelectron spectroscopy (XPS), alternating current surface photovoltage (AC SPV) techniques and ellipsometer. AFM and XPS analyses identified Au to exist at both the top of SiO
2 and SiO
2/Si interface as a cluster. Au/n-type Si Schottky-barrier causes an occurrence of frequency-dependent AC SPV. The frequency-dependent AC SPV still appeared in Au-contaminated (∼2×10
15 atoms/cm
2) and thermally oxidized Si surfaces at between 550 and 700
oC, demonstrating that Si surface was weakly inverted. This result indicates that Au/n-type Si Schottky-barrier is formed at SiO
2/Si interface even after thermal oxidation. The Au at SiO
2/Si interface diffused into bulk Si as temperature increased higher than 750
oC, resulting in drastic reduction of AC SPV. On oxidation kinetics at between 750 and 900
oC, Au is thought to act as catalyst to promote SiO
2 growth at the Si surface, resulting in the enhanced oxidation.
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