Schottky-Barrier-Induced AC Surface Photovoltages in Au-Precipitated n-Type Si(001) Surfaces

Abstract

We have studied the behavior of Au clusters on the top surface of a SiO2 film and/or at the SiO2/Si interface as a function of oxidation temperature between room temperature (RT) and 500 °C in conjunction with a Schottky-barrier-induced AC surface photovoltage (SPV) and an enhanced SiO2 growth due to Au at 500 °C. Upon rinsing an n-type Si(001) wafer in a Au-contaminated aqueous solution, precipitated Au atoms are observed as clusterlike Au granules on the top surface of SiO2 (Au surface concentration, 2.3 ×1015 atoms/cm2). In thermally oxidized Au-contaminated n-type Si(001) wafers between 100 and 500 °C, a Au cluster of a similar shape is also observed. Chemical analysis gives evidence that Au existed at the SiO2/Si interface, which produced Au/n-Si Schottky-barrier-type AC SPV between 100 and 500 °C as well as at both RT and higher temperatures, indicating that the Au/n-Si Schottky barrier remains in a similar manner. In the Au-contaminated n-Si thermally oxidized at 500 °C, the catalytic action of Au atoms enhances SiO2 growth as well as the case at high temperatures between 750 and 900 °C. The mechanism of the enhanced growth is proposed.

Anomalous Oxide Charge Variation Identified by Alternating Current Surface Photovoltage Method in Cr-Aqueous-Solution-Rinsed p-Type Si(001) Wafers Exposed to Air

“…The AFM image showed a smooth and flat surface in contrast to the clusterlike Au granules observed in the Au-aqueous-solution-rinsed Si surface. 23) This indicates that the Cr atom layer can cover the bare Si surface. This result will be discussed in x3.4.…”

“…On the other hand, in the n-type Si(001) surface dipped in hydrofluoric acid (HF) aqueous solution (hydrophobic in surface) and rinsed with Au aqueous solution, clusterlike Au granules are observed on the Si hydrophobic surface by atomic force microscopy (AFM), resulting in the formation of Schottky barrier contact. 23) Cr-deposited surfaces have not been investigated yet by AFM. In principle, a Cr layer deposited on a p-type Si surface is not expected to generate a Schottky barrier in contrast to that deposited on an n-type Si surface.…”

Direct Observation of Au Nanoclusters at Au/Si Interface and Enhanced SiO2Growth Due to Catalytic Action by Au in Thermally Oxidized Au-Precipitated n-Type Si(001) Surfaces

“…10,11) It was observed that when n-type Si(001) wafers with a hydrophobic surface are rinsed in Au aqueous solution, an alternating current (AC) surface photovoltage (SPV) [12][13][14][15][16] is generated by the deposition of Au on the Si surface (Au/n-Si Schottky barrier), demonstrating that depleted or weakly inverted layers can be formed at the Au/n-Si interface. 17) It was postulated that this AC SPV is caused by the Schottky barrier. 17) The occurrence of AC SPV differs fundamentally from that originally described as a metal-induced negative oxide charge (Q mi ) 18) shown by (AlOSi) À networks and/or AlO 2 À in n-type Si.…”

“…17) It was postulated that this AC SPV is caused by the Schottky barrier. 17) The occurrence of AC SPV differs fundamentally from that originally described as a metal-induced negative oxide charge (Q mi ) 18) shown by (AlOSi) À networks and/or AlO 2 À in n-type Si. 19) Thus, the Au/n-Si interface should be investigated with reference to the Schottky barrier in detail.…”

“…In contrast, Shimizu and coworkers 27,28) used X-ray photoelectron spectroscopy (XPS) to show that Au on a Si surface did not bond with other elements at RT. In the author's previous report, 17) an atomic force microscopy (AFM) revealed a nanosize protuberance with granular shape and/or nanometer-size islands (about 20 nm in diameter) are deposited on a Si(001) hydrophobic surface immediately after rinsing the surface in a Au aqueous solution at room temperature (RT). 17) When Au-contaminated Si(001) surfaces were thermally oxidized, nanosize protuberances were observed by AFM.…”