Initial oxidation processes on hydrogenated silicon surfaces studied by in situ Raman spectroscopy
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The influence of the solution pH on H-terminated silicon surfaces in different electrolytes was investigated by in situ confocal Raman microscopy. This study provides Raman evidence that the initial oxidation of the hydrogenated silicon surface could occur by two paths. In the lower pH solution, the H-terminated silicon surface could be directly oxidized by the attack of OH-; in the higher pH solution, the surface oxidation occurs in the second layer by the insertion of OH- into the back bond of Si-H (Si-Si), in which an intermediate species of -O3SiH could be found. In the study of the influence of electrolytes, it was found that F- ion could assist and accelerate the oxidation reaction, while the attack of OH- ion is essential to the initial oxidation processes. By taking advantage of Raman spectroscopy in the study of the low frequency region and analyzing the results from various samples, the assignment of the band located at about 629 cm(-1) is discussed in detail and attributed to the vibrations of the silicon hydride and multiphonon structure. (C) 2001 The Electrochemical Society.