Complex optical properties (ε=ε1+iε2) of polycrystalline bulk α-Ag2S are investigated by spectroscopic ellipsometry from 0.5 to 8.5 eV at room temperature. The acanthite structure (monoclinic) of α-Ag2S is confirmed by structural analysis. Multilayer analysis with Tauc-Lorentz dispersion model is applied to draw out ε from ellipsometric data. Ag2S shows absorption in the entire range of the visible spectrum with onset band gap of 1.07 eV; furthermore, six other interband transitions are identified whose energy positions accurately obtained by standard lineshape analysis of second-energy-derivative of point-by-point fit determined ε. Finally, we compared our data with reported theoretically calculated data, and origin of the main optical structures is discussed.

A novel, solution immersed silicon (SIS)-based sensor has been developed which employs the non-reflecting condition (NRC) for a p-polarized wave. The SIS sensor's response is almost independent of change in the refractive index (RI) of a buffer solution (BS) which makes it capable of measuring low-concentration and/or low-molecular-weight compounds.

The effect of annealing on SiGe films was investigated using scanning photoelectron spectroscopy ͑SPEM͒. Films annealed at a temperature above 950°C in N 2 ambient show a drastic morphological change. The difference in the chemical state between an islandlike surface and flat surface is dependent on the Si and Ge contents. In addition, the chemical state of the flat surface is closely related to differences in Si and Ge content, resulting in a donutlike shape. The oxidation of Ge is suppressed during the annealing process because of the lower heat of formation of GeO 2 than for SiO 2 . Thus, differences in content and the extent of oxidation are major determinants of the chemical state in the islandlike shape. The characteristic donutlike shape reflects kinetic changes in the SiGe content during the annealing process.

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