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We have tried to develop a new procedure to prepare the clean surface of a silicon single crystal. We successfully prepared the contamination free bare silicon surface with ultraviolet cleaning followed by HF dipping with low concentration HF obtained by dilution by organic free ultrapure water, at room temperature under the atmospheric condition. X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and ultraviolet photoelectron spectroscopy measurements proved thus prepared surface has a hydrogen monoatomic layer terminating the dangling bonds of silicon. The hydrogen termination was found to have remarkable passivation effect against surface oxidation reaction. A silicon thin-film epitaxially grown on the prepared surface was confirmed to have perfect crystal structure and high-purity level by scanning electron microscopy, reflection high-energy electron diffraction, Raman spectroscopy and secondary ion mass spectroscopy.

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We have measured Raman spectra of diamond with nanometer size, called cluster diamond. The Raman bands assigned to sp2 and sp3 clusters have been observed at around 1600 and 1322 cm−1, respectively. This result suggests that the cluster diamond slightly contains the sp2 cluster. The Raman band assigned to sp3 cluster is found to shift by −10 cm−1, compared with that of bulk crystal and to be asymmetric with some tailing toward lower Raman frequency. The observed Raman spectrum agrees well with that calculated by a phonon confinement model. The crystallite size of the cluster diamond estimated from the phonon confinement model agrees approximately with that estimated from x-ray measurement. Raman spectroscopy gives some information about the crystallite size of diamond particles with nanometer size.

SynopsisThe stabilized fibers prepared by heating PAN and a PAN copolymer in air and under reduced pressure have been examined by IT-IH spectroscopy in order to determine their chemical structures. Three kinds of reactions, cyclization, dehydrogenation, and oxygen uptake are found to occur almost simultaneously in the stabilization process in air by digital difference spectrum method. The effect of the comonomer is confirmed to accelate the dehydrogenation reaction and also the formation of acridone ring in the thermal stabilization in air by kinetic study.

Raman spectra of diamond powders with size less than 2 μm have been measured as a function of the particle size. The Raman line was found to become more asymmetric with some tailing towards lower Raman shifts, broader, and weaker with decreasing particle size. The observed result can be explained by a phonon confinement effect rather than by a strain effect. This work predicts that it is very difficult to detect Raman spectra of diamond particles with size less than ∼50 Å. A broad Raman band, whose intensity becomes stronger with decreasing particle size, was observed around 600 cm−1 in the spectra of diamond powders with particle size less than 2 μm. We hypothesize that the broad band arises from transverse acoustic phonons near the Brillouin zone boundary because of the relaxation in the wave vector selection rule.

Raman spectra of diamondlike amorphous carbon (a-C) films prepared under atmosphere with various hydrogen gas content have been measured as a function of excitation wavelength. The Raman spectral profiles vary with excitation wavelength depending on electronic absorption spectra associated with π-π* electronic transitions. Dependence of Raman spectra on excitation wavelength is interpreted in terms of π-π* resonant Raman scattering from aromatic rings with various sizes rather than polyene chains. The relative intensity of a 1400 cm−1 band against a 1530 cm−1 band is found to decrease with an increase of sp3 content in a-C films. It is shown that the relative intensity can be used as a parameter for sp3 content.

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