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Color control of the white photoluminescence (PL) from carbon-incorporated silicon oxide is demonstrated. The carbon-incorporated silicon oxide was fabricated by carbonization of porous silicon in acetylene flow (at 650 and 850 °C) followed by wet oxidation (at 650 and 800 °C). It was shown that PL color can be controlled in the range of blue-white and yellow-white by selecting the porosity of starting porous silicon as well as the carbonization and oxidation temperatures. Low-temperature oxidation resulted in bluish light emission in lower porosity series, while high-temperature oxidation promoted yellow-white light emission. The maximal integral intensity of PL was observed after oxidation at 800 °C. It was shown that white PL from carbon-incorporated silicon oxide has blue and yellow-white PL bands originating from different light-emitting centers. The origin of blue PL is attributed to defects in silicon dioxide. Some trap levels at the interface of the carbon clusters and silicon oxide are suggested to be the origin of the yellow-white light emission. [ABSTRACT FROM AUTHOR]

Nanostructured porous silicon (PS) optical filters have been proposed for their use in biological and chemical sensing applications. PS, however, presents a reactive surface that must be adequately passivated in order to achieve the required chemical stability mandatory for sensing applications. In the present work, thermal carbonization (TC) by acetylene decomposition is shown to provide effective passivation of a PS internal surface. Thermally carbonized PS optical filters are stable even in strong oxidizing environments such as absolute ethanol. Moreover, it is shown that the TC process, as opposed to more commonly used oxidation treatments, has only minor effects on the optical properties of PS. Thus, the optical performance of PS interference filters is preserved after the carbonization process. In addition, the hydrophilicity of the PS device surface can be adjusted by setting the appropriate TC process temperature. These results show that it is possible to produce low-cost, reusable, chemically stable PS optical devices for sensing applications. [ABSTRACT FROM AUTHOR]

The present research experiments the applicability of x-ray texture analysis in investigating the properties of paper coatings. The preferred orientations of kaolin, talc, ground calcium carbonate, and precipitated calcium carbonate particles used in four different paper coatings were determined qualitatively based on the measured crystal orientation data. The extent of the orientation, namely, the degree of the texture of each pigment, was characterized quantitatively using a single parameter. As a result, the effect of paper calendering is clearly seen as an increase on the degree of texture of the coating pigments. The effect of calendering on the preferred orientation of kaolin was also evident in an independent energy dispersive spectrometer analysis on micrometer scale and an electron spectroscopy for chemical analysis on nanometer scale. Thus, the present work proves x-ray texture analysis to be a potential research tool for characterizing the properties of paper coating layers. [ABSTRACT FROM AUTHOR]

Presents information on a study which used an isothermal microcalorimetric method to analyze photoinduced effects in porous silicon. Impact of aging to porous silicon; Methodology; Theory of the beam of light; Results and discussion; Conclusions.

Reports on the oxidation behavior of porous silicon and its link to illumination during etching. Autocatalytic oxidation behavior at room temperature caused by the unrelaxed surface; Removal using thermal treatment in a nitrogen atmosphere.

Examines the thermal oxidation of free-standing porous silicon thin film. Use of differential scanning calorimeter and thermogravimeter; Effect of humid storage condition on thermal oxidation rate; Calculation of the change in enthalpy and activation energy for first oxidation reaction; Analysis of backbond using Fourier transform infrared spectroscopy.