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Research involving lifetime measurements as a method for characterizing 'defect' properties of epitaxial layers is described and discussed.

This paper describes Raman spectroscopy of microstructured silicon (Si), which is used for electronic displays, solar cells, and other applications. Enhanced Raman scattering was found for excimer laser crystallized polycrystalline Si (ELC poly-Si) thin films, texture-structured Si, black Si, and porous Si. Raman scattering of those materials reflects mainly the conditions at projections on their surfaces. Atomic force microscopy and Raman spectroscopy for ELC poly-Si indicated that hillocks and ridges are located at grain boundaries where the defect density is relatively large and the thermal stress in the films is somewhat relaxed. The enhancement effect was shown to be useful for detecting a local vibration mode that could not be easily detected for mirror-finished Si. The variation in the enhancement ratio with the incident light wavelength was examined for comparison with the electromagnetic model. [ABSTRACT FROM AUTHOR]

The thermoelectric properties of polycrystalline binary narrow-bandgap intermetallic RuGa3 and RuIn3 compounds have been investigated in the temperature range from 373 K to 973 K. These compounds exhibit semiconductor-like transport properties with large Seebeck coefficients of -560 μV/K and 280 μV/K at 373 K for RuGa3 and RuIn3, respectively. The Seebeck coefficient of RuGa3 changed rapidly from large negative to large positive values around 500 K, which is consistent with our calculation based on the full-potential-linearized-augmented-plane-wave method. In contrast, RuIn3 is a p-type material at its operating temperature. The dimensionless figures of merit ZT of pure compounds reached maximum values of 0.13 and 0.17 at about 973 K and 773 K, respectively. The potential maximum ZT value was evaluated using the Boltzmann transport equation and can exceed unity by electron- or hole-doping for both compounds. By substituting Co for Ru in RuIn3, n-type thermoelectric materials (ZTmax = 0.10 at 473 K) were obtained. We suggest that ZT will be enhanced by further effective electron-doping. [ABSTRACT FROM AUTHOR]

Stress and defects in polycrystalline silicon (poly-Si) for thin-film transistor (TFT) were investigated on the aspect of difference of techniques between excimer laser annealing (ELA) with extremely short pulse duration and continuous-wave laser lateral crystallization (CLC). Micro-Raman spectroscopy was used for characterization. Mapping measurements with high spatial resolution were carried out for the optical-phonon mode at ∼520 cm-1 to observe distribution of stress and defects. Defects were characterized also by local-vibration modes (LVMs) in ∼2000 cm-1 region, where LVMs were induced by terminating dangling bonds at defects with hydrogen atoms. Significant tensile stress was found for both ELA and CLC, which magnitude is dominated by the thermal stress. The stress in ELA poly-Si tends to relax in the vicinity of grain boundaries. Densities of defects in grains and dangling bonds at grain boundaries in CLC poly-Si films were apparently smaller than those in ELA films. Those differences are attributed to cooling rates of ELA and CLC. The defects in CLC poly-Si distribute extending along the laser scan direction parallel to TFT channel current, which is effective to prevent the deterioration of TFT characteristics by residual defects. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]