Direct optical evidence of BursteinÀMoss shift (BMS) in conduction band of cubic c-In 2 O 3 nanowires is reported herein. The optical property of degenerate semiconducting oxide c-In 2 O 3 has been investigated by thermoreflectance (TR) spectroscopy. Lowtemperature TR spectra clearly show a series of band-edge excitons for c-In 2 O 3 . The threshold energy for the exciton series was determined. One transition feature of direct gap caused by BMS was detected in all TR spectra from 20 to 300 K. The Femi-level (E F ) energy above conduction-band edge (E C ) is determined to be E F À E C ≈ 92 meV. The energy value causes a calculated electron density of ∼2.1 Â 10 19 cm À3 . The direct gap of c-In 2 O 3 with BMS is 3.43 eV at 300 K. Free exciton, bound exciton complexes, donorÀacceptor pair transition, and defect emissions have been evaluated by photoluminescence (PL) measurements from 10 to 300 K. Photoresistivity change (i.e., 5.71 Â 10 À2 f 4.85 Â 10 À2 Ω-cm) under the illumination of halogen lamp (5 mW 3 cm À2 ) for c-In 2 O 3 thin-film nanorods was detected. The experimental results show In 2 O 3 nanocrystals an appropriate candidate applied not only for light-emitting devices but also for photoelectric-conversion cells.

The α-phase Bi(2)O(3) (α-Bi(2)O(3)) is a crucial and potential visiblelight photocatalyst material needless of intentional doping on accommodating band gap. The understanding on fundamental optical property of α-Bi(2)O(3) is important for its extended applications. In this study, bismuth oxide nanowires with diameters from tens to hundreds nm have been grown by vapor transport method driven with vapor-liquid-solid mechanism on Si substrate. High-resolution transmission electron microscopy and Raman measurement confirm α phase of monoclinic structure for the as-grown nanowires. The axial direction for the as-grown nanowires was along < 122 >. The band-edge structure of α-Bi(2)O(3) has been probed experimentally by thermoreflectance (TR) spectroscopy. The direct band gap was determined accurately to be 2.91 eV at 300 K. Temperaturedependent TR measurements of 30-300 K were carried out to evaluate temperature-energy shift and line-width broadening effect for the band edge of α-Bi(2)O(3) thin-film nanowires. Photoluminescence (PL) experiments at 30 and 300 K were carried out to identify band-edge emission as well as defect luminescence for the α-Bi(2)O(3) nanowires. On the basis of experimental analyses of TR and PL, optical characteristics of direct band edge of α-Bi(2)O(3) nanowires have thus been realized.

This study examines how patterns of racial and ethnic segregation in U.S. metropolitan areas vary by household structure. Specifically, using tract-level summary files from the 2000 decennial census, we estimated levels of metropolitan segregation for different racial and ethnic groups by household composition and poverty status. We find that when using the dissimilarity index, white households with children, and especially poor ones, are more segregated from black, Hispanic, and Asian households than are white households as a whole. Results from the interaction index provide complimentary information. In large part because nonpoor white married-couple households are more numerous than other groups in most metropolitan areas, such households tend to have relatively less interaction with other racial and ethnic groups, and black and Hispanic households in particular. In contrast, minority group members often live in neighborhoods with a high proportion of non-Hispanic white households. Among all three minority group families with children, nonpoor married householders had the highest levels of interaction with whites. These results show that household structure shapes racial and ethnic residential patterns in U.S. metropolitan areas.

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