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A new cycle model of a two-stage combined semiconductor thermoelectric device that is used as a heat pump is established. The influence of Joule heating due to the electric current and heat leak due to the temperature difference between the hot and the cold junctions on the performance of the system is investigated. The general expressions of three important performance parameters, the coefficient of performance (COP), the rate of heat pumping and the power input, are derived. The maximum COP and the corresponding parameters are calculated. The internal structure parameter

We report a room temperature study of the direct band gap photoluminescence of tensile-strained Ge/Si0.13Ge0.87 multiple quantum wells grown on Si-based germanium virtual substrates by ultrahigh vacuum chemical vapor deposition. Blueshifts of the luminescence peak energy from the Ge quantum wells in comparison with the Ge virtual substrate are in good agreement with the theoretical prediction when we attribute the luminescence from the quantum well to the cΓ1-HH1 direct band transition. The reduction in direct band gap in the tensile strained Ge epilayer and the quantum confinement effect in the Ge/Si0.13Ge0.87 quantum wells are directly demonstrated by room temperature photoluminescence.

Asymmetric light reflectance effect was observed in an anodic aluminum oxide on glass structure. The transmitted light from two sides of the films show the same colors, whereas the reflected light from two sides show complementary colors. The spectra analysis demonstrates that this asymmetric light reflectance effect can be ascribed to the asymmetric geometric structure of nanoscale aluminum networks. This effect may result in applications in many fields, especially in optical communication.

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