One-dimensional ͑1D͒ WO 2 nanorods were synthesized by hot-filament metal vapor deposition at high-pressure Ar flow without using any catalyst. The 1D WO 2 nanorods grew on the roots and were a few micrometers long and 50-100 nm wide. The x-ray diffraction pattern shows that the as-synthesized 1D WO 2 nanorods are the monoclinic structure in space group P2 1 / c, and the roots are the ␤ tungsten crystal of the cubic structure in space group Im3m. Field-emission-gun transmission electron microscopy images and selected-area electron diffraction patterns further confirm that the monoclinic 1D WO 2 nanorods consist of the ͑011͒ planes and preferentially grow along the ͗011͘ direction. According to these results, an uncatalyzed vapor-solid process is suggested to be the mechanism of growth of the as-synthesized 1D WO 2 nanorods. In comparison with the Raman scattering of three-dimensional WO 2 bulk powders, the Raman bands of the 1D WO 2 nanorod are blueshifted and narrower, indicating phonon confinement associated with the 1D WO 2 nanorod.

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We report the mixing performance of a GaAs microstrip ring resonator in which a Schottky photodetector is monolithically integrated in a coupling gap. A spectrum of down-conversion between an optically modulated RF signal and an independently applied LO (Local Oscillator) signal is demonstrated and the system conversion loss of RF to IF (Intermediate Frequency) is measured as a function of LO frequency and compared with other data.

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Single-element contacts, Pd or Ni, on various p-InP substrates grown by liquid-encapsulation Czochralski (LEC) and by metal-organic chemical vapor deposition were investigated. Pd or Ni contacts on the substrates supplied by one certain manufacturer were found to be ohmic with a minimum contact resistivity of ∼5×10−5 Ω cm2 after annealing between 420 and 500 °C. However, ohmic behavior was not observed for these contacts on other substrates. Hall measurement, double-crystal x-ray diffractometry, and photoluminescence technique were used to evaluate the substrates. It was speculated that existence of intrinsic defects, such as P vacancies and other possible defects, in p-InP grown by LEC method may be responsible for the observed difference in ohmic behavior. A defect-assisted tunneling mechanism is proposed to account for the observed ohmic behavior of single-element contacts on certain p-InP substrates. This approach is potentially useful for making ohmic contacts to other compound semiconductors.