Differential permittivity sensor using microstrip terminated cross-shaped resonator structure for material characterization

A differential planar microwave resonator permittivity sensor for material characterization is proposed in this paper. The sensor is based on asymmetric terminated cross-shaped resonator (TCSR) to provide multi-band notch frequency characteristics, allowing permittivity measurement of a small dielectric material under test (MUT) with a single resonator. Differential sensing is robust against varying ambient factors that cause frequency variations in the measurements. The dielectric properties of the MUT can be measured from the difference in notch frequencies with the reference material. To illustrate the technique, a tri-band sensor is prototyped using the proposed resonator configuration to measure the permittivity of both solid and liquid samples. The empirical equations for the determination of the MUT permittivity in relation to the notch frequencies have been derived. The sensor operates at 0.97, 1.69, and 2.91 GHz with an average sensitivity of 1.18, 4.45, and 1.22 MHz, respectively. The measured results are in a good agreement with the theoretical analysis

XPS and PLE studies on the band edge states of ZnSß{219}x̳Tex̳ thin films

In this work, the band edge states of ZnS1-xTex alloys grown by molecular beam epitaxy were studied using X-ray photoelectron spectroscopy (XPS) and photoluminescence excitation (PLE) techniques. Six ZnS1-xTex samples with x values ranging from 2.5 to 100% are studied by XPS using monochromatized Al Kα( 1486.6eV) radiation. Their valence band XPS spectra are investigated and analyzed. The characteristics PI and PII valence band states were observed to shift to lower binding energy as Te composition increases. On the other hand, the valence band maximum in the photoemission spectra was found to move toward the Fermi level at higher Te composition. These observations are believed attributed to the mixture of ionic and covalent bonding in the alloy and the large difference in electronegativity between S and Te atoms. Besides, two of the above ZnS1-xTex samples with x = 2.5 and 8.6% were characterized by the PLE technique. The peak energy of the excitation spectrum is determined to be 3.59eV and 3.33eV for the alloy with x = 2.5 and 8.6% respectively, which are quite close to their corresponding band edge. The observed broadening in the transition below the band edge of the excitation bands is believed caused by direct excitation on the Te isoelectronic centers in this alloy system

Rocksalt MgS solar blind ultra-violet detectors

Studies using in-situ Auger electron spectroscopy and reflection high energy electron diffraction, and ex-situ high resolution X-ray diffraction and electron backscatter diffraction reveal that a MgS thin film grown directly on a GaAs (100) substrate by molecular beam epitaxy adopts its most stable phase, the rocksalt structure, with a lattice constant of 5.20 angstrom. A Au/MgS/n(+)-GaAs (100) Schottky-barrier photodiode was fabricated and its room temperature photoresponse was measured to have a sharp fall-off edge at 235 nm with rejection of more than three orders at 400 nm and higher than five orders at 500 nm, promising for various solar-blind UV detection applications. Copyright 2012 Author(s). This article is distributed under a Creative Commons Attribution 3.0 Unported License. [http://dx.doi.org/10.1063/1.3690124

Additional file 1: of Self-Assembled Formation of Well-Aligned Cu-Te Nano-Rods on Heavily Cu-Doped ZnTe Thin Films

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