Novel ZnO:Al contacts to CdZnTe for X- and gamma-ray detectors.

CdZnTe (CZT) has made a significant impact as a material for room-temperature nuclear-radiation detectors due to its potential impact in applications related to nonproliferation, homeland security, medical imaging, and gamma-ray telescopes. In all such applications, common metals, such as gold, platinum and indium, have been used as electrodes for fabricating the detectors. Because of the large mismatch in the thermal-expansion coefficient between the metal contacts and CZT, the contacts can undergo stress and mechanical degradation, which is the main cause for device instability over the long term. Here, we report for the first time on our use of Al-doped ZnO as the preferred electrode for such detectors. The material was selected because of its better contact properties compared to those of the metals commonly used today. Comparisons were conducted for the detector properties using different contacts, and improvements in the performances of ZnO:Al-coated detectors are described in this paper. These studies show that Al:ZnO contacts to CZT radiation detectors offer the potential of becoming a transformative replacement for the common metallic contacts due to the dramatic improvements in the performance of detectors and improved long-term stability.

Electro-thermal control of aluminum-doped zinc oxide/vanadium dioxide multilayered thin films for smart-device applications.

We demonstrate the electro-thermal control of aluminum-doped zinc oxide (Al:ZnO) /vanadium dioxide (VO2) multilayered thin films, where the application of a small electric field enables precise control of the applied heat to the VO2 thin film to induce its semiconductor-metal transition (SMT). The transparent conducting oxide nature of the top Al:ZnO film can be tuned to facilitate the fine control of the SMT of the VO2 thin film and its associated properties. In addition, the Al:ZnO film provides a capping layer to the VO2 thin film, which inhibits oxidation to a more energetically favorable and stable V2O5 phase. It also decreases the SMT of the VO2 thin film by approximately 5-10 °C because of an additional stress induced on the VO2 thin film and/or an alteration of the oxygen vacancy concentration in the VO2 thin film. These results have significant impacts on technological applications for both passive and active devices by exploiting this near-room-temperature SMT.

Extreme tunability in aluminum doped zinc oxide plasmonic materials for near-infrared applications.

Plasmonic materials (PMs), featuring large static or dynamic tunability, have significant impact on the optical properties due to their potential for applications in transformation optics, telecommunications, energy, and biomedical areas. Among PMs, the carrier concentration and mobility are two tunable parameters, which control the plasma frequency of a metal. Here, we report on large static and dynamic tunability in wavelengths up to 640 nm in Al-doped ZnO based transparent conducting degenerate semiconductors by controlling both thickness and applied voltages. This extreme tunability is ascribed to an increase in carrier concentration with increasing thickness as well as voltage-induced thermal effects that eventually diminish the carrier concentration and mobility due to complex chemical transformations in the multilayer growth process. These observations could pave the way for optical manipulation of this class of materials for potential transformative applications.

Effects of surface potential on growth of ZnO nanorod arrays investigated by electric force microscopy.

The electric and Kelvin force probe microscopy were used to investigate the surface potentials on the ZnO seed layer, which shows a remarkable dependence on the annealing temperature. The optimum temperature for the growth of nanorod arrays normal to the surface was found to be at 600 degrees C, which is in the range of right surface potentials and energy measured between 500 degrees C and 700 degrees C. We demonstrated from both electric and Kelvin force probe microscopy studies that surface potential controls the growth of ZnO nanorods, illustrating the fact that this is a promising technique to visualize the control of ZnO nanorod arrays by studying their surface potentials. This study will provide important understanding of growth of other nanostructures.

Oral versus intravenous steroids in acute exacerbation of asthma--randomized controlled study.

BACKGROUND: Use of corticosteroids in asthma is a must however the route of administration of steroid in acute exacerbation is a matter of debate. Intravenous steroids used very frequently in clinical practice may not offer any advantage over oral steroids. AIM: To compare to the efficacy of oral vs intravenous steroids in adults admitted with acute exacerbation of bronchial asthma. METHODS: Adults admitted to hospital with acute exacerbation of asthma were randomized to receive oral prednisolone 100 mg once daily or hydrocortisone 100 mg i.v. 6 hourly for 72 hrs following admission. All patients concurrently received inhaled corticosteroids and bronchodilators. Improvements in peak expiratory flow rate (PEF) from baseline were compared for 72 hrs. RESULTS: A total of 65 patients were randomized, 34 received oral prednisolone and 31 received intravenous hydrocortisone. Both groups were matched at baseline for age (40 +/- 13.11 vs 44 +/- 16.23, p 0.27) and percentage prediction both pre (20.11% +/- 6.17 vs 20.58% +/- 4.78, p 0.73) and post bronchodilator (24.35% +/- 5.43 vs 25.38% +/- 5.01, p 0.43). After 72 hrs both groups had improvement in PEF which was statistically insignificant (53.23% +/- 9.54 vs 55.87% +/- 10.34, p 0.28). CONCLUSION: Corticosteroids administered orally and IV had similar efficacy in the treatment of adults hospitalized with acute exacerbation of bronchial asthma.

Surface plasmon resonance in CdSe semiconductor coated with gold nanoparticles.

We have grown CdSe semiconductor films on glass substrates and the films were coated with Au nanoparticles of 10 nm in size by the pulsed-laser deposition technique. The films demonstrate a large enhancement of Raman intensity and photoluminescence of CdSe semiconductor via excitation of surface plasmon resonances in proximate gold metal nanoparticles deposited on the surface of CdSe film. These observations suggest a variety of approaches for improving the performance of devices such as photodetectors, photovoltaics, and related devices, including biosensors.

Influence of doping rate in Er3+:ZnO films on emission characteristics.

High-quality Er(3+):ZnO films were grown by the pulsed-laser deposition technique for 0.5 and 2 wt. % Er doping. Two peaks were observed at approximately 1.54 microm in the photoluminescence spectra of samples with 2 wt. % doping contrary to only one peak in the 0.5 wt. % doped sample. Both peaks were found to be strongly temperature dependent. The microscopic studies clearly illustrate that the appearance of the additional peak is attributed to the environment of Er(3+) ions in the form of ErO(6) clusters, which are optically active centers in the ZnO matrix. These results are very important for designing waveguides for telecommunications.