Articles you may be interested inThe cooling effect on structural, electrical, and optical properties of epitaxial a-plane ZnO:Al on r-plane sapphire grown by pulsed laser deposition Appl. Phys. Lett. 101, 151907 (2012); 10.1063/1.4759032 Effect of substrate temperature on the properties of transparent conductive ZnO:Al thin films prepared by RF sputtering J. Vac. Sci. Technol. A 29, 051506 (2011); 10.1116/1.3610175 Structural, optical, and photocatalytic properties of ZnO:Al nanowall structure deposited on glass substrate by spray pyrolysis J. Vac. Sci. Technol. A 27, 885 (2009); 10.1116/1.3093878Comprehensive investigation of structural, electrical, and optical properties for ZnO:Al films deposited at different substrate temperature and oxygen ambient Aluminum doped zinc oxide (2nO:A.l) films were deposited on ( 1170) oriented sapphire substrates heated to 200 "C with a radio-frequency (rf) power ranging from 25 to 170 W for a deposition rate in the range 0.7-27.4 nm min -* by rf-magnetron sputtering from a ZnO target mixed with A&O3 of 2 wt. %. All of the films deposited were (0001) oriented singlecrystalline films with an internal stress. The stress was increased and degraded the crystallinity of the epitaxial film as a deposition rate was increased, and thus the Hall mobility and the resistivity of the film were, respectively, decreased and increased. However, the resistivities obtained were in the range about 1.4-3.0X 10 -4 Q cm, the values comparable to those for indium tin oxide film presently used as a transparent electrode. 3613

ZnO:Al films were deposited on (12̄10) oriented sapphire substrates heated up to 400 °C by rf magnetron sputtering from a ZnO target mixed with Al2O3 of 2 wt%. Films deposited on a substrate heated to a temperature in the range 50–350 °C were (0001) oriented single crystals but those grown at 400 °C consisted of crystallites with the (0001) and (11̄01) orientation. The former films had relatively smooth surfaces whereas the latter exhibited very rough surfaces. Electrical properties such as resistivity, carrier concentration, and the Hall mobility were measured as a function of substrate temperature. The carrier concentration decreased as the substrate temperature was increased up to 300 °C, although the Al content remained unchanged in this temperature range. From these measurements, it was found that the native donors were important as a source of carriers, even in ZnO:Al films. However, it was found that the Hall mobilities for films with a thickness of more than 200 nm experienced minor changes over a growth temperature range from 50 to 350 °C. The minimum resistivity obtained was about 1.5×10−4Ω cm, a value comparable to that for indium tin oxide film.

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The authors have proposed a new combustion process called the Plume Ignition Combustion Concept (PCC), in which a plume of the hydrogen jet is spark-ignited just after hydrogen is injected to accomplish combustion of a plume of rich mixture. With an optimal combination of injection timing, ignition timing and controlled jet geometry, this combustion process markedly improved thermal efficiency by reducing cooling loss which is an essential element to be reduced for improving thermal efficiency in hydrogen engine. In this study, in order to evaluate the cooling loss in hydrogen engine, characteristics of local cooling loss of PCC combustion are evaluated by measuring heat flux in two locations, one in the leading location and the others in the trailing location in the combustion chamber. As a result, it was found that local cooling heat flux in the leading direction of the jet injected showed extremely high level compare to trailing direction and spatially averaged cooling loss of the combustion chamber in injection angle of 15° of PCC combustion. By enlarging injection angle to 25°, thermal efficiency was improved and local heat flux in the leading direction is also mitigated. This result indicated that capturing local heat flux, especially in the leading direction of the injected jet, is a key to improve thermal efficiency.