ARTICLES YOU MAY BE INTERESTED INThe effect of oxygen partial pressure (P O 2 ) on polarity and crystalline quality of AlN films grown on nitrided a-plane sapphire substrates by pulsed direct current (DC) reactive sputtering was investigated as a fundamental study. The polarity inversion of AlN from nitrogen (c)-polarity to aluminum (+c)-polarity occurred during growth at a high P O 2 of 9.4×10 3 Pa owing to Al-O octahedral formation at the interface of nitrided layer and AlN sputtered film which reset the polarity of AlN. The top part of the 1300 nm-thick AlN film sputtered at the high P O 2 was polycrystallized. The crystalline quality was improved owing to the high kinetic energy of Al sputtered atom in the sputtering phenomena. Thinner AlN films were also fabricated at the high P O 2 to eliminate the polycrystallization. For the 200 nm-thick AlN film sputtered at the high P O 2 , the full width at half-maximum values of the AlN (0002) and (1012) X-ray diffraction rocking curves were 47 and 637 arcsec, respectively.

In the present work, Zn-ZrO2 nanocomposite coatings were deposited on the copper substrate through DC and pulse electrodeposition technique with low current density (10 mA/cm2). The effect addition of ZrO2 nanoparticles and pulse current were studied. The surface morphology, microhardness and erosion resistance of Zn-ZrO2 nanocomposite coating were evaluated. The result shows that, with the addition of ZrO2 particles, the surface morphology of Zn-ZrO2 nanocomposite coating was smoother. Phase identification by XRD confirm that Zn layer had been sucessfully deposited. The presence of ZrO2 nanoparticles was not detected. Compared to DC, pulsed current electrodeposition technique showed higher cathodic efficiency, better microhardness and good erosion resistance.

Aluminium nitride (Aln) is a promising semiconductor material for use as a substrate in high-power, high-frequency electronic and deep-ultraviolet optoelectronic devices. We study the feasibility of a novel Aln fabrication technique by using the Al/Gan substitution reaction method. the substitution method we propose here consists of an Al deposition process on a Gan substrate by a sputtering technique and heat treatment process. the substitution reaction (Al + Gan = Aln + Ga) is proceeded by heat treatment of the Al/Gan sample, which provides a low temperature, simple and easy process. C-axis-oriented Aln layers are formed at the Al/Gan interface after heat treatment of the Al/Gan samples at some conditions of 1473-1573 K for 0-3 h. A longer holding time leads to an increase in the thickness of the AlN layer. The growth rate of the AlN layer is controlled by the interdiffusion in the Aln layer. Aluminium nitride (AlN) is a promising semiconductor material for use as a substrate in high-power, highfrequency electronic and optoelectronic devices. It can be used as a substrate in AlGaN-based ultraviolet C (UV-C) optoelectronic devices owing to its wide bandgap (above 6 eV) 1 , UV transparency 2 , and close lattice constant with that of AlGaN 3. AlN can be grown in two forms: film and bulk. AlN films have been fabricated by various methods, such as metal-organic vapour-phase epitaxy (MOVPE) 4,5 , hydride vapour phase epitaxy (HVPE) 6,7 , pulsed laser deposition (PLD) 8,9 , molecular beam epitaxy (MBE) 10,11 , or sputtering 12,13 , to improve its crystalline quality, surface area, growth rate, or lower its processing temperature. Annealing techniques have been demonstrated to improve the crystalline quality of AlN films 14-16. To facilitate the further development of AlN crystal growth, several researchers have developed original and unconventional techniques. For example, the pyrolytic transportation method 17 , the liquid phase epitaxy (LPE) method using a Ga-Al binary solution 18 , Al-Sn flux growth 19 , AlN fabrication by using Al and Li 3 N solid sources 20 , and elementary-source vapour-phase epitaxy (EVPE) 21 have been demonstrated. In the pyrolytic transportation method 17 , α-Al 2 O 3 is used as an Al-source material, and it is heated at 2223 K to form Al 2 O gas in the nitrogen gas flow. The Al 2 O gas is transported to the growth zone to react with nitrogen gas at 2023 K on a sintered AlN plate for 30 h, which yields a rod-like AlN crystal (48-mm long). The advantages of this method are an economically friendly α-Al 2 O 3 source and good crystalline quality of AlN. Wu et al. 21 used metallic Al and nitrogen gas as source materials to grow an AlN crystal, which they called elementary-source vapour-phase epitaxy (EVPE). They grew the AlN with a growth rate of 18 μm/h under an optimum growth zone temperature of 1823 K. The advantages of this method are that it is conducted at a temperature lower than that of the sublimation method using no hazardous gas. Regarding the LPE methods, Adachi et al. 18 grew a 1-µm-...