The structure, surface morphology, composition, and optical properties of ZnO/GaN/Si thin films were

investigated by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), infrared (IR) absorption spectra, and photoluminescence (PL) spectra. Methods Samples and measurements First, GaN thin films were grown on Si (111) substrate by PLD at the growth temperature of 800°C using a GaN ceramic target. The film deposition was carried out in a stainless steel vacuum chamber evacuated by a turbomolecular pump to a base pressure of 5.6 × 10−5 Pa. A pulsed Nd:YAG laser with a wavelength of 1,064 nm (repetition 10 Hz, duration 10 ns) was focused by a lens on the ZnO target at an angle of incidence of 45°. During the deposition, the laser incident energy was maintained at 300 mJ/pulse. The size of the ablation spot is about 0.5 mm in diameter. Thiazovivin manufacturer A series of Si (111) substrate was placed at 40 mm from the target surface. For the ZnO target ablation and even thin film fabrication, GaN target and substrate rotated reversely with a frequency of 7 rpm. GaN films were deposited in the nitrogen background of 1.3 Pa, and depositing time was 15 min. The thickness of GaN thin films measured RG7112 research buy is about 50 nm. Second, the samples were placed on a quartz carrier and annealed in

a high-temperature tube quartz furnace. After the furnace reached the equilibrium temperature of 1,000°C the

carrier with the GaN samples was placed in a constant temperature region of the furnace. Flowing N2 was introduced into the tube for 5 min at a flow rate of 100 ml/min to flush out the residual air. Then, we terminated N2 flow and introduced NH3 into the tube at a flow rate of Fossariinae 800 ml/min for 20 min. Finally, the NH3 was flushed out by N2 introduced into the tube for another 5 min before the carrier was removed from the furnace. Third, ZnO thin films were fabricated on GaN (111) template by PLD at a growth temperature of 400°C in O2 ambience with a pressure of 1.3 Pa using a ZnO ceramic target. The laser incident energy was maintained at 200 mJ/pulse, and depositing time was 60 min. The thickness of ZnO thin films is about 600 nm, which was measured by the weight technique. The structural properties of thin films were studied by Rigaku D/max-rB XRD (Tokyo, Japan) spectroscopy with Cu Kα line radiation at 0.15418 nm. The surface morphology and the microstructure were studied using FESEM (QUANTA 250, FEI Co., Hillsboro, OR, USA). The IR buy NVP-BSK805 spectra were acquired using a BRUKER TENSOR27 spectrophotometer (Bruker Optik Gmbh, Ettlingen, Germany; wavenumber range 400 to 4,000 cm−1, optical resolution 4 cm−1, transmission mode). The optical properties of ZnO thin films were characterized by photoluminescence spectra with the excitation wavelength of 320 nm pumped by Xe lamp.