Thick GaN films were grown on the sapphire substrate by hydride vapour phase epitaxy. The properties of GaN films were found to be significantly influenced by the duration of exposing the sapphire substrate to ammonia...Thick GaN films were grown on the sapphire substrate by hydride vapour phase epitaxy. The properties of GaN films were found to be significantly influenced by the duration of exposing the sapphire substrate to ammonia prior to the GaN growth initiation. The crystalline quality of GaN films revealed by high resolution X-ray diffraction were strongly dependent on the nitridation time, which determined substrate surface topography. The different nitridation schemes strongly affected the morphology of GaN overlayers resulting in the blue shift of the main excitonic peak in photoluminescence spectra at room temperature.展开更多
Polyurethane-conjugated HgS nanocrystals with tunable sizes prepared by using biomimetic method. The obtained HgS nanoparticles with good dispersibility were characterized by Fourier transform infrared. Scanning elect...Polyurethane-conjugated HgS nanocrystals with tunable sizes prepared by using biomimetic method. The obtained HgS nanoparticles with good dispersibility were characterized by Fourier transform infrared. Scanning electron microscopy are used to envisage the binding of nanoparticles with functional groups. The polyurethane molecules can control nucleation and growth of HgS crystals by binding on the surface of nanocrystals to stabilize nanoparticles. Quantum confinement effect of polyurethane-conjugated HgS nanocrystals was confirmed by UV-Vis spectra. The nanoparticles exhibit a well-defined emission feature at about 291 nm. The fluorescence results reveal that the PU/HgS nanoparticles film is sensitive to Ba2＋, and a small amount of Ba2＋ makes the emissions increase rapidly. The emission is hardly affected by other common ions in water. The nanocomposite film is possible to become a special sensor material for Ba2＋.展开更多
基金National"863"Project of China (2001AA311100 and 2002AA305304) Sino French Cooperation Project:CNRS/ASC Chine 2003 Project(14915)
文摘Thick GaN films were grown on the sapphire substrate by hydride vapour phase epitaxy. The properties of GaN films were found to be significantly influenced by the duration of exposing the sapphire substrate to ammonia prior to the GaN growth initiation. The crystalline quality of GaN films revealed by high resolution X-ray diffraction were strongly dependent on the nitridation time, which determined substrate surface topography. The different nitridation schemes strongly affected the morphology of GaN overlayers resulting in the blue shift of the main excitonic peak in photoluminescence spectra at room temperature.
基金This work was supported by the National Natural Science Foundation of China （No.21102121）, the Shaanxi Province Council （No.2014JQ2077）, the China＇s Scholarship Council （No.2013JK0643）, and the Xianyang Normal University Council （No.13XSYK021）.
文摘Polyurethane-conjugated HgS nanocrystals with tunable sizes prepared by using biomimetic method. The obtained HgS nanoparticles with good dispersibility were characterized by Fourier transform infrared. Scanning electron microscopy are used to envisage the binding of nanoparticles with functional groups. The polyurethane molecules can control nucleation and growth of HgS crystals by binding on the surface of nanocrystals to stabilize nanoparticles. Quantum confinement effect of polyurethane-conjugated HgS nanocrystals was confirmed by UV-Vis spectra. The nanoparticles exhibit a well-defined emission feature at about 291 nm. The fluorescence results reveal that the PU/HgS nanoparticles film is sensitive to Ba2＋, and a small amount of Ba2＋ makes the emissions increase rapidly. The emission is hardly affected by other common ions in water. The nanocomposite film is possible to become a special sensor material for Ba2＋.
