Violet/blue photoluminescence from CeO2 thin film

CeO2 thin film was fabricated by dual ion beam epitaxial technique. The violet/blue PL at room temperature and lower temperature was observed from the CeO2 thin film. After the analysis of crystal structure and valence in the compound was carried out by the XRD and XPS technique, it was inferred that the origin of CeO2 PL was due to the electrons transition from Ce4f band to O2p band and the defect level to O2p band. And these defects levels were located in the range of 1 eV around Ce4f band.

Violet/blue emission from hydrogenated amorphous carbon films deposited from energetic CH3+ ions and ion bombardment

Considering the complexity of the general plasma techniques, pure single CH3+ ion beams were selected for the deposition of hydrogenated amorphous (a) carbon films with various ion energies and temperatures. Photoluminescence (PL) measurements have been performed on the films and violet/blue emission has been observed. The violet/blue emission is attributed to the small size distribution of sp(2) clusters and is related to the intrinsic properties of CH3 terminals, which lead to a very high barrier for the photoexcited electrons. Ion bombardment plays an important role in the PL behavior. This would provide further insight into the growth dynamics of a-C:H films. (C) 2002 American Institute of Physics.

The PL "violet shift" of cerium dioxide on silicon

CeO2 thin film was fabricated by dual ion beam epitaxial technique. The phenomenon of PL violet shift at room temperature was observed, and the distance of shift was about 65 nm. After the analysis of crystal structure and valence in the compound were carried out by XRD and XPS technique, it was concluded that the PL shift was related with valence of cerium ion in the oxides. When the valence of cerium ion varied front tetravalence to trivalence, the PL peak position would move from blue region to violet region and the phenomenon of "violet shift" was observed.

Blue-violet photoluminescence from large-scale highly aligned boron carbonitride nanofibers

We report on the strong blue-violet photoluminescence (PL) at room temperature from the large-scale highly aligned boron carbonitride (BCN) nanofibers synthesized by bias-assisted hot filament chemical vapor deposition. The photoluminescence peak wavelength shifts in the range of 470-390 nm by changing the chemical composition of the BCN nanofibers, which shows an interesting blue and violet-light-emitting material with adjustable optical properties. The mechanism for the shift of the PL peaks at room temperature is also discussed. (C) 2000 American Institute of Physics. [S0003-6951(00)04427-2].

Influence of polarization orientation of violet light on the diffraction efficiency of bacteriorhodopsin

When a grating is recorded in a bacteriorhodopsin film by two linear parallel polarized beams together with anauxiliary violet light, the diffraction efficiency has a dependence on the polarization orientation of the violet light as well as its intensity. A method for calculating the diffraction efficiency of gratings in bacteriorhodopsin is proposed based on the two-state photochromic model, considering the saturation effect and the polarization status of all the involved lights. It is found that the polarization orientation of the violet light produces an approximate-cosine and an approximate-sine modulation on the steady-state diffraction efficiency separately at low and high intensities, respectively. The parallel polarized violet light can improve the steady-state diffraction efficiency to a larger degree than the perpendicularly polarized violet light when both are at their optimal intensities. The optimal intensity for the parallel polarized violet light is lower than that of the perpendicular polarized one. Thus, the improvement of the steady-state diffraction efficiency is less sensitive to the intensity of perpendicular polarized violet light than to that of parallel polarized violet light. (C) 2008 Optical Society of America.

酚酞型聚芳醚砜共聚物与共混物－(PP/BiS-T) PES共聚物和(PPS/PES-C)、(PPO/PES-C)共混物的合成、结构与性能研究

本工作旨在通过共聚、共混技术制备酚酞型聚芳醚砜共聚物(PP/BiS-T) PES和共混物(PPS/PES-C)、PPO/PES-C，以便改善酚酞型聚芳醚砜（PES－C）的加工性能（特别是注射加工性能）和耐溶剂性能。通过研究共聚物和共混物的微观结构，聚集态结构与性能的关系，探索改善酚酞型聚芳醚硕性能的有效途径第一部分：(PP/BiS-T) PES共聚物的合成、结构与性能(PP/BiS-T) PES共聚物是以4，4'二氯二苯砜（DCDPS）、酚酞（PP）和4，4'－二羟基二苯硫醚(BiS-T)为单体，采用固体无水K_2CO_3/NMP/TMSO_2 混合溶剂反应体系合成的。共聚反应规律研究表明：在NMP/TMSO_2混合溶剂中，共聚反应可以顺利进行，避免了交联反应的发生，并成功地合成了高分子量的(PP/BiS-T) PES共聚物。DSC分析结果表明(PP/BiS-T) PES系列属于无定形的均相共聚物体系，每一组成比例对应的共聚物只具有一个玻璃化转变温度。且随组成比例的改变呈线性变化，TBA分析结果与DSC基本一致，并证实了(PP/BiS-T) PES属于均相共聚物体系，而不是均聚物的共混物。TG分析表明：共聚物具有良好的耐热氧化稳定性BiS-T链节在分子链中起到了提高自身抗氧性的作用。1R光谱对共聚物的结构进行表征。~(13)C-NMR分析确认共聚物多属于无规共聚物。动态力学试验表明共聚物(PP/BiS-T) PES以及PES－C，在－100 ℃附近和0－100 ℃，存在着次级松驰与转变，并发现水分子的存在对这种转变（次级松驰）有一定的影响。共聚物的熔融流动性试验和溶解性试验表明共聚物(PP/BiS-T) PES具有稍好于PES－C的熔融流动性；溶解性与PES－C类似。力学试验说明共聚物属于强而硬类型的聚合物。第二部分：PPS/PES－C共混物的制备、聚集态结构与性能PPS/PES－C共混物是以联苯/二苯硕混合物为溶剂，采用溶液沉析方法制备的，DSC、WAXD，SEM和1R分析手段对共混物的聚集态结构和微观结构进行了表征。DSC分析认为共混物属于多相体系，PPS的结晶性随着PES－C含量增加而降低。DSC和SEM观察结果表明：相转变发生在PPS占40％左右。PPS占25％时，DSC曲线呈现出界面相玻璃化转变温度。共混物具有良好的耐热氧化稳定性和耐热分解稳定性。微晶大小计算结果：PES－C存在导致了PPS微晶大小降低。WAXD曲线表明PPS占50％，共混物中的PPS具有较好的结晶性。SEM观察发现：随着PES－C含量增加，PES－C由分散相（PES－C50％）变为连续相（PES－C70％）。PPS占50％或低于50％时，共混物体系不仅发生了微观相分离，而且发生了宏观相分离。M.I.指数表明共混物中PPS为连续相时，共混物具有良好的熔融流动性。溶解性试验结果：共混物具有较好的耐溶剂性。第三部分：PPO/PES－C共混物的合成、结构与性能 PPO/PES－C共混物系用溶液－涂膜法，以氯彷为溶剂制备的。讨论了由同一共混物溶液浓度下制备的共混物的互溶性随组成的改变而变化。DSC分析结果：PPO/PES－C属于部分相溶性体系。利用Fox方程推导式计算结果表明PPO在富PES－C相中具有良好的分散性；而PES－C在富PPO相中的分散性较差。共混物(PPO/PES－C)试样经丙酮浸泡后，PPO（>50％）发生了溶剂诱导结晶现象，同时丙酮促使共混物发生完全相分离。结晶溶化热显示共混物中少量的PES－C存在有利于PPO的溶剂诱导结晶。TG分析表明共混物具有良好的耐热分解稳定性和耐热氧化分解稳定性。偏光显微镜下观察到PPO球晶的存在。SEM和FT－1R分别对共混物的形态结构和微观结构进行了表征。WAXD试验证实了丙酮处理的(PPO/PES－C)（70/30），（90/10）共混物中PPO的结晶性。溶解性试验表明：PPO掺入有助于 PES－C的耐溶剂性提高。

Room-Temperature Continuous-Wave Operation of InGaN-Based Blue-Violet Laser Diodes with a Lifetime of 15.6 Hours

We report our recent progress of investigations on InGaN-based blue-violet laser diodes (LDs). The room-temperature (RT) cw operation lifetime of LDs has extended to longer than 15.6 h. The LD structure was grown on a c-plane free-standing (FS) GaN substrate by metal organic chemical vapor deposition (MOCVD). The typical threshold current and voltage of LD under RT cw operation are 78 mA and 6.8 V, respectively. The experimental analysis of degradation of LD performances suggests that after aging treatment, the increase of series resistance and threshold current can be mainly attributed to the deterioration of p-type ohmic contact and the decrease of internal quantum efficiency of multiple quantum well (MQW), respectively.

Material Growth and Device Fabrication of GaN-Based Blue-Violet Laser Diodes

Studies on first GaN-based blue-violet laser diodes(LDs) in China mainland are reported.High quality GaN materials as well as GaN-based quantum wells laser structures are grown by metal-organic chemical vapor deposition method.The X-ray double-crystal diffraction rocking curve measurements show the full-width half maximum of 180" and 185" for (0002) symmetric reflection and (10(-1)2) skew reflection,respectively.A room temperature mobility of 850cm2/(V·s) is obtained for a 3μm thick GaN film.Gain guided and ridge geometry waveguide laser diodes are fabricated with cleaved facet mirrors at room temperature under pulse current injection.The lasing wavelength is 405.9nm.A threshold current density of 5kA/cm2 and an output light power over 100mW are obtained for ridge geometry waveguide laser diodes.

Blue-violet luminescence double peak of In-doped films prepared by radio frequency sputtering

ZnO films doped with different contents of indium were prepared by radio frequency sputtering technique. The structural, optical and emission properties of the films were characterized at room temperature using XRD, XPS, UV-vis-NIR and PL techniques. Results showed that the indium was successfully incorporated into the c-axis preferred orientated ZnO films, and the In-doped ZnO films are of over 80% optical transparency in the visible range. Furthermore, a double peak of blue-violet emission with a constant energy interval (similar to 0.17 eV) was observed in the PL spectra of the samples with area ratio of indium chips to the Zn target larger than 2.0%. The blue peak comes from the electron transition from the Zn-i level to the top of the valence band and the violet peak from the In-Zn donor level to the V-Zn level, respectively.