共查询到20条相似文献,搜索用时 406 毫秒
1.
2.
Ghulam Murtaza Rai Muhammad Azhar Iqbal Yongbing Xu Iain Gordon Will Wen Zhang 《化学物理学报》2011,24(3):353-357
研究Ho3+掺杂对氧化锌半导体材料的微结构和磁学性质影响. 利用热蒸发技术制备了一系列沉积在Si(100)衬底的Zn1-xHoxO(x=0.0、0.04、0.05)薄膜. X射线光谱、表面形貌以及磁性的实验结果表明,Ho3+掺杂对ZnO薄膜材料的性能影响很大. X射线衍射图显示峰位出现高角度转变并且趋向于(101)取向,在ZnO晶格显示Ho3+置换. 扫描电子显微镜和能谱仪对薄膜的表面形貌以及化学 相似文献
3.
利用中频非平衡磁控溅射技术在单晶硅基底上沉积了类石墨碳膜, 采用Raman光谱、高分辨透射电子显微镜、原子力显微镜分析了薄膜微观结构和表面形貌; 采用纳米压痕仪和CSM摩擦磨损试验机测试了碳膜力学性能和摩擦学性能. 结果表明: 利用中频非平衡磁控溅射技术沉积的碳膜是一种以sp2键合碳为主、结构非晶、硬度适中、应力较低、表面粗糙度较大、摩擦性能优异的薄膜. 脉冲占空比对薄膜微观结构和性能有显著影响, 随着脉冲占空比的增大, Raman光谱D峰和G峰的强度比ID/IG先减小后增大, 而硬度随脉冲占空比的增大却呈现出相反的变化趋势, 即先增大后减小; 大气氛围中的摩擦性能测试表明, 本实验制备的薄膜具有优异的抗磨性能(~10-11 cm3/N-1. m-1)和承载能力(~2.5 GPa). 随脉冲占空比的增大, 薄膜摩擦系数变化甚微而磨损率却呈现先显著减小后轻微增大的变化趋势. 类石墨碳膜优异的摩擦学性能主要归因于其独特的结构、较低的内应力及良好的结构稳定性. 相似文献
4.
采用直流反应磁控溅射法,以高纯Ti为靶材,高纯O2为反应气体,制备了TiO2薄膜.研究了氧气流量对薄膜结晶取向、表面形貌和光学性能的影响.研究发现,TiO2薄膜主要呈锐钛矿TiO2(101)择优取向,当氧气流量较小时,薄膜中还含有金属Ti(100),氧气流量较大时,薄膜含TiO2(101)和TiO2(004),成多晶态;薄膜的粗糙度和颗粒大小都随氧气流量的增大而增大;薄膜在400~1100nm可见-近红外波段有较高的透射率并且其吸收峰随着氧气流量的增大而红移,当氧气流量为5sccm时,平均透射率最高. 相似文献
5.
采用射频反应溅射法在不同衬底上制备Zn3N2薄膜,然后对其原位氧化制备ZnO薄膜。利用X射线衍射分析(XRD)、扫描电子显微镜(SEM)和光致发光谱(PL)等表征技术研究了不同衬底对ZnO薄膜的结晶特性和发光性能的影响。XRD研究结果显示:Zn3N2薄膜在500 ℃原位氧化3 h后完全转变为ZnO薄膜,在玻璃和熔融石英衬底上制备的多晶ZnO薄膜无择优取向,而单晶硅(100)衬底上的多晶ZnO薄膜具有较好的沿(002)方向的择优取向。PL测试结果显示:硅和熔融石英衬底上的多晶ZnO薄膜发光性能良好,激子复合产生的紫外发光峰很强,且半高宽较窄,而来自于深能级发射的绿色发光峰很弱;而玻璃衬底上的多晶ZnO薄膜发光性能较差。 相似文献
6.
染料敏化太阳电池(DSC)中的纳米薄膜电极 是决定太阳电池光电转换性能的重要组成部分. 为改善薄膜电极特性, 采用了不同浓度的TiO2溶胶对DSC光阳极导电玻 璃和纳米TiO2多孔薄膜进行不同方式的界面处理. 利用X射线衍射方法对制备得到的多孔薄膜以及溶胶经高温处理 后致密层中纳米TiO2颗粒的尺寸及晶型进行了测试. 采用高分辨透射电子显微镜和场发射扫描电子 显微镜观察了纳米颗粒及薄膜微结构形貌. 采用强度调制光电流谱/光电压谱分析了TiO2溶 胶的不同处理方式对电子传输和复合的影响. 在100 mW· cm-2光强以及暗环境下分别测试了DSC的伏安输出性能以及暗电流. 结果表明, 不同浓度和处理方式均能较好地抑制暗电流. 溶胶处理后光生电子寿命τn延长, 电子传输平均时间τd相应缩短. 采用浓度为0.10 mol·L-1的 溶胶对导电玻璃和多孔膜同时处理, DSC的宏观输出特性最佳, 短路电流密度Jsc提高了10.9%, 光电转换效率η提高了11.9%. 相似文献
7.
8.
Ghulam Murtaza Rai Muhammad Azhar Iqbal Yong-bing Xu Iain Gordon Will Qasim Mahmood 《化学物理学报》2012,25(3):313-317
采用热蒸镀技术和后续氨退火制备了Ho掺杂GaN稀磁半导体薄膜. X射线衍射分析表明,所有的峰属于六角纤锌矿结构. 利用扫描电子显微镜和能量色散谱分别进行了表面形貌和成分分析. 用振动样品磁强计在室温测定了Ga1-xHoxN(x=0.0,0.05)的室温铁磁性. 磁性测量结果表明,未掺杂薄膜GaN具有抗磁性行为,而Ho掺杂Ga0.95Ho0.05N的薄膜表现出铁磁行为. 相似文献
9.
采用溶胶凝胶法在玻璃基片上制备了ZnO及Ni, Fe共掺杂的Zn0.95-xNi0.05FexO (x=0, 0.005, 0.01, 0.03, 0.05) 薄膜. 通过扫描电镜(SEM) 和X射线衍射(XRD) 研究了薄膜样品的表面形貌和晶体结构. 结果表明所有样品都具有(002) 择优取向, Fe掺杂导致ZnO: Ni薄膜的晶体质量变差, 晶粒尺寸减小, 但适当的Fe掺杂有利于获得致密、 均匀的薄膜. XPS测试结果表明样品中Ni离子的价态为+2价, Fe离子的价态为+2价和+3价.室温光致发光(PL) 测量表明, 所有样品均观察到较强的紫外发光峰, 蓝光双峰和绿光发光峰. ZnO: Ni薄膜的发光强度可以通过Fe掺杂进行有效调节. 进而我们讨论了Ni, Fe共掺杂ZnO样品的发光机理. 相似文献
10.
11.
A multi-conjugate adaptive optics (MCAO) can offer a possibility of widening field of view (FOV) characterized by the isoplanatic angle, and the choose of conjugate height becomes a basic problem for MCAO, which influences the size of iosplanatic angle. Considering the application of lidar, the isoplanatic angle's expressions of two deformable mirrors (DMs) MCAO for uplink and downlink are deduced. The effects of conjugate heights for dual-conjugate AO are thoughtfully discussed, and the isoplanatic angles are further analyzed. The results show that the isopanatic angle varies with the conjugate height and reaches the maximum as the conjugate height is at the optimal altitude. Moreover, the optimal conjugate height changes with the propagation distance. 相似文献
12.
Due to the limit of response speed of the present single-photon detector, the code rate is still too low to come into practical use for the present quantum key distribution (QKD) system.A new idea is put up to design a quick single-photon detector.This quick single-photon detector is composed of a multi-port optic-fiber splitter and many avalanche photo diodes (APDs).Au of the ports with APDs work on the time division and cooperate with a logic discriminating and deciding unit driven by the clock signal.The operation frequency lies on the number N of ports, and can reach N times of the conventional single-photon detector.The single-photon prompt detection can come true for high repetition-rate pulses.The applying of this detector will largely raise the code rate of the QKD, and boost the commercial use. 相似文献
13.
14.
A.C mismatches are studied by Raman spectral characterization of PolyA, PolyC, and their equimolar complex in solution of 0.14 mol/L Na ,pH7.0.Experimental results show that A·C mismatches occur to be A/B (mainly A) conformers, and unlike Watson-Crick base pairing, this kind of mismatches is stabilized by only one hydrogen bond involving cytosine N4H2 and adenine N7.The formation of A·C complex makes the base stacking interactions much stronger, and conformation of the backbone more ordered, which leads to obvious Raman hypochromic effect with some shifts in corresponding bands. 相似文献
15.
40-GHz clock modulated signal as a pump to improve the efficiency of four-wave mixing (FWM)-based wavelength conversion in a 26.5-km dispersion shifted fiber (DSF) is investigated. The experimental results demonstrate that the conjugated FWM component has higher intensity with the clock pumping than that with the continuous-wave (CW) light pumping. The improvement of FWM-based wavelength conversion efficiency is negligible when the pump power is less than Brillouin threshold. But when the pump power is greater than Brillouin threshold, the improvement becomes significant and increases with the increment of pump power. The improvement can increase up to 9 dB if pump power reaches 17 dBm. 相似文献
16.
Our experimental results show that the presence of a proper amount of negative group velocity dispersion is essential to multi-pulse operation of a Kerr-lens mode-locked femtosecond laser. We demonstrate that the pulse separations and the number of pulses contained within a cavity round trip are strongly dependent on the initial perturbations. The results allow us to get a better understanding on the influences of the convoluted self-phase modulation and intra-cavity dispersions on the stable multi-pulse oscillation in a Kerr-lens mode-locked femtosecond laser. 相似文献
17.
Based on the Rytov approximation of light propagation in weak turbulent atmosphere,the closed-form expressions of field and average irradiance of each one of the four fundamental families of Helmholtz-Gauss (HzG)beams:cosine-Gauss beams,stationary Mathieu-Gauss beams,stationary parabolic-Gauss beams,and Bessel-Gauss beams,which are propagating in weak turbulent atmosphere,are obtained.The results show that the field and average irradiance can be written as the product of four factors:complex amplitude depending on the z-coordinate only,a Ganssian beam.a factor of complex phase perturbation induced by atmospheric turbulence,and a complex scaled version of the transverse shape of the non-diffracting beam.The effect of weak atmospheric turbulence on irradiance distribution of the HzG beam can be ignored. 相似文献
18.
Xin Kang 《中国光学快报(英文版)》2008,6(2)
An effective method for reducing the speckle noise in digital holography is proposed in this paper.Different from the methods based on classical filtering technique,it utilizes the multiple holograms which are generated by rotating the illuminating light continuously.The intensity images reconstructed by a series of holograms generated by rotating the illuminating light possess different speckle patterns.Hence by properly averaging the reconstructed intensity fields,the speckle noises can be reduced greatly.Experimental results show that the proposed method is simple and effective to reduce speckle noise in digital holography. 相似文献
19.
The impurities in two kinds of HfO2 materials and in their corresponding single layer thin films were determined through glow discharge mass spectrum technology and secondary ion mass spectrometry(SIMS) equipment respectively.It was found that ZrO2 was the main impurity in the two kinds of HfO2 either in the original HfO2 materials or in the electron beam deposited films.In addition,the difference of Zr content in the two kinds of HfO2 single laver films was much laxger than that of the other impurities such as Ti and Fe.which showed that it was just ZrO2 that made the difference between the optical performance of the film products including the two kinds of HfO2.With these two kinds of HfO2 and the same kind of SiO2.we deposited HfO2/SiO2 multilayer reflective coatings at the wavelength of 266 nm.Experimental results showed that the reflectances of these two mirrors were about 99.85% and 99.15% respectively,which agreed well with the designed results what were based on the optical constants obtained from the corresponding single layer thin films. 相似文献
20.
References: 《声学学报:英文版》2008,27(1):85-96
Microphone array-based speech enhancement has great importance for speech communications and speech recognition. To reduce the aperture of the microphone array and to increase the effect of the speech enhancement will greatly broaden the application areas of the microphone array. An array crosstalk resistant adaptive noise cancellation method is therefore presented. And then an improved spectral subtraction algorithm is further cascaded to obtain better enhancement results. Theoretic analysis and experiments indicate that the proposed scheme needs only a very small microphone array while it simultaneously achieves a higher SNR improvement. Besides, the proposed scheme can be used in many noisy environments and is easy for real-time implementation. 相似文献