镁含量和热处理对Zn1-xMgxO薄膜结构和发光性能的影响

采用溶胶-凝胶工艺在玻璃衬底上制备了Zn1-xMgxO(x=0.1,0.2,0.3,0.4,0.5,0.6,0.7)薄膜.X射线衍射谱(XRD)测试结果发现,在0.1相似文献   

镁含量和热处理对Zn1-xMgxO薄膜结构和发光性能的影响

采用溶胶-凝胶工艺在玻璃衬底上制备了Zn_1-xMg_xO(x=0.1,0.2,0.3, 0.4,0.5,0.6,0.7)薄膜.X射线衍射谱(XRD)测试结果发现,在 0.1<x<0.3 范围内,薄膜仍然保持氧化锌六角纤锌矿结构,(002)面衍射峰位向大角度方向移动,超过0.3时出现氧化镁立方相.对镁含量为0.1,0.2,0.3薄膜的光致发光谱研究表明：紫外发光峰随镁含量的增加向短波方向移动.对于Zn_0.9Mg_0.1O薄膜,在5,5.5和6℃/min的升温速率下,升温速率越快结晶程度越好.在相同升温速率下,随着退火温度从500 ℃升高到560 ℃,样品的结晶程度变好,当退火温度达到590 ℃时,结晶质量下降. 关键词： 氧化锌 结构 禁带宽度 光致发光谱     

溶胶-凝胶法制备MgxZn1-xO薄膜的结构及光学特性

用溶胶-凝胶法制备了一系列的Mg_xZn_1-xO(0≤x≤0.3)薄膜,并用X射线衍射(XRD)和光致发光(PL)研究了不同的退火温度和Mg的掺杂含量对Mg_xZn_1-xO薄膜的结构和光学性质的影响.研究表明:Mg_xZn_1-xO薄膜为单相六角纤锌矿结构,并且具有沿c轴的择优取向;发现了中间热处理温度为350℃的Mg_xZn_1-xO薄膜退火温度的转折点为700℃,低于这个温度时随退火温度的升高,(002)衍射峰强度增强且掺Mg的薄膜既有紫外光又有绿光发射;800℃退火时,薄膜的(002)衍射峰强度减小,出现了(100)和(101)衍射峰,且掺Mg的薄膜只有紫外发光峰.不同的掺杂浓度对于发光也有影响,低于700℃退火时,ZnO薄膜只出现紫外发光峰,掺Mg的薄膜却出现了紫外和绿光两个发光峰.     

ZnO/Zn界面对纳米ZnO薄膜光学性质的影响

采用氧等离子体辅助电子束蒸发金属Zn后低温退火的方法制备纳米ZnO薄膜。利用X射线衍射(XRD)谱、拉曼(Raman)谱、X射线光电子能谱(XPS)以及光致发光(PL)谱等手段,分析了退火温度及ZnO/Zn界面对样品的结构和发光性质的影响。Raman结果表明随着退火温度的升高,界面模式(Es)振动减弱并向低波数方向移动。当退火温度为400℃时,界面振动消失,Zn全部转化成具有六方纤锌矿结构的ZnO,得到化学配比的纳米ZnO薄膜。PL谱表明,经400℃退火处理的样品紫外发射最强,发光性质最好。     

ZnO∶V薄膜后退火处理前后的微结构与发光特性

利用溶胶-凝胶(Sol-gel)法在单晶硅(100)衬底上分别制备了ZnO∶V薄膜和纯ZnO薄膜。为进一步研究后退火对ZnO∶V薄膜结构和发光性质的影响,在两段式快速退火后又在800℃下进行了后退火处理。X射线衍射的结果表明:后退火处理前,钒(V)的掺入使ZnO结晶质量变差,而800℃退火处理后,从ZnO的衍射峰中可以看出,相对于无V杂样品其结晶质量变好。扫描电子显微镜形貌图中可以看出制备的样品薄膜颗粒大小均匀,薄膜致密度较高。光致发光(PL)谱的研究表明:ZnO∶V薄膜在800℃退火处理后,紫外和绿带发光峰均增强,但紫外发光峰增强得更多;与同样条件下制备的纯ZnO薄膜的PL谱比较,发现V掺杂后样品的紫外激子复合发光峰的强度明显增强且峰位发生蓝移,而缺陷引起的绿带发光峰的强度降低。     

ZnO：V薄膜后退火处理前后的微结构与发光特性

利用溶胶-凝胶(Sol-gel)法在单晶硅(100)衬底上分别制备了ZnO:V薄膜和纯ZnO薄膜。为进一步研究后退火对ZnO:V薄膜结构和发光性质的影响,在两段式快速退火后又在800℃下进行了后退火处理。X射线衍射的结果表明:后退火处理前,钒(V)的掺入使ZnO结晶质量变差,而800℃退火处理后,从ZnO的衍射峰中可以看出,相对于无V杂样品其结晶质量变好。扫描电子显微镜形貌图中可以看出制备的样品薄膜颗粒大小均匀,薄膜致密度较高。光致发光(PL)谱的研究表明:ZnO:V薄膜在800℃退火处理后,紫外和绿带发光峰均增强,但紫外发光峰增强得更多;与同样条件下制备的纯ZnO薄膜的PL谱比较,发现V掺杂后样品的紫外激子复合发光峰的强度明显增强且峰位发生蓝移,而缺陷引起的绿带发光峰的强度降低。     

反应溅射氧化锌薄膜的结构特点及性质

以金属Zn(纯度为99.99%)作为靶材,采用离子束反应溅射法在玻璃衬底上溅射沉积了一系列ZnO薄膜样品。通过对薄膜样品X射线衍射(XRD)谱的分析,发现尽管溅射条件不同,但是ZnO薄膜只沿(0002)晶面取向生长。衬底温度和溅射气体的氧分压对薄膜沿c轴取向生长有影响,其中衬底温度的影响较明显。溅射过程中发现衬底温度为360℃最适合(0002)晶面的生长,在此温度下溅射获得了完全沿c轴取向生长且衍射峰最强的ZnO薄膜。室温下测量了ZnO薄膜的发射光谱,发现薄膜在紫外区(364nm附近)、蓝绿区(470nm附近)有较强的发光峰,在紫光区(398nm附近)、蓝光区(452nm附近)和红外区(722nm附近)有较弱的发光峰。ZnO薄膜在空气中退火,对薄膜的结构、发光和电学性质都有一定影响。合适的退火温度可以促进薄膜沿c轴的取向生长;退火后ZnO多晶薄膜的晶粒比未退火的略大;退火使部分发光峰的位置发生偏移并使薄膜的发光强度增强;退火使薄膜的电阻率显著增大,薄膜的电阻率随氧分压的增大而增大。     

退火处理对LaAlO_3薄膜发光特性的影响

在室温下,采用射频磁控溅射法在p-Si(100)衬底上制备了铝酸镧(LaAlO3)薄膜,分别在800℃,900℃和950℃下进行退火处理。利用X射线衍射(XRD)仪、原子力显微镜(AFM)、荧光分光光度计等研究了不同温度退火处理对LaAlO3薄膜结构、表面形貌及光学性质的影响。研究结果表明,LaAlO3薄膜样品在900℃开始由非晶向晶体转变,说明高温退火有利于提高结晶质量。光致发光(PL)谱测量发现样品在368,470nm位置处分别出现发光峰,各峰的强度随退火温度的升高逐渐增强,但峰位基本保持不变。根据吸收光谱和缺陷能级图,推测出368nm紫外光峰来源于电子从氧空位形成的缺陷能级到价带顶能级的跃迁,470nm附近的蓝光峰归因于电子从负价AlLa错位缺陷能级到价带顶能级的跃迁。     

利用P-MBE制备高质量MgxZn1-xO的结构和光学特性

利用等离子体辅助分子束外延(P-MBE)的方法,在c平面的蓝宝石衬底上制备了高质量的MgxZn1-xO合金薄膜。通过改变Mg源的温度,得到了不同Mg组份的MgxZn1-xO合金薄膜;通过引入ZnO的低温缓冲层,有效地提高了MgxZn1-xO合金薄膜的结晶质量。随着Mg组份的增加,MgxZn1-xO的X射线衍射的(002)衍射峰逐渐向大角度方向移动。对样品进行光致发光(PL)谱的测量,在室温下观察到了较强的紫外发光。随Mg浓度的增加,紫外发光峰向高能侧移动,并且发光峰逐渐展宽。通过对x=0.15的样品进行变温光谱的测量研究了紫外发光峰起因,得到了MgxZn1-xO的发光是来自于自由激子的发光。自由激子束缚能为54meV。     

退火工艺对含硅量子点SiC_x薄膜光谱特性的影响

采用磁控共溅射法并结合微波退火和快速光热退火工艺,在不同退火温度下制备了含硅量子点的富硅SiC_x薄膜。采用掠入射X射线衍射(GIXRD)、拉曼光谱和光致发光(PL)光谱技术对薄膜进行了表征,研究了退火工艺对薄膜中硅量子点数量、尺寸、晶化率以及发光峰的影响。结果表明:与快速光热退火相比,微波退火不但能降低硅量子点的形成温度(降低200℃),而且还能降低β-SiC量子点的形成温度(降低100℃);在相同退火温度下,微波退火制备的硅量子点的数量更多、晶化率更高、光致发光峰更强;采用1000℃温度的微波退火样品的硅量子点数量最多、尺寸最大(5.26nm)、晶化率最高(74.25%)、发光峰最强,说明微波退火能凝析出高质量的硅量子点。     

Guided-Wave Two-Dimensional Acousto-Optic Scanner Using Proton-Exchanged Lithium Niobate Waveguide

Two-dimensional scanning of a 0.6328 mum guided-light beam has been realized using noncolinear acousto-optic (AO) coplanar Bragg diffraction together with colinear AO guided-mode to substrate radiation-mode conversion in a Z-cut Xpropagation LiNbO3 proton-exchanged (PE) waveguide. The two surface acoustic (SAW) waves utilized are at the center frequencies of 500 and 200 MHz, propagating in the Y and X axes, respectively. Two-dimensional scanning of approximately 720 resolvable light beam spots, namely, 18 40 (horizontal vertical) scanning, has been demonstrated using a light beam of 1.0 mm aperture. The total number of resolvable beam spots can be greatly increased from 720 by simply utilizing SAW transducers of larger bandwidth and a light beam of greater aperture. It should also be possible to significantly increase the diffraction efficiency from 3 % by optimizing the parameters of the PE waveguide and the SAWs.     

Femtosecond Transform-Limited Pulse Generation by Compensating for the Linear Chirp of SPM Spectra in Dispersion Shifted Fibers

A simple technique of pulse compression, based on the linear chirp compensation of self-phase modulation (SPM) spectra in dispersion shifted fibers, is demonstrated. The optimization procedure is carried out, for a short span of a single-mode fiber, using a parabolic law, which describes the behavior of the squared output pulse width versus the pump peak power in the case of Gaussian pulses. The experimental results give a minimum pulse duration of 233 fs, which is in good agreement with the model. Shorter and coherent pulses, down to 90 fs, have been obtained by inserting an interference filter at the optical output.     

Effect ofγ-radiation on the spectral luminescence characteristics of impure cadmium tungstate crystals

Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation (5.5·10⁴ Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure crystals is analyzed (preliminarily). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997.     

Theoretical analysis and simulation of conjugate heights for dual-conjugate AO system in lidar

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.     

Quick single-photon detector with many avalanche photo diodes working on the time division

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.     

Sorting of bending magnets for the SSRF booster

The Shanghai Synchrotron Radiation Facility(SSRF)booster ring,a full energy injector for the storage ring,is deigned to accelerate the electron beam energy from 150MeV to 3.5GeV that demands high extraction efficiency at the extraction energy with low beam loss rate when electrons are ramping.Closed orbit distortion(COD)caused by bending magnet field uniformity errors which affects the machine performance harmfully could be effectively reduced by bending magnet location sorting.Considering the affections of random errors in measurement,both ideal sorting and realistic sorting are studied based on measured bending magnet field uniformity errors and one reasonable combination of bending magnets which can reduce the horizontal COD by a factor of 5is given as the final installation sequence of the booster bending magnets in this paper.     

Improvement of four-wave mixing-based wavelength conversion efficiency in dispersion shifted fiber by 40-GHz clock pumping

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.     

Characterization of PolyA and PolyC mismatches by Raman spectroscopy

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.