蓝宝石基片的处理方法对ZnO薄膜生长行为的影响

采用反应射频磁控溅射方法，在经过不同方法处理的蓝宝石基片上，在同一条件下沉积了ZnO薄膜.利用原子力显微镜、X射线衍射、反射式高能电子衍射等分析技术，对基片和薄膜的结构、表面形貌进行了系统表征.研究结果显示，不同退火条件下的蓝宝石基片表面结构之间没有本质的差异，均为α-Al₂O₃ (001)晶面，但基片表面形貌的变化较大.在不同方法处理的蓝宝石基片上生长的ZnO薄膜均具有高c轴取向的织构特征，但薄膜的表面形貌差异较大.基片经真空退火处     

NH3气氛处理制备p型ZnO薄膜及性能表征

采用NH₃气氛处理直流/射频共溅射方法制得的ZnO：Al薄膜,从而获得Al+N共掺p型ZnO薄膜.XRD,场发射扫描电子显微镜测试及Hall效应测试发现,处理温度对ZnO薄膜的结构和电学性能具有较大的影响,其中处理温度为700℃时,薄膜具有较好的c轴择优取向,并且薄膜表面平整,结构紧密,晶粒大小均匀,无明显空洞和裂缝,具有良好的表面质量,晶粒尺寸约为40—60nm,薄膜的导电类型由n型转变为p型. 关键词： p型ZnO Al+N共掺杂 直流/射频共溅射     

不同氮流量制备Mn3CuNx薄膜及其电、磁输运性质的研究

采用对靶磁控溅射方法在单晶Si(100)基片上制备了反钙钛矿结构的Mn₃CuN_x薄膜.通过控制制备过程中的反应气体氮气(N₂) 流量(N₂/Ar+N₂), 研究了氮含量对Mn₃CuN_x薄膜结构及物理性能的影响.分别利用X射线衍射仪、俄歇电子能谱、 原子力显微镜、X射线光电子能谱、物理性能测试系统和超导量子干涉仪, 对所制备薄膜的晶体结构、成分、表面形貌和电、磁输运性质进行了测试.结果表明:制备的薄膜均为反钙钛矿立方结构,且沿 (200) 晶面择优生长.随着氮含量的增大,薄膜表面粗糙度和颗粒度尺寸逐渐增大, 导致电阻率增加.氮含量对薄膜的电输运性质没有影响,所有薄膜电阻率均随着温度的降低逐渐增大, 呈现半导体型导电行为,这与对应的块体材料结果相反.Mn₃CuN_x薄膜随着测试温度的增大发生了 亚铁磁到顺磁的磁转变,且N含量的增大降低了磁有序转变温度,主要是由于N缺陷对Mn₆N八面体结构中 磁交换作用的影响所致.     

Fe掺杂对溶胶凝胶法制备的ZnO: Ni薄膜结构及发光特性的影响

采用溶胶凝胶法在玻璃基片上制备了ZnO及Ni, Fe共掺杂的Zn_0.95-xNi_0.05Fe_xO (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.     

蒸发条件对碘化铅多晶薄膜结构的影响

采用真空蒸发法在普通玻璃上制备了PbI₂多晶薄膜.研究了蒸发速率、蒸发源与衬底距离、薄膜厚度以及衬底温度等实验条件对所制备PbI₂多晶薄膜结构的影响.利用X射线衍射仪和扫描电子显微镜对样品进行了测试.结果表明，在衬底温度为室温时得到(001)择优取向的多晶PbI₂薄膜，即沿c轴垂直衬底方向取向生长的薄膜.当衬底温度升高时，薄膜的择优取向逐渐由(001)转向(003)，且晶体颗粒变大.薄膜中的内应力随衬底温度的升高而降低.     

γ-LiAlO2上a面ZnO薄膜的光谱特性研究

利用激光脉冲沉积(PLD)技术在(302)γ-LiAlO₂衬底上成功生长了非极性的a面(1120)ZnO薄膜，光致发光谱(PL)带边发射峰半峰宽仅为115meV.研究了非极性ZnO薄膜光谱特性的面内各向异性，发现随着入射光偏振方向改变，在偏振透射光谱上，吸收边移动了20meV，这与A、B激子和C激子的能量差一致；而在拉曼光谱上，激发光偏振方向的改变导致E₂模式的强度发生明显改变.     

p型ZnO薄膜的制备及特性

采用射频磁控溅射在Si片上制备ZnO薄膜，通过离子注入对样品进行N掺杂，在不同温度下进行退火并实现了p型转变.用扫描电子显微镜、X射线衍射和Hall测量对薄膜进行了表征，结果表明薄膜具有良好的表面形貌和高度c轴择优取向，退火后p型ZnO薄膜的最高载流子浓度和最低电阻率分别为1.68×10¹⁶cm^-3和41.5Ω·cm.讨论并分析了退火温度和时间对ZnO薄膜p型转变的影响.     

Cr2MC(M=Al, Ga)的电子结构、弹性和热力学性质的第一性原理研究

本文使用第一性原理的GGA/RPBE方法研究了Cr₂MC(M=Al, Ga)的电子结构、弹性和热力学性质. 研究发现两个化合物的体积压缩性几乎相同, 并且证实了在0—50 GPa范围内c轴始终较a轴更难以压缩并且结构始终是稳定的. 通过对内坐标的研究发现了Cr₂AlC中Cr离子的内坐标始终大于Cr₂GaC中Cr离子的内坐标. 使用准谐德拜模型得到的体弹模量在0 GPa下随着温度的升高而减小, 而在300 GPa下则随着温度的升高而增大. 对德拜温度的研究发现Cr₂GaC的值小于Cr₂AlC的值, 而对热膨胀系数、Grüneisen参数、熵和热容的计算发现Cr₂GaC的值大于Cr₂AlC的值. 对电子结构的分析发现Cr₂GaC的s和p电子在费米能级处的值大于Cr₂AlC的s和p电子的值, 而其他离子的电子分布几乎一致.     

半导体材料AAl2C4(A=Zn, Cd, Hg; C=S, Se)的电子结构和光学性质

采用基于密度泛函理论的第一性原理方法, 对具有缺陷型黄铜矿结构的半导体材料A^ⅡAl₂C₄^Ⅵ(A=Zn, Cd, Hg; C =S, Se)的构型和电子结构进行研究, 并系统考察了各晶体的光学性质. 对于线性光学性质, 五种晶体在红外区和部分可见光区具有良好的透光性能, 其中HgAl₂S₄和HgAl₂Se₄晶体具有适中的双折射率. 在非线性光学性质方面, 该类晶体倍频效应较强, 理论预测得到的二阶静态倍频系数均较大(>20 pm/V). 体系的倍频效应主要来源于价带顶附近以S/Se 价p轨道为主要成分的能带向含有较多Al/Hg 价p成分的空带之间的跃迁. 通过与已商业化的AgGaC₂晶体光学性质的对比, 结果表明HgAl₂S₄和HgAl₂Se₄是一类性能优良的红外非线性光学晶体材料.     

三元硅化物CaAlSi的结构和超导电性

应用线性响应的线性糕模轨道方法计算AlB₂型结构的新超导体CaAlSi的电子能带、声子谱及电子-声子耦合常数，并讨论了它们的超导电性.通过比较两种结构模型的计算结果可以看出：若CaAlSi中Al，Si原子沿c轴方向以—Al—Al—Al—(或—Si—Si—Si—) 排列，低频B_1g模式的声子频率沿A-L方向出现虚频, 使得这种结构处于不稳定状态，电子-声子耦合表现异常增大；若Al，Si原子沿c轴     

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.     

Hybrid Wavelength and Code Division Multiple Access in Optical Networks

A review of schemes for multiple access in fiber optic networks shows that a hybrid of wavelength and code division multiple access (WCDMA) combines the best features of both. In particular, the hybrid scheme retains the large information carrying capacity of wavelength division multiple access (WDMA) and flexibility of code division multiple access (CDMA). In this paper WDMA, optical CDMA (OCDMA), and WCDMA networks are discussed. In OCDMA networks, concept of incoherent and coherent coding including inverse decoding and matched filter is introduced. The delay performance of both WDMA and WCDMA networks, under the simple suboptimum access protocols based on cyclic search, is computed. It has been shown quantitatively that tuning delay significantly affects the delay performance of both WDMA and WCDMA networks. Futhermore, delay performance of WCDMA networks is always better than the WDMA networks for the same tuning delay, load, and number of users.     

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.     

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.     

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.     

Measurement of nonlinear coefficient of optical fiber based on small chirped soliton transmission

We measure the waveform and phase curves of short optical pulses before and after transmission over different lengths of fibers by use of the pulse analyzer with the frequency-resolved optical gating (FROG),and numerically simulate pulse evolution under the experimental conditions.The nonlinear coefficient of the fiber is given by comparing the experimental results with the numerical ones.Difference between the experiment and numerical simulation is analyzed.     

Resonance scattering of canonical elastic shells in absorbing fluid medium

Resonance scattering of elastic spherical shell and cylindrical shell while the surrounding fluid medium has absorption is studied. The normal mode solution derived using exact elastic theory and the separation of variables is still applicable. However, the scattering form function has to be modified for the absorbing medium, otherwise the unreasonable result would be obtained. The backscattering form function in the absorbing medium is redefined, and the form function of elastic spherical and cylindrical shell with vacuum or solid matter filled is calculated in various absorption conditions. The results show that the absorption of surrounding fluid leads to notable attenuation of the coincidence resonances in the mid-frequency, but it has a little influence on the low-frequency resonance scattering induced by the filler inside the shell.     

Single-beam self-referenced phase-sensitive surface plasmon resonance sensor with high detection resolution

A versatile and low-cost single-beam self-referenced phase-sensitive surface plasmon resonance(SPR)sensing system with ultra-high resolution performance is presented.The system exhibits a root-mean-square phase fluctuation of ±0.0028.over a period of 45 min.i.e.a resolution of±5.2×10-9 refractive index units.The enhanced performance has been achieved through the incorporation of three design elements:a true single-beam configuration enabling complete self-referencing so that only the phase change associated with SPR gets detected,a differential measurement scheme to eliminate spurious signals not related to the sensor response,and the elimination of retardation drifts by incorporating temperature stabilization in the liquid crystal phase modulato .Our design should bring the detection sensitivity of non-labeling SPR biosensing closer to that achievable by conventional fluorescence-based techniques.     

Influences of SiO2 protective layers and annealing on the laser-induced damage threshold of Ta2O5 films

Ta2O5 films are prepared on BK7 substrates with conventional electron beam evaporation deposition.The effects of SiO2 protective layers and annealing on the laser-induced damage threshold (LIDT) of the films are investigated.The results show that SiO2 protective layers exert little influence on the electric field intensity(EFI)distribution,microstructure and microdefect density but increase the absorption slightly.Annealing iS effective on decreasing the microdefect density and the absorption of the films.Both SiO2 protective layers and annealing are beneficial to the damage resistance of the films and the latter is more effective to improve the LIDT.Moreover,the maximal LIDT of Ta2O5 films is achieved by the combination of SiO2 protective layers and annealing.