光纤基底TiNi形状记忆合金薄膜制备工艺

将TiNi基记忆合金薄膜与光纤相结合可制成智能化、集成化且成本经济的微机电系统和微传感器件.本文采用磁控溅射法在二氧化硅光纤基底上制备TiNi记忆合金薄膜,系统讨论了溅射工艺参数以及后续退火处理对薄膜质量的影响.采用自研制光纤镀膜掩膜装置在直径为125μm的光纤圆周表面上形成均匀薄膜.实验表明:在靶基距、背底真空度、Ar气流量和溅射时间一定的条件下,溅射功率存在最佳值;溅射压强较大时,薄膜沉积速率较低,但薄膜表面粗糙度较小.进行退火处理后,薄膜形成较良好的晶体结构,Ti_49.09Ni_50.91薄膜中马氏体B19′相和奥氏体B2相共存,但以B19′为主.根据本文研究结果,在玻璃光纤基底上制备高质量的TiNi基记忆合金薄膜是可实现的,本工作为下一步研制微机电系统和微型传感器做了基础准备.     

小角x射线散射确定TiNi薄膜中晶化粒子的长大激活能

用小角x射线散射技术研究以直流磁控溅射方法制备TiNi合金薄膜其退火生成的晶化粒子的长大行为.发现在室温下溅射的TiNi合金薄膜存在小于1nm尺寸的微空洞,将退火后薄膜的小角x射线散射强度扣除退火前微空洞产生的小角x射线散射强度,用这种方法得到的散射强度遵从Porod定律;而用通常方法扣除背底得到的散射强度结果不满足Porod定律.TiNi合金薄膜在733—793K之间退火晶化粒子的长大激活能Eg=301kJmol. 关键词： TiNi薄膜 晶化粒子 长大激活能     

退火温度和溅射时间对磁控溅射法制备Mg2Si薄膜的影响

采用磁控溅射法和原位退火工艺在钠钙玻璃衬底上制备 Mg2Si 薄膜。首先在钠钙玻璃衬底上交替溅射沉积两层Si、Mg 薄膜,冷却至室温后原位退火4 h,制备出一系列 Mg2Si 薄膜样品。通过 X 射线衍射仪(XRD) 、 扫描电子显微镜(SEM)对所得薄膜样品的晶体结构和表面形貌进行表征, 讨论了退火温度和溅射Si/Mg/Si/Mg 时间对制备 Mg2Si 薄膜的影响。结果表明,采用磁控溅射法在钠钙玻璃衬底上交替溅射两层Si、Mg 薄膜, 通过原位退火方式成功制备出单一相的 Mg2Si 薄膜,溅射Si/Mg/Si/Mg 的时间为12.5/9/12.5/9 min,退火温度为550 ℃ 时,制备的 Mg2Si 薄膜结晶度最好,连续性和致密性最强。这对后续 Mg2Si 薄膜器件的设计与制备提供了重要的参考。 积两层Si、Mg 薄膜, 冷却至室温后原位退火4 h, 制备出一系列 Mg2Si 薄膜样品. 通过 X 射线衍射仪(XRD) 、 扫描 电子显微镜(SEM)对所得薄膜样品的晶体结构和表面形貌进行表征, 讨论了退火温度和溅射Si/Mg/Si/Mg 时间 对制备 Mg2Si 薄膜的影响. 结果表明, 采用磁控溅射法在钠钙玻璃衬底上交替溅射两层Si、Mg 薄膜, 通过原位退火 方式成功制备出单一相的 Mg2Si 薄膜, 溅射Si/Mg/Si/Mg 的时间为12.5/9/12.5/9 min, 退火温度为550 ℃ 时, 制 备的 Mg2Si 薄膜结晶度最好, 连续性和致密性最强. 这对后续 Mg2Si 薄膜器件的设计与制备提供了重要的参考.     

周期性多层膜合金化制取的TiNi形状记忆薄膜的室温微结构特征

用掠入射X射线衍射及X射线反射对磁控溅射制取的等原子比Ni／Ti周期性多层膜晶化热处理 后的TiNi形状记忆薄膜室温微结构进行了研究.TiNi形状记忆薄膜在深度方向的相分布和元 素分布是不均匀的，都是一种多层结构.室温下其微结构特征为最外层是Ti氧化膜，再下层 是Ti₃Ni₄,B19’马氏体相和少量的B2奥氏体相的三相混合物，靠近 基体为主要相成分马氏体，最后是Ni和Si界面反应层.X射线反射率的拟和结果显示薄膜微结 构的分析是合理的.薄膜中相深度分布的不均匀性主要是动力学因素决定的. 关键词： 相深度分布 形状记忆 TiNi 多层膜     

利用表面磁光克尔效应监测Ni薄膜生长的物相转变

利用磁控溅射方法制备了不同厚度和退火处理的Ni薄膜.表面磁光克尔效应研究表明:冷基底无退火处理的Ni薄膜为软磁性,退火处理的Ni薄膜为铁磁性质,且无退火处理的Ni金属膜磁性随膜厚的增加而增强.分析认为,冷基底条件下Ni膜是非晶态生长,且膜内存有大量缺陷,经退火处理的Ni膜发生了重融再生长,形成了大颗粒结晶,膜内晶粒内缺陷大量消失.     

磁控溅射制备Y2O3-TiO2薄膜形貌的研究

室温下采用射频磁控溅射法,在硅衬底上制备了Y₂O₃-TiO₂氧化物复合薄膜.利用XRD(X-ray diffraction)和AFM( atomic force microscopy)分析观察了退火前后样品的物相、形貌等变化,讨论了致密薄膜的生长机理.实验发现,溅射功率越大,薄膜的平整度和致密度越好.对热处理前后样品的结晶结构和表面形貌的分析结果显示,在本实验参数范围内,随着溅射功率的增大,更多的Y₂O_{3关键词： 2}O₃-TiO₂薄膜')" href="#">Y₂O₃-TiO₂薄膜 表面形貌 原子力显微镜 磁控溅射     

不同衬底和CdCl2退火对磁控溅射CdS薄膜性能的影响

在科宁7059玻璃, FTO, ITO, AZO四种衬底上磁控溅射CdS薄膜, 并在CdCl₂+干燥空气380 ℃退火, 分别研究了不同衬底和退火工艺对CdS薄膜形貌、结构和光学性能的影响. 扫描电子显微镜形貌表明: 不同衬底原位溅射CdS薄膜的形貌不同, 退火后相应CdS薄膜的晶粒度和表面粗糙度明显增大. XRD衍射图谱表明: 不同衬底原位溅射和退火CdS薄膜均为六角相和立方相的混相结构, 退火前后科宁7059玻璃, FTO, AZO衬底上CdS薄膜有 H(002)/C(111) 最强衍射峰, ITO衬底原位溅射CdS薄膜没有明显的最强衍射峰, 退火后出现 H(002)/(111) 最强衍射峰. 紫外-可见分光光度计分析表明: AZO, FTO, ITO, 科宁7059玻璃衬底CdS薄膜的可见光平均透过率依次减小, 退火后相应衬底CdS薄膜的可见光平均透过率增大, 光学吸收系数降低; 退火显著增大了不同衬底CdS薄膜的光学带隙. 分析得出: 上述结果是由于不同衬底类型和退火工艺对CdS多晶薄膜的形貌、结构和带尾态掺杂浓度改变的结果. 关键词： CdS薄膜 磁控溅射 退火再结晶 带尾态     

磁控溅射功率对β-Ga2O3薄膜特性的影响

近年来,第三代宽禁带半导体材料β-Ga₂O₃受到越来越多的关注,在材料制备、掺杂、刻蚀等方面都有广泛研究.射频磁控溅射是常用的β-Ga₂O₃薄膜制备方法之一,而磁控溅射法制膜往往需要进行退火处理以提高薄膜质量.本文研究溅射功率对射频磁控溅射在C面蓝宝石基底上制备得到的β-Ga₂O₃薄膜特性的影响. X射线衍射(XRD)、原子力显微镜(AFM)和扫描电子显微镜(SEM)表征结果表明,随着溅射功率的增大,半峰宽呈现先增大后减小再增大的趋势,晶粒尺寸变化与之相反.此外,通过积分球式分光光度计,研究了溅射功率对β-Ga₂O₃薄膜光学特性的影响.光学特性方面,薄膜吸光度随着波长的增加,先升高后下降、再升高再下降,最后吸收边在700 nm附近截止,不同溅射功率制备的薄膜吸收光谱都存在两个吸收峰.     

溅射制备Ta2O5薄膜的表面形貌与光学特性

在室温条件下利用溅射Ta₂O₅靶材的方法制备了Ta₂O₅薄膜,并采用将薄膜两侧的反射率光谱进行比较的简便方法分析评估薄膜的光吸收,发现溅射制备薄膜的额外光吸收源是溅射引起的缺氧形成的,选择适当的溅射功率和含氧比例的工作气体能有效地消除这些缺陷、不用任何加温处理就可制备得到表面平坦和高致密度的高品质Ta₂O₅薄膜. 关键词： 2O₅薄膜')" href="#">Ta₂O₅薄膜 光吸收 表面形貌 磁控溅射     

原位退火温度对Mg_2Si薄膜结构及方块电阻的影响

采用磁控溅射法和原位退火工艺在钠钙玻璃衬底上制备Mg_2Si半导体薄膜.首先在钠钙玻璃衬底上依次溅射一定厚度的Si、Mg薄膜,冷却至室温后原位退火4h,在400~600℃退火温度下制备出一系列Mg_2Si薄膜样品.采用X射线衍射仪(XRD)、扫描电子显微镜(SEM)对Mg_2Si薄膜样品的晶体结构和表面形貌进行表征,利用四探针测试仪测试薄膜样品的方块电阻,讨论了原位退火温度对Mg_2Si薄膜结构、表面形貌及电学性能的影响.结果表明,采用原位退火方式成功在钠钙玻璃衬底上制备出单一相的Mg_2Si薄膜,退火温度为550℃时,结晶度最好,连续性和致密性最强,方块电阻最小.这对后续Mg_2Si薄膜器件的设计与制备提供了重要的参考.     

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.     

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.     

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.     

Multi-pulse operation of a Kerr-lens mode-locked femtosecond laser

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.     

Propagation of Helmholtz-Gauss beams in weak turbulent atmosphere

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.     

An effective method for reducing speckle noise in digital holography

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.     

Influence of purity of HfO2 on reflectance of ultraviolet multilayer

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.     

Speech enhancement by array crosstalk resistant ANC and spectrum subtraction

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.