电泡模型研究

基于铁电体物理学的基本理论，研究了在外加电场中铁电薄膜的电畴结构。研究表明，在铁电材料为单轴各向异性薄膜，且在铁电薄膜中能够形成电畴的情形下，如果外加一定大小的电场，同时外加电场的方向与将要形成的电畴的预定极化方向相反的条件下，在铁电薄膜中就可以形成圆柱形电畴结构，称为电泡。本质上，电泡是铁电薄膜中电畴所承受的压缩力与扩张力稳定平衡的结果，是电畴的一种稳定结构。至于电泡尺度的大小，除了与外加的电场有关外，还应与所研究的材料有关。     

基于电感耦合等离子体刻蚀的LNOI脊形微结构制备

铌酸锂(LiNbO₃,LN)是一种广泛使用的介电材料,由于其电光系数大,透明范围大,本征带宽宽,因而在集成和非线性光学器件中极为重要。但绝缘体上铌酸锂薄膜(LNOI)的化学稳定性好,刻蚀速率慢,其微结构参数难以控制。针对以上问题,该文开展了基于电感耦合等离子体刻蚀(ICP-RIE)的LNOI脊形微结构的制备工艺研究,分析了腔室压强、气体总流量及刻蚀功率等参数对刻蚀速率、刻蚀倾角和表面粗糙度(RMS)的影响。研究表明,在优化的工艺条件下,LNOI薄膜的刻蚀速率达到24.9 nm/min,制备出刻蚀深度249 nm、刻蚀倾角76°、表面粗糙度(RMS)0.716 nm的LNOI脊形微结构。该文通过对刻蚀工艺与微观结构参数的研究,建立了基于ICP的LNOI微结构刻蚀方法,为控制LNOI脊形光波导和提升性能提供了工艺支撑。     

磁控溅射氧氩体积流量比对β-Ga2O3薄膜的影响

利用射频磁控溅射在c面单晶蓝宝石(Al₂O₃)衬底上制备Ga₂O₃薄膜,研究了溅射过程中通入氧气与氩气的体积流量比对经过异位高温后退火处理得到的β-Ga₂O₃薄膜特性的影响。利用X射线衍射仪(XRD)和原子力显微镜(AFM)对薄膜进行表征,结果表明β-Ga₂O₃薄膜沿着■晶面择优生长,具备较好的单一取向性。在氧氩体积流量比约为1∶20时,薄膜的结晶性能相对较好、表面晶粒分布较均匀、均方根粗糙度较小、晶粒尺寸较大。此外,吸收光谱表征结果表明,不同氧氩体积流量比下制备得到的β-Ga₂O₃薄膜的带隙变化范围为4.53～4.64 eV,在较低氧氩体积流量比下制备的β-Ga₂O₃薄膜表现出较优的光学性质,在波长200～300 nm内具有较好的吸收特性,表现出良好的深紫外光学特性。     

铁酸铋薄膜柔性化微纳制造及铁电性能

研究了铁酸铋薄膜的柔性化可控制造方法及其电畴调控动态。利用脉冲激光沉积法制备了周期性畴结构的铁酸铋薄膜,结合可控剥离技术,完成了铁酸铋薄膜从刚性基底到柔性基底的制备过程。利用原子力显微镜和压电力显微镜技术对柔性化铁酸铋薄膜的微观形貌和铁电特性进行表征。结果表明,柔性化后的铁酸铋薄膜保持完整的表面形貌特征(粗糙度保持不变),电畴反转特性保持可调,且保持良好的铁电特性及电畴反转响应。该研究为铁酸铋薄膜的柔性化制备提供了一种新思路。     

类四方 BiFeO3薄膜中新型极化拓扑结构研究

结合像差校正透射电子显微术和精密脉冲激光沉积技术，本文研究了生长在LaAlO₃衬底上的单层铁电BiFeO₃薄膜中应变调控和缺陷诱导的极化涡旋拓扑畴组态。HAADF-STEM成像揭示了薄膜中的层状BiO⁺面缺陷有助于稳定畴壁面为(100)型的类180°畴结构，并在这种新型的180°畴壁和LaAlO₃界面相交区域诱导形成了半涡旋和极化涡旋拓扑结构。     

BNT KBT BT薄膜的制备及外场下电畴翻转

采用金属有机物热分解法在Pt/Ti/SiO2/Si基底上制备了085(Bi05Na05)TiO3 010(K05Bi05)TiO3 005BaTiO3(85BNT 10KBT 5BT)薄膜。通过X射线衍射仪、扫描探针显微镜（SEM）、压电力显微镜(PFM)等对薄膜的结构和外场下的电畴演变进行了表征及研究。结果表明,该薄膜微观结构主要由钙钛矿相和少量的焦绿石相组成,表面无明显裂纹和孔洞,其最大压电系数d33=150 pm/V;通过PFM观察到在电场作用下,其电畴可实现180°翻转,在力场作用下其电畴可实现90°翻转,并结合微观结构对电畴在外场下的演变机理进行了研究。该研究为铁电薄膜在MEMS中的应用提供了参考。     

柠檬酸对CeO2磨料分散稳定性及抛光性能的影响

采用柠檬酸作为pH调节剂和分散剂,针对CeO₂磨料水溶液的分散性差以及浅沟槽隔离(STI)化学机械抛光(CMP)过程中正硅酸乙酯(TEOS)/氮化硅(Si₃N₄)的去除速率选择性难以控制的问题进行了研究。分散实验结果表明,由于柠檬酸可以结合在CeO₂颗粒表面从而极大提高了CeO₂磨料的空间位阻,CeO₂溶液的分散稳定性得到提升,因此,与酒石酸、硝酸和磷酸相比,在CeO₂溶液中使用柠檬酸作为pH调节剂,可以使CeO₂磨料具有更小的粒径和较低的分散度以及使CeO₂溶液具有较高绝对值的Zeta电位。抛光实验结果表明,柠檬酸可以极大抑制Si₃N₄的去除速率,且对TEOS的去除速率影响较小,因此,使用柠檬酸作为pH调节剂和分散剂能实现TEOS/Si₃N₄的高去除速率选择比。同时抛光后TEOS和Si₃N₄薄膜具有良好的表面形貌和低的表面粗糙度。     

光学表面粒子污染物散射的单层薄膜调控特性

为了降低超精密低损耗光学元件表面粒子污染物的光散射损耗,文中提出通过在光学表面沉积单层薄膜来调控表面场强分布,从而降低散射损耗的方法。理论分析了K9玻璃超光滑光学表面不同厚度单层二氧化硅（SiO₂）和单层二氧化钛（TiO₂）薄膜表面上方半径为100 nm粒子污染物所在处的电场强度,理论分析结果发现,当SiO₂薄膜厚度为137.4 nm,TiO₂薄膜厚度为12.3 nm时,表面粒子污染物所在处的电场强度最小。在此基础上分别计算了光学元件表面沉积厚度为137.4 nm的单层SiO₂薄膜以及厚度为12.3 nm的单层TiO₂薄膜,表面粒子污染物的总散射损耗(S)和双向反射分布函数(BRDF),计算结果表明,在波长为632.8 nm的光垂直入射时,单层SiO₂薄膜和单层TiO₂薄膜可有效降低其表面粒子的BRDF,且可将K9玻璃表面的总散射分别降低12.40%和25.04%。实验验证了单层SiO₂薄膜对于表面粒子污染物散射降低的有效性。     

高k材料镧前驱体La(tmhd)3和La(tmod)3的热力学及其ALD应用

通过同步热分析研究两种不同的前驱体(La(tmhd)₃和La(tmod)₃)在升华过程中的热稳定性。结果表明,具有不对称分子结构的La(tmod)₃的挥发性大于La(tmhd)₃,其可以作为镧前驱体应用于原子层沉积(ALD)技术。将La(tmod)₃和O₃作为前驱体,通过ALD技术在SiO₂基片上实现了LaO_x薄膜的制备。实验结果表明,其最佳的ALD工艺参数包括：La(tmod)₃和O₃的脉冲时间分别为6 s和2 s, O₃的清洗时间为5 s,沉积温度为250℃。在制备的薄膜中发现了理想的自限性沉积行为。通过X射线光电子能谱仪(XPS)、扫描电子显微镜(SEM)和原子力显微镜(AFM)证实了生长的薄膜具有良好的纯度和表面形貌,其在250℃的沉积温度下具有稳定的生长速率(约0.16?/cycle, 1?=0.1 nm),薄膜的主要成分为La_...     

(Pb,La)TiO3薄膜电畴生长的压电响应力显微镜研究

压电响应力显微镜为铁电薄膜电畴的研究提供了一种有效的检测方法.本实验用压电响应力显微镜(PFM)对不同退火温度的(Pb,La)TiO3铁电薄膜进行表征,得到了各个样品相应的形貌像、面外电畴像和面内电畴像.结果表明,随退火温度升高,(Pb,La)TiO3铁电薄膜的表面形貌表现出从粘连到结晶较好,到出现抱团的变化过程;此外,随退火温度升高,铁电薄膜的自发极化强度先增强后减弱.通过对这一系列铁电薄膜电畴进一步研究得到:在625℃退火1 h后,(Pb,La)TiO3铁电薄膜以非铁电相为主;而在650℃和675℃退火1 h后,(Pb,La)TiO3铁电薄膜以铁电相为主.     

二硫化锡薄膜场效应晶体管的可见光探测特性

采用化学气相输运(CVT)法和微机械剥离技术制备了SnS₂薄膜,使用Au电极作为源、漏电极,n型重掺杂Si作为栅极,制备了基于SnS₂薄膜的背栅型场效应晶体管(FET),并研究了其电学特性和可见光探测特性。结果表明,制备的SnS₂薄膜具有良好的结晶度,SnS₂薄膜背栅型FET具备良好的栅压调控特性。器件对波长为405 nm的蓝紫光表现出明显的光响应,光响应度高达456.82 A·W^-1,外量子效率为1.40×10⁵%,比探测率为7.12×10¹²Jones,并且具有较快的光响应速度,上升和下降响应时间分别为1 ms和0.5 ms。器件的光探测性能受栅压调控,当栅压为40 V时,器件的光响应度可达730 A·W^-1。     

Laser interference figure measurement of 60-Hz high voltages usinga LiNbO3 spherical electro-optic sensor

Measurements of 60 Hz high voltages with a technique based on electric field modulated laser interference figures (produced by passing laser light through a solid sphere of electrooptic crystal) are discussed. The spherical geometry automatically forms a laser interference figure, and results in less electric field distortion than the geometries of previous electrooptic sensors in a uniform electric field. A proof-of-principle experiment was performed using a LiNbO₃ spherical electrooptic sensor     

退火处理对离子束溅射WO3-x薄膜结构和特性的影响

利用离子束溅射结合后退火处理的方法制备了WO_3-x(0≤x≤1)薄膜,系统研究了不同退火气氛、退火温度和退火时间等条件对WO_3-x薄膜的晶体结构以及电学、光学和电致变色特性的影响。研究发现,当退火温度超过WO3结晶温度后,特别是在湿氧气氛下,退火温度越高、退火时间越长,WO_3-x薄膜的结晶度越好,除WO3主晶相显著增强以外,还会陆续出现O29W10、O49W18和WO₂等缺氧相;在干氧条件下,更高的退火温度和更长的退火时间都有助于降低WO_3-x薄膜的电阻值,也都有助于WO_3-x薄膜可见光透过率的提升;WO_3-x薄膜电致变色器件在632.8 nm波长处的光学调制值达到了70%左右,表现出良好的电致变色特性。     

LiNbO3晶体纳秒级光开关的研究

LiNbO3晶体由于其透光范围广，响应速度快，不易潮解等特点而广泛用于高精度和高速光开关快门。为了将LiNbO3光开关曝光时间拓宽到纳秒领域从而弥补现有的高速光开关的不足，文章阐述了LiNbO3作为光开关理论原理，对多波段通光的晶体长宽比进行了优化设计，并对LiNbO3纳秒级光开关的可行性进行了实验验证。实验半波电压与理论符合很好，实验光信号和电信号在纳秒级范围内能实现同步响应。研究结果证实了LiNbO3光开关在纳秒级范围内的可行性，并为LiNbO3纳秒级光开关的制作提供了理论和实验依据。     

反射式掺杂液晶光子晶体光纤电场传感实验研究

提出了一种反射式结构的掺杂向列液晶(NLC)光子晶体光纤(PCF)电场测量传感器。传感器由小于1cm长的掺入液晶实芯PCF构成,在掺杂光纤端面镀Ag膜以提高端面反射率。通过实验,测量出了反射光强随电场强度增加的变化情况,证实了设计的传感器可以用于电场在1.4～3.7kVrms/mm范围内的电场测量,同时获得了镀膜对反射光强的影响以及对传感器灵敏度、精度的影响。     

Switchable Random Laser From Dye-Doped Polymer Dispersed Liquid Crystal Waveguides

A dye-doped polymer-dispersed liquid crystal (PDLC) film has been fabricated for random lasing action. In this PDLC film, the sizes of most liquid crystal (LC) droplets ranged from 200 to 500 nm. When the sample is optically pumped, ultrahigh Q (>10 000) lasing modes and a collimated laser beam can be observed. The threshold of the random laser is shown to be 0.23 mJ/cm². Additionally, a 9.2-V/mum external electric field was applied to control the orientations of LC molecules, thereby obtaining a switchable random laser. Consequently, the linewidth, intensity, and polarization of the emitted random laser are controlled     

Finite element analysis of LiNbO3 waveguides with Si orSi/SiO2 overlay

LiNbO₃ waveguides with Si overlays are emerging as a basic building block for a variety of integrated-optic components, including modulators, high-efficiency gratings, and narrowband WDM filters. However, the development and optimization of these devices are, in large part, hindered by the lack of understanding of the specifics of the Si-on-LiNbO₃ structure which appear to differ dramatically from those of the Si and LiNbO₃ waveguides, considered separately. In this work, we provide a specific insight into the waveguiding properties of vertically stacked Si-on-LiNbO₃ waveguides. In particular, we present a detailed theoretical analysis of the effect of the Si film on the modal characteristics (propagation constant and field distribution) of the structure. The vectorial finite element method (VFEM) is used to numerically investigate a step-index and graded-index single-mode channel waveguide in LiNbO₃, with a Si or Si/SiO₂ multimode overlay. We show that for ~70% of all Si thicknesses, in the range from 0 to 1.6 μm, the highest order normal mode of the entire structure has more than 99.9% of the total energy confined in the LiNbO₃ region, i.e., beneath the Si overlay. This fact is quite intriguing given the fact a planar Si layer of submicron thickness on bulk LiNbO₃ is already multimoded. Furthermore, we show that the effective mode index of the structure is considerably modified compared to that of the LiNbO₃ waveguide while the propagation loss is, on the other hand, practically unaffected (~0.3 dB/cm) even in the presence of the lossy Si film, as confirmed by our previous experimental results. Evidently, large modulation of the effective index and low-loss propagation provide an ideal combination of properties suitable for the fabrication of high-reflectance corrugated waveguide gratings, essential for a number of practical devices, in particular, WDM filters     

A Novel Bonding Method for Ionic Wafers

A novel method for bonding sapphire, quartz, and glass wafers with silicon using the modified surface activated bonding (SAB) method is described. In this method, the mating surfaces were cleaned and simultaneously coated with nano-adhesion Fe layers using a low energy argon ion beam. The optical images show that the entire area of the 4-in wafers of LiNbO₃/Si was bonded. Such images for other samples show particle induced voids across the interface. The average tensile strength for all of the mating pairs was much higher than 10 MPa. Prolonged irradiation reduced polarization in sapphire, quartz, and Al-silicate glasses. Fe and Ar ion-induced charge deposition result in the formation of an electric field, which was responsible for the depolarization. The lattice mismatch induced local strain was found in LiNbO₃/Si. No such strain was observed in the Al-silicate glass/Si interface probably because of annealing at 300 for 8 h. The Al-silicate glass/Si interface showed an interfacial layer of 2 nm thick. A 5-nm-thick amorphous layer was observed with the other layer across the /Si interface. The EELS spectra confirmed the presence of nano-adhesion Fe layers across the interface. These Fe layers associated with the electric field induced by ion beam irradiation for prolonged period of time, particularly in LiNbO₃/Si, might be responsible for the high bonding strength between Si/ionic wafers at low temperatures.     

二维聚合物分散液晶光子晶体的制备与研究

为了改善现有聚合物分散液晶(PDLC)光子晶体(PC)的制备方法和电光特性,利用532nm激光干涉条纹引发聚合物和液晶的混合物相分离,采用全息两次不等时曝光的方法,即第1次曝光完成后,将样品沿基板中心法线旋转60°进行第2次曝光,制备得到电可调谐的二维三角格子的PDLC-PC。实验结果表明,两次曝光的时间对聚合物和液晶的相分离程度影响很大,用偏光显微镜观察优化条件下制备得的二维PDLC-PC发现,聚合物和液晶在二维空间上呈规则的三角格子周期性分布。用波长为633nm的He-Ne激光器探测得到在未施加电压时不同晶格常数的PDLC-PC的衍射图样,并根据一级衍射的电光变化曲线,可以看到,其衍射效率可以利用电场进行有效的调节。     

Electro-optic modulation in germanosilicate fibre with UV-excitedpoling

The authors report what is, to their knowledge, the highest electro-optic effect measured in a germanosilicate fibre ever reported. The electro-optic effect based on a permanent second-order nonlinearity has been induced by UV-excited poling at 193 nm with an electric field >8×10⁵ V/cm. Polarisation dependence of the V_πL product in a birefringent fibre has been observed, and the lowest V_πL product obtained for the TE mode of 32 Vcm, comparable to that based on r₂₂ of LiNbO₃, has been measured at 633 nm with a phase modulation at frequencies up to 5 MHz