掺Ag纳米颗粒的BaTiO3复合薄膜的非线性光学特性

通过准分子激光(XeCl,308 nm,20 ns)在MgO(100)单晶衬底上制备了不同掺杂浓度的Ag:BaTiO3纳米复合薄膜,通过X射线衍射和X射线光电子能谱对薄膜的结构和组分进行了表征.在430 nm和470 nm附近观测到了不同浓度Ag纳米颗粒引起的等离子体吸收峰,通过z扫描技术对复合薄膜的三阶非线性光学特性进行了测量,并对其光学非线性的增强机制进行了讨论.     

脉冲激光沉积Ag:BaTiO3纳米复合薄膜及其光学特性

在MgO(100)基片上利用脉冲激光沉积技术制备了掺有Ag纳米颗粒的BaTiO₃复合薄膜.通过X射线衍射对薄膜的结构进行了表征,利用透射电子显微镜对Ag纳米颗粒的尺寸、形态进行了观测,X射线光电子能谱结果表明Ag呈金属态.在410—500nm范围内观测到了Ag纳米颗粒引起的等离子振荡峰,随着后处理温度和Ag颗粒浓度的增加,吸收峰发生红移,并出现了双峰现象. 关键词： 金属纳米复合薄膜 激光沉积 光吸收     

InP/SiO2纳米复合膜的微观结构和光学性质

应用射频磁控共溅射方法在石英玻璃和抛光硅片上制备了InP/SiO₂复合薄膜,并在几种条件下对这些薄膜进行退火.X射线光电子能谱和卢瑟福背散射实验结果表明,复合薄膜中InP和SiO₂的化学组分都大体上符合化学计量配比.X射线衍射和激光喇曼谱实验结果都证实了复合薄膜中形成了InP纳米晶粒.磷气氛保护下的高温(520℃)退火可以消除复合薄膜中残存的In和In₂O₃并得到了纯InP/SiO₂纳米复合薄膜.实验观察到了室温下纳米复合薄膜的明显的光学吸收边蓝移现象和光学非线性的极大增强 关键词： InP 纳米晶粒 微观结构 光学性质     

脉冲激光沉积Ag:BaTiO3纳米复合薄膜及其光学特性

在MgO(100)基片上利用脉冲激光沉积技术制备了掺有Ag纳米颗粒的BaTiO3复合薄膜.通过X射线衍射对薄膜的结构进行了表征,利用透射电子显微镜对Ag纳米颗粒的尺寸、形态进行了观测,X射线光电子能谱结果表明Ag呈金属态.在410-500 nm范围内观测到了Ag纳米颗粒引起的等离子振荡峰,随着后处理温度和Ag颗粒浓度的增加,吸收峰发生红移,并出现了双峰现象.     

CuO薄膜的三阶非线性光学特性研究

采用脉冲激光沉积技术在Si(100)和熔石英基片上制备了单相的CuO薄膜.通过X射线衍射仪,拉曼光谱仪,场发射扫描电镜和紫外可见光光度计对薄膜的结构,表面形貌和光学性质进行了表征. 场发射扫描电镜结果表明CuO薄膜中晶粒排列致密且分布均匀,其尺寸约为45nm.结合飞秒激光(800nm,50fs)和Z扫描方法测量了薄膜的三阶非线性光学特性,结果表明CuO薄膜具有超快的非线性光学响应且非线性折射率和非线性吸收系数均为负值,其大小分别为-3.96×10^-17 m^{2< 关键词： CuO薄膜 Z-扫描')" href="#">Z-扫描 三阶光学非线性}     

纳米ZnO和ZnO-SiO2复合薄膜的光学性质研究

通过溶胶凝胶(sol-gel)法分别在玻璃衬底上制备了ZnO纳米薄膜和ZnO-SiO₂纳米复合薄膜,并利用紫外-可见光分光光度计对薄膜的光学性能进行了分析.可见光-紫外透射谱显示,随着ZnO溶胶浓度从0.7mol/L降低到0.006mol/L,制备的ZnO薄膜从只出现一个380nm(对应的光学禁带宽度为3.27eV)左右的吸收边到在380和320nm(对应的光学禁带宽度为3.76eV)左右各出现一个吸收边,并且随着ZnO溶胶浓度的降低,在380—320nm波段内的透过率明显提高.而Z 关键词： 纳米ZnO 2复合薄膜')" href="#">ZnO-SiO₂复合薄膜 溶胶凝胶法 透射率     

Ag:Bi2O3复合膜的线性和非线性光学性质

从实验和理论两个方面，探讨了金属Ag不同掺杂浓度对Ag:Bi₂O₃复合膜线性和非线性光学性质的影响. 用吸收光谱研究了Ag浓度与Ag:Bi₂O₃复合膜表面等离子体共振带之间的关系；用皮秒Z-扫描技术研究了共振和非共振情况下(激发光波长分别为532nm和1064nm)，金属Ag浓度与复合膜三阶非线性极化率的关系. 基于表面等离子体共振理论和局域场增强理论对复合膜进行了分析，得到了不同Ag浓度时Ag:Bi₂O₃复合膜的三阶非线性效应，研究了激发波长和金属浓度对复合膜线性和非线性光学性质的影响. 结果表明，等离子体共振增强和合适的金属掺杂浓度使得三阶极化率增强二个量级，在Ag浓度为35％左右和接近等离子体共振频率(相应吸收带位于560nm—622nm)的532nm激发时，χ⁽³⁾具有最大值2.4×10^-9esu. 关键词： 金属纳米颗粒 复合膜 三阶非线性 表面等离子体共振     

Co:BaTiO3/Si(100)纳米复合薄膜制备、微结构及其紫外光电子能谱研究

采用脉冲激光气相沉积(PLD)方法,在Si(100)晶面上制备了Co:BaTiO₃纳米复合薄膜.采用X射线衍射(XRD)结合透射电镜(TEM)方法研究了两种厚度Co:BaTiO₃纳米复合薄膜的晶体结构,当薄膜厚度约为30 nm时,薄膜为单一择优取向;当薄膜厚度约为100nm时,薄膜呈多晶结构.原子力显微镜(AFM)分析表明,当膜厚为30nm时,薄膜呈现明显的方形晶粒.采用紫外光电子能谱(UPS)研究了Co的价态和Co:BaTiO₃纳米复合薄 关键词： 3')" href="#">BaTiO₃ 纳米复合薄膜 紫外光电子能谱     

Co:BaTiO3/Si(100)纳米复合薄膜制备、微结构及其紫外光电子能谱研究

采用脉冲激光气相沉积(PLD)方法,在Si(100)晶面上制备了Co:BaTiO3纳米复合薄膜.采用X射线衍射(XRD)结合透射电镜(TEM)方法研究了两种厚度Co:BaTiO3纳米复合薄膜的晶体结构,当薄膜厚度约为30 nm时,薄膜为单一择优取向;当薄膜厚度约为100 nm时,薄膜呈多晶结构.原子力显微镜(AFM)分析表明,当膜厚为30 nm时,薄膜呈现明显的方形晶粒.采用紫外光电子能谱(UPS)研究了Co的价态和Co:BaTiO3纳米复合薄膜的价带谱.研究表明:当Co浓度很高时其态密度(DOS)与晶体BaTiO3明显不同.此外,嵌埋纳米Co颗粒的BaTiO3薄膜的能带结构可用纳米颗粒的浓度来调制,从而也可对其光学和电学性质进行改性.     

InP/SiO_2纳米复合膜的微观结构和光学性质

应用射频磁控共溅射方法在石英玻璃和抛光硅片上制备了InP SiO2 复合薄膜 ,并在几种条件下对这些薄膜进行退火 .X射线光电子能谱和卢瑟福背散射实验结果表明 ,复合薄膜中InP和SiO2 的化学组分都大体上符合化学计量配比 .X射线衍射和激光喇曼谱实验结果都证实了复合薄膜中形成了InP纳米晶粒 .磷气氛保护下的高温(5 2 0℃ )退火可以消除复合薄膜中残存的In和In2 O3 并得到了纯InP SiO2 纳米复合薄膜 .实验观察到了室温下纳米复合薄膜的明显的光学吸收边蓝移现象和光学非线性的极大增强     

Excimer laser deposited CuO and Cu<Subscript>2</Subscript>O films with third-order optical nonlinearities by femtosecond <Emphasis Type="Italic">z</Emphasis>-scan measurement

By controlling the oxygen pressure, single-phase CuO and Cu₂O thin films have been obtained on quartz substrates using a pulsed laser deposition technique. The structure properties and linear optical absorption of the films were characterized by X-ray diffraction and UV–VIS spectroscopy. By performing z-scan measurements using a femtosecond laser (800 nm, 50 fs), the real and imaginary parts of the third-order nonlinear susceptibility, Re χ ⁽³⁾ and Im χ ⁽³⁾, of the films were determined. Both CuO and Cu₂O films exhibited large optical nonlinearities, which is comparable to those in some representative semiconductor films such as ZnO and GaN films using femtosecond laser excitation. Compared with Cu₂O films, the CuO films showed larger third-order nonlinear optical effects under off-resonance excitation. Furthermore, the mechanisms of the optical nonlinearities in CuO and Cu₂O films are explained in the main text. It was suggested that the reasons of the difference in their nonlinear refractive effects may be related to the different electronic structure in CuO and Cu₂O materials.     

金属纳米团簇复合薄膜Au/BaTiO3与Fe/BaTiO3的PLD制备及其光吸收特征

用脉冲激光沉积技术制备了掺杂纳米金属颗粒Au或Fe的BaTiO₃复合薄膜.用透射电子显微镜和x射线光电子能谱表征了金属颗粒的形态和化学态.330—800nm范围的吸收谱研究表明，掺Au颗粒的BaTiO₃薄膜在580nm附近有一个明显的共振吸收峰，而掺Fe颗粒的BaTiO₃薄膜没有这样的吸收峰.用Mie散射理论对结果进行了分析. 关键词： 复合薄膜 金属颗粒 脉冲激光沉积 吸收谱     

Structure-related infrared optical properties of BaTiO3 thin films grown on Pt/Ti/SiO2/Si substrates

BaTiO₃ thin films with different thickness have been grown on Pt/Ti/SiO₂/Si substrates by a modified sol-gel method. X-ray diffraction analyses show that the BaTiO₃ thin films are polycrystalline. The crystalline quality of the films is improved with increasing thickness. The infrared optical properties of the BaTiO₃ thin films have been investigated using an infrared spectroscopic ellipsometry in the wave number range of 800-4000 cm⁻¹ (2.5-12.5 μm). By fitting the measured pseudodielectric functions with a three-phase model (Air/BaTiO₃/Pt), and a derived classical dispersion relation for the thin films, the optical constants and thicknesses of the thin films have been simultaneously obtained. The refractive index of the BaTiO₃ thin films increases and on the other hand, the extinction coefficient does not change with increasing thickness in the entirely measured wave number range. The dependence of the refractive index on the film thickness has been discussed in detail and was mainly due to both the crystalline quality of the films and packing density. Finally, the absorption coefficient was calculated in the infrared region for applications in the pyroelectric IR detectors.     

Microstructural and optical investigations of Ce-doped barium titanate thin films by FTIR and spectroscopic ellipsometry

(BaTiO₃)_{1? x} (CeO₂) _x (with x?=?0,?1,?3,?5.7 and 16 at.%) thin films were prepared by electron beam evaporation method. According to X-ray diffraction, nanosized and amorphous Ce-doped barium titanate thin films were obtained. The crystallinity diminished as Ce content increased. The increase in the Ce slightly shifts the absorption peaks at 433–450 and 416–424?cm^?1 to higher wavenumbers. A two-layer model was used to describe the experimental ellipsometric data. The Bruggeman effective medium approximation (BEMA) was used to describe the surface roughness layer and the Cauchy dispersion relation was used to describe the main Ce-doped barium titanate layer. The refractive index and the extinction coefficient were found to increase with increasing Ce content; however, the optical band gap decreased with increasing Ce content. The accurate determination of the optical constants of Ce-doped barium titanate thin films may favor them in the applications of optical thin film devices.     

Nonlinear optical properties in SrTiO3 thin films by pulsed laser deposition

Well-crystallized 250 nm-thick SrTiO₃ thin films on fused-quartz substrate were prepared by pulsed laser deposition. The band-gap of SrTiO₃ thin film by transmittance spectra is equal to 3.50 eV, larger than 3.22 eV for the bulk crystal. The nonlinear optical properties of the films were examined with picosecond pulses at 1.064 μm excitation. A large two-photon absorption (TPA) with absorption coefficient of 87.7 cm/GW was obtained, larger than 51.7 cm/GW for BaTiO₃ thin films. The nonlinear refractive index n₂ is equal to 5.7×10⁻¹⁰ esu with a negative sign, larger than 0.267×10⁻¹¹ esu for bulk SrTiO₃. The large TPA is attributed to intermediate energy levels introduced by the grain boundaries, and the optical limiting behaviors stemming from both TPA and negative nonlinear refraction were also discussed.     

The film thickness dependent thermal stability of Al<Subscript>2</Subscript>O<Subscript>3</Subscript>:Ag thin films as high-temperature solar selective absorbers

The monolayer Al₂O₃:Ag thin films were prepared by magnetron sputtering. The microstructure and optical properties of thin film after annealing at 700 °C in air were characterized by transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and spectrophotometer. It revealed that the particle shape, size, and distribution across the film were greatly changed before and after annealing. The surface plasmon resonance absorption and thermal stability of the film were found to be strongly dependent on the film thickness, which was believed to be associated with the evolution process of particle diffusion, agglomeration, and evaporation during annealing at high temperature. When the film thickness was smaller than 90 nm, the film SPR absorption can be attenuated until extinct with increasing annealing time due to the evaporation of Ag particles. While the film thickness was larger than 120 nm, the absorption can keep constant even after annealing for 64 h due to the agglomeration of Ag particles. On the base of film thickness results, the multilayer Al₂O₃:Ag solar selective thin films were prepared and the thermal stability test illustrated that the solar selectivity of multilayer films with absorbing layer thickness larger than 120 nm did not degrade after annealing at 500 °C for 70 h in air. It can be concluded that film thickness is an important factor to control the thermal stability of Al₂O₃:Ag thin films as high-temperature solar selective absorbers.     

Nonlinear optical absorption in Bi3TiNbO9 thin films using Z-scan?technique

Bi₃TiNbO₉ (BTN) thin films with layered perovskite structure were fabricated on fused silica by pulsed laser deposition. The XRD pattern revealed that the films are single-phase perovskite and highly (00l) textured. Their fundamental optical constants, such as band gap, linear refractive index, and linear absorption coefficient, were obtained by optical transmittance measurements. The dispersion relation of the refractive index vs. wavelength follows the single electronic oscillator model. The nonlinear optical absorption of the films was investigated by single beam Z-scan method at a wavelength of 800 nm with laser duration of 80 fs. We obtained the nonlinear absorption coefficient β=1.44×10⁻⁷ m/W. The results show that the BTN thin films are promising for applications in absorbing-type optical devices.