Phase-matched second-harmonic generation at 440 nm in a LiNbO3 -Gd3Ga5O12 waveguide with a tunable stimulated Raman source

Using a tunable stimulated Raman source, we have observed second-harmonic generation in the blue in a sputtered LiNbO₃ film deposited on Gd₃Ga₅O₁₂. With the choice of Gd₃Ga₅O₁₂ as a substrate, it becomes possible to both phase-match a large range of fundamental wavelengths as well as have an excellent epitaxial quality surface. The SHG efficiency for the TM^ω₀ → TM^2ω₂ phase matched conversion process is estimated to be ～ 10^-4.     

Thermal annealing effect on the crystallization and optical dispersion of sprayed V2O5 thin films

Polycrystalline vanadium pentoxide (V₂O₅) thin films have been deposited by spray pyrolysis technique on preheated glass substrate. The influence of thermal annealing on the crystallization of V₂O₅ has been investigated. X-ray diffraction analysis (XRD) revealed that the films deposited at T_sub=350 °C were orthorhombic structures with a preferential orientation along 〈0 0 1〉 direction. Moreover, the degree of crystallinity was improved by thermal annealing. Optical properties of these samples were studied by spectrophotometer in the wavelength range 300-2500 nm. Some of the important optical absorptions such as optical dispersion energies E_o and E_d, dielectric constant ε, ratio between number of charge carriers and effective mass N/m^*, wavelength of single oscillator λ₀, plasma frequency ω_p, single resonant frequency ω₀ and the average of oscillator strength S_o, have been evaluated. In the annealing process, the dielectric properties have weak dependencies of film thickness and annealing time. Furthermore, a value of carrier concentration was obtained of 3.02×10²⁵ m⁻³ for the as-deposited film and slight changes with annealing time.     

不同波长激光激发下C6H12受激拉曼散射模式竞争

发现不同波长激光激发下C₆H₁₂的受激拉曼散射模式竞争现象. 在不同波长的激光激发下，不同拉曼模式的Stokes光占优势. 短波长(404，532nm)激光激发时小频移模式ω₁(802cm^-1)为弱增益模式，大频移模式ω₂(2852—3038cm^-1)为强增益模， 主要产生ω₂模式的Stokes光. 长波长(80 关键词： 模式竞争 6H₁₂')" href="#">C₆H₁₂ 受激拉曼散射     

3ω法加热/测温膜中温度波解析及其在微/纳米薄膜导热系数测量中的应用

给出了3ω法测试系统中描述薄膜表面加热/测温膜中温度波动的级数形式解，并将复数温度波动的实部和虚部分开表示.利用该解分析了交流加热频率、加热膜宽度和材料热物性的组合参数对加热膜温度波动幅度的影响.并根据此解对测量原理的数学模型进行了修正，建立了相应的3ω测试系统，首先测定了厚度为500 nm SiO₂薄膜的导热系数，验证了实验系统的合理性.加大了测试频率，利用级数模型在高频段直接得到SiO₂薄膜的导热系数，结合低频段的数据同时确定了Si基体的导热系数.利用级数解分析测试了激光晶体Nd:YAG〈111〉面上多层ZrO₂/SiO₂增透膜的导热系数，测试的ZrO₂薄膜的导热系数比体材料小.进行了不确定度分析.结果表明，提出的分析方法可以有效研究微器件表面薄膜结构的导热性能. 关键词： ω法')" href="#">3ω法 微/纳米薄膜 导热系数 微尺度加热膜     

ECR-PECVD制备Si3N4薄膜的光学特性研究

本文研究了ECR-PECVD制备的Si₃N₄薄膜的光学特性.得到的Si₃N₄薄膜具有光致发光效应,在280℃沉积制备的Si₃N₄薄膜的光致发光波长为400nm,具有较好的单色性.测试分析了Si₃N₄薄膜对可见光、红外光具有较高的透射性能,Si₃N₄薄膜可作为红外光的增速减反射膜.     

χ polarization induced in molecular glass of conjugated compound by all-optical poling

The paper presents the first report on χ⁽²⁾ polarization induced in molecular glass of conjugated compound by all-optical poling. Transparent thin film of molecular glass of 1,4-bis[2-[4-[N,N-di(p-tolyl)amino]phenyl]vinyl]benzene (BTAPVB) was prepared using a spin-cast technique. Dipolar as well as octupolar components in BTAPVB contributed to the formation of photoinduced χ⁽²⁾ polarization. Growth rate of χ⁽²⁾ polarization has good linear relation with E_ω⁴E_2ω, which suggested that the simultaneous processes of two-photon (ω + 2ω) and three-photon (ω + ω + ω) excitation on the same electronic level contributed to the formation of photoinduced χ⁽²⁾ polarization.     

Preparation and electrical conductivity of LISICON thin films

LISICON thin films have been prepared with RF sputtering and subsequent heat-treatment. The crystal phases of sputtered films depend on the sputtering conditions, especially the target composition and ambient gas atmosphere. Though the as-sputtered films in Ar-O₂ mixed gas (target composition: Li₃Zn_0.5GeO₄+0.5 ZnO, gas pressure: 9×10^-2 Torr, oxygen gas content: 74.6%) were amorphous; LISICON single phase thin films were obtained after annealing at 600°C for 6 h. The conductivity of the film at 500°C is 5×10^-3ω^-1cm^-1 which is slightly lower than that for ceramic Li₃Zn_0.5GeO₄.     

MnBiAl薄膜的磁光及磁性能研究

用真空电子束蒸发制备了MnBi_xAl_0.15薄膜.当0.4≤x≤0.7时,MnBi_xAl_0.15薄膜的Kerr角与MnBi_x薄膜相比有显著增大;而当x＞0.7时,MnBi_xAl_0.15的Kerr角则比MnBi_x的要不,633nm波长测量时,MnBi_{0.5Al0.15的Kerr角为2.75°,而相对应的MnBi0.5薄膜只有1.56°.MnBi05Al0.15薄膜的室温饱和磁化强度Ms为3×10⁵A/m,比MnBi0.5薄膜的Ms(4×10⁵A/m)要小.推测当0.4≤x≤0.7时,Al可能部分占据Bi空位和部分取代Mn位,由于晶格收缩使得Mn 3d电子与Bi 6p电子的杂化概率增大,从而导致其Kerr效应增强. 关键词：}     

Low-temperature performance of thin solid electrolyte cell based on MoO3-doped Bi2O3

Improvement of low-temperature performance of oxygen sensor was studied by preparing a thin film of 15 μm thickness. Melt-quenched Bi₂O₃ film doped with 16 mol% MoO₃ was used as an electrolyte after HF treatment. Impedance measurements were carried out in the frequency range DC-100 KHz. Resistance of electrolyte in the form of thin film (110ω) was negligibly small compared with the overall resistance of the cell (287 Kω) at 350°C. Oxygen/air concentration cell was constructed and the cell performance was measured at 350 and 300°C. Transference number close to unity and rapid response were observed at 350°C, however the cell showed a long response time of about 3 min at 300°C.     

Characterization of SnO2/Pb2CrO5 thin film/metal photovoltaic device

The photovoltaic behavior in a design of SnO₂/Pb₂CrO₅ thin film/metal (Au or Al) is described as functions of light intensity and wavelength for two different illumination directions. The Pb₂CrO₅ thin film in each device is formed over the SnO₂ coated glass substrate by an electron-beam evaporation technique. When illuminated from the metal side, the device with Au or Al shows the positive or the negative photovoltage, respectively. For the illumination from the SnO₂ side, the device with Au has the negative photovoltage at the short wavelength, and the positive one at the longer, while the device with Al has the negative photovoltage at both wavelength regions. These photovoltaic devices have two junctions at both sides of the Pb₂CrO₅ thin film. The band model of each device is also discussed.     

Red electroluminescent process excited by hot holes in SrGa2S4:Ce, Mn thin film

This paper reports the first observation of red electroluminescence (EL) in SrGa₂S₄:Ce, Mn thin film. The EL spectrum consists of single broad emission band having a peak wavelength of 665 nm. The dominant EL decay time was 31 μs. The relationship between the applied voltage and the EL waveform was measured in single insulating thin film electroluminescent (TFEL) devices. An asymmetric EL waveform was observed in SrGa₂S₄:Ce, Mn TFEL devices under a rectangular applied voltage. The polarity of the EL waveform in these devices was different from the waveform in manganese-activated zinc sulfide ZnS:Mn devices. This indicates that hot holes excite the Mn²⁺ ions to cause the red EL.     

Influence of mobile space charges on electrical properties of ferroelectric Bi3.5La0.5Ti3O12 thin films

Lanthanum-substituted bismuth titanate, Bi_3.5La_0.5Ti₃O₁₂ (i.e., x=0.5 in Bi_4−xLa_xTi₃O₁₂), thin films have been grown on Pt/Ti/SiO₂/Si substrates using pulsed laser deposition. The frequency dependence of the real part ε′(ω) and the imaginary part ε″(ω) of the dielectric constant has been studied. The ε′(ω) does not show any sudden change within the frequency range of 10²-10⁶ Hz. In contrast, the ε″(ω) shows a large dispersion as frequency decreases. The observed relaxation behavior in ε″(ω) can be explained in terms of a migration of oxygen vacancies in (Bi₂O₂)²⁺ layers, not in Bi₂Ti₃O₁₀ perovskite layers.     

Electrical properties of ZrO2-CeO2 at intermediate temperatures

Both ZrO₂-CeO₂ powder materials and thin film ceramic membranes have been prepared by sol-gel processes. Sol and suspensoid were used as dips for preparing the thin film membranes in this work. The membranes, with a thickness in the range of 200 nm to a few mm, were coated on porous alumina ceramic substrates by a slip-coating or spin-coating process for different purposes. The ZrO₂-CeO₂ thin film membranes are highly conductive and transparent with an ionic conductivity as high as 10⁻² S/cm at 600 °C, which is two orders of magnitude higher than that of the bulk materials. This is perhaps caused by a different microstructure for the thin film membranes compared to the bulk materials. The thin films, but not the bulk samples, are stable in reduced atmosphere. By controlling the composition and atmosphere, the ZrO₂-CeO₂ materials can be ionic, electronic or mixed conductors. For the bulk samples a transition has been observed where the conductivity increases by about two orders of magnitude. Paper presented at the 4th Euroconference on Solid State Ionics, Renvyle, Galway, Ireland, Sept. 13–19, 1997     

Investigation on optical properties of Bi<Subscript>2.85</Subscript>La<Subscript>0.15</Subscript>TiNbO<Subscript>9</Subscript> thin films by prism coupling technique

Layered-perovskite ferroelectric Bi_2.85La_0.15TiNbO₉ (LBTN) optical waveguiding thin films were grown on fused silica substrates by pulsed laser deposition (PLD). X-ray diffraction (XRD) revealed that the film is highly (00l) textured. We observed sharp and distinct transverse electric (TE) and transverse magnetic (TM) multimodes and measured the refractive indices of LBTN thin films at 632.8 nm. The ordinary and extraordinary refractive indices were calculated to be n _TE=2.358 and n _TM=2.464, respectively. The film homogeneity and the film-substrate interface were analyzed using an improved version of the inverse Wentzel–Kramer–Brillouin (iWKB) method. The refractive index of the film remains constant at n ₀ within the waveguiding layer. The average transmittance of the film is 70% in the wavelength range of 400–1400 nm and the optical waveguiding properties were evaluated by the optical prism coupling method. Our results showed that the LBTN films are very good electro-optical active material.     

Study of preparation of Au-LiF-Au and Al-LiF-Au systems by vacuum evaporation

The structure of thin LiF film has been investigated with regard to its continuity in Au-LiF-Au, Al-LiF-Au systems. The samples have been evaporated on unheated glass substrates at 5×10^?5 torr without breaking vacuum. The number of short-circuited samples was evaluated in dependence on the angle of evaporation and thickness of the LiF film. It appears that the angle of evaporation of the value about ofω=20° already increases the number of short circuits in the case of Au-LiF-Au, meanwhile in the case of Al-LiF-Au it has no influence. Explanation is given by means of shadow effects which take place in thin LiF film in the system Au-LiF-Au. Replicas of LiF on Au and LiF on Al show in the first case that the layer consists of larger crystals and is less homogeneous. Difference between systems mentioned above can be seen also from the dependence of the number of short-circuited samples on the thickness of thin LiF film at the angle of evaporationω=0°. It is possible to draw boundary thicknesses of thin LiF film for obtaining non-short-circuited samples. In the case of Al-LiF-Au it is about 250 Å and in the case of Au-LiF-Au about 500 Å.     

Cathode luminescence characteristics of ZnGa2O4 phosphor thin films with the doped activator

The zincgallate (ZnGa₂O₄) phosphor thin film was grown using RF magnetron sputtering system at various process parameters. A ZnGa₂O₄ phosphor thin film was deposited on Si(1 0 0) substrate and annealed by a rapid thermal processor (RTP). The X-ray diffractometer (XRD) patterns indicate that the Mn-doped ZnGa₂O₄ phosphor thin film shows a (3 1 1) main peak and a spinel phase. A ZnGa₂O₄ phosphor thin film has better crystallization due to increased substrate, annealing temperature and deposition time. Also the ZnGa₂O₄:Mn phosphor thin film shows green emission (510 nm, ⁴T₁→⁶A₁), and the ZnGa₂O₄:Cr phosphor thin film shows red emission (705 nm, ⁴A₂→⁴T₂).     

Study of complex refractive indices of gold and copper using emissivity measurements

We show from emissivity measurement that it is possible to determine the complex refractive index for smooth and opaque materials.⁽¹⁾ Moreover, for noble metals, Drudes's completed model can be used;⁽²⁾ thanks to the variations of the complex index as a function of the wavelength the; values of the plasma and relaxation frequency for conduction electrons (ω_p and ω_τ) respectively can be determined; First, we have shown how emissivity measurements can lead to values of (ω_p and ω_τ) (this study has been carried out on copper). Then we have computed deduced and determined a general dispersion formula as a function of temperature and frequency for, using gold for the experiments because of its chemical stability. Variation of zero frequency relaxation frequency with temperature due to interaction between conduction electrons and phonons matches Debye's model well,⁽³⁾ as has been verified. Relaxation frequency increases with the square of the radiation frequency, this behaviour due to interactions between conduction electrons had been described by Gurzhi,⁽⁴⁾ and verified. With the chosen model we are able to describe macroscopic properties of the emission radiation in the given range of temperature and wavelength with minimum requirement of parameters.⁽⁵⁾     

The nonlinear optical property and photoinduced anisotropy of?a?novel azobenzene-containing fluorinated polyimide

A novel azobenzene-containing fluorinated polyimide was synthesized. The nonlinear optical property and photoinduced birefringence of a polyimide thin film were investigated. Large third-order nonlinear refraction (n ₂=−4.49×10⁻¹¹ cm²/W) was observed in the polyimide thin film by carrying out Z-scan measurement. The polyimide thin film exhibited larger nonlinear refraction than that of a mono-azo dye doped PMMA thin film (n ₂=−1.63×10⁻¹² cm²/W). The photoinduced birefringence of the polyimide thin film (▵ n∼10⁻²) under different pump intensities was investigated; it was much larger than that of the mono-azo dye doped PMMA thin film (▵ n∼10⁻³). Moreover, the time constants for birefringence growth and relaxation processes were determined.     

Improved resistive switching performance in Cu-cation migrated MoS2 based ReRAM device incorporated with tungsten nitride bottom electrode

The resistive switching characteristics of sputtered deposited molybdenum disulphide (MoS₂) thin film has been investigated in Cu/MoS₂/W₂N stack configuration for Resistive Random Access Memory (ReRAM) application. The benefits of incorporating tungsten nitride (W₂N) as a bottom electrode material were demonstrate by stability in operating voltages, good endurance (10³ cycles) and long non-volatile retention (10³?s) characteristics. Resistive switching properties in Cu/MoS₂/W₂N structure are induced by the formation/disruption of Cu conducting filaments in MoS₂ thin film. Ohmic law and space charge limited current (SCLC) are observed as dominant conduction mechanism in low resistance state (LRS) and high resistance state (HRS) respectively. This study suggests the application of MoS₂ thin films with W₂N bottom electrode for next generation non-volatile ReRAM application.     

Irradiation of solid C60 films with pulsed UV-laser-light: Fabrication of a periodic submicron C60 structure and transformation of C60 into a different carbon phase

A thin solid C₆₀ film has been irradiated under a fix incident angle with pulsed UV light at the wavelength of 266 nm. With scanning electron microscopy and atomic force microscopy, a surface transformation of the irradiated films has been observed to a periodic surface structure at low laser fluences in air as well as in vacuum and to strong morphology changes at higher laser fluences only in air. For both structural transformations the occuring surface chemistry has been studied with Raman spectroscopy and X-ray photoelectron spectroscopy. In the case of the periodical lines, these results in addition to a detailed discussion of the existing models for laser induced surface structures have shown that the C₆₀ film remains a van der Waals solid but with much oxygen incorporation in the lattice and does not polymerize as it is known to happen during continuous wave irradiation. The case of strong morphology changes could be explained by detailed comparison of the obtained Raman and X-ray photoelectron spectroscopy data as the formation of a new carbon phase with diamond-like sp³ bondings through an oxygen-assisted fullerene cage opening.