用于燃料电池的氧化锆薄膜制备方法进展

固体氧化物燃料电池(SOFC)具有高效率、低污染等优点,氧化钇稳定氧化锆(YSZ)是目前用于SOFC的最成功的电解质材料,为了减小高温运行带来的困难,应用中需将YSZ制成薄膜。综述了制备YSZ 薄膜的各种方法,其中包括化学气相沉积(CVD)、电化学气相沉积(EVD)、溶胶-凝胶法(Sol-gel)和喷雾热解法等化学方法;物理气相沉积技术(PVD)和喷涂技术等物理方法;以及电泳沉积法(EPD)、注浆成型法和离心浇铸法等陶瓷成型方法,介绍了近年来采用上述方法制备的YSZ膜的性能及其用于SOFC电池研究取得的实验结果,最后评述了这些方法各自的特点。     

Low temperature metal-organic chemical vapor deposition of Ru thin films as electrode for high dielectric capacitors

Abstract

Low temperature metal-organic chemical vapor deposition (MOCVD) process of Ru films for use as electrode material was studied using a noble dome type reactor, liquid delivery technique and a new precursor. The films were grown at temperatures ranging from 275°C to 480°C in which film growth was controlled by a surface chemical reaction with a small activation energy of 0.21 eV. The root-mean-squared surface roughness was as low as 23 Å for a film grown at 290°C on a SiO₂ surface.     

Submilliampere threshold current InGaAs-GaAs-AlGaAs lasers andlaser arrays grown on nonplanar substrates

High performance buried heterostructure InGaAs-GaAs-AlGaAs quantum-well lasers and laser arrays with tight spatial confinement of the electrical current and the optical fields have been fabricated by metalorganic chemical vapor deposition. The lasers ace fabricated in a single growth step, using nonplanar substrates as a template for the active region definition. CW room temperature threshold currents, as low as 0.5 mA and 0.6 mA, are obtained for as-cleaved double and single quantum-well lasers, respectively. External quantum efficiencies exceeding 80% are obtained in the same devices. High-reflectivity facet-coated lasers have room temperature CW threshold currents as low as 0.145 mA with 10% external quantum efficiency. Lasers made by this technique have high yield and uniformity, and are suitable for low threshold array applications     

生长温度对ZnO纳米结构形貌的影响

研究了用气相输运方法制备ZnO纳米结构时,生长温度对ZnO纳米形貌的影响。当生长温度在400℃时,获得的是ZnO纳米锥,它们紧密结合在一起,形成了纳米锥薄膜;当生长温度升至450℃时,获得的是在ZnO纳米片上生长着杂乱无章的纳米线的双层结构;当生长温度升至480℃时,获得的是单一没有规则的ZnO纳米线;当生长温度升至560℃时,获得的是ZnO纳米片。试验结果表明:温度决定了ZnO纳米形貌特征。     

PATTERNED HIGH FREQUENCY THICK FILM MEMS TRANSDUCER

ABSTRACT

Ferroelectric properties of BiFeO₃ (BFO) thin films epitaxially grown on SrRuO₃ (SRO)/(001)SrTiO₃ (STO) structure were investigated. First, bottom SRO electrodes were deposited on STO substrates by metalorganic chemical vapor deposition (MOCVD) or by sputtering. Then, BFO thin films were deposited on SRO/STO structures by chemical solution deposition. X-ray diffraction analysis showed that the SRO films deposited by both methods grew epitaxially on STO substrates as a single phase perovskite structure, but the out-of-plane lattice parameters of SRO were different, that is, they were 0.396 nm in MOCVD and 0.399 nm in sputtering. The leakage current densities were higher than 1 A/cm² at room temperature in BFO films on both MOCVD-and sputtered-SRO, but the current density in the film on sputtered SRO decreased to 2 × 10^?4 A/cm² at 80 K. The remanent polarization of approximately 50 μC/cm² was observed at 80 K in the BFO thin film on sputtered-SRO/STO.     

Metal-organic chemical vapor deposition enabling all-solid-state Li-ion microbatteries: A short review

For powering small-sized electronic devices, all-solid-state Li-ion batteries are the most promising candidates due to its safety and allowing miniaturization. Thin film deposition methods can be used for building new all-solid-state architectures. Well-known deposition methods are sputter deposition, pulsed laser deposition, sol-gel deposition, atomic layer deposition, etc. This review summarizes thin film storage materials deposited by metal-organic chemical vapor deposition (MOCVD) for all-solid-state Li-ion batteries. The deposition parameters strongly influence the quality of the films, such as surface morphology, composition, electrochemical stability and cycling performance. Some materials have been successfully deposited by MOCVD into 3D–structured substrates, revealing conformal, homogeneous and high performance battery properties.     

离子参数对物理气相沉积薄膜微结构的影响

在追述以往的判断薄膜微结构的结构区模型的基础上，整理和介绍了国外最近提出的结构区模型。它是以离子复合参数Ｅｐ（由到达的离子带给凝聚粒子的平均能量ｅＶ／ａｔｏｍ）为参变量，衡量该参数对薄膜微结构及其特性的影响，对今后设计ＰＶＤ设备和更好地掌握工艺条件，将会是有益的。     

Effect of a thin ionized-metal-plasma deposited Cu layer on theproperties and thermal stability of Cu-TaN-SiO2-Si structures

Cu-TaN-SiO₂-Si structures, fabricated in a three-in-one system, were systematically investigated using various techniques. By depositing a thin plasma-metal-plasma (IMP) Cu layer on the TaN barrier prior to the copper film deposited using metal-organic chemical vapor deposition, the sheet resistance, uniformity, and adhesion of the metal in the Cu-TaN-SiO₂-Si structures can be significantly improved. The thermal stability of the structures can also be enhanced due to the reduction of Cu diffusion and out-diffusion of Si, Ta, and O elements. These observations are of great value for application of chemical vapor deposition Cu-IMP Cu in multilevel interconnects of deep-submicron integrated circuits     

PECVD低功率沉积氮化硅薄膜研究

为了减少太阳能电池氮化硅薄膜生产工艺中的缺陷、提高太阳能电池的转换效率,采用等离子增强化学气相沉积法在射频功率较低的条件下,对N型单晶硅片表面进行氮化硅沉积,获得与高射频功率沉积时相同膜厚和折射率的氮化硅膜,通过试验分析了低功率沉积工艺对电池电参数、对膜厚均匀性的影响。结果表明,在低功率沉积工艺条件下,有助于改善膜厚均匀性,使膜厚不均匀度由12%下降到6%,太阳能电池转换效率提高了0.05个百分点。     

Leakage Current Measurements of STO and BST Thin Films Interpreted by the "Dead" Layer Model

Electrical properties of Strontium-Titanate (STO) and Barium-Strontium-Titanate (BST) thin films capacitors were investigated. The STO films were fabricated by chemical solution deposition (CSD) with thickness between 50 and 150 nm, while the BST films were deposited by metal organic chemical vapor deposition (MOCVD) with thickness between 20 and 110 nm. All films were grown on platinized and oxidized silicon wafers. As top electrodes platinum (Pt) was deposited on top of the ceramic film by sputtering. The electrode size varied between 8*10 m 3 to 1 mm 2 . The leakage current measurements were performed at different temperatures ranging from 15 to 200C and the applied voltage varied between 0 and - 4 V. Capacitance was measured at RT up to - 3 V bias at 1 kHz and 50 mV oscillation voltage. The main results are: The effective barrier heights extracted from the temperature dependence of leakage current are about 1.35 eV for STO and 0.94 eV for BST for the temperature region >100C. The field dependencies of the leakage current show almost perfect linear behavior in a "Schottky" plot for BST while STO reveals 2 separated Schottky regions. The permittivity extracted from the field dependence using the simple thermionic emission model with Schottky lowering results in rather improbable values of the effective Richardson constant A * and unphysical values of the relative optical permittivity, l r, opt <1. The use of a modified model with low permittivity interface layers ("dead layers"), as suggested by the thickness dependence of the inverse capacitance, solved these difficulties. The parameters extracted from fits of this model are discussed.     

Poly (3,4-ethylenedioxythiophene) for chronic neural stimulation.

Chronic neural stimulation using microelectrode arrays requires highly stable and biocompatible electrode materials with high charge injection capability. Conductive polymer poly(3,4-ethylenedioxythiophene) (PEDOT) was electrochemically deposited on thin film Pt electrodes of stimulation electrode arrays to evaluate its properties for chronic stimulation. The coated electrodes demonstrated much lower impedance than thin film Pt due to the high surface area and high ion conductivity across the film. The PEDOT film also presents intrinsic redox activity which contributes to the low impedance as well as a much higher charge storage capacity. The charge injection limit of PEDOT electrode was found to be 2.3 mC/cm2, comparable to IrOx and much higher than thin film Pt. Under biphasic stimulation, the coated electrodes exhibited lower voltage and linear voltage excursion. Well-coated PEDOT electrodes were stable under chronic stimulation conditions, suggesting that PEDOT is a promising electrode material to be further developed for chronic neural stimulation applications.     

Electrodes for ferroelectric thin films

Abstract

Platinum and ruthenium oxide (RuO₂) deposited by ion beam sputter-deposition are evaluated for use as electrodes for PZT thin film capacitors. The effect of deposition temperature, film thickness, and the presence of oxygen on hillock formation in platinum is discussed. It is shown that the hillock density in Pt/Ti/SiO₂/Si films can be significantly reduced by properly controlling the processing conditions and film thickness. Stress measurements correlate with the experimental observation that depositing thinner platinum films (<800 Å) is an effective means of reducing hillock formation. The use of an intermediate deposition temperature 200–250°C also helps minimize hillock formation. Diffusion of the Ti adhesion layer into and/or through the platinum was significantly reduced by replacing the Ti with a TiO_x adhesion layer. RuO₂ electrodes are compared to Pt in terms of resistivity, surface morphology, microstructure and film orientation.     

Characterization of MOCVD Pt electrode for ferroelectric thin films

Abstract

Platinum thin films were deposited by low pressure chemical vapor deposition (LPMOCVD) on SiO₂/Si and (Ba, Sr)TiO₃/Pt/SiO₂/Si substrates using Pt-hexafluoroacetylacetonate at various deposition temperatures. The shiny mirror-like Pt thin films of a high electrical conductivity were obtained, when the deposition temperature is between 325°C and 350°C, whereas above 375°C Pt thin films showed rough surface as well as poor adhesion property to oxide substrate. Pt thin films had a good step coverage of 90%. The results indicate that LPMOCVD Pt thin films can be applied for the top electrode of high dielectric thin film, which is thought to be one of the best candidate materials for a capacitor of ULSI DRAM.     

Phase Development and Electrical Properties of Pb(Yb 1/2 Nb 1/2 )O 3 -PbTiO 3 Epitaxial Films

The growth and electrical properties of Pb(Yb 1/2 Nb 1/2 )O 3 -PbTiO 3 (PYbN-PT) epitaxial films were investigated. PYbN-PT epitaxial films with SrRuO 3 bottom electrodes were grown by pulsed laser deposition. Optimization of the growth conditions for the PYbN-PT epitaxial films was carried out on (100) SrRuO 3 /(100) LaAlO 3 substrates using the (50/50) composition target. It was found that formation of pyrochlore phase could be caused not only by low growth temperatures or lead deficiency, but also by poor surface condition of the SrRuO 3 bottom electrodes. (001) PYbN-PT epitaxial films with good crystalline quality were obtained for a range of deposition rates (60-100 nm/min) and temperatures (620-680 °C) after vacuum annealing the SrRuO 3 bottom electrodes. The ferroelectric and piezoelectric properties of 1 w m-thick PYbN-PT epitaxial films with (50/50) and (60/40) compositions and with (001) and (111) orientations were investigated using (100) LaAlO 3 , (100) SrTiO 3 , and (111) SrTiO 3 substrates with SrRuO 3 bottom electrodes. The highest remanent polarization (29 w C/cm 2 ) and effective piezoelectric coefficient e 31.f ( m 14 C/m 2 ) were observed in the (001) PYbN-PT (50/50) film. The transition temperature of the (001) PYbN-PT (50/50) film was about 380 °C. Because of the degradation of the target during the deposition, a 3 w m-thick film was prepared by three depositions (1 w m each layer). The 3 w m-thick film exhibited a higher e 31.f coefficient of m 19 C/m 2.     

薄膜二次锂离子电池正极研究进展

薄膜二次锂离子电池是锂离子电池发展的最新领域,正极材料的薄膜化是薄膜二次锂离子电池的重要部分.综述了近年来发展的一些薄膜正极的制备方法,包括溶胶-凝肢法(Sol-gel)、化学沉积法(CVD)、激光高温灼烧法(LA)、脉冲激光沉积法(PLD)、射频磁控溅射法(RMP),对各种方法的优缺点进行了比较,并对正极薄膜制备的发展方向进行了展望.     

Mocvd process model for deposition of complex oxide ferroelectric thin films

Abstract

Thin complex oxide films, such as ferroelectrics, pyroelectrics, waveguides, superconductors, MEMS/MOEMS and piezoelectrics are experiencing rapid growth in a wide variety of commercial markets. In particular, ferroelectrics as used in IC cards, embedded memories with micro-controllers, stand-alone memories, and other ASIC applications, require deposition by a technique that is compatible with deep sub-micron advanced geometry IC integration. Metal Organic Chemical Vapor Deposition (MOCVD) is the deposition method of choice for achieving conformal uniform (composition and thickness) contiguous pin hole free thin films over the challenging sub 0.2 micron geometry topology necessary for implementing advanced devices. MOCVD is free of the physical limitations that produce film defects associated with other liquid source and physical vapor deposition techniques. Of the different MOCVD approaches to complex oxide film deposition, we have found rotating disk reactor (RDR) MOCVD to be the most versatile and capable of producing uniform films efficiently. Using computational fluid dynamic methods, a process model for optimizing the multiple process parameters of RDR-MOCVD, single and multiple wafer production tools, has been developed. The models developed are compatible with plasma-assist, single or multiple precursor and graded composition deposition of films. The developed hardware and model have been combined to maximize thin oxide film properties. SMI modeled RDR MOCVD methodology and film results are presented.     

Optical modulators. The quantum well intersubband kind

Perfecting thin film growth techniques have made possible today's search for new, ultrafast optoelectronic devices. The techniques include: molecular beam epitaxy (MBE), organometallic chemical vapor deposition (OMCVD) and atomic layer epitaxy (ALE). By using these methods, scientists and engineers can grow multilayered semiconductor structures of different materials, with extremely high purity, sharp interfaces, and narrow doping profiles. The thickness of each layer has as its lower limit only one atomic layer. By superposing successive materials of different bandgaps, we can create quantum well structures in which electrons or holes are confined to potential wells in the conduction or valence bands. This quantization has allowed for the observation of quantum effects impossible to observe in the bulk materials. One effect is the electron or hole subband-to-subband transition within a conduction or a valence band in a quantum well. This is best known as the inter-subband transition. Before to this concept is examined, the author reviews the optical modulator, its pros and cons, and how quantum wells are used to realize a modulator     

Platinum,Ruthenium and Ruthenium Dioxide Electrodes Deposited by Metal Organic Chemical Vapor Deposition for Oxide Applications

Platinum (Pt), ruthenium (Ru), and ruthenium dioxide (RuO 2 ) have been considered as possible candidates as electrodes for high permittivity and ferroelectric oxides. The films were grown by metal organic chemical vapor deposition (MOCVD). High purity Pt films with near bulk resistivities (11 w z cm) were deposited. The Pt, Ru and RuO 2 films were found to be continuous and smooth and exhibited excellent adhesion properties on the underlying substrates. The temperature dependent electrical conductivity of the Ru and RuO 2 films was metallic type. Room temperature resistivities as low as 18 and 30 w z cm were determined for Ru and RuO 2 , respectively.     

Time-of-Flight pulsed ion beam surface analysis as a means of in situ,real-time characterization of the growth of ferro-electric and conductive oxide heterostructures

Abstract

Pulsed beam Time-of-Flight Ion Scattering and Recoil Spectroscopy (TOF-ISARS) surface analysis methods have been developed which permit real-time, in situ characterization of the growth layer of multi-component oxide thin films. Results are presented from a study of the deposition of Pb, Zr, Ti and Ru using a sequential layer-by-layer deposition method under ambient oxygen pressure conditions appropriate to the growth of PZT films, revealing layer-by-layer as well as 2D and 3D island growth processes during deposition. Thermodynamic stability conditions result in modification of the layered structure during deposition, in some cases altering the layer ordering of the growth region. Calculations using the Miedema model for surface segregation are in accord with experimental results that reveal an exchange between deposited Zr and Ti atoms and an underlying Pb layer. In addition, the room temperature studies revealed that Pb grows layer-by-layer, nucleating as 2D islands, while Zr tends to form three-dimensional islands. At room temperature, the Zr surface concentration is strongly enhanced by the presence of oxygen, but at high temperatures, surface Pb is found to be stabilized by the presence of an oxygen ambient, illustrating the importance of real-time, in situ analysis of the growth layer as opposed to more conventional surface analytical methods which require interruption of the deposition process in order to characterize the film surface.     

光学薄膜制备用的多离子束电子束系统

本文介绍一种新型的光学薄膜制备用多离子束电子束系统。