化学溶液沉积制备涂层导体Eu0.3Ce0.7O1.85-x单一缓冲层

采用高分子辅助化学溶液沉积(PACSD)方法,在双轴织构的NiW(200)合金基底上沉积了厚度大于160 nm的Eu0.3Ce0.701.85-x(ECO)单一缓冲层.制得的ECO缓冲层双轴织构良好,表面平整、无裂纹.同时,Eu的掺杂提高了CeO2单一缓冲层薄膜的临界厚度.在沉积了ECO缓冲层的NiW基带上外延生长的YBCO薄膜,超导零电阻转变温度Tc0=86K,临界电流密度达到Jc(O T,77 K)=0.4 MA/cm2.本研究提供了一种操作简单、成本低廉、性能优良的制备涂层导体单一缓冲层的方法.     

Preparation and Performance of the Sm0.2Ce0.8O1.9-x Single Buffer Layer Fabricated with Dip-Coating

在双轴织构的Ni-5％W合金基带上,采用高分子辅助化学溶液沉积法通过提拉涂敷法,制备了厚度达250 nm的Sm0.2Ce0.8O1.9(SCO)外延织构单层缓冲层.通过严格控制前驱溶液的浓度、提拉速度、成相温度和热处理时间,所获的SCO单层缓冲层涂层平整、无微裂纹、且具有较强的(200)c轴外延织构.在其他条件假设不变的情况下,主要研究不同提拉速度对SCO缓冲层薄膜性能的影响.在此基础上,采用化学溶液法在SCO/NiW缓冲层上制备了YBCO超导层,其具有高度的双轴织构和均匀的表面形貌.结果表明:用提拉法获得的SCO单层缓冲层在具有适度的厚度下,仍然具有很好的织构传递特性,为低层本制造YBCO涂层导体长带提供了一条可靠的路线.     

Ce_(1-x)Sm_xO_(2-y)缓冲层的化学溶液法制备

采用化学溶液法在NiW(200)基带上进行了Ce1-xSmxO2-y(x=0,0.2,1)缓冲层的制备及生长机理研究。结果表明,化学溶液法可以成功制备出双轴织构的Ce1-xSmxO2-y缓冲层;在x=0和x=0.2的情况下,所制备的缓冲层有裂纹产生;但是随着x的增加,开裂现象被逐步抑制。对x=1的Sm2O3缓冲层而言,当厚度增加到120nm时依然没有产生裂纹,表明Sm2O3缓冲层可以作为单一缓冲层而得以使用。     

Preparation of YBCO Coated Conductors on RABiTS Substrate with Advanced TFA-MOD Method

YBCO high temperature coated conductors are the most promising candidate for large scale superconducting transmission cables and fault current limiters. A modified TFA-MOD method was applied to prepare YBCO layer on Rolling Assisted Biaxially Textured Substrate (RABiTS) with textured Y 2 O 3 /YSZ/CeO 2 buffer layers, resulting in reduced time and cost of fabrication. By using Cu naphthenate instead of Cu(TFA) 2 , the pyrolysis time of the YBCO precursors was reduced significantly. YBCO films with thickness ...     

金属基底上IBAD-YSZ缓冲层的生长机理

用离子束辅助沉积(IBAD)方法,变换辅助离子束的能量和束流密度,在Hastelloy基底上制备了钇稳定氧化锆(YSZ)薄膜,作为涂层导体的缓冲层。XRD的结果显示:在一定的离子能量和束流密度的范围内,能够制备出高质量双轴织构的(001)取向的YSZ缓冲层,随着辅助离子束能量和束流密度的增大,IBAD-YSZ的面外取向和面内织构都出现先变好又变坏的现象。文中用辅助离子束对薄膜破坏程度的各向异性对结果做了解释。     

Behavior of oxygen diffusion in buffer layers for coated conductors

We have evaluated the effect of annealing in oxygen atmosphere on the structure, texture and phase transformation of LZO films deposited on YSZ (yttria-stabilized zirconia) (0 0 l) single crystal substrates and textured NiW substrates by metal-organic deposition (MOD) method. The results show that the structure stability of the LZO films is heavily dependent on the oxygen partial pressure in annealing process. Then we have in details studied the behavior of oxygen diffusion in three kinds of buffer layer architectures on NiW substrates by varying the temperature, oxygen partial pressure and dwelling time in the annealing process. The oxygen diffusion within buffer layers leads to the oxidation of substrate, and even the texture and structure of buffer layers are destroyed with the increase of the thickness of the oxides layer related to NiW substrate. It reveals that the relative volume of oxides related to NiW substrate increases exponentially with the annealing temperature, and increases linearly with the annealing time at logarithmic scale. The relative intensity of texture peaks of buffer layers decreases and even disappears with the increase of the oxygen partial pressure in annealing process because of the acceleration of the oxidation reaction of substrate. The influence of annealing temperature, oxygen partial pressure and dwelling time on the oxygen diffusion is related to the intrinsic oxygen diffusion coefficient of buffer layers materials. Compared with the increase of oxygen partial pressure, the elongation of dwelling time shows a less effect on the oxidation rate of NiW substrate and a weak destruction of the texture of buffer layers. Except choosing the oxide materials with small oxygen diffusion coefficient as buffer layers in coated conductors, the degree of oxidation about NiW substrate could be greatly controlled and it would result in the less destruction of texture and structure of buffer layers by adjusting the annealing temperature, oxygen partial pressure and dwelling time in the process of YBCO deposition.     

Residual stress analysis of multi-layered buffer layers on Ni substrate for YBCO coated conductor

CeO₂/YSZ/CeO₂ buffer layer structure is one of the preferred buffer layers for fabrication of coated conductors. Textured CeO₂/YSZ/CeO₂ buffer layers are grown on biaxially textured Ni (100) substrate from the solution of Zr, Y, and Ce based organometalic compounds, solvent and chelating agent using reel-to-reel sol-gel technique. The film thickness is controlled by number of coating withdrawal speed and solution chemistry. Residual stresses arise during the manufacturing process of buffer layers depending on some factors. One of the most important is due to temperature variation. Effects of the temperature variation and coating thickness on residual stress in CeO₂/YSZ/CeO₂ buffer layers structure annealed at high temperature are analyzed theoretically. It is observed that the stress magnitudes reach high levels in the region of interlayer of different materials. The surface morphologies and microstructure of sample are characterized by ESEM and AFM. ESEM and AFM micrographs of the films revealed pinhole-free, crack-free, smooth and dense microstructures in the used manufacturing process.     

Influence of High-Temperature Annealing of the Textured Metal Ni–W Substrate on the Structural Properties of Seed Layer in HTS 2G tapes

The surface reconstruction of the textured metal tapes at the temperatures typical for the formation of the seed buffer Y₂O₃ layer of HTS 2G tapes have been revealed and studied for the first time. The influence of a terrace structure of the substrate surface on the characteristics of the texture of the seed Y₂O₃ layer has been shown. This effect is critically important to the deposition of buffer layers on the moving tape and allows to expand the temperature range of growth, in which the full inheritance of substrate texture by the seed Y₂O₃ layer is occurred.     

Development of high strength and strongly cube textured Ni-4.5% W/Ni-15% Cr composite substrate for coated conductor application

The development of thin, mechanically stronger and highly cube textured substrates is of great technological importance for increasing the engineering current density of the coated conductors. Nickel is a suitable substrate for this in view of its ability to form strong cube texture after heavy rolling and annealing and its excellent oxidation resistance. However, nickel is very soft (yield strength ~40 MPa) and this limits the processing to thin tapes. The ferromagnetism of Ni is also undesirable for ac application of coated conductors in magnetic fields. In the present paper we report on the development of Ni-4.5 at.% W/Ni-15 at.% Cr composite substrates of 80 and 40 μm thickness with strong cube texture, high yield strength (~200 MPa) and reduced magnetisation losses. The strong cube texture was obtained through an optimised two-step recrystallisation annealing following heavy cold working. It was found that the presence of non-cube texture forming alloy (Ni-15% Cr) in the inner core of the composite had no adverse affect on the growth of cube textured grains on the surface (Ni-4.5% W) even at a low substrate thickness of 40 μm. A significant improvement in the texture/misorientation distribution was observed in the CeO₂ buffer layer deposited on the composite substrate.     

Silicon oxynitride gas barrier coatings on poly(ether sulfone) by plasma-enhanced chemical vapor deposition

Thin silicon oxynitride (SiO_xN_y) has been deposited for a gas barrier layer on the surface of poly(ether sulfone) film using plasma-enhanced chemical vapor deposition (PECVD) of a mixture of hexamethyldisiloxane (HMDSO) and ammonia. The chemical structure of the deposited layer varied from organic to inorganic structures depending on RF plasma input power applied to the reaction system. A silicon-based undercoat layer, which has an organic/inorganic hybrid structure, was used as an interfacial buffer layer between the organic PES and inorganic SiO_xN_y layer. With the help of the undercoat layer, the dense inorganic SiO_xN_y layer gave a superior oxygen barrier property of 0.2 cm³/m² day at a critical coating thickness of ca. 20 nm. In a highly stressed SiO_xN_y film, the effect of the undercoat layer was remarkable in preventing crack formation during bending tests.     

CSD-La3TaO7薄膜外延生长行为研究

涂层导体是实现氧化物高温超导材料在液氮温区强磁场应用的关键材料。在低成本的轧制辅助双轴织构/化学溶液沉积（RABiTS/CSD）路线中,缓冲层的良好外延生长是实现超导层织构生长以及高载流能力的前提,因此研究缓冲层外延生长行为就显得非常必要。本文探索了CSD技术制备La3TaO7（LTO）缓冲层过程中前驱液的热分解行为以及热处理工艺路线对薄膜取向生长的影响,通过选取恰当的LTO前驱液以及快速热处理升温的方法最终获得了良好c轴织构的LTO薄膜。     

织构金属衬底上CSD-SrTiO3薄膜的制备

涂层导体是发展77 K液氮温区强磁场下电力应用的实用化关键材料。由于缓冲层层数增加会导致控制生长、微观组织和界面结构的难度增大,所以简化缓冲层结构对涂层导体制备工艺的简化和成本的降低非常重要。本研究探索了低成本的化学溶液沉积(CSD)技术制备SrTiO_3(STO)缓冲层过程中前驱液热分解行为以及薄膜制备工艺路线对薄膜外延生长的影响,通过选取恰当的前驱液以及引入籽晶层沉积的方法最终获得了具有良好c轴织构且表面光滑的STO薄膜。     

Textured zinc oxide prepared by liquid phase deposition (LPD) method and its application in improvement of extraction efficiency for 650 nm resonant-cavity light-emitting diode (RCLED)

In this article, we report on the textured zinc oxide (ZnO) prepared by liquid-phase deposition (LPD) method and apply it as a window layer of 650 nm resonant-cavity light-emitting diode to enhance the extraction efficiency. The treatment solution for LPD ZnO (LPD-ZnO) growth consists of ZnO powder saturated with hydrochloric acid (HCl) and hydrogen peroxide (H₂O₂). Temperature-controlled water bath system was used to maintain a constant temperature of 40 °C in LPD system. The experimental results indicate that the deposition rate was determined by the concentration of H₂O₂ and growth temperature, and the average roughness of LPD-ZnO is dominated by the concentrations of HCl. In order to perform the practicability of LPD-ZnO, the textured LPD-ZnO is used as a window layer of 650 nm AlGaInP/GaInP resonant-cavity light-emitting diode (RCLED) to enhance the light output power. In addition, the calculated results indicate that the optimum roughness for enhancing the light output power of RCLED is in the range of 80-100 nm, which are close to the experimental results. As compared to the conventional RCLED, the RCLED with textured LPD-ZnO, which has the optimum average roughness of 82 nm, performs a high light output power, a high external quantum efficiency, a narrow linewidth of electroluminescence spectrum and the same far-field angle.     

Giant changes in magnetic and magnetoresistive properties of CoFe/Cu multilayers at subnanosized variations in the thickness of the chromium buffer layer

The article discusses the magnetic and magnetoresistive properties of the [Co₉₀Fe₁₀/Cu] _n multilayers prepared by magnetron sputtering as a function of the type of the substrate and the material and thickness of a buffer layer (Co₉₀Fe₁₀, Cu, Cr, Fe). The multilayers with a chromium buffer layer exhibit a sharp transition from low-coercive to high-coercive state at low variations in the thickness of the chromium layer (from 15 to 20 Å). It has been demonstrated that the revealed sudden change in the hysteresis properties of the multilayers with a Cr buffer layer is accompanied by structural changes in the Cu and Co₉₀Fe₁₀ layers, characterized by the disappearance of the 〈111〉 texture at t _Cr > 20 Å. It has been found that the most efficient buffer layer, which at room temperature ensures a threefold increase in the magnetoresistance at a minimum increase in hysteresis, is the Co₉₀Fe₁₀ (15 Å) layer. It has been established that the substrate type ((100)Si, \((10\bar 12)\) Al₂O₃, glass) does not exert a significant effect on the magnetoresistive properties of the multilayers studied.     

LZO covered Cu-based substrates

A Cu-based substrate has been made by electrodepositing a Ni layer on top of cube-textured Cu tape obtained by an alternating mechanical/thermal treatment. It could be found that the volume fraction of the cube texture component of Cu tapes increased with the annealing temperatures for an optimized rolling process. When the annealing temperature is at 800 °C, the sharpness of cube texture is best. In order to fabricate LZO films on the Cu-based substrate, a Ni layer was added on top of the Cu tape by electroplating. The thickness of Ni layer not only affects the texture sharpness of the substrate, but also affects its thermal stability of texture. A thickness of 15 μm was efficient to protect the Cu tapes. Fabricating well bi-axially textured LZO film on this bi-metallic substrate proves that this new Cu-based substrate is a good choice for coated conductor.     

Field,temperature and thickness dependent electron transport in 5,5′-(2,6-di-tert-butylanthracene-9,10-diyl)bis(2-p-tolyl-1,3,4-oxadiazole)

Charge transport in 5,5′-(2,6-di-tert-butylanthracene-9,10-diyl)bis(2-p-tolyl-1,3,4-oxadiazole) is investigated as a function of temperature and organic layer thickness. The thickness dependence of the current indicates towards the trap charge limited conduction (TCLC) with a field and temperature dependent mobility. The density of trap states has been found to be dependent on sample thickness. As the thickness has increased from 80 nm to 120 nm, trap energy has correspondingly increased from 78 meV to 130 meV. TCLC model with Poole Frenkel type field dependent mobility has been fitted into the data and has been found in excellent agreement. Temperature dependency of zero field mobility (μ₀) and β has been estimated from the model.     

Room-temerature oxidation of Ni(110) at low and atmospheric oxygen pressures

Oxidation of atomically clean (110) nickel single crystals has been studied at room temperature and in pure oxygen or air at pressures from 1×10^–9 torr to atmospheric. X-ray photoelectron (XPS) and Auger electron spectroscopic (AES) data indicate that the standard regimes of dissociative chemisorption, oxide nucleation, and oxide lateral growth to coalescence were observed at low pressures. After the NiO layer coalesced at low pressures, exposure of the sample to atmospheric oxygen or air did not cause further growth of the oxide thickness at room temperature. Instead the growth of a high-energy shoulder on the O 1s XPS peak indicated the formation of Ni(OH)₂ on the surface. The presence of the hydroxide is consistent with high-resolution, electronenergy-loss spectroscopy (HREELS) data and chemical shifts in the Ni 2p spectra. While the oxide thickness is constant, the hydroxide thickness increased with exposure and time at high pressure. Surface analysis and lowpressure techniques are appropriate for the study of room-temperature, ambient-oxide formation and allow a determination of the kinetics and reaction products critical to the passivation of Ni.     

Engineering Design of High Quality GaN Epitaxy on Silicon Substrate Using Varying GaN/AlGaN Composite Buffer Structures

High quality GaN epitaxy thin films have been desired for the energy-efficient,solid-state semiconductor illuminating devices.Silicon substrates offer high crystal quality,low wafer cost,large wafer size,and potential integration with the well-established silicon processing technologies.However,due to the large mismatch in lattice constants and thermal expansion coefficients,it is still challenging to grow high quality GaN on silicon substrates.In this study,high quality GaN epitaxy has been engineering designed to grow on Si(111)substrate using varying GaN/AlGaN composite buffer structures by an Axitron 200 metal-organic vapor phase epitaxy deposition system.A thin AlN seed layer of 25 nm was firstly grown at 720℃.AlGaN layer of different thickness was then grown at 1050℃with subsequent GaN thin film until the total thickness reached 500 nm.The thickness of the subsequent GaN thin film could be increased by reducing the AlGaN thickness in the composite buffer structures.The results have shown that the lower GaN/AlGaN thickness ratio would decrease the dislocation density and provide crack-free,mirror-like upper GaN crystal thin film.On the other hand,the GaN/AlGaN thickness ratio could be designed to be 2-6 to balance the processing cost and the thin film quality for engineering applications.The dislocation density has been about 2×10 9 cm-2.In addition,dislocation close loop was observed near the GaN/AlGaN interface.The annihilation mechanism could be depicted by the reduction in dislocation strain energy.     

用化学溶液方法在NiW基底上制备Ce_(1-x)Zr_xO_2过渡层的研究

以乙酰丙酮铈和乙酰丙酮锆为前驱盐,以正丙酸和异丙醇为溶剂获得了前驱液。用化学溶液方法(CSD)在YSZ和自制的NiW基底上制备出了Ce1-xZrxO2过渡层。研究了前驱液成分、性质以及退火温度对其成相和取向的影响。用常规XRD分析其相成分和织构。结果表明,优化工艺下获得的纯CeO2和Zr掺杂的CeO2薄膜均具有良好的立方织构。通过X射线四环衍射仪测出的Ce1-xZrxO2过渡层的(111)Φ扫描和(200)摇摆曲线的半高宽值说明其具有很强的双轴织构。另外,Zr掺杂获得的薄膜的表面质量得到了明显改善,晶粒也得到了细化。     

BEHAVIOUR OF BUFFER LAYER IN JOINING OF SIALON CERAMICS TO STEEL 40Cr

The buffer layer material itself may be influential to the bond strength between active brazingfiller and ceramics.For Ag_(57)Cu_(38)Ti_5 filler metal,Cu or Ta is excellent buffer layer material,but Kovar or Ni-15Cr-15Co is worse.It was important to design a layer of soft buffer,suchas Cu,to relax interfacial stress rather than hard buffer layer,such as Mo,to avoid stress.There is an optimum thickness range of soft buffer layer,saying h/L=0.02—0.1. It was agood solution to the interfacial stress problem to use soft/hard buffer layer to increasemetal/ceramics joint strength.Finally,an idea of designing gradual materials as buffer layerbetween metal and ceramics was suggested.