Evolution of texture in electrodeposited Ni/Cu layered nanostructures

The objective of this research was to study the evolution of crystallographic texture in electrodeposited Ni/Cu laminated nanostructures. Thick films (14-40 µm) consisting of nickel and copper nanolayers (7-27 nm) were fabricated on annealed polycrystalline copper substrates using an electodeposition technique. The microstructure of the deposits was varied by changing the deposition time of each layer and the electrolyte temperature. X-ray diffraction, transmission electron microscopy and scanning electron microscopy were applied to characterize the deposits. Three microstructural behaviours were observed. The deposit with a very fine bilayer thickness (7 nm) was composed of coherent layers parallel to the substrate surface. This deposit replicated the cube orientation of the substrate and showed a strong ?100? texture throughout the thickness of the deposit. An increase in the bilayer thickness (17 and 27 nm) caused a change in the texture from ?100? on the substrate side to ?111? on the solution side. This change in texture is suggested to be associated with a change in the deposition front orientation from {100} to {110} and the subsequent twinning of the cube-oriented crystals. A decrease in the electrolyte temperature inhibited faceting of the interface and hence no twinning was observed.     

Synthesis,structure, and electrochemical properties of epitaxial perovskite La0.8Sr0.2CoO3 film on YSZ substrate

Epitaxial films of the perovskite, La_0.8Sr_0.2CoO₃ (LSC), for SOFCs cathode were deposited on yttria-stabilized zirconia (YSZ) single crystals by pulsed laser deposition method. The films were characterized by thin-film X-ray diffraction measurement, atomic force microscopy (AFM), transmission electron microscope (TEM), and ac impedance spectroscopy. The film orientations depend on the substrate planes. The LSC films on the YSZ (100) and (111) substrates showed the (110) orientation with different twin structures, while those on the YSZ (110) had (100) and (112) orientations. Surface morphology of the films also depends on the substrate orientations. These films showed different electrode properties depending on the orientations. The relationships between the properties, the film orientations, surface morphology, and lattice misfit are discussed.     

Formation of bcc-Ni thin film on GaAs(100) substrate and phase transformation from bcc to fcc

Ni thin films are prepared on GaAs(100) single-crystal substrates at room temperature by using an ultra-high vacuum radio-frequency magnetron sputtering system. The growth behavior and the crystallographic properties are studied by in-situ refection highenergy electron diffraction and pole-figure X-ray diffraction. In an early stage of film growth, a metastable bcc Ni(100) single-crystal film is formed on GaAs(100) substrate, where the bcc structure is stabilized through hetero-epitaxial growth. With increasing the film thickness, fcc crystals coexist with the bcc(100) crystal. High-resolution cross-sectional transmission electron microscopy shows that the film consists of a mixture of bcc and fcc crystals and that a large number of planar faults exist parallel to the fcc(111) close-packed plane. The results indicate that the bcc structure starts to transform into fcc structure through atomic displacement parallel to the bcc{110} close-packed planes.     

YBCO涂层导体用YSZ缓冲层的快速制备研究

基于反应直流溅射法,采用镶嵌有钇粒的金属锆作为靶材,去离子水蒸汽为氧化反应气体,在有Y2O3种子层的双轴织构Ni-5at.%W基带上,系统地研究了温度和卷绕速度对YSZ阻挡层薄膜结构及表面形貌的影响。X射线衍射(XRD)分析表明,生长温度在700℃时制备的薄膜呈现明显的(002)取向;原子力显微镜(AFM)分析显示,该温度下制备的薄膜表面致密、无孔洞、无裂纹。在不同的卷绕速度下,虽然薄膜均为纯c轴取向,但其均方根粗糙度(RMS)和微粒大小均有较大差别。快速制备可达到抑制基片表面氧化、助于薄膜取向改善、提高薄膜制备效率的目的。     

Some aspects of interactions between HTSC-films and substrates

Different aspects of the interaction between YBa₂Cu₂O_y(YBCO) films and (100) ZrO₂〈Y〉 (YSZ) substrates have been investigated. It was determined using X-ray diffraction methods that the structural mismatch between the film and the substrate leads to a film deformation throughout its thickness. At the same time a strained layer appears in the substrate, whose thickness is proportional to the film thickness. The surface morphology changes of YBCO films which take place with variation of the growth temperaturet_sin the vicinity of the optimum temperature lead to changes of the film grain structure probably connected with nucleation centers. Tl₂Ba₂CaCu₂O_y(TBCCO) films on YSZ substrates were also synthesized. It was found that the dependence of the TBCCO film surface morphology changes with annealing temperature and the dependence of YBCO film surface morphology changes ont_sare similar.     

T1系超导薄膜金属涂层的生长与特性研究

我们研究了T1-2212超导薄膜在带有YSZ／CeO2缓冲层和带有Ce02／YSZ／CeO2缓冲层的Ni金属RABiTS基带上的生长情况．基带上的缓冲层是采用PLD方法制备的，T1-2212薄膜的制备采用了磁控溅射和后热处理两步方法．XRD实验结果表明。T1-2212薄膜都具有很好的C轴垂直于膜面的织构，并具有双向外延生长特性．在CeO2／YSZ／CeO2／Ni基带上制作的T1-2212薄膜的Tc达到102．8K，J,（77K,0T）达到2.6MA／cm^2；在YSZ／CeO2／Ni基带上薄膜Tc可达97．7K，Jc（77K,0T）也可以达到0．45MA／cm^2.     

Tl系超导薄膜金属涂层的生长与特性研究

我们研究了Tl-2212超导薄膜在带有YSZ/CeO2缓冲层和带有CeO2/YSZ/CeO2缓冲层的Ni金属RABiTS基带上的生长情况.基带上的缓冲层是采用PLD方法制备的,Tl-2212薄膜的制备采用了磁控溅射和后热处理两步方法.XRD 实验结果表明,Tl-2212薄膜都具有很好的C轴垂直于膜面的织构,并具有双向外延生长特性.在CeO2/YSZ/CeO2/Ni基带上制作的Tl-2212薄膜的Tc达到102.8 K,Jc(77 K,0 T)达到2.6 MA/cm2;在YSZ/CeO2/Ni基带上薄膜Tc可达97.7 K,Jc(77 K,0 T)也可以达到0.45 MA/cm2.     

Electrical conductivity of thick film YSZ

When yttria-stabilized zirconia (YSZ) electrolyte is coated and co-sintered on top of Ni–YSZ anode support, the measured conductivities of YSZ thick films (10–30 μm thick) are often lower than that of bulk YSZ. In this study, we found the observation by fabricating free-standing YSZ thick films and measuring and comparing in-plain and across-plain conductivities. The in-plane conductivity of free-standing YSZ film matched very well with the conductivity of mm-thick bulk sample. It was further shown that the conductivity decrease can be minimized by using better electrode morphology.Another factor that decreases the film conductivity was identified when the thick film was reduced. The conductivity decrease, ∼26% after reduction for 1h in humidified hydrogen gas, was due to Ni-doping into YSZ during sintering process.In order to minimize the conductivity drop of thick film YSZ during SOFC (solid oxide fuel cell) operation, an intermediate layer may be used between YSZ and anode support to prevent Ni-doping during co-sintering process in addition to the well-designed electrode morphology.     

Deposition and characterization of YBCO/CeO2/YSZ/CeO2 multilayers on biaxially textured Ni substrates

CeO2/YSZ/CeO2 buffer layers were deposited on biaxially textured Ni substrates by pulsed laser deposition. The influence of the processing parameters on the texture development of the seed layer CeO2 was investigated. Epitaxial films of YBCO were then grown in situ on the CeO2/YSZ （yttria-stabilized ZrO2）/CeO2-buffered Ni substrates. The resulting YBCO conductors exhibited self-fleld critical current density Jc of more than 1 MA/cm^2 at 77K and superconducting transition temperature Tc of about 91K.     

A comparative study of YBa2Cu3O7-δ/YSZ bilayer films deposited on silicon-on-insulator substrates with and without HF pretreatment

Highly epitaxial YBa2Cu3O7-δ (YBCO) and yttria-stabilized zirconia (YSZ) bilayer thin films have been deposited on silicon-on-insulator (SOI) substrates by using in situ pulsed laser deposition (PLD) technique. In the experiment, the native amorphous SiO2 layers on some of the SOI substrates are removed by dipping them in a 10% HF solution for 15 s. Comparing several qualities of films grown on substrates with or without HF pretreatment, such as thin film crystallinity, general surface roughness, temperature dependence of resistance, surface morphology, as well as average crack spacing and crack width, naturally leads to the conclusion that preserving the native SiO2 layer on the surface of the SOI substrate can not only simplify the experimental process but can also achieve fairly high quality YSZ and YBCO thin films.     

Fabrication and performance characterization of Al/Ni multilayer energetic films

Al/Ni multilayer bridge films, which were composed of alternate Al and Ni layers with bilayer thicknesses of 50, 100 and 200 nm, were prepared by RF magnetron sputtering. In each bilayer, the thickness ratio of Al to Ni was maintained at 3:2 to obtain an overall 1:1 atomic composition. The total thickness of Al/Ni multilayer films was 2 μm. XRD measurements show that the compound of AlNi is the final product of the exothermic reactions. DSC curves show that the values of heat release in Al/Ni multilayer films with bilayer thicknesses of 50, 100 and 200 nm are 389.43, 396.69 and 409.92 J?g^?1, respectively. The temperatures of Al/Ni multilayer films were obviously higher than those of Al bridge film and Ni bridge film. Al/Ni multilayer films with modulation of 50 nm had the highest electrical explosion temperature of 7000 K. The exothermic reaction in Al/Ni multilayer films leads to a more intense electric explosion. Al/Ni multilayer bridge films with modulation period of 50 nm explode more rapidly and intensely than other bridge films because decreasing the bilayer thickness results in an increased reaction velocity.     

Effects of underlayer materials and substrate temperatures on the structural and magnetic properties of Nd2Fe14B films

Thin films of Nd_2Fe_{14}B were fabricated on heated glass substrates by dc magnetron sputtering. Different material underlayers (Ta, Mo, or W) were used to examine the underlayer influence on the structural and magnetic properties of the NdFeB films. Deposited on a Ta buffer layer at 420℃, the 300 nm thick NdFeB films were shown to be isotropic. But when the substrate temperature T_s was elevated to 520℃, the Nd_2Fe_{14}B crystallites of (00l) plane were epitaxially grown on Ta (110) underlayer. In contrast, Mo (110) buffer layer could not induce any preferential orientation in NdFeB film irrespective of the substrate temperature or film thickness. The W buffer layer was found to be most effective for the nucleation of Nd_2Fe_{14}B crystallites with c-axis alignment perpendicular to the film plane when T_s<490℃. But at T_s=490℃ the magnetic layer became isotropic. The maximum coercivity obtained was about 995 kA/m for the 100nm film deposited on W underlayer at 490℃. These variations were tentatively explained in terms of the lattice misfit between the underlayer and the magnetic layer, combined with the considerations of underlayer morphologies.     

Research on CeO2 cap layer for YBCO-coated conductor

Two groups of coated conductor samples with different thicknesses of CeO2 cap layers deposited by pulsed laser deposition （PLD） under the same conditions have been studied. Of them, one group is of CeO2 films, which are deposited on stainless steel （SS） tapes coated by IBAD-YSZ （IBAD-YSZ/SS）, and the other group is of CeO2/YSZ/Y2O3 multilayers, which are deposited on NiW substrates by PLD for the fabrication of YBCO-coated conductor through the RABiTS approach. YBCO film is then deposited on the tops of both types of buffer layers by PLD. The effects of the thickness of the CeO2 film on the texture of the CeO2 film and the critical current density （Jc） of the YBCO film are analysed. For the case of CeO2 film on IBAD-YSZ/SS, there appears a self-epitaxy effect with increasing thickness of the CeO2 film. For CeO2/YSZ/Y2O3/NiW, in which the buffer layers are deposited by PLD, there occurs no self-epitaxy effect, and the optimal thickness of CeO2 is about 50 nm. The surface morphologies of the two groups of samples are examined by SEM.     

Structural characterization of La0.9Ba0.1MnO3/Y-ZrO2 film by X-ray diffraction

Perovskite manganite La_0.9Ba_0.1MnO₃(LBMO) films were deposited on (0 0 1)-oriented single crystal yttria-stabilized zirconia (YSZ) substrate by 90° off-axis radio frequency magnetron sputtering. The film thickness ranged from 10 nm to 100 nm. Grazing incidence X-ray diffraction technique and high resolution X-ray diffraction were applied to characterize the structure of LBMO films. The LBMO film mainly consisted of (0 0 1)-orientated grain as well as weakly textured (1 1 0)-orientated grain. The results indicated that an amorphous layer with thickness of about 4 nm was formed at the LBMO/YSZ interface. The strain in LBMO film was small and averaged to be about -0.14%. The strain in the film was not lattice mismatch-induced strain but residual strain due to the difference in thermal expansion coefficient between film and substrate.     

Formations and morphological stabilities of ultrathin CoSi₂ films

In this paper we investigate the formations and morphological stabilities of Co-silicide films using 1-8-nm thick Co layers sputter-deposited on silicon(100) substrates.These ultrathin Co-silicide films are formed via solid-state reaction of the deposited Co films with Si substrate at annealing temperatures from 450℃ to 850℃.For a Co layer with a thickness no larger than 1 nm,epitaxially aligned CoSi2 films readily grow on silicon(100) substrate and exhibit good morphological stabilities up to 600℃.For a Co layer thicker than 1 nm,polycrystalline CoSi and CoSi2 films are observed.The critical thickness below which epitaxially aligned CoSi2 film prevails is smaller than the reported critical thickness of the Ni layer for epitaxial alignment of NiSi2 on silicon(100) substrate.The larger lattice mismatch between the CoSi2 film and the silicon substrate is the root cause for the smaller critical thickness of the Co layer.     

Effect of electrically degenerated layer on the carrier transport property of ZnO epitaxial thin films

ZnO films were prepared on (1 1 1) YSZ and (0 0 0 1) sapphire by pulsed laser deposition method. Effect of lattice mismatch on the carrier transport properties of ZnO epitaxial thin films was investigated. The carrier mobility of the ZnO films on YSZ was larger than that of ZnO/sapphire due to smaller lattice mismatch when the thickness was below 150 nm. The effect of electrically degenerated layer on the carrier transport property increased with decreasing the film thickness of ZnO film. The carrier density and electron mobility of 20 nm-thick-ZnO film on either substrate were regardless of the temperature. We concluded that the dominant carrier scattering mechanism in ZnO ultra thin films is double Schottky barriers at the grain boundary and that their height depends on the carrier concentration.     

Ni掺杂ZnO薄膜的结构与光学特性研究

使用射频磁控溅射法成功制备了不同掺杂浓度（0—7at.%）的ZnO:Ni薄膜.X射线衍射的θ-2θ和摇摆曲线扫描结果表明,5at.%Ni掺杂ZnO薄膜具有沿c轴方向最佳的择优取向生长特性,（002）衍射峰向大角度方向移动揭示了Ni杂质被掺入ZnO晶格中占据Zn位.ZnO:Ni薄膜具有较好的可见光透明特性,拟合发现薄膜的光学带隙随Ni掺杂量的增加由3.272 eV线性降低到3.253 eV.未掺杂薄膜在550 nm处呈现出一个绿色发光峰,掺入Ni杂质后薄膜主要表现了以430 nm为中心的蓝色发光,分析认为它们分别源于薄膜中O空位和Zn填隙缺陷发光. 关键词： ZnO:Ni薄膜 结构特性 光学带隙 光致发光     

Improved initial epitaxial growth of superconducting YBa2Cu3O7 thin films on Y–ZrO2 substrates with a La1.85Sr0.15CuO4 buffer layer

Epitaxial thin films of YBa₂Cu₃O₇ (YBCO) have been deposited on Y–ZrO₂ (YSZ) substrates by means of the pulse laser deposition technique. It has been found that the initial epitaxy of YBCO thin films grown on YSZ can be significantly improved by using La_1.85Sr_0.15CuO₄ (LSCO) as a buffer layer. X-ray diffraction measurements show that the epitaxial YBCO films have single in-plane orientation with YBCO [100]LSCO [100] and LSCO [100]YSZ [110]. The real-time resistance measurements reveal that with LSCO buffer layers the initial formation of the YBCO ultra-thin films changes from the island growth to the layer-by-layer growth.     

Secondary electron microscopy and transmission electron microscopy studies of carbon nanotubes in C-Ni films

Carbon nanotubes films have been studied with SEM and TEM. The studied films were obtained using a two step method: PVD process and CVD process. Strongly defected and curled carbon nanotubes containing Ni nanoparticles formed the film with thickness of about 300–400 nm. Observed carbon nanotubes were of lengths from 100 nm to 300 nm and did not stick to each other.     

Angular dependence of the in-plane magnetization of (100) Cu/Ni/Cu structures

(100) Cu/Ni/Cu sandwich structures have been deposited on (100) Si using the (100) Cu epitaxially grown as the seed layer. The in-plane epitaxial relation between the metal films and Si allows the study of angular dependence of the magnetization for the field parallel to the film plane. Keeping the Cu layers at 1000 Å each and varying the Ni layers between 50 and 1000 Å, the magnetization along the [110] edge is larger than that along the [100] one. This is observed for both structures with a Ni thickness of 1000 and 500 Å, respectively. For the thinner Ni layers, the angular dependence is interfered by the reversal in magnetic anisotropy reported earlier. For such structures, a squared hysteresis loop is observed for the field perpendicular to the film plane, whereas one with little loop is observed for the in-plane magnetization. The angular dependence observed for the 1000 and 500 Å Ni films is the same as that of single crystal Ni. The (100) Cu/Ni/Cu films thus grown can be used for other magnetic measurements in the exploration of two-dimensional magnetism with controlled orientations.