Cube Textured Ni Substrate Research Articles

Orientational domains in metalorganic chemical vapor deposited CdTe(111) film on cube-textured Ni

CdTe thin film was grown by metal organic chemical vapor deposition on cube-textured Ni substrate. The microstructures of the CdTe film and Ni substrate were studied using transmission electron microscopy (TEM) lattice imaging in cross sectional. The orientational relationships of multiple hetereoepitaxial domains in the CdTe film were examined by TEM diffraction. The observed epitaxy is [111]CdTe//[001]Ni. The adjacent domains in CdTe film have a 30° rotation with respect to each other as inferred by the observed different diffraction patterns obtained from different zone axes. The high resolution lattice imaging shows that lamellar twins dominate within each domain. Our results are compared with CdTe(111) film epitaxially grown on Si(001) substrate by molecular beam epitaxy reported in the literature.

Low temperature epitaxial growth of Ge on CaF2 buffered cube-textured Ni

Quasi-single crystal Ge films were grown on cube textured Ni substrate at a temperature of 350°C using an insulating buffer layer of CaF2. A direct deposition of Ge on Ni at 350°C was shown to alloy with Ni. From x-ray pole figure analysis, it was shown that Ge grew epitaxially with the same orientation as CaF2 and the dispersions in the out-of-plane and in-plane directions were found to be 1.7±0.1° and 6±1°, respectively. In the out-of-plane direction, Ge[111]‖CaF2[111]‖Ni[001]. In addition, the Ge consisted of four equivalent in-plane oriented domains such that two mutually orthogonal directions: Ge〈2̄11〉 and Ge〈01̄1〉 are parallel to mutually orthogonal directions: Ni〈1̄10〉 and Ni〈1̄1̄0〉, respectively, of the Ni(001) surface. This was shown to originate from the four equivalent in-plane oriented domains of CaF2 created to minimize the mismatch strain between CaF2 and Ni in those directions.

Texture Evolution in Ni Substrate Prepared by Powder Metallurgy and Casting Methods

Cube textured Ni substrate were fabricated for YBCO coated conductors from the initial specimens prepared by powder metallurgy (P/M) and casting and the effects of annealing temperature and reduction ratio on texture formation and microstructural evolutio were evaluated. The initial specimens were rolled by 98.6% and 99.2% reduction ratio and then annealed in the temperature range of 600°C to 1200°C. The microstructure and texture were evaluated by optical microscopy and X-ray pole-figure analysis. We observed that microstructure of the initial specimen varied with preparation methods.Texture analysis indicated that a strong cube texture formed for substrate made by P/M, and the degree of texture did not significantly vary with annealing temperature of 600°C~1100°C. On the other hand, the texture of substrate made by casting was more dependent on the annealing temperature and twin texture ({221}<221>) and several minor texture components started to form at 1000°C. In addition, the texture of substrate made by P/M was significantly dependent on the reduction ratio.

A single oxide buffer layer on a cube-textured Ni substrate for the development of YBCOcoated conductors by photo-assisted MOCVD

Large-scale commercial applications of high-temperature superconducting (HTS)YBa2Cu3O7−x (YBCO)-based second generation coated conductors require simple and cost-effectiveprocess technologies to fabricate the buffer layer(s) and YBCO superconducting layer.Sm0.2Ce0.8O2+x (SCO) thick films have been epitaxially deposited on roll-textured Ni substrates as the singlebuffer layer for HTS coated conductors by using high-rate photo-assisted metal–organicchemical vapour deposition (PhAMOCVD) at a relatively low deposition temperature of600 °C. YBCO superconducting films were then successfully deposited on these thick SCO singlebuffer layers by the same high-rate PhAMOCVD process, and yielded critical current densities(Jc)of ∼0.52 MA cm−2 at 77 K and zero applied field. X-ray diffraction and scanning electron microscopeanalyses of SCO/Ni samples revealed very good crystalline structure and surfacemorphology for the SCO single buffer layers. These results suggest that SCOsingle buffer layer, as well as the YBCO conductors, fabricated by the high-ratePhAMOCVD technique may offer great potential for manufacturing YBCO coatedconductors.

Investigation of Processing Variables of Ni Substrate for YBCO Coated Conductors

We fabricated cube textured Ni substrates for YBCO coated conductors from the initial specimens prepared by powder metallurgy (P/M) and casting and evaluated the effects of annealing temperature on microstructural evolution and texture formation. To characterize the roles of the two preparation methods, the initial specimens were prepared to be of the same size and experienced the same rolling conditions, and were then annealed in the temperature range of 600/spl deg/C to 1200/spl deg/C. The texture was evaluated by X-ray pole-figure analysis and transmission electron microscopy (TEM). The texture analysis indicated that a strong cube texture formed for the substrate made by P/M and this texture did not vary significantly with annealing temperature in the range of 600-1200/spl deg/C. On the other hand, the texture of the substrate made by casting was more dependent on the annealing temperature, and a twin texture ({221} ) and several minor texture components began to form at 1000/spl deg/C. Microstructural observation showed that the morphology of deformation band together with micro-band in the as-rolled tape prepared by P/M was more homogeneous and of higher density than that produced by casting, resulting in a strong cube texture in wider range of annealing temperatures and a finer microstructure after recrystallization.

Formation of Strongly Biaxial-Textured Ni Layer for YBCO Coated Conductor by Electrodeposition Process

A new method of strongly biaxial-textured Ni substrate for YBCO coated conductor has been developed by electrodeposition using cube-textured cathode such as Ni single crystal, RaBiTS-processed Ni or Ni-W tape. Electrodeposited Ni layers using Ni single crystal as a cathode were characterized with /spl theta/-scan and /spl phi/-scan methods, and it showed excellent out-of-plane (/spl Delta//spl theta/=1.6/spl deg/) and in-plane alignment (/spl Delta//spl phi/=3.6/spl deg/). In addition, electrodeposited Ni layers using RaBiTS tape as a cathode show good biaxial texture (/spl Delta//spl theta/=5.7/spl deg/,/spl Delta//spl phi/=9.6/spl deg/) and smooth surface. XRD characterization shows that biaxial texture of cathode was transferred to electrodeposit and texture of electrodeposited Ni layers changes with deposition time. Finally, a CeO/sub 2/ buffer layer has been deposited by MOD process to show the compatibility of substrate with further buffer layer processing. Our modified electrodeposition process shows good possibility of providing a simple and effective way to high quality cube-textured Ni substrates for YBCO coated conductor.

Fabrication and characterization of cube textured Ni substrate for YBCO coated conductors

We fabricated Ni-substrates for YBCO coated conductors applying by powder metallurgy technique and evaluated the effects of pressing and annealing time on the texture. Compacts were prepared applying uniaxial or isostatic pressure. The texture of the substrate, made by applying cold isostatic pressure (CIP), was stronger than that by uniaxial pressure. We attribute this to the fact that the CIP method provided higher density and more uniform density distribution. The texture of the substrate made by CIP had a strong 4-fold symmetry and [111]/spl par/ND texture after annealing at a temperature of 1000 /spl deg/C. It was noted that the degree of texture was almost independent of annealing time and the full-width at half-maximum (FWHM) of in-plane and out-of-plane were measured to be in the range of 9.55/spl deg/ - 10.53/spl deg/ and 8.57/spl deg/ - 9.85/spl deg/, respectively. The development of strong cube texture and high fraction of low angle grain boundaries of Ni-substrates made by powder metallurgy technique in our study was considered to be useful in the deposition of YBCO coated conductors.

Microstructure of RE 2O 3 layers on cube textured Ni substrates

We investigated the structure and alignment of epitaxial Y 2O 3 and Gd 2O 3 films on cube textured Ni(0 0 1) substrates and used the findings to develop a general interpretation of the morphology of RE 2O 3 films (RE=Y or a rare earth element) on cube textured nickel and nickel-based alloys. The [1 0 0] axis of RE 2O 3 oxides mostly prefers aligning to the Ni[1 1 0] axis, while the [0 0 1] axis is aligned with the Ni[0 0 1] axis. This (2 2 ×2 2 )R45° extended domain matching (EDM) seems to be favored by a high coincidence site density (CSD) with the Ni(0 0 1) surface atoms, in spite of the existence of large lattice mismatches to Ni(0 0 1). Meanwhile a 3×3 EDM is not favored on Ni(0 0 1), in spite of the relatively small lattice mismatch to Ni(0 0 1), because of the existence of a low CSD. The broad mosaic distributions of RE 2O 3(0 0 l) grains (6–9° full-width at half-maximum) indicate that RE 2O 3 layers prefer growing along the Ni(0 0 1) planes rather than along the Ni surface, a condition presumably induced by the favorable energetics for EDM.

Deposition of YBCO films by high temperature spray pyrolysis

The fabrication of YBCO coated conductors on flexible textured metallic substrates requires the deposition of biaxially textured buffer layers and superconducting films. In this study we have prepared YBCO thin films on single crystal SrTiO 3 substrates and cube textured Ni substrates by spray pyrolysis. The Ni substrates have been pre-buffered with CeO 2/YSZ/CeO 2, layers deposited by pulsed laser deposition. Spray pyrolysis of nitrate solutions has been performed directly on heated substrates at temperatures between 800 and 900 °C without need for a subsequent annealing step. YBCO films deposited on both types of substrate are biaxially textured. Full width half maximum values determined from φ-scans are 8° and 20° for films on SrTiO 3 and buffered Ni substrates respectively. A transport J c value of 1.2×10 5 A/cm 2 at 77 K and zero field has been achieved on SrTiO 3 ( T c onset=91 K, ΔT c=6 K). χ ac susceptibility measurements of films on buffered Ni substrates show T c onsets of 88 K with ΔT c=18 K.

Preparation of oxide buffers on a cube-textured Ni substrate for coated conductor by CVD

CeO/sub 2/ and NiO films have been grown by metal-organic chemical vapor deposition (MOCVD) on cube-textured Ni substrate. At a lower deposition temperature of 400/spl deg/C, an amorphous film was formed. Deposited CeO/sub 2/ film showed a mixed texture of [100]<001> and [100]<011> orientations. Depending on the deposition condition, the transition from [100]<001> texture to [100]<011> orientation was observed for the CeO/sub 2/ film. The NiO film was deposited at 470/spl deg/C for 10 min. Deposition pressure was 10 Torr and the oxygen partial pressure was 0.91 Torr. The X-ray rocking curve and /spl phi/-scan showed that the NiO film has a bi-axial texture with a [100]<001> orientation. The out-of-plane and the in-plane deviation were measured as 4.2/spl deg/ and 6/spl sim/7/spl deg/ from the FWHM of [200] and [111] planes, respectively.

Studies of the improvement in microstructure of Y2O3 bufferlayers and its effect on YBa2Cu3O7-x film growth

Two kinds of Y2O3 buffer layers have been directlydeposited on cube-textured Ni substrates by electron beam evaporation underdifferent gas pressures. One is deposited at 10-5 Torr air (asingle-layer buffer). In order to reveal the improvement of the microstructure,the other is formed at first under 5×10-4 Torr and then10-6 Torr of N2 (a double-layer buffer). As a result, thedouble-buffer layer obtained is more than 97% {100} orientation and is arelatively denser structure. YBa2Cu3O7-x overlayersare deposited by pulsed-laser deposition on these buffer layers. Large YBa2Cu3O7-x pop-off areas are seen for the single-buffersamples. These areas are eliminated on the double-layer buffer. However, thecritical current does not increase appreciably for the YBa2Cu3O7-x film on the double-layer buffer, even though themicrostructure of the buffer is improved. Other defects probably yieldedpercolative current flow and a low critical current density in the YBa2Cu3O7-x layers.

Direct deposition of CeO2 films on Ni metal substrate by chemical vapor deposition

Cerium dioxide thin films have been grown in-situ directly on cube textured Ni substrate by metal-organic chemical vapor deposition (MOCVD). At a lower deposition temperature of 400°C, an amorphous film was formed. The texture of crystalline CeO2 film was changed from (200) orientation to (111) orientation when the deposition temperature was increased from 450°C to 550°C. The growth rate was ~40 nm/min and the rms surface roughness was 50 nm for the CeO2 film deposited at 450°C for 10 min. Surface roughness of the film was increased with the development of (111) orientation. Deposited CeO2 film showed a mixed texture of (100) and (100) orientation. Depending on the deposition condition, the transition from (100) texture to (100) orientation was observed.

Growth conditions and microstructure of Y 2O 3 buffer layers on cube-textured Ni

Y 2O 3 films were deposited on cube-textured Ni substrates by electron-beam evaporation as part of a buffer layer study for YBa 2Cu 3O 7− δ (YBCO) coated conductors. Their microstructure was observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and their crystallographic texture and surface roughness evaluated by X-ray diffraction (XRD) and atomic force microscopy (AFM). Previous studies showed the Y 2O 3 surface normal changed from {100} to {111} on decreasing the deposition chamber pressure from 10 −5 to 10 −6 Torr. In this work, 300 nm thick Y 2O 3 buffer layers were deposited at two different deposition chamber pressures, ∼5×10 −4 Torr N 2 and ∼2×10 −5 Torr air, so as to make the {100} orientation dominant. However, the morphology of the Y 2O 3 buffer layers was significantly affected by changing the deposition chamber pressure, the lower pressure buffer layer being denser and smoother than that made at the higher pressure. The Y 2O 3 grains in a 600 nm thick Y 2O 3 buffer layer grown under 2×10 −5 Torr air became larger and more uniformly square as the film grew thicker. The Y 2O 3 grown on thermally grooved Ni deposited at 2×10 −5 Torr air, showed 〈111〉-oriented grains near the grooves. This local imperfection in the texture could lead to significant barriers to supercurrent flow in the YBCO overlayer.

Fabrication of YBCO thick films on cube textured Ni substrate with NiO intermediate layer

High quality, sharp cube textured Ni substrates have been fabricated by a cold rolling and a recrystallization annealing process. X ray results show that there are some problems to be noted in the prevalent quality evaluation for a cube textured Ni substrate. In-plane-aligned, c axis-oriented YBa/sub 2/Cu/sub 3/O/sub 7/ (YBCO) thick films were grown on the textured Ni substrate with self-oxidized NiO intermediate layer by an ink-printed and floating zone heating method. The values of the resistively measured T/sub c/ (onset) were 86 K. This is a very useful and promising method for producing the long YBCO tapes with high J/sub c/, although J/sub c/ is lower at present.

Laser-ablation deposition of CeO 2 thin films on biaxially textured nickel substrates

Ceria buffer layers were deposited by pulsed laser ablation on (100)[001] cube-textured Ni substrate for the fabrication of high-current Y–Ba–Cu–O tapes for power applications. The films were grown both on Pd-buffered Ni and on pure Ni substrates. The CeO 2 film deposited directly on Ni was not fully epitaxially grown as it had a polycrystalline component. On the contrary, the θ–2 θ X-ray diffraction pattern of Ni–Pd–CeO 2 architecture contained only the (h00) peaks of Pd, Ni and CeO 2, indicating good epitaxy of Pd and CeO 2 on Ni, and the pole figure showed (100)[001] texture for Pd film and Ni substrate, and (100)[011] for CeO 2 film. The surface of the as-obtained CeO 2 films was smooth and continuous, hence appropriate for further YBCO film deposition.