High-rate Pulsed Laser Deposition Research Articles

Thin-film lithium batteries with 0.3–30 μm thick LiCoO2 films fabricated by high-rate pulsed laser deposition

High-rate pulsed laser deposition was applied to the preparation of thick LiCoO2 cathode films, which were then used in the fabrication of thin-film batteries. The deposition rate of the LiCoO2 films was 2–3 μm/h. The thin-film batteries showed an increase in capacity up to 470 μAh/cm2 with increasing cathode film thickness. The rate dependence of discharge capacity was analyzed using a diffusion model in which the chemical diffusion coefficient of lithium in the cathode determines the dynamic capacity. For the initial stage of discharge, the chemical diffusion coefficient was estimated to be 10−10 cm2/s. Conversely, the chemical diffusion coefficient decreases to ~10−12 cm2/s at the end of discharge. From the diffusion model, the available capacity was estimated as a function of cathode thickness. Crack formation inside the LiCoO2 film is also suggested as a cause of capacity limitation.

Pinning Properties of PLD-Obtained GdBa2Cu3O7-x Coated Conductors Doped With BaSnO3

This work is devoted to high-rate pulsed laser deposition of BaSnO 3 -doped superconducting films on long buffered metal tape substrates with the use of pilot-scale equipment and common deposition conditions typical for commercial 2G high-temperature superconducting wire production at SuperOx Japan. BaSnO 3 inclusions were found to grow as nanocolumns elongated along the vertical direction and having biaxial texture. With BaSnO3 doping, the angular dependence of critical current measured at 77 K became much more isotropic. At 77 K, the lift-factor (I c /I c sf ) values in BaSnO 3 -doped samples increased almost twice in 0.5-3 T magnetic field in perpendicular orientation; at the same time, the absolute critical current increased only by 10%. At 4.2 K, in 0.5-3 T perpendicular field, the absolute critical current in doped samples increased 1.8 times.

Processing of Long-Length YBCO Coated Conductors Based on Stainless Steel Tapes

Recent progress is reported in the development of long lengths (up to 100 m) of YBCO coated conductors with good mechanical stability and improved critical current homogeneity. A non-magnetic CrNi stainless steel tape, 0.1 mm thick, is employed as a substrate tape. Prior to deposition, the tape is coated with yttria stabilized zirconia in the form of a bi-axially textured buffer layer, using a novel "alternating beam assisted deposition" technique. After deposition of a ceria cap layer onto the buffer, YBCO films are deposited employing a high-rate pulsed laser deposition method that allows higher critical current densities and incurs a lower YBCO loss (~10%) than other deposition techniques. The last processing step consists of coating the with a thin layer of silver or gold and a 2-40 mum thick copper shunt layer. In 40 m long tapes with a 1 mum thick YBCO film (at 77 K and zero external field), critical current, J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> , up to 235 A per cm-width were obtained. Higher critical currents, up to 574 A per cm, were achieved in short 0.2-7 m sections corresponding to current densities, J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> , of up to 4.4 MA/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . The critical current homogeneity and performance of our improved coated conductors under applied temperature cycling, multiple quench-recovery cycles, and repeated bending are reported.

Large-area high-rate pulsed laser deposition of smooth TiC xN 1− x coatings at room temperature—mechanical and tribological properties

Titanium carbonitride (TiC x N 1− x ) hard coatings possess excellent tribological behavior in metal punching and forming as well as high biocompatibility. Because almost all PVD and CVD coating techniques for TiC x N 1− x coatings require substrate temperatures higher than 150–200 °C for reaching sufficient adhesion strength to the substrate surface, there is high demand in the development of large-area and high-rate low-temperature vacuum deposition processes. In the present work, this call was fulfilled by the application of the room temperature pulsed laser deposition (PLD) for TiC x N 1− x coating with various carbon ( x) and nitrogen contents. A pulsed Nd:YAG laser (wavelength: 1064 nm) was used for the vaporization of pure titanium targets in low-pressure N 2/C 2H 2 atmospheres. The highly ionized metal vapor was deposited onto polished substrates (molybdenum, AISI D2 steel), forming a nearly particulate-free, very smooth and dense film structures, which can be hardly reached by using other PVD techniques. The variation of the gas flow during deposition causes a change of the chemical composition and the microstructure of the nearly particulate-free coatings, and, consequently, of the mechanical and tribological properties. The solid solution hardening of the fcc TiN lattice by low contents of carbon increases the hardness and elastic modulus, while higher carbon contents decrease this effect. Furthermore, the maximum in hardness and elastic modulus correspond with the minima in the friction coefficients (∼0.2) and wear rates of both the coated disc and the counterparts (AISI 52100 (DIN 100Cr6) ball-bearing steel balls).

YBCO-Coated Conductors Manufactured by High-Rate Pulsed Laser Deposition

AbstractHigh-temperature superconductors of the second generation—coated conductors—are based on an architecture of YBCO films deposited on a well-textured substrate tape. The deposition technique used in the processing of YBCO films is responsible not only for both the resulting critical currents in the conductors and the cost efficiency of the employed production route, but also for the ultimate viability of the chosen technology. This article describes an advanced deposition method for YBCO films using high-rate pulsed laser deposition (HR-PLD).An elaborate variable azimuth ablation allows target roughening to be considerably reduced in the course of continuous deposition, and as a result, the integral deposition speed and speed stability can be increased to technologically interesting high values.Well-selected process parameters have been demonstrated to yield high currents of up to 480A/cm-width in short tapes and 360A/cm-width in 6-m-long tapes.Together with quasi-equilibrium heating, the HR-PLD method allows the processing of long-length YBCO-coated conductors and offers a cost-efficient route for their production on an industrial scale.

Critical currents in long-length YBCO-coated conductors

Recent progress in developing large-area HTS-coated stainless-steel(SS) tapes is reported. YBCO films have been grown on IBAD-YSZ buffered 0.1mm-thick SS foils using a high-rate pulsed laser deposition technique whichallows an increase of the deposition rate to 40 nm m2 h-1. YBCO-coated SS tapescontaining a shunt layer, with a length up to 5.5 m, have been manufacturedand tested. A model treatment was performed to describe an interchange ofcurrent between the shunt layer and the YBCO film. The optimal parameters of the shuntlayer have been employed to reduce the resistive loss in the coated tapes. Thecritical dc current of more than 105 A was observed in a 2 m-long and 10mm-wide coated tape.

Properties of ramp-edge Josephson junctions with a surface-modified barrier fabricated by high-rate PLD

YBa 2Cu 3O 7− δ (YBCO) ramp-edge Josephson junctions have been fabricated by pulsed laser deposition (PLD) with a relatively high deposition rate (∼50 nm/min). 200 nm thick YBCO films deposited on LaSrAlTaO x (LSAT) substrates in a PLD system with laser-beam scanning exhibited a typical T c of 88∼90.5 K. LSAT/YBCO bilayers were fabricated and then patterned to form a ramp structure. Electron cyclotron resonance ion bombardment and subsequent annealing in a various atmosphere were employed to form an amorphous layer and a recrystallized barrier layer on the ramp surface. Junction properties strongly depend on distance between the sample and the laser plume when upper layer YBCO is deposited. The junctions fabricated under optimum conditions exhibited resistively and capacitively shunted junction-like I– V curves with a typical I c R n product at 4.2 K of 1.0∼3.2 mV.

Transport and anisotropic properties of coated conductors deposited by PLD on steel substrates

Coated conductors deposited by a novel high-rate pulsed laser deposition (PLD) technique on ion-beam-assisted-deposition (IBAD) layers of yttria-stabilized zirconia (YSZ) on non-magnetic steel ribbons were investigated. An XRD analysis of the superconducting layers showed in-plane alignments with a FWHM from 10 to 25/spl deg/ and an out-of-plane alignment of better than 2/spl deg/. We report on the field and temperature dependence of the critical transport current density in these YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// films of various thickness. In addition, the angular dependence of the transport current at various external magnetic fields is presented. Thirdly, artificial pinning centers were introduced into the superconductors by neutron irradiation. The influence of these defects on the critical current densities and on the anisotropy ratio are discussed.

Large-area HTS-coated stainless steel tapes with high critical currents

Recent progress is reported in developing large-area HTS-coated stainless steel (SS) tapes. A new type of Cr-Ni SS exhibiting a high temperature resistance against oxygenation was employed as a substrate material. These SS tapes exhibit a favourable mechanical performance and allow a cost-efficient production. YBCO films have been grown on IBAD-YSZ buffered 0.1 mm-thick SS foils using a newly developed High-Rate Pulsed-Laser-Deposition (HR-PLD) technique which allows an increase of the film deposition rate by at least a factor of 20 compared to conventional PLD. The HR-PLD increases drastically the integral deposition rate to >35 nm m/sup 2//h keeping the "local" repetition rate of the deposition pulses at lower values of <20 Hz. For the shorter coated tapes (110/spl times/10 mm/sup 2/) critical current densities, J/sub c/'s, up to 23 kA/mm/sup 2/ were observed at 77 K. Long coated SS tapes with J/sub c/ of (4-6) kA/mm/sup 2/ were manufactured in dimensions up to 1 m/spl times/34 mm. HTS properties of the coated tapes are studied and discussed.

Pulsed laser deposition of oxide films by multi-kilowatt CO2 lasers

For realizing a high rate pulsed laser deposition (PLD) a pulsed 6 kW-CO2 laser conventionally used for laser machining was adapted by a suitable beam forming system. It allows intensities between 107 and 108 W/cm2 at a minimum pulse length of 100 μs. The targets consist of various compositions in the Al2O3–SiO2 system including the mullite phase. The deposition has been carried out in high vacuum. Even the average power of 200 W of the available 6 kW mostly used in these experiments due to the small sizes of the specially prepared targets yields mean deposition rates up to 100 nm/s. In-situ measurement of mass loss and momentum transfer on the target reveals that most of the material is ablated as microparticle, not as vapour. This corresponds with the cobblestone appearance of the films. Notwithstanding their rather coarse topography, they are dense without any kind of open porosity. This was also proved by mass loss investigations in oxidation experiments and by diffusion of 18O isotopes in combination with SNMS determination of the concentration profiles.