On-axis Dc Magnetron Sputtering Research Articles

Significant increasing of onset temperature of FM transition in LSMO thin films

La0.67Sr0.33MnO3 (LSMO) thin films with a significant increased onset temperature of ferromagnetic transition were prepared using an on-axis dc magnetron sputtering from a stoichiometric ceramic target onto one-side polished MgO (001). The highest temperature of insulator-metal transition was observed at TP=416K. Magnetization hysteresis curves taken at T=398K indicate the beginning of the ferromagnetic transition above 400K. The negative magnetoresistance reaches 15% at a temperature of 400K. We show that the LSMO thin films with increased temperature values of resistance peak TP and Curie temperature TC are characteristic by a proper microstructure with distorted orthorhombic unit cells. This microstructure is developed during the layer growth, it is not caused by the underlying substrate and it is linked with an appropriate pseudocubic out-of-plane lattice parameter ac⊥, splitted Bragg reflections in rocking curves and as well as in reciprocal space maps.

Low field anisotropic colossal magnetoresistance in Sm0.53Sr0.47MnO3 thin films

Sm0.53Sr0.47MnO3 (SSMO) thin films (thicknesses ∼200 nm) were deposited by on-axis dc magnetron sputtering on the single crystal LSAT (001) substrates. These films are oriented along the out of plane c-direction. The ferromagnetic and insulator-metal transition occurs at TC ∼ 96 and TIM ∼ 91 K, respectively. The magnetization easy axis is observed to lie in the plane of the film while the magnetic hard axis is found to be along the normal to this. The magnetotransport of the SSMO films, which was measured as a function of angle (θ) between the magnetic field (H) and plane of the film, shows colossal anisotropy. Magnetoresistance (MR) decreases drastically as θ increases from 0° (H//easy axis) to 90° (H//hard axis). The out-of-plane anisotropic MR is as high as 88% at H = 3.6 kOe and 78 K. The colossal anisotropy has been explained in terms of the magnetic anisotropies at play and the magnetic domain motion in applied magnetic field.

Out-of-plane low field anisotropic magnetoresistance in Nd 0.51Sr 0.49MnO 3 thin films

A comparative study of the out-of-plane anisotropic magnetoresistance (AMR) in single crystalline and polycrystalline thin films of phase separated manganite Nd 0.51Sr 0.49MnO 3 has been carried out. On-axis DC magnetron sputtering was used to deposit the single crystalline films (30 and 100 nm in thickness) on single crystal (0 0 1) LaAlO 3 (LAO) and polycrystalline films (100 nm) on (1 0 0) Yttrium-stabilized ZrO 2 (YSZ) substrates. The in-plane and out-of-plane magnetotransport properties of these films differ significantly. A large low field AMR is observed in all the films. AMR shows a peak below the insulator–metal transition temperature in the single crystalline films, while the same increases monotonically in the polycrystalline film. Relatively larger low field AMR (∼20% at T=78 K and H=1.7 kOe) in the polycrystalline films suggests the dominance of the shape anisotropy.

Growth and annealing of La1.85Sr0.15CuO4+δ thin films on SrTiO3 substrates

Epitaxial La1.85Sr0.15CuO4+δ thin films were successfully deposited ontoSrTiO3(100) substrates by using on-axis DC magnetron sputtering. Several different annealing andcooling processes were performed in studying the influence of the annealing processes forLa1.85Sr0.15CuO4+δ thin filmsgrown on SrTiO3 substrates. By using a quenching method, we found that the method can tune thesuperconducting transition temperature in a large viable range without changing theLa/Sr ratio. We suggest that this effect is probably induced by releasing tensile strain forLa1.85Sr0.15CuO4+δ thin filmsgrown on SrTiO3 substrates.

Effects of surface treatment of single-crystal MgO substrates on the growth and properties of YBa/sub 2/Cu3O/sub 7-y/ films

The preferred orientation and the inplane alignment of YBa/sub 2/Cu/sub 3/O/sub 7-y/ (YBCO) thin films deposited on MgO [100] substrates by on-axis DC magnetron sputtering have been investigated. The deposition temperature highly influences the preferred orientation of films. Films were oriented with the a-axis perpendicular to the substrates for low temperature depositions and with the c-axis for high temperature depositions. In the c-axis oriented films, there exist YBCO grains with the a(or b)-axis parallel to MgO [100] and 4-5/spl deg/ -rotated ones. 45/spl deg/ -rotated grains exclusively grow under the conditions of higher temperatures and on the substrates treated by acid-etching. The volume ratio between both types of YBCO grains is strongly connected with critical current density, even in the c-axis oriented films. >

The role of magnet arrangement in synthesis of YBCO thin films by on-axis DC magnetron sputtering

We have investigated various processes of DC magnetron sputtering films with on-axis geometry. The study shelved that the quality of YBCO thin films not only depended on the sputtering parameters such as gas pressure, DC voltage, and substrate temperature, but also depended on the structure of the magnetron sputtering gun. A variety of magnet configurations have been tested. We have identified several magnet arrangements with which high quality YBCO thin films could be obtained. With suitable magnet arrangements and optimal sputtering parameters, large area and high quality YBCO thin films could be fabricated with T/sub c/s about 90 K, J/sub c/s of 10/sup 6/ A/cm/sup 2/ at 77 K and zero field, and the transition width less than 1 K. >

In situ growth of epitaxial YBa2Cu3O7 thin films by on-axis unbalanced direct current magnetron sputtering

Superconducting YBa2Cu3O7−x thin films are prepared in situ by on-axis dc magnetron sputtering from a single stoichiometric target. The magnetron uses an unbalanced magnetic field configuration to eliminate resputtering effects, and high quality thin films on MgO (100) substrates are realized with excellent reproducibility. The target is sputtered in Ar/O2 mixture at a fixed partial pressure ratio pAr/pO2= 15:1. We report on the growth and properties of films deposited (a) as a function of the total sputtering pressure pt (1–100 Pa) at fixed substrate heater temperature Ts=740 °C, and (b) as a function of Ts (600–860 °C) at fixed pt=42 Pa. Epitaxial c-axis thin films are obtained over a wide range of deposition conditions (Ts≥700 °C, pt≥30 Pa). These films have superconducting transition temperatures Tc=86–90 K, critical current densities Jc77≥106 A cm−2, and resistance ratios R300/R100=2.0–3.1.

On-axis dc magnetron sputtering of large area high quality YBa2Cu3O7 superconducting thin films

It is demonstrated by our experiment that using the in situ dc magnetron sputtering method, it is possible to prepare high quality YBa2Cu3O7 (YBCO) thin films with substrates facing the region of plasma ring. The effect of oxygen resputtering can be greatly reduced with a high argon-oxygen working gas ratio and a large target to substrate distance. It is shown that high quality YBCO thin films of more than 60 mm in diameter, that is about the same size of the diameter of the YBCO target, can be prepared with this process. The thin films were characterized by x-ray diffractometry, and the critical temperatures were determined by both resistive and ac susceptibility techniques.

低酸素圧下で作製したＹ‐Ｂａ‐Ｃｕ‐Ｏスパッタ薄膜の超伝導臨界温度と組成および格子定数

Superconducting Y-Ba-Cu-O films have been prepared by on-axis DC magnetron sputtering from single sintered targets with various compositions, and relationships of transition temperature Tc to film composition and c-axis lattice parameter c0 have been examined. Films with zero-resistance transition temperature Tc, end exceeding 85K are easily obtained using Ba-poorer targets than stoichiometry under the conditions of lower oxygen pressures, 3-10mTorr, than those reported by other investigators. The Tc and c0 of these films strongly depend on X-ray intensity ratio Cu/Ba which has been obtained directly by EDX and is related to film composition ratio. As the Cu/Ba ratio is decreased from an optimum value, Tc values rapidly decrease and c0 values increases. Moreover, the c0 values are influenced by X-ray intensity ratio Ba/Y. Although some films with higher Ba/Y ratios have c0 values larger than 11.82A (=tetragonal lattice parameter of bulk), they still show superconductivity. Their dependence of Tc on c0 is clearly different from that usually reported for bulk samples and post-annealed films. On the basis of these results, effects of oxygen pressure during sputter-deposition on Tc, film composition and c0 are discussed.