Metallorganic Deposition Method Research Articles

Enhanced Pinning Properties of the Bilayers of YDy0.5Ba2Cu3O7−δ by SrZrO3 Nanoparticles through Low Fluorine Metallorganic Solution Deposition

Bilayered YDy0.5Ba2Cu3.6O7−δ superconducting films with a thickness of about 1 μ were deposited by metallorganic deposition method, an interlayer of secondary phase of SrZrO3 (SZO) and BaZrO3 (BZO) were inserted. Detailed growth mechanism studies of these structures as well as superconducting properties in different temperatures and magnetic field range (0–5 T) were investigated. Structural analysis showed that bilayer structure changed clearly the growth mechanism of YBCO. The SZO interlayer smoothens the film surface. Magnetic measurements of superconducting properties demonstrated that the critical temperature decreases slightly when both of SZO and BZO interlayer were inserted. This indicates a growing strain effect at the layer interfaces. The critical current densities as well as pining forces of bilayered YDy0.5Ba2Cu3.6O7−δ in the entire applied temperature and magnetic field range were enhanced by the insertion of SZO layer and decreased when BZO layer is introduced. The enhancement of the pinning properties is explained by the dense flux pinning in layered YDyBCO superconductors; this result may give further improvements in the current-carrying capability.

Surface Morphology and Profile Analysis for Five-Layer YBa2Cu3O7−δ Thick Films Prepared by Low-Fluorine Metallorganic Deposition

Thick YBa2Cu3O7−δ (YBCO) films grown by metallorganic deposition (MOD) are very significant for high-performance superconducting wires. In the present work, the modified MOD method with reduced fluorine content in precursor solution (namely LF-MOD in the following) is applied to prepare the YBCO films with the purpose of reducing the processing time as well as increasing thickness. Five-layer YBCO films with a thickness of more than 2.5 μm are achieved after the effect of high-temperature annealing time (ta) on the morphology and texture of YBCO films is systematically investigated. It is suggested that an annealing time as long as 6 h appears necessary to achieve a good performance for such a thick YBCO film. To understand the evolution of texture with thickness, plasma etching is employed to characterize the profile morphology at different depths inside the films, revealing the a-axis grains together with the impurity phases arising from the incomplete reaction mostly present at the top surface only.

Processing Dependence of Texture, and Critical Properties of YBa2Cu3O7−δ Films on RABiTS Substrates by a Non‐Fluorine MOD Method

YBa2Cu3O7−δ (YBCO or Y123) films on rolling‐assisted biaxially textured substrates (RABiTS) were prepared via a fluorine‐free metallorganic deposition (MOD) through spin coating, burnout, and high temperature anneal. The effects of substrate texture and surface energy of the CeO2 cap layer were investigated. Except for the commonly accepted key factors, such as the textures of substrate and buffer layers, we found some other factors, for example, the deposition temperature of the cap layer, are also critical to the epitaxial growth of Y123 phase. With the CeO2 cap layer deposited at relative high temperature of 700°C, a critical current density, Jc, over 1 MA/cm2 has been demonstrated for the first time on Ni‐RABiTS by a fluorine‐free MOD method. Whereas for samples with CeO2 cap layers deposited at a lower temperature of 600°C, even though XRD data showed a better texture on these buffer layers, texture degradations of YBCO grains under the optimized processing conditions were observed and a lower oxygen partial pressure around 40 ppm was necessary for the epitaxial growth of Y123 phase. As a result, Jc fell to 0.45 MA/cm2 at 77 K. The observed phenomena points to the change of surface energy and reactivity of the CeO2 cap layer with respect to the CeO2 deposition temperature. In this paper, the YBCO phase diagram was also summarized.

Novel approach to deposition of copper thin films by dip-coating method

The shift from aluminum to copper in the integrated circuit fabrication has received considerable attention during past decades. Copper has low electrical resistivity and good electromigration resistance. Copper also finds a place in a variety of thin film materials and is often alloyed with other elements. For example, copper/nickel multi-layers have been extensively studied in the past due to their wide range of application in magnetic devises [1–3]. Several techniques have been used to deposit metal coatings. Vapor phase techniques, such as sputtering, evaporation, and chemical vapor deposition (CVD) requires sophisticated vacuum equipment, which are costly, especially for large area and mass production. Moreover, volatile precursors, which are normally toxic and moisture sensitive are used in the CVD process. An alternative approach for depositing metal films of controlled thickness on insulator substrates (e.g. glass plate) at low temperatures is metallorganic deposition (MOD) of thin metal films by dip-coating technique. This process is very simple and does not require costly equipment. In our earlier works [4], we have demonstrated that the fabrication of nickel and cobalt films can be achieved by dip-coating process using acetolhydrazone (ALH) as a dissolving and reducing agent. However, when ALH was used to dissolve copper acetate, the formation of metallic copper in the alcoholic solution was confirmed by XRD. Therefore, the ALH is not suitable and another additive with mild reducing property such as diethanolamine (DEA) should be used. Despite the strong reducing effect that DEA has showed on lead and cadmium compounds, a stable sol could be obtained in the case of copper acetate [5, 6]. In the present study, we report on the application of MOD method to deposit copper films on glass plates and the characterization of the formed films. The dependence of the film uniformity and surface roughness on the firing temperature was investigated and discussed herein. The MOD system employed for the present work has been previously described in detail [4]. The copper solution was obtained by mixing copper acetate dihydrate, diethanolamine (DEA) in 2-propanol. The molar ratio of DEA to Cu2+ was two. The concentration of the obtained sol ranged from 0.25 to 1.5 M. The coatings were prepared on glass slides (Corning Co. # 7059) using the dip coating procedure. The thermal treatments were performed in a tube furnace under inert gas (nitrogen). The cleaned glass substrate (1 cm × 3 cm) was withdrawn at controlled speed of 2 to 6 cm/min after being immersed of in the precursor solution for 30 s. After deposition, the substrates were dried at 110 ◦C and finally the gel films were heat-treated at different temperatures (300 ◦C−600 ◦C) for 30 min in nitrogen flow. Phase evolution was characterized by XRD (X-ray diffraction, RAD 2R, Rigaku Co.), using Cu Kα radiation with a grazing incident angle of α = 2◦ and graphite as monochromator. The morphology was characterized by scanning electron microscopy (SEM, XL 30, Phillip) and AFM (atomic force microscope; Seiko Instruments Inc. SPI 3800N). The X-ray diffraction patterns of copper thin films that were fired at various temperatures are shown in Fig. 1. At 110 ◦C a diffuse XRD pattern, related to an