Ion-beam Assisted Deposition of MgO with in situ RHEED Monitoring to Control Bi-axial Texture
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Ion-beam Assisted Deposition of MgO with in situ RHEED Monitoring to Control Bi-axial Texture James R. Groves, Paul N. Arendt, Stephen R. Foltyn, Quanxi Jia, Raymond F. DePaula, Paul C. Dowden, Harriet Kung, Terry G. Holesinger, Liliana Stan, Luke A. Emmert, and Eric J. Peterson Materials Science Division, Los Alamos National Laboratory Los Alamos, NM, 87545 ABSTRACT We have studied the growth of magnesium oxide using ion-beam assisted deposition (IBAD) to achieve (100) oriented, bi-axially textured films with low mosaic spread, for film thicknesses of 10 nm on silicon substrates. We have refined the process by using reflected high-energy electron diffraction (RHEED) to monitor the growth of IBAD MgO films and found that the diffracted intensity can be used to determine (and ultimately control) final in-plane texture of the film. Here we present results on our work to develop the use of real-time RHEED monitoring to deposit well-oriented IBAD MgO films. The results have been corroborated with extensive grazing-incidence X-ray diffraction (GID). Results of these analyses have allowed us to deposit films on metallic substrates with in-plane mosaic spread less than 7°.
INTRODUCTION There is great interest in the high temperature superconductor (HTS) coated conductor community to develop economically scalable processes for fabricating bi-axially textured templates on which high quality YBa2Cu3O7-δ (YBCO) can be heteroepitaxially deposited. In order to achieve good superconducting properties, YBCO grains require good alignment between each other to achieve high (>1 MA/cm2) critical current densities (Jc)[1]. The two competitive processes to produce the bi-axial texture required by YBCO have been Roll-Assisted BI-axial Texturing of Substrates (RABiTS)[2] and Ion-Beam Assisted Deposition (IBAD)[3]. Our group has focused on the latter technique and expended much effort to deposit yttria-stabilized zirconia (YSZ) with IBAD for coating lengths on technically important metal substrates. This effort has resulted in the development of a process, coupled with pulsed laser deposited (PLD) YBCO, that has produced meter lengths of second generation superconducting wire with critical current densities over 1 MA/cm2 and critical currents over 100 A[4]. One of the criticisms of the IBAD YSZ process has been that the length of time required to deposit the material with sufficient in-plane texture for high quality YBCO is too long. In order to develop texture, YSZ requires a thickness between 0.5 and 1 µm to achieve a ∆φ (or full-width at half-maximum of the φ-scan peak) better than 12°. This translates to an IBAD deposition time of ~20 hours per meter of tape[5]. The viability of this process is questionable for cost effective, industrial fabrication. Wang et al. showed that magnesium oxide (MgO) could be deposited with the IBAD process and produce a film with in-plane texture comparable to YSZ that was only 10 nm[6]. This translates to a process which is ~100 times faster than IBAD YSZ. We have continued to develop this process for us
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