Law Ka Ming, Budhathoki Sujan, Ranjit Smriti, Martin Franziska, Thind Arashdeep S, Mishra Rohan, Hauser Adam J
Department of Physics and Astronomy, The University of Alabama, Tuscaloosa, AL, 35487, USA.
Institute of Materials Science and Engineering, Washington University in St. Louis, St. Louis, MO, 63130, USA.
Sci Rep. 2020 Oct 27;10(1):18357. doi: 10.1038/s41598-020-74981-2.
Superconducting resonators with high quality factors have been fabricated from aluminum films, suggesting potential applications in quantum computing. Improvement of thin film crystal quality and removal of void and pinhole defects will improve quality factor and functional yield. Epitaxial aluminum films with superb crystallinity, high surface smoothness, and interface sharpness were successfully grown on the c-plane of sapphire using sputter beam epitaxy. This study assesses the effects of varying substrate preparation conditions and growth and prebake temperatures on crystallinity and smoothness. X-ray diffraction and reflectivity measurements yield extensive Laue oscillations and Kiessig thickness fringes for films grown at 200 °C under 15 mTorr Ar, indicating excellent crystallinity and surface smoothness; moreover, an additional substrate preparation procedure which involves (1) a modified substrate cleaning procedure and (2) prebake at 700 °C in 20 mTorr O is shown by atomic force microscopy to yield nearly pinhole-free film growth while maintaining epitaxy and high crystal quality. The modified cleaning procedure is environmentally friendly and eliminates the acid etch steps common to conventional sapphire preparation, suggesting potential industrial application both on standard epitaxial and patterned surface sapphire substrates.
具有高品质因数的超导谐振器已由铝膜制成，这表明其在量子计算中有潜在应用。提高薄膜晶体质量以及消除空洞和针孔缺陷将提高品质因数和功能成品率。利用溅射束外延技术，在蓝宝石的c平面上成功生长出了具有优异结晶度、高表面平整度和界面清晰度的外延铝膜。本研究评估了不同的衬底制备条件、生长温度和预烘烤温度对结晶度和平整度的影响。对于在15毫托氩气环境下于200℃生长的薄膜，X射线衍射和反射率测量产生了广泛的劳厄振荡和基斯西格厚度条纹，表明其具有优异的结晶度和表面平整度；此外，原子力显微镜显示，一种额外的衬底制备程序，该程序包括(1)一种改进的衬底清洁程序和(2)在20毫托氧气中于700℃进行预烘烤，能在保持外延和高晶体质量的同时实现几乎无针孔的薄膜生长。改进后的清洁程序对环境友好，并且消除了传统蓝宝石制备中常见的酸蚀步骤，这表明其在标准外延和图案化表面蓝宝石衬底上均具有潜在的工业应用价值。
