School of Information Technology and Electrical Engineering, The University of Queensland, Brisbane, QLD 4072, Australia.
School of Mathematics and Physics, The University of Queensland, Brisbane, QLD 4072, Australia.
J Phys Chem Lett. 2023 May 25;14(20):4892-4900. doi: 10.1021/acs.jpclett.3c00850. Epub 2023 May 18.
Superconducting circuits are among the most advanced quantum computing technologies; however, their performance is limited by losses found in surface oxides and disordered materials. In this work, we demonstrate the identification and spatial localization of a near-field signature of loss centers on tantalum films using terahertz scattering-type scanning near-field optical microscopy. By utilizing terahertz nanospectroscopy, we observe a localized excess vibrational mode around 0.5 THz and identify this resonance as the boson peak, a signature of amorphous materials. Grazing-incidence wide-angle X-ray scattering reveals that oxides on freshly solvent-cleaned samples are amorphous, whereas crystalline phases emerge after aging in air. Through nanoscale localization of defect centers, our findings provide valuable insights for the optimization of fabrication procedures for new low-loss superconducting circuits.
超导电路是最先进的量子计算技术之一；然而，它们的性能受到表面氧化物和无序材料中损耗的限制。在这项工作中，我们使用太赫兹散射型扫描近场光学显微镜演示了在钽薄膜上对损耗中心的近场特征的识别和空间定位。通过利用太赫兹纳米光谱学，我们观察到大约 0.5 THz 处的局部过振动模式，并将该共振标识为玻色峰，这是无定形材料的特征。掠入射广角 X 射线散射表明，新鲜溶剂清洗样品上的氧化物是无定形的，而在空气中老化后则出现晶相。通过缺陷中心的纳米尺度定位，我们的发现为新的低损耗超导电路的制造工艺优化提供了有价值的见解。
