AI 中文总结
研究钽氮化物在超导量子比特中的应用，通过在硅衬底上设置TaN和Ta薄膜组合，探讨其内部品质因数Qi性能，发现添加Ta缓冲层可显著提高Qi值，支持控制衬底-金属界面关乎超导量子比特电路性能的假设。
AI 中文摘要
钽已被证明是一种有前途的超导量子比特材料，但其氮化物受到的关注较少。氮化钽具有多种化学计量比，导致多种材料特性，可在超导量子比特中用作多种用途。本研究探讨了硅衬底上超导TaN和Ta薄膜组合的内部品质因数Qi性能。发现独立TaN薄膜在单光子 regime 下100mK时Qi值约为1.5x10^5 。在几纳米厚的TaN种子层上生长的Ta制成的谐振器性能大致相同，但在硅衬底和TaN种子层之间添加几纳米厚的Ta缓冲层可将Qi显著提高到5.9x10^5 。透射电子显微镜测量表明TaN-Si界面存在氮积累和结构无序，引入Ta缓冲层可抑制这种界面改性。观察到的谐振器性能改善与界面相关的两能级系统损耗的降低一致，有力支持了控制衬底-金属界面对于超导量子比特电路性能至关重要的假设。
英文摘要
Tantalum has been demonstrated as a promising material for superconducting qubits. However, comparatively little attention has been given to its nitrides. Tantalum nitride exhibits a range of stoichiometries, resulting in a variety of material properties, including both superconducting and non-superconducting phases. Owing to this versatility, tantalum nitrides can serve multiple purposes in superconducting qubits: as seed layers for alpha-Ta growth, as a superconducting base material and as a non-superconducting barrier in the Josephson junction. In this study, we explore the performance of superconducting TaN and Ta thin film combinations on silicon substrates in terms of internal quality factor Qi. We find that standalone TaN films exhibit Qi values of about 1.5x10^5 at 100mK in the single-photon regime. Surprisingly, a resonator made from Ta grown on a few-nanometers-thick TaN seed layer yields largely the same performance. However, adding an additional, few-nanometers-thick Ta buffer layer between the Si substrate and this TaN seed layer enhances Qi significantly up to 5.9x10^5. Supporting transmission electron microscopy measurements reveal nitrogen accumulation and structural disorder at the TaN-Si interface, while this interfacial modification is suppressed when the Ta buffer layer is introduced. The observed improvement in resonator performance is consistent with a reduction of interface-related two-level system losses and strongly supports the hypothesis that controlling the substrate-metal interface is pivotal for the performance of superconducting qubit circuitry.
