论文标题
应力诱导的NB薄膜中的欧米茄相变，用于超导Qubit
Stress-induced omega phase transition in Nb thin films for superconducting qubits
论文作者
论文摘要
我们报告了使用透射电子显微镜（TEM）沉积的NB薄膜中欧米茄相形成的观察。我们假设，这种相转化为欧米茄相，具有BCC相的六边形结构，以及{111} <112>机械双胞胎的形成是由NB薄膜中的内部应力引起的。就侧向尺寸而言，NB的欧米茄相的大小范围为10至100 nm，这与NB（〜40 nm）的相干长度相当。就总体体积分数而言，〜1卷，NB晶粒的百分比显示了这一欧米茄阶段。我们还发现，在大谷物NB样品中未观察到NB中的欧米茄相，这表明可以通过降低晶界密度来抑制相变，这可以作为该系统中应变和错位的来源。目前的发现可能表明，由于NB薄膜的内部应力，NB薄膜易于欧米茄相变。最后，我们讨论了欧米茄阶段对NB薄膜超导性能的影响，并讨论减轻其形成的途径。
We report the observation of omega phase formation in Nb thin films deposited by high-power impulse magnetron sputtering (HiPIMS) for superconducting qubits using transmission electron microscopy (TEM). We hypothesize that this phase transformation to the omega phase with hexagonal structure from bcc phase as well as the formation of {111}<112> mechanical twins is induced by internal stress in the Nb thin films. In terms of lateral dimensions, the size of the omega phase of Nb range from 10 to 100 nm, which is comparable to the coherence length of Nb (~40 nm). In terms of overall volume fraction, ~1 vol.% of the Nb grains exhibit this omega phase. We also find that the omega phase in Nb is not observed in large grain Nb samples, suggesting that the phase transition can be suppressed through reducing the grain boundary density, which may serve as a source of strain and dislocations in this system. The current finding may indicate that the Nb thin film is prone to the omega phase transition due to the internal stress in the Nb thin film. We conclude by discussing effects of the omega phase on the superconducting properties of Nb thin films and discussing pathways to mitigate their formation.
