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arXiv · 2306.09566

Investigation of the deposition of $\alpha$-tantalum (110) films on a-plane sapphire substrate by molecular beam epitaxy for superconducting circuit

Haolin Jia·Boyi Zhou·Tao Wang·Yanfu Wu·lina Yang·Zengqian Ding·Shuming Li·Kanglin Xiong·Jiagui Feng
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Abstract

Polycrystalline {\alpha}-tantalum (110) films deposited on c-plane sapphire substrate by sputtering are used in superconducting qubits nowadays. However, these films always occasionally form other structures, such as {\alpha}-tantalum (111) grains and \b{eta}-tantalum grains. To improve the film quality, we investigate the growth of {\alpha}-tantalum (110) films on a-plane sapphire substrate under varying conditions by molecular beam epitaxy technology. The optimized {\alpha}-tantalum (110) film is single crystal, with a smooth surface and atomically flat metal-substrate interface. The film with thickness of 30 nm shows a Tc of 4.12K and a high residual resistance ratio of 9.53. The quarter wavelength coplanar waveguide resonators fabricated with the 150 nm optimized {\alpha}-tantalum (110) film, exhibits intrinsic quality factor of over one million under single photon excitation at millikelvin temperature.

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Haolin Jia, Boyi Zhou, Tao Wang, Yanfu Wu, lina Yang, Zengqian Ding, Shuming Li, Kanglin Xiong, Jiagui Feng. 2023-06-16. Investigation of the deposition of $\alpha$-tantalum (110) films on a-plane sapphire substrate by molecular beam epitaxy for superconducting circuit. https://doi.org/10.1116/6.0002886

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