Epitaxial Tantalum for Superconducting Usage
Chih-Yao Shih1*, Ping-Lien Lee1, Shao-Shiun Liao1,2, Huang Hsin Chuan1, Rui-Qian Liu3, Yi-Kai Kao1, Shao-Chi Hong1, Sheng-Shiuan Yeh3, Wen-Hao Chang1,2,4
1Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu, Taiwan
2Research Center for Critical Issues, Academia Sinica, Tainan, Taiwan
3International College of Semiconductor Technology, National Yang Ming Chiao Tung University, Hsinchu, Taiwan
4Research Center for Applied Sciences, Academia Sinica, Taipei, Taiwan
* Presenter:Chih-Yao Shih, email:henryshih.sc11@nycu.edu.tw
With the advancement of quantum processors, high-quality superconducting material has played a critical role in achieving longer relaxation times (T1). Conventional in-plane polycrystalline Tantalum (Ta) films deposited on c-plane sapphire reduce the residual resistivity ratio (RRR) and introduces the additional losses through grain-boundary oxide. In this work, we demonstrate the epitaxial Ta(110) and Ta(111) films on a-plane and c-plane sapphire, respectively. The surface morphology and grain orientation were characterized using atomic force microscopy (AFM), while crystallinity and epitaxial relationships were examined through x-ray diffraction (XRD) θ–2θ and φ scans. Electron backscatter diffraction (EBSD) was employed to determine grain size distributions and crystal orientations. Our results reveal large-scale grains and clear epitaxial alignment. To evaluate the superconducting performance, RRR is extracted. Furthermore, planar resonators and transmon qubits were fabricated, and their intrinsic quality factors (Qᵢ) and energy relaxation times (T₁) were measured. These findings confirm that epitaxial Ta(110) and Ta(111) films exhibit superior superconducting properties compared to conventional in-plane polycrystalline Ta, thereby providing a promising pathway toward large-scale integration of superconducting quantum processors.


Keywords: Fault-tolerant quantum computing, Wafer-scale, Superconducting thin films, Tantalum