Ultralow 1/Ƒ Noise in Superconducting Cobalt-Disilicide Thin Films on Silicon
Shao-Pin Chiu1*, Sheng-Shiuan Yeh1, Chien-Jyun Chiou2, Yi-Chia Chou2, Juhn-Jong Lin1,2, Chang-Chyi Tsuei3
1Institute of Physics, National Chiao Tung University, Hsinchu, Taiwan
2Electrophysics Department, National Chiao Tung University, Hsinchu, Taiwan
3Thomas J. Watson Research Center, IBM, New York, USA
* presenting author:Shao-Pin Chiu, email:fluentbb@gmail.com
High-precision resistance noise measurements indicate that the epitaxial CoSi2/Si(100) heterostructures at 150 K and 2 K (slightly above its superconducting transition temperature Tc of 1.54 K) exhibit an unusually low 1/ƒ noise level in the low frequency range. This corresponds to an upper limit of Hooge constant γ ≤ 3×10-6, about 100 times lower than that of single-crystalline aluminum films on SiO2. Supported by high-resolution cross-sectional transmission electron microscopy studies, our analysis reveals that the 1/ƒ noise is dominated by excess interfacial Si atoms and their dimer reconstruction induced fluctuators. Unbonded orbitals (i.e., dangling bonds) on excess Si atoms are intrinsically rare at the epitaxial CoSi2/Si(100) interface, giving limited trapping-detrapping centers for localized charges. With its excellent normal-state properties, CoSi2 has been used in silicon-based integrated circuits for decades. The intrinsically low noise properties discovered in this work could open up a promising avenue for developing quiet qubits and scalable superconducting circuits for future quantum computing.

Keywords: Superconducting silicide/silicon heterostructure, interfacial dynamic defects, 1/f resistance noise, dimer reconstruction, two-level-system fluctuators