Ultralow 1/f Noise in a Heterostructure of Superconducting Epitaxial Cobalt-Disilicide Thin Film on Silicon

TL;DR

This study demonstrates that epitaxial CoSi₂/Si heterostructures exhibit extremely low 1/f noise levels at cryogenic temperatures, promising for quantum computing applications due to their stability and low noise characteristics.

Contribution

The paper reports the discovery of ultralow 1/f noise in epitaxial CoSi₂/Si heterostructures, significantly lower than conventional materials, supported by detailed microscopy and noise analysis.

Findings

1/f noise level is about 100 times lower than aluminum films.

Low noise attributed to limited dangling bonds at the interface.

Potential for use in quiet qubits and scalable quantum circuits.

Abstract

High-precision resistance noise measurements indicate that the epitaxial CoSi$_2$/Si hetero-structures at 150 K and 2 K (slightly above its superconducting transition temperature $T_c$ of 1.54 K) exhibit an unusually low 1/f noise level in the frequency range of 0.008-0.2 Hz. This corresponds to an upper limit of Hooge constant $\gamma \leq 3 \times 10^{-6}$, about 100 times lower than that of single-crystalline aluminum films on SiO$_2$ capped Si substrates. Supported by high-resolution cross-sectional transmission electron microscopy studies, our analysis reveals that the 1/f 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 CoSi$_2$/Si(100) interface, giving limited trapping-detrapping centers for localized charges. With its excellent normal-state properties, CoSi$_2$ has been used in silicon-based integrated circuits for decades. The intrinsically low noise properties discovered in this work could be utilized for developing quiet qubits and scalable superconducting circuits for future quantum computing.