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

摘要

High-precision resistance noise measurements indicate that the epitaxialCoSi$_2$/Si hetero-structures at 150 K and 2 K (slightly above itssuperconducting transition temperature $T_c$ of 1.54 K) exhibit an unusuallylow 1/f noise level in the frequency range of 0.008-0.2 Hz. This corresponds toan upper limit of Hooge constant $\gamma \leq 3 \times 10^{-6}$, about 100times lower than that of single-crystalline aluminum films on SiO$_2$ capped Sisubstrates. Supported by high-resolution cross-sectional transmission electronmicroscopy studies, our analysis reveals that the 1/f noise is dominated byexcess interfacial Si atoms and their dimer reconstruction induced fluctuators.Unbonded orbitals (i.e., dangling bonds) on excess Si atoms are intrinsicallyrare at the epitaxial CoSi$_2$/Si(100) interface, giving limitedtrapping-detrapping centers for localized charges. With its excellentnormal-state properties, CoSi$_2$ has been used in silicon-based integratedcircuits for decades. The intrinsically low noise properties discovered in thiswork could be utilized for developing quiet qubits and scalable superconductingcircuits for future quantum computing.