Deposition and characterization of few-nanometers-thick superconducting Mo–Re films

Abstract

We report on the fabrication and investigation of few-nanometers-thick superconducting molybdenum-rhenium (Mo-Re) films intended for use in nanowire single-photon superconducting detectors (SSPDs). Mo-Re films were deposited on sapphire substrates by DC magnetron sputtering of an Mo(60)-Re(40) alloy target in an atmosphere of argon. The films 2-10 nm thick had critical temperatures (T c ) from 5.6 to 9.7 K. HRTEM (high-resolution transmission electron microscopy) analysis showed that the films had a homogeneous structure. XPS (x-ray photoelectron spectroscopy) analysis showed the Mo to Re atom ratio to be 0.575/0.425, oxygen concentration to be 10%, and concentration of other elements to be 1%.

Co-sputtered MoRe thin films for carbon nanotube growth-compatible superconducting coplanar resonators

“…Similar values have been identified in Ref. 26 as chemical shift due to the Mo-Re compound formation.…”

“…In contrast, at the Re 4f-peak neither changes in the line shape nor peak shifts are observed in the surface compared to the bulk spectrum, indicating the absence of rhenium oxides at the surface and in the bulk layers. All films examined in this work exhibit the same behavior for the rhenium peaks [25,26].…”

“…Figure 2(b) and 2(c) display details of the spectrum close to the Mo 3d-and Re 4f-peaks, referenced to the C 1s-peak. [26] The additional structure in the Mo 3d surface spectrum originates from MoO 3 and MoO 2 forming at the alloy surface [25,28]. It decreases subsequently until disappearing in the bulk where only the two Mo 3d 5/2and Mo 3d 3/2 -peaks are part of the spectrum.…”

Thickness dependent interlayer transport in vertical MoS 2 Josephson junctions

“…Here we probe the thickness dependence of interlayer electrical transport in MoS 2 flakes using the Josephson effect between two coupled molybdenum-rhenium (MoRe) superconductors. In addition to slow oxide growth of MoRe thin films [24], molybdenum itself has been shown to be an excellent contact metal for Schottky barrier-free contact to MoS 2 [25,26]. Using this alloy, we fabricate high transparency vertical junctions with 1-4 MoS 2 layers.…”

Mechanical dissipation in MoRe superconducting metal drums

“…The compatibility of MoRe with HF, oxygen plasma, and an elastic modulus of %1 GPa makes it an attractive candidate for making hybrid electromechanical devices. 20 The electrical properties of MoRe are well studied, establishing its disordered nature with a residual resistance ratio of approximately unity and a superconducting transition temperature of 9.2 K. [21][22][23][24] The electrical dissipation of such films in the microwave frequency domain has been characterized in earlier studies 25 and recent reports in coplanar waveguides. 26 Fig .…”