Thickness dependence of the superconducting properties of γ- Mo2N thin films on Si (001) grown by DC sputtering at room temperature

Abstract

We study the crystalline structure and superconducting properties of -Mo 2 N thin films grown by reactive DC sputtering on AlN buffered Si (001) substrates. The films were grown at room temperature. The microstructure of the films, which was studied by X-ray diffraction and transmission electron microscopy, shows a single-phase with nanometric grains textured along the (200) direction. The films exhibit highly uniform thickness in areas larger than 20 x 20 m 2. The superconducting critical temperature T c is suppressed from 6.6 K to ≈ 3.0 K when the thickness decreases from 40 nm to 5 nm. The residual-resistivity ratio is slightly smaller than 1 for all the films, which indicates very short electronic mean free path. The films are in the superconducting dirty limit with upper critical field H c2 (0) ≈ 12 T for films with thickness of 40 nm, and 9 T for films with thickness of 10 nm. In addition, from the critical current densities J c in the vortex-free state, we estimate a penetration depth (0) ≈ (800  50) nm and a thermodynamic critical field H c (0) = (500  80 Oe).

Synthesis of nanocrystalline δ-MoN by thermal annealing of amorphous thin films grown on (100) Si by reactive sputtering at room temperature

“…The total pressure at the chamber was 5 mTorr. AlN buffer layers were grown using a N 2 /(Ar+N 2 )= 0.2 mixture [17]. The deposition rate for MoN using a N 2 /(Ar+N 2 )= 0.5 mixture was ≈ 17 nm / min.…”

“…An outstanding feature for γ-Mo 2 N and δ-MoN is that sharp superconducting transitions have been observed for epitaxial and polycrystalline thin films [14,15,16]. Moreover, superconductivity has been observed for films with thicknesses of a few nanometers [14,15,17]. Recently, we have reported that the chemical concentration and T c for Mo-N thin films grown at room temperature by reactive sputtering can be modified by changing the Ar:N 2 ratio [18].…”

Compositional effects on the electrical properties of extremely disordered molybdenum oxynitrides thin films

“…The surface cleaning was performed with Ar + sputtering (2 kV). The pristine films display a component at binding energy (BE) ≈ 232.7 eV related to superficial MoO 3 that is removed during the sputtering process[29].Figure 4shows the XPS spectra in the Mo3d region for cleaned [MoN 10 O 0 ], [MoN 8 O 2 ], [MoN 5 O 5 ] and [MoN 0 O 10 ]. The results can be divided into nitrides and oxides.…”

Superconducting MoN thin films prepared by DC reactive magnetron sputtering for nanowire single-photon detectors

“…In our experiments, the 5 nm films had significantly lower TC than the films of 18 nm. The decrease in TC with decreasing thickness of MoN has been discussed in other works [23]. Thin films of less than 10 nm are preferable for superconducting nanowire single-photon detectors.…”

“…We have studied the electrical and superconducting properties of sub-20 nm MoN thin films depending on various deposition conditions, including the substrate, nitrogen partial pressure, temperature, discharge current, and post-deposition annealing. To our knowledge, there are only a couple of other reports of superconducting MoN films of less than 20 nm [23,24], which are of special interest for detector applications. We show that meander-shaped SNSPDs based on 5 nm MoN films demonstrate saturated internal detection efficiency at telecom wavelength.…”