We report on the superconducting properties of molybdenum nitride thin films grown by reactive DC sputtering at room temperature with a N 2 :Ar mixture. Thin films grown using 5 % N 2 concentration display T c = 8 K, which is gradually reduced and abruptly disappears for 40 % N 2 concentration. This suppression can be associated with changes in the nitrogen stoichiometry from Mo 2 N to MoN. Our results provide an effective and simple path to prepare Mo 2 N x thin films with tunable T c , which is relevant for the investigation of the fundamental properties and for technological applications.

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).

Total L and Li subshell X-ray production cross-sections were determined experimentally for Mo by proton impact.

We report the influence of crystalline defects introduced by 6 MeV 16

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We report on the synthesis and characterization of nanocrystalline δ-MoN by crystallization of amorphous thin films grown on (100) Si by reactive sputtering at room temperature.Films with chemical composition MoN were grown using a deposition pressure of 5mTorr with a reactive mixture of Ar/(Ar+N 2 )=0.5. The as-grown films display mostly amorphous structure. Nanocrystalline δ-MoN phase is obtained after annealing at temperatures above 600 °C. The superconducting critical temperature T c depends on film thickness. Thick films (170 nm) annealed at 700 °C for 30 min display a T c = 11.2 K (close to the one reported for bulk specimens: 13 K), which is gradually suppressed to 7.2 K for 40 nm thick δ-MoN films. Our results provide a simple method to synthesize superconducting nitride thin films on silicon wafers with T c above the ones observed for conventional superconductors such as Nb.

Abstract.We report on the critical current density Jc and the vortex dynamics of pristine and 3 MeV proton irradiated (cumulative dose equal to 2×10 16 cm −2 ) β-FeSe single crystals.We also analyze a remarkable dependence of the superconducting critical temperature Tc, Jc and the flux creep rate S on the sample mounting method. Free-standing crystals present Tc=8.4(1)K, which increases to 10.5(1)K when they are fixed to the sample holder by embedding them with GE-7031 varnish. On the other hand, the irradiation has a marginal effect on Tc. The pinning scenario can be ascribed to twin boundaries and random point defects. We find that the main effect of irradiation is to increase the density of random point defects, while the embedding mainly reduces the density of twin boundaries. Pristine and irradiated crystals present two outstanding features in the temperature dependence of the flux creep rate: S(T ) presents large values at low temperatures, which can be attributed to small pinning energies, and a plateau at intermediate temperatures, which can be associated with glassy relaxation. From Maley analysis, we observe that the characteristic glassy exponent µ changes from ∼ 1.7 to 1.35-1.4 after proton irradiation.

The sulfur K x-ray emission was studied in pure sulfur, anhydrite (CaSO 4) and sphalerite (ZnS) samples. The ionizations were induced by electron impact and the spectra were recorded with a wavelength dispersive spectrometer. The spectral processing was performed through a methodology based on the optimization of atomic and experimental parameters. Energies and intensities of diagram and satellite lines were determined for a set of transitions in the Kα and Kβ groups. The lines studied include Kα 22