High performance NbN nanowire superconducting single photon detectors fabricated on MgO substrates

We demonstrate high-performance nanowire superconducting single photon detectors (SSPDs) on ultrathin NbN films grown at a temperature compatible with monolithic integration. NbN films ranging from 150nm to 3nm in thickness were deposited by dc magnetron sputtering on MgO substrates at 400C. The superconducting properties of NbN films were optimized studying the effects of deposition parameters on film properties. SSPDs were fabricated on high quality NbN films of different thickness (7 to 3nm) deposited under optimal conditions. Electrical and optical characterizations were performed on the SSPDs. The highest QE value measured at 4.2K is 20% at 1300nm

Features relaxation grain and defect structure of nanostructured alloy V-Cr-ZrO2 alloy

The study of parameters of the defect structure near the recrystallization temperature of the dispersion-strengthened alloy V-Cr-ZrO2 after deformation by torsion under pressure is presented

Corrosion and mechanical properties of duplex-treated 301 stainless steel

ABSTRACT: Plasma nitriding is a widely used technique for increasing the surface hardness of stainless steels, and consequently, for improving their tribological properties. It is also used to create an interface between soft stainless steel substrates and hard coatings to improve adhesion. This paper reports on the mechanical and corrosion properties of AISI301 stainless steel (SS) after a duplex treatment consisting of plasma nitriding followed by deposition of Cr bond coat and CrSiN top layer by magnetron sputtering. Mechanical properties of the deposited films, such as hardness (H) and reduced Young's modulus (Er), were measured using depth-sensing indentation. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) were carried out to evaluate resistance to localized and to general corrosion, respectively. The corrosion behavior has been correlated with the microstructure and composition of the surface layers, determined by complementary characterization techniques, including XRD, SEM, and EDS. The CrSiN layers exhibited an H value of 24 GPa, whereas the nitrided layer was shown to present a gradual increase of H from 5 GPa (in the nitrogen-free SS matrix) to almost 14 GPa at the surface. The electrochemical measurements showed that the nitriding temperature is a critical parameter for defining the corrosion properties of the duplex-treated SS. At a relatively high temperature (723 K), the nitrided layer exhibited poor corrosion resistance due to the precipitation of chromium nitride compounds and the depletion of Cr in the iron matrix. This, in turn, leads to poor corrosion performance of the duplex-treated SS since pores and defects in the CrSiN film were potential sites for pitting. At relatively low nitriding temperature (573 K), the nitrided interface exhibited excellent corrosion resistance due to the formation of a compound-free diffusion layer. This is found to favor passivation of the material at the electrode/electrolyte interface of the duplex-treated SS

Tribological properties of CrSiN-coated 301 stainless steel under wet and dry conditions

ABSTRACT: The tribological properties of CrSiN coatings were investigated under dry and wet conditions. CrSiN films (2 μm thick) were deposited on 301 stainless steel substrates by dual magnetron sputtering, using a chromium interface layer (500 nm thick) on the top of plasma nitrided surface. The morphology and microstructure of the CrSiN films were examined by SEM, EDS and X-ray diffractometry. Dry and wet wear tests were performed using a linear reciprocating ball-on-flat tribometer. In wet condition, the contact was immersed in NaCl 1 wt.%, and the sliding wear tests were performed at open circuit potential (OCP), and under cathodic and anodic conditions. CrSiN films were found to exhibit excellent wear resistance under dry condition: the films had no tendency to delaminate after 1800 cycles of sliding wear under 1.6 GPa Hertzian stress. However, under wet condition, the wear resistance was rather poor: the films detached from the substrate at smaller contact pressures (1.2 GPa). It was demonstrated that the corrosion reactions at the electrode/electrolyte interface were the reason for the degradation of the tribological properties of these films; in the absence of corrosion reactions (under cathodic polarization), CrSiN coatings were found to resist much better sliding wear

Structural, tribo-mechanical, and thermal properties of NbAlN coatings with various Al contents deposited by DC reactive magnetron sputtering

DC reactive magnetron sputtered Nb2AlyNx coatings with various Al contents (y/(y + z)) ranging from 0 to 0.75 were deposited using different ratios of the currents applied to the Al and Nb targets in order to systematically control their chemical composition and crystalline structure, and to enhance their mechanical, tribological and thermal stability performance. The film microstructure and properties were assessed by various complementary techniques such as electron probe microanalysis, X-ray diffraction, nanoindentation, ball-on-disc test, and scanning electron microscopy. It was found that the solubility limit of Al in the NbN lattice is in the range 0.44 0.44, the hardness of the Nb2AlyNx coatings is reduced due to the formation of the soft hexagonal MN phase. In addition, the coatings exhibit interesting tribological properties: the coefficient of friction is in the range of 0.74 to 0.85, and wear rate is in the range of 4.8-9.1 x 10(-6) mm(3)/ Nm. Thermal stability shows a dependence on the Al content; specifically, the Nb0.33Al0.17N0.50 coating was found to be thermally stable up to 700 degrees C