Electrical conductivity of NbN–SiO2 films obtained by ammonolysis of Nb2O5–SiO2 sol–gel derived coatings

Structure and electrical properties of nitrided NbN–TiN sol–gel derived films

“…Such type of behavior has been also observed in some non-metallic (in the sense that their resistance increases strongly with the decreasing temperature) NbN [12] and Al [18] cermets. This dependence has been also observed in NbN-SiO 2 samples obtained after ammonolysis of sol-gel derived films [19]. Exemplary results for NbN-TiN samples are shown in Fig.…”

Superconducting properties of an NbN–SiO2 disordered system obtained by ammonolysis of NbN–SiO2 sol–gel derived coatings

“…The formation of Josephson junctions between NbN grains could have been blocked by non-superconducting phases, which may be present in the samples. The presence of Nb-O and Nb-O-N bonds in nitrided samples has been observed in XPS results [9].…”

“…The conductivity mechanisms of these samples may be explained using the model proposed by Lee and Ramakrishnan for weakly disordered systems [8]. The results of applying this model to non-superconducting NbN-SiO 2 samples were described in [9]. The superconducting transition was not observed in the examined samples, not even for the silica-free sample (x = 100).…”

XAFS investigations of nitrided NbN–SiO2 sol–gel derived films

“…Nitridation was carried out in a silica glass tube under NH 3 gas flow (4 l/h) at a heating rate of 1°C/min, up to a temperature of 1200°C, after which the samples were held isothermally at this temperature for 1 h. Following that, the samples were cooled under NH 3 gas flux. The structure of the samples was examined by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) measurements [3,4]. The measurements of resistivity as a function of temperature were performed with a DC technique in a standard four-terminal configuration [3,5].…”

“…The films exhibit interesting electrical properties. Firstly, the 2D-3D crossover (typical of weakly disordered systems) is observed in DC electrical conductivity data at about 30 K [3]. Secondly, superconducting properties strongly depend on the NbN/SiO 2 molar ratio (the superconducting transition is not observed in NbN films and a small addition of SiO 2 is sufficient to improve the superconducting properties) and on the film thickness [4].…”