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Granular Ti1− xNb xN thin films, 0 ≤ x ≤ 0.77, were deposited on borosilicate glass substrates by RF magnetron sputtering. Conductive-atomic force microscopy (C-AFM) was employed to study the local electrical transport properties of Ti1− xNb xN thin films. Topography images reveal that the grain size in the films increased from 30 to 90 nm, as x increased from 0 to 0.77. For a constant applied voltage of 1 V, the local leakage current in Ti1− xNb xN films increased with an increase in x value. The measured current is in the order of nA and its flow is filamentary in nature. Current-voltage characteristics measured at different locations on each current image revealed that the local resistance drastically decreased with an increase in Nb concentration. Electron-grain boundary scattering and the presence of native oxide states are responsible for the increase in the local electrical resistance of the films. [ABSTRACT FROM AUTHOR]

The optical reflectance, dielectric functions and phonon vibrational modes of TiNbN (0≤ x≤0.77) thin films are reported. Films of 500-nm thickness were deposited on 316LN nuclear grade stainless steel substrates by radio-frequency magnetron sputtering. The reflectance spectra of the films, in the energy range 1.5 to 5.5 eV, are fitted using the Drude-Lorentz model as the response of one Drude parameter and four Lorentz oscillators. It is demonstrated that the properties studied are dependent on Nb concentration, x, and exhibit a behavior transition threshold at x=0.5. The optical properties studied are closer to TiN for x<0.5 and resemble NbN for x>0.5. For example, the films showed a minimum in reflectance at ∼2.33 eV for values of x up to 0.5, corresponding to the Ti-N charge transfer band. Increase in Nb concentration beyond 0.5 caused a large shift in this energy to 3.2 eV, corresponding to the Nb-N charge transfer excitation. Similarly, the real part of the dielectric function is characterized by a screened plasma energy of 2.25 eV for values of x<0.5 (∼TiN) and 3.25±0.2 eV for x>0.5 (∼NbN). The energy at which the loss function reaches a peak value increases linearly for values of x from 0 to 0.41 and decreases very drastically for x>0.5. Phonon-vibrational modes of TiNbN thin films studied by Raman spectroscopy show that Nb substitution in TiN results in first-order Raman scattering. The single-phonon acoustical peak at 270 cm of TiN shifted to 265 cm for x=0.77, while the two-phonon acoustical peak of TiN at 620 cm shifted to 630 cm for the same value of x. The reasons for the existence of a behavior transition threshold in Nb concentration are discussed. [ABSTRACT FROM AUTHOR]

The structure, mechanical, optical, and electrical properties of TiNbN thin films, 0 ≤ x ≤ 1, are reported. The films were deposited onto polycrystalline nuclear grade 316LN stainless steel substrate by radio frequency reactive magnetron sputtering in 100% N plasma. X-ray diffraction results revealed that Nb is soluble in TiN up to x = 0.77. From x = 0.26 to x = 0.77, these films stabilized in rock salt structure with (111) orientation. The hardness and Young's modulus increased, whereas electrical resistivity decreased with an increase in the Nb concentration in the films. The highest value of hardness and Young's modulus were 31 and 320 GPa, respectively, for x = 0.77, at which the value of the lowest resistivity of 56 μΩ-cm was measured. The films showed a broad reflectance band, with a minimum in reflectance that shifted to shorter wavelengths as a function of increasing x. The reflectance band extended from the ultraviolet (~250 nm) to the visible region (~750 nm) and the position of the reflectance shifted from 2.33 to 3 eV with an increase in x from 0 to 0.77. [ABSTRACT FROM AUTHOR]

Abstract: Simultaneous local current and topography measurements were made on the surface of titanium nitride thin films by conductive-atomic force microscopy (C-AFM). Two compositions, stoichiometric TiN and sub-stoichiometric TiN0.76 were investigated. Local variation of current at grain and grain boundaries was examined. The current flow is filamentary in nature, with the number of percolation paths being smaller for sub-stoichiometric titanium nitride. Current-voltage characteristics of stoichiometric TiN reveal that the grain interiors are electrically conductive, while in sub-stoichiometric TiN0.76 thin film, grains are electrically resistive, i.e., a potential barrier to electron transport exists at the junction between the grain and the grain boundary in sub-stoichiometric TiN0.76. Therefore, electron transport in this film is due to tunneling through the junction, which leads to increased resistivity. The total resistance of the samples measured using the four probe technique is 1 and 400kΩ for TiN and TiN0.76 respectively. In both type of compounds the grain and grain boundary resistances are of the order of MΩ. The grain and grain boundaries are connected in a manner that causes the total resistivity to be lower than the local resistivity. [Copyright &y& Elsevier]

Abstract: Using RF reactive magnetron sputtering process in a 100% nitrogen atmosphere, TiN x thin films were deposited on a quartz substrate. The crystal structure and optical properties of the as-deposited thin films, as a function of substrate temperature, were studied. From room temperature till 600°C, with increasing temperature, the crystal structure changed from tetragonal to cubic, with ‘x’ in TiN x increasing with the substrate temperature. In the entire temperature range x was less than 1. Simultaneously, the optical plasma band of the film shifted from the ultra-violet region having energy of 4.83eV to the visible region corresponding to energy of 2.47eV. The width of the transmittance band in the visible range varied with temperature between 460nm and 620nm. All the films exhibited a PL (photoluminescent) single band in the middle of the visible region. [ABSTRACT FROM AUTHOR]