Angle‐resolved XPS studies of oxides at NbN, NbC, and Nb surfaces

Darlinski, A.; Halbritter, J.

doi:10.1002/sia.740100502

Cited by 210 publications

(108 citation statements)

References 47 publications

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“…Essentially, this means that the oxide overlayer is not perfectly flat. This type of serration was also observed by Darlinski and Halbritter in their ARXPS studies of Nb and NbC [35].…”

Section: Surface Characterization Of Coatingssupporting

confidence: 80%

“…Lorentzian-Gaussian functions were used to represent Nb 2 O 5 at 207.4 eV, Nb-C at 204.2 eV, and Nb-Nb at 202.5 eV. The fits were in good agreement with the cited studies [34,35] except for the present addition of a strong asymmetric tail modifier for the conducting compounds Nb-C and Nb-Nb. The reason for the modifier is to account for Nb3d asymmetry and limit the number of model bands [36].…”

Section: Surface Characterization Of Coatingssupporting

confidence: 68%

“…However, they also stated that the percentage of the suboxides was very small and that these bonds did not appear as separate peaks. Oxycarbide formation (i.e., carbide with oxygen in interstitial sites) could not be resolved according to the Nb3d XPS study [35]. Correspondingly, we were also unable to experimentally resolve any peaks due to suboxides or oxycarbide.…”

Section: Surface Characterization Of Coatingsmentioning

confidence: 78%

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Passive films on nanocomposite carbide coatings for electrical contact applications

et al. 2017

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Nanocomposite transition metal carbide/amorphous carbon coatings (Me-C/a-C) deposited by magnetron sputtering have excellent electrical contact properties. The contact resistance can be as low as that of noble metal coatings, although it is known to vary by several orders of magnitude depending on the deposition conditions. We have investigated a nanocrystalline niobium carbide/ amorphous carbon (NbC x /a-C:H) model system aiming to clarify factors affecting the contact resistance for this group of contact materials. For the first time, the surface chemistry is systematically studied, by angle-resolved X-ray photoelectron spectroscopy, and in extension how it can explain the contact resistance. The coatings presented a mean oxide thickness of about 1 nm, which could be grown to 8 nm by annealing. Remarkably, the contact resistances covered four orders of magnitude and were found to be exponentially dependent on the mean oxide thickness. Moreover, there is an optimum in the amount of a-C:H phase where the contact resistance drops very significantly and it is thus important to not only consider the mean oxide thickness. To explain the results, a model relying on surface chemistry and contact mechanics is presented. The lowest contact resistance of a nanocomposite matched that of a gold coating at 1 N load (vs. gold), and such performance has previously not been demonstrated for similar nanocomposite materials, highlighting their useful properties for electrical contact applications.

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“…Essentially, this means that the oxide overlayer is not perfectly flat. This type of serration was also observed by Darlinski and Halbritter in their ARXPS studies of Nb and NbC [35].…”

Section: Surface Characterization Of Coatingssupporting

confidence: 80%

Section: Surface Characterization Of Coatingssupporting

confidence: 68%

Section: Surface Characterization Of Coatingsmentioning

confidence: 78%

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Passive films on nanocomposite carbide coatings for electrical contact applications

et al. 2017

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“…All the Bi 2 Se 3 -NbN bilayers in the present study were obtained using an "in-situ" process where both the 3 nm thick NbN film and the 10 nm thick Bi 2 Se 3 cap layer were prepared in the same deposition run without breaking the vacuum. This kept the interface between the NbN and Bi 2 Se 3 layers protected against contamination and oxidation which occur if the NbN surface is exposed to air [17,35]. Transport measurements were done using an array of 40 gold coated spring loaded spherical tips for the 4-probe measurements on 10 different locations on the wafer (Ci with i = 1-10, 4 contacts for each location).…”

Section: Methodsmentioning

confidence: 99%

Magnetoresistance, Gating and Proximity Effects in Ultrathin NbN-Bi2Se3 Bilayers

Koren

2017

Condensed Matter

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Ultrathin Bi 2 Se 3 -NbN bilayers comprise a simple proximity system of a topological insulator and an s-wave superconductor for studying gating effects on topological superconductors. Here we report on 3 nm thick NbN layers of weakly connected superconducting islands, overlayed with 10 nm thick Bi 2 Se 3 film which facilitates enhanced proximity coupling between them. Resistance versus temperature of the most resistive bilayers shows insulating behavior but with signs of superconductivity. We measured the magnetoresistance (MR) of these bilayers versus temperature with and without a magnetic field H normal to the wafer (MR = [R(H) − R(0)]/{[R(H) + R(0)]/2}), and under three electric gate-fields of 0 and ±2 MV/cm. The MR results showed a complex set of gate sensitive peaks which extended up to about 30 K. The results are discussed in terms of vortex physics, and the origin of the different MR peaks is identified and attributed to flux-flow MR in the isolated NbN islands and the different proximity regions in the Bi 2 Se 3 cap-layer. The dominant MR peak was found to be consistent with enhanced proximity induced superconductivity in the topological edge currents regions. The high temperature MR data suggest a possible pseudogap phase or a highly extended fluctuation regime.

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“…Oxide films of niobium and its compounds are covered by a great amount of works, i.e. [2][3][4][5]. However, there are no works covering layer phase profiling of oxidized thin films of niobium compounds.…”

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confidence: 99%

An XPS method for layer profiling of NbN thin films

et al. 2016

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Abstract. Layer chemical and phase profiling of niobium nitride thin films on a silicon substrate oxidized on air was performed with the help of a method designed by us. The method includes: a new method of background subtraction of multiple inelastically scattered photoelectrons considering depth inhomogeneity of electron inelastic scattering; a new method of photoelectron line decomposition into component peaks considering physical nature of different decomposition parameters; joint solution of the background subtraction and photoelectron line decomposition problems; control of line decomposition accuracy with the help of a suggested performance criterion; calculation of layer thicknesses for a multilayer target using a simple formula.The interest in thin films of niobium and its compounds is caused by their superconductive properties used in cryogenic electronic instrumentation. For example, niobium nitride thin films are attracting rising attention in recent submillimeter and THz receiver research [1]. As an oxidation result of films of niobium or its compounds (originally homogeneous) multilayer and multiphase films are built. The superconductive properties of niobium compounds become worse with increase of surface niobium oxide layer thickness. Oxide films of niobium and its compounds are covered by a great amount of works, i.e. [2][3][4][5]. However, there are no works covering layer phase profiling of oxidized thin films of niobium compounds.This work presents layer phase profiling of oxidized thin films of niobium nitride on a silicon substrate by the means of XPS. Thin niobium nitride films were sputtered onto a silicon substrate by the magnetron method. The films were oxidized during unload from the vacuum chamber. X-ray photoemission spectra were obtained with the electron-ion spectroscopy module based on the platform Nanofab 25 (NT-MDT). In the analytical chamber, an ultrahigh oil-free vacuum about 10 -8 Pa was achieved. The spectra were recorded with an electrostatic semi-spherical energy analyzer SPECS Phoibos 225.Layer profiling on the base of XPS spectra of multilayer multicomponent thin films interpretation is a complex inverse problem with a lot of unknown parameters. For correct solution of this problem new methods and approaches designed by the authors are suggested:

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Angle‐resolved XPS studies of oxides at NbN, NbC, and Nb surfaces

Cited by 210 publications

References 47 publications

Passive films on nanocomposite carbide coatings for electrical contact applications

Passive films on nanocomposite carbide coatings for electrical contact applications

Magnetoresistance, Gating and Proximity Effects in Ultrathin NbN-Bi2Se3 Bilayers

An XPS method for layer profiling of NbN thin films

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