| 1. |
- Lubenschenko, A., et al.
(författare)
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Air-Oxidation of Nb Nano-Films
- 2018
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Ingår i: Semiconductors. - 1090-6479 .- 1063-7826. ; 52:5, s. 678-682
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Tidskriftsartikel (refereegranskat)abstract
- X-ray photoelectron spectroscopy (XPS) depth chemical and phase profiling of air-oxidized niobium nanofilms has been performed. It is found that oxide layer thicknesses depend on the initial thickness of the niobium nanofilm. The increase in thickness of the initial Nb nano-layer is due to increase in thickness of an oxidized layer.
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| 2. |
- Lubenschenko, A., et al.
(författare)
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Controlled Ultra-Thin Suboxide Films Generation in Metal-Oxide Systems by Ar + Ion Irradiation
- 2020
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Ingår i: Journal of Physics: Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 1695:1
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Konferensbidrag (refereegranskat)abstract
- A method of controlled generation of metal suboxide films is proposed, basing on low-current ion sputtering of native oxides of ultra-thin metallic films and XPS chemical and phase depth profiling. Niobium suboxide ultra-thin films are generated and controlled using this approach.
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| 3. |
- Lubenschenko, A., et al.
(författare)
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Interface Layers of Niobium Nitride Thin Films
- 2019
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Ingår i: Journal of Physics: Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 1410:1
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Konferensbidrag (refereegranskat)abstract
- Intermediate layers formed by thin NbN films are studied. A surface phase of NbN different from the bulk one under the oxide layer and a layer consisting of NbNx-SiOy between the film and the substrate are found.
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| 4. |
- Lukiantsev, Denis S., et al.
(författare)
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The Formation of nanosuboxide layers in the oxide of niobium in low-power ion beam of argon
- 2021
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Ingår i: Proceedings of the 3rd 2021 International Youth Conference on Radio Electronics, Electrical and Power Engineering, REEPE 2021.
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Konferensbidrag (refereegranskat)abstract
- This paper presents the results of chemical, quantitative, and layer-by-layer phase analysis of a 10 nm thick niobium thin film created by magnetron sputtering and subsequently oxidized in air. The analysis was performed before and after long-term delicate modification by argon ions by X-ray photoelectron spectroscopy using numerical simulation of the interaction of ion beams with the target surface in the SRIM software package. At different durations of low-current ion sputtering of niobium oxide, the formation of metastable stoichiometric and non-stoichiometric nanosuboxide layers of various thicknesses, as well as their sputtering, was found. The study shows that it is possible to create the necessary nanosuboxide layers, the structure of which is determined by the performance of functional devices.
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| 5. |
- Krause, Sascha, 1989, et al.
(författare)
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Ambient temperature growth of mono- and polycrystalline NbN nanofilms and their rigorous composition and surface analysis
- 2015
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Ingår i: European Conference on Applied Superconductivity.
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Konferensbidrag (refereegranskat)abstract
- This paper reflects on the rigorous investigation of high-quality 5nm thin NbN films which were deposited by means of reactive DC magnetron sputtering at ambient temperatures. Monocrystalline NbN films have been epitaxially grown onto hexagonal GaN buffer-layers (0002) and showing a distinct, low defect interface as confirmed from HRTEM. The critical temperature (Tc) of those films reached 10.4K. Furthermore, a poly-crystalline structure was observed on films grown onto Si (100) substrates, exhibiting a Tc of 8.1K albeit a narrow transition from the normal to the superconducting state. The deposition at ambient temperatures offers major advantages from a processing point of view and motivates the in-depth characterization and comparison of present films with high quality films grown at elevated temperatures. X-ray photoelectron spectroscopy and reflected electron energy loss spectroscopy verified that the composition of NbN did not differ irrespectively of applied substrate heating. Moreover, the native oxide layer at the surface of NbN has been identified as NbO2 and thus is in contrast to the Nb2O5, usually being formed at the surface of Nb when exposed to air. These findings are of great significance since it was proven the possibility of growing epitaxial NbN onto GaN buffer layer in the absence of high temperatures hence paving the way to employ NbN in more advanced fabrication processes involving a higher degree of complexity. Particularly low-noise THz receiver could benefit from the eased integration of e.g IF circuitry or general multi-layer structures which take advantage of lift-off techniques.
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| 6. |
- Krause, Sascha, 1989, et al.
(författare)
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Ambient temperature growth of mono- and polycrystalline NbN nanofilms and their surface and composition analysis
- 2016
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Ingår i: IEEE Transactions on Applied Superconductivity. - : Institute of Electrical and Electronics Engineers (IEEE). - 1558-2515 .- 1051-8223. ; 26:3
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents the studies of high-quality 5 nmthin NbN films deposited by means of reactive DC magnetronsputtering at room temperature. The deposition withoutsubstrate heating offers major advantages from a processingpoint of view and motivates the extensive composition- andsurface characterization and comparison of the present filmswith high quality films grown at elevated temperatures.Monocrystalline NbN films have been epitaxially grown ontohexagonal GaN buffer-layers (0002) and show a distinct, lowdefect interface as confirmed by High-Resolution TEM. Thecritical temperature Tc of films on the GaN buffer-layer reached10.4 K. Furthermore, a poly-crystalline structure was observedon films grown onto Si (100) substrates, exhibiting a Tc of 8.1 Kalbeit a narrow transition from the normal to thesuperconducting state. X-ray photoelectron spectroscopy andreflected electron energy loss spectroscopy verified that thecomposition of NbN was identical irrespectively of appliedsubstrate heating. Moreover, the native oxide layer at the surfaceof NbN has been identified as NbO2 and thus, is in contrast to theNb2O5, usually claimed to be formed at the surface of Nb whenexposed to air. These findings are of significance since it wasproven the possibility of growing epitaxial NbN onto GaN bufferlayer in the absence of high temperatures hence paving the wayto employ NbN in more advanced fabrication processes involvinga higher degree of complexity. The eased integration andemployment of lift-off techniques could, in particular, lead toimproved performance of cryogenic ultra-sensitive terahertzelectronics.
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| 7. |
- Lubenschenko, A., et al.
(författare)
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Native oxide on ultra-thin NbN films
- 2019
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Ingår i: ISSTT 2019 - 30th International Symposium on Space Terahertz Technology, Proceedings Book. ; , s. 95-98
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Konferensbidrag (refereegranskat)abstract
- We report study of native oxide formation over NbN ultra-thin films. With a help of XPS, chemical and phase depth profiles of NbN film of 5 nm and 10 nm thickness exposed to room air for more than a month were recorded. The surface of those films were sputtered with Ar+ ions and consequently oxidized in room air for another few days. It was found that an intermediate layer of NbNx was formed between the niobium oxide layer and original NbN material.
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| 8. |
- Lubenschenko, A., et al.
(författare)
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XPS Study of Niobium and Niobium-Nitride Nanofilms
- 2018
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Ingår i: Journal of Surface Investigation. - 1819-7094 .- 1027-4510. ; 12:4, s. 692-700
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Tidskriftsartikel (refereegranskat)abstract
- A new, XPS-based approach to quantitative and nondestructive determination of the chemical and phase layer composition of multicomponent multilayer films is proposed. It includes a new method for subtracting the background of repeatedly inelastically scattered photoelectrons, taking into account the inhomogeneity of inelastic scattering over depth; a new way of decomposing a photoelectron line into component peaks, taking into account the physical nature of various decomposition parameters; solution of the problem of subtracting the background and decomposing the photoelectron line simultaneously; and determination of the thickness of the layers of a multilayer target using a simple equation. The phase-layer composition of nanoscale Nb and NbN films is determined, and the thicknesses of these layers are calculated.
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