| 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. |
- 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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| 3. |
- 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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| 4. |
- 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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| 5. |
- Afanas'ev, Victor P., et al.
(författare)
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Study of NbN Ultra-thin Films for THz Hot-electron Bolometers
- 2014
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Ingår i: 25th International Sympsoium on Space Terahertz Technology, ISSTT 2014; Moscow; Russian Federation; 27 April 2014 through 30 April 2014. ; , s. 141-143
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Konferensbidrag (refereegranskat)abstract
- Hot-electron bolometer (HEB) mixers based on superconducting ultra-thin NbN films are largely used for THz spectroscopy for space and ground-based observations. Performance of the HEB mixers directly depends on the details of the structure and composition of thin film surface, as well as the nitrogen composition and its depth distribution. In this work, we present the study of the composition and the surface oxidation state of NbN films grown at two different temperatures and of 5 and 10 nm thickness.
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| 6. |
- Lubenchenko, Alexander, 1966, et al.
(författare)
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An XPS method for layer profiling of NbN thin films
- 2017
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Ingår i: EPJ Web of Conferences. - : EDP Sciences. - 2101-6275 .- 2100-014X. ; 132, s. Art no 03053-
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Konferensbidrag (refereegranskat)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.
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