| 1. |
- Kapran, Olena M., et al.
(författare)
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Crossover between short- and long-range proximity effects in superconductor/ferromagnet/superconductor junctions with Ni-based ferromagnets
- 2021
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Ingår i: Physical Review B. - : American Physical Society (APS). - 2469-9950 .- 2469-9969. ; 103:9
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Tidskriftsartikel (refereegranskat)abstract
- We study superconductor/ferromagnet/superconductor junctions with CuNi, PtNi, or Ni interlayers. Remarkably, we observe that supercurrents through Ni can be significantly larger than through diluted alloys. The phenomenon is attributed to the dirtiness of disordered alloys leading to a short coherence length despite a small exchange energy. To the contrary, pure Ni is clean resulting in a coherence length as long as in a normal metal. Analysis of temperature dependencies of critical currents reveals a crossover from short (dirty) to long (clean) range proximity effects in Pt1-xNix with increasing Ni concentration. Our results point out that structural properties of a ferromagnet play a crucial role for the proximity effect and indicate that conventional strong-but-clean ferromagnets can be advantageously used in superconducting spintronic devices.
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| 2. |
- Iovan, A., et al.
(författare)
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Diode effect in asymmetric double-tunnel barriers with single-metal nanoclusters
- 2006
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 88:16
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Tidskriftsartikel (refereegranskat)abstract
- Asymmetric double-tunnel barriers with the center electrode being a metal cluster in the quantum regime are studied. The zero dimensionality of the clusters used and the associated quantized energy spectra are manifest in well-defined steps in the current-voltage characteristic. Record high current rectification ratios of similar to 10(4) for tunneling through such clusters are demonstrated at room temperature. We are able to account for all of the experimentally observed features by modeling our double-barrier structures using a combination of discrete states and charging effects for tunneling through quantum dots.
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| 3. |
- Iovan, Adrian, et al.
(författare)
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NbN thin films grown on silicon by molecular beam epitaxy for superconducting detectors
- 2023
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 123:25
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Tidskriftsartikel (refereegranskat)abstract
- Superconducting nanowire single photon detectors (SNSPDs) made with thin NbN films can reach high performances. While sputtering has been the deposition method of choice, here, we show that ammonia-molecular beam epitaxy (NH3-MBE) can produce pertinent epitaxial cubic NbN thin films on silicon substrates using an AlN buffer. Despite granular morphology and a high density of grain boundaries as well as the presence of rotational twins, Tc = 12.7 K for a 5.6 nm thick film and saturation of internal detection efficiency up to 850 nm are achieved. Morphology and stoichiometry as well as strain have a strong impact on the detector properties, highlighting the importance of a precise control of the growth parameters. These results pave the way for high fabrication yield of SNSPDs on large-scale silicon wafers using epitaxial NbN thin films grown by MBE.
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| 4. |
- Iovan, A., et al.
(författare)
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Rectification of current for tunneling through metallic nano-particles
- 2006
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 99:8
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Tidskriftsartikel (refereegranskat)abstract
- Double tunnel barrier structures were obtained by using a scanning tunneling microscope and samples composed of metallic nanoparticles deposited onto an oxidized bottom electrode. The nanoparticles were formed by evaporating subpercolation thin metallic layers. Due to the small size of the particles their energy spectrum is discrete, which is evidenced by the measured quantized current-voltage characteristics. Current rectification ratios of 100-1000 for tunneling through such quantum dots are demonstrated at room temperature.
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| 5. |
- Iovan, Adrian, et al.
(författare)
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Spin diode based on Fe/MgO double tunnel junction
- 2008
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Ingår i: Nano letters (Print). - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 8:3, s. 805-809
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate a spin diode consisting of a semiconductor-free nanoscale Fe/MgO-based double tunnel junction. The device exhibits a near perfect spin-valve effect combined with a strong diode effect. The mechanism consistent with our data is resonant tunneling through discrete states in the middle ferromagnetic layer sandwiched by tunnel barriers of different spin-dependent transparency. The observed magnetoresistance is a record high > 1000%, essentially making the structure an on/off spin switch. This, combined with the strong diode effect, similar to 100, demonstrates a new device principle, promising for memory and reprogrammable logic applications.
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| 6. |
- Korenivski, Vladislav, et al.
(författare)
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Stimulated emission of radiation using spin-population inversion in metals
- 2013
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Ingår i: Proceedings - 2013 International Kharkov Symposium on Physics and Engineering of Microwaves, Millimeter and Submillimeter Waves, MSMW 2013. - : IEEE. - 9781479910663 ; , s. 259-261
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Konferensbidrag (refereegranskat)abstract
- The discovery of masers and lasers has led to major breakthroughs in science and technology. Later important developments include compact semiconductor lasers for visible to near-infrared and quantum-cascade lasers for far-infrared to THz radiation.
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