| 1. |
- Anyfantis, Dimitrios, I, et al.
(författare)
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Unexpected Development of Perpendicular Magnetic Anisotropy in Ni/NiO Multilayers After Mild Thermal Annealing
- 2019
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Ingår i: IEEE Magnetics Letters. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 1949-307X .- 1949-3088. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- We report on the significant enhancement of perpendicular magnetic anisotropy of Ni/NiO multilayers after mild annealing up to 90 min at 250 degrees C. Transmission electron microscopy shows that after annealing, a partial crystallization of the initially amorphous NiO layers occurs. This turns out to be the source of the anisotropy enhancement. Magnetic measurements reveal that even multilayers with Ni layers as thick as 7 nm, which in the as-deposited state showed in-plane anisotropy with square hysteresis loops, show reduced in-plane remanence after thermal treatment. Hysteresis loops recorded with the field in the normal-to-film-plane direction provide evidence for perpendicular magnetic anisotropy with up and down magnetic domains at remanence. A plot of effective uniaxial magnetic anisotropy constant times individual Ni layer thickness as a function of individual Ni layer thickness shows a large change in the slope of the data attributed to a drastic change of volume anisotropy. Surface anisotropy showed a small decrease because of some layer roughening introduced by annealing.
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| 2. |
- Vallejo-Perez, Monica, et al.
(författare)
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Optimization of GOPS-Based Functionalization Process and Impact of Aptamer Grafting on the Si Nanonet FET Electrical Properties as First Steps towards Thrombin Electrical Detection
- 2020
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Ingår i: Nanomaterials. - : MDPI. - 2079-4991. ; 10:9
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Tidskriftsartikel (refereegranskat)abstract
- Field effect transistors (FETs) based on networks of randomly oriented Si nanowires (Si nanonets or Si NNs) were biomodified using Thrombin Binding Aptamer (TBA-15) probe with the final objective to sense thrombin by electrical detection. In this work, the impact of the biomodification on the electrical properties of the Si NN-FETs was studied. First, the results that were obtained for the optimization of the (3-Glycidyloxypropyl)trimethoxysilane (GOPS)-based biofunctionalization process by using UV radiation are reported. The biofunctionalized devices were analyzed by atomic force microscopy (AFM) and scanning transmission electron microscopy (STEM), proving that TBA-15 probes were properly grafted on the surface of the devices, and by means of epifluorescence microscopy it was possible to demonstrate that the UV-assisted GOPS-based functionalization notably improves the homogeneity of the surface DNA distribution. Later, the electrical characteristics of 80 devices were analyzed before and after the biofunctionalization process, indicating that the results are highly dependent on the experimental protocol. We found that the TBA-15 hybridization capacity with its complementary strand is time dependent and that the transfer characteristics of the Si NN-FETs obtained after the TBA-15 probe grafting are also time dependent. These results help to elucidate and define the experimental precautions that must be taken into account to fabricate reproducible devices.
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