Regensburg 2019 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 62: Direct-Write Nanofabrication and Applications III
(Electron Beam Induced Processing) (joint session DS/TT)
TT 62.7: Vortrag
Donnerstag, 4. April 2019, 17:15–17:30, H32
Crystalline NbC superconducting nanowires by direct-writing — •Fabrizio Porrati1, Sven Barth2, Roland Sachser1, Oleksandr Dobrovolskiy1, Anja Seybert3, Achilleas Frangakis3, and Michael Huth1 — 1Goethe-University, Institut of Physics, Frankfurt a. M. — 2TU Wien, Institute of Materials Chemistry — 3Goethe-University, Buchmann Institute
We present a comparative study of planar nanowires and 3D free-standing nanowires grown by focused electron- / ion (Ga+)-beam induced deposition (FEBID/FIBID) using the novel precursor Nb(NMe2)3(N-t-Bu). FEBID planar nanowires contain 67at%C, 22at%N and 11at%Nb; FIBID planar nanowires 42.9at%C, 12.9at%N, 15.5at%Ga and 28.7at%Nb. TEM analysis shows that FEBID samples are amorphous, while FIBID samples are made of fcc NbC polycrystals, with grains of 15-20nm diameter and lattice constant 4.47Å. The RT electrical resistivity is ≈104 µΩcm and 550 µΩcm for FEBID and FIBID samples. Conductivity vs. temperature measurements show that the FEBID nanowires are insulating, following a variable-range-hopping behavior. FIBID nanowires, with RRR=0.87, become superconducting at TC=5.0 K. TC can be slightly tuned either by an electron irradiation treatment (TC=5.4, for 20nC/*m2) or by changing the width of the nanowires (TC=4.3-6.4, for w=50-1000 nm). 3D free-standing nanowires were grown by FIBID. TEM experiments confirm a fcc NbC microstructure. The electrical measurements of these nanowires, with RRR=1.02, show a superconducting transition with TC 11K, a value close to the value of bulk NbC.