Nanofabrication
SA Cybart, R Bali, G Hlawacek, F Röder, J Fassbender
Helium Ion Microscopy, 415-445
The ability of gas field ion sources (GFIS) to produce controllable inert gas ion beams with atomic
level precision opens up new applications in nanoscale direct-write material modification. Two
areas where this has recently been demonstrated is focused helium ion beam production of high-transiti
on temperature (high-T C) superconductor electronics and magnetic spin transport devices.
SA Cybart, TJ Wong, EY Cho, JW Beeman, CS Yung, BH Moeckly, RC Dynes
Applied Physics Letters 104 (18), 182604
Magnetic field sensors based on two-dimensional arrays of superconducting quantum
interference devices were constructed from magnesium diboride thin films. Each array
contained over 30 000 Josephson junctions fabricated by ion damage of 30 nm weak links
through an implant mask defined by nano-lithography. Current-biased devices exhibited
very large voltage modulation as a function of magnetic field, with amplitudes as high as 8
mV.
SA Cybart, EY Cho, TJ Wong, VN Glyantsev, JU Huh, CS Yung, BH Moeckly, JW Beeman, E Ulin-Avila, SM Wu, RC Dynes
Applied Physics Letters 104 (6), 062601
We have fabricated and tested two-dimensional arrays of YBa2 Cu 3O7− δ superconducting
quantum interference devices. The arrays contain over 36 000 nano Josephson junctions
fabricated from ion irradiation of YBa2 Cu 3O7− δ through narrow slits in a resist-mask that
was patterned with electron beam lithography and reactive ion etching. Measurements of
current-biased arrays in magnetic field exhibit large voltage modulations as high as 30 mV.
SA Cybart, P Roediger, E Ulin-Avila, SM Wu, TJ Wong, RC Dynes
Journal of Vacuum Science & Technology B 31 (1), 010604
We demonstrate a low pressure reactive ion etching process capable of patterning nanometer scale angled sidewalls and three dimensional structures in photoresist. At low pressure the plasma has a large dark space region where the etchant ions have very large highly-directional mean free paths. Mounting the sample entirely within this dark space allows for etching at angles relative to the cathode with minimal undercutting, resulting in high-aspect ratio nanometer scale angled features. By reversing the initial angle and performing a second etch we create three-dimensional mask profiles.
SA Cybart, SM Anton, SM Wu, J Clarke, RC Dynes
Nano letters 9 (10), 3581-3585
Very large scale integration of Josephson junctions in a two-dimensional series−parallel array has been achieved by ion irradiating a YBa2Cu3O7−δ film through slits in a nanofabricated mask created with electron beam lithography and reactive ion etching. The mask consisted of 15820 high aspect ratio (20:1), 35 nm wide slits that restricted the irradiation in the film below to form Josephson junctions. Characterizing each parallel segment k, containing 28 junctions, with a single critical current Ick we found a standard deviation in Ick of about 16%.
SA Cybart, K Chen, Y Cui, Q Li, XX Xi, RC Dynes
Applied physics letters 88, 012509
We have fabricated planar thin-film MgB2Josephson junctions and 20-junction series arrays using 200-keV ion implantation and electron-beam lithography. Resistively shunted junctionI-V characteristics were observed in the temperature range of 34–38K. The ac Josephson effect was observed and flat giant Shapiro steps in arrays suggest good junction uniformity with a small spread in junction parameters. The temperature dependence of the critical current suggests that the nature of the interface between the superconductor and normal region can be described using a soft boundary proximity effect coupling model. We believe that the higher operating temperature and close spacing of these junctions make them promising candidates for quantum voltage standards and other devices.
K Chen, SA Cybart, RC Dynes
Journal of Vacuum Science & Technology B 23 (5), 1887-1890
The electron proximity effect makes it difficult to fabricate uniform patterns at nanometer scale. A simple scheme to correct the effect is presented and applied to fabricate 100 parallel lines spaced at 250 and 500 nm on a photoresist mask using electron beamlithography. The width of each line is less than 100 nm and nearly identical. Two rectangles adjacent to the first and the last lines were exposed with a dosage below the threshold that the electron beam resist requires for development. The linewidths are more uniform with this proximity effect correction than without it. This technique has been used to fabricate ion-damaged high temperature superconducting Josephson junction arrays.