Abstract
We have formed AlNx tunnel barriers in Nb Josephson junctions using a nitrogen ion beam operated at low energy (<150 eV). Independent control of ion energy and dose allowed for the exploration of a wide parameter space in which devices were fabricated with good quality and reproducibility with J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> < 10 kA/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . The junctions were stable up to temperatures of at least 200degC, implying that the nitrogen atoms are strongly bound and do not desorb as gaseous molecular N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> . Large-area uniformity was also investigated where the spatial variation in ion current density was correlated with J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> . This technique could be applied to form other metal nitrides at room temperature for device applications where a high degree of control is desired.
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