Healing effect of controlled anti-electromigration on conventional and high-Tc superconducting nanowires

At the present time, electron beam lithography (EBL) is considered as the reference technique for nanoscale patterning. However, making nanostructures below the sub-10 nm scale is still challenging due to broadening effects (forward electron scattering, backscattering, electrostatic charging…), and requires strong investment in terms of cost for state-of-the-art EBL systems. In this sense, alternative methods are continuously explored in order to make such nanofabrication easily reachable.
A promising approach consists of inducing atomic diffusion by a large current density. This phenomenon, called electromigration (EM), and well known since the 60’s as a failure mechanism in metallic interconnections [1], still attracts interests from scientists and engineers for its great potential for fabrication of microstructures and for its reversibility character [2, 3].

In this work, we show that the combination of electromigration and anti-electromigration allows the precise tuning of superconducting properties of Al nanoconstrictions and we also observe the reversibility of electromigration failure for this material (see Fig. 1). The same process has been applied on Nb, leading to a more irreversible process, and La2 xCexCuO4.
For the latter material, we show that selective migration of oxygen atoms and the consequent doping modification induces a transition from a superconducting state to an insulating state in a reversible way [4].

We also discussed the possibility to enhance the electromigration technique by replacing the complex feedback control by a technique of electropulsing. These researches have direct practical impact as a method to explore the dependence of the characteristic parameters on the exact oxygen content and pave the way for a reversible control of local properties of nanowires.