We report on a controlled method to fabricate in-situ a superconducting (SC) nanostructure at the apex of the standard W tip of a Scanning Tunnelling Microscope (STM) by pulsing the tunnelling voltage on a graphene covered metal surface. We have characterized the SC properties of the resulting tip as a function of temperature and magnetic field, obtaining a transition temperature of 3.3 K and a critical field well above 3T. The SC nanotip is robust, stable, and achieves atomic resolution. The non-SC tip can be easily recovered by controlled voltage pulsing on a clean metal surface. The present result should be taken into account when studying zero-bias features like Kondo resonances or superconductivity on graphene-based systems by means of STM using tungsten tips.
@article{arxiv.1906.02932,
title = {Robust, switchable, C-related, Superconducting Nanostructure at the Apex of a W tip},
author = {C. G. AYani and F. Calleja and P. Casado and A. Norris and J. J. Navarro and M. Garnica and M. Acebron and D. Granados and A. L. Vazquez de Parga and J. G. Rodrigo and R. Miranda},
journal= {arXiv preprint arXiv:1906.02932},
year = {2019}
}