Local anodic oxidation of superconducting NbN thin films by an atomic force microscope

A local anodic oxidation technique has been applied to create oxidized nanowires on superconducting NbN thin films using an atomic force microscope (AFM) with a conductive probe. The AFM surface topography shows that both the width and height of the oxidized nanowires increase with increasing applied probe voltage under a certain relative humidity and a probe scan rate. The resistances of the NbN microbridges with and without an oxidized nanowire crossing were measured, and the results indicate that the oxidized nanowires with height of more than 8 nm are fully oxidized. The R-T and I-V characteristics of the NbN microbridges with the oxide wire of less than 8 nm were also obtained and analyzed. Methods for fabricating devices such as superconducting single photon detectors and superconducting hot electron bolometer mixers using this technology are discussed.