Effect of Ar+ ion sputtering on the electronic transport of MgB2 surface

Abstract Scanning tunneling microscopy and spectroscopy (STM/STS) experiments on a high-density sintered MgB 2 surface were performed at 4.2 K, using a low-temperature STM. For a 20-min Ar + ion sputtered MgB 2 surface, a double-gap structure with gap values of Δ L =9.5 meV and Δ S =4.0 meV was clearly observed in the local tunneling spectra, exhibiting the BCS-shaped characteristic with a metallic background. But for a 2-h Ar + ion sputtered surface, the observed current–voltage characteristics of the MgB 2 surface show metallic electronic transport behavior. In an attempt to clarify the effect of Ar + ion sputtering on the electronic transport, the MgB 2 surface was characterized by Auger electron spectroscopy (AES). The compositional changes of the MgB 2 surface were investigated in real time during the course of Ar + ion sputtering. The detailed compositional analysis of the MgB 2 surface may help to elucidate the various electronic transport behavior observed in surface-sensitive STS measurements.