Surface Morphology of Step Edge on MgO Single Crystal Substrate for Josephson Junction

We have fabricated and compared the surface morphology of the step-edge on the MgO substrate by using Ar ion beam milling (IBM) and wet chemical etching methods. To characterize the surface morphology and step height of the fabricated step edge on MgO substrate, SEM and AFM measurements were performed. The step height obtained using IBM and chemical etching methods were ∼220 nm and ∼500 nm, respectively. From the comparison of AFM images of the un-etched and etched regions, a very small increase in the surface roughness of the etched region was observed for the IBM etched substrate; whereas for the chemical etched substrate the roughness of both un-etched and etched regions have increased. It was observed that the step-edge fabricated by IBM techniques has sharp step edge and better surface morphology as compared to step edge fabricated by chemical etching process.