Polishing of YBa2Cu3O7−yby He‐ion etching

Clean polishing is performed by helium‐ion etching on a surface of high‐Tc YBa2Cu3O7−y. Based on a knock‐on cascade model, the decrease of surface roughness is discussed. A rate process of etching is applied for the surface roughness of the high‐Tc YBa2Cu3O7−y.