Surface morphology of oxidized and ion-etched silicon by scanning tunneling microscopy

The surface morphology of silicon (100) wafers has been measured by scanning tunneling microscopy. Samples which were bombarded with low-energy argon ions are found to have an average root-mean-square roughness of 4.0 Å, and the surfaces are covered with characteristic 50-Å-diam hillocks. The roughness of nonbombarded (control) samples is observed to be 1.8 Å, and this roughness arises in part from disorder at the interface between a native oxide and the silicon substrate.