Nanoscopic surface modification by slow ion bombardment

We present systematic scanning tunneling microscopy (STM)/atomic-force microscopic (AFM) investigations on nanoscopic defect production at atomically clean surfaces of SiO2, Al2O3 and highly oriented pyrolytic graphite (HOPG) after bombardment by slow (impact energy less than or equal to 1.2 keV) singly and multiply charged ions under strict ultra-high vacuum (UHV) conditions. Combined STM and AFM studies show that on HOPG only electronic but no visible topographic defects are created by such ion bombardment. On the monocrystalline insulator surfaces, well-defined topographic features of typically nm extensions are produced (potential sputtering). For Al2O3 and HOPG, a clear dependence of the defect size on the projectile ion charge is demonstrated. These results are discussed in view to possible new nanoscopic surface structuring and modification methods for which the kinetic projectile energy plays a minor role only. (C) 2003 Elsevier Science B.V. All rights reserved.