A study of energetic particle impacts on solid surfaces by scanning probe microscopy.

摘要

Particle-solid interactions and the modification of solid surfaces have been of scientific and technological interest for years. In this dissertation, three independent projects were performed to study energetic impacts on solid surfaces using scanning probe microscopy (SPM).; (1) Epi-ready Ge(111) and chemomechanically polished Ge(100) surfaces were implanted with 40 to 200 keV germanium (Ge), cobalt (Co), iron (Fe) ions at a dose of {dollar}5times10sp{lcub}14{rcub}{dollar} to {dollar}5times10sp{lcub}17{rcub}{dollar} ions/cm{dollar}sp2.{dollar} Cellular nanostructures were observed by scanning tunneling microscopy (STM), contact mode and tapping mode atomic force microscopy (AFM). We have shown that the appearance of columnar/granular structures in AFM images of ion bombarded nanometer cellular structures created on germanium surfaces is due to severe image distortion when the tip radius r is close to or greater than the hole radius R.; (2) Very flat {dollar}rm Insb{lcub}0.22{rcub}Gasb{lcub}0.78{rcub}As{dollar} layers grown by metalorganic vapor phase epitaxy (MOVPE) on GaAs(100) surfaces were bombarded with a low dose (10{dollar}sp{lcub}11{rcub}{dollar} ions cm{dollar}sp2){dollar} of arsenic and boron ions at 35 keV. AFM observations show craters with average diameters of 14.6 nm and 11.4 nm for As{dollar}sp+{dollar} and B{dollar}sp+{dollar} respectively and that each crater is correlated with a single ion impact. The mechanism of the formation of the craters is discussed.; (3) Highly oriented pyrolitic graphite (HOPG) was irradiated with 1.8 MeV electrons at 45{dollar}spcirc{dollar} and near grazing (86{dollar}spcirc){dollar} angles of incidence. For near grazing incidence, at a dose of {dollar}5times10sp{lcub}12{rcub}{dollar} electrons cm{dollar}sp{lcub}-2{rcub},{dollar} features of nm size are observed. These are attributed to the effects of single electron-carbon interactions in the top surface layers. At a dose of {dollar}5times10sp{lcub}14{rcub}{dollar} electrons cm{dollar}sp{lcub}-2{rcub}{dollar} (near grazing incidence) both STM and AFM observations show an anomalously large (period 2.5 to 17 nm) superperiodicity superimposed on the normal 0.246 nm atomic spacing of graphite. We propose that near grazing incidence electron irradiation causes a break-up of the surface layers into fragments, largely retaining the six-fold atomic rings, that rotate by a small angle resulting in the observed pattern by interaction with the deeper bulk-structure layers.