Composition and structure of surfaces by time-of-flight scattering and recoiling spectrometry (TOF-SARS)

Time-of-flight scattering and recoiling spectrometry (TOF-SARS) was applied to characterize surface structures in order to understand the chemical and physical phenomena on various surfaces. The combination of TOF-SARS, LEED, and classical ion trajectory simulations has allowed characterization of the elemental composition in the outermost atomic layers, surface symmetry, and possible reconstruction or relaxation.; The composition and structure of the CdS{dollar}{lcub}0001{rcub}{dollar}-(1 x 1) and CdS{dollar}{lcub}000bar1{rcub}{dollar}-(1 x 1) surfaces were investigated. The termination layer of each surface was determined by grazing incidence TOF-SARS. Both (1 x 1) surfaces are bulk-terminated without any reconstruction or relaxation detected by TOF-SARS. Each surface has two domains which are rotated by 60{dollar}spcirc{dollar} from each other and there exist steps on both surfaces. The CdS{dollar}{lcub}0001{rcub}{dollar}-(1 x 1) surface is stabilized by O and H covering half a monolayer which are structurally ordered on the surface, while the O and H on the CdS{dollar}{lcub}000bar1{rcub}{dollar}-(1 x 1) stabilize the surface without ordering.; The study of GaN{dollar}{lcub}000bar1{rcub}{dollar}-(1 x 1) shows the bulk-termination of the surface with no detectable reconstruction or relaxation. The surface is terminated in a N layer with Ga in the 2{dollar}rmsp{lcub}nd{rcub}{dollar}-layer. H atoms are bound to the outermost N atoms with a coverage of {dollar}sim{dollar}3/4 monolayer and protrude outward from the surface.; The surface termination, composition and structure of the {dollar}rm Alsb2Osb3{dollar} (sapphire) were examined. The surface relaxation was studied quantitatively using classical ion trajectory simulations along with TOF-SARS. The surface undergoes {dollar}rm1sp{lcub}st{rcub}{lcub}-{rcub}2sp{lcub}nd{rcub}{dollar}-layer relaxation as large as 0.5 A from the bulk value resulting in near coplanarity of Al and O atoms.; The reconstruction of the Ni{dollar}{lcub}100{rcub}{dollar}-(2 x 2)-C surface was studied by TOF-SARS. The surface contained 80% of the (2 x 2)p4g phase and 20% of the unreconstructed (2 x 2) phase. The displacement of Ni atoms was determined by comparing the experimental and simulated results.