Nanometer-Size Monolayer and Multilayer Molecule Corrals on HOPG:  A Depth-Resolved Mechanistic Study by STM

Abstract

Surface defects on highly oriented pyrolytic graphite (HOPG) were controllably produced by bombardment with Cs+ ions at various incident kinetic energies ranging from 0.3 to 10 keV and at various dose densities. Defects in the HOPG created by Cs+ ion impacts were subsequently oxidized at 650 °C in air to produce nanometer-size monolayer and multilayer molecule corrals (pits). The controlled production of both monolayer and multilayer pits on HOPG bombarded with energetic Cs+ ions was realized and studied by scanning tunneling microscopy (STM). The pit density, pit yield, pit diameter, and pit depth can be well controlled by varying the experimental conditions. Multilayer pits can be controllably produced using Cs+ ion bombardment at higher kinetic energies, and monolayer pits can be produced using low-energy Cs+ ion bombardment. The presence of both monolayer and multilayer pits on the same HOPG samples makes the direct comparison of pit growth rates possible under exactly the same conditions. The measured depth-resolved pit growth rates for multilayer pits are in good agreement with a model of the pit growth rate “acceleration” by adjacent layers, and the separate contributions to the pit growth rate of surface diffusion and collision were extracted.

Transition metals on the (0 0 0 1) surface of graphite: Fundamental aspects of adsorption, diffusion, and morphology

“…In addition to forming clusters and islands on the terraces, metals decorate step edges on graphite surfaces [47,63,100,[104][105][106][107]. This has been shown for many metals under many different conditions.…”

“…Changes may have been made to this work since it was submitted for publications. An interesting variant of step decoration involves circular step edges, which can be formed by oxidizing graphite at elevated temperature [25,47,[104][105][106]108]. Oxidation etches away the graphite, starting at pre-existing defects and moving outward in a circle.…”

An ultrafast rechargeable aluminium-ion battery

“…8c). This superior structural integrity of PG over natural graphite during charging was attributed to the existence of covalent bonding between adjacent graphene sheets in PG 17 , which was not present in natural graphite. Using PG, which has an open, three-dimensionally-bound graphitic structure, we prevented excessive electrode expansion that would lead to electrode disintegration, while maintaining the efficient anion intercalation necessary for high performance.…”

Deposition of copper from Cu(i) and Cu(ii) precursors onto HOPG surface: Role of surface defects and choice of a precursor

“…This shape is precisely what is expected for these surface preparation conditions chosen based on the previous detailed investigations of the pit formation in the same experimental setup. 30 Thus, AFM images confirm that surface defect sites are effectively introduced by ion sputtering and oxidation, and this would provide sufficiently reactive sites for the copper precursor molecules. It should be emphasized that the pit structures should not be considered as atomic-scale defect sites.…”

“…The work presented here will also take advantage of controlled sputtering/oxidation processes on HOPG to introduce specific defects. 30 Atomic force microscopy (AFM) is used to investigate the height of the surface nanostructures while scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) are used to identify their composition. Ex situ X-ray photoelectron spectroscopy (XPS) is utilized to follow the chemistry of copper deposition and to interrogate copper oxidation states.…”