Nanoscale patterning at the Si/SiO₂/graphene interface by focused He⁺ beam

Abstract

We have studied the capability of He+ focused ion beam (He+-FIB) patterning to fabricate defect arrays on the Si/SiO2/Graphene interface using a combination of atomic force microscopy (AFM) and Raman imaging to probe damage zones. In general, an amorphized ‘blister’ region of cylindrical symmetry results upon exposing the surface to the stationary focused He+ beam. The topography of the amorphized region depends strongly on the ion dose, DS , (ranging from 103 to 107ions/spot) with craters and holes observed at higher doses. Furthermore, the surface morphology depends on the distance between adjacent irradiated spots, LS . Increasing the dose leads to (enhanced) subsurface amorphization and a local height increase relative to the unexposed regions. At the highest areal ion dose, the average height of a patterned area also increases as ∼1/LS . Correspondingly, in optical micrographs, the µm2-sized patterned surface regions change appearance. These phenomena can be explained by implantation of the He+ ions into the subsurface layers, formation of helium nanobubbles, expansion and modification of the dielectric constant of the patterned material. The corresponding modifications of the terminating graphene monolayer have been monitored by micro Raman imaging. At low ion doses, DS , the graphene becomes modified by carbon atom defects which perturb the 2D lattice (as indicated by increasing D/G Raman mode ratio). Additional x-ray photoionization spectroscopy (XPS) measurements allow us to infer that for moderate ion doses, scattering of He+ ions by the subsurface results in the oxidation of the graphene network. For largest doses and smallest LS values, the He+ beam activates extensive Si/SiO2/C bond rearrangement and a multicomponent material possibly comprising SiC and silicon oxycarbides, SiOC, is observed. We also infer parameter ranges for He+-FIB patterning defect arrays of potential use for pinning transition metal nanoparticles in model studies of heterogeneous catalysis.

Nanoscale Trapping of Interlayer Excitons in a 2D Semiconductor Heterostructure

“…Our approach opens up a new avenue to realize deterministically placed IX quantum dots that make use of the highly tunable energy of the IX energy. In future studies, we plan to refine our architecture decreasing the trap diameter and increasing the strength of the confinement potential through ion beam lithography and dielectric engineering approaches 26 to ultimately trap single stable IXs which can be integrated with on-chip photonic or plasmonic structures for scalable quantum technology applications.…”

Prediction Method of Graphene Defect Modification Based on Neural Network

“…Bottcher et al used Staudenmaier method to prepare graphene. Natural expandable graphite with a fineness of 200 mesh was used as raw material, treated with sulfuric acid, nitric acid, and other oxidants for 96 h, washed with dilute hydrochloric acid and deionized water, dried in vacuum, and rapidly thermally expanded in high-temperature equipment in an argon atmosphere to prepare graphene [22]. Smolsky et al oxidized graphene with sulfuric acid, nitric acid, and other oxidants, so that active groups such as carboxyl and hydroxyl groups were generated on its molecular surface and then esterified with it with coupling agent KH-560 [23].…”