Crystallographic Etching of Few-Layer Graphene

Abstract

We demonstrate a method by which few-layer graphene samples can be etched along crystallographic axes by thermally activated metallic nanoparticles. The technique results in long (>1 µm) crystallographic edges etched through to the insulating substrate, making the process potentially useful for atomically precise graphene device fabrication. This advance could enable atomically precise construction of integrated circuits from single graphene sheets with a wide range of technological applications.Due to its remarkable electronic properties, few layer graphene is emerging as a promising new material for use in a vast array of postsilicon nanoelectronic devices incorporating quantum size effects.1,2 Of particular interest would be the construction of atomically precise graphene nanoribbons, in which charge carriers are confined in the lateral dimension whereby the electronic properties are controlled by the width and specific crystallographic orientation of the ribbon.3−14 Such structures hold enormous promise as nanoscale devices similar to those recently developed using carbon nanotubes 2,11,15 with the added advantage that graphenes two-dimensionality lends itself to existing device architectures based on planar geometries.However, these structures have so far been impossible to achieve because of the rough noncrystalline edges of the graphene that result from current state-of-the-art nanolithography techniques.2,16,17 These rough edges are thought to be the crucial limiting factor to attaining useful performance and on/off current ratios from nanoscale graphene devices. 13,18,19 As a step toward band gap engineering of this material, we have developed a means by which fewlayer graphene (FLG) samples can be etched along crystallographic axes by thermally activated metallic nanoparticles. 20 The technique results in long (>1 µm) trenches commensurate with the crystal lattice that are etched through to the supporting insulating substrate, making the process potentially useful for atomically precise graphene device fabrication, as well as indicating a possible method by which entire circuits could be carved out from single graphene sheets. Our initial samples (before etching) consisted of pristine few-layer graphene sheets transferred onto highly doped Si substrates with 300 nm thermally grown SiO 2 by mechanical exfoliation under ambient conditions, similar to the technique described in ref 21. Flakes of few-layer graphene are identified using optical microscopy. Height imaging of our samples is done using a Veeco Dimension 3100 atomic force microscope (AFM) operating in intermittent contact mode, with Si 3 N 4 -coated tips (NSC15, Mikromasch) of curvature * E-mail: drstrach@sas.upenn.edu † E-mail: cjohnson@physics.upenn.edu 1 radius ≤ 20 nm. Samples are also characterized using a JEOL JSM6400 scanning electron microscope (with a LaB 6 filament).The FLG on SiO 2 /Si substrates are uniformly spin-coated with ∼15 mL solution of 50 mg/L Fe(NO 3 ) 3 ·9H 2 O in isopropyl alcohol (HPLC grade). The samples are th...

Catalytic subsurface etching of nanoscale channels in graphite

“…Subsequently deposited Ni nanoparticles resting at these artificial and at the natural step edges serve as catalyst for hydrogenation of carbon when the sample is exposed to high temperature in H atmosphere (see Methods for more details). It is understood that the nanoparticle is dragged into the void where carbon atoms have been removed at the edge of the sheet, catalyses further hydrogenation of carbon and successively etches a channel from the edge into the sheet, following the main symmetry directions of carbon lattice 1,3,[5][6][7][8][9][10] (see also Fig. 1a).…”

“…In recent years it has attracted renewed attention as a possible route for nanopatterning of graphene, especially for the production of graphene nanoribbons. Metallic nanoparticles etch the surface layers of graphite [1][2][3][4][5][6][7][8] , as well as single-layer graphene sheets [9][10] . The process is anisotropic along the crystallographic highsymmetry directions, that is, the zigzag /11-20S or armchair /10-10S directions.…”

The atomistic mechanism of carbon nanotube cutting catalyzed by nickel under an electron beam

“…(2) min E  10 eV for two-coordinate atoms and three-coordinate atoms in non-hexagonal rings or within two bonds from one-coordinate, two-coordinate and three-coordinate atoms in nonhexagonal rings, and (3) (3) min E  17 eV for three-coordinate atoms in the perfect hexagonal part of the carbon network (two bonds away from any atoms of the types listed above). As most of the irradiation-induced events take place for atoms from the second group, two values for the corresponding minimal transferred energy (2) min E  10 eV and 13 eV are considered in the present paper to study the sensitivity of the results to this parameter.…”

Anisotropic Etching and Nanoribbon Formation in Single-Layer Graphene

“…. Indeed, previous studies of catalytic gasification of carbon found that catalytic metal nanoparticles would sometimes etch graphite along crystallographic directions, creating both armchair and zigzag edges [27][28][29][30][31] . …”

“…The hope for an anisotropic etching method is not unfounded though, because zigzag and armchair edges have markedly different chemical reactivities 25,26 . Indeed, previous studies of catalytic gasification of carbon found that catalytic metal nanoparticles would sometimes etch graphite along crystallographic directions, creating both armchair and zigzag edges [27][28][29][30][31] .…”