Extreme Monolayer-Selectivity of Hydrogen-Plasma Reactions with Graphene

Abstract

We study the effect of remote hydrogen plasma on graphene deposited on SiO₂. We observe strong monolayer selectivity for reactions with plasma species, characterized by isotropic hole formation in the basal plane of monolayers and etching from the sheet edges. The areal density of etch pits on monolayers is 2 orders of magnitude higher than on bilayers or thicker sheets. For bilayer or thicker sheets, the etch pit morphology is also quite different: hexagonal etch pits of uniform size, indicating that etching is highly anisotropic and proceeds from pre-existing defects rather than nucleating continuously as on monolayers. The etch rate displays a pronounced dependence on sample temperature for monolayer and multilayer graphene alike: very slow at room temperature, peaking at 400 °C and suppressed entirely at 700 °C. Applying the same hydrogen plasma treatment to graphene deposited on the much smoother substrate mica leads to very similar phenomenology as on the rougher SiO₂, suggesting that a factor other than substrate roughness controls the reactivity of monolayer graphene with hydrogen plasma species.

Plasma-enhanced chemical vapor deposition of graphene on copper substrates

“…Similar etching effects of remote hydrogen plasmas were previously reported. 32 However, in contrast to these studies, we are not observing high monolayer selectivity but in fact do not observe any etching of the monolayer at all. We believe that this is due to the fundamental differences in the studies given that we use a carbon source gas in addition to hydrogen while in 32 hydrogen alone was used to study the etching.…”

“…32 However, in contrast to these studies, we are not observing high monolayer selectivity but in fact do not observe any etching of the monolayer at all. We believe that this is due to the fundamental differences in the studies given that we use a carbon source gas in addition to hydrogen while in 32 hydrogen alone was used to study the etching. Hence we believe that two competing mechanisms occur in our process with a simultaneous etching of graphene and the deposition of carbon on the surface at the same time.…”

“…In our experiments we were not able to synthesize graphene at lower temperatures than 800 • C. This is in good agreement with the temperature dependence of the etching rate found in 32 where the highest reaction rates occurred between 500 and 600 • C and decreased for higher temperatures. In our experiments the etching effect is the dominating process at lower temperatures and thus suppressing any graphene synthesis on the surface.…”

Graphene etching on SiC grains as a path to interstellar polycyclic aromatic hydrocarbons formation

“…The etching process has attacked the graphene in contact with the H-passivated substrate, and the process has stopped at the step edge where the overlayer becomes BLG. Thus, the presence of BLG can be considered as a protective film with respect to H attack 31,32 . This could be the reason why this process does not disrupt the whole SiC grain.…”

Weak localization and Raman study of anisotropically etched graphene antidots

“…[14][15][16][17][18][19][20][21][22][23] The etching reaction can occur in a catalyzed [14][15][16][17] or in a noncatalyzed form. 18,[20][21][22][23] Only the latter allows position control of the edges via a lithographic patterning process prior to the anisotropic etching.…”