Electronic Transport and Raman Scattering in Size-Controlled Nanoperforated Graphene

We demonstrate the fabrication and study of the structure-property relationships of large-area (>1 cm(2)) semiconducting nanoperforated (NP) graphene with tunable constriction width (w = 7.5-14 nm), derived from CVD graphene using block copolymer lithography. Size-tunable constrictions were created while minimizing unintentional doping by using a dual buffer layer pattern-transfer method. An easily removable polymeric layer was sandwiched between an overlying silicon oxide layer and the underlying graphene. Perforation-size was controlled by overetching holes in the oxide prior to pattern transfer into graphene while the polymer protected the graphene from harsh conditions during oxide etching and lift off. The processing materials were removed using relatively mild solvents yielding the clean isolation of NP graphene and thereby facilitating Raman and electrical characterization. We correlate the D to G ratio as a function of w and show three regimes depending on w relative to the characteristic Raman relaxation length. Edge phonon peaks were also observed at 1450 and 1530 cm(-1) in the spectra, without the use of enhancement methods, due to high density of nanoconstricted graphene in the probe area. The resulting NP graphene exhibited semiconducting behavior with increasing ON/OFF conductance modulation with decreasing w at room temperature. The charge transport mobility decreases with increasing top-down reactive ion etching. From these comprehensive studies, we show that both electronic transport and Raman characteristics change in a concerted manner as w shrinks.