Laser-induced disassembly of a graphene single crystal into a nanocrystalline network

Abstract

We report about investigations of time-dependent structural modifications in single-crystal graphene due to laser irradiation even at moderate power levels of 1 mW in a diffraction-limited spot. The modifications have been characterized by in situ scanning confocal Raman spectroscopy, atomic force height microscopy, and transport studies. The time evolution of the Raman spectrum reveals two different effects: on a short-time scale, dopants, initially present on the flake, are removed. The longer time scale behavior points to a laser induced gradual local decomposition of single-crystal graphene into a network of interconnected nanocrystallites with a characteristic length scale of approximately 10 nm due to bond breaking. The broken bonds offer additional docking sites for adsorbates as confirmed in transport and AFM height studies. These controlled structural modifications may for instance be valuable for enhancing the local reactivity, trimming graphene based gas sensors and generating spatially varying doping patterns.

Kinetics of defect formation in chemically vapor deposited (CVD) graphene during laser irradiation: The case of Raman investigation

“…According to Krauss et al [11], these preliminary results indicate that additional defects are created when focusing the laser down to a micrometer-sized spot. It seems, in addition, that the application of the Raman technique to CVD graphene (instead of exfoliated), is harmful to the sample, despite the employment of lower power (64 kW/cm 2 against [11] 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 400 kW/cm 2 ) and energy (3.8 MJ/cm 2 against [11] 12 MJ/cm 2 ) densities. Actually, Tiberj et al [10] reported about photo-induced doping as directly connected to the substrate preparation, evidencing that, when graphene is transferred onto Si/SiO2 substrates used as-received and without any cleaning, the doping of graphene flakes remains constant for all the entire laser power range.…”

“…1a shows the Raman spectrum of the CVD graphene, collected in macro-configuration with a laser (=532 nm, wavelength) spot of d=100 μm diameter and a laser power at the sample P=11.7 mW (power density, Ψ150 W/cm 2 ) for Tinteg=60 s integration time. The spectrum is compared with a typical one from micro-Raman of exfoliated graphene [11], to highlight the similar quality, apart from the slightly higher D peak in the CVD case. Considering the spatial averaging character of the macrotool, this encouraging result suggested us to perform micro-Raman investigation to select the best areas, which reasonably should show an even better quality.…”

“…However, there are evidences in literature about the modification of graphene properties induced by intense laser irradiation, either in terms of reversible photon-induced doping of the material [10], disassembly of graphene monocrystal into a nanocrystalline network [11], or ablation of graphene multilayer till to a monolayer [12,13].…”

“…For these reasons, when the laser light is focused down to the diffraction limit, as in micro-Raman instruments, possible sample damage can occur, as reported in the case of exfoliated material [11]. The assessment of the technique in the case of CVD graphene is then necessary, otherwise information 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 extracted on the samples quality cannot be reliable at all.…”

Highly Selective Mercury Detection at Partially Oxidized Graphene/Poly(3,4-Ethylenedioxythiophene):Poly(Styrenesulfonate) Nanocomposite Film-Modified Electrode

“…The G band is characteristic of sp2-hybridized C = C bonds in graphene sheets (Childres et al, 2013); whereas, the D band is associated with structural defects and partially disordered structures of the sp2 domain (Childres et al, 2013). The 2D band located at 2718 cm −1 originates from a double-resonance process (Krauss et al, 2009;Yan et al, 2011). The calculated values of I D /I G listed in Table 1.…”