Introduction
Laser and 2D materials interactions
Direct laser writing of graphene patterns
Fig.2 (a) Schematic illustration of the femtosecond direct laser writing reduction and patterning of GO; (b) optical microscopic images of different micropatterns; (c) atomic force microscopy image of the details of micropatterns, the bottom two images show the profile of the micropatterns [33] |
Laser thinning of 2D materials
Fig.3 (a) Schematic of laser interacts with MoS2 flake; (b) optical microscopic image of a multilayered MoS2 flake deposited onto a 285 nm SiO2/Si substrate; (c) same as in (b) after scanning a laser in the area marked by a dashed rectangle in (b). The laser thinning parameters were l = 514 nm, incident power on the sample 10 mW, scan step 400 nm, and exposure time of 0.1 s between steps [39] |
Laser doping of 2D materials
Fig.4 Laser-assisted doping of MoS2. (a) Schematic diagram of laser-assisted doping method. Focused laser locally illuminated on the MoS2 flakes (blue atoms, Mo; yellow atoms, S) located on a SiO2/Si substrate under diluted phosphine dopant gas environment; (b) optical image of as-prepared monolayer and five-layer MoS2 on SiO2/Si substrate (blue color represents MoS2); (c) AFM image of the zoomed area in (b). Its thickness is ~ 0.7 nm, nm, in a good agreement with the thickness of a monolayer of MoS2. The circle in (c) is the laser exposed spot area in the laser doping; (d) PL mapping of the zoomed area in (c) that showed the PL intensity enhancement of the laser-assisted doped area [46] |
Two beam laser interference technique
Fig.5 (a) Schematic illustration of the two-beam laser interference (TBLI) system for the fabrication of superhydrophobic graphene films; (b) photograph of an as-patterned graphene film, the structural color can be observed by the naked eye; (c) optical microscopic image of the graphene pattern; (d) schematic illustration of the graphene surface after the TBLI treatment; (e) scanning electron microscope (SEM) image of the superhydrophobic and iridescent graphene film [33] |
Broad applications
Photonics and optoelectronic devices
Ultrathin flat lens
Fig.6 Design of the GO lens. (a) Conceptual design and laser fabrication of the GO ultrathin lens; (b) amplitude and phase modulations provided by the transmission and refractive index difference, respectively, between the GO and RGO zones; (c) topographic profile of the GO lens measured with an optical profiler; (d) left: schematic of the wavefront manipulation by the GO lens converting the incident plane wave into a spherical wavefront. Right: intensity distributions of the 3D focal spot predicted by the analytical model for a GO lens with three rings and the radius of the most inner rings of 1.8 mm; (e, f) theoretical focal intensity distributions in the lateral and axial directions; (g, h) experimental focal intensity distributions along the lateral and axial directions [50] |
Ultrathin GO polarizers
Fig.8 (a) Schematic design of the proposed GO polarizer with 2D periodic C-shape arrays. The C-shape array is in the x-y plane and the incident light is in the y-z plane with the colatitude angle q; (b) optical microscopic image of fabricated C-shape array. The lattice constant of C-shape array is 3 mm, the line width of each C-shape is 500 nm and the radius of C-shape is 1 mm. Inset: A magnified image of the yellow box; (c) strong confinement of the incident light within the GO polarizer under TM polarization; (d) transmission spectra of the proposed GO polarizer with TE and TM polarized light incidence [22,53] |
Perfect absorber
Fig.9 (a) Schematic representation of a three-layer structure system with the top multilayer graphene-based metamaterial with thickness t patterned as gratings of period p. d is the width of the air groove; (b) optical profiler image of gratings with p = 980 nm and w = 400 nm; (c) cross-sectional plot of the optical profiler image; (d) measured absorption spectra for TE polarization, TM polarization, unpolarized light and sample without grating structure [56] |
Creating p-njunctions in graphene
Fig.10 (a) Fabricated n-doped regions in the form of the letters “UI” with the laser writing method; (b) resistance vs gate voltage (R-Vg) curves for a graphene FET as fabricated (black line), after spin coating TIPS-pentacene (red line), and after laser irradiation of the entire channel area (blue line) [59] |
Transparent conductive electrode
Fig.11 (a) Transmittance at 550 nm and sheet resistance of the laser reduced GO (LrGO) films on PET substrates as a function of their film thickness. The inset shows the UV-vis transmittance spectra of the LrGO films on PET; (b) sheet resistance (normalized to the unbending sheet resistance) for various bending angles and thicknesses; (c) schematic and (d) picture of the flexible PET/r-GO/PEDOT:PSS/P3HT:PCBM/Al photovoltaic devices fabricated; (e) illuminated current-voltage (J-V) curves of the solar cells with various LrGO film thicknesses [61] |
Laser-induced microstructuring of 2D perovskite
Electrochemical energy storage
Fig.14 (a) Schematics of CO2 laser-patterning of free-standing hydrated GO films to fabricate RGO-GO-RGO devices with in-plane and sandwich geometries. The black contrast in the top schematics corresponds to RGO, and the light contrast to unmodified hydrated GO. For in-plane devices, three different geometries were used, and the concentric circular pattern gives the highest capacitance density. The bottom row shows photographs of patterned films; (b) photograph of an array of concentric circular patterns fabricated on a free-standing hydrated GO film; (c) SEM image of the interface between GO and RGO, with yellow arrows indicating a long-range pseudo-ordered structure generated by laser-beam scanning [78] |
Other applications
Surface enhanced Raman scattering
Fig.15 (a) Schematic illustration of TBLI fabrication of RGO gratings and subsequent silver coating toward the development of SERS substrates. (i) TBLI treatment of GO film; (ii) light intensity distribution of two interfered laser beams; (iii) RGO gratings; and (iv) Ag-RGO gratings as SERS substrates; (b) comparison of SERS measured with two different laser polarization directions with respect to the gratings, red and blue curves show the SERS spectra measured with the polarization parallel and perpendicular to the gratings, respectively. (Inset) SEM image of the Ag-RGO gratings; red and blue marks show the laser polarization directions; (c) SERS spectra of RhB solution with different concentrations, from top to bottom the concentration decreased from 10−6 to 10−10 M [79] |
Biomedical applications
Fig.16 (a) Schematics of the steps proposed to create an ordered neural network on single layer graphene (SLG) substrate; (b) and (c) neural networks oriented along line patterns. In (b) yellow markers indicate the width of graphene stripes, kept at 40 mm, black markers indicate the width of etched stripes, i.e., 30 and 60 mm in the pattern shown. In (c) the boundary region between graphene (upper left) and patterned graphene is shown. For the samples shown the fluency used during laser patterning was 0.8 J/cm2 [83] |