Figure 1
From: Preparing local strain patterns in graphene by atomic force microscope based indentation
Preparing strain patterns in graphene. (a) AFM indentation patterning scheme. (b) AFM topography image and height profile of indentation lines of various depth, prepared by moving the tip along the sample surface (inset: lattice resolved AFM image of graphene flake). (c) Raman map of patterned graphene sample. Color scale encodes the position of the 2D peak, obtained by fitting a Lorentz function. The sample contains 2 × 2.5 μm2 indent line patterns, having a line spacing of 50 nm, as in (b). These line patterns can be easily identified by the increased downshift of the 2D peak wave number and are marked by colored rectangles. The SiO2 substrate areas show up as noise in this image, since the Lorentz fit to the 2D peak fails in this area. (d) Correlation plot of the G-2D peak positions measured on line patterns with increasing indentation depth. Colors of the data points correspond to the colors in c. Blue slope corresponds to the ratio of the Grüneisen parameters for the 2D and G peaks33, while the red slope is the shift due to p doping. The maximum average strain relative to the pristine graphene is 0.1%. (e) Raw Raman spectra in a single point measured on the various line patterns. (f,g) Plots of the G and 2D peak (colors correspond to the colors used in (c). The spectra are offset in intensity with respect to each other for the sake of clarity. Data in this figure was measured, using 532 nm excitation.
