As the reaction surface area is influenced by the interaction volume, one can potentially engineer functionalities at a specific atomic location with a high resolution e-beam. Alternately, one can create complex patterns by rastering a broader e-beam across a substrate-supported sample, as illustrated in Fig. , which depicts an SEM image of a graphene surface patterned with the emblem of the United States Air Force (USAF). The outline of the emblem can be discerned in Fig. due to a controlled amount of adventitious carbon deposited onto the surface. The corresponding Raman intensity map in Fig. shows a much more striking contrast where the defect density in the pattern is plotted as the ratio of intensities (ID/IG) of the disorder-induced D peak ~1350 cm -1 (with the 514.4 nm excitation wavelength) and the sp 2 carbon stretching mode ~1580 cm -1 . The D peak in graphene arises from intervalley scattering of a transverse optical (TO) phonon with a lattice defect, and the ID/IG value has been extensively used as a qualitative measure of the defect density in sp 2 carbon materials (graphite, graphene and carbon nanotubes). X-ray photoelectron spectroscopy (XPS) analysis on our patterned graphene revealed the origin of the defects to be functionalization of the graphene surface with hydroxyl (C-OH), epoxide (C-O-C) and carboxyl (-COOH) groups. Individual Raman spectra from the graphene outside and inside the patterned area are displayed in Fig. , and show the D and G peaks in addition to the second order 2D peak, which arises from the scattering of two TO phonons from the K point of the graphene Brillouin zone. In addition to these peaks, a second disorder-related peak, labeled D' can be observed in the spectrum from the patterned region. The D' peak arises from intravalley scattering of a TO phonon with a lattice defect, and its intensity has been shown to be sensitive to the type of defect in the graphene lattice, i.e. sp 3 or vacancies. 42 Having demonstrated that e-beam chemistry can be used to pattern and functionalize graphene, we next show how the various processing parameters in the ESEM can be used to tune and optimize the resulting patterns. Since Raman spectra from graphene offer insights into its physical properties, our primary metrics of interest are the Raman spectral features, namely the frequencies and widths of the D, G, D' and 2D peaks, as well as the ID/IG ratio as a measure of the functionalization (or defect density) in graphene. Among the many interrelated process parameters in the ESEM, the physics of the e-beam is nicely captured by the total beam dose (in units of µC/cm 2 ), which is given by the relationship Dose = (td)(Ibeam)/P 2 . Here P is the shot pitch (i.e. the spacing between e-beam probe positions), td is the dwell time, and Ibeam is the beam current. Therefore, the variables under investigation for pattern optimization are 1) pressure, 2) voltage, 3) dwell time, 4) pitch, and 5) beam dose. In this study, we systematically probed each of these variables in a parametric study by varying each variable and keeping the others constant in order to see their effects on the Raman spectral features of graphene. Our study not only identified the optimal parameters for controlling the defect density (and thereby functionalization) in graphene, but also reveals the fundamental physics of the e-beam chemistry process.