After this point, peaks either did not change in width (D and 2D, Figs. 4e and 4f respectively) or sharpened (D' and G, Figs. 4g and 4h respectively). In graphene, the G peak typically sharpens upon doping and broadens under strain. The broadening (sharpening) of the G peak below (above) a critical dose therefore hints at a change in the state of the material with respect to strain and charge density. This is discussed in detail further below. Using the relationships between the peak intensities, we can elucidate various physical properties that shed a light on the process of e-beam chemistry with radiolyzed water. In the following discussion, we address three such analyses. First, we studied the ID/IG ratio as a function of electron dose, at a constant acceleration voltage (1 kV) and varying dwell times (40 -100 µs). Up to a certain defect concentration, the introduction of additional defects increases the probability of phonon scattering by lattice defects and thus the D peak intensity. The D peak in graphene has A1g symmetry, requiring a complete 6-fold C-ring. At high defect concentrations, the probability of finding such a ring decreases and the magnitude of D diminishes. As can be determined from a plot of ID/IG with increasing dose (Fig. ), we can precisely tune the magnitude of ID/IG, and hence the defect spacing, simply by adjusting the dose. It is also evident from Fig. that, at a fixed dose, the dwell time does not matter with respect to the measured defect density in the patterned region -td only plays a part in reducing or increasing the modification of the graphene surface outside of the intentionally patterned region (as shown in Fig. ). Interestingly, ID/IG increased up to a certain dose (~4500 µC/cm 2 ) and decreased at higher doses; this inflection point is similar to the inflection points noted for the Raman peak frequencies and widths Fig. . The reason for this increase and subsequent decrease in ID/IG is related to strain and doping in the graphene and is explained in greater detail further below. As mentioned in the Introduction section, ID/ID' serves as an indicator of the type of defect introduced in graphene. The fact that the two defect peaks have different dependencies on symmetry and defect concentration mean that their intensity ratio (i.e. ID/ID' ) is a convenient tool for pinpointing the type of defect present. It has been experimentally and theoretically shown that sp type defects (i.e. those that do not destroy the underlying graphene lattice) result in ID/ID' ratios of ~8-13 while vacancy-type defects (i.e. those that do destroy the graphene lattice) result in a lower ratio, ~5-7. This discernment of defect type allows us to tune defect engineering to the limits of modification of the graphene surface and beyond to the introduction of permanent, vacancy-type defects. An analysis of the data collected at the lowest beam energy (1 kV, Fig. ) reveals that, with increasing dose, ID/ID' remained safely within the confines of the sp 3 -type defect regime. I2D/IG behaved in a similar fashion as ID/ID' , decreasing steadily until a dose ~4500 µC/cm 2 , after which it more or less leveled off. The intensity of the 2D peak in monolayer graphene is tied to that of the D peak since both peaks arise from TO phonons. While a defect is not necessary for the appearance of the 2D peak, the probability of the two-phonon scattering process reduces with increasing defect density. In other words, the 2D peak intensity is inversely proportional to the D peak intensity and thus we expect to see opposite trends between ID/IG and I2D/IG, as is borne out by the data in Figs. and.