These maps are color-coded, and thus the shift in color from yellow-green to blue-green is showing a decrease of pitch as the degree of swelling increases. As the degree of swelling is raised from 1.6 to 2.2, the average values of localized pitch range drop from 36.5 nm to from 32.5 nm (displayed graphically in Figure ). Similar trends showing a decrease in pitch with increasing swelling degrees have been observed by others for different initial film thicknesses. At first glance it may seem somewhat counterintuitive that the pitch decreases as the swelling degree increases, however, it is important to realize that the film can only swell in the vertical direction perpendicular to the substrate, which causes the microdomains to be become non-spherical where they shrink in size in the in-plane direction and stretch in the out-of-plane direction. The decrease in pitch with increased swelling degree can be best understood by noting that the domain spacing, 𝐿, in the strong segregation limit is given by 𝐿 ∼ 𝑁 #/% 𝜒 eff &/' . Given that the effective Flory-Huggins interaction parameter 𝜒 decreases linearly with the amount of solvent incorporated into the film, the domain spacing is expected to decrease as swelling degree increases, as observed. Similarly, solvent molecules can fully incorporate into thinner films more easily compared to thicker films, leading to a decrease in pitch. Before quantitatively analyzing the defects in these BCP dot patterns, it is first useful to visualize the grains structures observed with different annealing conditions. The local cell orientation of each dot is mapped in Figure , which effectively maps out individual grains (regions where all the BCP dots have the same relative orientation). These results clearly demonstrate the large variability in long-range ordering as a function of initial film thickness and swelling degree. Some films comprise many very small, sub-100 nm grains, and others are uniform over micron scales. At a film thickness of 20.0 nm, the annealed films have extremely small grains (on the order of a few lattice pitches) and the grains themselves have a low degree of local orientational ordering (vide infra). There also appears to be regions of optimal grain size and local orientational ordering. For example, at an initial film thickness of 24.0 nm, the grain size increases as the swelling degree increases, reaching a maximum size, but then decreasing as the swelling degree is further increased; the local ordering also seems to significantly decrease. The initial increase in grain size with increased swelling degree is a result of the intended action of solvent annealing, where increased solvent vapour incorporated into the film increases chain mobility, allowing for the formation of ordered lattice structures with lower configurational energy. However, this increase in chain mobility is always accompanied by a decrease in segregation strength, and thus as the segregation strength approaches the order-disorder transition (ODT) the local microdomain ordering begins to decrease. These competing processes of chain mobility and segregation strength explain the trends observed in Figure where there will be an optimal swelling degree for a given initial film thickness to maximize grain size and longrange ordering. Although these BCP cell orientation maps provide a useful qualitative sense of grain size and long-range ordering, it is necessary to quantitatively define and measure defects in order to apply ML methods to optimize the SVA processing. One of the most conventional methods for identifying defects is to determine the coordination number, where any non-6 fold coordinated dots are marked as defects. Maps of the local coordination number are shown in Figure , which very clearly identify topological point defects like dislocations and disclinations having 5and 7-fold coordinated sites. Although the coordination number very easily identifies point defects, it does not encode for fluctuations and deviations from hexagonal ideality, which is a significant concern in these soft BCP lattices during SVA. These deviations in local hexagonality are important to consider when attempting to quantify the defectivity of these BCP lattices and their broader applications in bit-patterned media. Specifically, it is easy to imagine a lattice with only 6-fold coordinated sites, but have sufficiently large local fluctuations in dot positioning to cause read/write errors. With this concept in mind, we define the metric of registration error (𝑅 " ) in order to identify fluctuational defects.