Annealing reduces the vacancy defects and creates new grain boundaries (Fig. ), which is consistent with the fact that the position of the D band is almost the same after thermal treatment (Table ). For the single-layered NPGs, both vacancies and grain boundaries remain: The value of ID/ID' =5.33 (Table ) is in between the values of vacancy (~7) and grain boundary (~3.5). For the stacked NPG (NPG (stacked)), most of the vacancies are removed. The parent stacked NPC (NPC (stacked) has ID/ID'=9.4 (Table ), which indicates that it has both sp 3 (ID/ID' ~13) and vacancy defects (~7). The annealing reduced the ID/ID' value changed to 4.12, which is close to the value of grain boundary (~3.5). The mean distance between the defects in NPGs (RNPG) can also be estimated using ID/IG. The ID/IG of 1.7 for θ-and γ-NPGs corresponds to RNPG = 7.0 nm, from Eq. 2. These values indicate that there exist vacancy and SW defects per 9 × 10 2 hexagonal rings in NPGs on average. The λRaman for θ-and γ-NPGs is calculated to be 1.1 ×10 -3 , which agrees with λTPD. The defect density decreases to λTPD(NPG) / λTPD (NPC) ≈ λRaman(NPGs) / λRaman (NPCs) = 4-6% upon annealing NPCs. The formation of multiple defects on a hexagonal ring is negligible in all NPGs as in NPCs (Fig. ). The red shifts of the SW and SW+D bands in NPGs may reflect (i) the strain release by defect healing around the last SW sites and/or (ii) the creation of fewer SW defects in the new grain boundary.