Interestingly, the initial etching behavior for pre-heated silica NPs was quite similar to that for non-pre-heated Si NPs, although the initial EEO2 was higher than for pre-heated Si NPs, and the magnitude of the increase during initial etching was only a factor of ~2. The similarities suggests that the higher initial EEO2 and smaller increases during initial etching, result from preheated silica NPs having had atomically rough surfaces, even though pre-heating was estimated to have reached TNP near the bulk silica Tmelt (and well above the bulk Si Tmelt). Several processes might account for rough surfaces. During pre-heating, the NPs would have rapidly lost SiO, O, O2, etc. from their surfaces, and the CO2 laser was automatically terminated as soon as optical emission was detected, resulting in rapid cooling. Thus, there may simply not have been enough time to anneal out defects or other reactive Si sites created by surface decomposition and desorption. In addition, differential contraction of the NP surface layer and core during rapid cooling from the pre-heat temperature may have created a roughened or strained surface. That would occur, for example, if the NP core retained higher O concentration than the surface layer, as seems likely. Both Si and silica have low coefficients of thermal expansion at high temperatures, but the value for Si is roughly an order of magnitude higher.