That’s ok- sorry for that! I’m happy to explain anytime. I always tell my fellow coworkers or students in the past: don’t assume I’m right, dig and let me know if I’m wrong. ;)

In this case the environment in the vacuum chamber of the SEM isn’t a perfect vacuum- especially if you have outgassing samples or a lot of organics- when this is the case, you can bake various gaseous things onto the sample with the heat of the e-beam. The ebeam is like an old TV set- the beam rasters back and forth. When we sit zoomed in on a sample, the local ebeam energy is pretty high, and we can bake on material from the gas around it- then when we zoom out, the material we deposited will have the same shape as our view-screen/tv screen because thats where the ebeam rasters across the surface while looking zoomed in. So in this case the fact the rectangle is almost a perfect match for the screen’s aspect ratio, makes me wonder if I’m just looking at “beam damage” or “beam deposition” would be similar phrases. Although damage usually means actual damage and not deposition. Basically it’s not the sample, but what was baked onto the sample. I add it here because this type of mistake ends up making the researcher look silly- even if they have important contributions to make- which is a shame. I’ll try and review the article when I can- working for the man at the moment, but was happy to see a high tech microscope used here. Usually for organics it’s not too common to use SEM- but they have more capable organic compatible microscopes these days. :). So- kudos to the researchers- I just wish they had caught that first image on the left and not included it.