Week+of+September+20

September 20th: Becky had prepared a sample for me to scan when I arrived. It was annealed gold that had been exposed on the Polonium-212 from 5:00 p.m. Friday, the 17th, to 3:30 (when I arrived) on Monday, the 20th. The reasoning behind this was the thought that the longer the gold was exposed, the more impacts we could expect. Also, the sample had been 50% covered, with the exposed side having been marked by a sharpie. The thought behind this was that any impacts due to alpha-particles would be more noticeable if there were a control right next to it. Becky and I took this sample up to an optical microscope on the second floor of Nieuwland Hall. We had previously used this microscope to view a machined piece with square holes roughly 7 microns across. We could see the holes, and Becky said that the craters would likely be a similar size, so we should be able to see something. After taking several images, which we saved on a flash drive, we returned to the lab where I proceeded to scan the gold with the AFM. I managed to have a few clear images, trying to get as close to the middle as possible, with the goal of having an image partially exposed and partially covered.

September 21st: I scanned the half-exposed gold from yesterday, the 20th. However, I went with Becky and Annette to a tenure talk by a professor in the Chemistry department. This talk lasted about an hour, from 4 to 5, and we didn't return to the lab until about 5:10. After returning, I proceeded to continue scanning. However, the microscope was acting up and had trouble approaching. The tip also failed at this point, and it took a few extra minutes to change it. I managed to get a couple of images before the microscope really started acting up and I went home.

Update: I was using the portable AFM. The tip has to approach, although the process doesn't take as long and approaches in relation to the STM. Becky is hoping to go to the Rad Lab soon and use a optical microscope there, and possibly another AFM as well. The portable AFM is tricky in that the isolation vibration table that comes with it needs to be calibrated very precisely. The ideal weight is around 25 lbs. This allows the table to move at a regular and slow frequency, about 1/2 hz. However, the actual scan head of the microscope is light, only about two pounds. At first, we tried putting books on the vibration isolation table, but that proved crude and unbalanced. Becky then had the idea over a weekend to use a thin block of iron. It weighs about 20 lbs, and has allowed us to have much more consistent scans with less interference. The difference is actually significant. We went from having scans that were barely recognizable to very clear "frosted flake" structures, as we call them.