TEM in-situ heating at Vanderbilt University
Hello everyone! The new FEI Osiris TEM system has been finally setup recently. With the new purchased Gatan single tilt heating holder 628, we were managed to do an in-situ heating experiment with the Osiris system last week. We used the same sample OSO201510, which was used in Harvard, to test this heating holder as a start.
In this video, we can clearly see the pore forming and coalescing during the crystallization process. This visible crystallization process took place quickly. The dynamic Si crystallization and pore movement took place at 800C, which is above the temperature of 680C that we observed at Harvard. Clearly there is a temperature discrepancy in this in-situ heating experiment given that very similar heating holder (it was double tile heating holder 652 from Gatan) was used in Harvard. I tend to believe that the temperature readout from this new 628 holder is not well calibrated since this is the first time use. However this heating experiment is very encouraging because the 628 heating holder is functioning well with the new Osiris system despite of the temperature calibration problem. We should be able to solve this issue and run more in-situ heating experiments in the near future, which would be critical to study the pore formation mechanism and the very interesting re-amorphization phenomenon of Si film.
Another thing I want to mention is that I met a student who was giving a talk about the Void-induced Solid-Phase Crystallization in a-Si:H Films Seeded by Silicon Nanocrystals in the MRS conference. This student is Andrew Wagner, who did his undergraduate at RIT, and he is currently working on his Phd advised by Professor Uwe Kortshagen at University of Minnesota. In his talk he showed a video which looks VERY similar as our pore movement video and his talk was about a solid-phase crystallization (SPC) mechanism has been observed in hydrogenated amorphous silicon (a-Si:H) wherein small voids, bounded by amorphous and crystalline surfaces, propagate through the amorphous matrix leaving behind a crystalline tail. The major difference between us is that he intentionally formed some nano-voids at the bottom of Si nanoparticles due to the shadow effect during the deposition. These nano-voids moved around and coalesced during the crystallization process when the sample was heated up. We had a nice talk afterward and clearly we are not the only group who is working in this field.