5:15 PM - 6:30 PM
[SIT21-P03] Measurements of local stress using TEM in-situ obserbation
Keywords:electron microscope, in-situ experiment, nano-deformation
[Introduction] Extensive in-situ loading/ indentation experiments have been conducted inside a transmission electron microscope (TEM) to understand the nanomechanical properties of materials (e.g., Wang et al., 2015). In these studies, the stress on the sample were estimated just by dividing the applied load by the area loaded on and/or analyzed by the finite element method. In this study, we succeeded in measuring the stress state within a sample directly from the electron diffraction patterns of a deformed sample.
[Materials and Methods] A thin film of monocrystalline silicon with 100 nm thickness was prepared by a focused ion beam (FIB, Helios NanoLab G3 CX, Thermo Fisher Scientific). In-situ indentation/ compression tests were performed with a diamond indenter inside the chamber of TEM at Kyoto University (JEM-2100F, JEOL), under the load-controlled mode up to 40, 100, 200, and 500 µN (Hysitron PI95 TEM PicoIndenter, Bruker). The film with the crystal zone axis of approximately [01-1] was compressed on the (001) plane along the [001] direction. Diffraction patterns were taken before, during, and after the compression. Digital Microgarph (Gatan, Inc.) and ReciPro (developed by Y. Seto, http://pmsl.planet.sci.kobe-u.ac.jp/~seto/) were used for data analysis. The equation of state of Si by Pandya et al. (2012) was used to calculate the stress from the lattice strain.
[Results and Discussion] The results show that the lattice spacing parallel to the loading axis [001] reduced on compression. On the other hand, the lattice spacing of the [110] direction, perpendicular to the compression axis, did not change during compression. Calculated stresses along the compression axis were ~1.7 GPa at 40 µN, ~2.4 GPa at 100 µN, ~3.7 GPa at 200 µN and ~7.1 GPa at 500 µN, respectively. The lattice parameter along the [110] direction changed negligibly or expanded slightly. The pressure was estimated from the change of a cell volume as ~1.1 GPa at 200 µN, and ~1.4 GPa at 500 µN, assuming that there was no strain along the direction of incident electron beam. The local stress became small with the increase of the distance from the contact point of the indenter. Clarifying the detailed geometry of the contacting point is needed for more accurate analysis.
Wang et al., (2015) Scripta Materialia, 98, 40; Pandya et al. (2012) J. Phys.: Conf. Ser. 377 012097
[Materials and Methods] A thin film of monocrystalline silicon with 100 nm thickness was prepared by a focused ion beam (FIB, Helios NanoLab G3 CX, Thermo Fisher Scientific). In-situ indentation/ compression tests were performed with a diamond indenter inside the chamber of TEM at Kyoto University (JEM-2100F, JEOL), under the load-controlled mode up to 40, 100, 200, and 500 µN (Hysitron PI95 TEM PicoIndenter, Bruker). The film with the crystal zone axis of approximately [01-1] was compressed on the (001) plane along the [001] direction. Diffraction patterns were taken before, during, and after the compression. Digital Microgarph (Gatan, Inc.) and ReciPro (developed by Y. Seto, http://pmsl.planet.sci.kobe-u.ac.jp/~seto/) were used for data analysis. The equation of state of Si by Pandya et al. (2012) was used to calculate the stress from the lattice strain.
[Results and Discussion] The results show that the lattice spacing parallel to the loading axis [001] reduced on compression. On the other hand, the lattice spacing of the [110] direction, perpendicular to the compression axis, did not change during compression. Calculated stresses along the compression axis were ~1.7 GPa at 40 µN, ~2.4 GPa at 100 µN, ~3.7 GPa at 200 µN and ~7.1 GPa at 500 µN, respectively. The lattice parameter along the [110] direction changed negligibly or expanded slightly. The pressure was estimated from the change of a cell volume as ~1.1 GPa at 200 µN, and ~1.4 GPa at 500 µN, assuming that there was no strain along the direction of incident electron beam. The local stress became small with the increase of the distance from the contact point of the indenter. Clarifying the detailed geometry of the contacting point is needed for more accurate analysis.
Wang et al., (2015) Scripta Materialia, 98, 40; Pandya et al. (2012) J. Phys.: Conf. Ser. 377 012097