High-power laser irradiation for high-temperature in situ transmission electron microscopy.

We developed high temperature in situ transmission electron microscopy using a high-density laser irradiation device (nominal maximum laser density ~9.4 GW/m) and a corresponding heat shielding sample mount device. The spatial line resolution of the microscope was maintained to be 0.14 nm at ambient temperatures after the installation of the laser irradiation device. The system was applied to the investigation of high temperature structural variation in tungsten plates. When the laser power was increased up to irradiation densities of approximately 61-280 MW/m (laser source output: 130-590 mW) to degrade tungsten plates, the microscope was undamaged. The surface dynamics was observed in situ by lattice imaging at irradiation densities of approximately 61-75 MW/m (laser source output: 130-160 mW); the spatial line resolution of the microscope was maintained to be 0.23 nm at high temperatures. It was expected that high temperature observation is realized using this heating system, which can be applied to the investigation of various advanced heat-resistant materials. We found using this heating system that degradation in tungsten plates started from surfaces and progressed through the preferential generation of characteristic defects, such as atomistic and nanometer holes and rods, and their subsequent evolution in thinner regions during the heating. It was demonstrated that the holes and rod were truncated with {110} sidewalls, i.e., these surfaces were stable in tungsten at high temperatures.