Optomechanical and Crystallization Phenomena Visualized with 4D Electron Microscopy: Interfacial Carbon Nanotubes on Silicon Nitride
With ultrafast electron microscopy (UEM), we report observation of the nanoscopic crystallization of amorphous silicon nitride, and the ultrashort optomechanical motion of the crystalline silicon nitride at the interface of an adhering carbon nanotube network. The in situ static crystallization of the silicon nitride occurs only in the presence of an adhering nanotube network, thus indicating their mediating role in reaching temperatures close to 1000 °C when exposed to a train of laser pulses. Under such condition, 4D visualization of the optomechanical motion of the specimen was followed by quantifying the change in diffraction contrast of crystalline silicon nitride, to which the nanotube network is bonded. The direction of the motion was established from a tilt series correlating the change in displacement with both the tilt angle and the response time. Correlation of nanoscopic motion with the picosecond atomic-scale dynamics suggests that electronic processes initiated in the nanotubes are responsible for the initial ultrafast optomechanical motion. The time scales accessible to UEM are 12 orders of magnitude shorter than those traditionally used to study the optomechanical motion of carbon nanotube networks, thus allowing for distinctions between the different electronic and thermal mechanisms to be made.
Additional Information© 2010 American Chemical Society. Received for review: 03/1/2010. Published on Web: 04/08/2010. This work was supported by the National Science Foundation and the Air Force Office of Scientific Research in the Gordon and Betty Moore Center for Physical Biology at the California Institute of Technology. We thank Dr. Spencer Baskin for helpful discussion on local and transient heating effects.
Supplemental Material - nl100733h_si_001.pdf
Supplemental Material - nl100733h_si_002.avi
Supplemental Material - nl100733h_si_003.avi
Supplemental Material - nl100733h_si_004.avi
Supplemental Material - nl100733h_si_005.avi