In-situ Quantitative TEM Studies with Micro-electro-mechanical Systems
By: Aman Haque, Mechanical & Nuclear Engineering, the Pennsylvania State University
The modern Transmission Electron Microscope (TEM) is a complete analytical tool with only one inconvenience – it has a very small chamber size. The challenges in miniaturizing an entire experimental setup to fit in a 3 mm diameter footprint have been formidable, constraining in-situ TEM studies to mostly real time qualitative visualization. We approach the problem with micro-electro-mechanical systems (MEMS), a perfect foil for the TEM for quantitative testing. We present a setup capable of performing mechanical tests inside a transmission electron microscope (TEM) at elevated temperature up to 1000 °K. The MEMS device is fabricated on silicon-on-insulator (SOI) wafer and has integrated heaters, force sensors and thermal actuators. The device can be co-fabricated with thin films deposited on the wafer, as long as they can be patterned and subsequently released from the substrate to create freestanding uniaxial tension specimens. Young’s modulus, fracture stress as well as stress-strain relationship of thin films at high temperatures can be demonstrated to visualize deformation and fracture mechanisms inside the TEM. The device is demonstrated on metal films as well as graphene, molybdenum di-sulfide and boron nitride. The advantage of the MEMS approach is the ability to multi-function in a single chip. We demonstrate thus by adding microelectrodes for in-situ measurement of thermal and electrical conductivity inside the TEM.