The in situ TEM cell was composed of two microelectromechanical systems (MEMS) chips, each composed of a silicon base with a 550 x 50 µm hole in the center covered by a freestanding 50 nm thick amorphous silicon nitride film. One chip was patterned with four 500 nm gold spacer posts at the corners to set the chamber height. Each chip was cleaned with acetone and methanol to remove a protective photoresist coating and dried gently with filtered compressed air.