Effect of amorphous carbon coating on the performance of liquid phase transmission electron microscopy (LP-TEM) and the dynamics of enclosed Pt nano-colloids

Abstract

Ultra-thin silicon nitride (SiN) membranes are critical in microfabrication-based liquid cells (LCs) for transmission electron microscopy (TEM). This study used a homemade LC with a 50-nm SiN membrane to study the dynamics of 2.58-nm platinum (Pt) nanoparticles (NPs) in approximately 200-nm-deep water. When a strong beam with electron flux ranging from 2.5 × 103 to 1.4 × 106 e-/(nm2 s) was applied to resolve the NPs, the beam caused NP aggregation and even drilled a hole on the top membrane. The hole drilling was prevented by coating a 1-4-nm-thick amorphous carbon layer on both sides of the membrane. The NP aggregation rate also decreased with increasing carbon thickness. After overcoming the aforementioned issues, lattice fringes of the Pt NPs were visible when the NPs were attached to the membrane of the 4-nm-carbon-coated LC containing a thin liquid layer. The effects of the electron beam and carbon on the LC and Pt NPs were investigated and discussed. This work provides a reference for LC-TEM research using strong electron beams.