Effect of Silicon Nitride Substrate Thickness and Surface Treatment on Thermal Transport and Local Heating of Gold Nanoparticles under Electron Beam Irradiation

Silicon nitride (SiN) is the principal substrate material used in solid and liquid phase in situ transmission electron microscopy (TEM), due to its exceptional thermal stability, mechanical strength, and chemical robustness, which enable direct deposition and high-resolution observation of dynamic reactions across a wide temperature range. Here, in situ TEM is used to systematically probe the effects of SiN substrate thickness and surface chemistry on electron beam–induced structural transformation and decomposition of gold nanoparticles. Our results reveal a rapid, edge-initiated solid-to-amorphous liquid-like transition, which is markedly accelerated on thicker SiN substrates (40–50 nm) due to enhanced local heat accumulation and reduced thermal dissipation. In contrast, thinner SiN substrates (10 nm) facilitate more efficient heat dissipation, thereby delaying nanoparticle destabilization and structural transition. Plasma treatment of SiN surfaces further suppresses melting by increasing nanoparticle adhesion and promoting thermal dissipation. Comparative heating chip-assisted in situ experiments indicate that both electron beam–induced structural transition and thermally driven melting of gold nanoparticles proceed via similar pathways, originating at nanoparticle edges before propagating inward. COMSOL Multiphysics simulations suggest that thicker SiN substrates act as thermal reservoirs, efficiently trapping heat and triggering structural transition in gold nanoparticles. These findings demonstrate how SiN substrate thickness and surface modification impact gold nanoparticle stability and dynamics under extreme environmental conditions, offering critical insights for the controlled design of nanomaterials in advanced electron microscopy platforms.