New TEM grids coated with ultrathin amorphous films have been developed using atomic layer deposition technique. The amorphous films can withstand temperatures over in air and in vacuum when the thickness of the film is 2？nm, and up to in air when the thickness is 25？nm, which makes heating TEM grids with nanoparticles up to in air and immediate TEM observation without interrupting the nanoparticles possible. Such coated TEM grids are very much desired for applications in high-temperature high-resolution transmission electron microscopy. 1. Introduction High-temperature high-resolution transmission electron microscopy (HRTEM) has been widely utilized to study the dynamic behaviors of nanoparticles at elevated temperatures [1–11], such as morphology [1], oxidation [2], melting [3–5], structural transformation [6], evaporation [7], recrystallization [8], phase stability [9], and growth [10] of nanoparticles. In these high-temperature HRTEM investigations, the supporting films coated on TEM grids should be thin enough (not to blur the HRTEM images of nanoparticles) and be mechanically stable (to support the nanoparticles) up to several hundred Celsius right before TEM observation without postheating processing. Unfortunately such ideal ultra-thin and mechanically stable supporting films are not available. The conventional ultra-thin carbon supporting films with thickness of several nanometers are suitable for HRTEM imaging and electron diffraction patterning at room temperature and in vacuum [12]. However, the carbon supporting films are not mechanically stable at high temperatures, always break in vacuum or burn away in air upon heating. In order to improve mechanical stability of the carbon supporting films, a thermally stable silicon oxide was deposited on the conventional carbon films using sputtering method [13]. The deposited oxide films were too thick and blurred HRTEM images while the quality of the deposited oxide films was hard to be controlled because of the sputtering deposition technique. Gold-platinum alloys [14] and germanium films [15] were also sputtered on the carbon supporting films, but the coated films were only suitable for HRTEM up to C in vacuum and could not resist oxidization in air at high temperatures. In order to withstand temperatures higher than C, silicon-based membrane window grids, like silicon oxide membranes [16] and silicon nitride membranes[17], have recently been developed to meet the new requirement of high-temperature TEM experiments. These commercial membrane window grids can withstand temperatures up to C in air
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