Limitation of the use of thin Amorphous Carbon Substrates for High Temperature Microscopy

Abstract

Carbon films have been used as substrates by many authors at temperatures ranging from 400°-1050°C(1-4). At such high temperatures, however, substrate/ grid interactions become appreciable and the carbon film becomes contaminated, due to carbide formation. Therefore, a series of experiments was performed on the C/Ti, C/Mo, and C/W film/support-grid systems to determine the usefulness of carbon substrates for high temperature TEM applications.Amorphous carbon films approximately 1000 Å in thickness were prepared using conventional arc evaporation and mounted on Ti, Mo, and W grids. The specimens were then placed in a UHV (∼2xl0-8 torr) electron microscope and observed continuously in-situ during their exposure to temperatures greater than 800°C(5). In this study it was found that carbides formed with all specimens after short times of exposure at 900°C. The micrographs in Fig.