A method for preparing cross sectional transmission electron microscopy (TEM) specimens using thin film processing techniques is described. Optical lithography is used to pattern lines of photoresist on the sample, followed by shadow evaporation of Al against the resist sidewalls. Removal of the resist leaves free standing, 100 nm wide metal lines on the surface. A selective, anisotropic reactive ion etch into the substrate then produces 1.5 μm tall, 100 μm wide walls, which, when turned on their sides, are sufficiently thin to allow transmission of high energy electrons in the TEM. This technique permits very specific, as well as very large, regions of a sample to be thinned for cross sectional examination. The processing steps are straightforward and may be easily adapted to other materials.