SIMPLE METHOD FOR DETERMINING THE ABSOLUTE SENSE OF IMAGE ROTATION IN A TRANSMISSION ELECTRON-MICROSCOPE

The TEM images of a specimen are generally rotated by a finite angle with respect to their associated diffraction patterns. A simple method for determining the absolute sense of the image rotation was developed using the topographical imaging approach. This method is extremely easy to use for image rotation calibration and does not require special samples, such as molybdenum trioxide. Topographical images can be obtained by displacing in the direction of the operating diffraction vector, gBAR, to include approximately half of the transmitted beam. Inside this aperture, there will be refracted beams arising from the thin specimen edge which will be seen with bright contrast in the image. The orientation of the bright/dark edge images obtained by this topographical imaging technique allows one to determine the absolute sense of the image rotation by direct comparison of the image and diffraction pattern.