Optimizing the environment for sub-0.2 nm scanning transmission electron microscopy.

Sub-0.2 nm probes can now be readily obtained on Schottky field-emission microscopes. However, environmental instabilities are proving to be the limiting factors for atomic resolution spectroscopy and distortion-free annular-dark field imaging. This is a result of the long acquisition times and the serial nature of the scanning system where instabilities result in image distortions rather than reductions in contrast. Troubleshooting the most common environmental problems is discussed here. In addition to the expected sensitivity to mechanical vibration, electromagnetic interference and temperature variations, air-pressure fluctuations are found to have a significant impact on microscopes with side-entry goiniometers.