In situ high-resolution Electron Microscopy

In recent years, there have been many dramatic recordings of dynamic behavior, taken at the atomic level by high-resolution electron microscopy. However in the majority of cases, reliance has been placed on the imaging electron beam to bring about the changes in question. There are many disadvantages to this approach, not the least of which is the lack of experimental control available to the operator. Accordingly we have developed the application of a heating holder to achieve stable elevated temperatures at which reactions can be followed under atomic imaging conditions. This article briefly reviews our progress to-date.Our microscope system is quite conventional, showing that there is no major impediment to hot-stage HREM. We have employed a Philips EM 430 ST (300kV) instrument equipped with a Gatan image pick-up device and a commercial video-recorder. The heating holder is the Philips single tilt sideentry model (PW 6592) which we have found works well up to about 875°C. Of course a double tilt holder is preferable but we overcome the tilting limitations by judicious positioning of cross-section specimens. Image stability can be achieved by heating to a temperature below that of the observation for several minutes before "ramping up" to the desired level.