UHV-TEM

Ultra high vacuum transmission electron microscopy

Description of Microscope The microscope is a Hitachi H-9000 UHV microscope operating at an accelerating voltage of 300kV and a base pressure of 2x10-10 Torr. It was modified by inserting capillary tubes into holes drilled through the upper polepiece allowing gases to be introduced into the specimen area. The maximum pressure which can be sustained during observation is ~10-5 Torr. A small electron beam evaporator is mounted above the polepiece allowing metals to be deposited during observation. Finally, several specimen holders have been constructed allowing heating of the specimen by direct current as well as three-electrode biasing for electrochemical measurements. The heating holders are capable of both transmission and reflection geometry. A Gatan Imaging Filter allows us to record zero-loss images or perform elemental analysis if required. Images are recorded on plates, or at 30 frames per second onto a Gatan off-axis CCD camera, or at up to 12 frames per second onto a charge transfer CCD beyond the energy filter. The specimen can be transferred under UHV between the microscope column and a series of adjacent chambers which were designed and constructed in-house. The first (transfer) chamber can store four specimen holders and contains a small removable evaporator as well as electrical connections. The second has a focused ion beam gun, electron gun and Auger detector, and the stage can tilt, shift and heat the specimen. A window allows the specimen temperature to be calibrated using infra red or optical pyrometry. The third chamber contains two 3kW electron beam evaporators, an Ar ion sputter gun and several smaller thermal evaporators. Each chamber has several unused ports and can be modified depending on the experiment.