Recently, the CMSC acquired a variable pressure scanning electron microscope (VP-SEM), a Zeiss EVO LS 25. The VP-SEM is able to operate under high vacuum conditions like a typical SEM, but also has the capability of operating under elevated pressures (10-400 Pa). The advantage of operating at elevated pressures is that the sample requirements that can normally hinder traditional SEM use (insulating and/or out-gassing specimens) are lifted and a wide variety of specimens can be examined. The microscope operates in three pressure modes: High Vacuum for traditional SEM operations; Variable Pressure, where 10-80 Pa of nitrogen acts to neutralize surface charging; and Extended Pressure, where 80-400 Pa of water is introduced for hydrated specimens.
Features of the VP-SEM include:
1.A five quadrant back scatter detector.
2.A Peltier cooling stage for precise control of humidity above the sample.
3.A heating stage capable of reaching 1200 C.
4.A large specimen chamber that is able to accommodate specimens up to 22 cm in diameter.
5.Energy Dispersive X-ray Detector of determining atomic compositions.