Specimen heating stage with in-situ evaporator in UHV-STEM for the observation and characterization of monolayered superstructures
In-situ evaporating experiments on solid surfaces become meaningful only when the evaporation takes place after the surface of the object is fully cleaned in ultra high vacuum (UHV). A specimen heating stage is usually used for the cleaning process.For the observation of single heavy atom superstructures at atomic resolution in UHV, we have constructed a new specimen heating stage equipped with an insitu evaporator. The device is built into the specimen ante-chamber of the high-resolution UHV-STEM as shown in Figures 1 and 2. The vacuum of the chamber has been tested at 4 × 10-10 torr. with two 20 ℓ/ sec ion pumps attached close to the chamber. The vacuum of the STEM column is better than 1 × 10-10 torr. The heating stage is built into the specimen holder so that direct heating of the specimen is possible. In the detail shown in Figure 2, a thin specimen is mounted between two supporting grids which are then fastened together by two semi-circular tantalum clips. These clips are also used as contacts which carry the current to heat the specimen directly.