Environmental TEM, ETEM

The Environmental TEM (ETEM) is a TEM which enables us to observe specimens under a gas-controlled environment. A volume around the specimen is filled with gases so that the pressure of the volume is kept higher than that of the TEM column. The ETEM is classified into two types; isolation-film type and differential pumping type. The former ETEM is equipped with an (gas) environmental cell (EC) in the specimen holder. A passage for gas introduction and evacuation is connected to the EC. There are holes above and below the EC to allow electron-beam transmission. To prevent gas leakage into the microscope column, thin films such as carbon or silicon nitride films (called "insulation films") are sealed to the holes. The latter ETEM is designed to introduce gasses into the specimen chamber in the microscope column. To prevent vacuum deterioration of the column caused by gas diffusion, differential pumping is adopted. For example, multiple orifices are incorporated into the upper and lower parts of the polepieces (on the optical axis). This construction enables differential pumping of spaces isolated by the respective orifices. The ETEM is used for in-situ observation of reaction processes between the specimen and the introduced gasses, observation of water-containing specimens, etc.

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