In situ HVEM study on copper oxidation using an improved environmental cell

A window-type environmental cell that can be used over the temperature range from room temperature to ∼1000 K was improved by incorporating a new window material that increases resolution and contrast in high voltage electron microscopy. With this improvement, the resolution was a few nanometers and the maximum pressure in the cell was ∼1.3 x 10 4 Pa. Using this new window-type environmental cell, oxidation of copper and reduction of copper oxides, which occur through gas (oxygen or hydrogen-solid (copper metal) reactions, have been successfully observed in situ, i.e. the formation process of oxides (Cu → Cu 2 O → CuO) and their subsequent reduction (CuO → Cu) in the cell. The growth process of CuO whiskers on a thick (50 μm) Cu film was also observed in situ. It was found that whisker growth occurs at the tips of whiskers.