Osmium-metal coating device using hollow-cathode plasma CVD method

A novel osmium-metal coating device for SEM observation has been developed to prevent negative charge build-up on specimens by applying the hollow-cathode low voltage discharge plasma chemical vapour deposition (CVD) method. The CVD method using the hollow-cathode offers the following advantages. (i) The method can deposit osmium-metal at very low discharge voltage that is as low as half of that of the planar parallel electrode method. Therefore, the method avoids damage due to ion bombardment during the coating process. (ii) The method can minimize the quantity of the OsO4 gas by introducing directly into the hollow-cathode. This feature is important to prevent the air pollution caused by the purged gas. (iii) A large coating area is guaranteed because the Os ion is filled in the hollow-cathode where the specimen is holed. (iv) The lower discharge voltage can be used by mixing Ar, N2 or air with the OsO4 gas as the environmental gas in the chamber. (v) The hybrid coating is also available by lining the appropriate metal material such as platinum (Pt) on the surface of the inside of the hollow-cathode. The method uses the plasma CVD of Os metal as well as the ion-sputter deposition of the lined metal.