Structural Observation of Electron Emitting Tip Using UHV STM

Electron emitting tip is widely used in many research ˆelds such as microfabrication, electron microscopy, surface science and so on. There are mainly three types of electron emitter as thermionic, ˆeld-emission and Schottky electron emitter. Because of the high stability with large emission current, tungsten〈100〉single crystal coated with ZrO2 is widely used as Schottky electron emitter of an electron microscope. In order to develop a new technique for evaluating electron emitter, we thought that it was possible to observe the surface topographic structures of the electron emitting tip with a scanning probe microscope and succeeded in observing the nanostructure of the electron emitting tip in air. In this study, we have tried to observe tip nanostructure using ultra high vacuum scanning tunneling microscope (UHVSTM), because electron emitter is generally used under UHV condition. Using UHVSTM, high resolution STM images which are related to scanning electron microscope images were acquired. This indicated that UHVSTM could be a plausible tool for electron tip characterization.