EM of diamond-coated molybdenum field emission cathodes

Abstract

Molybdenum is a common metal used to fabricate field emission devices.1-2 However, during extended operation, Mo cathodes exhibit current instabilities, which are thought to arise from adsorption of contaminants on the emitter surface. Coating Mo field emitters with diamond may enhance the current stability, as well as the total emission current. An understanding of the diamond nucleation mechanism is crucial for depositing consistent, uniform coatings on the emitters, and therefore producing reliable devices. To the author's knowledge, little information exists about the mechanism of diamond nucleation on these highly curved Mo surfaces.In order to study the diamond nucleation mechanism, the morphology of the diamond coating and the structure of the diamond/Mo interface were analyzed by high resolution TEM. Emitters make excellent TEM specimens, since no further sample preparation is required after the diamond deposition; artifacts thus do not become an issue in interpreting the TEM results. Figure 1 shows that the films have a general morphology of clustered nanocrystalline particles.