A new electron source which consists of microsize field emitter arrays attract strong attention for realizing new applications such as flat panel display, super-high frequency vacuum devices etc. Although the conventional field emitter that is usually a single crystal tungsten needle is operated under an ultra-high vacuum condition, new microsize field emitter arrays are required to be prepared by deposition methods and to be operated under a normal vacuum condition. Therefore, the researches on the new materials and structures for the development of microsize field emitter arrays have been needed. The selection of a low work function material as an emitter material is a prospective method to realize a stable operation of microsize field emitter array.