Field Emission Properties of Ball-Like Nano-Carbon Thin Films Deposited on Mo Films with Accidented Topography

Ball-like nano-carbon thin films (BNCTs) are grown on Mo layers by microwave plasma chemical vapour deposition (MPCVD) system. The Mo layers are deposited on ceramic substrates by electron beam deposition method and are pretreated by ultrasonically scratching. The optimization effects of ultrasonically scratching pretreatment on the surface micro-structures of carbon films are studied. It is found from field-emission scanning electron microscope (FE-SEM) images and Raman spectra that the surface structures of the carbon films deposited on Mo pretreated are improved, which are composed of highly uniform nano-structured carbon balls with considerable disorder structures. Field emission (FE) measurements are carried out using a diode structure. The experimental results indicate that the BNCTs exhibit good FE properties, which have the turn on field of 1.56V/μm, and the current density of 1.0mA/cm² at electric field of 4.0V/μm, the uniformly distributed emission site density from a broad well-proportioned emission area of 4cm² are also obtained. Linearity is observed in Fowler--Nordheim (F-N) plots in higher field region, and the possible emission mechanism of BNCTs is discussed.