Electron Emission Mechanism of Doped CVD Diamond Characterised by Combined XPS/UPS/FES System

摘要

Clarification on electron emission mechanism of diamond is one essential approach to realize the clear vision of vacuum nano-electronics; to replace the thermal cathode by a "cold" emitting cathode. Electric field of less than 5 V/μm is enough to extract electrons from doped chemical vapour deposited (CVD) diamond, whereas field of one to two orders of magnitude higher is needed to extract electrons from metal emitter tips [1]. Diamond has various advantages as an electron emitter in addition to the low-threshold voltage, negative electron affinity (NEA), high thermal conductivity, high mechanical hardness, and high chemical stability. The difficulty in clarification of electron emission mechanism is the factor preventing diamond from being used in practical applications. Quite a few numbers of possible mechanisms were proposed to better understand the origin and properties of the observed emission from diamond [2-5]. Most of these mechanisms were, however, based on the results obtained by conventional I (Emission current)-V (Anode voltage) characteristics. Energy distribution of the field-emitted electrons is essential in direct clarification of the mechanism. It enables one to draw the energy band diagram of emitting diamond. Our ultimate goal is to draw the energy band diagram of emitting diamond using the electron energy distribution obtained from combined spectroscopy of XPS/UPS/FES. In this study, combined XPS/UPS/FES system (Figure 1) was used to characterize the electron emission mechanism of doped CVD diamond.