Diamond microemitters - The new frontier of electron field emissions and beyond

Chemical vapor deposited (CVD) diamond or related carbon materials are exce llent materials for electron field emitters because of their low or negativ e electron affinity (NEA) and excellent mechanical and chemical properties. Many reports to date have dealt with nonuniform microstructures of diamond , diamond-like carbon (DLC) or other forms of carbon planar films and carbo n nanotubes. However, the "direct" usage of diamond or other forms of carbo n emitters leads to nonuniform emitter microstructures, uncontrolled random ly scattered emission sites, and inconsistent emission behaviors. Consequen tly, practical engineering design and control of emitter structures are nee ded to fully exploit the potential usage of diamond/carbon field emissions. In this paper, a well-engineered molding process for the fabrication of di amond field emitter cathodes and devices is presented. Practical modificati ons involving the sp? content, surface treatment, boron doping, and tip sha rpening to further enhance diamond field emission are discussed. Well-contr olled ultrasharp diamond tips with a radius of curvature of less than 5 nm have been achieved and show significant improvement in emission characteris tics. Discussion of this enhanced emission in diamond microtips is presente d in accordance with the results of analysis of emission behavior. The deve lopment of high site density of uniform diamond microtip arrays is presente d. We also report the development of self-aligned gate diamond emitter diod es and triodes using silicon-based microelectromechanical system (MEMS) pro cessing technology and achieve totally monolithic diamond field emitter dev ices on silicon wafers. Preliminary results in the triode configuration dem onstrate promising transistor characteristics suitable for vacuum microelec tronic applications. Theoretical analysis and modeling of the thermodynamic s of diamond field emissions suggest the potential usage of diamond emitter s beyond the conventional vacuum microelectronics to encompass usage such a s microcoolers and power generators in MEMS applications and beyond.