Monolithic multifinger lateral nanodiamond electron emission devices
Chemical-vapor-deposited (CVD) diamond is an excellent electron emission material due to its low electron affinity, robust mechanical and chemical properties, high thermal conductivity, and ability to withstand high temperature and radiation. Nanocrystalline diamond, also known as nanodiamond, is an emerging form of CVD diamond which vastly expanding its applicability in vacuum electronics. Apart from the assets of the conventional CVD diamond, it possesses certain distinct properties which include smaller grain-size, high volume density of grain-boundaries, smoother surface morphology, n-type dopant incorporation and increased sp2-carbon content. However, the utilization of nanodiamond in vacuum micro/nanoelectronics has been limited by the complexity associated with its process integration. The purpose of my research is to develop a reliable process technique to fabricate efficient nanodiamond lateral electron emission devices operable at low voltage with high emission current for applications in vacuum microelectronics and integrated-circuits. To achieve this goal, first, a well-controlled process to realize useful and potential nanodiamond electron emitter structures in array configurations using electron beam lithography (EBL) and plasma etching techniques has been developed. Detail study includes optimization of processing parameters for EBL, metal-mask deposition and nanodiamond dry etching. The main part of the research includes the application of these recently developed process techniques for the design, fabrication and characterization of micro/nanopatterned nanodiamond lateral field emission devices which include sub-micron gap two-terminal and multifinger three-terminal structures. 140-fingered nanodiamond lateral diode has been achieved for the first time with 300nm interelectrode distance. On the other hand, the three-terminal structure is composed of 140 finger-like emitters with integrated anode and gate, which also has never been reported before. The electrical characteristics of these fabricated nanodiamond vacuum lateral field emission devices demonstrated promising behavior with very low turn-on voltage with high and stable emission current. It has also been observed for the first time that three emission mechanisms dominated at different potential levels. The three-terminal structure showed anode current enhancement and suppression behavior by changing gate bias. These developments in the field of nanotechnology signify the integration of vacuum electronics with the well-established IC process techniques favorable for high-speed and high-power, IC-compatible, extreme-environment vacuum micro/nanoelectronics applications.