| dc.description.abstract | CVD diamond is an excellent material for field emission with low electron affinity, robust mechanical and chemical properties, high thermal conductivity, and ability to withstand extreme temperature and radiation. However, utilization of the properties of diamond in vacuum micro/nanoelectronics and other fields has been limited by the complexity associated with its process integration. Nanocrystalline diamond is an emerging form of the material, vastly expanding its utility for applications ranging from electronics to tribology. Its distinct properties, including small grain size, controlled amounts of sp^2-carbon, high electrical conductivity from n-type dopant (nitrogen) incorporation, and a smooth, uniform surface morphology, offer wide latitude for materials processing and integration for device formation. This research is focused on the design, fabrication, and characterization of nanodiamond vacuum microelectronic devices, specifically on monolithic lateral field emission diodes, triodes, and transistors, developed using a consistent process scheme, paralleling semiconductor IC fabrication technology.
Reliable process techniques have been developed to grow and micropattern nitrogen-incorporated nanodiamond thin films, with grain size as small as 5 nm, and integrated in the fabrication of lateral field emitter array (FEA) devices. A lithographically controlled finger-like emitter geometry and small interelectrode spacing in a low-capacitance integrated structure, achieved by single-mask processing are attributes of the lateral devices.
The nanodiamond lateral emitters demonstrate promising characteristics of low turn-on voltage (~ 5 V) and threshold electric field (1.1 V/ìm), high emission current (25 mA) and current density (183 µA/finger), with reliable and stable performance. These electron devices exhibit high diode rectification (> 10^4), and a large transconductance (0.3 µS/finger) as a gated microtriode. The monolithic vacuum transistor, in planar lateral configuration, shows negligible gate intercepted current (Ig/Ia ratio ~ 0.001 %), current saturation, and large amplification factor of ~ 200. Moreover, this research has led to the development of the first vacuum microelectronic technology with operational temperature immunity (> 350 C) and radiation hardness (tested upto 20 MRad total dose and 4.4x10^13 neutrons/cm^2 exposure). These diamond vacuum device characteristics signify a novel, efficient means of accomplishing IC-compatible electronics, suited for high-speed, high-frequency and high-power, extreme-environment applications. | |
