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With its low work function and high mechanical strength, the LaB6/VB2 eutectic system is an interesting candidate for high performance thermionic emitters. For the development of device applications, it is important to understand the origin, value, and spatial distribution of the work function in this system. Here we combine thermal emission electron microscopy and low energy electron microscopy with...
The oxide/semiconductor structure is key to controlling current in electronic devices and HfO2 is a common gate material in conventional electronic devices due to its favorable dielectric properties. Graphene devices also require insulating gates. We demonstrate a unique direct growth approach to obtain the bottom gate structure (graphene/HfO2/n-SiC). The present approach involves transfer of graphene...
LaB6 eutectic materials show promise as a replacement for common thermionic cathode materials. This eutectic system belongs to a class of materials referred to as directionally solidified eutectics (DSEs). LaB6 DSEs consist of a LaB6 matrix with a second phase, a metal di-boride, forming cylindrical rods in the matrix. Previous investigations on this material were focused on its use as a high temperature...
Field emission (FE) cathodes made from carbon nanotube (CNT) fibers have demonstrated high emission currents, low turn-on voltages, long lifetimes and offer considerable potential for use as electron sources for vacuum electronic devices. CNT fibers were fabricated by wet-spinning of pre-made CNTs1 and consist of CNT fibrils held together by van der Waals forces. The fibers were 50μm in diameter and...
Electric Hybrid Lasers (EHL) combines the benefits of a solid state laser (SSL) and a gas phase system. EHLs have the electrical capacity of an SSL and the thermal management and beam quality of a gaseous lasing medium. Researchers at Emory University have developed a novel EHL.1 A three-level EHL is being developed that utilizes a capacitively coupled RF discharge to produce metastable excited states...
Laser assisted electron emission from a free standing, non-aligned carbon nanotube film is observed with low power (<100 mW) continuous wave (785 nm) laser excitation. An increase in emission current by 330 times is realized.
Electric Hybrid Lasers (EHL) are of great interest for commercial and government application due to their ability to combine the benefits of a solid state laser (SSL) with the benefits of a gas phase system. EHLs have the electrical capacity of an SSL and the thermal management and beam quality of a gaseous lasing medium. Recently, researchers at Emory University have developed a novel EHL.1 The Discharge...
Field emission (FE) cathodes made from carbon nanotube (CNT) fibers have demonstrated high emission currents, low turn-on voltages, long lifetimes and offer considerable potential for use as electron sources for vacuum electronic devices. CNT fibers were fabricated by wet-spinning of pre-made CNTs1 and consist of CNT fibrils held together by van der Waals forces. The fibers were 10–100 µm in diameter...
There has been a recent resurgence of interest in the development of high power microwave and terahertz (THz) sources and amplifiers. High power microwave and THz amplifiers have the potential to vastly improve a number of applications: high data rate communications, concealed weapon and threat detection, remote high resolution imaging spectroscopy of airborne chemicals, and biomedical diagnostics...
High direct currents of 2.0 mAmps for a 15 micron diameter single walled nanotube (SWNT) fiber were achieved. Highly aligned, dense SWNT morphology in the fiber was demonstrated to reduce threshold emission and improve resilience to Joule heating. SWNT fibers were exposed to ion bombardment and the effects on emission were evaluated.
High power terahertz (THz) sources and amplifiers hold the potential to greatly improve remote sensing and high bandwidth communication. To enable these applications, a Traveling Wave Tube (TWT) operating at 0.22 THz and a multi-cathode Field Emission (FE) electron gun are developed and characterized using a Particle-in-Cell simulation. Three candidate high current density cathode materials, Halfnium...
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