On-Chip Thermionic Electron Sources Based on Graphene and Carbon Nanotubes

Abstract

Miniature electron sources fabricated on a chip by microfabrication technologies are highly desired for vacuum micro/nan o-electronics applications. While previous efforts to on-chip e lectron sources were mainly devoted to field electron sources, I will talk on our efforts to on-chip thermionic electron sourc es based on graphene and carbon nanotubes. Due to good ele ctrical conductivity and high melting temperature, graphene a nd carbon nanotube (CNT) are ideal materials for filaments o f thermionic electron emission. We studied thermionic emissi on from a CNT heated by Joule-heating, and found that its th ermionic emission deviates from classical Richardson's law. <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sup> Thermionic emission current from a CNT was measured to b e more than 1 order of magnitude larger than that predicted b y Richardson's law. The phenomenon is attributed to be the e mission of hot electrons generated in CNT under electrical dr ive. <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> By employing CNT and graphene as thermionic filamen ts, we have realized the scaling down of thermionic emission source to the microscale on a chip by using microfabrication t echnologies. <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3-5</sup> Compared to field emission sources, on-chip t hermionic electron sources show advantages of low working voltage, good controllability and low vacuum requirement for stable emission. On-chip thermionic electron sources also ha ve a short turn-on/off response time of less than 1 μs, much s horter than their bulky counterparts. On-chip thermionic elect ron sources open a new route for realizing miniature electron sources for vacuum micro/nano-electronics applications.