Regensburg 2013 – scientific programme
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MM: Fachverband Metall- und Materialphysik
MM 15: Poster Session
MM 15.13: Poster
Monday, March 11, 2013, 18:00–20:00, Poster E
Characterization of Pulsed CNT Field Emitters for Medical Imaging — •Daniela Leberl1,2, Bernhard Hensel2, and Sandro Francesco Tedde1 — 1Siemens AG, Corporate Technology, Erlangen, Germany — 2Center for Medical Physics and Engineering, University Erlangen-Nuremberg, Erlangen, Germany
Cold electron sources for X-ray applications would be beneficial for reduced acquisition time and improved image quality compared to thermionic emitters, today’s state of the art. Carbon nanotubes (CNTs) are a promising material for field emission applications due to the high aspect ratio and high electrical and thermal conductivity. For motion-free 3D image acquisition, short electron pulses of many individual sources are necessary. Thus it is important to investigate the field emitter characteristics and stability under pulsed conditions.
Here we report on electrical characterization of multi-walled CNTs grown by thermal chemical vapour deposition on stainless steel substrates. We studied the dependence of the IV characteristics and emitter stability on pressure, pulse-on time and duty cycle. All investigations have been carried out on samples with high field emission currents up to 126 mA (220 mA/cm2) and extremely long lifetimes up to 200 cumulative hours.
We found out that the emitter degradation is an important parameter for the application in medical X-ray systems. We discuss potential degradation mechanisms and present the correlation with threshold field and field enhancement factor, calculated with the Fowler-Nordheim theory of field emission.