Field Emission Studies from Graphene Cold Cathodes

In recent years, graphene is being widely explored for cold cathode applications due to atomic thickness, excellent electrical conductivity, and high mechanical strength. In addition, the electrical properties can be tailored by substitutional dopant such as nitrogen or boron. In this context, field emission studies from electrophoretically fabricated pristine, boron doped, and nitrogen doped graphene cold cathodes have been carried out. The nitrogen doped graphene exhibits lower turn on electric field of 0.6 V/μm for drawing emission current density of 10 μA/cm2 than the pristine and boron doped graphene. For understanding the current delivering capability of nitrogen doped graphene without structural deformation, the field emission studies were performed inside transmission electron microscope. The studies reveal that the maximum amount of emission current that could be drawn is limited by the Joule heating effect causing structural deformation in the form of contraction/buckling of sheet. Furthermore, the reliability of the graphene cold cathodes under the harsh environment has been studied by irradiating specimens with 6 MeV electron beam by varying the electron fluence. Overall, the field emission turn on and noise characteristics are found to be electron fluence dependent. 

References:

. 	1.	Remarkable low-turn on field emission in Undoped, Nitrogen doped and Boron doped Graphene, Umesh A. Palnitkar, Ranjit V. Kashid, Mahendra A. More, Dilip S. Joag, Leela S. Panchakarla, and C. N. R. Rao, Applied Physics Letters 97, 063102, 2010.

2. 	Field emission characteristics of pristine and N-doped graphene measured by in-situ transmission electron microscopy, Ranjit V. Kashid, Mohd Yusop Zamri, Chisato Takahashi, Golap Kalita, Leela S. Panchakarla, Dilip S. Joag, Mahendra A. More, Masaki Tanemura, Journal of Applied Physics, 113, 214311, 2013.