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Electron Emission from Cx(BN) Graphite Petals

posted Jun 14, 2013, 8:48 AM by Timothy Fisher   [ updated Jun 18, 2013, 10:20 AM by Patrick McCarthy ]

Student: Patrick McCarthy

Faculty: Tim Fisher

Summary: Carbon based nanomaterials have been studied extensively as energy generation devices via thermionic and photoemission characterization of carbon nanotubes, graphene petals, and chemical modifications thereof. Potassium intercalated graphene petals exhibit a low work function (energy barrier) and high electron emission intensity. Good optical and thermal properties of the carbon structures reinforces the potential of these materials. However, thermionic emission from these structures is limited by the deintercalation of potassium from between planar layers of graphene at elevated temperatures. This work will attempt to limit deintercalation of potassium and increase thermal stability via boron nitride (BN) modification of graphene petals. BN is an analogue of graphene (i.e. consisting of stacks of planar, hexagonal atomic layers). Limited mobility of oxygen within Cx(BN) has been demonstrated leading to decreased carbon burnoff. This may in turn limit potassium mobility within the lattice allowing for increased stability at high temperatures. Electron energy distributions (EEDs) will be recorded utilizing a hemispherical energy analyzer (HEA) with current density measurements to be taken as well. Initial EEDs recording exhibit trends of increased thermal stability.

Results from Cx(BN) studies indicate that while boron nitride modification produces multiple work function peaks while retaining a low work function emission peak, it rapidly losses emission intensity above 580 K. Conversely, non-modified graphitic petals intercalated with potassium show remarkable increases in emission intensity up to 980 K.

Image: Photoemission electron energy distributions resulting from solar simulator illumination of potassium intercalated graphitic petals, Cx(BN) petals, and hydrogen plasma treated Cx(BN) petals.

Representative Paper: http://avspublications.org/jvstb/resource/1/jvtbd9/v28/i2/p423_s1