Fabrication of Patterned Carbon Nanotube Field Emission Surfaces on SiC Substrates
- PDF / 1,198,235 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 22 Downloads / 161 Views
Fabrication of Patterned Carbon Nanotube Field Emission Surfaces on SiC Substrates Michael Pochet*,1, Jonathon Campbell1, Ronald Coutu1, Steven Fairchild2, and John Boeckl2 1 Department of Electrical and Computer Engineering, Air Force Institute of Technology, WrightPatterson Air Force Base, OH 45433, USA 2 Air Force Research Laboratory, Materials and Manufacturing Directorate, AFRL/RXPS, Wright-Patterson Air Force Base, OH 45433, USA ABSTRACT This work focuses on the patterning of SiC substrates prior to carbon nanotube (CNT) formation using the surface decomposition growth method for the purpose of improving the field emission capabilities of the resultant CNT film. The thermal decomposition of silicon carbide (SiC) substrates is an established approach to create highly dense arrays of vertically aligned CNTs. The attractiveness of this growth approach is that the CNTs form without the aid of a catalyst metal, yielding potentially defect free CNTs ideal for various applications. Due to the high temperature anneals (1400-1700oC) and moderate vacuum conditions (10-2 – 10-5 Torr) necessary for the thermal decomposition process to initiate on the SiC substrate, patterning CNT outcroppings ideal for enhancing the surface’s field emission properties is more difficult when compared to metal catalyst based chemical vapor deposition growth processes on silicon substrates. The intent of the SiC patterning is to reduce field screening effects between neighboring emission sites during field emission while maintaining a high emission site density. Specifically, the SiC substrate is etched to form μm scale pillars on the SiC surface. Experimental findings show that SiC substrates patterned with μm scale pillars can be decomposed to form CNT topped field emission sites, yielding a field emission substrate that outperforms a non-patterned SiC/CNT film. A turn-on electric field of 4.0 V/μm was measured. INTRODUCTION Numerous manuscripts found in the literature report that CNTs have excellent field emission properties, emitting high electron current densities at low electric fields [1-5]. The potential for extraordinary field emission from CNTs owes to their high aspect ratio and electrical conductivity [6]. The primary growth method used in CNT based emitter fabrication is through metal catalyzed chemical vapor deposition (CVD). While metal catalyzed CVD growth approaches are ideal in that they form whisker-like morphologies ideal for field emission, there is an unwanted presence of the metal catalyst particles in the CNT product, degrading/altering the characteristic properties of the CNTs [7]. It is this unwanted result of catalyst based CNT growth approaches that has driven interest in methods that form CNTs without the use of catalyst metals and ideally a higher degree of purity. One approach to catalyst metal free growth of CNTs has been achieved by the thermal decomposition of SiC and has been reported by several research groups [8-10]. In this work, SiC samples are patterned to create elevated emission sites in an attempt t
Data Loading...
