Impact of growth parameters on the formation of carbon nanostructures through thermal deposition of silicon carbide
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Impact of growth parameters on the formation of carbon nanostructures through thermal deposition of silicon carbide Munson Anderson1, Michael Pochet1, Benji Maruyama2, Pavel Nikolaev2, Elizabeth Moore2, and John Boeckl2 1: Air Force Institute of Technology, Wright-Patterson Air Force Base, OH 45433 2. Air Force Research Laboratory, AFRL/RX, Wright-Patterson Air Force Base, OH 45433 ABSTRACT Carbon nanotube (CNT) and graphene films form on silicon carbon (SiC) using a metalcatalyst-free thermal decomposition approach. In this work, the growth conditions used in the decomposition process are varied to investigate their impact on the type and quality of carbon allotrope formed on the SiC substrate. The nanostructure growth is performed using two approaches, both of which involve intense heating (1250-1700oC) under moderate vacuum conditions (10-2 – 10-5 Torr) without the aid of carbon rich feed gases or metal catalysts commonly used in Chemical Vapor Deposition (CVD) growth approaches. The first growth method uses a graphite resistance furnace capable of annealing wafer-sized samples. The second approach uses a high-intensity laser to heat a micro-meter scale spot size. The high-intensity laser heats the illuminated area of the SiC substrate while under vacuum conditions, resulting in a small-scale growth process similar to the conventional resistance furnace technique. Unique to this micro-scale approach is that in situ Raman spectroscopy is performed yielding instantaneous characterization of the resultant carbon nanostructure as it is formed. The laser-induced growth mechanism enables the impact of varied background vacuum pressures and temperatures to be evaluated in situ. This work reports the findings for various parameter sets implemented during growth, and provides insight into the physical mechanism influencing the growth process. INTRODUCTION Today, microwave devices in the GHz bands are required for frequency agile radar and communication, and are commonly based on higher mobility group III-V semiconductor materials [1]. However, even today’s “fast” III-V materials have their limitations. Due to their extraordinary electrical properties, carbon nanostructures, namely CNTs and graphene, have become popular subjects of research [2, 3]. In order to reach faster speeds required for future applications, graphene and CNTs have been examined as potential alternatives to silicon. This work characterizes the carbon allotropes formed during the thermal decomposition of SiC. The conventional furnace based decomposition method involves the extreme heating (1200 – 1700°C) of a SiC substrate while under moderate vacuum conditions (10-3 – 10-5 Torr); the resultant carbon nanostructure formed is dependent on the growth conditions [4]. The attractiveness of this growth technique is the lack of catalyst metal needed to initiate carbon allotrope formation, yielding potentially defect free carbon allotropes. This growth method is unique in that the carbon nanostructures formed are conformal to all surfaces exposed to the intens
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