Patterned Growth of Long and Clean Boron Nitride Nanotubes on Substrates
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1204-K08-03
Patterned Growth of Long and Clean Boron Nitride Nanotubes on Substrates Chee Huei Lee1, Ming Xie1, Jiesheng Wang1, Russell E. Cook2, and Yoke Khin Yap1 1 2
Michigan Technological University, Houghton, MI 49931, U.S.A. Electron Microscopy Center, Argonne National Laboratory, Argonne, IL 60439, U.S.A.
ABSTRACT For the first time, patterned growth of boron nitride nanotubes (BNNTs) on Si substrates has been achieved by catalytic chemical vapor deposition (CCVD). Following the boron oxide chemical pathway and our growth vapor trapping approach, high quality and quantity BNNTs can be produced. Effective catalysts have been found to facilitate the growth of BNNTs, while some critical parameters of the synthesis have also been identified to control the quality and density. The success of patterned growth of high quality BNNTs not only explains the roles of the effective catalysts during the synthesis process, but could also be of technologically important for future device fabrication.
INTRODUCTION Boron nitride nanotubes (BNNTs) have gained more research interest in the recent years due to their interesting properties. BNNTs have almost identical structure to carbon nanotubes (CNTs), in which both are formed by seamless tubular structure with strong sp2 bonded hexagonal network. On the other hand, unlike their C counterpart, BNNTs possess a wide bandgap of ~5.5 eV, which is almost insensitive to the number of walls, diameters, and chiralities [1]. In addition, BNNTs are good in mechanical properties and thermal conductivity [2, 3]. They are also chemically stable to oxidation up to 1000 °C [4]. Besides, modification of the band gap might be possible via several approaches, such as doping [3, 5], the giant Stack effect [6], and deformation [7]. All these fascinating possibilities make BNNTs potentially useful in deep-UV optoelectronic applications, high-temperatures and high-power electronics, as well as their use as boron carrier in boron neutron capture therapy [8]. BNNTs are also attractive for insulating mechanical and reinforcement applications [9]. Synthesis of BNNTs is challenging compared to that of CNTs due to the needs of much higher growth temperatures and complicated chemistry. This has prevented the applications of BNNTs. By far, BNNTs have been synthesized by various methods, including arc-discharge [10, 11], laser ablation/vaporaization [12, 13], BN substitution method from CNT templates [14], chemical vapor deposition (CVD) using borazine [15, 16], induction heating boron oxide CVD (BOCVD) [17, 18], as well as ball milling [19]. Among these synthesis techniques, significant progress has been produced by BOCVD for the mass production of multiwall BNNTs and led to potential applications [12, 13]. Nevertheless, this technique requires an induction furnace with specific design for achieve high growth temperatures (usually >1500 oC) and high temperature gradients. Thus direct growth of BNNTs on Si based substrates is prevented by the BOCVD approach. We previously reported low temperature growth
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