Boron sulfide chemical vapor deposition: A new method for the efficient and low-temperature growth of boron nitride nanotubes

Boron oxide chemical vapor deposition (BOCVD) is renowned for facilitating the synthesis of boron nitride nanotubes (BNNTs). However, it employs a rather high growth temperature. Herein, we describe boron sulfide chemical vapor deposition (BSCVD), a novel method we have developed for the efficient and low-temperature synthesis of BNNTs. BSCVD is based on the principle of a metal (Me) sulfide and boron (B) reacting to form an Me–B–S system (where S = sulfur). This system has the advantages of a low melting point, high evaporation rate, and increased reactivity with ammonia. Thus, the growth temperature of BNNTs in BSCVD is approximately 100°C lower than that in BOCVD. Additionally, the nucleation time of catalyst droplets in BSCVD is 25 %–40 % of that in BOCVD, while the growth rate of BNNTs in BSCVD is 1.4–1.7 times faster than that in BOCVD. Moreover, the addition of S powder in the Me–B–S system increases the nucleation probability, which in turn reduces the BNNT growth temperature by another 100°C. Meanwhile, the minimum growth temperature of 800°C is relatively low compared to other growth temperatures in the thermal CVD growth domain. In summary, the BSCVD method substantially enhances the low-temperature synthesis of BNNTs and can serve as a new basis for low-melting-point growth systems.