Orientation-controlled, low-temperature plasma growth and applications of h-BN nanosheets

Abstract

Dimensionality and orientation of hexagonal boron nitride (h-BN) nanosheets are promising to create and control their unique properties for diverse applications. However, low-temperature deposition of vertically oriented h-BN nanosheets is a significant challenge. Here we report on the low-temperature plasma synthesis of maze-like h-BN nanowalls (BNNWs) from a mixture of triethylamine borane (TEAB) and ammonia at temperatures as low as 400 °C. The maze-like BNNWs contained vertically aligned stacks of h-BN nanosheets. Wavy h-BN nanowalls with randomly oriented nanocrystalline structure are also fabricated. Simple and effective control of morphological type of BNNWs by the deposition temperature is demonstrated. Despite the lower synthesis temperature, thermal stability and oxidation resistivity of the maze-like BNNWs are higher than for the wavy nanowalls. The structure and oxidation of the nanowalls was found to be the critical factor for their thermal stability and controlled luminescence properties. Cytotoxic study demonstrated significant antibacterial effect of both maze-like and wavy h-BN nanowalls against E. coli. The reported results reveal a significant potential of h-BN nanowalls for a broad range of applications from electronics to biomedicine.

Chemical vapour deposition of sp2-hybridised B-C-N materials from organoborons

“…NW were the most common and their morphology varied with the deposition parameters. It is interesting to observe growth of NW at such low temperatures (300 °C ≤ T ≤ 400 °C), but it is consistent with the minimal deposition temperatures reported by Merenkov et al 165 for BN NW deposition. The morphology of the NW could be varied from so-called maze-like (i.e.…”

“…As mentioned earlier, first reports of nanowalls are related to the study of carbon nanostructures. 158,159 BN [160][161][162][163][164][165] and BCxNy 166 nanowalls were reported later on. The two preferred synthesis methods for NW are microwave plasma CVD (MW-PACVD) and thermal CVD.…”

“…Smooth films were obtained with two sets of conditions. The morphology of the smooth films deposited for plasma power of 2325 W, 238 sccm total flow and N/Ar = 13.3 could be explained by too low deposition temperatures as in 165 , induced by cooling by high N2 flow. This is consistent with the high growth rate and high oxygen content.…”

“…The orientation of the NW is thought to be due to lateral field effects 167 or crowding effects (i.e. the initial clusters grow flat until they meet and then curl upward to grow vertically) 161,165,168,169 . The suppression of other growth directions can be explained by shadowing of smaller sheets 171 and by support from adjacent sheets 170 .…”

“…Nanowalls have high surface-to-volume ratio and are therefore of interest for storage and catalytic applications. BN NW have interesting nonwetting properties (superhydrophobicity) 160,161 and as most nanostructures, BN and BCN NW are interesting for electronic 163 and optoelectronic 160,[163][164][165][166] applications.…”