Time dependent decomposition of ammonia borane for the controlled production of 2D hexagonal boron nitride

Abstract

Ammonia borane (AB) is among the most promising precursors for the large-scale synthesis of hexagonal boron nitride (h-BN) by chemical vapour deposition (CVD). Its non-toxic and non-flammable properties make AB particularly attractive for industry. AB decomposition under CVD conditions, however, is complex and hence has hindered tailored h-BN production and its exploitation. To overcome this challenge, we report in-depth decomposition studies of AB under industrially safe growth conditions. In situ mass spectrometry revealed a time and temperature-dependent release of a plethora of NxBy-containing species and, as a result, significant changes of the N:B ratio during h-BN synthesis. Such fluctuations strongly influence the formation and morphology of 2D h-BN. By means of in situ gas monitoring and regulating the precursor temperature over time we achieve uniform release of volatile chemical species over many hours for the first time, paving the way towards the controlled, industrially viable production of h-BN.

Vapor–liquid–solid growth of large-area multilayer hexagonal boron nitride on dielectric substrates

“…Furthermore, as shown in Fig. 3f, the pole figures of the sapphire and h-BN films proved that the alignment of the h-BN layers on sapphire was [0001] h-BN|| [0001] sapphire, h-BN|| [11][12][13][14][15][16][17][18][19][20] sapphire, and [11][12][13][14][15][16][17][18][19][20] h-BN|| sapphire, consistent with previous reports 21,29 .…”

“…According to the corresponding FFT patterns of the as-grown h-BN and sapphire ( Fig. 3a insets), it was calculated that the [11][12][13][14][15][16][17][18][19][20] direction in the h-BN was well aligned to the direction in the sapphire. In addition, the atomic resolution and atomic fringes in the magnified high-resolution TEM images of h-BN and sapphire also confirmed the alignment ( Fig.…”

“…However, catalytic effects always yield thin h-BN films, e.g., a thickness of a few layers (<10 layers), which could not efficiently protect electronic 2D crystals from the disturbance in their surroundings. The existing fabrication approaches use flammable and toxic chemicals, including borazine (B 3 N 3 H 6 ) 16 , or complicated chemicals, such as ammonia borane (H 3 NBH 3 ) 20 , as reactive precursors. In addition, the wet transfer process from metallic surfaces to target substrates would probably degrade the quality of the h-BN and then limit its application in microelectronics.…”

A Peeling Approach for Integrated Manufacturing of Large Monolayer h-BN Crystals

“…38 In conjunction with our cold-wall CVD reactor system (base pressure < 2 × 10 -6 mbar, further details in Experimental Methods), a well-controlled precursor atmosphere can be maintained, in contrast to the use of ammonia borane, which can exhibit a complex and evolving decomposition profile especially for hot-wall CVD reactor conditions. 39 Our main findings relate to fundamental interactions with the catalytic growth substrate and hence are transferable to other B and N precursors. In particular, we note that while borazine represents a precursor with pre-defined stoichiometry (B:N = 1), it dissociates on the Pt surface.…”

The Onset of Dehydrogenation in Solid Ammonia Borane: An Ab Initio Metadynamics Study

“…The system can generate as much as one H 2 per formula unit and what is left is a disordered mixture of polymeric (‐H 2 BNH 2 ‐) n aminoboranes (PAB) that further decompose . In spite of intense experimental efforts, there is no general consensus on how dehydrogenation proceeds. In the early stages of dehydrogenation, the formation of diammoniate of diborane ([(NH 3 ) 2 BH 2 + ][BH 4 − ], DADB) and ammonia diborane (H 3 NBH 2 (μ‐H)BH 3 , AaDB) Figure b has been reported.…”