Large-Scale Growth of High-Quality Hexagonal Boron Nitride Crystals at Atmospheric Pressure from an Fe–Cr Flux

Abstract

Single crystals of hexagonal boron nitride (hBN) have recently been envisioned for electronic, optoelectronic, and nanophotonic applications. In this study, the production of large-scale, high-quality hBN single crystals via precipitation from a new solvent composed of Fe and Cr was demonstrated to be viable at atmospheric pressure. The clear and colorless crystals have a maximum domain size of around 2 mm and a thickness of around 200 μm. The Raman spectra and photoluminescence emission spectra demonstrate that the crystals produced with this solvent are pure hBN phase, and with low defect and residual impurity concentrations. The use of an Fe−Cr mixture provides a lower cost alternative to the more common Ni−Cr solvent for growing large hBN of comparable quality.

Controlled synthesis of uniform multilayer hexagonal boron nitride films on Fe2B alloy

“…In recent years, layered h-BN akes, integrated with other layered materials for 2D heterostructure devices, were mechanically exfoliated from high quality h-BN bulk crystal, which was obtained under extremely high temperature and pressure for several days. 12,13 However, the limited size and inhomogeneous thickness hinder further development of 2D electronics and photonics. As the most promising technique, chemical vapor deposition (CVD) was employed to achieve large-area monolayer and few layer h-BN on metal or dielectric substrates by using ammonia borane (NH 3 $BH 3 ) or borazine (B 3 N 3 H 6 ) as the precursor.…”

Excellent electronic transport in heterostructures of graphene and monoisotopic boron-nitride grown at atmospheric pressure

“…While the HPHT method produces BN of the highest quality, it is clearly limited in its scalability. An alternative method of growth using atmospheric pressure and high temperature (APHT) [23][24][25][26] is not only more suitable for larger scales [26,27], but furthermore allows for the easy control of isotopic concentrations [28].…”

Boron nitride for excitonics, nano photonics, and quantum technologies

“…Using a more spatially focused beam than a laser one, that is to say by doing cathodoluminescence measurements, it is possible to excite regions of the crystal free from defects. Then the fluorescence is freed from contributions of such defects [17,110,132]. However, cathodoluminescence measurements failed to detect fluorescence for thicknesses smaller than six monolayers [133].…”

“…The reasons for this enhancement are correlated to the interactions of neutrons with 10 B atoms with a cross section of 3835 barns to be compared with 0.0055 barns for 11 B. There are two boron neutron capture fission reactions possible with different probabilities of occurrence: Decisive scientific breakthroughs appeared when large size (about 1 × 1 × 0.2 mm 3 ) single crystals were grown in 2004 in the group of T. Taniguchi at NIMS [16] and later in the groups of James Edgar at KSU [17], Nikholai Zighadlo at Basel University [18] and many other actors including several companies now selling it. Watanabe et al [16] demonstrated in particular in their 2004 article that hBN could emit a strong cathodoluminescence signal at 215 nm and that laser action could be observed at this short wavelength, a wavelength never reached before.…”

“…A lot of efforts have been dedicated to the epitaxial growth of hBN epilayers and they continue to be. Growth of bulk hBN crystals is realized after solidification of a melt of precursors ( [16][17][18]123] and refs therein) and their sizes are critically depending on the tricks under the technology used to cool down the melt in order to trigger and control as much as possible its solidification [124]. In epitaxial approaches of the growth, the boron nitride is (with hopefully good stoichiometry) deposited on a target substrate which can be a metal like gold [124], copper [125][126][127], or sapphire [128,129] or Highly Ordered Pyrolitic Graphite [40] or the Si face of SiC [130] to cite a few examples.…”