Editing Boron nitride (section)

==Structure==
Boron nitride exists in multiple forms that differ in the arrangement of the boron and nitrogen atoms, giving rise to varying bulk properties of the material.

=== Amorphous form (a-BN) ===
The amorphous form of boron nitride (a-BN) is non-crystalline, lacking any long-distance regularity in the arrangement of its atoms. It is analogous to [[amorphous carbon]].

All other forms of boron nitride are crystalline.

=== Hexagonal form (h-BN) ===
The most stable crystalline form is the hexagonal one, also called h-BN, α-BN, g-BN, graphitic boron nitride and "white graphene". Hexagonal boron nitride (point group = D<sub>3h</sub>; space group = P6<sub>3</sub>/mmc) has a layered structure similar to graphite. Within each layer, boron and nitrogen atoms are bound by strong [[covalent bond]]s, whereas the layers are held together by weak [[van der Waals force]]s. The interlayer "registry" of these sheets differs, however, from the pattern seen for graphite, because the atoms are eclipsed, with boron atoms lying over and above nitrogen atoms. This registry reflects the local polarity of the B–N bonds, as well as interlayer N-donor/B-acceptor characteristics. Likewise, many metastable forms consisting of differently stacked polytypes exist. Therefore, h-BN and graphite are very close neighbors, and the material can accommodate carbon as a substituent element to form BNCs. BC<sub>6</sub>N hybrids have been synthesized, where carbon substitutes for some B and N atoms.<ref>{{cite journal | author = Kawaguchi, M. | title = Electronic Structure and Intercalation Chemistry of Graphite-Like Layered Material with a Composition of BC6N | journal = Journal of Physics and Chemistry of Solids | volume = 69 | year = 2008 | page = 1171 | doi = 10.1016/j.jpcs.2007.10.076 |issue = 5–6 |bibcode = 2008JPCS...69.1171K |display-authors=etal}}</ref> Hexagonal boron nitride monolayer is analogous to [[graphene]], having a honeycomb lattice structure of nearly the same dimensions. Unlike graphene, which is black and an electrical conductor, h-BN monolayer is white and an insulator. It has been proposed for use as an atomic flat insulating substrate or a [[tunnel diode|tunneling]] dielectric barrier in 2D electronics. .<ref>{{cite journal
| vauthors = Ba K, Jiang W, Cheng J, Bao J, ''et al.''
| date = 2017
| title = Chemical and Bandgap Engineering in Monolayer Hexagonal Boron Nitride
| journal = Scientific Reports
| volume = 7
| issue = 1
| page = 45584
| doi = 10.1038/srep45584
| pmid = 28367992
| bibcode = 2017NatSR...745584B
| s2cid = 22951232
| doi-access = free
| pmc = 5377335
}}</ref>

Studies into the optical properties of [[hexagonal boron nitride|h-BN]] at the few- and mono-layer level have been conducted using specialized techniques like [[deep ultraviolet]] (DUV) [[hyperspectral imaging]] due to its very wide bandgap. Research at low temperatures revealed that [[monolayer]] h-BN exhibits [[photoluminescence]] consistent with a [[direct and indirect bandgaps|direct bandgap]] semiconductor, with emission observed around 6.1 eV. In contrast to observations in other 2D materials like [[transition metal dichalcogenide monolayers|TMDs]], the photoluminescence intensity remains remarkably high in few-layer h-BN, which has been attributed to a high radiative efficiency despite the [[direct and indirect bandgaps|indirect bandgap]] nature of bulk h-BN. Complementary [[atomic force microscopy|AFM]] investigations, particularly in tapping and Kelvin probe modes, have provided nanoscale insight into surface morphology and potential distribution across mono- and few-layer regions. These AFM-based techniques not only assist in confirming flake thickness and uniformity but also support optoelectronic analyses by correlating topographical and electrical variations with luminescence behavior.<ref name="Rousseau2021DUV">{{cite journal | last1=Rousseau | first1=Adrien | last2=Ren | first2=Lei | last3=Durand | first3=Alrik | last4=Valvin | first4=Pierre | last5=Gil | first5=Bernard | last6=Watanabe | first6=Kenji | last7=Taniguchi | first7=Takashi | last8=Urbaszek | first8=Bernhard | last9=Marie | first9=Xavier | last10=Robert | first10=Cédric | last11=Cassabois | first11=Guillaume | title=Monolayer Boron Nitride: Hyperspectral Imaging in the Deep Ultraviolet | journal=Nano Letters | volume=21 | issue=23 | pages=10133–10138 | date=September 16, 2021 | doi=10.1021/acs.nanolett.1c02531 | pmid=34529455 }}</ref>

=== Functionalization and Heterostructures ===
Modifications of hexagonal boron nitride have led to novel materials like hBNCF, a vertical heterostructure involving [[graphene]] and [[hexagonal boron nitride|h-BN]] functionalized with [[fluorine]]. This material, synthesized from h-BN via graphitization and fluorination, was found to exhibit room-temperature [[ferromagnetism]]. Crucially, [[Magnetic Force Microscopy]] (MFM), a specialized mode of [[Atomic Force Microscopy|AFM]], was employed to investigate the magnetic properties at the nanoscale. These MFM studies confirmed the ferromagnetic nature of the hBNCF powder. Furthermore, the MFM analysis provided evidence that the observed magnetism was intrinsic to the hBNCF structure, helping to exclude extrinsic [[magnetic impurity|metallic magnetic impurities]] as the origin.<ref name="Sahoo2021hBNCF">{{cite journal | last1=Sahoo | first1=Krishna Rani | last2=Sharma | first2=Rahul | last3=Bawari | first3=Sumit | last4=Vivek | first4=S. | last5=Rastogi | first5=Pankaj Kumar | last6=Nair | first6=Swapna S. | last7=Grage | first7=Stephan L. | last8=Narayanan | first8=Tharangattu N. | title=Room-temperature ferromagnetic wide bandgap semiconducting fluorinated Graphene-hBN vertical heterostructures | journal=Materials Today Physics | volume=21 | pages=100547 | year=2021 | doi=10.1016/j.mtphys.2021.100547 | issn=2542-5293}}</ref> The material was also characterized as a wide [[band gap]] semiconductor (~3.89 eV) with potential applications as an [[MRI contrast agent]].<ref name="Sahoo2021hBNCF"/>

=== Cubic form (c-BN) ===
Cubic boron nitride has a crystal structure analogous to that of [[diamond]]. Consistent with diamond being less stable than graphite, the cubic form is less stable than the hexagonal form, but the conversion rate between the two is negligible at room temperature, as it is for diamond. The cubic form has the [[Cubic crystal system#Zincblende structure|sphalerite crystal structure]] (space group = F{{overline|4}}3m), the same as that of diamond (with ordered B and N atoms), and is also called β-BN or c-BN.

=== Wurtzite form (w-BN) ===
The [[Wurtzite crystal structure|wurtzite]] form of boron nitride (w-BN; point group = C<sub>6v</sub>; space group = P6<sub>3</sub>mc) has the same structure as [[lonsdaleite]], a rare hexagonal polymorph of carbon. As in the cubic form, the boron and nitrogen atoms are grouped into [[tetrahedra]].<ref>{{cite book | author = Silberberg, M. S. | title = Chemistry: The Molecular Nature of Matter and Change | edition = 5th | location = New York | publisher = McGraw-Hill | year = 2009 | page = 483 |isbn=978-0-07-304859-8}}</ref> In the wurtzite form, the boron and nitrogen atoms are grouped into 6-membered rings. In the cubic form all rings are in the [[chair configuration]], whereas in w-BN the rings between 'layers' are in [[boat configuration]]. Earlier optimistic reports predicted that the wurtzite form was very strong, and was estimated by a simulation as potentially having a strength 18% stronger than that of diamond. Since only small amounts of the mineral exist in nature, this has not yet been experimentally verified.<ref>{{Cite web |url=https://www.newscientist.com/article/dn16610-diamond-no-longer-natures-hardest-material/ |title=Diamond no longer nature's hardest material |last=Griggs |first=Jessica |date=2014-05-13 |website=New Scientist |access-date=2018-01-12}}</ref> Its hardness is 46 GPa, slightly harder than commercial borides but softer than the cubic form of boron nitride.<ref name="ReferenceA" />

<gallery mode="packed">
File:Boron-nitride-(hexagonal)-side-3D-balls.png|Hexagonal form (h-BN)<br/>[[Hexagonal crystal family|hexagonal]] analogous to [[graphite]]
File:Boron-nitride-(sphalerite)-3D-balls.png|Cubic form (c-BN)<br/>[[sphalerite]] structure<br/> analogous to [[diamond]]
File:Boron-nitride-(wurtzite)-3D-balls.png|Wurtzite form (w-BN)<br/>[[Wurtzite crystal structure|wurtzite]] structure<br/>analogous to [[lonsdaleite]]
</gallery>