Polytypes of sp2-Bonded Boron Nitride

Abstract

The sp2-bonded layered compound boron nitride (BN) exists in more than a handful of different polytypes (i.e., different layer stacking sequences) with similar formation energies, which makes obtaining a pure monotype of single crystals extremely tricky. The co-existence of polytypes in a similar crystal leads to the formation of many interfaces and structural defects having a deleterious influence on the internal quantum efficiency of the light emission and on charge carrier mobility. However, despite this, lasing operation was reported at 215 nm, which has shifted interest in sp2- bonded BN from basic science laboratories to optoelectronic and electrical device applications. Here, we describe some of the known physical properties of a variety of BN polytypes and their performances for deep ultraviolet emission in the specific case of second harmonic generation of light.

First-Principles Calculations to Investigate the Structural, Electronic, Optical, and Elastic Constants; Thermal Conductivity; Raman Scattering; Mulliken Population; and XPS Loss Features of Boron Nitride Polytypes

“…The K L is around 3.905 W/(m K) at 300 K for h-B2N2, which is lower than the values for w-B2N2 (10.156 W/(m K)) and c-B4N4 (22.038 W/(m K)). However, compared to pristine sp 2 -hybridized fewlayer h-B2N2 sheets (227−280 W/(m K)), 153 BN nanotubes (350−2400 W/(m K)), 154,155 bulk hBN (390 W/(m K)), 156,157 five-layer h-BN (550 W/(m K)), 158 and sp 3 hybridized c-BN (2113 W/(m K)), 159 our results are significantly lower. To our knowledge, among the investigated BN polytypes, h-B2N2 had the lowest thermal conductivity of the lattice, as shown in Figure 7.…”

“…In recent years, extensive theoretical and experimental research has been conducted on the characteristics of the boron nitride (BN) polytype. The fascinating chemical and physical properties of BN, such as extreme durability, high chemical and thermal stability, low electron affinity, high melting point, low voltage constant, broad band bandwidth, excellent mechanical resistance, high melting field, double-type doping, etc., are widely used in modern microelectronic devices, solar cells, batteries, and their protection coatings. − BN materials are used primarily in high-temperature applications and are becoming a strong competitor for diamonds and SiC. , BN is a lightweight III–V compound and was first reported by Balmain et al BN is isoelectric when combined with III–V semiconductors such as GaAs, but it has very different properties. Unlike diamonds, GaN, and SiC, it is also called the third-generation semiconductor material after Si, Ge, and GaAs.…”

“…The use of h-B2N2 sheets as dielectric materials for transistors and nanocapacitors, as well as spacer layers for metal−insulator−metal devices is being investigated. 26−28 c-B4N4 is the second hardest material after diamond, which is resistant to oxidation and has a strong covalent sp 3 hybridization. It was first synthesized from c-B4N4 by Wentorf et al 29 using high temperatures and pressure.…”

“…It has excellent thermal conductivity and is considered a natural protective coating and a UV emitter. 30,31 The metastable phase stacking sequence w-B2N2 occurs in the formation of a covalent bond between B and N atoms with sp 3 and sp 2 hybridization. It is created from h-B2N2 by applying high pressure at ambient temperature.…”

Rhombohedral and Turbostratic Boron Nitride Polytypes Investigated by X-ray Absorption Spectroscopy

“…Recently, the interest in boron nitrides has grown significantly due to the potential application in novel devices, e.g., in microelectronics for various optical devices in the UV range, − detectors, and graphene-based devices. , The reason is due to the desirable properties of wide band gap semiconductors with high thermal stability and mechanical strength . Moreover, for 2D layered BN with sp 2 -hybridized in-planar bonding, there exist several different polytypes of crystalline structures: the hexagonal (h-BN), the rhombohedral (r-BN) and its twinned version (twin-r-BN), and a less ordered turbostratic phase (t-BN) .…”