From the synthesis of hBN crystals to their use as nanosheets for optoelectronic devices

TL;DR

This paper presents a novel method for synthesizing high-quality hexagonal boron nitride crystals and explores their application as nanosheets in optoelectronic devices, demonstrating promising optical properties and potential for future use.

Contribution

Introduces a dual synthesis method for large hBN crystals and investigates their use as nanosheets in heterostructures for optoelectronic applications.

Findings

High-quality hBN crystals with a free exciton lifetime of 0.43 ns.

BN nanosheets effectively encapsulate TMDs without luminescence interference.

BNNSs exhibit narrow photoluminescence linewidths suitable for optoelectronic devices.

Abstract

In the wide world of 2D materials, hexagonal boron nitride (hBN) holds a special place due to its excellent characteristics. In addition to its thermal, chemical and mechanical stability, hBN demonstrates high thermal conductivity, low compressibility, and wide band gap around 6 eV, making it promising candidate for many groundbreaking applications and more specifically for optoelectronic devices. Millimeters scale hexagonal boron nitride crystals are obtained through a disruptive dual method (PDC/PCS) consisting in a complementary coupling of the Polymer Derived Ceramics route and a Pressure-Controlled Sintering process. In addition to their excellent chemical and crystalline quality, these crystals exhibit a free exciton lifetime of 0.43 ns, as determined by time-resolved cathodoluminescence measurements, confirming their interesting optical properties. To go further in applicative fields, hBN crystals are then exfoliated, and resulting Boron Nitride NanoSheets (BNNSs) are used to encapsulate transition metal dichalcogenides (TMDs). Such van der Waals heterostructures are tested by optical spectroscopy. BNNSs do not luminesce in the emission spectral range of TMDs and the photoluminescence width of the exciton at 4K is in the range 2-3 meV. All these results demonstrate that these BNNSs are relevant for future opto-electronic applications.