Exploring 2D materials by high pressure synthesis: hBN, Mg-hBN, b-P, b-AsP, and GeAs

In materials science, selecting the right synthesis technique for specific compounds is one of the most important steps. High-pressure conditions have a significant effect on the crystal growth processes, leading to the creation of unique structures and properties that usually are not possible under normal conditions. The prime objective of this article is to illustrate the benefits of using high-pressure, high-temperature (HPHT) technique when developing two-dimensional (2D) materials. We could successfully grow bulk single crystals of hexagonal boron nitride (hBN) and magnesium doped hexagonal boron nitride (Mg-hBN) from Mg-B-N solvent. Further exploration of the Mg-B-N system could lead to the crystallization of isotopically ¹⁰B and ¹¹B enriched hBN crystals, and other doped variants of it. Black phosphorus (b-P) and black phosphorus doped with arsenic (b-AsP) were obtained by directly converting its elements into melt and subsequently crystallizing them under HPHT. Germanium arsenide (GeAs) bulk single crystals were also obtained from the melt at a pressure of 1 GPa. Upon crystallization, all these compounds exhibit the anticipated layered structures, which makes them easy to exfoliate into 2D flakes, thus providing opportunities to modify their electrical behavior and create new useful devices.