Efficient Second Harmonic Generation in Specific Polytypes of Hexagonal Boron Nitride

Polytypism ( a very well-known phenomenon in Silicon Carbide) is currently under quite intense investigations in the field of 2D-semiconductors in general, and for boron nitride (BN) in particular. Although the most probable stacking routinely obtained is the perfect superposition of layers of 6-ring alternating B and n atoms where B and N atoms regularly alternate from one layer to another one in the <001> crystallographic direction, alteration of this perfection are also found (B.Gil et al. Crystals 12, 782 2022). This can be obtained by adding foreign atoms to the precursors routinely used to grow the layered BN (Tadao Sato, Proc. Jap. Academy, 10, 459, 1985), by heteroepitaxy on foreign surfaces, growth from precipitation out of the flux where Group IIB-metals are mixed with Carbon (Rousseau et al. Physical Review Materials 5, 064602 (2021), etc...

The modification thus produced of the crystalline ordering leads to an alternative periodicity which can allow novel physical properties such as piezoelectricity, spontaneous polarization, ferroelectricity, Second Harmonic Generation (SHG).

I will review more particularly how are produced the Graphitic AB stacking, the AA stacking and AND (Rombohedral) stackings by different growth methods, the impact of the polytypism on linear and nonlinear optical properties of layered hexagonal BN and I will put the emphasis on the measured efficient SHG in the DUV (200nm ) range.