Large out-of-plane piezoelectricity of single-layer group III–V compounds decorated with hydrogen and fluorine

Using first-principles calculations, we systematically investigated the effects of hydrogenation and fluorination on the piezoelectric properties of single-layer honeycomb structures composed of group III–V compounds. Our findings reveal that both hydrogenation and fluorination effectively enhance piezoelectricity in these materials. For the initially flat structures lacking out-of-plane piezoelectricity, hydrogenation and fluorination induce structural distortions and out-of-plane polarizations, thereby generating out-of-plane piezoelectricity. After hydrogenation and fluorination, most group III–V compounds exhibit significantly improved vertical piezoelectricity, making them promising candidates for ultrathin piezoelectric devices operating in the d31 mode. Notably, materials such as h-HInNH (0.59 pm/V), h-FInNH (1.13 pm/V), h-FInPH (0.88 pm/V), and h-FInAsH (0.83 pm/V) exhibit out-of-plane piezoelectric strain coefficients (d31) surpassing that of wurtzite boron nitride (0.33 pm/V). Additionally, the in-plane piezoelectric strain coefficients (d11) of most group III–V compounds show a notable increase following hydrogenation and fluorination. These results suggest that hydrogenation and fluorination of the single-layer group III–V compounds could lead to the development of promising 2D materials for advanced piezoelectric device applications.