Hexagonal monolayer AlN (h-mAlN) is an indirect wide-gap semiconductor and is attractive for use in optoelectronic devices. Herein, first-principles calculations are performed to study the electronic, vibrational, elastic, and piezoelectric properties of H and F-functionalized AlN sheets. The results indicate that the H-/ F-functionalized (FAlNH) and fully H-functionalized (HAlNH) sheets are thermodynamically and dynamically stable. FAlNH is a direct bandgap material while HAlNH is still an indirect one. The F(H) atoms in F(H)AlNH bonded with Al act as electron acceptors whereas the H atoms bonded with N are electron donors. Some vibrational modes of these two functionalized systems differ significantly although their structures are similar. Functionalization with the H and F atoms reduces the elastic constants considerably and alters the mechanical performances of both systems. The in-plane piezoelectric constants of the FAlNH (HAlNH) sheet increase (decrease) surprisingly to about three times (one-third) that of h-mAlN. However, the work functions of both systems are enhanced notably. The study provides useful information for modulating the intrinsic properties of h-mAlN for possible applications.

No abstract

No abstract

No abstract