Shear strain induced indirect to direct transition in band gap in AlN monolayer nanosheet

• Homogeneous biaxial strain is most effective in tuning the band gap.
• Large shear strain uniaxial strain induces an indirect-to-direct transition.
• The dynamical stability have been assessed through phonon dispersion calculations.

The electronic band structure of aluminum nitride (AlN) nanosheets under different kinds of strains has been investigated. Our first principles based studies show that the homogeneous biaxial strain is most effective as compared to uniaxial and shear strain in tuning the band gap. Large shear strain (⩾7.5%) and 10% uniaxial strain along the zig–zag direction induces an indirect-to-direct transition in band gap. The response of these 2 dimensional AlN nanosheets to strain is different from that of its 3 dimensional bulk phase counterparts to pressure. Quantum confinement effects govern the behavior of the former. The dynamical stability of AlN nanosheets have also been assessed under different modes of strains through phonon dispersion calculations. The AlN nanosheets are found to be dynamically stable under tensile strain and shear strain along zig–zag directions, while the sheets are found to be unstable under compressive strain.