Ab initio study of ferroelectric BiAlO3 (0 0 0 1) polar surfaces

Herein, we present first-principles density functional theory (DFT) calculations to study the stoichiometric (0 0 0 1) polar surfaces of ferroelectric BiAlO3. The results show that the physical and chemical properties are different between the positively and negatively polarized surfaces. The integrated AlO3Bi trilayer exhibited the minimal cleavage energy and considered as the more favorable construction. It is found that the surface compensation charges are 0.45e and −0.46e for the most stable positive and negative surfaces, respectively. The significant relaxations are found at the outermost Al and Bi atomic layers for the positive and negative surfaces, respectively. The electronic structure shows that the most favorable negative and positive surfaces are insulating and the energy gap of the positive surface is reduced by 0.8 eV with respect to the bulk. We predict that the atomic charges of preferred BiAlO3 (0 0 0 1) polar surfaces are strongly dependent on the ferroelectric polarization.