Strain-Controlled Formation Energy and Migration of Nitrogen Vacancy in Al_1-ScN: A First-Principles Study

The impact of strain on the formation energy and migration behavior of nitrogen vacancies (V_Ns) in Al_1-ScN has been investigated by first-principles calculations. The formation energy of V_Ns is obtained by total energy calculations. The migration barrier calculation utilizes the climbing nudged elastic band method. It is found that the formation energy of V_Ns is highly tunable with respect to the strain. The formation energy of V_Ns increases with the tensile strain increasing to +4% and decreases with the increasing compressive strain to -4%. A minimum formation energy of 4.11 eV is obtained when -4% strain is applied. Furthermore, the migration behavior of V_Ns is studied by calculating the migration barriers. Calculation results show that the migration barrier is strongly affected by strain. When the strain is -4%, the barrier is 2.46 eV while the barrier is increased to 2.71 eV under +4% strain. Therefore, a tensile strain can prevent the formation and migration of V_Ns. These findings suggest that strain engineering may serve as a tool for regulating V_Ns behavior in Al_1-ScN, potentially alleviating the ferroelectric degradations associated with V_Ns.