A study on the magnetic properties of carbon-doped (1 1 2-bar 0) ZnO thin films

By using the first principle method based on density functional theory (DFT), a study on the electronic structure and the ferromagnetic stability in C-doped (1 1 2-bar 0) ZnO thin films was conducted. It was found that the thin films have a FM ground state for a majority of configurations. It was also found that C atoms in the thin films have a clear clustering tendency. The ferromagnetism (FM) can be attributed to the coupling between C energy levels. The results showed that oxygen vacancies cannot stabilize the FM coupling of C-doped ZnO thin films. However, zinc vacancies can stabilize the FM coupling of the thin films, which indicates that hole-carriers play a crucial role in the observed FM behavior. In addition, the strain effect on the FM of C-doped ZnO thin films was also analyzed. - Research highlights: → In the paper, by using the first principle method based on density functional theory (DFT), a study on the electronic structure and the ferromagnetic stability in C-doped (1 1 2-bar 0) ZnO thin films was conducted. → The results showed that C atoms in the thin films have FM stability for a majority of configurations. It was found that C defects have a tendency to form clusters. The FM coupling between C atoms is long-ranged. → It was found that zinc vacancies can stabilize FM coupling of C-doped (1 1 2-bar 0) ZnO thin films. However, oxygen vacancies are unfavorable to FM coupling of the thin film. → Because of the complexity of the hybridization and anisotropy of spin density distribution in space, the FM and conductive properties of the thin films can be tuned by lattice strain.