Atomic and Electronic Structures of Co-Related Point Defects in CoSb3
Co-vacancies (VCo) and Co-interstitials (Coi) have been suggested to play key roles in p-type doping in CoSb3 under Sb-rich and Co-rich conditions, respectively. Based on density-functional theory calculations, we report detailed atomic and electronic structures of the Co-related point defects in CoSb3. The Co-vacancy is found to induce increases in the long and short bond lengths of the nearby Sb4 rings, generating Sb4-π-like acceptor states inside the band gap. Co-interstitial is found to have a sevenfold coordination number in the lowest energy configuration, and gives a single 3d-like acceptor state slightly above the valence-band maximum. The sevenfold Co-interstitials can be paired with an additional Coi–Coi bond, and by the pairing, the 3d-like acceptor state becomes deep inside the band gap, and new donor states are found to emerge inside the band gap.