Вплив кисневих вакансій та міжвузлових атомів цинку і бору на електронну структуру та властивості ZnO: DFT дослідження

• Datum: 2025
• Hauptverfasser: Казакова, О. О., Варварін, М. О., Галстян, І. Є., Рудь, М. О., Лень, Є. Г.
• Format: Artikel
• Sprache: Ukrainisch
• Veröffentlicht: Chuiko Institute of Surface Chemistry National Academy of Sciences of Ukraine 2025
• Schlagworte: оксид цинку; киснева вакансія; міжвузлові атоми; електронна структура; DFT розрахунок
• Online Zugang: https://surfacezbir.com.ua/index.php/surface/article/view/803
• Назва журналу: Surface

Zinc oxide (ZnO) is a promising material for transparent current collector layers (TCOs) in optoelectronics due to its wide band gap and high transparency. However, its technologically important properties are determined not by the ideal crystal structure but by the presence of point defects, such as oxygen vacancies (V_O) and interstitial atoms, for example, of zinc and boron (Zn_i, B_i), the concentration of which is particularly high near surfaces and grain boundaries. The electronic properties of these defects are fundamentally dependent on their charge state and ability to form complexes. Although individual defects have been well studied, but there is a lack of systematic comparative analysis of how different charge states (V_O(0)) versus V_O(2+)) and complex formation (V_O + Zn_i versus V_O + B_i) influence on the band structure (including impurity levels), electronic density of states, and, consequently, on the effective band gap (Eg), which determines the transparency and conductivity of the material. A systematic study of the influence of V_O with different charge states (0, 2+) and their complexes with interstitial Zn_i, B_i atoms on the band structure and orbital-projected density of states was performed using ab initio calculations within the framework of density functional theory (DFT+U) for wurtzite ZnO. The electronic structure was calculated using the PBE functional considering the Hubbard U-correction (U = 7.5 eV) for the correct description of the 3d states of Zn in the Quantum ESPRESSO software package. Simulations were performed on 2×2×2 supercells (31–32 atoms) with complete relaxation of atomic positions for ideal ZnO and for systems contained the defects. The band structure was calculated along the high-symmetry directions, and the PDOS was calculated on a dense 8×8×6 k-point grid using the tetrahedron method. Ideal ZnO was found to be a direct-gap semiconductor with a characteristically low Eg ≈ 1.1 eV in (PBE+U) calculations, where the valence band maximum (VBM) is formed by O 2p states, and the conduction band minimum (CBM) — by Zn 4s states. As shown, the defects radically change this picture. A neutral vacancy acts as a shallow donor, creating a filled defect level localized on Zn atoms near the oxygen vacancy. A charged vacancy, V_O(2+), has the opposite effect: its defect level becomes empty and forms the bottom of the conduction band. The electronic structure and band gap of ZnO are not constants, but are dynamically controlled by the presence of defects, their charge states, and interactions. Depending on the defect state, the band gap can be effectively narrowed, broadened, or even formed by other states. These results have practical implications for the engineering of ZnO film properties, demonstrating how the control of the defect structures (especially near surfaces) allows for the manipulation of the transparency and conductivity of the material.