Electronic and thermodynamic properties of native point defects in V₂O₅: a first-principles study

Area of Science:

• Materials Science
• Solid State Physics
• Computational Chemistry

Background:

• Native point defects critically influence semiconductor properties.
• Vanadium pentoxide (V2O5) native defects, including vacancies, self-interstitials, and antisites, are crucial but underexplored, with only oxygen vacancies extensively studied.

Purpose of the Study:

• To systematically investigate the properties of all possible native defects in V2O5 using first-principles calculations.
• To understand the formation, electronic structure, and concentration of native defects in V2O5.
• To elucidate the role of these defects in V2O5's electronic properties and conductivity.

Main Methods:

• First-principles calculations utilizing the DFT+U method to determine electronic structure and formation energies.
• Statistical modeling with charge neutrality constraints to estimate defect concentrations.
• Kinetic Monte Carlo simulations to assess polaron mobility and hopping barriers.

Main Results:

• Vanadyl vacancies act as shallow acceptors but are compensated by more stable oxygen vacancies and interstitials, hindering intrinsic p-type doping.
• Oxygen vacancies are dominant under oxygen-deficient conditions, while oxygen interstitials become major defects under oxygen-rich conditions.
• Oxygen vacancies induce compensating electron polarons trapped at V centers with significant escaping barriers (0.6 eV), reducing polaron mobility by four orders of magnitude.

Conclusions:

• Oxygen vacancies are key to V2O5's electronic conductivity, acting as polaron traps.
• Despite reduced mobility, high concentrations of thermally activated polarons due to oxygen vacancies contribute to intrinsic n-type semiconducting behavior in V2O5 at elevated temperatures.