Equilibrium carrier type and intrinsic conductivity of alpha-MnO2

Determine the equilibrium carrier type of stoichiometric alpha-MnO2 and establish whether intrinsic n-type or p-type conductivity is feasible by performing a full charge-neutrality analysis of its native defects.

Background

The paper calculates native-defect formation energies and charge-transition levels under Mn-rich and O-rich conditions, identifying manganese interstitials and oxygen vacancies as dominant compensating defects. These calculations indicate strong self-compensation near both band edges, but formation-energy diagrams alone do not determine the self-consistent equilibrium concentrations of charged defects and carriers.

A complete charge-neutrality analysis is therefore required to determine the equilibrium Fermi level, carrier type, and whether intrinsic n-type or p-type conductivity can occur in alpha-MnO2. The authors explicitly state that their present calculations leave this issue unresolved.