Adiabatic small polaron hopping in a-MoO3 induced by oxygen vacancies

Oxygen vacancy induced polaron formation in defective MoO3-x has been suggested theoretically to maintain its structural stability. Here, we show the formation of extremely localized small polarons related to the ionic intermixing due to the vacancy formation in amorphous MoO3-x. High concentration of the oxygen vacancies (similar to 4%) results in two distinct adiabatic small polaronic hopping mechanisms in different temperature range. Activation energy values confirm the polaron hopping along distinct oxygen vacancy paths related to the vacancy formation energies. Highly localized small polarons, with radius smaller than the interatomic distances, are the result of a short-range order in the defective matrix of MoO3. Polaronic conduction in this system can be tuned via the density of the oxygen vacancies, which leads to the enhanced charge stability that can be exploited in advanced electronic and optical devices.