Atomic-Scale Imaging of Nanoengineered Oxygen Vacancy Profiles in SrTiO3

Oyxgen vacancies can act as n-type dopants in SrTiO3, allowing carrier mobilities in excess of 104 cm2/(Vs) at low temperatures. These dopants must be controlled and confined on nanometer lengths in order to produce functional oxide heterostructures. Using annular-dark-field electron microscopy and core-level spectroscopy, with absolute detection sensitivities of 1-4 oxygen vacancies, we are able to profile vacancy distributions on an atomic scale, opening a pathway to the microscopic study of dopant clustering and deactivation in oxides. 

Under the appropriate growth conditions, we successfully fabricated superlattices with oxygen doping profiles exhibiting sub-nanometer abruptness, limited only by mesoscopic fluctuations from vacancy clustering.