Unravelling oxygen-vacancy-induced electron transfer at SrTiO₃-based heterointerfaces by transport measurement during...

Numerous studies have shown that oxygen vacancies play an important role on the formation of two-dimensional electron gas (2DEG) at SrTiO₃-based heterointerfaces. Previously, it is widely believed that the main mechanism is that the oxygen vacancies in SrTiO₃ directly contribute electrons to the 2DEG. Here, we performed transport measurements during the creation of 2DEG for depositing amorphous LaAlO₃ on SrTiO₃ substrates and related heterostructures. Our result suggests that, unlike the previous viewpoint, in this kind of 2DEG the determinant mechanism is the electron transfer from the oxygen vacancies in the film grown on SrTiO₃, rather than the oxygen vacancies in SrTiO₃ themselves. This effect is so striking that an amorphous film of less than 10% monolayer coverage on SrTiO₃, or equivalently 0.04 nm, can already generate a highly conducting 2DEG. The present result may have a general implication and provide a possible way to understand the long-standing debate on the origin of 2DEG at SrTiO₃-based heterointerfaces.