Exploration of Electronic Functionalities in Metal Oxides by Combinatorial Lattice Engineering

A review is given for our originally-developed thin film technology, combinatorial lattice engineering. This is extended from a conventional pulsed laser deposition, where the surface of a sintered oxide tablet (target) is irradiated with focused laser pulses and the evaporated precursors are condensed on a heated substrate to grow single crystalline thin films. By this method, it has become possible to concurrently synthesize many oxide thin films on a substrate at different locations (segments) with such diversities as composition, growth conditions, and the sequence of heterostructures. By inserting a masking system between the target and substrate and computer controlling the mask motion as well as target switching, one can integrate many oxide thin film segments on the substrate. Starting from the background of and demand for this technology as well as the advancement of the key ingredient technology, i.e., atomically regulated epitaxial growth of oxide thin films, the concept and examples of this combinatorial lattice engineering are introduced highlighting the representative demonstration on magnetic, photonic, and electronic functionalities, especially emphasizing the benefit of this combinatorial technology. In addition, further progress of device physics triggered by the combinatorial discoveries are introduced, for example, electric field control of magnetism, bright ultraviolet light emitting devices, and quantum effects in oxide semiconductors.