Materials Design and Functionality in Oxide Heterostructures
Favorable conditions for improved and miniaturized electronics require tunable functions in clean systems at the nanoscale. However, the methods required to fabricate the desired devices are not yet capable of meeting the necessary size, reproducibility, and tenability for useful functional compounds. On the other hand, heterostructures offer an appealing route to create a variety of states emerging from interfacial couplings and reduced-dimensionality effects. Indeed, sharp, clean interfaces, was one of the enabling factors leading to the revolution in modern semiconductor technologies and to the discovery of some of the most exotic forms of electronic matter, including the Quantum Hall Effect and the Fractional Quantum Hall Effect. Recently, in the family of transition metal oxides the diversity of phenomena discovered, from exotic superconducting phases to unconventional magnetic and ferroelectric behaviors, in digitally synthesized heterostructures is particularly spectacular. Here the emergent technology based on strong spin, charge, orbital and lattice interactions at nanometer thick interfaces promises to overcome the impasse faced today on scaling and compatibility issues by using materials abundant in synthetic chemistry.
I will discuss our effort to understand and employ properties of quantum mechanics to develop systems with functionalities arising from a collective interaction of electrons in a heterostructure. Our laboratory has served as a coordinated “scientific instrument” to study and exploit materials discoveries. Further to in-house deposition methods for materials growth, we develop and employ inhouse techniques including miniature magnetometers, thermal and electrical measurement apparatuses to the millikelvin regime and high fields, which complement our experiments using x-ray, neutron and muon techniques at international facilities. More recently we designed and built a “quiet island” inside the Nanyang Technological University. This prototype noise-free structure, which includes a materials and device fabrication platform, scanning probes and electronic transport measurements in a single ultra-high-vacuum environment aims at the design and growth of materials, and devices to perform fundamental studies and develop reliable methods for information technology.
The talk will also demonstrate typical examples of systems where by varying the composition of the individual layers of a heterostructure, the substrate material and selective external perturbations we may now control the interfacial properties over a broad range. The high degree of tunability achieved promises structures and devices with electromagnetic properties controllable at the atomic monolayer level.