Category: IRG 2 (DMR – 1720415)

Oxide compounds with multiple metal atoms are called complex oxides because they can have many chemical states, crystal structures, and a wide range of useful properties. Wisconsin MRSEC researchers have developed a new way to create crystals of an important series of oxides for quantum electronics, involving the lanthanide row of elements on the periodic table. The MRSEC team deposited lanthanide oxide films using a method called atomic layer deposition, using chemical precursors they developed. The resulting films are amorphous, with a disordered atomic structure, but heating them in contact with the surface of a substrate widely employed in oxide research transforms them into crystals templated by the substrate. This work required interdisciplinary collaboration among chemists, chemical engineers, and materials scientists, brought together by the MRSEC.

Small (nanometer-sized) crystals of multi-component, complex metal oxides have useful properties for applications in electronics, optics, sensors, and mechanical actuators. In order to realize this potential, engineers need to be able to put tiny crystals exactly where they are needed and to control the orientation of the crystal’s lattice. Researchers at the Wisconsin MRSEC and Argonne National Lab have studied a new way to place tiny oxide crystals through controlled, seeded crystallization of disordered, amorphous thin films. They have demonstrated controlled crystal growth at desired locations either from seeds of the same material (homoepitaxy) or seeds of a different material (heteroepitaxy). This work is an important step toward general control of oxide crystals and new applications.

Creating thin films using novel synthesis techniques is a key step in expanding the functionality of metal oxide materials. It is particularly important to create these oxides in new geometrical forms and with new compositions. Researchers and the Wisconsin MRSEC have developed ways to create new oxides by first synthesizing them in the amorphous form and subsequently crystallizing the deposited material, a process known as solid-phase epitaxy (SPE).

Three-dimensional metal oxide crystals with Madison MRSEC complex structures or compositions are challenging to prepare because it is difficult to control nanoscale phenomena underlying crystal nucleation and growth. Researchers at the Wisconsin MRSEC have now made important steps in establishing this control in so-called “perovskite” complex oxide crystals, a class of materials with useful optical and electronic properties.