Oxygen Controls Surface of Epitaxial Manganite Films

This atomically resolved study revealed a strong link between oxygen pressure and both surface-structure formation and growth dynamics in manganite thin films. The work provides key insights into controlling atomic-level behavior necessary for growing functional materials, such as manganese oxides  for electronic and solid-oxide fuel cell applications.

Understanding the surface and structure formation in these systems is critical to improving efficiencies and controlling device structure, but has been hindered by lack of atomic-resolution studies, largely due to difficulties in preparing an atomically clean surface. Here, films of a common manganese oxide, La_5/8Ca_3/8MnO₃, were grown with atomic-level precision using laser molecular beam epitaxy and then imaged without exposure to air with scanning tunneling microscopy (STM). The STM imaging was combined with in-situ analysis of surface chemical composition by means of angle-resolved X-ray photoemission spectroscopy.

The researchers found a dramatic effect of the background oxygen pressure during deposition of the manganese oxide on both structural and chemical features of the film surface. These experiments are the first studies on formation of the surface structure and chemistry in epitaxy of manganite films to reveal atomic-scale details. They pave the way towards a greater understanding of the ways oxygen pressure controls formation of the structure and surface of thin films of these technologically important materials. 

 

A. Tselev, R. K. Vasudevan, A. G. Gianfrancesco, L. Qiao, P. Ganesh, T. L. Meyer, H. N. Lee, M. D. Biegalski, A. P. Baddorf, and S. V. Kalinin, “Surface control of epitaxial manganite films via oxygen pressure,” ACS Nano, 9, 4316 (2015).    DOI: 10.1021/acsnano.5b00743

 

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