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Understanding surface structure and chemistry of single crystal lanthanum aluminate

DOI: 10.1038/srep43721 DOI Help

Authors: Stevin S. Pramana (Imperial College London) , Andrea Cavallaro (Imperial College London) , Jiahui Qi (Imperial College London) , Chris L. Nicklin (Diamond Light Source) , Mary P. Ryan (Imperial College London) , Stephen J. Skinner (Imperial College London)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Scientific Reports , VOL 7

State: Published (Approved)
Published: March 2017
Diamond Proposal Number(s): 11597

Open Access Open Access

Abstract: The surface crystallography and chemistry of a LaAlO3 single crystal, a material mainly used as a substrate to deposit technologically important thin films (e.g. for superconducting and magnetic devices), was analysed using surface X-ray diffraction and low energy ion scattering spectroscopy. The surface was determined to be terminated by Al-O species, and was significantly different from the idealised bulk structure. Termination reversal was not observed at higher temperature (600 °C) and chamber pressure of 10−10 Torr, but rather an increased Al-O occupancy occurred, which was accompanied by a larger outwards relaxation of Al from the bulk positions. Changing the oxygen pressure to 10−6 Torr enriched the Al site occupancy fraction at the outermost surface from 0.245(10) to 0.325(9). In contrast the LaO, which is located at the next sub-surface atomic layer, showed no chemical enrichment and the structural relaxation was lower than for the top AlO2 layer. Knowledge of the surface structure will aid the understanding of how and which type of interface will be formed when LaAlO3 is used as a substrate as a function of temperature and pressure, and so lead to improved design of device structures.

Journal Keywords: Characterization and analytical techniques; Chemical physics

Subject Areas: Materials, Physics

Instruments: I07-Surface & interface diffraction