The impacts of cation stoichiometry and substrate surface quality on nucleation, structure, defect formation, and intermixing in complex oxide heteroepitaxy LaCrO3 on SrTiO3(001)

Journal Article · Tue Jan 01 00:00:00 EST 2013 · Advanced Functional Materials

DOI:https://doi.org/10.1002/adfm.201202655· OSTI ID:1090481

Qiao, Liang ^[1]; Zhang, K. H. L ^[2]; Bowden, Mark E ^[2]; Varga, Tamas ^[2]; Shutthanandan, Vaithiyalingam ^[2]; Colby, Robert ^[2]; Du, Yingge ^[2]; Kabius, Bernd ^[2]; Sushko, Peter V ^[3]; Biegalski, Michael D ^[1]; Chambers, S. A. ^[2]

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1. ORNL
2. Pacific Northwest National Laboratory (PNNL)
3. University College, London

Our ability to design and fabricate electronic devices with reproducible properties using complex oxides is critically dependent on our ability to controllably synthesize these materials in thin-film form. Structure-property relationships are intimately tied to film and interface composition Here we report on the effect of cation stoichiometry on structural quality and defect formation in LaCrO3 heteroepitaxial films prepared using molecular beam epitaxy. We calculate from first principles the regions of stability of various candidate defects as a function of Cr and O chemical potential, along with the predicted effects of these defects on structural parameters. We show that epitaxial LaCrO3 films readily nucleate and remain coherently strained on SrTiO3(001) over a wide range of La-to-Cr atom ratios, but that La-rich films are of considerably lower structural quality than stoichiometric and Cr-rich films. Cation imbalances are accompanied by anti-site defect formation, as deduced by comparing experimental trends in the c lattice parameter with those from first-principles calculations. Cation mixing occurs at the interface for all La-to-Cr ratios investigated, and is not quenched by deposition on SrTiO3(001) at ambient temperature. Indiffused La atoms occupy Sr sites, most likely facilitated by Sr vacancy formation in STO resulting from high-temperature oxygen annealing required to prepare the substrate. Intermixing is effectively quenched by using molecular beam epitaxy to deposit LaCrO3 at ambient temperature on defect free Si(001). However, analogous pulsed laser deposition on Si is accompanied by cation mixing.

• Research Organization: Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Center for Nanophase Materials Sciences (CNMS)
• Sponsoring Organization: USDOE Office of Science (SC)
• DOE Contract Number: DE-AC05-00OR22725
• OSTI ID: 1090481
• Journal Information: Advanced Functional Materials, Vol. 23, Issue 23; ISSN 1616-301X
• Country of Publication: United States
• Language: English

Related Subjects

Oxide heteroepitaxy
Nonstoichiometry
Intermixing
Molecular beam epitaxy