Anomalous strain behavior on EuTe self-assembled islands

作者：Heredia E; Diaz B^*; Malachias A; Rappl P H O; Iikawa F; Brasil M J S P; Motisuke P

来源：Journal of Crystal Growth, 2014, 386: 139-145.

DOI：10.1016/j.jcrysgro.2013.10.002

• EuTe
• Magneto-optic materials
• Molecular beam epitaxy
• Nanostructures
• High resolution X-ray diffraction

EuTe is a magnetic semiconductor with potential applications in prototype optoelectronic and spintronic devices. In this work, we investigated the structural properties of EuTe grown on BaF2(111) substrates by molecular beam epitaxy. X-ray diffraction measurements were performed on two series of samples with different growth times and temperatures. The growth occurs in the Volmer-Webber mode, with initial formation of islands that then coalesce to form thin films. The islands size, mosaic spread, and strain state are deduced as a function of growth conditions. Surprisingly, the EuTe islands exhibit in-plane tensile strain, while compressive strain is expected for structures grown over a substrate with smaller lattice parameter. The islands tensile strain relaxes with increasing deposition times and substrate temperature, and it tends to zero for thick EuTe films. We propose that the EuTe/BaF2 lattice mismatch is compensated by the formation of interfacial misfit dislocations. The growth conditions out of equilibrium favor the formation of a metastable state with a high concentration of dislocations that over-compensates the original misfit. This is in agreement with the observed reduction of tensile strain as the substrate temperature increases.

• 出版日期2014-1-15
• 单位Saskatoon; Canadian Light Source