Interface Stability-Controlled Growth of FexGe on Ge (100), (110),and (111) Substrates

The electronic and magnetic properties of materials arestrongly influenced by their surface and interface structures andconfigurations. In this work, we have grown FexGe single crystalline islandson the Ge substrate with three different surfaces, (001) (110), and (111), andinvestigated the interface structures between FexGe crystals and Gesubstrates. The FexGe crystals result in two distinct phases on all three Gesubstrates, namely, monoclinic and hexagonal. Using TEM/HRTEM, 3Drotational electron diffraction, and DFT simulation approaches, we carefullystudied the facet orientation at the interface and explained the coexistenceand formation mechanism of the monoclinic-FeGe and hexagonal-Fe13Ge8.Although Ge substrates with different orientations were used in the study, ourfindings suggest a unique facet preference that all the FexGe crystals tend to grow with Ge {111} epitaxially or endotaxially.Combining simulation of energy difference on selected facets, lattice mismatch, and the dangling bond density, we derive themechanism of such a phenomenon as an interfacial equilibrium driven by the difference of interface energy. Our study providesvaluable information in the FexGe/Ge system and will potentially benefit the future development of FexGe-related electronic/magnetic devices.

Automated summary

This study investigates the interface structures and formation mechanisms between FexGe single crystalline islands and Ge substrates. The findings reveal that FexGe crystals exhibit two distinct phases on different Ge substrates and tend to grow epiaxially or endotaxially on Ge {111} surfaces. Simulation analysis sheds light on the mechanism of interfacial equilibrium driven by the difference of interface energy.