Morphology-engineered strain transformation in Ge/GeO2 core/shell nanoparticles

• Ge/GeO2 core/shell nanoparticles embedded in amorphous Al2O3 matrix is fabricated by the pulsed laser deposition method and rapid thermal annealing technique.
• The strain at the interface between the core and the shell strongly depends on the morphology of Ge/GeO2 core/shell nanoparticle.
• A dramatic transformation of the strain on Ge core from tensile to compressive strain during the shrinkage of Ge core and the expansion of GeO2 shell.

Growth of nanoparticles embedded in a host matrix can lead to substantial strain. Ge/GeO2 core/shell nanoparticles embedded in amorphous Al2O3 matrix is fabricated by the pulsed laser deposition method and rapid thermal annealing technique, which is confirmed by the experimental HRTEM result and consistent with Zhdanov׳s theoretical prediction. A finite-element calculation is performed to investigate the tuning effect on the strain by the morphology evolution of the Ge/GeO2 core/shell nanoparticle embedded in Al2O3 matrix. The simulated result indicates that the strain at the interface between the core and the shell strongly depends on the morphology of the nanoparticles. Moreover, it can be found that there is a dramatic transformation of the strain on Ge core from tensile to compressive strain during the shrinkage of Ge core and the expansion of GeO2 shell. The simulated results indicate that the strain can be designed by tuning the morphology of the nanoparticles, which provides an opportunity to engineer the properties of the nano-sized core/shell structures.