Tuning phase stability of complex oxide nanocrystals via conjugation.

Nanocrystals (NCs) attract tremendous research interests because of their unique properties to meet the demands of functionalities. To date, hybrid NCs with multiple components are developed to meet the rising demands that could be very difficult, or even impossible to be achieved by single-component NCs. Tuning properties by strain via conjugation could be an alternative solution. Strain engineering has been discovered and widely applied to many thin-film materials for tuning physical properties. Then, there is a further question to be addressed in this study: can we take the advantages we have learned in heteroepitaxy of thin films and transfer that into the NC conjugation? In order to demonstrate this possibility, we investigated NC conjugation of BiFeO3 and LaAlO3. We found that change in either LaAlO3-NC or BiFeO3-NC size would change the stability of rhombohedral-to-tetragonal phase transition. The present results show that strain engineering is possible to be realized in not only thin film but also NC conjugation. The same concept should be applicable to other complex oxide systems in order to broaden their practical applications for the rising demands of multifunctionalities.