Dopant-Induced Manipulation of the Growth and Structural Metastability of Colloidal Indium Oxide Nanocrystals

Doping semiconductor nanocrystals is crucial for enhancing and manipulating their functional properties, but the doping mechanism and the effects of dopants on the nanocrystal growth and structure are not well understood. We show that dopant adsorption to the surfaces of colloidal In2O3 nanocrystals during incorporation inhibits the nanocrystal growth. This phenomenon induces a surface stress which gives rise to a reduction in atomic volume and leads to the formation of metastable corundum-type In2O3 for nanocrystals smaller than 5 nm. The growth beyond the critical size lowers the potential energy barrier height and causes the nanocrystal phase transformation. Direct comparison between Cr3+ and Mn3+ dopants indicates that the nanocrystal structure directly determines the dopant incorporation limits and the dopant electronic structure, which can be predicted and controlled. These results enable a new approach to designing multifunctional nanostructures and understanding the early stages of crystal growth in the presence of impurities.