Ferroelectric properties of BaTiO₃ nanocube self-assembled monolayers: an investigation using piezoresponse force microscopy

We investigated the ferroelectric properties of barium titanate (BTO) nanocube self-assembled monolayers with and without heat treatment using piezoresponse force microscopy (PFM). Observations of polarization switching behavior confirmed that BTO nanocube monolayers about 15 nm thick are ferroelectric, even without heat treatment. Vertical PFM phase imaging of the monolayers revealed that heat treatment changed the ferroelectric polarization distribution in the monolayers at 800 °C. Atomic force microscopy and transmission electron microscopy suggested that this change originated from the residual stress caused by mechanical interactions between neighboring BTO nanocubes and between the monolayers and the substrate.