Modulating Ferroelectric Response in Colloidal Semiconductor Nanocrystals through Cation Exchange

We report the appearance of ferroelectric behavior in CdSSe nanocrystals arising from a room-temperature cation exchange of semiconductor nanoparticles. Cation exchange reactions were performed on colloidal CdSSe nanocrystals using antimony, tin, and gold salts. The degree of exchange was determined using scanning transmission electron microscopy energy-dispersive spectroscopy and the ferroelectric response was measured using a Sawyer-Tower circuit. As the percent exchange of tin(IV) was varied, the ferroelectric properties were optimized at similar to 30 and 70% as a result of intracrystal atomic displacements. The amount of disorder can be minimized by selecting the exchange cation that exhibits the largest change in saturation polarization with the least amount of exchange. The ability to tune the structure and ferroelectric response of nanostructures could offer new routes toward the development of ferroelectric random-access memory devices as well as lower the cost of energy-harvesting applications.