Materials with metastable phases can exhibit vastly different properties from their thermodynamically favored counterparts. Methods to synthesize metastable phases without the need for high-temperature or high-pressure conditions would facilitate their widespread use. I will discuss the electrochemical growth at room temperature in aqueous solution of microcrystals of bismuth selenide, Bi2Se3, in the metastable orthorhombic phase. Rather than direct epitaxy with the growth substrate, the spontaneous formation of a seed layer containing nanocrystals of cubic BiSe enforces the metastable phase. We first used single-crystal silicon substrates with a range of resistivities and different orientations to identify the conditions needed to produce the metastable phase. When the applied potential during electrochemical growth is positive of the reduction potential of Bi3+, an initial, Bi-rich seed layer forms. Electron microscopy imaging and diffraction reveal that the seed layer consists of nanocrystals of rock salt BiSe embedded within an amorphous matrix of Bi and Se. Using density-functional theory calculations, we show that epitaxial matching between cubic BiSe and orthorhombic Bi2Se3 stabilizes the metastable orthorhombic phase over the thermodynamically stable rhombohedral phase. The spontaneous formation of the seed layer enables us to grow orthorhombic Bi2Se3 on a variety of substrates including single-crystal silicon with different orientations, polycrystalline fluorine-doped tin oxide, and polycrystalline gold. The ability to stabilize metastable phases through room-temperature electrodeposition in aqueous solution without requiring a single-crystal substrate, broadens the range of applications for novel semiconductor compounds in optoelectronic and electrochemical devices.

Spontaneous seed formation during electrodeposition drives epitaxial growth of metastable semiconductor microcrystals

Where thousands of chemistry professionals meet to share ideas and advance scientific and technical knowledge. Spring 2023 abstracts, posters, and presentations will launch at the end of March.

ACS Spring 2023

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.