The direct response of electronic properties as a function of the density of a material can be examined and controlled by the application of external pressure. In this way, lattice compression allows for a “clean” systematic tuning of the charge density, i.e., without the necessity for changes to the chemical composition of the material via dopants. Exploratory high-pressure experiments can then inform the design of bulk synthesis of materials that benefit from their properties under compression or strain. Here, we report the electronic and structural response of semiconducting tin nitride Sn3N4 under compression -- a continuous opening of the optical band gap from 1.3 eV to 3.0 eV over a range of 100 GPa, corresponding to a 540 nm blueshift which spans the entire visible spectrum. The pressure-mediated band gap opening is found to be general to this material across a number of high-density polymorphs, implicating the predominant ionic bonding nature in the material as the root of its mechanism -- fingerprinted by an increase in charge localization in the material with reducing volume. The rate of decompression reveals recoverable metastable states with varying band gaps energies, opening the possibility of pressure tuneable electronic properties for future applications.

Pressure tuneable visible-range band gap in the ionic spinel tin nitride

256th National Meeting (2018)

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