Chemical synthesis of two-dimensional iron chalcogenide nanosheets: FeSe, FeTe, Fe(Se,Te), and FeTe₂

Transition metal chalcogenides are important materials because of their range of useful properties and applications, including as thermoelectrics, magnetic semiconductors, superconductors, quantum dots, sensors, and photovoltaics. In particular, iron chalcogenides have received renewed attention following the discovery of superconductivity in PbO-type β-FeSe and related solid solutions. This paper reports a low-temperature solution chemistry route to the synthesis of β-FeSe, β-FeTe, FeTe₂, and several members of the β-Fe(Se,Te) solid solution. The samples were analyzed by powder XRD, TEM, EDS, SAED, SEM with elemental mapping, AFM, and SQUID magnetometry. Consistent with the layered crystal structures, the FeSe, FeTe, and Fe(Se,Te) products are predominantly twodimensional single-crystal nanosheets with thicknesses of approximately 2-3 nm and edge lengths ranging from 200 nm to several micrometers. FeTe₂ forms a mixture of nanosheets and onedimensional sheet-derived nanostructures. None of the samples are superconducting, which could be due to size effects, nonstoichiometry, or low-level impurities.