Anisotropic growth of ferberite (FeWO₄) on W (110) by high-temperature oxygen-assisted molecular beam epitaxy

We report on the growth of nanowires of ferberite (FeWO₄) by high-temperature oxygen-assisted molecular beam epitaxy on W (110). This multifunctional material has promising applications in different fields. The wires extend for several millimeters in length, with widths in the hundreds and heights in the tens of nanometers. We have monitored the growth process by real-time low-energy electron microscopy and characterized the wires in-situ by low-energy electron microscopy and laterally-resolved X-ray absorption and photoelectron spectroscopies. Further analysis was performed ex-situ by atomic force and optical microscopies as well as by Raman spectroscopy. The growth of ferberite on W (110) was possible by dosing iron in a molecular oxygen atmosphere likely due to the formation of highly mobile WOₓ units that can be incorporated into the anisotropic wolframite structure, which in turn is responsible for the highly anisotropic growth. We propose that the same method may be used for the growth of other tungstate or related compounds.