Quaternary p-type sulfide-fluoride transparent conductor: BaCuSF

Conductive thin films of wide band-gap BaCuSF were prepared by pulsed laser deposition and post-annealing in a H$_{2}$S. High conductivity (up to 500-1800 S/cm), carrier density ($\sim $10$^{21}$ cm$^{-3})$, and mobility (0.7-4 cm$^{2}$/Vs) were measured for the undoped and potassium-doped films, attributed to the textured crystalline structure at low processing temperature (T=235$^{\circ}$C). The positive Seebeck coefficient (+5 $\mu $V/K) identifies holes as majority mobile carriers in this degenerate semiconductor. The conductivity can be significantly reduced ($\sim $10$^{5}$ S/cm) by higher temperature annealing, with observed higher transparency in the visible and near-IR spectrum. The absorption coefficient of the high conductivity BaCuSF films is compared to that of transparent conducting oxides of the delafossite structure.