Sulfide and Oxide-Sulfide Combinatorial Libraries by Co-Sputtering with an Atomic Sulfur Source

We report a deposition method with improved control over the sulfur content in thin-films through the addition of a radio frequency (RF) solids atom source (cracker) to a multiple-source sputtering system. Co-sputtering from one or two targets provides a compositional gradient across a 2'' substrate. In addition, a temperature gradient orthogonal to the composition gradient is induced. An RF solids cracker is used to provide controllable amounts of activated sulfur during the deposition. The composition gradient, temperature gradient and activated sulfur can be used concurrently to control the composition and phase of the thin films. In proof-of-principle experiments, Cu$_{\mathrm{2}}$S films have been grown from both Cu and Cu$_{\mathrm{2}}$O targets as well as Bi$_{\mathrm{x}}$O$_{\mathrm{y}}$S$_{\mathrm{z}}$ films with tunable oxygen to sulfur ratios from a Bi$_{\mathrm{2}}$O$_{\mathrm{3}}$ target. Further, the independent tuning of anion and cation ratios is demonstrated by the growth of BiCuOS. The successful growth of both sulfide and oxide-sulfide compounds demonstrates the viability of this hybrid approach. Finally, this hybrid deposition approach is likely extendable to phosphides and oxide-phosphides.