Short-Range Order Tunes Optical Properties in Long-Range Disordered ZnSnN2-ZnO Alloy

Local site ordering offers a new paradigm forproperty control in functional materials. However, systems thatexhibit a propensity for local order and global disorder are oftenchallenging to characterize, and demonstrations of ordering-induced property tuning are few and far between. Here, wedemonstrate that short-range ordering tunes the optical absorptionedge in the long-range disordered alloy system(ZnSnN2)1-x(ZnO)2xatx=0.25.Weusecombinatorialcosputtering to synthesize a set of thin-film samples spanningthis alloy space. X-ray diffraction demonstrates lattice contractionas a function of alloy composition, confirming that a mixed-anionand -cation alloy has been synthesized. Using N and O K-edge X-ray absorption near-edge structure in conjunction with simulationsof cation-disordered supercell structures, wefind that samples exhibit octet-rule-breaking motifs around both anions. Upon annealingat an alloy composition ofx= 0.25, X-ray absorption analysis suggests that local motif structure shifts toward octet-rule-conservingwhile long-range disorder is maintained. Spectroscopic ellipsometry reveals that local ordering increases the absorption edge energyat constant composition. Additionally, alloy-induced optical absorption edge tuning is demonstrated. This work paves the waytoward property tuning with short-range ordering in (ZnSnN2)1-x(ZnO)2xand beyond.

Automated summary

This study demonstrates that short-range ordering can tune the optical absorption edge in the long-range disordered alloy system (ZnSnN2)1-x(ZnO)2x at x=0.25. Using combinatorial cosputtering, a set of thin-film samples spanning this alloy space is synthesized. X-ray diffraction confirms the synthesis of a mixed-anion and -cation alloy. X-ray absorption analysis and spectroscopic ellipsometry reveal that local ordering increases the absorption edge energy at constant composition. This work opens up possibilities for property tuning with short-range ordering in (ZnSnN2)1-x(ZnO)2x and similar materials.