Photoluminescence properties of Sm-doped ZnO grown by sputtering-assisted metalorganic chemical vapor deposition

Sm-doped ZnO (ZnO:Sm) thin films with c-axis oriented wurzite structure were grown by sputtering-assisted metalorganic chemical vapor deposition (SA-MOCVD). In the photoluminescence (PL) measurements of annealed ZnO:Sm, sharp emission lines from intra-4f transitions in Sm3+ ions were observed at room temperature under the excitation energy above the bandgap energy of ZnO (indirect excitation). In the dependence of PL intensity at 77 K on Sm concentration, the Sm3+ PL intensity was the largest at Sm concentration of 0.4%. In time-resolved PL measurements, the lifetime of Sm3+ PL became short at higher Sm concentration than 0.4%. These results revealed that a quenching of the Sm3+ PL from ZnO:Sm was induced at higher Sm concentration than 0.4%.