Photoluminescence Properties of Er-doped Y_2O_3 Thin Films by Radical-enhanced Atomic Layer Deposition

摘要

Erbium-doped Y_2O_3 thin films were synthesized by combining radical-enhanced atomic layer deposition (RE-ALD) of Y_2O_3 and Er_2O_3 in an alternating fashion at 350℃. The Er doping level was precisely controlled to range from 6 to 14 at.% by varying the ratio of Y_2O_3:Er_2O_3 cycles during deposition. At 350℃, the films were found to be polycrystalline, showing a preferential growth direction in the [111] direction. Room-temperature photoluminescence (PL) at 1.54 μm, characteristic of the Er~(3+) intra 4f transition, was observed in a 500-A Er-doped (6 at.%) Y_2O_3 film, showing well resolved Stark features indicating the proper incorporation of Er in the Y_2O_3 host. Extended X-ray absorption fine structure (EXAFS) analysis revealed a six-fold coordination of Er by O in all samples, suggesting that the PL quenching observed at high Er concentration ( > 8 at.%) is likely dominated by Er ion-ion interaction and not by Er immiscibility in the Y_2O_3 host. The effective absorption cross section for Er~(3+) ions incorporated in Y_2O_3 was determined to be ～10~(-18) cm~2, about three orders of magnitude larger than the direct optical absorption cross section reported for Er~(3+) ions in a stoichiometric SiO_2 host.