Characterization of ZnO in Infiltrated PS-b-PMMA

We have characterized the growth of ZnO using sequential infiltration synthesis (SiS) in PS-b-PMMA block copolymers (BCP) of spherical and cylindrical sub-20nm morphologies and studied how the photoluminescence of these nanostructures varies per its seed layer. We report blue-shifted photoemission at 335 nm (3.70 eV), suggesting quantum confinement effects. Infiltrated ZnO prepared with an alumina seed layer showed additional defect state photoemission at 470 nm and 520 nm for spherical and cylindrical BCP morphologies, respectively. Defect photoemission was not observed in samples prepared without a seed layer. No Raman peaks were observed for any samples with less than four cycles of ZnO, implying these ZnO nanostructures are isolated emitters. Samples annealed in air above 500 ^oC began to coalesce and show photoemission characteristic of bulk ZnO at 370 nm (3.35 eV). Our work demonstrates that ZnO nanostructures grown on PS-b-PMMA via SiS are advantageous in uniformity and size, and exhibit unique fluorescence properties. The nature of PS-b-PMMA as a photoresist allows infiltrated ZnO to be easily manipulated with lithography for on-chip compact light sources, photodetectors, photodiodes, and other various quantum materials and CMOS applications.