Formation and optical properties of ZnO:ZnFe₂O₄ superlattice microwires

Pure ZnO hexagonal microwires and Fe(III)-doped ZnO microwires (MWs) with a novel rectangular cross section were synthesized in a confined chamber by a convenient one-step thermal evaporation method. An oriented attachment mechanism is consistent with a vapor-solid growth process. Photoluminescence (PL) and Raman spectroscopy of the Fe(III)-doped ZnO MWs and in situ spectral mappings indicate a quasi-periodic distribution of Fe(III) along a one-dimensional (1-D) superlattice ZnO:ZnFe₂O₄ wire, while PL mapping shows the presence of optical multicavities and related multimodes. The PL spectra at room temperature show weak near-edge doublets (376 nm and 383 nm) and a broad band (450-650 nm) composed of strong discrete lines, due to a 1-D photonic crystal structure. Such a 1-D coupled optical cavity material may find many applications in future photonic and spintronic devices.[Figure not available: see fulltext.]