title: Solution-processed, barrier-confined, and 1D nanostructure supported quasi-quantum well with large photoluminescence enhancement.
abstract: Planar substrate supported semiconductor quantum well (QW) structures are not amenable to manipulation in miniature devices, while free-standing QW nanostructures, e.g., ultrathin nanosheets and nanoribbons, suffer from mechanical and environmental instability. Therefore, it is tempting to fashion high-quality QW structures on anisotropic and mechanically robust supporting nanostructures such as nanowires and nanoplates. Herein, we report a solution quasi-heteroepitaxial route for growing a barrier-confined quasi-QW structure (ZnSe/CdSe/ZnSe) on the supporting arms of ZnO nanotetrapods, which have a 1D nanowire structure, through the combination of ion exchange and successive deposition assembly. This resulted in highly crystalline and highly oriented quasi-QWs along the whole axial direction of the arms of the nanotetrapod because a transition buffer layer (Zn(x)Cd(1-x)Se) was formed and in turn reduced the lattice mismatch and surface defects. Significantly, such a barrier-confined QW emits excitonic light ∼17 times stronger than the heterojunction (HJ)-type structure (ZnSe/CdSe, HJ) at the single-particle level. Time-resolved photoluminescence from ensemble QWs exhibits a lifetime of 10 ns, contrasting sharply with ∼300 ps for the control HJ sample. Single-particle PL and Raman spectra suggest that the barrier layer of QW has completely removed the surface trap states on the HJ and restored or upgraded the photoelectric properties of the semiconductor layer. Therefore, this deliberate heteroepitaxial growth protocol on the supporting nanotetrapod has realized a several micrometer long QW structure with high mechanical robustness and high photoelectric quality. We envision that such QWs integrated on 1D nanostructures will largely improve the performance of solar cells and bioprobes, among others.
authors.affiliation: Nano Science and Technology Program, Department of Chemistry, and ‡Department of Physics, William Mong Institute of Nano Science and Technology, The Hong Kong University of Science and Technology , Clear Water Bay, Kowloon, Hong Kong.
authors.forename: Keyou
authors.initials: K
authors.lastname: Yan
authors.forename: Lixia
authors.initials: L
authors.lastname: Zhang
authors.forename: Qin
authors.initials: Q
authors.lastname: Kuang
authors.forename: Zhanhua
authors.initials: Z
authors.lastname: Wei
authors.forename: Ya
authors.initials: Y
authors.lastname: Yi
authors.forename: Jiannong
authors.initials: J
authors.lastname: Wang
authors.forename: Shihe
authors.initials: S
authors.lastname: Yang
mesh_terms: D019187:Cadmium Compounds / Q000737:chemistry; D049449:Luminescence; D055595:Mechanical Phenomena; D008958:Models, Molecular; D008968:Molecular Conformation; D049329:Nanostructures / Q000737:chemistry*; D018036:Selenium Compounds / Q000737:chemistry; D012666:Semiconductors; D012996:Solutions; D014835:Volatilization; D017967:Zinc Compounds / Q000737:chemistry; D015034:Zinc Oxide / Q000737:chemistry
chemical_list: D019187:Cadmium Compounds; D018036:Selenium Compounds; D012996:Solutions; D017967:Zinc Compounds; C058667:cadmium selenide; C044696:zinc selenide; D015034:Zinc Oxide