Synthesis And Physical Properties Of Doped ZnO Quasi-one-dimensional Superlattice Nanostructures

The synthesis, characterization and physical properties studying of quasi-one-dimensional (1D) nanomaterials, including nanowires (rods), nanoribbons (belts), nanotubes, heterostructure and superlattice nanowires (ribbons) are always the center spots of namomaterials research area. Among these, the preparing and physical properties studying of heterostructure and superlattice nanostructures are of even more important, as it is the critical case for the success of future optical and electronic nanodevice and integrate circuits performance. In recent years, different kinds and different shape of quasi-1D nanomaterials heterostrtures and superlattice have been successfully synthesized.Owing to the better optical and electronic properties, the homogenous compounds of InMO₃(ZnO)_m have attracted much attention recently. Huge improgress have been obtained on quasi-1D InMO₃(ZnO)_m nanomaterials and a large of them have been successfully synthesized. Yet to now, all superlattice nanowires reported are not periodical and little physcial properties such as photoluminescence have been studied. So it is important to prepared periodical InMO₃(ZnO)_m superlattice nanostructures with different shapes and studying their further physical properties. The main contents, focusing on the preparing, characterization, physical properties studying of In₂O₃(ZnO)_m planar superlattice nanoribbons and InGaO₃(ZnO)_m axial superlattice nanowires, are summarized as:1. synthesis and electrical properties studying of In₂O₃(ZnO)_m planar superlattice nanoribbons.By the use of chemical vapor transports self assembly method, we successfully synthesized In₂O₃(ZnO)_m planar superlattice nanoribbons. Combined with XRD results, we verified the formation of In₂O₃(ZnO)₃ planar superlattice nanoribbons by analyzing the SAED pattern with the incident direction of electron beam perpendicular to the wide surface of a nanoribbon. We also give the translational relation between monoclinic cell and ZnO wurtzite cell and successfully index the obtained SAED with monoclinic structure. We mixed the In₂O₃(ZnO)_m planar superlattice nanoribbons with epoxy resin and cross cut the mixture to slices of about 200 run in thickness and obtained cross-sectional HRTEM image of a nanoribbon. The HRTEM image clearly shows the formation of superlattice structures. We also measure theâ… -â…¤properties of the obtained In₂O₃(ZnO)_m planar superlattice nanoribbons and the out put current can reach severalμA level, which is the highest results ever reported.2 Raman property of In₂O₃(ZnO)_m planar superlattice nanoribbonsThe formation of superlattice structures change the local crystal structure of ZnO wurtzite and thus the vibrational property. We compared the Raman spectra of In doped ZnO nanoribbons with and without superlattice structures. Beside the intensity of ZnO characteristic mode E₂(high) getting low and broading, there is a new vibrational mode (AM) around 621cm^-1 in Raman spectra of products containing In₂O₃(ZnO)_m planar superlattice nanoribbons. By the analysis of the local crystal structure of In₂O₃(ZnO)_m planar superlattice nanoribbons, we infer that this new mode is attributed to an O atom that bonded with three In atoms and one Zn atom in a distorted tetrahedron coordinatio in the interface between In-O layer and In/Zn-O layers in the superlattice of nanoribbons and be the characteristic vibrational mode of In₂O₃(ZnO)_m superlattice nanoribbons.3 Synthesis and photoluminescene properties of InGaO₃(ZnO)_m axial superlattice nanowiresWe havealso successfully synthesized InGaO₃(ZnO)₃ axial superlattice nanowires using chemical vapor transport self assembly method. HRTEM images show the nanowires having layered superlattice structure with perfect commensurability and and exactly four In/Zn-O layers between two adjacent In-O layers. EDS spectra indicates that a large amount of Zn atoms in Ga/Zn-O layers.are substituted by In atoms. We have also found some InGaO₃(ZnO)₅ axial superlattice nanowires and InGaO₃(ZnO)_m lateral superlattice nanoribbons formation in the as synthesized products. By the analysis of PL spectra of the as synthesized products, we infer that the peaks around 3.23eV is the near band edge emission of InGaO₃(ZnO)_m superlattice nanowires.4 Syntheis and physical properties studying of several kinds of complexed ZnO nanostructures.We successfully prepared complexed nanostructures of ZnO nanodisks/nanoribbons by directly evaporating the mixture of ZnO and In₂O₃ powders. The wide surface of the nanodisks is ZnO (0001) and the growth direction of ZnO nanoribbons is [11-20] with the wide surface (0001). The band gap emission redsift to 409nm cause by In doping was obtained in photoluminescence (PL) spectra. Under different experimental condition, we also successfully prepared the complexed nanostructures of ZnO nanorods/nanoribbons.By evaporating the powders of ZnO and MnO₂ displayed at different places, we obtained ZnO nanotowers and ZnO nanorods arrays with layered structures. XRD result indicates the crystal structures of ZnO wurtzite. All the complexed nanostructures obtained above enrich the morphology of ZnO nanostructures.