(Color online) Field emission scanning electron microscopy images: (a) undoped ZnO NWs, (b) after Ti+ implantation and subsequent annealing in Ar, and (c) EDS spectra of the Ti-doped ZnO NWs.
(Color online) XRD patterns of the Ti-doped ZnO NWs (1 at. % and 2 at. %) annealed in Ar compared with that of the undoped ZnO NWs (0 at. %).
(Color online) Low-magnification TEM images of the ZnO NW (a) undoped and (b) after Ti+ implantation and subsequent annealing in Ar. (c), (d) High-resolution TEM images of the corresponding ZnO NWs. Insets are the corresponding SAD patterns [from the circled area in (a) and (b)].
(Color online) (a) TEM image of the Ti-doped ZnO NWs and (b)–(d) energy-dispersive spectroscopy elemental mapping of Zn, O, and Ti, respectively.
(Color online) CL spectra of the as-grown and Ti ion–implanted ZnO NWs.
(Color online) I–V curves of (a) undoped, (b) 1 at. % Ti doped, and (c) 2 at. % Ti doped ZnO NWs connected to the Al electrodes at 300 K. Each inset shows an FE-SEM image of NW and electrodes. Results for structures having diameter and length of (a) 100 nm, 4.5 μm; (b) 100 nm, 3.5 μm; and (c) 100 nm, 6.5 μm.
(Color online) (a)–(d) Sequential FE-SEM images of four typical bending cases of the Ti-doped ZnO NW. (e) A series of representative I–V curves of the ZnO NW, corresponding to the bending cases in (a)–(d).
(Color online) (a) SEM image of the single Ti-doped ZnO NW and the measured electrodes, corresponding to curve C in Fig. 7(e). (b) Schematic diagram of the M-S-M structure and its equivalent circuit. EFS and EFD denote the Fermi level of the source (metal W) and drain (metal W) electrodes respectively, Φb1 and Φb2 denote the corresponding Schottky barrier heights at the two contacts, and ξ denotes the distance between the bottom of the conductance band and the Fermi level of the semiconducting NW. (c) Band diagram showing the bending of the bands at the metal-semiconductor contacts and under applied voltage V. (d) A typical ln I–V curve of the Ti-doped ZnO NW at lower bias from Fig. 7(e) (curve C).
Data for doped ZnO NWs. Values are given on Ti content, electron carrier concentration (n) and optical band gap (Eg).
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