H Hou et al. /Solid State Sciences 7(2005)45-51 Fig.6. FE-SEM images for the as-synthesized ZnO epitaxial whiskers Fig. 7. TEM and SAED image of Zno epitaxial whiskers(pH=8, 110C, (pH=8, 110C, 12 h).(a) The panoramic morphology of Zno epitaxial 12 h).(a)The TEM image of overview ZnO epitaxial whiskers (b)The whiskers. ( b) The edge image of ZnO epitaxial whiskers. (c)The side face SAED pattem of the epitaxial whiskers. (c)The TEM image of individual image of Zno epitaxial whiskers. symmetrically epitaxial whisker.(d) The TEM image of one special single ZnO epitaxial whisker. Fig. 6. Fig. 6(a), the panoramic morphology of the sample, shows that the sample consists of epitaxial whiskers with straight and symmetrical whiskers. The image of some sep- b: epitaxial whiskers arated independent whiskers suggests that the whisker has nearly smooth, well-defined crystallographic facets and reg- ular prismatic hexagon, with the width of 2 um and angles about 1200, respectively. The edge image of ZnO epitaxial whiskers, as shown in Fig. 6(b), clearly exhibits two hexag - onal prism united together with end facet. The side face image of ZnO epitaxial whiskers(Fig. 6(c), which accords well with the TEM results. showed that the individual Zno epitaxial whisker, which has nearly smooth face, extending outside continuously without curving and clearly show sym- metrical feature Further morphology characterization of the ZnO epitax Wavelength/nm ial whiskers was performed using TEM shown in Fig. 7, Fig 8. Room-temperature PL spectrum of the as-grown ZnO tubular which accords well to the FesEm results. Fig. 7(a) show whiskers and epitaxial whiskers the general morphology of ZnO epitaxial whiskers prepared in which the symmetrically epitaxial whiskers inextricably Room-temperature photoluminescence(PL)of the as- united together by two single whiskers. Most of the epi- grown products were studied and the Pl spectrum the Zno taxial whiskers have fairly uniform diameters of around tubular whiskers and epitaxial whiskers were shown in 4 um and the length of about 10 um. The SAED pattern of Fig 8. Fig 8(a), showing PL spectrum of as-grown ZnO Fig. 7(b), taken on the Zno epitaxial whisker, exhibits that tubular whiskers, consists of a strong shoulder emission the as-synthesized Zno epitaxial whiskers are single crys- band located at 400 and 408 nm, and a weak and broad tal with the oriented growth direction along c-axis. Different emission band centered at 533 nm. The two shoulder nearly parts of this whisker show exactly the same electron pat overlapped violet emission(400, 408 nm), having slight red tern, indicating the single crystallinity of the whole single shift in the near band-edge emission, differ from the band whisker. Dozens of individual whiskers have been examined gap of bulk ZnO(around 380 nm)[16-18], which comes using this method, which confirmed their single crystallinity from the recombination of free exciton [12, 19]. The green Fig. 7(c)confirms the individual ZnO epitaxial whisker, emission at 533 nm is related to the singly ionized oxygen which has nearly smooth face, extending outside continu- vacancy, and this emission results from the recombination of ously without curving and clearly show symmetrical feature. photogenerated hole with a singly ionized charge state of the ig. 7(d) reveals the morphology of one special single Zno specific defect[20, 21]. The photoluminescence spectrum of hisker, whose perfect symmetrical structure clearly shows the as-grown ZnO epitaxial whiskers was shown in Fig. 8(b) the orientation adhesion in which a strong shoulder emission band located at 411 and48 H. Hou et al. / Solid State Sciences 7 (2005) 45–51 Fig. 6. FE-SEM images for the as-synthesized ZnO epitaxial whiskers (pH = 8, 110 ◦C, 12 h). (a) The panoramic morphology of ZnO epitaxial whiskers. (b) The edge image of ZnO epitaxial whiskers. (c) The side face image of ZnO epitaxial whiskers. Fig. 6. Fig. 6(a), the panoramic morphology of the sample, shows that the sample consists of epitaxial whiskers with straight and symmetrical whiskers. The image of some sep￾arated independent whiskers suggests that the whisker has nearly smooth, well-defined crystallographic facets and reg￾ular prismatic hexagon, with the width of 2 µm and angles about 120◦, respectively. The edge image of ZnO epitaxial whiskers, as shown in Fig. 6(b), clearly exhibits two hexag￾onal prism united together with end facet. The side face image of ZnO epitaxial whiskers (Fig. 6(c)), which accords well with the TEM results, showed that the individual ZnO epitaxial whisker, which has nearly smooth face, extending outside continuously without curving and clearly show sym￾metrical feature. Further morphology characterization of the ZnO epitax￾ial whiskers was performed using TEM shown in Fig. 7, which accords well to the FESEM results. Fig. 7(a) shows the general morphology of ZnO epitaxial whiskers prepared, in which the symmetrically epitaxial whiskers inextricably united together by two single whiskers. Most of the epi￾taxial whiskers have fairly uniform diameters of around 4 µm and the length of about 10 µm. The SAED pattern of Fig. 7(b), taken on the ZnO epitaxial whisker, exhibits that the as-synthesized ZnO epitaxial whiskers are single crys￾tal with the oriented growth direction along c-axis. Different parts of this whisker show exactly the same electron pat￾tern, indicating the single crystallinity of the whole single whisker. Dozens of individual whiskers have been examined using this method, which confirmed their single crystallinity. Fig. 7(c) confirms the individual ZnO epitaxial whisker, which has nearly smooth face, extending outside continu￾ously without curving and clearly show symmetrical feature. Fig. 7(d) reveals the morphology of one special single ZnO whisker, whose perfect symmetrical structure clearly shows the orientation adhesion. Fig. 7. TEM and SAED image of ZnO epitaxial whiskers (pH = 8, 110 ◦C, 12 h). (a) The TEM image of overview ZnO epitaxial whiskers. (b) The SAED pattern of the epitaxial whiskers. (c) The TEM image of individual symmetrically epitaxial whisker. (d) The TEM image of one special single ZnO epitaxial whisker. Fig. 8. Room-temperature PL spectrum of the as-grown ZnO tubular whiskers and epitaxial whiskers. Room-temperature photoluminescence (PL) of the as￾grown products were studied and the PL spectrum the ZnO tubular whiskers and epitaxial whiskers were shown in Fig. 8. Fig. 8(a), showing PL spectrum of as-grown ZnO tubular whiskers, consists of a strong shoulder emission band located at 400 and 408 nm, and a weak and broad emission band centered at 533 nm. The two shoulder nearly￾overlapped violet emission (400, 408 nm), having slight red shift in the near band-edge emission, differ from the band gap of bulk ZnO (around 380 nm) [16–18], which comes from the recombination of free exciton [12,19]. The green emission at 533 nm is related to the singly ionized oxygen vacancy, and this emission results from the recombination of photogenerated hole with a singly ionized charge state of the specific defect [20,21]. The photoluminescence spectrum of the as-grown ZnO epitaxial whiskers was shown in Fig. 8(b), in which a strong shoulder emission band located at 411 and