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The Luminescent Inhomogeneity and the Distribution of Zinc Vacancy-Related Acceptor-Like Defects in N-Doped ZnO Microrods

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ABSTRACT

Vertically aligned N-doped ZnO microrods with a hexagonal symmetry were fabricated via the chemical vapor transport with abundant N2O as both O and N precursors. We have demonstrated the suppression of the zinc interstitial-related shallow donor defects and have identified the zinc vacancy-related shallow and deep acceptor states by temperature variable photoluminescence in O-rich growth environment. Through spatially resolved cathodoluminescence spectra, we found the luminescent inhomogeneity in the sample with a core-shell structure. The deep acceptor-isolated VZn and the shallow acceptor VZn-related complex or clusters mainly distribute in the shell region.

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The SR-CL spectra and monochromatic images of a single N-doped ZnO MR performed with an accelerating voltage of 15 kV at 100 K. a The top view SEM image of the selected MR. b The CL monochromatic mapping of the MR taken at 3.306 eV. c The CL monochromatic mapping of the MR taken at 2.480 eV. d The PL spectrum measured at 100 K. e The CL spectrum obtained in spot mode from the center of the MR. f The CL spectrum obtained in spot mode from the edge of the MR
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Fig6: The SR-CL spectra and monochromatic images of a single N-doped ZnO MR performed with an accelerating voltage of 15 kV at 100 K. a The top view SEM image of the selected MR. b The CL monochromatic mapping of the MR taken at 3.306 eV. c The CL monochromatic mapping of the MR taken at 2.480 eV. d The PL spectrum measured at 100 K. e The CL spectrum obtained in spot mode from the center of the MR. f The CL spectrum obtained in spot mode from the edge of the MR

Mentions: Figure 6a shows the top view SEM image of one single hexagonally shaped N-doped ZnO MR in the investigated area, while the CL monochromatic 2D mapping of this MR recorded at a photon energy of 3.306 eV (375 nm) and 2.480 eV (500 nm) are shown in Fig. 6b, c, respectively. It can be noticed that the ultraviolet luminescence is stronger at the center of the MR, but in contrast, the green band luminescence mainly originates from the edge within a thickness of around 200–300 nm. Taking the advantage of high spatial resolution of the CL technique, Fig. 6e, f presents two CL spectra obtained in spot mode from the center and edge, respectively. Figure 6d shows the 100 K PL spectrum for identification of the optical transitions in the CL spectra. By comparing the CL spectra with the PL spectrum, the 3.306 eV peak corresponds to the eA0 while the 2.480 eV peak corresponds to the GB. Owing to the width of CL spectra that are much larger than that of the PL, peak deconvolution process has been employed for the CL spectra according to the well-resolved PL peaks. As can be seen from the deconvoluted components, the intensified eA0 emission at the center observed in Fig. 6b actually originates from the contribution of FX and its first LO-phonon replica whereas the actual intensity of eA0 emission at the center is weaker than that at the edge. As the eA0 is linked to the shallow acceptors, the result indicates that more shallow acceptors are located along the edge of the MR. For the GB luminescence, the integrated intensity ratio of the GB/NBE is 0.179 and 0.342 for center and edge, respectively, indicating that more isolated VZn defects are located near the edge area, similar to the monochromatic observation from Fig. 6c.Fig. 6


The Luminescent Inhomogeneity and the Distribution of Zinc Vacancy-Related Acceptor-Like Defects in N-Doped ZnO Microrods
The SR-CL spectra and monochromatic images of a single N-doped ZnO MR performed with an accelerating voltage of 15 kV at 100 K. a The top view SEM image of the selected MR. b The CL monochromatic mapping of the MR taken at 3.306 eV. c The CL monochromatic mapping of the MR taken at 2.480 eV. d The PL spectrum measured at 100 K. e The CL spectrum obtained in spot mode from the center of the MR. f The CL spectrum obtained in spot mode from the edge of the MR
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC5120051&req=5

Fig6: The SR-CL spectra and monochromatic images of a single N-doped ZnO MR performed with an accelerating voltage of 15 kV at 100 K. a The top view SEM image of the selected MR. b The CL monochromatic mapping of the MR taken at 3.306 eV. c The CL monochromatic mapping of the MR taken at 2.480 eV. d The PL spectrum measured at 100 K. e The CL spectrum obtained in spot mode from the center of the MR. f The CL spectrum obtained in spot mode from the edge of the MR
Mentions: Figure 6a shows the top view SEM image of one single hexagonally shaped N-doped ZnO MR in the investigated area, while the CL monochromatic 2D mapping of this MR recorded at a photon energy of 3.306 eV (375 nm) and 2.480 eV (500 nm) are shown in Fig. 6b, c, respectively. It can be noticed that the ultraviolet luminescence is stronger at the center of the MR, but in contrast, the green band luminescence mainly originates from the edge within a thickness of around 200–300 nm. Taking the advantage of high spatial resolution of the CL technique, Fig. 6e, f presents two CL spectra obtained in spot mode from the center and edge, respectively. Figure 6d shows the 100 K PL spectrum for identification of the optical transitions in the CL spectra. By comparing the CL spectra with the PL spectrum, the 3.306 eV peak corresponds to the eA0 while the 2.480 eV peak corresponds to the GB. Owing to the width of CL spectra that are much larger than that of the PL, peak deconvolution process has been employed for the CL spectra according to the well-resolved PL peaks. As can be seen from the deconvoluted components, the intensified eA0 emission at the center observed in Fig. 6b actually originates from the contribution of FX and its first LO-phonon replica whereas the actual intensity of eA0 emission at the center is weaker than that at the edge. As the eA0 is linked to the shallow acceptors, the result indicates that more shallow acceptors are located along the edge of the MR. For the GB luminescence, the integrated intensity ratio of the GB/NBE is 0.179 and 0.342 for center and edge, respectively, indicating that more isolated VZn defects are located near the edge area, similar to the monochromatic observation from Fig. 6c.Fig. 6

View Article: PubMed Central - PubMed

ABSTRACT

Vertically aligned N-doped ZnO microrods with a hexagonal symmetry were fabricated via the chemical vapor transport with abundant N2O as both O and N precursors. We have demonstrated the suppression of the zinc interstitial-related shallow donor defects and have identified the zinc vacancy-related shallow and deep acceptor states by temperature variable photoluminescence in O-rich growth environment. Through spatially resolved cathodoluminescence spectra, we found the luminescent inhomogeneity in the sample with a core-shell structure. The deep acceptor-isolated VZn and the shallow acceptor VZn-related complex or clusters mainly distribute in the shell region.

No MeSH data available.


Related in: MedlinePlus