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Efficient nitrogen incorporation in ZnO nanowires.

Stehr JE, Chen WM, Reddy NK, Tu CW, Buyanova IA - Sci Rep (2015)

Bottom Line: The incorporated nitrogen atoms are concluded to mainly reside at oxygen sites (NO).The NO centers are suggested to be located in proximity to the NW surface, based on their reduced optical ionization energy as compared with that in bulk.This implies a lower defect formation energy at the NW surface as compared with its bulk value, consistent with theoretical predictions.

View Article: PubMed Central - PubMed

Affiliation: Linköping University, Department of Physics, Chemistry and Biology, Linköping, 581 83, Sweden.

ABSTRACT
One-dimensional ZnO nanowires (NWs) are a promising materials system for a variety of applications. Utilization of ZnO, however, requires a good understanding and control of material properties that are largely affected by intrinsic defects and contaminants. In this work we provide experimental evidence for unintentional incorporation of nitrogen in ZnO NWs grown by rapid thermal chemical vapor deposition, from electron paramagnetic resonance spectroscopy. The incorporated nitrogen atoms are concluded to mainly reside at oxygen sites (NO). The NO centers are suggested to be located in proximity to the NW surface, based on their reduced optical ionization energy as compared with that in bulk. This implies a lower defect formation energy at the NW surface as compared with its bulk value, consistent with theoretical predictions. The revealed facilitated incorporation of nitrogen in ZnO nanostructures may be advantageous for realizing p-type conducting ZnO via N doping. The awareness of this process can also help to prevent such unintentional doping in structures with desired n-type conductivity.

No MeSH data available.


(a) An SEM overview image of the studied ZnO NWs under a tilted view of 45°. (b) a magnified SEM image of a single ZnO NW. (c) XRD diffractogram of the studied ZnO NWs.
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f1: (a) An SEM overview image of the studied ZnO NWs under a tilted view of 45°. (b) a magnified SEM image of a single ZnO NW. (c) XRD diffractogram of the studied ZnO NWs.

Mentions: Figure 1(a) shows a representative scanning electron microscopy (SEM) image of the investigated ZnO NWs. A magnified image from a single NW is shown in Fig. 1(b). Most of the NWs are found to be vertically aligned along the crystallographic [0001] axis and exhibit a uniform size distribution with an average length and diameter of 30 μm and 100 nm, respectively. Some of the NWs are, however, randomly tilted by up to 20°. The excellent structural quality was further confirmed from performed x-ray diffraction (XRD) experiments, The XRD spectra of the ZnO NWs contain four peaks which can be assigned to ZnO (001) and (002) reflexes, Au and Al2O3 - see Fig. 1(c). The latter two reflexes are expected since the NWs were grown on an Al2O3 substrate and Au was used as a catalyst. The XRD results confirm that the NWs are preferentially oriented along the crystallographic c-axis ([0001] direction), since the calculated d-spacing of the major reflex (2θ = 34.4°, d = 0.261 nm) matches that expected for hexagonal ZnO. The full width at half maximum (FWHM) of the main ZnO reflex was found to be 0.27°, indicative of the high quality ZnO.


Efficient nitrogen incorporation in ZnO nanowires.

Stehr JE, Chen WM, Reddy NK, Tu CW, Buyanova IA - Sci Rep (2015)

(a) An SEM overview image of the studied ZnO NWs under a tilted view of 45°. (b) a magnified SEM image of a single ZnO NW. (c) XRD diffractogram of the studied ZnO NWs.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4547102&req=5

f1: (a) An SEM overview image of the studied ZnO NWs under a tilted view of 45°. (b) a magnified SEM image of a single ZnO NW. (c) XRD diffractogram of the studied ZnO NWs.
Mentions: Figure 1(a) shows a representative scanning electron microscopy (SEM) image of the investigated ZnO NWs. A magnified image from a single NW is shown in Fig. 1(b). Most of the NWs are found to be vertically aligned along the crystallographic [0001] axis and exhibit a uniform size distribution with an average length and diameter of 30 μm and 100 nm, respectively. Some of the NWs are, however, randomly tilted by up to 20°. The excellent structural quality was further confirmed from performed x-ray diffraction (XRD) experiments, The XRD spectra of the ZnO NWs contain four peaks which can be assigned to ZnO (001) and (002) reflexes, Au and Al2O3 - see Fig. 1(c). The latter two reflexes are expected since the NWs were grown on an Al2O3 substrate and Au was used as a catalyst. The XRD results confirm that the NWs are preferentially oriented along the crystallographic c-axis ([0001] direction), since the calculated d-spacing of the major reflex (2θ = 34.4°, d = 0.261 nm) matches that expected for hexagonal ZnO. The full width at half maximum (FWHM) of the main ZnO reflex was found to be 0.27°, indicative of the high quality ZnO.

Bottom Line: The incorporated nitrogen atoms are concluded to mainly reside at oxygen sites (NO).The NO centers are suggested to be located in proximity to the NW surface, based on their reduced optical ionization energy as compared with that in bulk.This implies a lower defect formation energy at the NW surface as compared with its bulk value, consistent with theoretical predictions.

View Article: PubMed Central - PubMed

Affiliation: Linköping University, Department of Physics, Chemistry and Biology, Linköping, 581 83, Sweden.

ABSTRACT
One-dimensional ZnO nanowires (NWs) are a promising materials system for a variety of applications. Utilization of ZnO, however, requires a good understanding and control of material properties that are largely affected by intrinsic defects and contaminants. In this work we provide experimental evidence for unintentional incorporation of nitrogen in ZnO NWs grown by rapid thermal chemical vapor deposition, from electron paramagnetic resonance spectroscopy. The incorporated nitrogen atoms are concluded to mainly reside at oxygen sites (NO). The NO centers are suggested to be located in proximity to the NW surface, based on their reduced optical ionization energy as compared with that in bulk. This implies a lower defect formation energy at the NW surface as compared with its bulk value, consistent with theoretical predictions. The revealed facilitated incorporation of nitrogen in ZnO nanostructures may be advantageous for realizing p-type conducting ZnO via N doping. The awareness of this process can also help to prevent such unintentional doping in structures with desired n-type conductivity.

No MeSH data available.