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Optics Express

Optics Express

  • Editor: Andrew M. Weiner
  • Vol. 22, Iss. 7 — Apr. 7, 2014
  • pp: 8617–8623
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Extended photo-response of ZnO/CdS core/shell nanorods fabricated by hydrothermal reaction and pulsed laser deposition

Qin Yang, Yanli Li, Zhigao Hu, Zhihua Duan, Peipei Liang, Jian Sun, Ning Xu, and Jiada Wu  »View Author Affiliations


Optics Express, Vol. 22, Issue 7, pp. 8617-8623 (2014)
http://dx.doi.org/10.1364/OE.22.008617


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Abstract

Heterogenous nanostructures shaped with CdS covered ZnO (ZnO/CdS) core/shell nanorods (NRs) are fabricated on indium-tin-oxide by pulsed laser deposition of CdS on hydrothermally grown ZnO NRs and characterized through morphology examination, structure characterization, photoluminescence and optical absorption measurements. Both the ZnO cores and the CdS shells are hexagonal wurtzite in structure. Compared with bare ZnO NRs, the fabricated ZnO/CdS core/shell NRs present an extended photo-response and have optical properties corresponding to the two excitonic band-gaps of ZnO and CdS as well as the effective band-gap formed between the conduction band minimum of ZnO and the valence band maximum of CdS.

© 2014 Optical Society of America

1. Introduction

Nanosized heterostructures constructed of two or more semiconductors have attracted much attention because of their modified properties and improved performance compared with the constructing materials [1

1. J. van Embden, J. Jasieniak, D. E. Gómez, P. Mulvaney, and M. Giersig, “Review of the synthetic chemistry involved in the production of core/shell semiconductor nanocrystals,” Aust. J. Chem. 60(7), 457–471 (2007). [CrossRef]

4

4. S. Mokkapati, D. Saxena, N. Jiang, P. Parkinson, J. Wong-Leung, Q. Gao, H. H. Tan, and C. Jagadish, “Polarization tunable, multicolor emission from core-shell photonic III-V semiconductor nanowires,” Nano Lett. 12(12), 6428–6431 (2012). [CrossRef] [PubMed]

]. In this respect, nanostructured materials are superior to the bulk ones, since hetero-nanostructures can be constructed simply by surface modification or surface coating. ZnO is promising for various applications including photovoltaic processes and photocatalytic reactions [5

5. S. J. Pearton, D. P. Norton, K. Ip, Y. W. Heo, and T. Steiner, “Recent progress in processing and properties of ZnO,” Superlattices Microstruct. 34(1–2), 3–32 (2003). [CrossRef]

]. Owing to its wide band-gap (3.37 eV), however, ZnO itself can only be used in the ultraviolet (UV) region. Therefore, ZnO has been proposed to form heterostructures with a narrower band-gap semiconductor to extend the spectral region of photo-response [1

1. J. van Embden, J. Jasieniak, D. E. Gómez, P. Mulvaney, and M. Giersig, “Review of the synthetic chemistry involved in the production of core/shell semiconductor nanocrystals,” Aust. J. Chem. 60(7), 457–471 (2007). [CrossRef]

,2

2. K. Wang, J. J. Chen, W. L. Zhou, Y. Zhang, Y. F. Yan, J. Pern, and A. Mascarenhas, “Direct growth of highly mismatched type II ZnO/ZnSe core/shell nanowire arrays on transparent conducting oxide substrates for solar cell applications,” Adv. Mater. 20(17), 3248–3253 (2008). [CrossRef]

]. With a narrower band-gap (2.4 eV) and the same crystal structure [6

6. M. C. Baykul and N. Orhan, “Band alignment of Cd(1 −x)ZnxS produced by spray pyrolysis method,” Thin Solid Films 518(8), 1925–1928 (2010). [CrossRef]

,7

7. A. A. Ziabari and F. E. Ghodsi, “Growth, characterization and studying of sol–gel derived CdS nanoscrystalline thin films incorporated in polyethyleneglycol: Effects of post-heat treatment,” Sol. Energy Mater. Sol. Cells 105, 249–262 (2012). [CrossRef]

], CdS has a good compatibility with ZnO and is an ideal material to sensitize ZnO and construct type-II heterostructures with ZnO [8

8. C. M. Li, T. Ahmed, M. G. Ma, T. Edvinsson, and J. F. Zhu, “A facile approach to ZnO/CdS nanoarrays and their photocatalytic and photoelectrochemical properties,” Appl. Catal. B 138, 175−183 (2013).

,9

9. S. Khanchandani, S. Kundu, A. Patra, and A. K. Ganguli, “Shell thickness dependent photocatalytic properties of ZnO/CdS core−shell nanorods,” J. Phys. Chem. C 116(44), 23653–23662 (2012). [CrossRef]

]. The band alignment of ZnO-CdS heterostructures contributes to spatially separating electrons and holes and is favorable for photovoltaic and photocatalytic applications [1

1. J. van Embden, J. Jasieniak, D. E. Gómez, P. Mulvaney, and M. Giersig, “Review of the synthetic chemistry involved in the production of core/shell semiconductor nanocrystals,” Aust. J. Chem. 60(7), 457–471 (2007). [CrossRef]

,2

2. K. Wang, J. J. Chen, W. L. Zhou, Y. Zhang, Y. F. Yan, J. Pern, and A. Mascarenhas, “Direct growth of highly mismatched type II ZnO/ZnSe core/shell nanowire arrays on transparent conducting oxide substrates for solar cell applications,” Adv. Mater. 20(17), 3248–3253 (2008). [CrossRef]

]. Using ZnO as the core material and CdS as the shell material, one-dimensional rod-like or wire-like ZnO-CdS in particular, is superior in both the surface-to-volume ratio for modifying the surface [10

10. Z. M. Wu, Y. Zhang, J. J. Zheng, X. G. Lin, X. H. Chen, B. W. Huang, H. Q. Wang, K. Huang, S. P. Li, and J. Y. Kang, “An all-inorganic type-II heterojunction array with nearly full solar spectral response based on ZnO/ZnSe core/shell nanowires,” J. Mater. Chem. 21(16), 6020–6026 (2011). [CrossRef]

] and the lateral size for reducing the nonradiative recombination and carrier scattering loss [2

2. K. Wang, J. J. Chen, W. L. Zhou, Y. Zhang, Y. F. Yan, J. Pern, and A. Mascarenhas, “Direct growth of highly mismatched type II ZnO/ZnSe core/shell nanowire arrays on transparent conducting oxide substrates for solar cell applications,” Adv. Mater. 20(17), 3248–3253 (2008). [CrossRef]

,11

11. Y. Zhang, M. D. Sturge, K. Kash, A. S. Gozdz, L. T. Florez, and J. P. Harbison, “Temperature dependence of luminescence efficiency, exciton transfer, and exciton localization in GaAs/AlxGa1-xAs quantum wires and quantum dots,” Phys. Rev. B Condens. Matter 51(19), 13303–13314 (1995). [CrossRef] [PubMed]

]. An extended spectral region for light absorption and a suppressed loss of photogenerated carriers can be expected.

In this study, ZnO-CdS heterostructures in the form of CdS covered ZnO (ZnO/CdS) nanorods (NRs) constructed of wurtzite ZnO cores and wurtzite CdS shells were fabricated. After morphology examination and structure characterization, the optical properties of the ZnO/CdS core/shell NRs were studied through the measurements of photoluminescence (PL) and optical absorption and the discussion of the relevant mechanisms.

2. Experimental details

ZnO NRs were first grown on nanocrystalline ZnO seeded indium-tin-oxide (ITO) substrates by hydrothermal reaction at 90 °C in the precursor solution of 0.04 M hexamethylenetetramine (HMT) and 0.04 M zinc nitrate hexahydrate [Zn(NO3)2⋅6H2O] resolved in 1 L de-ionized water [12

12. N. Xu, Y. Cui, Z. G. Hu, W. L. Yu, J. Sun, N. Xu, and J. D. Wu, “Photoluminescence and low-threshold lasing of ZnO nanorod arrays,” Opt. Express 20(14), 14857–14863 (2012). [CrossRef] [PubMed]

]. The grown ZnO NRs were served as the cores over which CdS coatings were deposited by pulsed laser deposition as the shells. The second harmonic of a Q-switched Nd: YAG laser (wavelength 532 nm, pulse duration 5 ns, repetition rate 10 Hz) was used to ablate a CdS target after being focused (spot size ~1.2 mm2 and fluence ~2 J/cm2). The deposition of CdS coatings was performed in vacuum (~10−4 Pa) at room temperature for 20 min. The fabricated ZnO/CdS NRs were then annealed in a flowing N2 atmosphere (~105 Pa) at temperatures up to 500 °C for 60 min.

The morphologies of bare ZnO NRs and ZnO/CdS core/shell NRs were examined by field-emission scanning electron microscopy (FESEM, Hitachi S-4800). The sample structure was characterized by X-ray diffraction (XRD, Rigaku D/MAX 2550 VB/PC) and Raman scattering (Jobin-Yvon LabRAM-1B). With the excitation by a 325-nm He-Cd laser beam, room-temperature and low-temperature PL spectra were recorded by an intensified charge-coupled device (ICCD, iStar DH720, Andor) equipped on a 0.5 m spectrometer (SpectraPro-500i, Acton). Absorption spectra were measured in the UV−near-infrared (near-IR) range using a Shimutsu UV3101PC Photo-Spectrometer.

3. Results and discussion

3.1 Morphology and structure

Figure 1(a)
Fig. 1 FESEM images of bare ZnO NRs (a) and ZnO/CdS core/shell NRs (b).
shows the FESEM images of the hydrothermally grown ZnO NRs, indicating that the bare ZnO NRs grew nearly oriented with their axes perpendicular to the substrate and are almost shaped with hexagonal prisms having an average diameter of 90 nm and length of 2 um. Figure 1(b) shows that the ZnO NRs are uniformly covered with CdS from bottom to top, forming ZnO/CdS core/shell NRs. The CdS covered ZnO NRs exhibit increased diameters and rough surfaces compared with the bare ZnO NRs. After annealing, no obvious changes in the morphology were observed.

Figure 2
Fig. 2 XRD patterns of bare ZnO NRs (1), as-fabricated ZnO/CdS core/shell NRs (2), and annealed ZnO/CdS core/shell NRs at 300 °C (3) and 500 °C (4).
shows the XRD patterns taken from the bare ZnO NRs and the ZnO/CdS core/shell NRs. For the bare ZnO NRs, a strong diffraction peaking at 2θ = 34.42° with a full width at half-maximum (FWHM) of 0.11° dominates the XRD pattern. This peak is indexed to the (002) diffraction of wurtzite ZnO (JCPDS: 36-1451). Besides those diffracted from the ITO substrate (marked with *), three prominent peaks and three weak ones are resolved. They can be indexed to the (101), (102), (103), (100), (110) and (112) diffractions of wurtzite ZnO, respectively. For the ZnO/CdS core/shell NRs, additional diffractions appear including a broad one at 2θ = 26.65° (FWHM = 0.56°) and two weak ones. They are attributed to the (002), (101) and (110) diffractions of wurtzite CdS (JCPDS: 41-1049). Therefore, the fabricated ZnO/CdS core/shell NRs are composed of wurtzite ZnO cores and wurtzite CdS shells. After annealing, the diffractions from CdS become stronger and an additional peak corresponding to the (100) plane of wurtzite CdS appears, indicating an improvement in the crystal structure due to the annealing treatment.

Figure 3(a)
Fig. 3 (a) Raman spectra of bare ZnO NRs and as-fabricated ZnO/CdS NRs (the inset shows magnified Raman spectrum of bare ZnO NRs); (b) Raman spectra of as-fabricated ZnO/CdS NRs and annealed ZnO/CdS NRs. (1−bare ZnO NRs, 2−as-fabricated ZnO/CdS NRs, 3−ZnO/CdS NRs annealed at 300 °C, 4−ZnO/CdS NRs annealed at 500 °C).
shows the Raman spectra of the bare ZnO NRs and the as-fabricated ZnO/CdS core/shell NRs. A prominent peak at 98 cm−1 and a weak one at ~436 cm−1 are recognized in the Raman spectrum of the bare ZnO NRs (spectrum 1 and the inset). They correspond to the low- and high-frequency branches of the non-polar optical phonon modes [E2 (Low) and E2 (high)] of ZnO [13

13. T. C. Damen, S. P. S. Porto, and B. Tell, “Raman effect in zinc oxide,” Phys. Rev. 142(2), 570–574 (1966). [CrossRef]

,14

14. V. Pachauri, C. Subramaniam, and T. Pradeep, “Novel ZnO nanostructures over gold and silver nanoparticle assemblies,” Chem. Phys. Lett. 423(1–3), 240–246 (2006). [CrossRef]

]. After the deposition of CdS, the Raman spectrum is dominated by a strong peak at 299 cm−1 and a weak one around 598 cm−1 (spectrum 2). They correspond to the first-order longitudinal optical (1LO) mode of wurtzite CdS and its 2-phonon scattering processes (2LO) [15

15. R. C. C. Leite, J. F. Scott, and T. C. Damen, “Multiple-phonon resonant raman scattering in CdS,” Phys. Rev. Lett. 22(15), 780–782 (1969). [CrossRef]

]. The Raman measurements confirm the hexagonal wurtzite structure of the ZnO cores and the CdS shells. For the annealed ZnO/CdS core/shell NRs, the featureless background in the Raman spectra decreases significantly, as shown in Fig. 3(b), also confirming the improvement in the structure after annealing.

3.2. Photoluminescence

Figure 4(b) illustrates the PL spectra of the as-fabricated ZnO/CdS core/shell NRs at reduced temperatures and compares them with the room-temperature PL spectrum. The intensity of the UV emission increases significantly with an obvious blue shift and a much narrower width (FWHM ~5 nm at 10 K) as the temperature decreases. This can be explained in terms of the freeze-out of phonons and quenching of nonradiative recombination processes in ZnO at low temperatures [12

12. N. Xu, Y. Cui, Z. G. Hu, W. L. Yu, J. Sun, N. Xu, and J. D. Wu, “Photoluminescence and low-threshold lasing of ZnO nanorod arrays,” Opt. Express 20(14), 14857–14863 (2012). [CrossRef] [PubMed]

,16

16. W. Shan, W. Walukiewicz, J. W. Ager III, K. M. Yu, H. B. Yuan, H. P. Xin, G. Cantwell, and J. J. Song, “Nature of room-temperature photoluminescence in ZnO,” Appl. Phys. Lett. 86(19), 191911 (2005). [CrossRef]

]. The strong UV emission in the low-temperature PL also suggests that the absorption by the CdS coatings contributes little to the reduction in the measured room-temperature PL spectra of the ZnO/CdS core/shell NRs. With the decrease in temperature, in addition, the intensity of the broad visible luminescence also increases. Especially, a prominent emission band centered near 516 nm appears at low temperatures. This band corresponds to the NBE emission from CdS. The appearance of this emission and the increase of the wide visible luminescence can also be attributed to the quenching of nonradiative recombination in the sample at low temperatures.

3.3 Optical absorption

Figure 5
Fig. 5 Absorption spectra of ZnO NRs and ZnO/CdS NRs (1−bare ZnO NRs, 2−as-fabricated ZnO/CdS NRs, 3−ZnO/CdS NRs annealed at 300 °C, 4−ZnO/CdS NRs annealed at 500 °C).
shows that the bare ZnO NRs present a clear absorption edge near 380 nm corresponding to the excitonic band-gap of ZnO [5

5. S. J. Pearton, D. P. Norton, K. Ip, Y. W. Heo, and T. Steiner, “Recent progress in processing and properties of ZnO,” Superlattices Microstruct. 34(1–2), 3–32 (2003). [CrossRef]

,16

16. W. Shan, W. Walukiewicz, J. W. Ager III, K. M. Yu, H. B. Yuan, H. P. Xin, G. Cantwell, and J. J. Song, “Nature of room-temperature photoluminescence in ZnO,” Appl. Phys. Lett. 86(19), 191911 (2005). [CrossRef]

]. After being covered by CdS shells, the sample exhibits increased optical absorption in the visible to near-IR region and shows a second absorption edge near 510 nm corresponding to the excitonic band-gap of CdS [6

6. M. C. Baykul and N. Orhan, “Band alignment of Cd(1 −x)ZnxS produced by spray pyrolysis method,” Thin Solid Films 518(8), 1925–1928 (2010). [CrossRef]

,7

7. A. A. Ziabari and F. E. Ghodsi, “Growth, characterization and studying of sol–gel derived CdS nanoscrystalline thin films incorporated in polyethyleneglycol: Effects of post-heat treatment,” Sol. Energy Mater. Sol. Cells 105, 249–262 (2012). [CrossRef]

,17

17. K. Vanheusden, C. H. Seager, W. L. Warren, D. R. Tallant, and J. A. Voigt, “Correlation between photoluminescence and oxygen vacancies in ZnO phosphors,” Appl. Phys. Lett. 68(3), 403–405 (1996). [CrossRef]

]. Furthermore, additional absorption is found extending below the CdS band-gap into the near-IR, which could arise from an interfacial transition coupling a hole state in the CdS shell with an electron state in the ZnO core, i.e. the transition corresponding to the so-called effective band-gap formed between the conduction band minimum of ZnO and the valence band maximum of CdS [2

2. K. Wang, J. J. Chen, W. L. Zhou, Y. Zhang, Y. F. Yan, J. Pern, and A. Mascarenhas, “Direct growth of highly mismatched type II ZnO/ZnSe core/shell nanowire arrays on transparent conducting oxide substrates for solar cell applications,” Adv. Mater. 20(17), 3248–3253 (2008). [CrossRef]

,10

10. Z. M. Wu, Y. Zhang, J. J. Zheng, X. G. Lin, X. H. Chen, B. W. Huang, H. Q. Wang, K. Huang, S. P. Li, and J. Y. Kang, “An all-inorganic type-II heterojunction array with nearly full solar spectral response based on ZnO/ZnSe core/shell nanowires,” J. Mater. Chem. 21(16), 6020–6026 (2011). [CrossRef]

]. The spectral extension of the optical absorption is consistent with the red-shit of the visible luminescence from the CdS covered ZnO NRs. As a result, the ZnO/CdS core/shell NRs have a much broader absorption region than the bare ZnO NRs due to the band alignment in the heterostructures constructed of ZnO and CdS. For the annealed samples, in addition, the absorption decreases with increasing annealing temperature because of the improved structure, providing another evidence for the explanation that the reduction in the measured luminescence results mainly from the suppressed radiative recombination of photogenerated carriers, rather than the absorption of the exciting photons and the emitted photons by the CdS shells. The ZnO NRs covered with CdS shells therefore exhibit an enhanced charge separation and an extended photo-response compared with the bare ZnO NRs. The increased optical absorption and the extended photo-response region are expected to improve the utilization efficiency of solar energy and most favorable for photocatalytic reactions and photovoltaic processes.

4. Conclusions

Heterogeneous nanostructures in the form of aligned ZnO/CdS core/shell NRs have been fabricated on ITO substrates by pulsed laser deposition of CdS coatings on hydrothermally grown ZnO NRs. The fabricated hetero-nanostructures are constructed of wurtzite ZnO nanorod cores and wurtzite CdS shells. The photoluminescence from ZnO cores is significantly quenched by the CdS shells mainly because of the suppressed radiative recombination of photogenerated electrons and holes due to the enhanced charge separation in the hetero-nanostructures. The ZnO/CdS core/shell NRs exhibit increased optical absorption and an extended photo-response region compared with the bare ZnO NRs and present optical properties corresponding to the two excitonic band-gaps of wurtzite ZnO and wurtzite CdS as well as the effective band-gap formed between the conduction band minimum of ZnO and the valence band maximum of CdS.

Acknowledgments

This work is supported by the National Basic Research Program of China (2012CB934303) and the National Natural Science Foundation of China (11275051). Acknowledgment is also made to the Research Fund for the Doctoral Program of Higher Education of China (20110071110020).

References and links

1.

J. van Embden, J. Jasieniak, D. E. Gómez, P. Mulvaney, and M. Giersig, “Review of the synthetic chemistry involved in the production of core/shell semiconductor nanocrystals,” Aust. J. Chem. 60(7), 457–471 (2007). [CrossRef]

2.

K. Wang, J. J. Chen, W. L. Zhou, Y. Zhang, Y. F. Yan, J. Pern, and A. Mascarenhas, “Direct growth of highly mismatched type II ZnO/ZnSe core/shell nanowire arrays on transparent conducting oxide substrates for solar cell applications,” Adv. Mater. 20(17), 3248–3253 (2008). [CrossRef]

3.

Q. Yang, Y. Liu, C. F. Pan, J. Chen, X. N. Wen, and Z. L. Wang, “Largely enhanced efficiency in ZnO nanowire/p-polymer hybridized inorganic/organic ultraviolet light-emitting diode by piezo-phototronic effect,” Nano Lett. 13(2), 607–613 (2013). [CrossRef] [PubMed]

4.

S. Mokkapati, D. Saxena, N. Jiang, P. Parkinson, J. Wong-Leung, Q. Gao, H. H. Tan, and C. Jagadish, “Polarization tunable, multicolor emission from core-shell photonic III-V semiconductor nanowires,” Nano Lett. 12(12), 6428–6431 (2012). [CrossRef] [PubMed]

5.

S. J. Pearton, D. P. Norton, K. Ip, Y. W. Heo, and T. Steiner, “Recent progress in processing and properties of ZnO,” Superlattices Microstruct. 34(1–2), 3–32 (2003). [CrossRef]

6.

M. C. Baykul and N. Orhan, “Band alignment of Cd(1 −x)ZnxS produced by spray pyrolysis method,” Thin Solid Films 518(8), 1925–1928 (2010). [CrossRef]

7.

A. A. Ziabari and F. E. Ghodsi, “Growth, characterization and studying of sol–gel derived CdS nanoscrystalline thin films incorporated in polyethyleneglycol: Effects of post-heat treatment,” Sol. Energy Mater. Sol. Cells 105, 249–262 (2012). [CrossRef]

8.

C. M. Li, T. Ahmed, M. G. Ma, T. Edvinsson, and J. F. Zhu, “A facile approach to ZnO/CdS nanoarrays and their photocatalytic and photoelectrochemical properties,” Appl. Catal. B 138, 175−183 (2013).

9.

S. Khanchandani, S. Kundu, A. Patra, and A. K. Ganguli, “Shell thickness dependent photocatalytic properties of ZnO/CdS core−shell nanorods,” J. Phys. Chem. C 116(44), 23653–23662 (2012). [CrossRef]

10.

Z. M. Wu, Y. Zhang, J. J. Zheng, X. G. Lin, X. H. Chen, B. W. Huang, H. Q. Wang, K. Huang, S. P. Li, and J. Y. Kang, “An all-inorganic type-II heterojunction array with nearly full solar spectral response based on ZnO/ZnSe core/shell nanowires,” J. Mater. Chem. 21(16), 6020–6026 (2011). [CrossRef]

11.

Y. Zhang, M. D. Sturge, K. Kash, A. S. Gozdz, L. T. Florez, and J. P. Harbison, “Temperature dependence of luminescence efficiency, exciton transfer, and exciton localization in GaAs/AlxGa1-xAs quantum wires and quantum dots,” Phys. Rev. B Condens. Matter 51(19), 13303–13314 (1995). [CrossRef] [PubMed]

12.

N. Xu, Y. Cui, Z. G. Hu, W. L. Yu, J. Sun, N. Xu, and J. D. Wu, “Photoluminescence and low-threshold lasing of ZnO nanorod arrays,” Opt. Express 20(14), 14857–14863 (2012). [CrossRef] [PubMed]

13.

T. C. Damen, S. P. S. Porto, and B. Tell, “Raman effect in zinc oxide,” Phys. Rev. 142(2), 570–574 (1966). [CrossRef]

14.

V. Pachauri, C. Subramaniam, and T. Pradeep, “Novel ZnO nanostructures over gold and silver nanoparticle assemblies,” Chem. Phys. Lett. 423(1–3), 240–246 (2006). [CrossRef]

15.

R. C. C. Leite, J. F. Scott, and T. C. Damen, “Multiple-phonon resonant raman scattering in CdS,” Phys. Rev. Lett. 22(15), 780–782 (1969). [CrossRef]

16.

W. Shan, W. Walukiewicz, J. W. Ager III, K. M. Yu, H. B. Yuan, H. P. Xin, G. Cantwell, and J. J. Song, “Nature of room-temperature photoluminescence in ZnO,” Appl. Phys. Lett. 86(19), 191911 (2005). [CrossRef]

17.

K. Vanheusden, C. H. Seager, W. L. Warren, D. R. Tallant, and J. A. Voigt, “Correlation between photoluminescence and oxygen vacancies in ZnO phosphors,” Appl. Phys. Lett. 68(3), 403–405 (1996). [CrossRef]

OCIS Codes
(160.4760) Materials : Optical properties
(300.1030) Spectroscopy : Absorption
(300.6280) Spectroscopy : Spectroscopy, fluorescence and luminescence
(310.1860) Thin films : Deposition and fabrication
(160.4236) Materials : Nanomaterials

ToC Category:
Materials

History
Original Manuscript: January 10, 2014
Revised Manuscript: March 7, 2014
Manuscript Accepted: March 18, 2014
Published: April 3, 2014

Virtual Issues
Vol. 9, Iss. 6 Virtual Journal for Biomedical Optics

Citation
Qin Yang, Yanli Li, Zhigao Hu, Zhihua Duan, Peipei Liang, Jian Sun, Ning Xu, and Jiada Wu, "Extended photo-response of ZnO/CdS core/shell nanorods fabricated by hydrothermal reaction and pulsed laser deposition," Opt. Express 22, 8617-8623 (2014)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-22-7-8617


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References

  1. J. van Embden, J. Jasieniak, D. E. Gómez, P. Mulvaney, M. Giersig, “Review of the synthetic chemistry involved in the production of core/shell semiconductor nanocrystals,” Aust. J. Chem. 60(7), 457–471 (2007). [CrossRef]
  2. K. Wang, J. J. Chen, W. L. Zhou, Y. Zhang, Y. F. Yan, J. Pern, A. Mascarenhas, “Direct growth of highly mismatched type II ZnO/ZnSe core/shell nanowire arrays on transparent conducting oxide substrates for solar cell applications,” Adv. Mater. 20(17), 3248–3253 (2008). [CrossRef]
  3. Q. Yang, Y. Liu, C. F. Pan, J. Chen, X. N. Wen, Z. L. Wang, “Largely enhanced efficiency in ZnO nanowire/p-polymer hybridized inorganic/organic ultraviolet light-emitting diode by piezo-phototronic effect,” Nano Lett. 13(2), 607–613 (2013). [CrossRef] [PubMed]
  4. S. Mokkapati, D. Saxena, N. Jiang, P. Parkinson, J. Wong-Leung, Q. Gao, H. H. Tan, C. Jagadish, “Polarization tunable, multicolor emission from core-shell photonic III-V semiconductor nanowires,” Nano Lett. 12(12), 6428–6431 (2012). [CrossRef] [PubMed]
  5. S. J. Pearton, D. P. Norton, K. Ip, Y. W. Heo, T. Steiner, “Recent progress in processing and properties of ZnO,” Superlattices Microstruct. 34(1–2), 3–32 (2003). [CrossRef]
  6. M. C. Baykul, N. Orhan, “Band alignment of Cd(1 −x)ZnxS produced by spray pyrolysis method,” Thin Solid Films 518(8), 1925–1928 (2010). [CrossRef]
  7. A. A. Ziabari, F. E. Ghodsi, “Growth, characterization and studying of sol–gel derived CdS nanoscrystalline thin films incorporated in polyethyleneglycol: Effects of post-heat treatment,” Sol. Energy Mater. Sol. Cells 105, 249–262 (2012). [CrossRef]
  8. C. M. Li, T. Ahmed, M. G. Ma, T. Edvinsson, J. F. Zhu, “A facile approach to ZnO/CdS nanoarrays and their photocatalytic and photoelectrochemical properties,” Appl. Catal. B 138, 175−183 (2013).
  9. S. Khanchandani, S. Kundu, A. Patra, A. K. Ganguli, “Shell thickness dependent photocatalytic properties of ZnO/CdS core−shell nanorods,” J. Phys. Chem. C 116(44), 23653–23662 (2012). [CrossRef]
  10. Z. M. Wu, Y. Zhang, J. J. Zheng, X. G. Lin, X. H. Chen, B. W. Huang, H. Q. Wang, K. Huang, S. P. Li, J. Y. Kang, “An all-inorganic type-II heterojunction array with nearly full solar spectral response based on ZnO/ZnSe core/shell nanowires,” J. Mater. Chem. 21(16), 6020–6026 (2011). [CrossRef]
  11. Y. Zhang, M. D. Sturge, K. Kash, A. S. Gozdz, L. T. Florez, J. P. Harbison, “Temperature dependence of luminescence efficiency, exciton transfer, and exciton localization in GaAs/AlxGa1-xAs quantum wires and quantum dots,” Phys. Rev. B Condens. Matter 51(19), 13303–13314 (1995). [CrossRef] [PubMed]
  12. N. Xu, Y. Cui, Z. G. Hu, W. L. Yu, J. Sun, N. Xu, J. D. Wu, “Photoluminescence and low-threshold lasing of ZnO nanorod arrays,” Opt. Express 20(14), 14857–14863 (2012). [CrossRef] [PubMed]
  13. T. C. Damen, S. P. S. Porto, B. Tell, “Raman effect in zinc oxide,” Phys. Rev. 142(2), 570–574 (1966). [CrossRef]
  14. V. Pachauri, C. Subramaniam, T. Pradeep, “Novel ZnO nanostructures over gold and silver nanoparticle assemblies,” Chem. Phys. Lett. 423(1–3), 240–246 (2006). [CrossRef]
  15. R. C. C. Leite, J. F. Scott, T. C. Damen, “Multiple-phonon resonant raman scattering in CdS,” Phys. Rev. Lett. 22(15), 780–782 (1969). [CrossRef]
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