We observe ultraviolet photoluminescence from sputtered ZnO quantum dots which are fabricated with no annealing steps. The nanocrystals are embedded in amorphous SiO₂ and exhibit a narrow size distribution of 3.5 ± 0.6 nm. Photoluminescence and transmittance measurements show a shift of ultraviolet emission and absorption of the dots compared to bulk ZnO material. This work paves the way for cheap nanooptical devices in the ultraviolet which are fabricated in a single sputtering run.

© 2011 Optical Society of America

1. N. Janßen, K. M. Whitaker, D. R. Gamelin, and R. Bratschitsch, “Ultrafast spin dynamics in colloidal ZnO quantum dots,” Nano Lett. 8, 1991–1994 (2008). [CrossRef]
2. S. Kako, C. Santori, K. Hoshino, S. Götzinger, Y. Yamamoto, and Y. Arakawa, “A gallium nitride single-photon source operating at 200 K,” Nat. Mater. 5, 887–892 (2006). [CrossRef]
3. T. Thomay, T. Hanke, M. Tomas, F. Sotier, K. Beha, V. Knittel, M. Kahl, K. M. Whitaker, D. R. Gamelin, A. Leitenstorfer, and R. Bratschitsch, “Colloidal ZnO quantum dots in ultraviolet pillar microcavities,” Opt. Express 16, 9791–9794 (2008). [CrossRef] [PubMed]
4. J. G. Ma, Y. C. Liu, C. S. Xu, Y. X. Liu, C. L. Shao, H. Y. Xu, J. Y. Zhang, Y. M. Lu, D. Z. Shen, and X. W. Fan, “Preparation and characterization of ZnO particles embedded in SiO2 matrix by reactive magnetron sputtering,” J. Appl. Phys. 97, 103509 (2005). [CrossRef]
5. G. Mayer, M. Fonin, U. R¨udiger, R. Schneider, D. Gerthsen, N. Janßen, and R. Bratschitsch, “The structure and optical properties of ZnO nanocrystals embedded in SiO2 fabricated by radio-frequency sputtering,” Nanotechnology 20, 075601 (2009). [CrossRef] [PubMed]
6. V. Pankratov, V. Osinniy, A. Nylandsted Larsen, and B. Bech Nielsen, “ZnO nanocrystals/SiO2 multilayer structures fabricated by rf-magnetron sputtering,” Physica B 404, 4827–4830 (2009). [CrossRef]
7. J. I. Pankove, Optical Processes in Semiconductors (Prentice-Hall Inc., 1971).
8. S. Srinivasan, F. Bertram, A. Bell, F. A. Ponce, S. Tanaka, H. Omiya, and Y. Nakagawa, “Low Stokes shift in thick and homogeneous InGaN epilayers,” Appl. Phys. Lett. 80, 550–552 (2002). [CrossRef]
9. P.-T. Hsieh, Y.-C. Chen, C.-M. Wang, Y.-Z. Tsai, and C.-C. Hu, “Structural and photoluminescence characteristics of ZnO films by room temperature sputtering and rapid thermal annealing process,” Appl. Phys., A Mater. Sci. Process. 84, 345–349 (2006). [CrossRef]
10. Y. G. Wang, S. P. Lau, H. W. Lee, S. F. Yu, B. K. Tay, X. H. Zhang, and H. H. Hng, “Photoluminescence study of ZnO films prepared by thermal oxidation of Zn metallic films in air,” J. Appl. Phys. 94, 354–358 (2003). [CrossRef]
11. J. Zhao, L. Hu, Z. Wang, Y. Zhao, X. Liang, and M. Wang, “High-quality ZnO thin films prepared by low temperature oxidation of metallic Zn,” Appl. Surf. Sci. 229, 311–315 (2004). [CrossRef]
12. Y. Chen, D. M. Bagnall, H.-J. Koh, K.-T. Park, K. Hiraga, Z. Zhu, and T. Yao, “Plasma assisted molecular beam epitaxy of ZnO on c-plane sapphire: growth and characterization,” J. Appl. Phys. 84, 3912–3918 (1998). [CrossRef]
13. V. A. Fonoberov, K. A. Alim, and A. A. Balandin, “Photoluminescence investigation of the carrier recombination processes in ZnO quantum dots and nanocrystals,” Phys. Rev. B 73, 165317 (2006). [CrossRef]
14. K. Vanheusden, W. L. Warren, C. H. Seager, D. R. Tallant, J. A. Voigt, and B. E. Gnade, “Mechanisms behind green photoluminescence in ZnO phosphor powders,” J. Appl. Phys. 79, 7983–7990 (1996). [CrossRef]
15. M. K. Wu, Y. T. Shih, M. J. Chen, J. R. Yang, and M. Shiojiri, “ZnO quantum dots embedded in a SiO2 nanoparticle layer grown by atomic layer deposition,” Phys. Status Solidi 3, 88–90 (2009) (RRL). [CrossRef]
16. J. G. Lu, Z. Z. Ye, Y. Z. Zhang, Q. L. Liang, S. Fujita, and Z. L. Wang, “Self-assembled ZnO quantum dots with tunable optical properties,” Appl. Phys. Lett. 89, 023122 (2006). [CrossRef]
17. L. Mädler, J. W. Stark, and S. E. Pratsinis, “Rapid synthesis of stable ZnO quantum dots,” J. Appl. Phys. 92, 6537–6540 (2002). [CrossRef]
18. K. Suzuki, H. Kondo, M. Inoguchi, N. Tanaka, K. Kageyama, and H. Takagi, “Optical properties of wellcrystallized and size-tuned ZnO quantum dots,” Appl. Phys. Lett. 94, 223103 (2009). [CrossRef]
19. R. T. Senger and K. K. Bajaj, “Optical properties of confined polaronic excitons in spherical ionic quantum dots,” Phys. Rev. B 68, 045313 (2003). [CrossRef]
20. L. E. Brus, “Electron-electron and electron-hole interactions in small semiconductor crystallites: the size dependence of the lowest excited electronic state,” J. Chem. Phys. 80, 4403–4409 (1984). [CrossRef]
21. M. Iwamatsu, M. Fujiwara, N. Happo, and K. Horii, “Effects of dielectric discontinuity on the ground-state energy of charged Si dots covered with a SiO2 layer,” J. Phys. Condens. Matter 9, 9881–9892 (1997). [CrossRef]
22. V. A. Fonoberov and A. A. Balandin, “Origin of ultraviolet photoluminescence in ZnO quantum dots: confined excitons versus surface-bound impurity exciton complexes,” Appl. Phys. Lett. 85, 5971–5973 (2004). [CrossRef]
23. V. A. Fonoberov, and A. A. Balandin, “Radiative lifetime of excitons in ZnO nanocrystals: the dead-layer effect,” Phys. Rev. B 70, 195410 (2004).
24. K. A. Alim, V. A. Fonoberov, and A. A. Balandin, “Origin of the optical phonon frequency shifts in ZnO quantum dots,” Appl. Phys. Lett. 86, 053103 (2005). [CrossRef]
25. Y. Yamada, Wide Bandgap Semiconductors, 1st ed. (Springer, Berlin, 2007).

Appl. Phys. Lett.

• S. Srinivasan, F. Bertram, A. Bell, F. A. Ponce, S. Tanaka, H. Omiya, and Y. Nakagawa, “Low Stokes shift in thick and homogeneous InGaN epilayers,” Appl. Phys. Lett. 80, 550–552 (2002). [CrossRef]
• J. G. Lu, Z. Z. Ye, Y. Z. Zhang, Q. L. Liang, S. Fujita, and Z. L. Wang, “Self-assembled ZnO quantum dots with tunable optical properties,” Appl. Phys. Lett. 89, 023122 (2006). [CrossRef]
• K. Suzuki, H. Kondo, M. Inoguchi, N. Tanaka, K. Kageyama, and H. Takagi, “Optical properties of wellcrystallized and size-tuned ZnO quantum dots,” Appl. Phys. Lett. 94, 223103 (2009). [CrossRef]
• V. A. Fonoberov and A. A. Balandin, “Origin of ultraviolet photoluminescence in ZnO quantum dots: confined excitons versus surface-bound impurity exciton complexes,” Appl. Phys. Lett. 85, 5971–5973 (2004). [CrossRef]
• K. A. Alim, V. A. Fonoberov, and A. A. Balandin, “Origin of the optical phonon frequency shifts in ZnO quantum dots,” Appl. Phys. Lett. 86, 053103 (2005). [CrossRef]

Appl. Phys., A Mater. Sci. Process.

• P.-T. Hsieh, Y.-C. Chen, C.-M. Wang, Y.-Z. Tsai, and C.-C. Hu, “Structural and photoluminescence characteristics of ZnO films by room temperature sputtering and rapid thermal annealing process,” Appl. Phys., A Mater. Sci. Process. 84, 345–349 (2006). [CrossRef]

Appl. Surf. Sci.

• J. Zhao, L. Hu, Z. Wang, Y. Zhao, X. Liang, and M. Wang, “High-quality ZnO thin films prepared by low temperature oxidation of metallic Zn,” Appl. Surf. Sci. 229, 311–315 (2004). [CrossRef]

J. Appl. Phys.

• Y. Chen, D. M. Bagnall, H.-J. Koh, K.-T. Park, K. Hiraga, Z. Zhu, and T. Yao, “Plasma assisted molecular beam epitaxy of ZnO on c-plane sapphire: growth and characterization,” J. Appl. Phys. 84, 3912–3918 (1998). [CrossRef]
• K. Vanheusden, W. L. Warren, C. H. Seager, D. R. Tallant, J. A. Voigt, and B. E. Gnade, “Mechanisms behind green photoluminescence in ZnO phosphor powders,” J. Appl. Phys. 79, 7983–7990 (1996). [CrossRef]
• L. Mädler, J. W. Stark, and S. E. Pratsinis, “Rapid synthesis of stable ZnO quantum dots,” J. Appl. Phys. 92, 6537–6540 (2002). [CrossRef]
• Y. G. Wang, S. P. Lau, H. W. Lee, S. F. Yu, B. K. Tay, X. H. Zhang, and H. H. Hng, “Photoluminescence study of ZnO films prepared by thermal oxidation of Zn metallic films in air,” J. Appl. Phys. 94, 354–358 (2003). [CrossRef]
• J. G. Ma, Y. C. Liu, C. S. Xu, Y. X. Liu, C. L. Shao, H. Y. Xu, J. Y. Zhang, Y. M. Lu, D. Z. Shen, and X. W. Fan, “Preparation and characterization of ZnO particles embedded in SiO2 matrix by reactive magnetron sputtering,” J. Appl. Phys. 97, 103509 (2005). [CrossRef]

J. Chem. Phys.

• L. E. Brus, “Electron-electron and electron-hole interactions in small semiconductor crystallites: the size dependence of the lowest excited electronic state,” J. Chem. Phys. 80, 4403–4409 (1984). [CrossRef]

J. Phys. Condens. Matter

• M. Iwamatsu, M. Fujiwara, N. Happo, and K. Horii, “Effects of dielectric discontinuity on the ground-state energy of charged Si dots covered with a SiO2 layer,” J. Phys. Condens. Matter 9, 9881–9892 (1997). [CrossRef]

Nano Lett.

• N. Janßen, K. M. Whitaker, D. R. Gamelin, and R. Bratschitsch, “Ultrafast spin dynamics in colloidal ZnO quantum dots,” Nano Lett. 8, 1991–1994 (2008). [CrossRef]

Nanotechnology

• G. Mayer, M. Fonin, U. R¨udiger, R. Schneider, D. Gerthsen, N. Janßen, and R. Bratschitsch, “The structure and optical properties of ZnO nanocrystals embedded in SiO2 fabricated by radio-frequency sputtering,” Nanotechnology 20, 075601 (2009). [CrossRef] [PubMed]

Nat. Mater.

• S. Kako, C. Santori, K. Hoshino, S. Götzinger, Y. Yamamoto, and Y. Arakawa, “A gallium nitride single-photon source operating at 200 K,” Nat. Mater. 5, 887–892 (2006). [CrossRef]

Opt. Express

• T. Thomay, T. Hanke, M. Tomas, F. Sotier, K. Beha, V. Knittel, M. Kahl, K. M. Whitaker, D. R. Gamelin, A. Leitenstorfer, and R. Bratschitsch, “Colloidal ZnO quantum dots in ultraviolet pillar microcavities,” Opt. Express 16, 9791–9794 (2008). [CrossRef] [PubMed]

Phys. Rev. B

• R. T. Senger and K. K. Bajaj, “Optical properties of confined polaronic excitons in spherical ionic quantum dots,” Phys. Rev. B 68, 045313 (2003). [CrossRef]
• V. A. Fonoberov, K. A. Alim, and A. A. Balandin, “Photoluminescence investigation of the carrier recombination processes in ZnO quantum dots and nanocrystals,” Phys. Rev. B 73, 165317 (2006). [CrossRef]
• V. A. Fonoberov, and A. A. Balandin, “Radiative lifetime of excitons in ZnO nanocrystals: the dead-layer effect,” Phys. Rev. B 70, 195410 (2004).

Phys. Status Solidi

• M. K. Wu, Y. T. Shih, M. J. Chen, J. R. Yang, and M. Shiojiri, “ZnO quantum dots embedded in a SiO2 nanoparticle layer grown by atomic layer deposition,” Phys. Status Solidi 3, 88–90 (2009) (RRL). [CrossRef]

Physica B

• V. Pankratov, V. Osinniy, A. Nylandsted Larsen, and B. Bech Nielsen, “ZnO nanocrystals/SiO2 multilayer structures fabricated by rf-magnetron sputtering,” Physica B 404, 4827–4830 (2009). [CrossRef]

Other

• J. I. Pankove, Optical Processes in Semiconductors (Prentice-Hall Inc., 1971).
• Y. Yamada, Wide Bandgap Semiconductors, 1st ed. (Springer, Berlin, 2007).

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