Doping semiconductor nanocrystals

Article metrics

Abstract

Doping—the intentional introduction of impurities into a material—is fundamental to controlling the properties of bulk semiconductors. This has stimulated similar efforts to dope semiconductor nanocrystals1,2,3,4. Despite some successes5,6,7,8,9,10,11, many of these efforts have failed, for reasons that remain unclear. For example, Mn can be incorporated into nanocrystals of CdS and ZnSe (refs 7–9), but not into CdSe (ref. 12)—despite comparable bulk solubilities of near 50 per cent. These difficulties, which have hindered development of new nanocrystalline materials13,14,15, are often attributed to ‘self-purification’, an allegedly intrinsic mechanism whereby impurities are expelled. Here we show instead that the underlying mechanism that controls doping is the initial adsorption of impurities on the nanocrystal surface during growth. We find that adsorption—and therefore doping efficiency—is determined by three main factors: surface morphology, nanocrystal shape, and surfactants in the growth solution. Calculated Mn adsorption energies and equilibrium shapes for several nanocrystals lead to specific doping predictions. These are confirmed by measuring how the Mn concentration in ZnSe varies with nanocrystal size and shape. Finally, we use our predictions to incorporate Mn into previously undopable CdSe nanocrystals. This success establishes that earlier difficulties with doping are not intrinsic, and suggests that a variety of doped nanocrystals—for applications from solar cells16 to spintronics17—can be anticipated.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.

from$8.99

All prices are NET prices.

Figure 1: Theoretical binding energies for individual Mn adsorbates on various semiconductor surfaces.
Figure 2: Equilibrium crystal shape for cubic systems, as determined by the ratios of their surface energies.
Figure 3: Photoluminescence data and theoretical doping model for ZnSe nanocrystals doped with Mn.
Figure 4: Mn doping of zinc-blende and wurtzite CdSe nanocrystals.

References

  1. 1

    Ekimov, A. I. & Onushchenko, A. A. Quantum size effect in 3-dimensional microscopic semiconductor crystals. JETP Lett. 34, 345–349 (1981)

  2. 2

    Efros, Al. L. & Efros, A. L. Interband absorption of light in a semiconductor sphere. Sov. Phys. Semicond. 16, 772–775 (1982)

  3. 3

    Brus, L. E. A simple model for the ionization potential, electron affinity, and aqueous redox potentials of small semiconductor crystallites. J. Chem. Phys. 79, 5566–5571 (1983)

  4. 4

    Alivisatos, A. P. Semiconductor clusters, nanocrystals, and quantum dots. Science 271, 933–937 (1996)

  5. 5

    Wang, Y., Herron, N., Moller, K. & Bein, T. 3-dimensionally confined diluted magnetic semiconductor clusters: Zn1–xMnxS. Solid State Commun. 77, 33–38 (1991)

  6. 6

    Bhargava, R. N., Gallagher, D., Hong, X. & Nurmikko, A. Optical properties of manganese-doped nanocrystals of ZnS. Phys. Rev. Lett. 72, 416–419 (1994)

  7. 7

    Levy, L., Hochepied, J. F. & Pileni, M. P. Control of the size and composition of three dimensionally diluted magnetic semiconductor clusters. J. Phys. Chem. 100, 18322–18326 (1996)

  8. 8

    Norris, D. J., Yao, N., Charnock, F. T. & Kennedy, T. A. High-quality manganese-doped ZnSe nanocrystals. Nano Lett. 1, 3–7 (2001)

  9. 9

    Suyver, J. F., Wuister, S. F., Kelly, J. J. & Meijerink, A. Luminescence of nanocrystalline ZnSe:Mn2+. Phys. Chem. Chem. Phys. 2, 5445–5448 (2000)

  10. 10

    Hanif, K. M., Meulenberg, R. W. & Strouse, G. F. Magnetic ordering in doped Cd1–xCoxSe diluted magnetic quantum dots. J. Am. Chem. Soc. 124, 11495–11502 (2002)

  11. 11

    Stowell, C. A., Wiacek, R. J., Saunders, A. E. & Korgel, B. A. Synthesis and characterization of dilute magnetic semiconductor manganese-doped indium arsenide nanocrystals. Nano Lett. 3, 1441–1447 (2003)

  12. 12

    Mikulec, F. V. et al. Organometallic synthesis and spectroscopic characterization of manganese-doped CdSe nanocrystals. J. Am. Chem. Soc. 122, 2532–2540 (2000)

  13. 13

    Shim, M. & Guyot-Sionnest, P. n-type colloidal semiconductor nanocrystals. Nature 407, 981–983 (2000)

  14. 14

    Hoffman, D. M. et al. Giant internal magnetic fields in Mn doped nanocrystal quantum dots. Solid State Commun. 114, 547–550 (2000)

  15. 15

    Efros, Al. L., Rashba, E. I. & Rosen, M. Paramagnetic ion-doped nanocrystal as a voltage-controlled spin filter. Phys. Rev. Lett. 87, 206601 (2001)

  16. 16

    Huynh, W. U., Dittmer, J. J. & Alivisatos, A. P. Hybrid nanorod-polymer solar cells. Science 295, 2425–2427 (2002)

  17. 17

    Wolf, S. A. et al. Spintronics: a spin-based electronics vision for the future. Science 294, 1488–1495 (2001)

  18. 18

    Hwang, I. S., Kim, H. D., Kim, J. E., Park, H. Y. & Lim, H. Solid solubilities of magnetic ions in diluted magnetic semiconductors grown under equilibrium conditions. Phys. Rev. B 50, 8849–8852 (1994)

  19. 19

    Jamil, N. Y. & Shaw, D. The diffusion of Mn in CdTe. Semicond. Sci. Technol. 10, 952–958 (1995)

  20. 20

    Shiang, J. J., Kadavanich, A. V., Grubbs, R. K. & Alivisatos, A. P. Symmetry of annealed wurtzite CdSe nanocrystals — assignment to the C3v point group. J. Phys. Chem. 99, 17417–17422 (1995)

  21. 21

    Peng, X. G., Wickham, J. & Alivisatos, A. P. Kinetics of II–VI and III–V colloidal semiconductor nanocrystal growth: ‘Focusing’ of size distributions. J. Am. Chem. Soc. 120, 5343–5344 (1998)

  22. 22

    Kresse, G. & Furthmuller, J. Efficient iterative schemes for ab initio total-energy calculations using a plane-wave basis set. Phys. Rev. B 54, 11169–11186 (1996)

  23. 23

    Perdew, J. P., Burke, K. & Ernzerhof, M. Generalized gradient approximation made simple. Phys. Rev. Lett. 77, 3865–3868 (1996)

  24. 24

    Ji, T. H., Jian, W. B. & Fang, J. Y. The first synthesis of Pb1–xMnxSe nanocrystals. J. Am. Chem. Soc. 125, 8448–8449 (2003)

  25. 25

    Wortis, M. Chemistry and Physics of Solid Surfaces VII Ch. 13 (Springer, Berlin, 1988)

  26. 26

    Kasuya, A. et al. Ultra-stable nanoparticles of CdSe revealed from mass spectrometry. Nature Mater. 3, 99–102 (2004)

  27. 27

    Kaxiras, E. Effect of surface reconstruction on stability and reactivity of Si clusters. Phys. Rev. Lett. 64, 551–554 (1990)

  28. 28

    Balet, L. P., Ivanov, S. A., Piryatinski, A., Achermann, M. & Klimov, V. I. Inverted core/shell nanocrystals continuously tunable between type-I and type-II localization regimes. Nano Lett. 4, 1485–1488 (2004)

  29. 29

    Koh, A. K. & Miller, D. J. The systematic variation of the EPR parameters of manganese in II–VI semiconductors. Solid State Commun. 60, 217–222 (1986)

  30. 30

    Peng, X. G. et al. Shape control of CdSe nanocrystals. Nature 404, 59–61 (2000)

Download references

Acknowledgements

This work was supported by the US Office of Naval Research, the NSF-MRSEC at the University of Minnesota, and NSF-CTS. Computations were performed at the Department of Defense Major Shared Resource Center at ASC. We thank Y. Nesmelov, P. Hasjim and R. Weber for experimental assistance.

Author information

Correspondence to Steven C. Erwin or David J. Norris.

Ethics declarations

Competing interests

Reprints and permissions information is available at npg.nature.com/reprintsandpermissions. The authors declare no competing financial interests.

Supplementary information

Supplementary Discussion

This document lists and discusses the specific surface reconstructions used in the calculations of semiconductor surface energies and of binding energies for Mn adsorbates. (PDF 18 kb)

Supplementary Methods

This document provides a detailed derivation of the optical model used for describing measured photoluminescence intensity ratios. (PDF 48 kb)

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Erwin, S., Zu, L., Haftel, M. et al. Doping semiconductor nanocrystals. Nature 436, 91–94 (2005) doi:10.1038/nature03832

Download citation

Further reading

Comments

By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.