Abstract

We examine fundamental issues related to discriminating structural and optical features in near-field scanning apertureless microscopy. We report a series of controlled experiments with nanosphere-sized standard spheres in which we observed significant differences in resolution and structure between an atomic-force microscope image and a simultaneously acquired near-field optical (NFO) image. Further, in experiments that employed a mix of dyed and undyed nanospheres we found that we can observe differences in the same NFO image for adjacent nanospheres. Therefore we conclude that near-field scanning apertureless microscopy not only meets the criteria for a NFO image but also is capable of measuring optical properties below the diffraction limit. The two-point resolution was at least 200 nm when we were detecting optical phase and 50 nm when we were detecting optical intensity. The edge response was typically 15 nm, and the minimum observable features were of the order of 3 nm.

© 1999 Optical Society of America

Full Article  |  PDF Article

References

  • View by:
  • |
  • |
  • |

  1. D. Courjon and C. Bainier, Rep. Prog. Phys. 57, 989 (1994).
    [CrossRef]
  2. H. K. Wickramasinghe and C. C. Williams, “Apertureless near field optical microscope,” U.S. patent4,947,034 (April28, 1989).
  3. F. Zenhausern, M. P. O’Boyle, and H. K. Wickramasinghe, Appl. Phys. Lett. 65, 1623 (1994).
    [CrossRef]
  4. B. Hecht, H. Bielefeldt, Y. Inouye, L. Novotny, and D. W. Pohl, J. Appl. Phys. 81, 2492 (1997).
    [CrossRef]
  5. V. B. Ellings and G. A. Gurley, “Tapping atomic force microscope,” U.S. patent5,412,980 (May9, 1995).
  6. When the tip oscillation amplitude is kept constant, the average tip–sample distance is constant over the lock-in integration time. Therefore there is less risk of introducing artifacts that could be due to measurement of the cantilever position with light reflection from it. In previous experiments, however, the entire cantilever position was modulated relative to the sample, so there is a risk that the images are a measurement of only the tip position.
  7. C. Schönenberger and S. F. Alvarado, Rev. Sci. Instrum. 60, 3131 (1989).
    [CrossRef]
  8. F. Zenhausern, Y. Martin, and H. K. Wickramasinghe, Science 269, 1083 (1995).
    [CrossRef] [PubMed]
  9. N. Garcia and M. Nieto-Vesperinas, Appl. Phys. Lett. 66, 3399 (1995).
    [CrossRef]
  10. J. D. Jackson, Classical Electrodynamics, 2nd ed. (Wiley, New York, 1975).
  11. Since the FWHM of a step is a commonly used resolution criterion, 15 nm is closer to the resolution predicted by Garcia and Nieto-Vesperinas9 than that predicted by Zenhausern et al.8
  12. Polysciences Fluoresbrite nanospheres were used. The fluorescein-based dye is limited to the outer 10% of the nanosphere radius and has a fluorescence that peaks at 540 nm and extends to 700 nm.

1997 (1)

B. Hecht, H. Bielefeldt, Y. Inouye, L. Novotny, and D. W. Pohl, J. Appl. Phys. 81, 2492 (1997).
[CrossRef]

1995 (2)

F. Zenhausern, Y. Martin, and H. K. Wickramasinghe, Science 269, 1083 (1995).
[CrossRef] [PubMed]

N. Garcia and M. Nieto-Vesperinas, Appl. Phys. Lett. 66, 3399 (1995).
[CrossRef]

1994 (2)

D. Courjon and C. Bainier, Rep. Prog. Phys. 57, 989 (1994).
[CrossRef]

F. Zenhausern, M. P. O’Boyle, and H. K. Wickramasinghe, Appl. Phys. Lett. 65, 1623 (1994).
[CrossRef]

1989 (1)

C. Schönenberger and S. F. Alvarado, Rev. Sci. Instrum. 60, 3131 (1989).
[CrossRef]

Alvarado, S. F.

C. Schönenberger and S. F. Alvarado, Rev. Sci. Instrum. 60, 3131 (1989).
[CrossRef]

Bainier, C.

D. Courjon and C. Bainier, Rep. Prog. Phys. 57, 989 (1994).
[CrossRef]

Bielefeldt, H.

B. Hecht, H. Bielefeldt, Y. Inouye, L. Novotny, and D. W. Pohl, J. Appl. Phys. 81, 2492 (1997).
[CrossRef]

Courjon, D.

D. Courjon and C. Bainier, Rep. Prog. Phys. 57, 989 (1994).
[CrossRef]

Ellings, V. B.

V. B. Ellings and G. A. Gurley, “Tapping atomic force microscope,” U.S. patent5,412,980 (May9, 1995).

Garcia, N.

N. Garcia and M. Nieto-Vesperinas, Appl. Phys. Lett. 66, 3399 (1995).
[CrossRef]

Gurley, G. A.

V. B. Ellings and G. A. Gurley, “Tapping atomic force microscope,” U.S. patent5,412,980 (May9, 1995).

Hecht, B.

B. Hecht, H. Bielefeldt, Y. Inouye, L. Novotny, and D. W. Pohl, J. Appl. Phys. 81, 2492 (1997).
[CrossRef]

Inouye, Y.

B. Hecht, H. Bielefeldt, Y. Inouye, L. Novotny, and D. W. Pohl, J. Appl. Phys. 81, 2492 (1997).
[CrossRef]

Jackson, J. D.

J. D. Jackson, Classical Electrodynamics, 2nd ed. (Wiley, New York, 1975).

Martin, Y.

F. Zenhausern, Y. Martin, and H. K. Wickramasinghe, Science 269, 1083 (1995).
[CrossRef] [PubMed]

Nieto-Vesperinas, M.

N. Garcia and M. Nieto-Vesperinas, Appl. Phys. Lett. 66, 3399 (1995).
[CrossRef]

Novotny, L.

B. Hecht, H. Bielefeldt, Y. Inouye, L. Novotny, and D. W. Pohl, J. Appl. Phys. 81, 2492 (1997).
[CrossRef]

O’Boyle, M. P.

F. Zenhausern, M. P. O’Boyle, and H. K. Wickramasinghe, Appl. Phys. Lett. 65, 1623 (1994).
[CrossRef]

Pohl, D. W.

B. Hecht, H. Bielefeldt, Y. Inouye, L. Novotny, and D. W. Pohl, J. Appl. Phys. 81, 2492 (1997).
[CrossRef]

Schönenberger, C.

C. Schönenberger and S. F. Alvarado, Rev. Sci. Instrum. 60, 3131 (1989).
[CrossRef]

Wickramasinghe, H. K.

F. Zenhausern, Y. Martin, and H. K. Wickramasinghe, Science 269, 1083 (1995).
[CrossRef] [PubMed]

F. Zenhausern, M. P. O’Boyle, and H. K. Wickramasinghe, Appl. Phys. Lett. 65, 1623 (1994).
[CrossRef]

H. K. Wickramasinghe and C. C. Williams, “Apertureless near field optical microscope,” U.S. patent4,947,034 (April28, 1989).

Williams, C. C.

H. K. Wickramasinghe and C. C. Williams, “Apertureless near field optical microscope,” U.S. patent4,947,034 (April28, 1989).

Zenhausern, F.

F. Zenhausern, Y. Martin, and H. K. Wickramasinghe, Science 269, 1083 (1995).
[CrossRef] [PubMed]

F. Zenhausern, M. P. O’Boyle, and H. K. Wickramasinghe, Appl. Phys. Lett. 65, 1623 (1994).
[CrossRef]

Appl. Phys. Lett. (2)

F. Zenhausern, M. P. O’Boyle, and H. K. Wickramasinghe, Appl. Phys. Lett. 65, 1623 (1994).
[CrossRef]

N. Garcia and M. Nieto-Vesperinas, Appl. Phys. Lett. 66, 3399 (1995).
[CrossRef]

J. Appl. Phys. (1)

B. Hecht, H. Bielefeldt, Y. Inouye, L. Novotny, and D. W. Pohl, J. Appl. Phys. 81, 2492 (1997).
[CrossRef]

Rep. Prog. Phys. (1)

D. Courjon and C. Bainier, Rep. Prog. Phys. 57, 989 (1994).
[CrossRef]

Rev. Sci. Instrum. (1)

C. Schönenberger and S. F. Alvarado, Rev. Sci. Instrum. 60, 3131 (1989).
[CrossRef]

Science (1)

F. Zenhausern, Y. Martin, and H. K. Wickramasinghe, Science 269, 1083 (1995).
[CrossRef] [PubMed]

Other (6)

H. K. Wickramasinghe and C. C. Williams, “Apertureless near field optical microscope,” U.S. patent4,947,034 (April28, 1989).

V. B. Ellings and G. A. Gurley, “Tapping atomic force microscope,” U.S. patent5,412,980 (May9, 1995).

When the tip oscillation amplitude is kept constant, the average tip–sample distance is constant over the lock-in integration time. Therefore there is less risk of introducing artifacts that could be due to measurement of the cantilever position with light reflection from it. In previous experiments, however, the entire cantilever position was modulated relative to the sample, so there is a risk that the images are a measurement of only the tip position.

J. D. Jackson, Classical Electrodynamics, 2nd ed. (Wiley, New York, 1975).

Since the FWHM of a step is a commonly used resolution criterion, 15 nm is closer to the resolution predicted by Garcia and Nieto-Vesperinas9 than that predicted by Zenhausern et al.8

Polysciences Fluoresbrite nanospheres were used. The fluorescein-based dye is limited to the outer 10% of the nanosphere radius and has a fluorescence that peaks at 540 nm and extends to 700 nm.

Cited By

OSA participates in CrossRef's Cited-By Linking service. Citing articles from OSA journals and other participating publishers are listed here.

Alert me when this article is cited.


Figures (5)

Fig. 1
Fig. 1

Schematic of the apparatus: Light from a He–Ne laser is split into a reference beam and a sample beam at a beam splitter, S1. The sample beam continues to beam splitter S2, where part of it is dumped and part of it is focused onto the AFM tip by a microscope objective (N.A., 0.75). Since the depth of field of the microscope objective is only 1 µm, compared with a tip height of 15 µm, only the apex of the tip is imaged. Light scattered from the AFM tip is collected by the same objective and combined with the reference beam (reflected from mirror M1) at beam splitter S3. A laser line filter, LF, then rejects all light except the laser light. A spatial filter, SF, passes only light from the AFM tip while excluding light that may be reflected from the cantilever. The light is then split by a Wollaston prism, WP, and is incident upon differential photodiodes, A and B.

Fig. 2
Fig. 2

Raw NFO image of a region between two adjacent 200-nm polystyrene nanospheres with A, a 3-nm minimum observable feature size and B, a 15-nm step response.

Fig. 3
Fig. 3

A, raw NFO image demonstrating 50-nm resolution. The sample is two identical nanospheres imaged by detection of scattered intensity. B, simulated image obtained by use of the coupled-dipole model. The simulation used a tip radius of 20 nm and was computed from the AFM data collected for image A.

Fig. 4
Fig. 4

Clusters of 50-nm nanospheres. Left, simultaneously acquired AFM data; right, raw NFO image from the microscope, demonstrating approximately 200-nm resolution for detection of optical phase.

Fig. 5
Fig. 5

50-nm-scale optical property discrimination. False-color images of dyed and undyed 50-nm nanospheres are shown. The left image is from AFM data, and the right image is from the raw NFO data: i, 50-nm spheres resolved by the microscope show up as “low” next to ii, 50-nm spheres that appear “high.”

Equations (1)

Equations on this page are rendered with MathJax. Learn more.

It=c0k44π02d2pt2sin2ϕ,

Metrics