Abstract

Soft x-ray Zernike phase contrast microscopy was implemented using a “Zernike zone plate” (ZZP) without the use of a separate phase filter in the back focal plane. The ZZP is a single optic that integrates the appropriate ±π/2 radians phase shift through selective zone placement shifts in a Fresnel zone plate. Imaging using a regular zone plate, positive ZZP, and negative ZZP was performed at a wavelength of λ=2.163 nm. Contrast enhancement with the positive ZZP and contrast reversal with the negative ZZP were observed.

© 2008 Optical Society of America

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References

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  1. D. Attwood, Soft x-rays and extreme ultraviolet radiation: principles and applications, (Cambridge University Press, 1999).
  2. P.A.C. Jansson, U. Vogt, and H.M. Hertz, "Liquid nitrogen jet laser plasma source for compact soft x-ray microscopy," Rev. Sci. Instrum. 76, 043503 (2005).
    [CrossRef]
  3. Energetiq Technology, Inc., "EQ-10M Soft X-ray & EUV Source," http://www.energetiq.com/DataSheets/DS004_EQ-10M_Data_Sheet_SXR.pdf.
  4. G. Schmahl, D. Rudolph, P. Guttmann, G. Schneider, J. Thieme, and B. Niemann, "Phase contrast studies of biological specimens with the x-ray microscope at BESSY," Rev. Sci. Instrum. 66, 1282-1286 (1995).
    [CrossRef]
  5. G. Schmahl, D. Rudolph, G. Schneider, P. Guttmann, and B. Niemann, "Phase contrast X-ray microscopy studies," Optik 97, 181-182 (1994).
  6. M. Awaji, Y. Suzuki, A. Takeuchi, H. Takano, N. Kamijo, S. Tamura, and M. Yasumoto, "Zernike-type X-ray imaging microscopy at 25 keV with Fresnel zone plate optics," J. Synchrotron Rad. 9, 125-127 (2002).
    [CrossRef]
  7. H. Yokosuka, N. Watanabe, T. Ohigashi, Y. Yoshida, S. Maeda, S. Aoki, Y. Suzuki, A. Takeuchi and H. Takano, "Zernike-type phase-contrast hard X-ray microscope with a zone plate at the Photon Factory," J. Synchrotron Rad. 9, 179-181 (2002).
    [CrossRef]
  8. U. Neuhäusler, G. Schneider, W. Ludwig, M.A. Meyer, E. Zschech, and D. Hambach, "X-ray microscopy in Zernike phase contrast mode at 4 keV photon energy with 60 nm resolution," J. Phys. D: Appl. Phys. 36, A79-A82 (2003).
    [CrossRef]
  9. Y. Kohmura, A. Takeuchi, H. Takano, Y. Suzuki, and T. Ishikawa, "Zernike phase-contrast X-ray microscope with an X-ray reflractive lens," J. Phys. IV France 104, 603-606 (2003).
    [CrossRef]
  10. H.S. Youn and S-W. Jung, "Hard X-ray microscopy with Zernike phase contrast," J. Microsc. 223, 53-56 (2006).
    [CrossRef] [PubMed]
  11. E. Di Fabrizio, D. Cojoc, S. Cabrini, B. Kaulich, J. Susini, P. Facci, T. Wilhein, "Diffractive optical elements for differential interference contrast x-ray microscopy," Opt. Express 11, 2278-2288 (2003).
    [CrossRef] [PubMed]
  12. U. Vogt, M. Lindblom, P.A.C. Jansson, T.T. Tuohimaa, A. Holmberg, H.M. Hertz, M. Wieland, and T. Wilhein, "Single-optical-element soft x-ray interferometry with a laser-plasma x-ray source," Opt. Lett. 30, 2167-2169, (2005).
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  13. C. Chang, A. Sakdinawat, P. Fischer, E. Anderson, and D. Attwood, "Single-element objective lens for soft x-ray differential interference contrast microscopy," Opt. Lett. 31, 1564-1566 (2006).
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  14. A. Sakdinawat and Y. Liu, "Soft x-ray microscopy using spiral zone plates," Opt. Lett. 32, 2635-2637 (2007).
    [CrossRef] [PubMed]
  15. F. Zernike, "Phase contrast, a new method for the microscopic observation of transparent objects," Physica 9, 686-698 and 975-986, (1942).
    [CrossRef]

2007 (1)

2006 (2)

2005 (2)

2003 (3)

E. Di Fabrizio, D. Cojoc, S. Cabrini, B. Kaulich, J. Susini, P. Facci, T. Wilhein, "Diffractive optical elements for differential interference contrast x-ray microscopy," Opt. Express 11, 2278-2288 (2003).
[CrossRef] [PubMed]

U. Neuhäusler, G. Schneider, W. Ludwig, M.A. Meyer, E. Zschech, and D. Hambach, "X-ray microscopy in Zernike phase contrast mode at 4 keV photon energy with 60 nm resolution," J. Phys. D: Appl. Phys. 36, A79-A82 (2003).
[CrossRef]

Y. Kohmura, A. Takeuchi, H. Takano, Y. Suzuki, and T. Ishikawa, "Zernike phase-contrast X-ray microscope with an X-ray reflractive lens," J. Phys. IV France 104, 603-606 (2003).
[CrossRef]

2002 (2)

M. Awaji, Y. Suzuki, A. Takeuchi, H. Takano, N. Kamijo, S. Tamura, and M. Yasumoto, "Zernike-type X-ray imaging microscopy at 25 keV with Fresnel zone plate optics," J. Synchrotron Rad. 9, 125-127 (2002).
[CrossRef]

H. Yokosuka, N. Watanabe, T. Ohigashi, Y. Yoshida, S. Maeda, S. Aoki, Y. Suzuki, A. Takeuchi and H. Takano, "Zernike-type phase-contrast hard X-ray microscope with a zone plate at the Photon Factory," J. Synchrotron Rad. 9, 179-181 (2002).
[CrossRef]

1995 (1)

G. Schmahl, D. Rudolph, P. Guttmann, G. Schneider, J. Thieme, and B. Niemann, "Phase contrast studies of biological specimens with the x-ray microscope at BESSY," Rev. Sci. Instrum. 66, 1282-1286 (1995).
[CrossRef]

1994 (1)

G. Schmahl, D. Rudolph, G. Schneider, P. Guttmann, and B. Niemann, "Phase contrast X-ray microscopy studies," Optik 97, 181-182 (1994).

1942 (1)

F. Zernike, "Phase contrast, a new method for the microscopic observation of transparent objects," Physica 9, 686-698 and 975-986, (1942).
[CrossRef]

J. Microsc. (1)

H.S. Youn and S-W. Jung, "Hard X-ray microscopy with Zernike phase contrast," J. Microsc. 223, 53-56 (2006).
[CrossRef] [PubMed]

J. Phys. D: Appl. Phys. (1)

U. Neuhäusler, G. Schneider, W. Ludwig, M.A. Meyer, E. Zschech, and D. Hambach, "X-ray microscopy in Zernike phase contrast mode at 4 keV photon energy with 60 nm resolution," J. Phys. D: Appl. Phys. 36, A79-A82 (2003).
[CrossRef]

J. Phys. IV France (1)

Y. Kohmura, A. Takeuchi, H. Takano, Y. Suzuki, and T. Ishikawa, "Zernike phase-contrast X-ray microscope with an X-ray reflractive lens," J. Phys. IV France 104, 603-606 (2003).
[CrossRef]

J. Synchrotron Rad. (2)

M. Awaji, Y. Suzuki, A. Takeuchi, H. Takano, N. Kamijo, S. Tamura, and M. Yasumoto, "Zernike-type X-ray imaging microscopy at 25 keV with Fresnel zone plate optics," J. Synchrotron Rad. 9, 125-127 (2002).
[CrossRef]

H. Yokosuka, N. Watanabe, T. Ohigashi, Y. Yoshida, S. Maeda, S. Aoki, Y. Suzuki, A. Takeuchi and H. Takano, "Zernike-type phase-contrast hard X-ray microscope with a zone plate at the Photon Factory," J. Synchrotron Rad. 9, 179-181 (2002).
[CrossRef]

Opt. Express (1)

Opt. Lett. (3)

Optik (1)

G. Schmahl, D. Rudolph, G. Schneider, P. Guttmann, and B. Niemann, "Phase contrast X-ray microscopy studies," Optik 97, 181-182 (1994).

Physica (1)

F. Zernike, "Phase contrast, a new method for the microscopic observation of transparent objects," Physica 9, 686-698 and 975-986, (1942).
[CrossRef]

Rev. Sci. Instrum. (2)

P.A.C. Jansson, U. Vogt, and H.M. Hertz, "Liquid nitrogen jet laser plasma source for compact soft x-ray microscopy," Rev. Sci. Instrum. 76, 043503 (2005).
[CrossRef]

G. Schmahl, D. Rudolph, P. Guttmann, G. Schneider, J. Thieme, and B. Niemann, "Phase contrast studies of biological specimens with the x-ray microscope at BESSY," Rev. Sci. Instrum. 66, 1282-1286 (1995).
[CrossRef]

Other (2)

D. Attwood, Soft x-rays and extreme ultraviolet radiation: principles and applications, (Cambridge University Press, 1999).

Energetiq Technology, Inc., "EQ-10M Soft X-ray & EUV Source," http://www.energetiq.com/DataSheets/DS004_EQ-10M_Data_Sheet_SXR.pdf.

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Figures (5)

Fig. 1.
Fig. 1.

(a) Schematic of a typical x-ray microscope with well-collimated hollow cone illumination. The 0th order contribution to the image is the light shaded in gray after the objective zone plate. This is the light that is filtered (typically with a phase ring) to provide the phase contrast. Other 0th order light from the sample that is not focused by the objective zone plate passes straight through, but does not contribute to the image since the image area at the CCD does not overlap that of the 0th order. The lack of large spatial divergence of the 0th order allows the phase filter to be moved from the back focal plane to the plane of the objective zone plate as shown by the arrow. This allows the combination of the phase filter and objective into a single optical element. (b) Schematic for the case of a microscope with on-axis illumination.

Fig. 2.
Fig. 2.

Modification of a regular zone plate to a Zernike zone plate involves multiplying by a phase filter with shape and area corresponding to the undiffracted illumination used in the imaging system. The case of on-axis illumination is depicted for the positive Zernike phase contrast case (a) and for the negative Zernike phase contrast case (b). It can be seen that only the portion of the zone plate modified by the phase filter (in this case, the central area) is changed.

Fig. 3.
Fig. 3.

Schematic of the experimental setup for the soft x-ray Zernike phase contrast microscope. A SEM image of a 45 nm thick Cr grating sample underneath a 900 nm Au pinhole is shown. The regular zone plate and Zernike zone plates were used to image the sample with a magnification of 525 times.

Fig. 4.
Fig. 4.

(a) SEM images of the fabricated regular zone plate (RZP), positive Zernike zone plate (PZZP), and negative Zernike zone plate (NZZP). Each zone plate was fabricated using electron beam lithography with an outermost zone width of 72 nm, 300 zones, and 250 nm thick Ni; (b) Corresponding images obtained with the RZP, PZZP, and NZZP at a wavelength of λ=2.163 nm using the setup and sample described in Fig. 3. Contrast enhancement is seen in the image taken with the PZZP, and contrast reversal is seen in the image taken with the NZZP.

Fig. 5.
Fig. 5.

Normalized line profiles taken horizontally through the center of the regular zone plate (RZP), positive Zernike zone plate (PZZP), and negative Zernike zone plate (NZZP) images in Fig. 4b. The PZZP line profile shows enhanced contrast, and the NZZP line profile shows contrast reversal.

Equations (3)

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ZZP ( r ) = RZP ( r ) H ZZP ( r in , r out )
RZP ( r ) = exp ( i πr 2 λf )
H ZZP ( r in , r out ) = { exp ( ± 2 ) if r r out and r r in 1 for all other r

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