Abstract

Metal/MgO multilayers (metal of Fe, Ni80Nb20, and Ti) with bilayer periods in the range 1.2–3.0 nm have been prepared by pulsed laser deposition and characterized by both hard and soft-x-ray reflectometry. The interface roughness is found to be ≤0.5 nm in all the samples and is nearly independent of the total number of deposited bilayers. The interface roughness, however, depends on the absolute thickness of the individual layers and increases from ≈0.3 nm for a 3.0-nm period to ≈0.5 nm for a bilayer period of 1.2 nm. The multilayers are found to be highly stable up to temperatures as high as 550 °C. The hard-x-ray reflectivity of the multilayers decreases for T > 300 °C, whereas the layered structure is stable up to 550 °C. The reflectivity in the water window region of soft x rays, λ = 3.374 nm, was found to be 0.4% at an angle of incidence of ≈54° for multilayers with 60 bilayers at a period of ≈2.1 nm.

© 2004 Optical Society of America

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References

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    [CrossRef]
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    [CrossRef]
  3. G. A. Johansson, M. Berglund, F. Eriksson, J. Birch, H. M. Hertz, “Compact soft x-ray reflectometer based on a line-emitting laser plasma source,” Rev. Sci. Instrum. 72, 58–62 (2001).
    [CrossRef]
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    [CrossRef]
  5. H.-C. Mertins, F. Schäfers, H. Grimmer, D. Clemens, P. Böni, M. Horisberger, “W/C, W/Ti, Ni/Ti, and Ni/V multilayers for the soft-x-ray range: experimental investigation with synchrotron radiation,” Appl. Opt. 37, 1873–1882 (1998).
    [CrossRef]
  6. F. Schäfers, H.-C. Mertins, F. Schmolla, I. Packe, N. N. Salashchenko, E. A. Shamov, “Cr/Sc multilayers for the soft-x-ray range,” Appl. Opt. 37, 719–728 (1998).
    [CrossRef]
  7. S. Vitta, P. Yang, “Thermal stability of 2.4 nm period Ni-Nb/C multilayer x-ray mirror,” Appl. Phys. Lett. 77, 3654–3656 (2000).
    [CrossRef]

2001 (2)

K. Sturm, H.-U. Krebs, “Quantification of resputtering during pulsed laser deposition,” J. Appl. Phys. 90, 1061–1063 (2001).
[CrossRef]

G. A. Johansson, M. Berglund, F. Eriksson, J. Birch, H. M. Hertz, “Compact soft x-ray reflectometer based on a line-emitting laser plasma source,” Rev. Sci. Instrum. 72, 58–62 (2001).
[CrossRef]

2000 (1)

S. Vitta, P. Yang, “Thermal stability of 2.4 nm period Ni-Nb/C multilayer x-ray mirror,” Appl. Phys. Lett. 77, 3654–3656 (2000).
[CrossRef]

1998 (3)

1988 (1)

A. G. Michette, “X-ray microscopy,” Rep. Prog. Phys. 51, 1525–1606 (1988).
[CrossRef]

Berglund, M.

G. A. Johansson, M. Berglund, F. Eriksson, J. Birch, H. M. Hertz, “Compact soft x-ray reflectometer based on a line-emitting laser plasma source,” Rev. Sci. Instrum. 72, 58–62 (2001).
[CrossRef]

Birch, J.

G. A. Johansson, M. Berglund, F. Eriksson, J. Birch, H. M. Hertz, “Compact soft x-ray reflectometer based on a line-emitting laser plasma source,” Rev. Sci. Instrum. 72, 58–62 (2001).
[CrossRef]

Böni, P.

Clemens, D.

Eriksson, F.

G. A. Johansson, M. Berglund, F. Eriksson, J. Birch, H. M. Hertz, “Compact soft x-ray reflectometer based on a line-emitting laser plasma source,” Rev. Sci. Instrum. 72, 58–62 (2001).
[CrossRef]

Grimmer, H.

Hertz, H. M.

G. A. Johansson, M. Berglund, F. Eriksson, J. Birch, H. M. Hertz, “Compact soft x-ray reflectometer based on a line-emitting laser plasma source,” Rev. Sci. Instrum. 72, 58–62 (2001).
[CrossRef]

Horisberger, M.

Johansson, G. A.

G. A. Johansson, M. Berglund, F. Eriksson, J. Birch, H. M. Hertz, “Compact soft x-ray reflectometer based on a line-emitting laser plasma source,” Rev. Sci. Instrum. 72, 58–62 (2001).
[CrossRef]

Krebs, H.-U.

K. Sturm, H.-U. Krebs, “Quantification of resputtering during pulsed laser deposition,” J. Appl. Phys. 90, 1061–1063 (2001).
[CrossRef]

Mertins, H.-C.

Michette, A. G.

A. G. Michette, “X-ray microscopy,” Rep. Prog. Phys. 51, 1525–1606 (1988).
[CrossRef]

Packe, I.

Salashchenko, N. N.

Schäfers, F.

Schmolla, F.

Shamov, E. A.

Sturm, K.

K. Sturm, H.-U. Krebs, “Quantification of resputtering during pulsed laser deposition,” J. Appl. Phys. 90, 1061–1063 (2001).
[CrossRef]

Vitta, S.

S. Vitta, P. Yang, “Thermal stability of 2.4 nm period Ni-Nb/C multilayer x-ray mirror,” Appl. Phys. Lett. 77, 3654–3656 (2000).
[CrossRef]

Windt, D. L.

D. L. Windt, “IMD—software for modeling the optical properties of multilayer films,” Comput. Phys. 12, 360–370 (1998).
[CrossRef]

Yang, P.

S. Vitta, P. Yang, “Thermal stability of 2.4 nm period Ni-Nb/C multilayer x-ray mirror,” Appl. Phys. Lett. 77, 3654–3656 (2000).
[CrossRef]

Appl. Opt. (2)

Appl. Phys. Lett. (1)

S. Vitta, P. Yang, “Thermal stability of 2.4 nm period Ni-Nb/C multilayer x-ray mirror,” Appl. Phys. Lett. 77, 3654–3656 (2000).
[CrossRef]

Comput. Phys. (1)

D. L. Windt, “IMD—software for modeling the optical properties of multilayer films,” Comput. Phys. 12, 360–370 (1998).
[CrossRef]

J. Appl. Phys. (1)

K. Sturm, H.-U. Krebs, “Quantification of resputtering during pulsed laser deposition,” J. Appl. Phys. 90, 1061–1063 (2001).
[CrossRef]

Rep. Prog. Phys. (1)

A. G. Michette, “X-ray microscopy,” Rep. Prog. Phys. 51, 1525–1606 (1988).
[CrossRef]

Rev. Sci. Instrum. (1)

G. A. Johansson, M. Berglund, F. Eriksson, J. Birch, H. M. Hertz, “Compact soft x-ray reflectometer based on a line-emitting laser plasma source,” Rev. Sci. Instrum. 72, 58–62 (2001).
[CrossRef]

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Figures (9)

Fig. 1
Fig. 1

Hard-x-ray reflectivity of Ni80Nb20/MgO multilayers as a function of the bilayer period varied in the range from of 2.36 to 1.19 nm, [(a)–(e)] showing clear total thickness oscillations and the layer period Bragg peak (solid curves). The number of bilayers is kept constant at 40. A simulation of the reflectivity (dashed curves) gives the interface roughness variation with the period. The curves are shifted vertically for clarity.

Fig. 2
Fig. 2

Hard-x-ray reflectivity of Fe/MgO multilayers as a function of varying number: (a) 20, (b) 55, and (c) 65. Periods between 2.1 and 2.2 nm show clear peaks and hence a complete layer ordering. The results of our simulations (dashed curves) are also shown. The curves are shifted vertically for clarity.

Fig. 3
Fig. 3

Measured (solid curves) and simulated (dashed curves) hard-x-ray reflectivity of Ti/MgO multilayers with (a) 1.50-nm and (b) 1.35-nm periods. A simultation of reflectivity shows that the interface roughness is 0.20 and 0.33 nm, respectively. The curves are shifted vertically for clarity.

Fig. 4
Fig. 4

Summary of the rms interface roughness values σ measured on Ni80Nb20/MgO, Fe/MgO, and Ti/MgO multilayers with bilayer period Λ.

Fig. 5
Fig. 5

Soft-x-ray reflectivity of a 60-bilayer, 2.11-nm period Ni80Nb20/MgO multilayer at λ = 3.374 nm. The solid curve represents the simulation to the measured data shown as squares.

Fig. 6
Fig. 6

Soft-x-ray reflectivity of a 65-bilayer, 2.14-nm Fe/MgO multilayer at λ = 3.374 nm. The solid curve represents the simulation to the measured data shown as squares.

Fig. 7
Fig. 7

Thermal stability of 2.4-nm period Ni80Nb20/MgO multilayers in the temperature range 200 °C–600 °C is studied by hard-x-ray reflectivity. The multilayers were annealed for 75 min at each temperature and cooled to room temperature before the reflectivity was measured. The curves are shifted vertically for clarity.

Fig. 8
Fig. 8

Thermal stability of 2.1-nm period Fe/MgO multilayers in the temperature range 200 °C–600 °C is studied by hard-x-ray reflectivity. The multilayers were annealed for 75 min at each temperature and cooled to room temperature before the reflectivity was measured. The curves are shifted vertically for clarity.

Fig. 9
Fig. 9

Effect of annealing at different temperatures is studied by the monitoring of the first-order Bragg peak reflectivity with respect to the as-deposited multilayer. The reflectivity drops for T > 300 °C and the layered structure breaks down at 600 °C.

Tables (1)

Tables Icon

Table 1 Fit Parameters of the Hard-X-Ray Reflectivity Curves Shown in Figs. 1 3 Performed on Samples Consisting of Metal and MgO Bilayers

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