Abstract

The vacuum-ultraviolet reflectance of freshly evaporated aluminum films has been measured as a function of time in vacuum after the deposition. The pressure in the experimental chamber during the measurements ranged from 4 × 10−6 mm Hg at the time of the deposition to an ultimate pressure of 2 × 10−7 mm Hg. The first measurements were made less than 10 sec after the evaporation. The reflectance of unoxidized aluminum has been determined by extrapolating the reflectance curves back to zero time. It has been found that unoxidized aluminum has a normal-incidence reflectance greater than 86% for wavelengths down to λ1025 Å. The effect on the reflectance of exposing freshly prepared aluminum films to O2, N2, and air is shown. At λ735 and λ584 Å, the optical constants of unoxidized aluminum have been determined from measurements of reflectance as a function of incidence angle. The optical constants are: at λ735 Å, n = 0.455, k = 0.043; and at λ584 Å, n = 0.71, k = 0.018. The effect of oxidation on the reflectance of aluminum at λ735 and λ584 Å is shown, and the transmission of unsupported films of aluminum, with and without oxide, is calculated.

© 1963 Optical Society of America

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References

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  1. G. Hass and R. Tousey, J. Opt. Soc. Am. 49, 593 (1959).
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  4. G. B. Sabine, Phys. Rev. 55, 1064 (1939).
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  6. G. Hass, W. R. Hunter, and R. Tousey, J. Opt. Soc. Am. 46, 1009 (1956).
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    [Crossref]
  8. W. C. Walker, J. A. R. Samson, and O. P. Rustgi, J. Opt. Soc. Am. 48, 81 (1958).
  9. W. C. Walker, O. P. Rustgi, and G. L. Weissler, J. Opt. Soc. Am. 49, 471 (1959).
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  10. R. P. Madden and L. R. Canfield, J. Opt. Soc. Am. 51, 838 (1961).
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1961 (2)

1960 (1)

1959 (2)

1958 (1)

W. C. Walker, J. A. R. Samson, and O. P. Rustgi, J. Opt. Soc. Am. 48, 81 (1958).

1957 (1)

1956 (1)

1942 (1)

1939 (1)

G. B. Sabine, Phys. Rev. 55, 1064 (1939).
[Crossref]

Angel, D.

Banning, M.

Berning, P. H.

Canfield, L. R.

Hass, G.

Hunter, W. R.

Madden, R. P.

Rustgi, O. P.

W. C. Walker, O. P. Rustgi, and G. L. Weissler, J. Opt. Soc. Am. 49, 471 (1959).
[Crossref]

W. C. Walker, J. A. R. Samson, and O. P. Rustgi, J. Opt. Soc. Am. 48, 81 (1958).

Sabine, G. B.

G. B. Sabine, Phys. Rev. 55, 1064 (1939).
[Crossref]

Samson, J. A. R.

W. C. Walker, J. A. R. Samson, and O. P. Rustgi, J. Opt. Soc. Am. 48, 81 (1958).

Tousey, R.

Walker, W. C.

W. C. Walker, O. P. Rustgi, and G. L. Weissler, J. Opt. Soc. Am. 49, 471 (1959).
[Crossref]

W. C. Walker, J. A. R. Samson, and O. P. Rustgi, J. Opt. Soc. Am. 48, 81 (1958).

Weissler, G. L.

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Figures (13)

Fig. 1
Fig. 1

Sectional view of the combined evaporator–reflectometer used to obtain reflectance measurements of evaporated films before oxidation. The substrate holder is rotated into a vertical position for the measurement of reflectance.

Fig. 2
Fig. 2

Pressure in the vacuum system immediately after a typical high-speed aluminum evaporation. (The deposition, during which the pressure had risen to 3 − 6 × 10−6 mm Hg, ended at 0 sec.)

Fig. 3
Fig. 3

Initial reflectance decrease of freshly deposited aluminum films in vacuum in the vacuum ultraviolet as a function of time in seconds.

Fig. 4
Fig. 4

Reflectance decrease of freshly deposited aluminum films in vacuum at three wavelengths in the vacuum ultraviolet as a function of time up to 40 min.

Fig. 5
Fig. 5

Effect of the speed of evaporation on the reflectance of freshly deposited aluminum films before exposure to air at λ1216Å. The times indicated on the curves represent the duration of the evaporations. All films were 700–900 Å thick.

Fig. 6
Fig. 6

Effect on the reflectance of freshly deposited aluminum films at λ1216 Å of introducing oxygen and nitrogen into the vacuum system.

Fig. 7
Fig. 7

Reflectance of oxide-free evaporated aluminum as a function of wavelength from λ1000 to λ2000 Å. The points are values taken from the curves of Fig. 3 by extrapolating to zero time.

Fig. 8
Fig. 8

Effect of aging in vacuum and in air on the reflectance of evaporated aluminum at three different wavelengths in the vacuum ultraviolet. The films were exposed to air after measuring their reflectance decay in vacuum for 8 min.

Fig. 9
Fig. 9

Reflectance of aluminum films as a function of incidence angle at different stages of aging for λ584 and λ735 Å. Lower curves: after 24-h exposure to air; middle curves: after 13 min in vacuum; upper curves: calculated initial reflectance fitted to extrapolated data points at 50° and 60°. The film thicknesses are as indicated.

Fig. 10
Fig. 10

Reflectance decrease in vacuum of freshly deposited aluminum films as a function of time at an incidence angle of 60° for λ584 Å.

Fig. 11
Fig. 11

Calculated reflectance at 50° and 60° angles of incidence as a function of absorption coefficient of a film material with n = 0.71 (critical angle = 45.25°).

Fig. 12
Fig. 12

Calculated effect of film thickness of aluminum on glass at two angles of incidence larger than the critical angles for λ584 and λ735 Å.

Fig. 13
Fig. 13

Calculated effect of oxide thickness on the reflectance of, 1000-Å-thick aluminum films on glass as a function of incidence angle for λ584 and λ735 Å.

Tables (1)

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Table I Calculated transmittance of unsupported aluminum films with equal thicknesses of oxide on each surface.

Equations (2)

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λ 584 Å : n = 0.71 k = 0.018 , λ 735 Å : n = 0.455 k = 0.043.
Al 2 O 3 { λ 584 Å : n = 0.74 k = 0.56 , λ 735 Å : n = 1.05 k = 0.80 ; glass { λ 584 Å : n = 0.83 k = 0.45 , λ 735 Å : n = 1.12 k = 0.70.