Abstract

A near-normal incidence (~6°) reflectometer system is described that records continuously and directly the reflectance R(ω) as a range of photon energies is scanned. The system has an absolute error of ±2 × 10−2 and a relative error of ±2 × 10−5. It incorporates a quartz light pipe rotating at 70 Hz which captures light from the incident and the reflected beam, respectively, during about 20% of its period of rotation in either case. A gating circuit separates the output signal of the photomultiplier into two channels, corresponding to the incident and the reflected beam, respectively. The signal corresponding to the incident beam is kept constant by a servo system which regulates the gain of the photomultiplier. The reflectance is thus proportional to the signal of the second channel, which is recorded as a function of photon energy. Portions of the reflectance spectrum of Ge are given as examples. No trace of a fine structure in the reflectance of Ge below 2 eV is found.

© 1969 Optical Society of America

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References

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  1. T. S. Robinson, Proc. Phys. Soc. London B65, 901 (1952); H. R. Philipp, E. A. Taft, Phys. Rev. 113, 1002 (1959).
    [Crossref]
  2. See, e.g., H. E. Bennett, W. F. Koehler, J. Opt. Soc. Amer. 50, 1 (1960).
    [Crossref]
  3. The same geometry of the light pipe has been used previously for reflectance measurements in the vacuum uv. For this application, the front surface was coated with a sodium salicylate layer. The light pipe was turned by hand. Results obtained with this set up were reported by U. Gerhardt, E. Mohler, Phys. Stat. Sol. 18, K45 (1966).
    [Crossref]
  4. R. F. Potter, J. Phys. Soc. Japan 21, 107 (1966). The optical constants given in this paper were obtained from polarimetry measurements, using large angles of incidence. This fact might make polarimetry measurements more sensitive to surface layers than measurements of the reflectance at normal incidence.

1966 (2)

The same geometry of the light pipe has been used previously for reflectance measurements in the vacuum uv. For this application, the front surface was coated with a sodium salicylate layer. The light pipe was turned by hand. Results obtained with this set up were reported by U. Gerhardt, E. Mohler, Phys. Stat. Sol. 18, K45 (1966).
[Crossref]

R. F. Potter, J. Phys. Soc. Japan 21, 107 (1966). The optical constants given in this paper were obtained from polarimetry measurements, using large angles of incidence. This fact might make polarimetry measurements more sensitive to surface layers than measurements of the reflectance at normal incidence.

1960 (1)

See, e.g., H. E. Bennett, W. F. Koehler, J. Opt. Soc. Amer. 50, 1 (1960).
[Crossref]

1952 (1)

T. S. Robinson, Proc. Phys. Soc. London B65, 901 (1952); H. R. Philipp, E. A. Taft, Phys. Rev. 113, 1002 (1959).
[Crossref]

Bennett, H. E.

See, e.g., H. E. Bennett, W. F. Koehler, J. Opt. Soc. Amer. 50, 1 (1960).
[Crossref]

Gerhardt, U.

The same geometry of the light pipe has been used previously for reflectance measurements in the vacuum uv. For this application, the front surface was coated with a sodium salicylate layer. The light pipe was turned by hand. Results obtained with this set up were reported by U. Gerhardt, E. Mohler, Phys. Stat. Sol. 18, K45 (1966).
[Crossref]

Koehler, W. F.

See, e.g., H. E. Bennett, W. F. Koehler, J. Opt. Soc. Amer. 50, 1 (1960).
[Crossref]

Mohler, E.

The same geometry of the light pipe has been used previously for reflectance measurements in the vacuum uv. For this application, the front surface was coated with a sodium salicylate layer. The light pipe was turned by hand. Results obtained with this set up were reported by U. Gerhardt, E. Mohler, Phys. Stat. Sol. 18, K45 (1966).
[Crossref]

Potter, R. F.

R. F. Potter, J. Phys. Soc. Japan 21, 107 (1966). The optical constants given in this paper were obtained from polarimetry measurements, using large angles of incidence. This fact might make polarimetry measurements more sensitive to surface layers than measurements of the reflectance at normal incidence.

Robinson, T. S.

T. S. Robinson, Proc. Phys. Soc. London B65, 901 (1952); H. R. Philipp, E. A. Taft, Phys. Rev. 113, 1002 (1959).
[Crossref]

J. Opt. Soc. Amer. (1)

See, e.g., H. E. Bennett, W. F. Koehler, J. Opt. Soc. Amer. 50, 1 (1960).
[Crossref]

J. Phys. Soc. Japan (1)

R. F. Potter, J. Phys. Soc. Japan 21, 107 (1966). The optical constants given in this paper were obtained from polarimetry measurements, using large angles of incidence. This fact might make polarimetry measurements more sensitive to surface layers than measurements of the reflectance at normal incidence.

Phys. Stat. Sol. (1)

The same geometry of the light pipe has been used previously for reflectance measurements in the vacuum uv. For this application, the front surface was coated with a sodium salicylate layer. The light pipe was turned by hand. Results obtained with this set up were reported by U. Gerhardt, E. Mohler, Phys. Stat. Sol. 18, K45 (1966).
[Crossref]

Proc. Phys. Soc. London (1)

T. S. Robinson, Proc. Phys. Soc. London B65, 901 (1952); H. R. Philipp, E. A. Taft, Phys. Rev. 113, 1002 (1959).
[Crossref]

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Figures (7)

Fig. 1
Fig. 1

Schematic diagram of the system.

Fig. 2
Fig. 2

Top view showing the geometry of the sample and bent light pipe.

Fig. 3
Fig. 3

Photomultiplier output measured across 10 kΩ of the gating circuit (see Fig. 4). The larger peaks correspond to the I0 channel and the smaller peaks to the RI0 channel. The upper trace is with the gating circuit turned off and the lower trace is with the gating circuit operating.

Fig. 4
Fig. 4

Gating circuit.

Fig. 5
Fig. 5

The reflectance of P type Ge (0.074 Ω cm) from 1.6 eV to 5.2 eV. Vibration coupling to the monochromator causes a wavelength modulation, which produces a bump in the reflectance near the strong xenon line at 4.85 eV. The energy resolution given in the bottom part is the half-width of atomic mercury lines, as recorded with our system.

Fig. 6
Fig. 6

The reflectance of Ge from 1.6 eV to 3.2 eV in expanded scale (same sample as Fig. 5).

Fig. 7
Fig. 7

The reflectance of Ge from 2.04 eV to 2.32 eV in drastically expanded scale (same sample as Fig. 5). The vertical arrows indicate the relative error of the measurement.

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