Dispersion of Amorphous Boron Films in the Near Infrared ANNE M. MURPHY Physical Electronics Laboratory, Melpar, Inc., Falls Church, Virginia 22046 (Received 21 January 1967) INDEX HEADINGS: Infrared; Boron; Films; Dispersion; Refractive index. T HE lack of available data on the dispersion of boron prompts this brief note. The index of refraction of deposited, amorphous boron films was calculated from interference fringes of transmission curves using the expression 2nd = mλ. 1 The thickness (d) was adjusted so FIG. 1. Index of refraction versus wavelength of boron films. Moss 1 ×; Gebhart, 4 two samples, Δ and ▲; Morita 5 □ (dashed curve); measured values O (solid curve). that the first order of interference could be easily detected. This removed any ambiguity in selecting the order (m). A Cary 14 spectrophotometer was used in the range of 0.2 μ to 2.0 μ while a Beckman IR5A was used from 2.0 μ to 4.0 μ. The films were deposited by electron bombardment of a boron rod (>99.99% pure) in a vacuum of 10 –5 torr onto fused silica and Irtran-2 2 substrates. The amorphous structure of the films and the details of deposition have been described by Feldman et al. 3 A total of 45 films were examined in order to reduce possible errors in thickness measurements which were made on a Zeiss interference microscope. The accuracy of index measurement is estimated to be between 1% and 2%. The results of the measurements are shown in Fig. 1, and compared with those reported in the literature by Gebhart and Jacobs- meyer, 4 Morita, 5 and Moss. 1 Morita examined films which were probably amorphous, while Gebhart and Moss examined various crystalline specimens. The author wishes to thank K. Hoggarth for film deposition, Charles Feldman for suggesting these measurements, and the National Aeronautical and Space Administration, Contract No. NAS-934 for partial support. 1 T. S. Moss, Optical Properties of Semiconductors (Butterworth Scientific Publications, London, 1959). 2 Irtran-2 obtained from Eastman-Kodak Co., Rochester, N. Y. 3 C. Feldman, F. Ordway, W. Zimmerman, III, and K. Moorjani, in Boron, Vol. 2, G. K. Gaule, Ed. (Plenum Press, New York, 1965). 4 F. L. Gebhart and V. P. Jacobsmeyer in Boron, Vol. 2, G. K. Gaule, Ed. (Plenum Press, New York, 1965). 5 I. N. Morita. J. Sci. Res. Inst. (Tokyo) 48, 8 (1954). June 1967 845

Dispersion of Amorphous Boron Films in the Near Infrared

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Dispersion of Amorphous Boron Films in the Near Infrared

ANNE M. MURPHY Physical Electronics Laboratory, Melpar, Inc.,

Falls Church, Virginia 22046 (Received 21 January 1967)

INDEX HEADINGS: Infrared; Boron; Films; Dispersion; Refractive index.

THE lack of available data on the dispersion of boron prompts this brief note.

The index of refraction of deposited, amorphous boron films was calculated from interference fringes of transmission curves using the expression 2nd = mλ.1 The thickness (d) was adjusted so

FIG. 1. Index of refraction versus wavelength of boron films. Moss1 × ; Gebhart,4 two samples, Δ and ▲; Morita5 □ (dashed curve); measured values O (solid curve).

that the first order of interference could be easily detected. This removed any ambiguity in selecting the order (m). A Cary 14 spectrophotometer was used in the range of 0.2 µ to 2.0 µ while a Beckman IR5A was used from 2.0 µ to 4.0 µ. The films were deposited by electron bombardment of a boron rod (>99.99% pure) in a vacuum of 10–5 torr onto fused silica and Irtran-2 2

substrates. The amorphous structure of the films and the details of deposition have been described by Feldman et al.3 A total of 45 films were examined in order to reduce possible errors in thickness measurements which were made on a Zeiss interference microscope. The accuracy of index measurement is estimated to be between 1% and 2%.

The results of the measurements are shown in Fig. 1, and compared with those reported in the literature by Gebhart and Jacobs-meyer,4 Morita,5 and Moss.1 Morita examined films which were probably amorphous, while Gebhart and Moss examined various crystalline specimens.

The author wishes to thank K. Hoggarth for film deposition, Charles Feldman for suggesting these measurements, and the National Aeronautical and Space Administration, Contract No. NAS-934 for partial support.

1 T. S. Moss, Optical Properties of Semiconductors (Butterworth Scientific Publications, London, 1959). 2 Irtran-2 obtained from Eastman-Kodak Co., Rochester, N. Y. 3 C. Feldman, F. Ordway, W. Zimmerman, III, and K. Moorjani, in Boron, Vol. 2, G. K. Gaule, Ed. (Plenum Press, New York, 1965). 4 F. L. Gebhart and V. P. Jacobsmeyer in Boron, Vol. 2, G. K. Gaule, Ed. (Plenum Press, New York, 1965). 5 I. N. Morita. J. Sci. Res. Inst. (Tokyo) 48, 8 (1954).

June 1967 845