Optical Properties of Epitaxial PbS Films in the Energy Range 2-6 eV

C. E. Rossi, William Paul

The reflectivity of epitaxial PbS films has been compared with the reflectivity of bulk PbS in the energy range 2.1 to 6.2 eV and found to agree in both magnitude and structure within a few percent at energies where interference effects can be neglected. The transmission of several films with thicknesses varying from 335 to 550 Å has been measured and the structure and shape of the spectra shown to be the same for the films with different thicknesses. The reflectivity of bulk PbS between 2.1 and 6.2 eV has been combined with measurements made by other workers outside of this range to compute optical constants from the Kramers Kronig relation. The optical constants obtained in this manner appear to agree quite well (within about 10% in most cases) with those obtained from the reflectivity and transmission of the films, considering the experimental difficulties experienced in measuring film thickness and the absolute magnitude of the reflectivity. © 1967 The American Institute of Physics.

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Materials
Curve 1
Temperature K: ~298 Wavelength Range, μm: 0.200-0.596 Geometry θ' θ'': ~0°-0° Reported Error, %: ± 5 Composition (weight percent), Specifications, and Remarks: Crystalline; cleaved.
Curve 2
Temperature K: ~298 Wavelength Range, μm: 0.200-0.605 Geometry θ' θ'': ~0°-0° Reported Error, %: ± 5 Composition (weight percent), Specifications, and Remarks: Similar to above specimen and conditions except film 410 Å thick.
Curve 3
Temperature K: 298 Wavelength Range, μm: 0.200-0.599 Geometry θ' θ'': ~0°-0° Reported Error, %: ± 5 Composition (weight percent), Specifications, and Remarks: Similar to the above specimen and conditions except film 470 Å thick.
Curve 4
Temperature K: 298 Wavelength Range, μm: 0.200-0.602 Geometry θ' θ'': ~0°-0° Reported Error, %: ± 5 Composition (weight percent), Specifications, and Remarks: Epitaxial PbS film (550 Å thick); NaCl substrate (~8 mm thick) cleaved in air; powdered natural PbS evaporated in vacuum (5 x 10⁻⁵ mm Hg) at 200 Å min⁻¹ and at a substrate temp of 573 K.
Curve 1
Temperature K: 298 Wavelength Range, μm: 0.200-0.605 Geometry θ' θ'': ~0°-0° Reported Error, %: ± 10-25 Composition (weight percent), Specifications, and Remarks: Epitaxial film (325 Å thick); NaCl substrate (~8 mm thick) cleaved in air; powdered natural PbS evaporated in vacuum (5 x 10⁻⁵ mm Hg) at 40 to 80 Å min⁻¹ and at a substrate temp of 573 K.
Curve 2
Temperature K: 298 Wavelength Range, μm: 0.200-0.608 Geometry θ' θ'': ~0°-0° Reported Error, %: ± 10-25 Composition (weight percent), Specifications, and Remarks: Similar to the above specimen and conditions except with 410 Å film thickness.
Curve 3
Temperature K: 298 Wavelength Range, μm: 0.200-0.605 Geometry θ' θ'': ~0°-0° Reported Error, %: ± 10-25 Composition (weight percent), Specifications, and Remarks: Similar to the above specimen and conditions except with 470 Å film thickness.
Curve 4
Temperature K: 298 Wavelength Range, μm: 0.200-0.605 Geometry θ' θ'': ~0°-0° Reported Error, %: ± 10-25 Composition (weight percent), Specifications, and Remarks: Epitaxial film (550 Å thick); NaCl substrate (~8 mm thick) cleaved in air; powdered natural PbS evaporated in vacuum (5 x 10⁻⁵ mm Hg) at 200 Å min⁻¹ and grown at a substrate temperature of 573 K.