Reststrahl Reflection Characteristics of Amorphous Silica

Kenzo Sato, Miyoko Shibata

The Reststrahl reflection characteristics in the wavelength region 1-25µ of silica films, a few thousand ångstroms in thickness, have been studied. The films were grown on silicon wafers under controlled conditions. The reflection maxima in the Si-O stretching and Si-O bending bands, which are observed with crystalline quartz at 9.1 and 20.4µ respectively, are found to shift to the longer wavelength side. With the decrease in film thickness, the Reststrahl wavelengths increase and the Reststrahl intensities decrease. A tentative explanation is given of these features, assuming that there are unsaturated Si atoms, i.e. those with one, two or three dangling bonds, in a very thin layer immediately below the free surface of the film. Some observations have also been made on the influence on the Reststrahl reflection of the impurities present in the silica film and of the growth conditions of the film. © 1966, THE PHYSICAL SOCIETY OF JAPAN. All rights reserved.

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Materials
Curve 1
Temperature K: ~298 Wavelength Range, µm: 0.166-0.248 Geometry θ θ': 14° 14° Composition (weight percent), Specifications, and Remarks: Similar to the above specimen and conditions except optical density >2 at 6.1 eV.
Curve 1
Temperature K: ~298 Wavelength Range, µm: 0.169-0.247 Geometry θ θ': 14° 14° Composition (weight percent), Specifications, and Remarks: Similar to the above specimen and conditions except optical density = 0.162 at 6.0 eV.
Curve 2
Temperature K: ~298 Wavelength Range, µm: 0.169-0.248 Geometry θ θ': 14° 14° Composition (weight percent), Specifications, and Remarks: Similar to the above specimen and conditions except optical density = 0.728 at 6.0 eV.
Curve 1
Temperature, K: ~298 Wavelength Range, µm: 1.54-24.86 Geometry θ θ' ω': 10° 10° Composition (weight percent), Specifications, and Remarks: Phosphorous doped (10¹⁷ cm⁻³) silicon oxidized by heating to 1473 K in wet oxygen; formed an amorphous silica film (5500 Å thick); data extracted from smooth curve.
Curve 2
Temperature, K: ~298 Wavelength Range, µm: 6.00-13.00 Geometry θ θ' ω': 10° 10° Composition (weight percent), Specifications, and Remarks: Phosphorous doped (10¹⁷ cm⁻³) silicon oxidized by heating to 1473 K in oxygen reaction tube and then exposing to air; formed an amorphous silica film (5200 Å thick); coating etched in CP₄; data extracted from smooth curve.
Curve 3
Temperature, K: ~298 Wavelength Range, µm: 6.00-13.00 Geometry θ θ' ω': 10° 10° Composition (weight percent), Specifications, and Remarks: Above specimen and conditions except film thickness reduced to 4650 Å by etching in CP₄.
Curve 4
Temperature, K: ~298 Wavelength Range, µm: 6.00-13.00 Geometry θ θ' ω': 10° 10° Composition (weight percent), Specifications, and Remarks: Above specimen and conditions except film thickness reduced to 3650 Å by etching in CP₄.
Curve 5
Temperature, K: ~298 Wavelength Range, µm: 6.00-13.00 Geometry θ θ' ω': 10° 10° Composition (weight percent), Specifications, and Remarks: Above specimen and conditions except film thickness reduced to 3250 Å by etching in CP₄.
Curve 6
Temperature, K: ~298 Wavelength Range, µm: 6.00-13.00 Geometry θ θ' ω': 10° 10° Composition (weight percent), Specifications, and Remarks: Above specimen and conditions except film thickness reduced to 3000 Å by etching in CP₄.
Curve 7
Temperature, K: ~298 Wavelength Range, µm: 6.00-13.00 Geometry θ θ' ω': 10° 10° Composition (weight percent), Specifications, and Remarks: Above specimen and conditions except film thickness reduced to 2750 Å by etching in CP₄.
Curve 8
Temperature, K: ~298 Wavelength Range, µm: 6.00-13.00 Geometry θ θ' ω': 10° 10° Composition (weight percent), Specifications, and Remarks: Above specimen and conditions except film thickness reduced to 2500 Å by etching in CP₄.
Curve 9
Temperature, K: ~298 Wavelength Range, µm: 6.00-13.00 Geometry θ θ' ω': 10° 10° Composition (weight percent), Specifications, and Remarks: Above specimen and conditions except film thickness reduced to 2250 Å by etching in CP₄.
Curve 10
Temperature, K: ~298 Wavelength Range, µm: 6.00-13.00 Geometry θ θ' ω': 10° 10° Composition (weight percent), Specifications, and Remarks: Above specimen and conditions except film thickness reduced to 2000 Å by etching in CP₄.
Curve 11
Temperature, K: ~298 Wavelength Range, µm: 6.00-13.00 Geometry θ θ' ω': 10° 10° Composition (weight percent), Specifications, and Remarks: Above specimen and conditions except film thickness reduced to 1250 Å by etching in CP₄.
Curve 12
Temperature, K: ~298 Wavelength Range, µm: 6.00-13.00 Geometry θ θ' ω': 10° 10° Composition (weight percent), Specifications, and Remarks: Above specimen and conditions except film thickness reduced to 1000 Å by etching in CP₄.
Curve 13
Temperature, K: ~298 Wavelength Range, µm: 6.00-13.00 Geometry θ θ' ω': 10° 10° Composition (weight percent), Specifications, and Remarks: Above specimen and conditions except film thickness reduced to 750 Å by etching in CP₄.
Curve 14
Temperature, K: ~298 Wavelength Range, µm: 6.00-13.00 Geometry θ θ' ω': 10° 10° Composition (weight percent), Specifications, and Remarks: Above specimen and conditions except film thickness reduced to < 750 Å by etching in CP₄.
Curve 15
Temperature, K: ~298 Wavelength Range, µm: 2.01-14.00 Geometry θ θ' ω': 10° 10° Composition (weight percent), Specifications, and Remarks: Arsenic doped (10¹⁹ cm⁻³) silicon oxidized by heating to 1473 K in dry oxygen; formed an amorphous silica film; data extracted from smooth curve.
Curve 16
Temperature, K: ~298 Wavelength Range, µm: 1.62-14.00 Geometry θ θ' ω': 10° 10° Composition (weight percent), Specifications, and Remarks: Similar to above specimen and conditions except surface film grown in wet oxygen.