R. W. Alexander

Optical properties of the metals Al, Co, Cu, Au, Fe, Pb, Ni, Pd, Pt, Ag, Ti, and W in the infrared and far infrared

Infrared optical constants collected from the literature are tabulated. The data for the noble metals and Al, Pb, and W can be reasonably fit using the Drude model. It is shown that -epsilon1(omega) = epsilon2(omega) approximately omega(2)(p)/(2omega(2)(tau)) at the damping frequency omega = omega(tau). Also -epsilon1(omega(tau)) approximately - (1/2) epsilon1(0), where the plasma frequency is omega(p).

Optical properties of fourteen metals in the infrared and far infrared: Al, Co, Cu, Au, Fe, Pb, Mo, Ni, Pd, Pt, Ag, Ti, V, and W.

Infrared optical constants collected from the literature are tabulated for Mo and V. New data are presented for Cu, Fe, and Ni. Drude model parameters ωτ and ωp are given for the fourteen metals Al, Co, Cu, Au, Fe, Pb, Mo, Ni, Pd, Pt, Ag, Ti, V, and W. The Drude model parameters for Cu are revised from our earlier tabulation due to the availability of additional data. Refinements in our fitting technique have resulted in only slight changes in the Drude model parameters for Al, Au, Ag, and W. The Drude model parameters for Pb correct a numerical error in our earlier tabulation. For all fourteen metals, the optical resistivity has been calculated from the Drude model parameters ωτ and ωp and compared to handbook values for the dc resistivity.

Optical properties of Al, Fe, Ti, Ta, W, and Mo at submillimeter wavelengths

Measurements of the optical constants of metals at submillimeter wavelengths are sparse. We have used a nonresonant cavity to measure, at room temperature, the angle averaged absorptance spectra P(omega) of aluminum, molybdenum, tantalum, titanium, tungsten, and iron in the 30-300-cm(-1) wavenumber region. The real part of the normalized surface impedance spectrum, z(omega) = r(omega) + ix(omega), was determined from P(omega). Measurements were also made on iron from 400 to 4000 cm(-1) using standard reflectance techniques. The r(omega) spectrum was combined with previous measurements by others at higher frequencies and Kramers-Kronig analyses of the resultant combined r(omega) spectra provided epsilon(omega) = epsilon(1)(omega) + iepsilon(2)(omega) and N(omega) = n(omega) + ik(omega).

Optical properties of Au, Ni, and Pb at submillimeter wavelengths

Measurements of the optical properties, and thus the optical constants, of metals at submillimeter wavelengths are almost nonexistent. We used a nonresonant cavity to measure at ambient temperature the angle averaged absorptance spectra P(omega) of gold, nickel, and lead in the 30-300-cm(-1) wave-number region. The real part of the normalized surface impedance spectrum z(omega) = r(omega) + ix(omega) was determined from P(omega). The r(omega) spectrum was combined with previous measurements by others at higher frequencies, and Kramers- Kronig analyses of the resultant r(omega) spectra provided (omega) =, (1) (omega) + i(2)(omega) and N(omega) = n(omega) + ik(omega) for gold and nickel in the 35-15,000-cm(-1) region and for lead in the 15-15,000-cm(-1) region. We also derived an exact analytical expression for P(omega) of a metal.

Optical properties of calcite and gypsum in crystalline and powdered form in the infrared and far-infrared

Abstract The complex indices of refraction for crystalline gypsum and calcite were determined from reflectance measurements for both single crystals and pressed powder pellets. These optical constants were determined from a classical dispersive analysis (DA) of the reflectance data to facilitate comparisons between the crystal and powdered data. This study was done to show the usefulness and the limitations of using pressed pellets for determining the complex refractive index of materials unavailable in single crystals.

Multimedia dispersion relation for surface electromagnetic waves

We have derived a general, n−media dispersion relation for surface electromagnetic waves propagating on isotropic layers with complex dielectric functions. The equation is presented in a convenient, compact form for ease of application.

Propagation distances of surface electromagnetic waves in the far infrared

Abstract The propagation distances, L x , of surface electromagnetic waves on metal-air and semiconductor-metal-air systems were measured using the two prism technique in the far infrared (84.2 cm −1 ). Copper, gold, palladium, tungsten, nickel, steel, and platinum metal-air interfaces were studied. Also semiconductor-metal-air systems consisting of Pt films of varying thickness deposited on single crystal GaAs substrates were examined. The experimental values for L x were found to be orders of magnitude lower than theoretical values for these metals.

Absorption in the infrared of surface electromagnetic waves by adsorbed molecules on a copper surface

Experimental observations have been made for the first time that surface electromagnetic wave (SEW) spectroscopy can be used to measure the infrared spectra of adsorbed molecules and very thin films on metal surfaces. Using a tunable CO2 laser (9.2–10.8 μm wavelength), the 975 and the 1037 cm−1 resonances of 5–25 A thick physisorbed benzene on copper were observed. Broadening of these resonances for the thinnest layers of benzene was observed. Also SEW spectroscopy and ellipsometry were used to study thin films of cellulose acetate (15–75 A) on copper. Further, it was shown that film thicknesses determined by SEW spectroscopy are in agreement with the ellipsometric thicknesses and that the SEW method is more sensitive for very thin (<25 A) films.

Propagation distance of surface electromagnetic waves on two metal-oxide-air systems☆

Abstract The propagation distance of surface electromagnetic waves on a copper-cuprous oxide-air system was measured using two prism couplers, for oxide thickness between 20 A and 2000 A, and wavelengths from 9.2 μm to 10.8 μm. The copper sample consisted of an evaporated copper film on glass, with an oxide film overlayer grown by heating in air. The measured values of propagation distance agree well with computer-calculated solutions of the three-media dispersion relation. Similar measurements made on a polished surface of rolled titanium, oxidized by heating in air, give agreement only to within 50%. Auger analysis indicated that a carbide impurity on the highly reactive titanium surface and a variation of the titanium oxide composition with thickness both contributed to the disagreement between measured and calculated values of propagation distance.

Surface Electromagnetic Waves on Metals and Polar Insulators: Some Comments

The important parameters governing the propagation of surface electromagnetic waves (SEW) on metals or polar insulators have been theoretically investigated. General approximations for the propagation distance, decay distance, and penetration depth are presented in summary tables. It is found that the propagation distance of SEW can be used to study overlayer materials on metals, that the penetration depth of SEW fields into a metal is governed by the classical skin depth at low frequencies and by the plasma frequency in the visible wavelength region, that surface phonons can propagate over a centimeter on PbS, PbTe, and ferroelectrics, and that the propagation distances of SEW increase with decreasing temperature.