Infrared characterization of surfaces and coatings by internal-reflection spectroscopy

Abstract

Some problems which arise in the characterization of surfaces and coatings by internal reflection spectroscopy are described. The ir spectra of bare CaF(2) trapezoids and of ThF(4)- and ZnSe-coated trapezoids exhibit absorption bands in the same spectral region as those of H(2)O and hydrocarbon impurities. In accord with previous investigations, it is observed that the absorptance due to water is much greater in the ThF(4) films than in the ZnSe films or on the CaF(2) surfaces. These results suggest that the water is distributed throughout the ThF(4) films, whereas for ZnSe it resides primarily on the surface. In addition, a number of interesting observations on the desorption and adsorption of water and hydrocarbons to these materials are made. The experimentally observed absorptances are analyzed on the basis of the reflectance for a threelayer system. The analysis enables reasonably quantitative values for the absorption coefficient to be determined for these thin-film coatings.

Study of the Orientation Dependent Etching and Initial Anodization of Si in Aqueous KOH

“…Removing of the native oxide in HF, two rinsings in deionized water, blowing dry, and remeasuring within 10 rain always reduced these values by less than a factor of two. We assume this to be the limit set by the assumed n and k for St, instrumental misalignment, adsorbed water and hydrocarbons (30), and partially regrown oxide. While the absolute values of thickness may be in question in the thin-film regime ~ 100A, the relative increase in thickness as anodization takes place is easy to determine because A increases initially at about 0.35 deg/A.…”

Angular behavior of the Berreman effect investigated in uniform Al2O3layers formed by atomic layer deposition

“…Clarification is needed however on whether the quantity A tot (ω LO ) corresponds to absorptance [23][24][25] α = (1 − T − R) × 100, where T is transmittance and R reflectance, or simply to transmission absorbance −Log 10 (T ). Experimental absorptance in IR spectroscopy requires separate measurement of reflection and transmission, which is cumbersome and rarely adopted for analysis of thin organic and inorganic layers [24][25][26][27][28][29][30]. Thus, usually, in transmission IR spectroscopy, simply transmission absorbance is considered.…”