Quantitative comparison of ATR-IR spectra of LB and bulk layers of 22-tricosenic acid on inorganic supports

A novel internal reflection element (IRE) for attenuated total reflection Fourier transform infrared (ATR-FT-IR) spectral acquisition is introduced and applied for several surface-sensitive measurements. It is based on microstructured double-side-polished (100) silicon wafers with v-shaped grooves of {111} facets on their backside. These facets of the so-called "microstructured single-reflection elements" (mSRE) are formed by a crystal-oriented anisotropic wet etching process within a conventional wafer structuring process. They are used to couple infrared radiation into and out of the IRE. In contrast to the application of the commonly used silicon multiple-reflection elements (MRE), the new elements provide single-reflection ATR measurements at the opposite wafer side by using simple reflection accessories without any special collimation. Due to the short light path, the spectral range covers the entire mid-infrared region with a high optical throughput, including the range of silicon lattice vibrations from 300 to 1500 cm(-1). In addition to typical ATR applications, i.e., the measurement of bulk liquids and soft materials, the new reflection elements can be effectively used and customer-specifically designed for in situ and ex situ investigations of aqueous solutions, thin films, and monolayers on Si. Examples presented in this article are in situ etching of native as well as thermal SiO(2) and characterization of polydimethylsiloxane (PDMS) films on Si under various measuring conditions.

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Applications of Microstructured Silicon Wafers as Internal Reflection Elements in Attenuated Total Reflection Fourier Transform Infrared Spectroscopy

Schumacher

Künzelmann²,

Vasil'ev³

et al. 2010

Optical Contact in ATR/FT-IR Spectroscopy

Ekgasit

Padermshoke

2001

Optical contact between an internal reflection element (IRE) and a sample is crucial for obtaining a good spectrum in an attenuated total reflection (ATR) experiment. When an air gap is present between the IRE and the sample, the spectrum severely deteriorates. Two techniques for determining the goodness of contact are proposed—first, by making a comparison between polarized ATR spectra and, second, by making a comparison between ATR and transmission spectra. When the optical contact is achieved, the normalized p-polarized ATR spectrum is exactly the same as the normalized s-polarized ATR spectrum. Moreover, the ratio between the normalized absorbance measured in the ATR mode and the normalized absorbance measured in the transmission mode equals the ratio between the frequency being considered and the normalization frequency. Theoretical and experimental investigations have been performed in order to verify the proposed techniques.

Novel Attenuated Total Reflection Fourier Transform Infrared Microscopy Using a Gem Quality Diamond as an Internal Reflection Element

Ekgasit

Thongnopkun

2005

A novel technique for attenuated total reflection Fourier transform infrared (ATR FT-IR) spectral acquisition by an infrared microscope with a gem-quality faceted diamond as an internal reflection element (IRE) is introduced. Unlike conventional IREs, the novel diamond IRE has a sharp tip configuration instead of a flat tip configuration. Light at normal incidence was coupled into the diamond while the transflected radiation from the diamond was collected through the table facet by the built-in 15x Cassegrainian objective. The number of reflections in the novel diamond IRE equals two. The evanescent field generated under total internal reflection at the pavilion facet was exploited for ATR spectral acquisition of materials attached to the IRE. The observed ATR spectra were compared to those obtained via a traditional zinc selenide IRE.