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The Refractor2™ is a simple, low cost, in-line grazing angle accessory. It is ideal for recording spectra of thin films on metal substrates. The angle of incidence is fixed at 75°. Excellent spectral contrast results. Large panel samples can be easily analyzed, since the sampling surface is above all of the optical components.
Conventional in-line grazing angle accessories have two major drawbacks. First, the short plane mirrors employed do not totally intercept the beam of the spectrometer, resulting in a significant loss in optical throughput. Second, an external polarizer is typically required. Such an external polarizer is expensive. Both of these drawbacks are overcome with the Refractor2™.
Figure 1. The Refractor.™ Grazing Angle Reflectance Accessory.
In the Refractor2™, the optical beam from the FT-IR spectrometer is deflected to and from the sample via wedged ZnSe windows (see Figure 1). This design results in a compact grazing angle accessory with optimal throughput. The two ZnSe windows are SuperCharged™, which nearly doubles the performance of the Refractor2™. A single Brewster's angle silicon polarizer is located below the sampling plane to provide the required parallel polarization.
Figure 2. Grazing Angle Reflectance Spectrum of SiO2 on an Al Substrate.
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Figure 3. Infrared Grazing Angle Reflectance Spectra of Silicone Lubricant on an Al Substrate.
Figure 2 shows the grazing angle reflectance spectrum of a silicon dioxide film, approximately 500Å thick, on an aluminum substrate. In Figure 3, the grazing angle spectrum of a 100Å layer of silicone lubricant on an aluminum substrate is given. Here, an external KRS-5 wire-grid polarizer is used in place of the internal silicon polarizer.
The Refractor2™ is supplied with all mounting hardware required to install it directly in the spectrometer and is compatible with most FTIR instruments. Alignment is fast and simple. For analyses that require spectral information at frequencies below 500 cm-1, replacement KRS-5 windows are available on a special order. A reaction chamber model, the Refractor Reactor, is available on special order, for analysis of samples in a vacuum or pressurized environment by grazing angle reflectance spectroscopy.
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