The new Woollam Company newsletter is available!
In this edition, you will find interesting articles on spectroscopic ellipsometry and on the Woollam company and their products. Read, for example, how to perform ellipsometric measurements of coatings on an anisotropic polymer substrate
- iSE – The new, compact in situ ellipsometer
- Portrait: Dr. Zachary Holman, Arizona State University
- Presentation of a brand new book on ellipsometry: “Spectroscopic Ellipsometry for Photovoltaics“ by Hiroyuki Fujiwara and Robert W. Collins
- New camera-based sample alignment for M-2000/RC2
- New spectral enhancement of the VASE to 4 µm
Spectral enhancement of the VASE to 4 µm
Enhancing the spectral range of our instruments is always fascinating, as it opens up new options and applications. Since 2018, we offer our VASE ellipsometer with a spectral range up to 4 µm in the infrared.
So far, we have offered infrared enhancements to 1.7 µm, 2.5 µm and 3.2 µm. A fourth grating on our HS-190 monochromator and a brand new InSb detector cooled with liquid nitrogen now allows operations to 4 µm in the infrared. The detector is sealed in a dewar with liquid nitrogen that can be filled before data acquisition and allows measurement times as long as 8 hours. In combination with a UV-VIS detector, continuous measurements over a spectral range from 193 - 4000 nm are possible.
This spectral range enhancement is useful for the development of infrared camera components, and semi-conductors with low bandwidths. In chemistry, it is also useful for the analysis of vibration absorption in organic and polymer films.
Fig. 2 shows experimental and model data for a polymer-photoresist film on silicon. Multiple absorption structures between 3.2 and 3.6 µm can be recognized. These structures are connected with vibration absorptions in the polymer molecules and show the chemical bonds and concentrations in the film.
The spectra in fig. 2 were analyzed to determine the film thickness of 2014,6 nm and the optical constants n & k of the polymer film. The resulting optical constants are shown in fig. 3.
Various infrared absorptions were modeled with a combination of 10 Gaussian oscillator functions (green curve for k). A Sellmeier function with shorter wavelengths outside the measured spectral band was added, to take the refractive index dispersion into account.
Our 4 µm MWIR option is available as upgrade for all new VASE systems and some of the established system.
Please contact us for further information or a quotation.