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IR-VASE^® Applications

Optical Coatings

Characterize thickness and IR index of single and multilayer fi lms. Bulk uncoated
substrates. Infrared optical systems. AR, HR, single-layer and multilayer coatings.
High-index and low-index.

Molecular Bond Vibrations

Like standard FTIR spectroscopy, IR ellipsometry relies on the information about molecular bond vibrations. Infrared absorption caused by these vibrations can be studied in bulk or thin film materials. IR ellipsometry offers increased sensitivity over FTIR spectroscopy. It also presents the advantage of obtaining both n and k rather than just absorbance values. Figures below show measured optical constants of a silicone thin film with vibrational absorptions labeled.

Multilayer Characterization

Multilayer films can be extensively studied using the wide spectral range and variable angle capability of the IR-VASE®. Multiple angles provide additional information by changing the light's path length through each layer. The following results show sensitivity to 3 layers. Infrared optical contrast between similar materials allows measurement of each layer's thickness.

IR-VASE Ellipsometer Applications - Multilayer on Si

IR-VASE Ellipsometer Applications - Psi Delta of Infrared Multilayer

Epitaxial Layers, Doping Concentration and Doping Profiles

At infrared wavelengths, the difference in free-carrier levels can cause optical contrast between epitaxial or implanted layers. This gives IR-VASE® excellent sensitivity to epitaxial layer thickness and substrate doping concentration. The ellipsometer also has good sensitivity to carrier gradients at interfaces. Carrier profiles show near-perfect in agreement when nondestructive IR-VASE® and destructive SIMS measurements are compared.

IR-VASE Ellipsometer Applications - Epitaxial Layers, Doping Concentration and Doping Profiles
T.E. Tiwald et al., Phys. Rev. B, 60 (1999) 11 464.

Phonon Structure (Compound Semiconductors)

The Wide spectral range IR-VASE® is important for phonon absorption studies. Data on the left show phonon modes of a GaN / AlGaN laser structure, modeled to determine alloy ratios, doping concentrations, and film quality.

IR-VASE Ellipsometer Applications - Phonon Structure
M. Schubert et al., SPIE Vol. 4449-8 (2001)