The equations describing ellipsometry were first derived in 1887 by Paul Drude, who is well known for his ‘Drude Model’ that expresses the optical properties of metals and semiconductors. However, it was not until 1975 when Apnes merged spectroscopy and ellipsometry into a crude version of the system used today. Further advances were made in the 1980s and 1990s to improve the real-time monitoring and precision of the device. Today, spectroscopic ellipsometry is used to measure the optical constants of materials and once those are known, the thicknesses of sub-monolayer films can be determined.
Ellipsometry is an optical measurement technique that characterizes materials based on the changes in the light after reflection or transmission at a sample. Ellipsometry, named because light often takes on an elliptical polarization state upon reflection or t...
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...etup is mathematically equivalent to that of a rotating polarizer setup. In a rotating polarizer setup, tan(P) is replaced with tan (A). The optical configuration for both experimental setups is exactly the same. The only change is to which part optical part rotates during the analysis. In RAE, S3 is not measured and thus the error of the measurement increases as Δ approaches 0 and 180 degrees. To overcome this problem, a compensator can be introduced to the instrument design. A compensator is another optical tool that introduces as phase shift, δ and is typically placed after the sample but prior to the analyzer in the setup. The compensator allows for all of the Stokes parameters to be measured which drastically reduces the error in the measurement. This also provides an additional method of measurement for ellipsometers, rotating compensator ellipsometry.
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