Optical techniques are usually the preferred method for measuring thin films because they are accurate, non-destructive, and require little or no sample preparation.

Optical techniques can determine the thickness, roughness and optical constants of a film. Spectrophotometry is an optical technique where the reflectivity is measured over a wide range of different wavelengths. Reflection occurs whenever light passes through an interface between different materials and the amount of light that is reflected depends on the different in the optical properties (n and k) at the interface.

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