Optical measurement of the refractive index, layer thickness, and volume changes of thin films

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Abstract
Preparation, measurement, and calculation methods are discussed for the determination of the complex index of refraction, the layer thickness, and induced volume changes of thin layers (due to a phase change, for example). The principle of the calculation is fitting a curve in the reflectance–transmittance plane measured on a range of layer thicknesses, instead of fitting the reflectance and transmittance as a function of independently measured layer thicknesses. This general method is applied to thin films of GaSb and InSb, in which a laser-induced amorphous-to-crystalline transition can be used in optical recording. The information essential for optical recording applications is measured quickly by making use of a stepwise prepared layer thickness distribution, while the complex refractive index and the layer thicknesses can also be calculated unambiguously.