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

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.