Universal ultrahigh vacuum facility for the measurement of the optical properties of solids.

An apparatus is described in which the reflectance and transmittance of a hot sample and a cold sample may be measured simultaneously and differentially in the wavelength region from the infrared to the vacuum ultraviolet. These measurements may be carried out under an ultrahigh vacuum or a gaseous ambience, and the surfaces may be temperature treated (e.g., flashed atomically clean) before the measurement. The hotcold differential capability of the apparatus is convenient when considering the temperature dependence of optical parameters.

Optical properties of very thin, nonideal multilayer superlattice stacks.

In this study, the theory of very thin, nonideal multilayer stacks is developed, and the computed wavelength variation of the transmissivity and reflectivity is compared with that measured on experimentally prepared silver-silicon monoxide layer stacks. The model imputes a step-function character to the complex index of refraction along the layer structure, and nonideality is accounted for by allowing for the likely presence of interfacial layers between each primary layer pair and also for the possibility that the thickness of the individual layers may vary randomly within some limit of error. Abeles's transfer matrix technique is used to arrive at the characteristic matrix of the stack, and additive corrective matrices are derived to account for the effects due to interfacial layers and the random layer thickness variation.

Computation of the optical properties of nonideal multilayer structures.

A general computer program was developed to calculate the reflectivity, transmissivity, and absorptivity of nonideal multilayer structure devices. The program allows for error-based variation in layer thicknesses and also for the formation of interfacial layers between the primary layers. The main text of the program consists of the calculation of the matrix elements of the characteristic matrix T for any given two-component layer structure. The treatment is not restricted to any particular range of wavelength, type of material forming the layer structure, or number of layers in the chosen system. The pertinent parameters entering the calculations are the thicknesses of the individual layers (which are permitted to vary randomly within some limit of error); the thicknesses of the interfacial layers; the complex indices of refraction of the substrate, the pertinent layers, and the surrounding ambience; and the structural makeup of the layer stacking.