Ellipsometry in the study of selective radiation-absorbing surfaces

Ellipsometry is an inexpensive technique whereby the optical properties of surfaces are investigated by analyzing the polarization of reflected light. The experimental system consists of a source of monochromatic light of known wavelength, a suitable quarter wave plate, and two polaroids, mounted on rotatable discs with circular vernier scales for measuring the orientation of the transmission axes with respect to the plane of incidence. The system provides sensitive measurements of both optical constants and coating thicknesses, which are then used to compute the reflectivity of the surface at different wavelengths. The method was applied to single and double black nickel layers electro-deposited on polished copper substrates using the Silo and Mladinik (1969) electrolyte (nickel ammonia sulfate, zinc sulfate, potassium thiocyanide). Results are in good agreement with previously reported data.