FOURIER-TRANSFORM IR EMISSION STUDIES OF WEAKLY EMITTING OVERLAYERS ON METAL-SURFACES - EXPERIMENTAL AND SPECTRAL-RATIOING PROCEDURES AND THE COMPARATIVE USE OF ROOM-TEMPERATURE TRIGLYCINE SULFATE AND LOW-TEMPERATURE MERCURY CADMIUM TELLURIDE DETECTORS

A description is given of procedures developed for the measurement of weak emission spectra from overlayers on metal surfaces using i.r. Fourier-transform interferometry. Emittance spectra are obtained by ratioing the emission spectrum of the sample against the emission spectrum of a blackbody at the same temperature. Emission from the beam-splitter of the interferometer is eliminated by interferogram subtraction prior to the above ratioing procedure. It is shown that a mercury cadmium telluride photoconductive detector used at liquid nitrogen temperatures gives an i.r. signal/noise better by more than an order of magnitude over the wavenumber range 3300-700 cm-1 compared with the triglycine sulphate room temperature pyro-electric detector when normally used with a fast scanning interferometer. Weak emission spectra from an oxide layer of 6 nm (60 Å) thickness on aluminium are described as a function of the angle between the normal to the emitting surface and the optical axis of the spectrometer. © 1979.