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A new optical technique for the determination of spatial distributions of the thickness and the optical constants of thin films is proposed. This technique is simple and nondestructive involving mainly an ellipsometer and a coherent light source, and no contact to the thin-film samples is required. A theoretical estimation indicates that this technique may provide a spatial resolution close to the diffraction-limited resolution under certain conditions. Possible applications of this technique are also discussed.

The liquid motion normally observed in electrically stressed dielectric liquids is mainly caused by two mechanisms: (a) the Coulombic force due to the interaction of the space charge with the field, and (b) the electromechanical force created by the field resulting from the spatial variation of the dielectric constant due to the variation of temperature from domain to domain and from time to time in the liquid. The direction of such a liquid motion depends on which of these two mechanisms is dominant. The schlieren images sometimes observed in liquids under applied fields show mainly the change of the already existing temperature gradients in the liquids, and this change is due to the liquid motion caused by either mechanisms (a) or (b) or both. It is concluded that the schlieren images are directly governed by the temperature distribution in the liquid and have no direct bearing on the formation and distribution of space charges.

On the principle that the spatial distribution of the refractive index produced by a small applied temperature difference is changed due to an electromechanical force created by the field resulting from the spatial variation of the dielectric constant, the electric field distributions in a dielectric system can be determined using the schlieren method. Some experimental results for benzene and n-hexane between two spherical electrodes obtained with this method show the essential features predicted from the space charge effects. This method can be used to study electric field and space charge distributions under both steady and transient conditions.

New laser interferometry has been developed for determination of thickness distributions of low absorbing films on transparent substrates. This technique is suitable for films with either a gradual change or a step change in thickness. With this technique we have obtained fringe patterns showing the 2-D thickness distribution of Se films. This technique is simple and nondestructive without involving computations for films with low absorption and substrates transparent to the laser beam.