Electrical characteristics of thermally evaporated stearic acid films

The d.c. dielectric breakdown properties of thermally deposited thin films of stearic acid (CH3, (CH2)16 COOH) have been investigated. The voltage vs. time (V-t) and current vs. voltage (I-V) characteristics were studied on test capacitors consisting of aluminum-stearic acid-aluminum. The film thickness (d) dependence studies of the dc breakdown field of these capacitors have been carried out in the thickness range 200-2000A. Electric breakdown processes in thin film insulators are discussed. Interpretation of the results are greatly facilitated by using specimens which were self-healed to eliminate most of the weak spots in the films.

The experimental results are analyzed in the light of Forlani and Minnaja’s theory of ionization avalanche breakdown. The destruction of the capacitor after the breakdown has been studied using an optical microscope at constant magnification. Various types of rupture patterns are observed as a result of dielectric breakdown of these insulating films.