Conduction and breakdown characteristics of thermally evaporated stearic acid films

Thin films of organic fatty acids such as stearic acid (C17H35COOH), deposited by Langmuir-Blodgett technique have been widely investigated and the progress reviewed (1,2). However, very little is known about the conduction and breakdown characteristics of thin films of stearic acid deposited by thermal evaporation in vacuum. Agarwal and Mitsuhashi (3) have studied the high field conduction characteristics using a planar electrode geometry and Kasilingam et al (4,5) have reported the conduction and breakdown characteristics on sandwich electrode geometry. In these studies (3–5) the film deposition parameters were; pressure in the 10⁻⁵ to 10⁻⁶ Torr range and film deposition rate of −10Å/s. Moreover, no attempt was made to avoid the formation of an Al2O3 film on the lower aluminum electrode prior to the deposition of the stearic acid film. In this paper we have reported breakdown behavior and dielectric nature of stearic acid films deposited at much lower pressure (∼10⁻⁸ Torr) and at a much lower film deposition rate). We have also used proper masking and a dual source evaporator to deposit the lower Al electrode and the stearic acid film without disturbing the vacuum so that no oxide layer is formed between the lower electrode and the stearic acid film. Sandwich structures have capacitance/area ranging from 0.027 to 0.033 f/m², the dielectric constant between 1.45 and 2.04, and DC breakdown field strength ranging from 9.27 × 10⁷ to 7.63 × 10⁸ V/m.