Thickness dependence of conduction currents in ultra thinevaporated polypropylene films

摘要

A ultra thin polypropylene film (thin PP film) was deposited on aglass substrate by the vacuum evaporation method. A thin PP filmdeposited on a glass substrate at room temperature was annealed for onehour in N₂. Thin PP films are about 60~1.50 A in thickness.Aluminum electrodes (2 mm square) were evaporated on both sides of athin PP film [evap.Al/Thin PP/evap.Al (Al/thin PP/Al)]. The conductioncurrent for a 150A-thick PP film was explained with Schottky conductionand a tunneling conduction for a 60 A-thick film. When the area of theupper electrode was reduced to 85% of the initial area by self-healingbreakdowns, the electrical field strength was about 7.5 MV/cm for the150 A-thick film, and 16 MV/cm for 60 A thick film. These show that thebreakdown strength of a thin film has the thickness dependence. In otherwords, it suggests the avalanche breakdown