COMPLEX IMPEDANCE OF COPPER-FILMS

Thin (approximately 1500 A) evaporated bismuth films having initial resistance values between 30 and 150 OMEGA /square have been shown previously to have a structure-determined impedance in the infrared region between 2 and 15 mu m. The electric circuit representing this impedance was derived from a combination of resistance and infrared transmission measurements. For evaporated copper films of similar thickness and for the same infrared region an impedance has been determined using infrared transmission and reflection measurements instead. The most useful circuit obtained is similar to the one derived for bismuth: a capacitance in series with a parallel capacitance and resistance. For copper films having a range of initial values of resistance from 30 to 260 OMEGA /square the equivalent circuits together with R- and C-parameter values are determined and presented.