Noise and Electro-Ultrasonic Spectroscopy of Polymer Based Conducting Layers

We have studied the properties of polymer based thick film layers by noise and electro-ultrasonic spectroscopy. The low frequency noise spectral density is 1/fa type and it is proportional to the square of electric current. The frequency factor a is very near to 1. From the noise measurements we have estimated the number of point contacts between conducting grains in the measured samples. We have applied new principle for non-destructive testing of conducting solids - Electro-Ultrasonic Spectroscopy. The ultrasonic signal of frequency fU changes the contact area between conducting grains and then resistance is modulated by the frequency of ultrasonic excitation. An intermodulation voltage is created on the structure. It depends on the value of AC current varying with frequency fE and on the ultrasonic excited resistance change DeltaR varying with frequency fU. The intermodulation component of frequency fm = fE - fU varies linearly with electric excitation and quadratic dependence on ultrasonic excitation was observed. Simultaneous measurement of electrical noise and amplitude of intermodulation signal shows that intermodulation signal amplitude is correlated with the noise spectral density.