RESISTANCE CHARACTERISTICS OF CONDUCTING POLYMER-FILMS USED IN GAS SENSORS

The measurement of the resistance of thin films of conducting polymer deposited between microelectrodes is discussed. Attention is drawn to the severity of self-heating effects which may perturb the measurement unless the measuring power is kept low. The conduction mechanism is n onohmic at frequencies below 1 MHz, but considerably more ohmic at fre quencies of tens of MHz. Noise measurements show that the passage of d .c. current generates a high level of excess noise with a 1/f characte ristic. This result, taken with the high-frequency data, is consistent with a model picture of a film conductivity which is dominated by int ergranular contact at low frequencies although electrode contact effec ts cannot be completely excluded. Due to the 1/f noise, accurate resis tance measurements are best made using a.o. techniques. (C) 1997 Elsev ier Science S.A.