Current Noise in Pyrolyzed Polyacrylonitrile

Current noise measurements of the organic semiconductor polyacrylonitrile pyrolyzed in nitrogen at temperatures from 550° to 900°C reveal conductivity fluctuations similar to those attributed to carrier fluctuations in inorganic semiconductors. The current noise spectra exhibit characteristic time constants of 10−2, 3×10−4, and 5×10−5 sec which are independent of pyrolysis temperature and are tentatively associated with the molecular structure leading to conductivity. The observed noise magnitude suggests the existence of a large number of independent sub-volumes which increase in size with treatment temperature. Samples pyrolyzed above 700°C exhibit 1/f noise that may be indicative of a different molecular structure.