1/f Noise in conducting Langmuir-Blodgett films of quasi-one-dimensional charge-transfer complexes

Abstract

The noise characteristics of conducting Langmuir-Blodgett films of charge-transfer complexes (C16H33-TCNQ)0.4(C17H35−DMTTF)0.6 (surface-active complex based on a 1.5: 1.0 mixture of heptadecyldimethyltetrathiafulvalene (C17H35−DMTTF) and hexadecyltetracyanoquinodimethane (C16H33-TCNQ)) are studied. It is demonstrated that the excess (with respect to the thermal noise) electrical noise whose spectrum is close to 1/f dominates in the frequency range 1–104 Hz. This noise has a bulk nature and arises owing to fluctuations of the film conductivity. The noise level is almost three orders of magnitude higher than the level predicted by the Hooge formula. A model that explains the film conductivity fluctuations by the superposition of relaxation processes of the on/off switching of conducting channels is proposed. In the framework of this model, a relationship that makes it possible to represent the level of the 1/f noise in terms of the parameters of a sample is derived. It is shown that the application of this relationship for the calculation of the 1/f noise magnitude in specific samples of conducting Langmuir-Blodgett films and TTF-TCNQ crystals yields results that are close to the experimental data.