Application of the three omega method for the thermal conductivity measurement of polyaniline

The three omega method has proven to provide accurate and reliable measurements of thermal conductivity of thin films and other materials. However, if the films are soft and conductive, conventional methodologies to prepare samples for the measurement technique are challenging and often unachievable. Various modifications to the sample preparation to employ this technique for soft conducting films are reported in this paper including the use of shadow masks for metal heater deposition and a process for preparation of low temperature insulating films required between film and heater. In this work, thick (similar to 5 mu m) and ultrathin (similar to 110 nm) films of polyaniline as well as a thin (similar to 300 nm) film of low temperature plasma enhanced chemical vapor deposited SiO(2) as a function of temperature were measured. Though not considered a soft material, the silicon dioxide film was utilized for comparison with previous data. Results indicate that the SiO(2) film exhibits a thermal conductivity slightly lower than others' data [S. M. Lee and D. G. Cahill, J. Appl. Phys. 81, 2590 (1997); H. Yan , Chem. Lett. 2000, 392; H. Yan , Anal. Calorim. 69, 881 (2002); J. E. de Albuquerque , Rev. Sci. Instrum. 74, 306 (2003)], which is likely due to the low temperature processing conditions that results in additional disorder in the film. The polyaniline films exhibit an increase in thermal conductivity with temperature, which is largely due to increasing heat capacity. The thick film thermal conductivity is many times the value corresponding to the thin film, which is likely due to significant phonon boundary scattering present in the ultrathin film. (c) 2007 American Institute of Physics.