Improved approach for determining thin layer thermal conductivity using the 3ω method. Application to porous Si thermal conductivity in the temperature range 77-300 K

An improved approach for determining thermal conductivity using the 3 omega method was used to determine anisotropic porous Si thermal conductivity in the temperature range 77-300 K. In this approach, thermal conductivity is extracted from experimental data of the third harmonic of the voltage (3 omega) as a function of frequency, combined with consequent FEM simulations. The advantage is that within this approach the finite thickness of the sample and the heater are taken into account so that the corresponding errors introduced in thermal conductivity values when using Cahill's simplified analytical formula are eliminated. The developed method constitutes a useful tool for measuring the thermal conductivity of samples with unknown thermal properties. The thermal conductivity measurements with the 3. method are discussed and compared with those obtained using the well-established dc method.