2. 3ω method
• The 3ω method is widely used to measure thermal properties of both bulk
materials and thin films after it was first introduced in 1990 by Cahill
• The metallic strip serves as both an electrical heater and a temperature sensor
• When measuring the thermal conductivity of an electrically conductive material or
a semi-conducting material, an additional electrical insulation layer is needed
between the electrical heater/sensor and thin film. Depending on the width of the
heater, both the cross-plane and the in-plane thermal conductivity of thin films
can be measured using the 3ω method
• The calculated error of 3ω measurement due to radiation is less than 2% even at a
high temperature of 1000 K .
4. Fig2. Schematic of the cross-plane and the in-plane thermal conductivity measurement
using the 3ω method. For cross-plane thermal conductivity measurement, the heater width
should be relatively large compared to thin film thickness in order to satisfy the assumption
that the heat conduction is one-dimensional across the thin film. For the in-plane thermal
conductivity measurement, narrower-width heater is used so that the in-plane thermal
conductivity can be deduced through heat spreading in the thin film.
