Traveling wave method for measurement of thermal conductivity of thin films

We present here the design of a novel and simple setup for measuring the thermal conductivity of thin films. This method is based on the well known principle of phase lag of a traveling thermal wave. In the present setup, the traveling thermal wave is generated in the thin film by irradiating its one edge by an infrared laser. The phase lag (Delta theta) between the excitation wave and the resulting thermal wave, at a variable distance d from the edge of the sample, is determined by measuring the deflection of another ''probe-laser.'' The thermal diffusivity is then directly calculated from the slope of the plot between Delta theta and d. This method offers an accuracy of better than +/-5%. (C) 1997 American Institute of Physics. [S0034-6748(97)01811-X].