A thermal wave of high modulation frequency
is generated at the surface of the thin film. Due to the
high frequency of the temperature modulation, the
penetration depth into the film is limited to the film
thickness. This isolates the thin film thermically from the
substrate and allows one to measure changes in the heat
capacity and the perpendicular thermal conductance of the
thin film. An ultra-thin platinum film on the surface of the
film serves at the same time as heater and thermometer. In
some cases the resistance of the thin film itself may be
used instead. |