ICT2014 Abstracts

The Pulse Transient Hot Strip (PTHS) technique has been adapted for slab sample geometry to be able to determine the thermal conductivity and thermal diffusivity of anisotropic thin film materials (< 50 µm), deposited on thin substrates (i.e. wafers). An advantage of this technique is that it provides a well-controlled thermal probing depth, making it possible to thermally probe a predetermined depth of the sample layer and thereby avoid the influence from underlying material(s).

A micro-sized metal strip sensor was deposited on the sample surface by e-beam evaporation, and thereafter probed using micro-manipulators. A series of periodic square-shaped current pulses were fed to the strip sensor via a pulse generator in an AC-coupled network, and the subsequent average temperature increase of the strip sensor was recorded using a low-pass filter and a nano-voltmeter. The recorded data was thereafter fitted to an analytical thermal diffusion model, from which the anisotropic thermal transport properties could be extracted. To verify the technique measurements were performed on crystalline quartz, using a thermal probing depth of only about 30 µm. Along the perpendicular (parallel) direction to the z-, i.e. optic axis, a thermal conductivity of 6.48 (11.4) W/mK, and a thermal diffusivity of 3.62 (6.52) mm²/s, were obtained which are in line with corresponding literature values for bulk crystalline quartz. To demonstrate that the technique can be used to study a wide range of materials of different thermal conductivity, measurements were performed on samples such as fused quartz, gallium arsenide, benzocyclobutene, and sapphire. Finally, an extension of the technique to also be able to study nm-thick sample layers is discussed.