Photoacoustic thermal characterization of low thermal diffusivity thin films

Thin films with ultra-low thermal expansion.

Ultra-low coefficient of thermal expansion (CTE) is an elusive property, and narrow temperature ranges of operation and poor mechanical properties limit the use of conventional materials with low CTE. We structured a periodic micro-array of bi-metallic cells to demonstrate ultra-low effective CTE with a wide temperature range. These engineered tunable CTE thin film can be applied to minimize th...

Accurate measurements of the thermal diffusivity of thin films and thin filaments using lock-in thermography

In lock-in thermography the thermal diffusivity can be obtained from the slope of the linear relation between the phase of the surface temperature and the distance to the heating spot. However, in the case of thin samples, the linearity is not found. In this work we identify heat conduction to the surrounding gas as the mechanism responsible for the lost of linearity. Accordingly accurate measu...

Thermal Diffusivity Measurement of Refrigerant 22 at Low Pressures Using the Photoacoustic Effect

In-Situ Testing of the Thermal Diffusivity of Polysilicon Thin Films

This paper presents an intuitive yet effective in-situ thermal diffusivity testing structure and testing method. The structure consists of two doubly clamped beams with the same width and thickness but different lengths. When the electric current is applied through two terminals of one beam, the beam serves as thermal resistor and the resistance R(t) varies as temperature rises. A delicate ther...

Thermal fluctuations of thin liquid films

A surprising lowering of the surface energy of liquid surfaces was recently found in x-ray scattering experiments which enhances thermal fluctuations of fluid interfaces at microscopic scales and calls for a re-examination of small-scale interfacial processes. This reduction was predicted for microscopic undulations below a few nm by density functional theory taking into account the long-range ...