Photothermal Radiometry Applied to Angstrom's Method for Measuring the Thermal Diffusivity of CVD Diamond
A Feldman, N M. Balzaretti
The longitudinal thermal diffusivity of three thin long bars of chemical vapor deposited diamond has been measured by a modification of the one dimensional Angstrom's method that employs photothermal radiometry to detect the thermal profile. The geometry permits us to use a linear least squares fitting procedure on both the temperature magnitude and phase as a function of position, provided that the condition for ignoring end effects is fulfilled. Values of diffusivity obtained with the two types of data showed no significant difference. The diffusivities obtained agree reasonably well with the mean values calculated form measurements made by several other laboratories on the same specimens. The heat source was the beam of an argon-ion laser focused onto the specimen surface either with a cylindrical lens to form a line focus or with a spherical lens to form a point focus. The differences in diffusivities obtained when a line source was used and when a point source was used were not statistically significant. The point source was preferable because the optical configuration of the experiment was simpler and larger signals were obtained experimentally. A theoretical calculation indicates that the one dimensional treatment is valid regardless of the detailed shape of the heating source provided heating is localized and the measurements are made sufficiently far from the heat source.
and Balzaretti, N.
Photothermal Radiometry Applied to Angstrom's Method for Measuring the Thermal Diffusivity of CVD Diamond, Journal of Chemical Vapor Deposition
(Accessed September 24, 2023)