Pyroelectric calorimeter for photothermal studies of thin films and adsorbates

Abstract

A pyroelectric calorimeter for studies of radiation induced thermal transients in thin films and at surfaces is described. The signal generation and detection process, as well as design criteria are briefly reviewed. Detailed data are presented whereby our design, which has found extensive utility, can be fabricated. This device is compatible with standard Inficon quartz microbalance hardware and provides a sensitivity of several nanojoules at a time resolution of <100 ns over a wide temperature and pressure range.

Invited Review Article: Photopyroelectric calorimeter for the simultaneous thermal, optical, and structural characterization of samples over phase transitions

“…Here, the pyroelectric parameters have been assumed homogeneous and temperature independent as normally justified under ordinary experimental conditions. 41 Therefore, a current…”

“…Moreover, such materials must be characterized also by a relatively large value of the Curie temperature. 41 In fact, operation of detectors sufficiently below such a temperature implies a very weak temperature dependence of the pyroelectric coefficient, which is advisable when performing measurements as a function of temperature as in case of investigations over phase transitions. Among others, lithium tantalate (LaTiO 3 ) is one of the most commonly adopted pyroelectric material due its relatively large figure of merit (∼15) and high value of the Curie temperature (∼600 • C).…”

“…On the other hand, β-polyvinylidene (β-PVDF), because of its relatively low cost, is also employed even if it has a lower figure of merit (∼9.7). The main limitation of β-PVDF is represented by the low value of its Curie temperature (∼130 • C) which restricts its operating temperature range below 100 • C. 41 As far as the PPE calorimetry is concerned, the piezoelectric contribution to the PPE signal must be reduced as much as possible. In fact, such a contribution is in general expressed by complicated terms 42 involving a combination of both thermal and elastic parameters.…”

Pyroelectric polymer electrets

“…Later, regularization was also used by Wubbenhorst and Wiinsche and Bloss et al [115,116]. Physical insight into the reason for a nonuniform resolution was gained by Leal-Ferreira [ l l v and Coufal et al [118], who proposed scaling transformations in order to obtain an approximation of the desired charge or polarization profiles. These ideas were further developed by Ploss et al [119], and by Bauer [120].…”

“…Polarization gradients were observed near the electrode-coated surfaces. Investigations of these depolarized near-surface layers were reported by Coufal et al [118] and by DeReggi and Broadhurst [lo81 who used the thermal-pulse technique, as well as by Ploss et al [119] and Ploss and Bianzano [129], who employed the thermal wave techmque. It was found that with increasing film thickness, the homogeneity of the polarization decreased [118].…”