Electric-field profile and thermal properties in substrate-supported dielectric films

Abstract

The transient pyroelectric response of a dielectric film on a substrate is used to determine both the electricfield profile across the film and its thermal properties. The response is a convolution of the field and temperature profile. A closed-form expression for the transient temperature profile is obtained for a generic model in terms of thermal parameters. This expression allows analysis of the pyroelectric response using an iterative procedure consisting of deconvolution and variation of thermal parameters. Tikhonov regularization is used in the deconvolution with a Honerkamp-Weese self-consistent regularization parameter. Simulations show that, at least in the cases tested, the electric-field profile, the thermal diffusivity and conductivity ͑and thus the heat capacity, which is their ratio͒, and the thermal resistance of the dielectric/substrate interface can be determined. Experiments on polyimide films adhered to substrates unambiguously reveal bound negative charge within a small depth of the free surface of virgin samples and also weaker, broader charge distributions injected from the substrate in samples under an applied voltage. The analysis resolves both sharp and broad features and gives thermal properties characteristic of the near-surface region, suggesting that the heat capacity may be significantly higher in this region than in the bulk.

Characterisation of the polarisation state of embedded piezoelectric transducers by thermal waves and thermal pulses

“…Figure 4 illustrates the mean temperature over a time period of 0.1 s. The analytical models start at the temperature maximum whereas the FEM model shows the increase of the temperature from room temperature to a maximum value since the laser pulse has a given time duration of 0.5 µs. The model of Bloß et al (2000) does not reach the maximum immediately but shows a slight increase of the temperature at the beginning due to the thermal mass of the electrode. At longer times, the temperature decreases exponentially to room temperature.…”

“…However, there is still a time shift between the signal maxima of the model and the experiment. One reason could be the thermal buffering effect of the top electrode (Bloß et al, 2000). It absorbs thermal energy during the short thermal pulse but only slowly transfers it to the piezoelectric since the heat transfer is limited by the piezoelectric's thermal diffusivity.…”

“…Another analytical approach is a one-dimensional transient heat transfer model introduced by Bloß et al (2000). It additionally considers the thermal mass of the electrode.…”

Thermal and acoustic pulse studies of space-charge profiles in electron-irradiated fluoroethylene propylene

“…The improvements brought by the present TP measurements [11] compared to the earlier LIMM measurements [4] are extended bandwidth and improved signal-to-noise ratio (SNR) of the measurement. The maximal modulation frequency used for the LIMM spectra in [4] was f max = 100 kHz.…”

Distribution of space charges in luminescent conjugated polymers

“…Accordingly, small aberrations in the data, which are inevitably effected by measurement errors, will result in large or even unbounded errors of the reconstructed distribution function r(z) . In order to solve such ill‐posed inverse problems special mathematical methods, eg regularisation methods, are necessary 13–15…”