Dependence of the pyroelectric response on internal stresses in ferroelectric thin films

Abstract

The role of internal stresses on the pyroelectric properties of ferroelectric thin films is analyzed theoretically via a thermodynamic model. The pyroelectric coefficient as a function of the misfit strain is calculated for ͑001͒ Ba 0.6 Sr 0.4 TiO 3 epitaxial thin films. It is shown that this property is highly dependent on the misfit strain. A very large pyroelectric response ͑0.65 C/cm 2 K͒ is theoretically predicted at a critical misfit strain ͑ϳϪ0.05%͒ corresponding to the ferroelectric to paraelectric phase transformation. The analysis shows that internal tensile stresses are particularly not desirable with significant degradation close to an order of magnitude in the pyroelectric response.

Impact of misfit relaxation and a-domain formation on the electrical properties of tetragonal PbZr0.4Ti0.6O3/PbZr0.2Ti0.8O3 thin film heterostructures: Experiment and theoretical approach

“…The stable equilibrium domain configuration can be determined using the relations (1)- (15). F has to be minimized in order to calculate the remnant polarization P r .…”

“…[44] Misfit dislocations which form at the interface are accompanied by local strains which affect both P r and ε r , [24,45,46] and give rise to threading dislocations. [15] These threading dislocations in turn have been only taken into account as a relaxation mechanism, but they also directly affect P r . [43,47] Overall, despite the simplicity of the approach, the variations of the experimental observations can be elucidated and the effect of a-domains can be highlighted through the adopted methodology.…”

“…Other properties like the pyroelectric effect are affected as well. [14][15][16] However these considerations only hold true for a very confined thickness range. If a critical thickness is exceeded during film growth, the film starts to relax by forming misfit and threading dislocations.…”

Electrothermal properties of perovskite ferroelectric films

“…Previous results from our group show that internal stresses in ferroelectric thin films could significantly deteriorate the functional properties of ferroelectric films and an optimum pyroelectric and electrocaloric response can be realized by tuning various experimental parameters to adjust the internal stresses [40,41]. For polycrystalline ferroelectric films produced by industry-standard deposition techniques such as sputtering or metal-organic solution deposition [42], internal stresses mainly come from the CTE mismatch between the film and the substrate and the self-strain of the paraelectric-ferroelectric transition.…”

Impact of in-plane anisotropic strains on the dielectric and pyroelectric properties of Ba0.7Sr0.3TiO3 thin films

“…One major advantage is that they can operate at room temperature, thereby eliminating the need for expensive cooling systems. [7][8][9][10] Moreover, the integration of hybrid arrays of ferroelectric thin films detectors with silicon readout integrated circuits can offer high-performance infrared imaging. BST thin films are also considered as the candidate materials for pyroelectric sensors because of their relatively large nonlinear pyroelectric response at room temperature, good reliability, good sensitivity, and low cost.…”