Influence Of Piezoelectric Effect Research Articles

Competitive behavior between the piezoelectric and piezoresistive effects in monolayer WS2 photodetector

The strain induced piezoelectric and piezoresistive effects have been regarded as promising methods to regulate the photoelectric properties of two-dimensional transition metal dichalcogenides. However, the distinction between the influence of piezoelectric and piezoresistive effects on devices is ambiguous. Here, piezo-phototronic photodetectors based on monolayer WS2 were fabricated to investigate the competitive behavior of the piezoelectric and piezoresistive effects. We have shown that the piezoresistive effect dominates the photocurrent enhancement through narrowing the bandgap under small strain. With increasing strain, the influence of piezoelectric effect became more and more obvious, and it dominated the photo-induced carrier transport behavior through polarization charges accumulated at the metal–semiconductor contact interface when the strain exceeded 0.78%. Under the strain condition, the modulation of strain on photocurrent reached as high as 1400%.

The influence of piezoelectric effect on the heterogeneous photocatalytic hydrogen production of strontium titanate nanoparticles

Combining photocatalysis with the other physical-field is an efficient way to improve the performance of photocatalysis. The piezoelectric effect on the heterogeneous photocatalytic hydrogen production of SrTiO3 (STO) nanoparticles was studied in this paper. It was found that the piezoelectric effect generated by the ultrasonic cavitation (sonophotocatalysis) had a profound influence on heterogeneous photocatalytic hydrogen production with or without sacrificial agents. Notably, the sonophotocatalytic hydrogen production of STO was related to the viscosity of sacrificial agents and the position of the ultrasonic vibrators. The mechanism of the performance changes by sonophotocatalysis was investigated by in-situ deposition Pt nanoparticles, which were found to aggregate obviously on STO nanoparticles' surface. Thus, ultrasonic cavitation would build a piezoelectric potential on the local surface of STO that would inhibit photo-generated carriers migrating to the surface.

Analysis of Reflection Phenomena in a Fiber Reinforced Piezo-Thermoelastic Half Space with Diffusion and Two-Temperature

Present work is concerned with the analysis of transient wave phenomena in a piezo-thermoelastic medium with diffusion, fiber reinforcement and two-temperature, when an elastic wave is made incident obliquely at the traction free plane boundary of the considered medium. The formulation is applied under the purview of generalized theory of thermoelasticity with one relaxation time. The problem is solved analytically and it is found that there exists four coupled quasi waves: qp (quasi-p ), qMD (quasi mass diffusion), qT (quasi thermal) and qSV (quasi-SV ) waves propagating with different speeds in a two-dimensional model of the solid. The amplitude ratios, phase velocities and energy ratios for the reflected waves are derived and the numerical computations have been carried out with the help of MATLAB programming. Effect of presence of diffusion is analyzed theoretically, numerically and graphically. The number of reflected waves reduce to three in the absence of diffusion as qMD wave will disappear in that case which is physically admissible. Influence of piezoelectric effect, two temperature and anisotropy is discussed on different characteristics of reflected waves such as phase velocity and reflection coefficients. It has been verified that there is no dissipation of energy at the boundary surface during reflection. Thus, the energy conservation law holds at the surface. Finally, all the reflection coefficients are represented graphically through 3D plots to estimate and highlight the effects of frequency and angle of incidence.

Piezoelectric effects on the resonance frequencies of boron nitride nanosheets

By using molecular dynamics (MD) simulations, we find in this work that due to the piezoelectric characteristic of boron nitride (BN) nanosheets their resonance frequencies can be efficiently tuned by applying an external electric field. This finding suggests that BN nanosheet can be treated as a good building block for designing novel piezoelectrically tunable two-dimensional nanoresonators. As BN nanosheets possess an inversely stacked structure, the applied electric field has different effects on the resonance frequency of BN nanosheets with odd and even layers. The influence of piezoelectric effect on the vibration behaviours observed in MD simulations is found to significantly deviate from the prediction of the conventional Euler–Bernoulli beam model (EBM), since the EBM cannot account for the weak van der Waals interaction between neighbouring layers in BN nanosheets. To take into account the interlayer interaction in the mathematical modelling of the piezoelectric effect on the vibration of BN nanosheets, we propose here a novel multiple beam model (MBM), which can account for both interlayer stretching and shearing deformations. The MBM result is found to be in a good agreement with the MD result without any additional parameters fitting, which indicates that the present MBM can be treated as a more precise theoretical model in the future study of the vibration properties of BN nanosheets.

Measurement of Flexoelectric Effect in Lead Zirconate Titanate Ceramics

Lead zirconate titanate (PZT) ceramics is usually used as a piezoelectric material. However it has characteristics of not only piezoelectricity but also flexoelectricity. Piezoelectricity is a phenomenon that electric polarization is induced by strain, and flexoelectricity is the one that the polarization is induced by strain gradient. In this study, flexoelectricity in poled soft PZT ceramics is measured. In order to eliminate influence of piezoelectricity, PZT ceramic thin plates are subjected pure bending using four-point bending experimental mechanism. Strain gradient along the direction of thickness in the plate is caused by the bending motion. Electric charge between two electrodes which is set on the center of the plate surface is measured under quasi-static sinusoidal load. Even though the polarization for piezoelectric effect is eliminated by the experimental setup, the influence of piezoelectric effect still remains since polarization by piezoelectricity is much larger than the one by flexoelectricity. So the influence of piezoelectricity is eliminated using qualitative difference between piezoelectricity and flexoelectricity for poling direction. Eventually, flexoelectric coefficient of the order of 10-5 C/m is measured.

Theoretical study of InAs/GaAs quantum dots grown on [11k] substrates in the presence of a magnetic field

Eight-band k.p theory including strain and piezoelectric effects are employed to calculate the strain distribution and electron and hole energy levels of InAs/GaAs quantum dots grown on [11k] substrates in the presence of an external magnetic field. Height of the dot determines how the increasing of k influences isotropic part of the strain tensor while biaxial part of the strain tensor is always reduced with increasing k. Because of the reduced symmetry of high index surfaces, influence of piezoelectric effect on the electronic structure becomes more dominant with increasing k. Electron energy levels are influenced by the isotropic part of the strain compared to the hole energy levels, where strong heavy hole–light-hole mixing is observed. For the dots grown on the [11k] surfaces magnetic field has smaller influence on the electron and hole energy levels as compared to the referent case.

Intensity factors for some common piezoelectric fracture mechanics specimens with conducting cracks or electrodes

This paper provides the stress and electric field intensity factors for some common piezoelectric fracture mechanics specimens with electrically conducting cracks or electrodes. Firstly, the solution for a vertical crack with electrically conducting boundary condition on its surfaces is established for a piezoelectric strip under combining mechanical and electrical loads. Then, a surface-cracked strip, a double edge cracked strip, and a center-cracked strip, subjected to uniform stress and electric field loads simultaneously, are investigated. Also investigated is an edge-cracked strip under pure bending and uniform electric field loads. The influence of piezoelectric effect on the stress and electric field intensity factors is found to be insignificant, suggesting that the stress intensity factors of piezoelectric materials under mechanical loads can be obtained in a same way as ordinary brittle solids, and the electric field intensity factors of piezoelectric materials under electric field loads can be obtained in a same way as ordinary dielectrics. However, the results show that the mechanical loads can produce electric field intensity factors, and the electric field loads can produce stress intensity factors in piezoelectric materials, due to the fact that the medium has finite size.

Interaction of a Screw Dislocation with an Interfacial Crack in Two Dissimilar Piezoelectric Layers

A screw dislocation interacting with a semi-infinite interfacial crack in two dissimilar piezoelectric layers is studied. The complex variable method and the conformal mapping technique are employed to obtain the solution of the problem. The stress and electric displacement intensity factors are given explicitly. We find that the stress and electric displacement intensity factors depend on the effective electro-elastic material constants. Numerical example shows that the influence of piezoelectric effect on the crack tip shielding is significant.

Screw dislocation in two dissimilar piezoelectric layers

AbstractThe elastic and electrical fields produced by a straight screw dislocation in two dissimilar piezoelectric layers are derived through the use of conformal mapping technique, where the solution for a semi‐infinite piezoelectric bimaterial is used as a base. The expression for the image force acting on the dislocation is given explicitly. The equilibrium position of the dislocation is further determined by letting the image force be equal to zero. In the case where one of the two layers is pure elastic, the numerical results for the image force are provided to illustrate the influence of piezoelectric effect on the behavior of the dislocation. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Soft modes and phonon interactions in studied by neutron scattering

The low frequency lattice dynamics and its relationship to the second order paraelectric-to-ferroelectric transition in Sn2P2S6 is studied. The dispersion branches of the acoustic and lowest lying optical phonons in the a*-c* plane have been obtained in the ferroelectric phase, for x-polarized phonons. Close to the phase transition a considerable softening is found for the lowest optical mode (Px), comparable to the behaviour observed in previous Raman investigations. As found previously in Sn2P2Se6, a strong coupling between the TO(Px) and TA(uxz) phonons is observed, although, apparently, not strong enough to lead to an incommensurate phase. The soft TO(Px) mode at the zone center is observed. The temperature dependence of its frequency and damping shows that the transition is not entirely displacive. At low temperatures an unusual apparent negative LO-TO splitting is observed which is shown to arise from the coupling of the x-polarized soft mode to the nearby z-polarized optical phonon. For comparison, the soft TO(Px) dispersion in the a*-b* plane is measured in both the paraelectric and ferroelectric phases. Consistent frequency changes and LO-TO splitting are observed, revealing a significant interaction between the TA(uyx) and LA(uxx) acoustics branches and the TO and LO soft optic branches, respectively. In contrast, the nearby y-polarized optic branch shows almost no temperature dependence. Finally, the influence of piezoelectric effects on the limiting acoustic slopes in the ferroelectric phase is discussed.

Influence of piezoelectric effect on photorefractive gratings in electro-optic crystals

The general equations applicable to the description of different photorefractive effects in electro-optic crystals, taking into account their piezoelectric properties, have been considered in this paper. The photorefractive gratings formed by plane light waves slowly changing in time in boundless piezoelectric media have been analyzed in detail. The influence of piezoelectric properties of the crytals on the effective static dielectric constant at different orientations of the photorefractive grating vector has also been considered.