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We study temperature effects in piezoelectric semiconductor thin films through pyroelectric and thermoelastic as well as piezoelectric couplings. Two-dimensional equations based on the macroscopic theory of piezoelectric semiconductors for extensional deformations of the films are used. A p-type ZnO film with an in-plane c-axis is analyzed. It is shown through a linear and theoretical analysis that a local temperature change produces a pair of a potential barrier and a well in the film. A nonlinear numerical analysis is then performed when a voltage is also applied, showing that the potential barrier blocks the in-plane motion of the holes and thus affects the current density distribution. The effects of various physical and geometric parameters are examined. The results obtained provide the theoretical foundation for thermally manipulating currents in piezoelectric semiconductor films for piezotronic applications. [ABSTRACT FROM AUTHOR]

We study electromechanical fields in a thin composite beam of a flexoelectric semiconductor layer sandwiched between two piezomagnetic dielectric layers induced by an applied magnetic field. The macroscopic theory of piezomagnetics and flexoelectric semiconductors is used. A one-dimensional model is derived from the three-dimensional equations. Responses under static and time-harmonic magnetic fields are obtained analytically from the model. Results show magnetically induced bending deformation and redistribution or motion of charge carriers toward the top and bottom of the beam through combined piezomagnetic and flexoelectric couplings. A coupling coefficient depending on the physical and geometric parameters of the structure is introduced to characterize the strength of the effect. The coupling coefficient assumes a maximum for a specific thickness ratio of the piezomagnetic and semiconductor layers. The results are fundamental to the emerging field of flexoelectronics when magnetic fields are involved. [ABSTRACT FROM AUTHOR]

We study the interaction between mechanical fields and the motion of charge carriers in a composite beam of flexoelectric (nonpiezoelectric) and semiconductor layers. The macroscopic theory of flexoelectricity and the drift-diffusion theory of semiconduction are used. They are coupled by doping and mobile charges in Gauss's equation of electrostatics. A one-dimensional electromechanical model is established for the bending of the beam. Solutions from the model show that bending of the beam induces redistribution of charge carriers through the electric field produced by flexoelectric coupling. This provides a new means for constructing electromechanical semiconductor devices and extends piezotronic devices. [ABSTRACT FROM AUTHOR]

We study the electrical behavior of a piezoelectric semiconductor fiber under local extensional or compressive stress and an applied voltage. A numerical analysis based on a one-dimensional phenomenological model is performed. The current-voltage relation is obtained. It is found that when the applied voltage is below a stress-dependent critical value, no current can flow through the fiber in either direction. When the voltage is above the critical voltage, currents can flow in one direction but not the other. When the voltage is above a second critical value, currents can flow in both directions. Thus, the local stress acts like a switch, which can turn the currents on and off in one or both directions. This provides a basic means for mechanically manipulating the electrical behavior of piezoelectric semiconductor fibers and thus serves as a fundamental element of piezotronics. [ABSTRACT FROM AUTHOR]

We study extensional vibrations of a ZnO piezoelectric semiconductor fiber driven by a time-harmonic end force. A theoretical analysis is performed using a one-dimensional model based on the phenomenological theory of piezoelectric semiconductors consisting of the equations of piezoelectricity coupled to the continuity equation of electrons. A series of resonance frequencies are identified. It is found that these frequencies are lower than those of the corresponding piezoelectric dielectric fiber because the mobile charges in the semiconductor screen the effective polarization charges and thus weaken the piezoelectric stiffening effect. Various electromechanical fields at resonances are calculated and examined. Numerical results show that the effective surface polarization charge plays a more dominant role than the effective body polarization charge. The mobile charges can screen the body polarization charges greatly, but not the surface polarization charges. [ABSTRACT FROM AUTHOR]

We study the extension of a composite fiber of piezoelectric dielectrics and nonpiezoelectric semiconductors. A theoretical analysis is performed using a one-dimensional model. It is shown that mechanical loads cause redistribution of mobile charges in such a composite fiber. Thus, the composite fiber exhibits piezotronic couplings like a homogeneous piezoelectric semiconducting fiber. The couplings are a product property of the composite, enabling the design of piezotronics devices beyond materials with direct piezotronics couplings. The basic behavior of the composite fiber and the effects of various parameters on piezotronic couplings are calculated and examined. It is observed that piezotronic couplings in these fibers are sensitive to material and geometric parameters and can be optimized through design. [ABSTRACT FROM AUTHOR]

We study transient effects in AT-cut quartz plate thickness-shear mode acoustic wave resonators. Mindlin's equations for thin crystal plates are employed. Based on the relatively slow evolution of the vibration amplitude compared to the high-frequency thickness-shear vibration, a first-order differential equation governing the amplitude evolution is obtained. The equation allows simple and accurate solutions for transient processes in quartz resonators. A few numerical examples of resonator startup and turning off are given. The equation can be applied to other transient processes in crystal resonators such as driving voltage fluctuations and generalized to resonator-based acoustic wave sensors. [ABSTRACT FROM AUTHOR]

We study the propagation of coupled acoustic and electromagnetic waves in a piezoelectric plate waveguide embedded in two half-spaces of another dielectric material. It is shown that certain waves are guided electromagnetically but not so acoustically and that these waves are effectively damped waves with acoustic leakage of energy. An estimate of the acoustic radiation damping is given. [ABSTRACT FROM AUTHOR]