Some half-space problems of cubic piezoelectric materials

Half-space problems of a cubic piezoelectric material subjected to anti-plane deformation and in-plane electric field are studied. A general solution in terms of the integration of the boundary data prescribed over the surface of the semi-infinite domain is derived. Based on the general solution, the problem of a concentrated line force acting on the surface is treated and ensuing electromechanical response is determined. The solution to the problem of a screw dislocation in the half-space is also obtained, and the result is exploited to study a sub-surface crack problem by simulating the crack as a continuous distribution of dislocations.     

The nonlinear analysis of elastic wave of piezoelectric crystal plate with perturbation method

When investigating or designing acoustic wave sensors, the behavior of piezoelectric devices is supposed to be linear. However, if the sensors are subjected to a strong elastic field, the amplitude of the elastic strain induced in the piezoelectric material is so large that the nonlinearity, which affects the stability and performance of the piezoelectric sensors, can no longer be ignored. In this paper, we perform a theoretical analysis on nonlinear anti-symmetric thickness vibration of thin-film acoustic wave resonators made from quartz. Using Green’s identity, under the usual approximation of neglecting higher time harmonics, a perturbation analysis is performed from which the resonator frequency–amplitude (A–F) relation is obtained. Numerical calculations are made. Furthermore, the validity of the method is examined.     

An asymptotic model of a multimaterial with a thin piezoeletric interphase

We study the electromechanical behavior of a multimaterial constituted by a linear piezoelectric transversely isotropic plate-like body with high rigidity embedded between two generic three-dimensional piezoelectric bodies by means of the asymptotic expansion method. After defining a small real dimensionless parameter ε, which will tend to zero, we characterize the limit model and the associated limit problem. Moreover, we identify the non-classical electromechanical transmission conditions between the two three-dimensional bodies.     

光电经纬仪主镜面型误差主动补偿技术研究

光电经纬仪俯仰动作时,引起主镜的面型误差,从而影响整个光学系统的准确度,以往主镜支撑结构采用被动式补偿方式,来保证实际面型最大误差在设计指标之内.本文基于压电陶瓷主动面型补偿技术,通过对俯仰变化引起面型误差曲线的实时修正,来主动控制主镜装调和动作引起的面型误差.使用光机系统联合仿真方法,拟合主镜面型误差,然后采用压电陶瓷的主动补偿技术修正面型误差,能够使原主镜峰值下降到66.9 nm,均方根最大值下降到12.9 nm,满足15.82 nm的均方根要求.基于压电陶瓷的主动面型补偿技术不仅可以很好地实时补偿主镜的动态面型误差,提高光学系统的像质清晰度和视轴稳定性,对大口径高准确度主镜系统的装调与动态检测有重要的意义.     

铁电微型传感器和执行器制作技术

采用表面微细加工技术制作了铁电微型传感器和执行器。其技术特点是将铁电薄膜制备和加工工艺与半导体集成电路工艺相结合。其技术难点有：平面化、多晶硅的内应力控制，悬空结构与基片粘连及各层薄膜制备工艺间的兼容性等。本文提出了解决方法。     

Observation of the pyroelectric effect in strained piezoelectric InGaAs/GaAs quantum-wells grown on (111) GaAs substrates

We investigated the temperature dependence of the piezoelectric constant e₁₄, i.e. the pyroelectric effect, of various strained InGaAs/GaAs single- and multi-quantum wells embedded in p-i-n structures grown on (111)B GaAs substrates and diodes made from these structures. Both photoreflectance spectroscopy and differential photocurrent spectroscopy were applied to obtain e₁₄ over the temperature range 11-300 K. The values of e₁₄ for In_xGa_1−xAs quantum well layers with x=0.12-0.21 were observed to increase with temperature, which is contrary to the expected dependence, and the strain-induced components of the pyroelectric coefficients were quantitatively determined. The dependence of the pyroelectric coefficient on In fraction is discussed.     

Semiconducting and Piezoelectric Oxide Nanostructures Induced by Polar Surfaces

Zinc oxide, an important semiconducting and piezoelectric material, has three key characteristics. First, it is a semiconductor, with a direct bandgap of 3.37 eV and a large excitation binding energy (60 meV), and exhibits near‐UV emission and transparent conductivity. Secondly, due to its non‐centrosymmetric symmetry, it is piezoelectric, which is a key phenomenon in building electro‐mechanical coupled sensors and transducers. Finally, ZnO is bio‐safe and bio‐compatible, and can be used for biomedical applications without coating. With these unique advantages, ZnO is one of the most important nanomaterials for integration with microsystems and biotechnology. Structurally, due to the three types of fastest growth directions—<0001>, <01 0>, and <2 0>—as well as the ±(0001) polar surfaces, a diverse group of ZnO nanostructures have been grown in our laboratory. These include nanocombs, nanosaws, nanosprings, nanorings, nanobows, and nanopropellers. This article reviews our recent progress in the synthesis and characterization of polar‐surface‐induced ZnO nanostructures, their growth mechanisms, and possible applications as sensors, transducers, and resonators. It is suggested that ZnO could be the next most important nanomaterial after carbon nanotubes.     

Photoreflectance study of InAs quantum dots on GaAs(n 1 1) substrates

InAs self-assembling quantum dots (SAQDs) were grown on GaAs(n 1 1) substrates (n=2,3,4,5) by molecular beam epitaxy. Their structural and optical properties were studied by reflection high-energy electron diffraction, atomic force microscopy (AFM) and photoreflectance spectroscopy (PR). The PR spectra from 0.7 to 1.3 eV presented transitions associated to the SAQDs. The energy transitions were obtained by fitting the PR spectra employing the third derivative line-shape model. For n=2,4,5, two functions were required to fit the spectra. For n=3 only one function was required, in agreement with the more uniform SAQDs size distribution observed by AFM on GaAs(3 1 1)A. Franz–Keldysh oscillations (FKO) were observed in the PR spectra at energies higher than the GaAs band gap. From the FKO analysis we obtained the GaAs built-in internal electric field strength (F_int) at the InAs/GaAs(n 1 1) heterointerface. From F_int we made an estimation of the GaAs strain at the heterointerface.