Detection of acoustoelectric voltage by shear-horizontal-plate waves in cadmium-sulphide plates

A novel configuration employing shear-horizontal-plate waves is used to detect acoustoelectric voltage in photoconductive cadmium sulphide. A theoretical expression (neglecting diffusion effects) for the voltage is also given.     

Nondestructive evaluation of the semiconductor interface states' density using the transverse acoustoelectric voltage

Nondestructive determination of the interface states' density (D_it) is presented. The measurement technique, utilizing the surface acoustic waves, is applied to silicon/thermal oxide structure. The detected signal is the transverse acoustoelectric voltage amplitude (TAV) which is monitored as a function of the applied bias voltage (TAV-V). D_it is measured by comparing the theoretical and experimental TAV-V curves. The calculation procedure of the D_it and the experimental example are presented.     

Image processing using acoustic surface waves

An application of acoustic surface waves for image processing is reported. The information compression of videophone signals takes advantage of the so-called Hadamard transformation. Acoustic-surface-wave tapped delay lines are efficient for the achievement of such a transform in a low-cost real-time device. The results of initial experiments are reported.     

Directional coupler using acoustic surface waves

The properties of interdigital transducers have been used to construct a directional coupler. The coupler consists basically of an array of eight transducers etched from an aluminium film deposited on a lithium-niobate substrate. Experimentally, a directivity of 17 dB was obtained at 75 MHz.     

激光激发表面波测量表面缺陷深度的数值研究

为了研究声表面波与表面缺陷的作用机理,实现激光超声技术对表面微缺陷定量检测,本文采用有限元法首先分别研究了声表面波与缺陷前沿、缺陷后沿的作用,然后讨论了缺陷宽度的存在对缺陷前沿与声表面波作用的影响,最后通过分析矩形缺陷与声表面波的作用,给出了能定量表征表面缺陷的特征量。研究结果表明:RS波(特征点Q)后的振荡信号(特征点W、E)来源于透射表面波在缺陷后沿所产生的振荡。特征点Q的到达时间随表面缺陷深度或宽度增大都呈现微小的线性增长；特征点W、E的到达时间差随表面缺陷深度的增大呈线性增长,与缺陷宽度的变化无关。最后,根据特征点的到达时间实现了缺陷深度的定量计算。研究结果为表面缺陷的定量检测提供了理论依据。     

Realisation of microwave-circuit functions using acoustic surface waves

In realising microwave-circuit functions using surface technology, the physical size of passive components using e.m. waves imposes a limitation. This letter investigates the application of acoustic waves to this case. The feasibility of constructing waveguides and directional couplers is demonstrated experimentally, and some theoretical considerations referring to waveguides are presented.     

Programmable correlation using parametric interactions in acoustic surface waves

Real-time correlation of 31 chip binary p.s.k. waveforms has been obtained using nonlinear interactions of acoustic surface waves, with a signal bandwidth of 8 MHz. A dynamic range of 20 dB was obtained. Calculations indicate that a dynamic range of 50 dB should be obtainable quite readily, making the device attractive for adaptive signal processing.     

Generation of surface acoustic waves using the electrostrictive effect

Surface acoustic waves have been generated and detected on a biased electrostrictive substrate. A delay line with an insertion loss of 26 dB at 77 K has been constructed on strontium titanate. The temperature and electric-field dependence of the insertion loss are given.     

On a new type of surface acoustoelectric waves in hexagonal crystals

It is shown that, in the basal plane of crystals with hexagonal symmetry, purely longitudinal surface acoustoelectric waves can propagate. In contrast to well-known Gulyaev-Blustein transverse waves, these longitudinal waves are localized in the surface layer, whose thickness is on the order of the wavelength. The field of mechanical displacements and the potential field of the wave are phase shifted by ??/2. The electricfield vector of the wave is circularly polarized in the sagittal plane.     

Visualisation of surface acoustic waves

A simple method for acoustic-surface-wave visualisation is described which is applicable to both piezoelectric and non-piezoelectric surfaces. Briefly, a uniform layer of small particles, comparable to the wavelength, is distributed over the acoustic surface. The acoustic-beam pattern of an incident surface wave is then traced out by scattering the particles out of the propagation path. Experiments at 100 MHz on lithium-niobate surfaces are described.     

Low-sidelobe weighted-coupled integrated acoustooptic tunablefilter using focused surface acoustic waves

A single-stage low-sidelobe weighted-coupled integrated acoustooptic tunable filter (IAOTF) operating at the optical wavelength of 1.31 μm has been realized on a Y-cut X-propagating LiNbO₃ substrate for the first time. The weighted-coupling, which enabled the achievement of low-sidelobe levels, was facilitated by focused surface acoustic waves generated by a curved interdigital transducer. First sidelobe levels as low as -17.6 dB have been obtained. Optical bandwidth of 4 nm and tuning range of 170 nm for an interaction length of 6 mm were also accomplished     

Generation and correlation of quadriphase-coded signals using acoustic surface waves

The use of acoustic surface waves to generate and correlate a 4-phase 15-bit generalized Barker sequence is described. Experimental results using quartz and LiNbO3as substrates are reported.     

Variable delay for acoustic surface waves by electro-acousto-optic interaction

Continuosly variable analogue delay is demonstrated by using reflections from a laser-light-induced impedence discontinuity on a photoconductive layer evaporated on an LiNbO3 delay line at 75 MHz. ?30dB reflection loss is obtained with a delay range of 20 ?s.     

Theoretical computations on ridge acoustic surface waves using the finite-element method

Theoretical computations have been carried out on ridge acoustic surface waves using the finite-element method. The results obtained agree substantially with experiments performed previously.     

Optical probing of surface acoustic waves

Light diffraction by surface acoustic waves is used in studying the propagation characteristics of Rayleigh waves on y-cut z-oriented LiNbO3. In reflection, only the surface deformation contributes to the diffracted light. In transmission, the photoelastic effect, which is incident beam polarization dependent, must also be considered. Such optical probing has been used to study the Fresnel diffraction radiation pattern of an interdigital transducer, to measure beam steering effects related to transducer misalignment on an anisotropic substrate, and to measure reflection and transmission coefficients of an electrically loaded transducer. Attenuation measurements have been made over frequencies as high as 3.5 GHz. The power dependence of attenuation and harmonic generation is also examined.     

Wavefront visualisation of acoustic surface waves

Acoustic surface waves (a.s.w.) propagating on yz-cut lithium niobate have been visualised by two imaging techniques. The wavefronts of straight-crested and convergent a.s.w. have been rendered visible on the screen of a storage oscilloscope.     

Ridge guides for acoustic surface waves

A low-velocity flexural mode has been excited on acoustic-surface-wave topographic guides. With structures offering some hope of realisation at high frequencies, very strong confinement of the guided wave is obtained. Q factors in excess of 1000 have been observed on a ring resonator only ten wave lengths in diameter.     

Application of the transverse acoustoelectric effect to studying silicon surface charging upon water adsorption

Water adsorption on a silicon surface in a layered Si-LiNbO₃ structure with an air gap is studied using the transverse acoustoelectric effect on surface acoustic waves. A generalized analysis of measurements of the transverse acoustoelectric effect makes it possible to determine the initial band bending of the Si surface, its changes during gas cycles, hence, the sign and charging kinetics of Si upon H₂O adsorption. Depending on the properties of the semiconductor surface defects, both the donor and acceptor nature of the interaction of H₂O with Si are observed. For samples with a thermal oxide, the donor-type interaction occurs; for samples with a natural oxide, both interaction types take place. Based on the used physical model of oxide charging upon exposure to an adsorbate, a comprehensive methodical approach is proposed, which allows the targeted development of acoustoelectronic structures for sensor applications.     

SEM中用表面电子束激励势法研究半导体特性

本文考虑用一种新的非接触法来研究和测量半导体晶体微区特性的方法,这种方法是基于扫描电镜中控测半导体的表面电子束激励电势(SEBIV)法来研究半导体的电物现特性和测量半导体电物现参数。本文讨论了一种测量半导体晶体的非平衡载流子的扩散长度L和寿命τ的方法。本文还讨论了用本方法可观测到的表面电子束激励电势图像衬度的形成和它与扫描方向、半导体材料的物理特性和表面激励电势极性的关系。SEBIV法是一种非接触而且非常有效的观测和研究半导体晶体中活性非平衡载流子电特性的方法,这种方法有下列特点:1测量时不需要与样品直接接…