A Comparison of Acoustic Microscopy, Imaging, Holographic and Tomographic Procedures

In this paper we offer our view on the various systems that are used or should be used in the field of NDE. We conclude that imaging systems evolve around a given form of radiation and that a given imaging system is not easily adapted to an alternate form

Acoustic Microscopy Via Scanning

We offer via posters some of the latest images recorded with the scanning acoustic microscope operating near 2.5 GHz. Our report at the 1978 Review included a description of the scanning instrument which had been scaled up in frequency to 3 GHz. This was accomplished in large part by fabricating acoustic lens with smaller radii and by heating the liquid to reduce the absorption. In our report for this year, we·will present the results of our material studies as carried out with the new instruments operating near 2.5 GHz. We will include results on four different materials - steel, Cobalt-Titanium, brass and alumina ceramic. Each of these have distinctive characteristics in the acoustic micrographs and each of these have information which is distinct from their optical counterparts

Recent Progress in Materials Studies with Acoustic Microscopy

The scanning acoustic microscope operating in water with a frequency of 2.5 GHz (wavelength 6000 Å) has been used to nondestructively characterize materials and devices in a manner inaccessible to optical and electron microscopy. Adhesion of thin films of Cr on glass (optical masks for photolithography) is shown to be a strong source of acoustic microscope contrast. This offers nondestructive evaluation of film adhesion on a microscopic scale for the first time. Study of intentionally damaged integrated circuit structures reveals damage features not visible in optical microscopy. Microscopic subsurface imaging of composite structures is presented, as in other recent acoustic microscope imaging of materials. Recent theoretical work in acoustic response of layered materials is reviewed

Atomic Force Microscope

The scanning tunneling microscope is proposed as a method to measure forces as small as 10−18 N. As one application for this concept, we introduce a new type of microscope capable of investigating surfaces of insulators on an atomic scale. The atomic force microscope is a combination of the principles of the scanning tunneling microscope and the stylus profilometer. It incorporates a probe that does not damage the surface. Our preliminary results in air demonstrate a lateral resolution of 30 ÅA and a vertical resolution less than 1 Å

Acoustic Microscopy for Materials Characterization

An acoustic microscope with mechanical scanning and piezoelectric film transducers for the input and output has been developed for the microscopic examination of materials.1 In the reflection mode it is possible to work with an acoustic wavelength of 0.5 micrometers and a resolution that compares to that of the optical microscope. The elastic images of material surfaces as recorded with this instrument display interesting features which provide information which complements the optical microscope. In particular we find that different phases show up with good contrast and in alloy material the texture of the grains can be recorded since the grain orientation influences the acoustic reflectivity

Resonant harmonic response in tapping-mode atomic force microscopy

Cataloged from PDF version of article.Higher harmonics in tapping-mode atomic force microscopy offers the potential for imaging and sensing material properties at the nanoscale. The signal level at a given harmonic of the fundamental mode can be enhanced if the cantilever is designed in such a way that the frequency of one of the higher harmonics of the fundamental mode ~designated as the resonant harmonic! matches the resonant frequency of a higher-order flexural mode. Here we present an analytical approach that relates the amplitude and phase of the cantilever vibration at the frequency of the resonant harmonic to the elastic modulus of the sample. The resonant harmonic response is optimized for different samples with a proper design of the cantilever. It is found that resonant harmonics are sensitive to the stiffness of the material under investigation

Nanometer-scale patterning and individual current-controlled lithography using multiple scanning probes

Cataloged from PDF version of article.Scanning probe lithography(SPL) is capable of sub-30-nm-patterning resolution and nanometer-scale alignment registration, suggesting it might provide a solution to the semiconductor industry’s lithography challenges. However, SPL throughput is significantly lower than conventional lithography techniques. Low throughput most limits the widespread use of SPL for high resolution patterning applications. This article addresses the speed constraints for reliable patterning of organic resists. Electrons field emitted from a sharp probe tip are used to expose the resist. Finite tip-sample capacitance limits the bandwidth of current-controlled lithography in which the tip-sample voltage bias is varied to maintain a fixed emission current during exposure. We have introduced a capacitance compensation scheme to ensure continuous resist exposure of SAL601 polymerresist at scan speeds up to 1 mm/s. We also demonstrate parallel resist exposure with two tips, where the emission current from each tip is individually controlled. Simultaneous patterning with multiple tips may make SPL a viable technology for high resolution lithography. © 1999 American Institute of Physic