Finite element method simulations of periodically corrugated metal terahertz wire waveguides have been conducted with concurrent analysis done on both the near-field confinement properties and the far-field emission properties at the end of the waveguides. This modeling was used to guide the choice of design parameters for the fabrication of waveguides with laser micromachining. The waveguides were characterized with a fiber-coupled terahertz time-domain spectroscopy and imaging system. The propagation properties as well as the frequency dependent diffraction at the end of the wire waveguides were examined and compared to straight, non-engineered metallic wire waveguides.

Polyester resin based glass fiber reinforced composite panels obtained from a local windmill turbine blade part manufacturing company are used to evaluate the performance of inter-digital transducer (IDT) surface wave transducers. Interaction of surface waves with fiberglass layers is addressed in this work. Additionally, artificially created flaws such as cracks, impact damage and delamination are also studied in terms of amplitude changes in order to attempt to quantify the size, location and severity of damage in the test panels. As a potential application to the structural health monitoring (SHM) of windmill turbine blades, the coverage distance within the width of the sound field is estimated to be over 80 cm when a set of IDT sensors consisted of one transmitter and two receivers in a pitch-catch mode.

The pulsed laser deposition of YBa2Cu3O7-x targets by excimer laser at fluences of 4-10 J cm(-2) in low pressure oxygen backgrounds yields emissive plumes with kinetic energies of 50-200 eV, driving the formation of a shock front with Mach numbers of M = 10-50. The propagation of the shock front is independent of atomic species and adequately characterized by the Sedov-Taylor shock model if the dimensionality of the plume is allowed to deviate from ideal spherical expansion. The ideal efficiency of energy conversion from laser pulse to shock expansion is nearly unity at 1 Torr, but decreases rapidly at lower pressures, where the plume expands beyond the laser footprint during ablation. The low oxygen background pressures, 100-1000mTorr, typically employed for the production of superconducting films is sufficient for the generation of a strong shock front with shock thickness of 5mm to less than 0.4 mm, but too low to develop three-dimensional flow. Indeed, dimensionality of the expansion ranges from n = 0.8 to 2.4 over the background oxygen pressure range of 25-1000mTorr. Shock strength is proportional to the Mach number and inversely dependent on pressure, indicating a thickness limited to approximately the collision mean free path.

Emission time-of-flight (TOF) profiles have been obtained using gated imagery to further the process control during the pulsed laser deposition of the high temperature superconductor, YBa2Cu3O7−x. An intensified charge coupled device array was used to obtain a sequence of plume images at 10ns temporal resolution and 0.2mm spatial resolution. Plume imagery is transformed to TOF profiles and pulse-to-pulse variations removed using physically based smoothing techniques. Comparison with non-imaging sensors establishes excellent agreement, with systematic uncertainties in streaming speed and temperatures of less than 15% and 8%, respectively. The resulting streaming speeds of 0.4–1.2×106cm∕s and characteristic temperatures of 20000–200000K are characterized across the full plume. This new imaging TOF technique enables the monitoring of the complete evolution of speed distributions. Indeed, significant deviations from the forward-directed Maxwellian speed distributions are observed.

The paper will give a brief overview on techniques that have been developed or are in progress for high resolution characterization of materials at the Center for Materials Diagnostics, University of Dayton. Acoustic microscopy is used to characterize coating systems and localized defects like corrosion pits. Significantly higher resolution is provided by Ultrasonic force microscopy, which allows the imaging of elastic inhomogenities in materials for example, studying nano-grain structures in copper films and nano precipates in aluminum alloys. Several optical high-resolution techniques have been developed or are in progress. These include interferometric imaging of the response of acoustic MEMS transducers, imaging of acoustic wave structures and early detection of crack initiation. Microellipsometric and NSOM imaging techniques are in development for imaging of surface structures significantly smaller than the optical wavelength. White light interference microscopy is frequently used to characterize surface topography with nanometer resolution for example, to quantify fretting damage or stress fields in front of fractures.

In 1981, Gerd Binning and Heinrich Rohree at IBM Zurich developed the first generation of the scanning probe microscope, the scanning tunneling microscope for which they received the Noble Prize in physics. The Scanning Tunneling Microscope (STM) was a fantastic breakthrough with its capability to image atoms with angstrom precision. The physical operating principle of the STM is that when a bias voltage is applied between a sharp tip and a sample, a tunneling current is produced as electrons travel from one material to the other. This tunneling current is an exponential function of the distance between the tip and the sample and is responsible for the angstrom precision of the STM [1]. Wide use of the STM however was constrained by the requirement that the scanning tip and the sample must be conductive. The Atomic Force Microscope (AFM) was developed from the STM system and overcame the necessity of conductivity that accompanied STM imaging. The AFM sacrifices some of the atomic resolution of the STM as a trade off for imaging both nonconductors and conductors. The AFM resolution is classified as near atomic for topographic images.

The surface of laser‐treated ceramic hard disk drive head sliders has been imaged with the atomic force microscope (AFM) and ultrasonic force microscope (UFM). The surface topography image from the AFM is compared with the elasticity image generated by the UFM on the same region. Images of the surface structure changes along with microcracking in the laser‐treated regions are presented. The possible reasons for the development of microcracking and the enhanced contrast that the UFM provides of the microcracks and the material microstructure changes in the laser‐treated region are discussed.

The material being used to construct interconnects in microelectronic circuitry is changing as developers switch from aluminum alloys to copper in order to make increasing smaller circuit wires. The performance of copper interconnects can be adversely affected by electromigration, precipitation formation, and changes in the grain microstructure of the wire. There is a need for characterization methods that can allow examination of the interconnects/wires and their grain structure in the nanometer range. One of the most powerful tools that are routinely used for characterization of nanostructured materials is the Atomic Force Microscope. The combination of AFM with ultrasonics (UFM) allows a near field acoustic microscopic image to be generated. By having the AFM tip detect the ultrasonic signal, the lateral resolution limitation of the acoustic wavelength that occurs in conventional acoustic microscopy can be overcome so that imaging with nanometer resolution is possible. In this paper, we present a qualitative comparison of AFM-UFM images on different forms of copper nanograins from two sources namely, ion beam deposited thin films samples containing polycrystalline sections and the aligned copper grains in the wires of an actual working microelectronic device. Images of the nanometer grain structure will be presented. Explanations for the image differences between samples will be discussed and possible applications are suggested.

The quest for technical advancements is leading scientists to study how devices interact on the nanometer scale. There is a growing need for material characterization techniques, which can image, detect damage/changes, and characterize the material and its engineered structures in the nanometer region. One of the most powerful tools that are routinely used for characterization of nanostructured materials is Atomic Force Microscopy. The Atomic Force Microscope (AFM) provides a 3 dimensional surface topographic image of a sample. When imaging a sample's surface, a 10-micron or smaller area maybe fairly flat so that the AFM image provides very little detail and contrast even though the overall sample surface is quite rough. Ultrasonic Force Microscopy (UFM) has been developed in order to improve the image contrast on flat areas of interest where the AFM topography images are limited in contrast. The combination of AFM-UFM allows a near field acoustic microscopic image to be generated. The AFM tip is used to detect the ultrasonic waves and overcomes the lateral resolution limit of the acoustic wavelength that occurs in acoustic microscopy. By using the elastic changes under the AFM tip, an image of much greater detail than the AFM topography can be generated. Nondestructive evaluation and material characterization on ceramic and copper applications in which the addition of UFM has greatly improved upon the AFM images is presented.