We have directly imaged n‐alkane layers adsorbed at the liquid/graphite interface using a scanning tunneling microscope. The layers possessed a high degree of two‐dimensional ordering. The adsorbate was observed to enhance the tunneling current, and the atomic structure of the images was dominated by features associated with the substrate. These systems are excellent vehicles for studies concerning the imaging mechanism of adsorbed organic layers because of their stability and simplicity.

Short-period fiber Bragg gratings with weakly tilted grating planes generate multiple strong resonances in transmission. Our experimental results show that the wavelength separation between selected resonances allows the measurement of the refractive index of the medium surrounding the fiber for values between 1.25 and 1.44 with an accuracy approaching $1\times {10}^{-4}$. The sensor element is $10\text{\hspace{0.17em} mm}$ long and made from standard single-mode telecommunication grade optical fiber by ultraviolet light irradiation through a phase mask.

This work demonstrates the electrodeposition of micrometer‐scale copper structures using a simple instrument based on the scanning electrochemical microscope (SECM). Copper columns of 25 μm width up to about 2 mm high were deposited on different substrates and interconnects were grown within an integrated circuit package. In the present instrument electrodeposition is localized by applying a voltage between a closely spaced glass insulated Pt disk ultramicroelectrode, ca. 25 μm diam, and a substrate, all immersed in a solution of acidified . The potential, the concentration of the , and the presence of organic additives were all found to affect the microstructure of the deposits and control the efficiency of the deposition. To demonstrate some of the possible applications of this technique, copper lines were grown between pads in an integrated circuit package and an antenna about 2 cm long was grown on a millimeter wave transmission line cantilever. © 2000 The Electrochemical Society. All rights reserved.

In biomedical applications ranging from the study of pathogen invasion to drug efficacy assays, there is a growing need to develop minimally invasive techniques for single-cell analysis. This has inspired researchers to develop optical, electrical, microelectromechanical and microfluidic devices for exploring phenomena at the single-cell level. In this work, we demonstrate an electrical approach for single-cell analysis wherein a 1.6 GHz microwave interferometer detects the capacitance changes (ΔC) produced by single cells flowing past a coplanar interdigitated electrode pair. The experimental and simulated capacitance changes generated by yeast cells are in close agreement. By using the capacitance changes of uniform polystyrene spheres (diameter = 5.7 µm) for calibration purposes, we demonstrate a 0.65 aF sensitivity in a 10 ms response time. Using an RC circuit, a low frequency sinusoidal potential is simultaneously superimposed on the electrode pair to generate a dielectrophoretic force that translates cells. Specifically, when yeast cells suspended in a solution of 90 ppm NaCl in deionized water are exposed to 10 kHz and 3 MHz potentials (ranging from 1–3 V_pp), they experience negative and positive dielectrophoresis, respectively. The corresponding changes in cell elevation above the interdigitated electrodes are detected using the asymmetry of the capacitance signature produced by the cell. Cell elevation changes can be detected in less than 80 ms. The minimum detectable change in elevation is estimated to be 0.22 µm. This approach will have applications in rapid single-cell dielectrophoretic analysis, and may also prove useful in conjunction with impedance spectroscopy.

We report a study of tip artifacts in atomic force microscope (AFM) images of thin film surfaces. Specifically, a troublesome artifact that occurs when an AFM tip images surface features with a radius of curvature less than the apex of the tip. These artifacts are not easily detected, since the affected AFM images are similar to those expected for a thin film with a columnar microstructure. In a study of 23 thin films, we found that for a significant fraction, the AFM image was affected by this type of tip artifact. In the worst cases, the AFM images consisted almost entirely of images of the AFM tip. We discuss a simple technique to determine the extent of these tip artifacts.