Optical transmission through double-layer, laterally shifted metallic subwavelength hole arrays.

We measure the transmission of IR radiation through double-layer metal films with periodic arrays of subwavelength holes. When the two metal films are placed in sufficiently close proximity, two types of transmission resonances emerge. For the surface plasmon mode, the electromagnetic field is concentrated on the outer surface of the entire metallic layer stack. In contrast, for the guided mode, the field is confined to the gap between the two metal layers. Our measurements indicate that, as the two layers are laterally shifted from perfect alignment, the peak transmission frequency of the guided mode decreases significantly, while that of the surface plasmon mode remains largely unchanged, in agreement with numerical calculations.

Nanopores in solid-state membranes engineered for single molecule detection.

A nanopore is an analytical tool with single molecule sensitivity. For detection, a nanopore relies on the electrical signal that develops when a molecule translocates through it. However, the detection sensitivity can be adversely affected by noise and the frequency response. Here, we report measurements of the frequency and noise performance of nanopores

Casimir force on a surface with shallow nanoscale corrugations: geometry and finite conductivity effects.

We measure the Casimir force between a gold sphere and a silicon plate with nanoscale, rectangular corrugations with a depth comparable to the separation between the surfaces. In the proximity force approximation (PFA), both the top and bottom surfaces of the corrugations contribute to the force, leading to a distance dependence that is distinct from a flat surface. The measured Casimir force is found to deviate from the PFA by up to 10%, in good agreement with calculations based on scattering theory that includes both geometry effects and the optical properties of the material.

Measurement of the Casimir force between a gold sphere and a silicon surface with nanoscale trench arrays.

We report measurements of the Casimir force between a gold sphere and a silicon surface with an array of nanoscale, rectangular corrugations using a micromechanical torsional oscillator. At distances between 150 and 500 nm, the measured force shows significant deviations from the pairwise additive formulism, demonstrating the strong dependence of the Casimir force on the shape of the interacting bodies. The observed deviation, however, is smaller than the calculated values for perfectly conducting surfaces, possibly due to the interplay between finite conductivity and geometry effects.

Controlling the phase delay of light transmitted through double-layer metallic subwavelength slit arrays.

We demonstrate that the phase of light transmitted through double-layer subwavelength metallic slit arrays can be controlled through lateral shift of the two layers. Our samples consist of two aluminum layers, each of which contains an array of subwavelength slits. The two layers are placed in sufficient proximity to allow coupling of the evanescent fields at resonance. By changing the lateral shift between the layers from zero to half the period, the phase of the transmitted electromagnetic field is increased by pi, while the transmitted intensity remains high. Such a controllable phase delay could open new capabilities for nanophotonic devices that cannot be achieved with single-layer structures.

Small-Signal Performance and Modeling of sub-50nm nMOSFETs with f above 460-GHz.

We have fabricated and tested the performance of sub-50nm gate nMOSFETs to assess their suitability for mixed signal applications in the super high frequency (SHF) band, i.e. 3-30GHz. For a 30nm×40 µm×2 device, we found f(T) =465GHz at V(ds)=2V, V(g)=0.67V, which is the highest cut-off frequency reported for a MOSFET produced on bulk silicon substrate so far. However, our measurements of f(max) and noise figure indicate that parasitics impose limitations on SHF operation. We also present a high-frequency ac model appropriate to sub-50nm gate length nanotransistors, which incorporates the effects of the parasitics. The model accurately accounts for measurements of the S and Y parameters in the frequency range from 1 to 50GHz.

Beyond the Gene Chip.

We describe a prospective strategy for reading the encyclopedic information encoded in the genome: using a nanopore in a membrane formed from an MOS-capacitor to sense the charge in DNA. In principle, as DNA permeates the capacitor-membrane through the pore, the electrostatic charge distribution characteristic of the molecule should polarize the capacitor and induce a voltage on the electrodes that can be measured. Silicon nanofabrication and molecular dynamic simulations with atomic detail are technological linchpins in the development of this detector. The sub-nanometer precision available through silicon nanotechnology facilitates the fabrication of the detector, and molecular dynamics provides us with a means to design it and analyze the experimental outcomes.

Long-term reliability of semiadjustable articulator interchangeability.

PURPOSE: Interchangeability between articulators allows mounted casts to be accurately transferred from one articulator to another. The purpose of this study was to evaluate the interchangeability of Whip-Mix model #2240 articulators (Whip-Mix Corporation, Louisville, KY) that had been in clinical use for between 1 and 6 years. MATERIALS AND METHODS: Forty-six Whip-Mix model #2240 articulators that had been in clinical use by students, practitioners, or laboratory technicians for between 1 and 6 years were evaluated for interchangeability using the Whip-Mix #2245 check system. The horizontal tolerance of the check system was 94 microns. The articulators were also evaluated in the vertical dimension at four locations around the check system cylinders using 26-micron shimstock. Vertical discrepancies between the cylinders were recorded as the thickness of 0, 1, 2, or more than 2 pieces of shimstock. RESULTS: Thirty-eight of the articulators (83%) passed the test for interchangeability. These articulators were interchangeable with other Whip-Mix model #2240 articulators fabricated over a 5 1/2-year period (December 1990 to August 1996). In the vertical dimension, most articulators had discrepancies < or = 26 microns. Three articulators (6.5%) had vertical discrepancies greater than 52 microns. CONCLUSIONS: (1) Eighty-three percent of Whip-Mix model #2240 articulators that had been in clinical use for between 1 and 6 years remained interchangeable within a tolerance of 94 microns in the horizontal dimension. (2) Only three articulators in this study (6.5%) had a vertical discrepancy at any location between the cylinders greater than 52 microns. (3) The model #2240 articulator has the potential to remain interchangeable during clinical use.

The scimitar syndrome: demonstration with magnetic resonance imaging.

The authors describe a case of scimitar syndrome, which is a rare congenital lung abnormality characterized by partially anomalous pulmonary venous return. MRI findings as well as other methods of diagnosis are discussed.

Design and fabrication of high-efficiency beam splitters and beam deflectors for integrated planar micro-optic systems.

High-frequency gratings with rectangular-groove profiles are used to generate high-efficiency beam splitters and beam deflectors. The effects of the grating design parameters, i.e., period, groove depth, duty cycle, number of phase levels, and polarization state (TE and TM) of the incoming signal, are considered. The case of the binary beam splitter grating is analyzed by using rigorous electromagnetic grating analysis. Fabrication techniques are presented in which three different lithographic techniques are considered (optical contact, deep-UV stepper reduction, and electron-beam direct write). Experimental results of 97% efficiency for the beam splitter grating and up to 80% for the beam deflector grating are reported.

Soft-x-ray projection lithography experiments using Schwarzschild imaging optics.

Soft-x-ray projection imaging is demonstrated by the use of 14-nm radiation from a laser plasma source and a single-surface multilayer-coated ellipsoidal condenser. Aberrations in the condenser and the Schwarzschild imaging objective are characterized and correlated with imaging performance. A new Schwarzschild housing, designed for improved alignment stability, is described.

Diffraction-limited soft-x-ray projection imaging using a laser plasma source.

Projection imaging of 0.1-microm lines and spaces is demonstrated with a Mo/Si multilayer coated Schwarzschild objective and 14-nm illumination from a laser plasma source. This structure has been etched into a silicon wafer by using a trilevel resist and reactive ion etching. Low-contrast modulation at 0.05-microm lines and spaces is observed in polymethylmethacrylate.

Soft-x-ray projection lithography: printing of 0.2-microm features using a 20:1 reduction.

We demonstrate nearly diffraction-limited printing of 0.2-microm features, using soft x rays of approximately 36-nm wavelength. An open-stencil transmission mask with minimum features of 4 microm was imaged by a twentyfold-reduction Schwarzschild-type objective onto silicon wafers coated with various e-beam resists. Implications for soft-x-ray projection lithography are discussed.

Changes in CNS responses to high pressure during maturation of newborn mice.

From birth to maturity CD-2 mice were exposed to progressively increasing pressures of helium-oxygen. In all age groups a regular progression of changes in locomotor behavior was observed including, in sequence, increased locomotor activity and two types of convulsions designated as types I and II. The effects of altering compression rate and of reserpine pretreatment were recorded for all age groups. Maturation in these mice is associated with increased resistance to high-pressure neurological syndrome convulsions of either type, in contrast to what might have been expected from previous phylogenetic studies. The patterns in development of the two seizure types differ greatly in detail, further supporting the previously advanced inference that they represent neurological events that differ in kind rather than merely quantitatively. The effect of the results on theories that concern the mechanism of action of pressure on the vertebrate central nervous system is discussed.

Time, rate, and temperature factors in the onset of high-pressure convulsions.

An interrupted compression profile technique was used to develop data to separate the effects of time and pressure factors governing increase of high-pressure neurological syndrome (HPNS) convulsion threshold pressures (the compression rate effect) during different compression profiles. A single differential equation fits all data available to date for compression rate effect on convulsion thresholds of CD-1 mice (three distinct types of compression profile; mean compression rates 12-1,000 atm/h). The process leading to increase in HPNS convulsion pressure is initiated at the very beginning of compression, proceeds at increasingly rapid rates as higher pressures are attained, and approaches a limiting upper convulsion pressure. The convulsion threshold pressure in any given experiment is independent of the compression rate prevailing during the time immediately preceding onset of the seizure. The magnitude of the compression rate effect in the CD-1 mouse is independent of chamber temperature over a range of 27-36 degrees C, and rectal temperatures of 29.2-37.5 degrees C. The bearing of these results on the design of optimal compression schedules and on the analysis of the neurological mechanisms underlying the HPNS is discussed.

Rate factors in development of the high-pressure neurological syndrome.

The effect of varying the pressure/time profile upon development of tremors and convulsions of the high-pressure neurological syndrome was studied in adult mice and squirrel monkeys and in baby mice. Two distinct response patterns were observed. In the adults rapid compression produces early onset of convulsions; convulsions subside rapidly when animals are held at constant pressure just above the convulsion point; and interrupted compression schedules show that total compression time rather than instantaneous compression rate at the moment seizures develop is the controlling parameter. Baby mice up to 12 days of age, by contrast, fail to show any perceptible relation between compression rate and convulsion threshold pressure (Pc); their seizures continue for a considerable period of time after a constant pressure level just above the convulsion threshold has been reached; and interrupted compressions of type a fail to change their convulsion threshold. Together with supplementary data regarding tremor thresholds and the transient increase of convulsion thresholds by prior seizures these results lead to a proposed schema describing these phenomena in terms of a pressure-dependent primary event predisposing to tremors and convulsions; a time-dependent event counteracting the convulsions (absent in baby mice); and a transient effect of prior convulsions, raising subsequent Pc.