167 research outputs found
A Scanned Perturbation Technique For Imaging Electromagnetic Standing Wave Patterns of Microwave Cavities
We have developed a method to measure the electric field standing wave
distributions in a microwave resonator using a scanned perturbation technique.
Fast and reliable solutions to the Helmholtz equation (and to the Schrodinger
equation for two dimensional systems) with arbitrarily-shaped boundaries are
obtained. We use a pin perturbation to image primarily the microwave electric
field amplitude, and we demonstrate the ability to image broken time-reversal
symmetry standing wave patterns produced with a magnetized ferrite in the
cavity. The whole cavity, including areas very close to the walls, can be
imaged using this technique with high spatial resolution over a broad range of
frequencies.Comment: To be published in Review of Scientific Instruments,September, 199
Microwave shielding of transparent and conducting single-walled carbon nanotube films
The authors measured the transport properties of single-walled carbon
nanotube (SWCNT) films in the microwave frequency range from 10 MHz to 30 GHz
by using the Corbino reflection technique from temperatures of 20-400 K. Based
on the real and imaginary parts of the microwave conductivity, they calculated
the shielding effectiveness for various film thicknesses. Shielding
effectiveness of 43 dB at 10 MHz and 28 dB at 10 GHz are found for films with
90% optical transmittance, which suggests that SWCNT films are promising as a
type of transparent microwave shielding material. By combining their data with
those from the literature, the conductivity of SWCNT films was established in a
broad frequency range from dc to visible.Comment: 4 pages, 4 figure
Noncontact electrical metrology of Cu/low-k interconnect for semiconductor production wafers
We have demonstrated a technique capable of in-line measurement of dielectric
constant of low-k interconnect films on patterned wafers utilizing a test key
of ~50x50 \mu m in size. The test key consists of a low-k film backed by a Cu
grid with >50% metal pattern density and <250 nm pitch, which is fully
compatible with the existing dual-damascene interconnect manufacturing
processes. The technique is based on a near-field scanned microwave probe and
is noncontact, noninvasive, and requires no electrical contact to or grounding
of the wafer under test. It yields <0.3% precision and 2% accuracy for the film
dielectric constant
A near-field scanned microwave probe for spatially localized electrical metrology
We have developed a near-field scanned microwave probe with a sampling volume
of approximately 10 micron in diameter, which is the smallest one achieved in
near-field microwave microscopy. This volume is defined to confine close to 100
percent of the probe net sampling reactive energy, thus making the response
virtually independent on the sample properties outside of this region. The
probe is formed by a 4 GHz balanced stripline resonator with a few-micron tip
size. It provides non-contact, non-invasive measurement and is uniquely suited
for spatially localized electrical metrology applications, e.g. on
semiconductor production wafers.Comment: 6 pages, 3 figures, submitted to Appl. Phys. Let
Superconducting RF Metamaterials Made with Magnetically Active Planar Spirals
Superconducting metamaterials combine the advantages of low-loss, large
inductance (with the addition of kinetic inductance), and extreme tunability
compared to their normal metal counterparts. Therefore, they allow realization
of compact designs operating at low frequencies. We have recently developed
radio frequency (RF) metamaterials with a high loaded quality factor and an
electrical size as small as 658, ( is the free space
wavelength) by using Nb thin films. The RF metamaterial is composed of truly
planar spirals patterned with lithographic techniques. Linear transmission
characteristics of these metamaterials show robust Lorentzian resonant peaks in
the sub- 100 MHz frequency range below the of Nb. Though Nb is a
non-magnetic material, the circulating currents in the spirals generated by RF
signals produce a strong magnetic response, which can be tuned sensitively
either by temperature or magnetic field thanks to the superconducting nature of
the design. We have also observed strong nonlinearity and meta-stable jumps in
the transmission data with increasing RF input power until the Nb is driven
into the normal state. We discuss the factors modifying the induced magnetic
response from single and 1-D arrays of spirals in the light of numerical
simulations.Comment: 4 pages, 7 figure
Near-Field Scanning Microwave Microscopy: Measuring Local Microwave Properties and Electric Field Distributions
We describe the near-field microwave microscopy of microwave devices on a
length scale much smaller than the wavelength used for imaging. Our microscope
can be operated in two possible configurations, allowing a quantitative study
of either material properties or local electric fields.Comment: 4 pages, 8 figures, minor corrections to text and 2 figure
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