11 research outputs found
Millimeter-wave/infrared rectenna development at Georgia Tech
The key design issues of the Millimeter Wave/Infrared (MMW/IR) monolithic rectenna have been resolved. The work at Georgia Tech in the last year has focused on increasing the power received by the physically small MMW rectennas in order to increase the rectification efficiency. The solution to this problem is to place a focusing element on the back side of the substrate. The size of the focusing element can be adjusted to help maintain the optimum input power density not only for different power densities called for in various mission scenarios, but also for the nonuniform power density profile of a narrow EM-beam
Millimeter wavelength rectenna development
Rectennas were studied with the intent of converting the Earth's (black body) radiation into dc power for satellites in earth orbit. Power densities; metal-oxide-metal diodes; antenna design configurations; fluid patterns; substrate mounted antennas; and directions for future work are outlined. This presentation is represented by viewgraphs only
Progress toward superconductor electronics fabrication process with planarized NbN and NbN/Nb layers
To increase density of superconductor digital and neuromorphic circuits by
10x and reach integration scale of Josephson junctions (JJs) per chip,
we developed a new fabrication process on 200-mm wafers, using self-shunted
Nb/Al-AlOx/Nb JJs and kinetic inductors. The process has a layer of JJs, a
layer of resistors, and 10 fully planarized superconducting layers: 8 Nb layers
and 2 layers of high kinetic inductance materials, MoN and NbN, with sheet
inductance of 8 pH/sq and 3 pH/sq, respectively. NbN films were deposited by
two methods: with =15.5 K by reactive sputtering of a Nb target in
Ar+N mixture; with in the range from 9 K to 13 K by plasma-enhanced
chemical vapor deposition (PECVD) using
Tris(diethylamido)(tert-butylimido)niobium(V) metalorganic precursor. PECVD of
NbN was investigated to obtain conformal deposition and filling narrow trenches
and vias with high depth-to-width ratios, which was not possible to achieve
using sputtering and other physical vapor deposition (PVD) methods at
temperatures below required to prevent degradation of Nb/Al-AlOx/Nb
junctions. Nb layers with 200 nm thickness are used in the process layer stack
as ground planes to maintain a high level of interlayer shielding and low
intralayer mutual coupling, for passive transmission lines with wave impedances
matching impedances of JJs, typically <=50 , and for low-value
inductors. NbN and NbN/Nb bilayer are used for cell inductors. Using NbN/Nb
bilayers and individual pattering of both layers to form inductors allowed us
to minimize parasitic kinetic inductance associated with interlayer vias and
connections to JJs as well as to increase critical currents of the vias.
Fabrication details and results of electrical characterization of NbN films,
wires, and vias, and comparison with Nb properties are given.Comment: 12 pages, 16 figures, 4 tables, 49 references. Submitted to IEEE TAS
on Nov. 10, 202
Studies of dipole antennas on finite thickness substrates with planar integrated focusing elements
Ph.D.Glenn S. Smit
Deep sub-micron stud-via technology for superconductor VLSI circuits
A fabrication process has been developed for fully planarized Nb-based superconducting inter-layer connections (vias) with minimum size down to 250 nm for superconductor very large scale integrated (VLSI) circuits with 8 and 10 superconducting layers on 200-mm wafers. Instead of single Nb wiring layers, it utilizes Nb/Al/Nb trilayers for each wiring layer to form Nb pillars (studs) providing vertical connections between the wires etched in the bottom layer of the trilayer and the next wiring layer that is also deposited as a Nb/Al/Nb trilayer. This technology makes possible a dramatic increase in the density of superconducting digital circuits by reducing the area of interconnects with respect to presently utilized etched contact holes between superconducting layers and by enabling the use of stacked vias. Results on the fabrication and size dependence of electric properties of Nb studs with dimensions near the resolution limit of 248-nm photolithography are presented. Superconducting critical current density in the fabricated stud-vias is about 0.3 A/μm 2 and approaches the depairing current density of Nb films.United States. Air Force (Contract FA8721-05-C-0002