Henry Leduc - Academia.edu (original) (raw)

Papers by Henry Leduc

This report describes preliminary tests of a 205 GHz SIS receiver using Pb-alloy and NbN junction... more This report describes preliminary tests of a 205 GHz SIS receiver using Pb-alloy and NbN junctions in a waveguide mixer mount. Double sideband receiver noise temperature as low as 113 K has been measured with a Pb-alloy junction operated at a physical temperature of 4.2 K.

Journal of Astronomical Telescopes, Instruments, and Systems, 2021

We present the initial design, performance improvements, and science opportunities for an upgrade... more We present the initial design, performance improvements, and science opportunities for an upgrade to the Field-Imaging Far-Infrared Line Spectrometer (FIFI-LS). FIFI-LS efficiently measures fine structure cooling lines, delivering critical constraints of the interstellar medium and star-forming environments. The Stratospheric Observatory for Infrared Astronomy (SOFIA) provides the only far-infrared (FIR) observational capability in the world, making FIFI-LS a workhorse for FIR lines, combining optimal spectral resolution and a wide velocity range. Its continuous coverage of 51 to 203 μm makes FIFI-LS a versatile tool to investigate a multitude of diagnostic lines within our galaxy and in extragalactic environments. The sensitivity and field of view (FOV) of FIFI-LS are limited by its 90s-era photoconductor arrays. These limits can be overcome by upgrading the instrument using the latest developments in kinetic inductance detectors (KIDs). KIDs provide sensitivity gains in excess of 1.4 and allow larger arrays, enabling an increase in pixel count by an order of magnitude. This increase allows a wider FOV and instantaneous velocity coverage. The upgrade provides gains in point source observation speed by a factor >2 and in mapping speed by a factor >3.5, enabled by the improved sensitivity and pixel count. This upgrade has been proposed to NASA in response to the 2018 SOFIA Next Generation Instrumentation call.

Nanoscience and Nanotechnology Letters, 2010

Carbon-based nanomaterials have been actively applied to a diverse array of space-based applicati... more Carbon-based nanomaterials have been actively applied to a diverse array of space-based applications in electronics and optics at the Jet Propulsion Laboratory. In the area of nano-electro-mechanical-systems (NEMS), we describe the implementation of carbon nanotubes (CNTs) and carbon nanofibers (CNFs) to dc nanorelays, as well as for AC resonator applications, which are under consideration for extreme environment electronics. We have also implemented single-walled nanotubes (SWNTs) to physical sensing, specifically for forming miniaturized pressure sensors for vacuum micro-cavity applications, where the mechanism of operation in such sensors relies on the thermal conductivity principle. Finally, we have also initiated an effort to apply arrays of vertically oriented CNTs for optical applications, specifically to act as broadband optical absorbers for calibration targets. In this paper, we provide an overview of the recent results in each of these three applications of carbon nanomaterials.

$Research paper thumbnail of Experimental study of the kinetic inductance fraction of superconducting coplanar waveguide$

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2006

We have studied the kinetic inductance fraction (ratio of kinetic inductance to total inductance)... more We have studied the kinetic inductance fraction (ratio of kinetic inductance to total inductance) of superconducting coplanar waveguides (CPWs) by measuring the resonance frequency of CPW transmission line resonators. We describe a procedure for accurately determining the kinetic inductance of transmission line geometries with small kinetic inductance fractions. In this approach, we compare the temperature dependence of the resonance frequency with that of a resonator of the same film thickness but with a large kinetic inductance fraction. We present data for 200 nm-thick Al CPWs of several geometries and compare that with our own calculations and with calculations found in literature.

Physical Review B, 1984

Single crystals of the fast-ion conductors M-P-gallate, where M is K, Rb, Ag, or Tl, have been pr... more Single crystals of the fast-ion conductors M-P-gallate, where M is K, Rb, Ag, or Tl, have been prepared with small amounts of zinc. The zinc doping removes the excess oxygen ions usually found in the conduction plane. Infrared and far-infrared (6-4000 cm ') reAectance and transmission spectroscopy have been used to study the lattice dynamics of the zinc-doped spinel blocks and the conducting cations in the more open conduction plane. Comparing these spectra with the infrared and Raman spectra of the undoped and the stoichiometric gallates, we find that the occupation of sites in the conduction plane is different from that of the undoped materials. In addition, the conduction plane in the Tl-Zn-P-gallate is sufficiently disordered to violate the exclusion principle. No systematic changes were seen in the spinel block lattice modes with the addition of the zinc or the increased cation density which results.

AIP Conference Proceedings, 2006

We are developing a microwave readout multiplexer for arrays of superconducting quantum interfere... more We are developing a microwave readout multiplexer for arrays of superconducting quantum interference devices (SQUIDs). A series of microwave resonators with frequencies ~10 GHz are each loaded by a dc SQUID to a degree that depends on the flux state of the SQUID. By using resonators with high quality factors and slightly different resonance frequencies, many of these resonator-coupled SQUIDs

Ieee Transactions on Microwave Theory and Techniques, 2007

The physical mechanisms underlying a novel chemical sensor based on electron tunneling in metal-i... more The physical mechanisms underlying a novel chemical sensor based on electron tunneling in metal-insulator-metal (MIM) tunnel junctions were studied. Chemical sensors based on electron tunneling were shown to be sensitive to a variety of substances that include iodine, mercury, bismuth, ethylenedibromide, and ethylenedichloride. A sensitivity of 13 parts per billion of iodine dissolved in hexane was demonstrated. The physical mechanisms involved in the chemical sensitivity of these devices were determined to be the chemical alteration of the surface electronic structure of the top metal electrode in the MIM structure. In addition, electroreflectance spectroscopy (ERS) was studied as a complementary surface-sensitive technique. ERS was shown to be sensitive to both iodine and mercury. Electrolyte electroreflectance and solid-state MIM electroreflectance revealed qualitatively the same chemical response. A modified thin-film structure was also studied in which a chemically active layer was introduced at the top Metal-Insulator interface of the MIM devices. Cobalt phthalocyanine was used for the chemically active layer in this study. Devices modified in this way were shown to be sensitive to iodine and nitrogen dioxide. The chemical sensitivity of the modified structure was due to conductance changes in the active layer. IV. ELECTROREFLECTANCE SPECTROSCOPY 4-1 A. BACKGROUND 4-1 B. ERS EXPERIMENTAL DETAILS 4-1 C. ERS RESULTS 4-2 D. ERS DISCUSSION 4-2 V. CHEMICAL SENSING BASED ON METAL-PHTHALOCYANINES 5-1 A. BACKGROUND 5-1 B.

In this paper, we report on a fabrication process developed for submicron area tunnel junctions. ... more In this paper, we report on a fabrication process developed for submicron area tunnel junctions. We have fabricated Nb/AlO x /Nb tunnel junctions with areas down to 0.1 /imû sing these techniques. The devices have shown excellent performance in receiver systems up to 500 GHz and are currently in use in radio astronomy observatories at 115, 230, and 500 GHz. The junctions are fabricated using a variant of the self-aligned-liftoff trilayer process^ with modifications for electron beam lithographic patterning of junction areas. In brief, the technique involves patterning submicron holes in PMMA using electron beam lithography. The negative of this pattern is formed by thermal deposition and liftoff of chromium metal using this PMMA stencil. The chromium pattern is transferred to an underlying polyimide film using oxygen RIE. Junctions are formed by RIE using a gas mixture containing CC12F2 and electrically isolated with thermally evaporated silicon monoxide. Contact wiring and coupling/tuning structures are patterned by RIE.

Receiver noise and RF coupling bandwidth have been measured for a quasioptically coupled diffusio... more Receiver noise and RF coupling bandwidth have been measured for a quasioptically coupled diffusion-cooled hot-electron bolometer mixer at a local oscillator frequency of 1267 GHz and an intermediate frequency of 1.4 GHz. A lowest receiver equivalent noise temperature of 1880 K double-sideband was measured, with an upper limit for the mixer noise temperature of 950 K double-sideband. The amount of absorbed local oscillator power in the bolometer device was approximately 6 nW. The effective instantaneous RF bandwidth measured with a Fourier transform spectrometer was 730 GHz.

A new theoretical model is introduced to describe heterodyne mixer conversion efficiency and nois... more A new theoretical model is introduced to describe heterodyne mixer conversion efficiency and noise (from thermal fluctuation effects) in diffusion-cooled superconducting hot-electron bolometers. The model takes into account the non uniform internal electron temperature distribution generated by Wiedemann Franz heat conduction, and accepts for input an arbitrary (analytical or experimental) superconducting resistance-versustemperature curve. A non-linear large signal solution is solved iteratively to calculate the temperature distribution, and a linear frequency-domain small-signal formulation is used to calculate conversion efficiency and noise. In the small-signal solution the device is discretized into segments, and matrix algebra is used to relate the heating modulation in the segments to temperature and resistance modulations. Matrix expressions are derived that allow single-sideband mixer conversion efficiency and coupled noise power to be directly calculated. The model accounts for self-heating and electrothermal feedback from the surrounding bias circuit.

Aluminum based diffusion cooled hot electron 1)olometers (I-IEB) mixers, predicted to have a broa... more Aluminum based diffusion cooled hot electron 1)olometers (I-IEB) mixers, predicted to have a broader bandwidth, to require less LO power, and perhaps even have lower noise than Nb based diffusion cooled HEBs, have been fabricated. Preliminary DC tests were performed. The bolometer elements consisted of short (0.18 to 0.53 gm), narrow (0.08 to 0.15 pun) and thin (11 nm) aluminum microbridges connected to large contact pads consisting of a novel trilayer Al/Ti/Au. The patterns were defined by electron beam lithography and the metal deposition involved a double angle process, with the aluminum microbridges being deposited at-degree (i.e. straight on) and the pads being deposited at a 45 degree angle without breaking vacuum. The Al/Ti/Au trilayer was developed to provide a way of making contact between the aluminum microbridge and the gold antenna without degrading the properties of the microbridge. The titanium layer acts as a diffusion barrier to avoid damage of the aluminum contact and bolometer microbridge and to lower the transition temperature of the pads to below that of the bolometer microbridge. The Au layer avoids the formation of an oxide on the Ti layer and provides good electrical contact to mixer if embedding circuit and planar antenna. The resistance of the bolometers as a function of temperature was measured. It appears that below the transition temperature of the microbridge (1.8K) but above the transition temperature of the contact pads (0.6K), the proximity effect drives much of the bolometer microbridge normal, which gives the apperance of a very broad transition. This however should not affect the performance of the bolometers since they will be operated at a temperature below the Tc of the pads, and hence no proximity effect will be present. This is evident from the IV characteristics measured at 0.3K. RF characterization tests will be g in shortly.

1993 IEEE MTT-S International Microwave Symposium Digest