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At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS2017

Evidence of Carrier Localization in InAsSb/InSb Digital Alloy nBn Detector

Recently we have demonstrated a novel method of extending the cut-off wavelength of InAsSb nBn detectors, by incorporating a series of monolayers of InSb. Here we study photoluminescence and minority carrier lifetime of this InAsSb/InSb digital alloy. While increasing temperature from 15 K to 40 K we show a 14 meV blue shift of the photoluminescence peak energy and a decrease in lifetime. This deviation from the expected Varshni empirical relation indicates strong carrier localization. We contrast to photoluminescence and lifetime results in bulk InAsSb. We discuss implications of this localization for design of digital alloy InAsSb/InSb nBn detectors.

Pepper, Brian J.↗
DOE OSTI2020

Materials Data on NbN by Materials Project

NbN is Molybdenum Carbide MAX Phase-like structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Nb3+ is bonded to six N3- atoms to form a mixture of face, edge, and corner-sharing NbN6 octahedra. The corner-sharing octahedra tilt angles range from 0–45°. There are three shorter (2.23 Å) and three longer (2.26 Å) Nb–N bond lengths. There are two inequivalent N3- sites. In the first N3- site, N3- is bonded to six equivalent Nb3+ atoms to form a mixture of edge and corner-sharing NNb6 octahedra. In the second N3- site, N3- is bonded to six equivalent Nb3+ atoms to form a mixture of distorted edge and corner-sharing NNb6 pentagonal pyramids. The corner-sharing octahedral tilt angles are 1°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on NbN by Materials Project

NbN is Halite, Rock Salt structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Nb3+ is bonded to six equivalent N3- atoms to form a mixture of corner and edge-sharing NbN6 octahedra. The corner-sharing octahedral tilt angles are 0°. All Nb–N bond lengths are 2.23 Å. N3- is bonded to six equivalent Nb3+ atoms to form a mixture of corner and edge-sharing NNb6 octahedra. The corner-sharing octahedral tilt angles are 0°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on NbN by Materials Project

NbN is Tungsten Carbide structured and crystallizes in the hexagonal P-6m2 space group. The structure is three-dimensional. Nb3+ is bonded to six equivalent N3- atoms to form a mixture of distorted edge, face, and corner-sharing NbN6 pentagonal pyramids. All Nb–N bond lengths are 2.25 Å. N3- is bonded to six equivalent Nb3+ atoms to form a mixture of distorted edge, face, and corner-sharing NNb6 pentagonal pyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on NbN by Materials Project

NbN is Molybdenum Carbide MAX Phase-like structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Nb3+ is bonded to six equivalent N3- atoms to form a mixture of distorted corner and edge-sharing NbN6 pentagonal pyramids. All Nb–N bond lengths are 2.23 Å. N3- is bonded to six equivalent Nb3+ atoms to form a mixture of corner, edge, and face-sharing NNb6 octahedra. The corner-sharing octahedral tilt angles are 46°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on NbN by Materials Project

NbN is Wurtzite structured and crystallizes in the hexagonal P6_3mc space group. The structure is three-dimensional. Nb3+ is bonded to four equivalent N3- atoms to form distorted corner-sharing NbN4 tetrahedra. There are one shorter (1.99 Å) and three longer (2.12 Å) Nb–N bond lengths. N3- is bonded to four equivalent Nb3+ atoms to form distorted corner-sharing NNb4 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on NbN by Materials Project

NbN is Tungsten Carbide-like structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Nb3+ is bonded to six equivalent N3- atoms to form a mixture of edge, corner, and face-sharing NbN6 octahedra. The corner-sharing octahedral tilt angles are 44°. All Nb–N bond lengths are 2.25 Å. N3- is bonded to six equivalent Nb3+ atoms to form a mixture of distorted edge and corner-sharing NNb6 pentagonal pyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on NbN by Materials Project

NbN is Zincblende, Sphalerite structured and crystallizes in the cubic F-43m space group. The structure is three-dimensional. Nb3+ is bonded to four equivalent N3- atoms to form corner-sharing NbN4 tetrahedra. All Nb–N bond lengths are 2.08 Å. N3- is bonded to four equivalent Nb3+ atoms to form corner-sharing NNb4 tetrahedra.

36 MATERIALS SCIENCE↗
NASA NTRS1994

NbN A/D Conversion of IR Focal Plane Sensor Signal at 10 K

We are implementing a 12 bit SFQ counting ADC with parallel-to-serial readout using our established 10 K NbN capability. This circuit provides a key element of the analog signal processor (ASP) used in large infrared focal plane arrays. The circuit processes the signal data stream from a Si:As BIB detector array. A 10 mega samples per second (MSPS) pixel data stream flows from the chip at a 120 megabit bit rate in a format that is compatible with other superconductive time dependent processor (TDP) circuits being developed. We will discuss our planned ASP demonstration, the circuit design, and test results.

conversion↗
NASA NTRS2006

Fabrication and Characterization of Superconducting NbN Nanowire Single Photon Detectors

We report on the fabrication and characterization of high-speed, single photon detectors using superconducting NbN nanowires at a wavelength of 1064 nm. A 15 by 15 micron detector with a detector efficiency of 40% has been measured. Due to kinetic inductance, the recovery time of such large area detectors is longer than that of smaller or single wire detectors. The recovery time of our detectors (50 ns) has been characterized by measuring the inter-arrival time statistics of our detector.

single proton detectors↗
NASA NTRS2017

Extended Cut-Off Wavelength nBn Detector Utilizing InAsSb/InSb Digital Alloy Absorber

We investigated a novel approach to extend a cut -off wavelength of Sb-based nBn detectors. We incorporated a series of single InSb monolayer into InAsSb bulk that allowed to realize a digital alloy absorber with an extended cut-off wavelength of λ = 4.6 μm at T = 200 K. The cut-off wavelength extension to 4.6μm is technologically important for realization of detectors covering CO2 absorption line at 4.26μm

InAsSb/InSb photodiodes↗
DOE OSTI2023

Effects of 63 MeV proton irradiation on the performance of MWIR InGaAs/InAsSb nBn photodetectors

An investigation into the effects of 63 MeV proton irradiation on high-sensitivity mid-wave infrared InGaAs/InAsSb nBn devices is performed. Three different structures with various absorber region doping profiles are irradiated and characterized to assess their impact on performance degradation. Minority carrier lifetime is measured using time-resolved photoluminescence and lifetime damage factors are assessed. The majority carrier concentration is determined via capacitance–voltage measurements and dopant introduction rates are calculated. An analysis of dark current density is performed using these material parameters, revealing a reduction in mobility with proton fluence and the emergence of a proton-induced trap energy level. Quantum efficiency is calculated at each proton fluence, and quantum efficiency damage factors show that the graded doping structure exhibits the least reduction of quantum efficiency with dose, attributed to its effective mobility enhancement. Conclusively, detector sensitivity, assessed via shot-noise limited noise-equivalent irradiance, shows that the graded doping structure is the least susceptible to high energy proton irradiation-induced performance degradation.

Physics↗
DOE OSTI2021

Stabilization of ferroelectric phase of Hf 0.6 Zr 0.4 O 2 on NbN and Nb [slides]

This work demonstrated both NbN and Nb make good electrodes for stabilizing orthorhombic phase of Hf 0.6 Zr 0.4 O 2 ferroelectric films. Wake up are < 100 cycles. P r can be as high as 30 µC/cm 2 - respectively 14 and 18 µC/cm 2 here. Further, capacitance suggests an orthorhombic phase can be stabilized. Addition of a linear dielectric under modest thickness can tune the P r and reduce leakage.

36 MATERIALS SCIENCE↗
NASA NTRS1971

Characteristics of NbN Dayem bridges

NbN Dayem bridge characteristics, discussing negative resistance region, self induced subharmonic current steps, temperature dependence and microwave radiation effects

Blaugher, R. D.↗
NASA NTRS1972

Lower critical field measurements in NbN bulk and thin films.

Low-field magnetization measurements were made at 4.2 K on thin-film and bulk NbN samples by using a vibrating-sample Foner magnetometer with a 50-kG superconducting solenoid. Values of the lower and upper critical fields are calculated, using magnetization curves as the basis. The significance of the Pauli spin paramagnetism and spin-orbit scattering in these materials is discussed.

Mathur, M. P.↗
NASA NTRS1986

Room-Temperature Deposition of NbN Superconducting Films

Films with high superconducting transition temperatures deposited by reactive magnetron sputtering. Since deposition process does not involve significantly high substrate temperatures, employed to deposit counter electrode in superconductor/insulator/superconductor junction without causing any thermal or mechanical degradation of underlying delicate tunneling barrier. Substrates for room-temperature deposition of NbN polymeric or coated with photoresist, making films accessible to conventional lithographic patterning techniques. Further refinements in deposition technique yield films with smaller transition widths, Tc of which might approach predicted value of 18 K.

Thakoor, S.↗
NASA NTRS1985

High T(c) superconducting NbN films deposited at room temperature

The dc reactive magnetron sputtering process yields stoichiometric NbN films with superconducting transition temperature T(c) as high as 15.7 K on substrates as varied as glass, glazed ceramic, fused quartz, and sapphire. These films posses fcc (B1) structure and (111) texture. The most dominant factors governing the formation of the transition metal nitrides are the relative metal and nitrogen fluxes incident on the substrate and the background argon pressure (which dictates the overall reactive sites and residence times for nitrogen).

Thakoor, S.↗
NASA NTRS1991

Performance of NbN superconductive tunnel junctions as SIS mixers at 205 GHz

Small area (less than 1 sq micron), high-current-density NbN/MgO/NbN tunnel junctions with I-V characteristics suitable for high-frequency mixers have been fabricated. Mesa-geometry junctions with an area of about 1 sq micron and critical current density of 5-10 kA/sq cm are integrated with superconducting microstrip lines designed to resonate out the junction capacitance. A study was made of the mixer gain and noise performance near 205 GHz as a function of the inductance provided by the microstrip line. This has confirmed, at a high millimeter-wave frequency, values of junction capacitance of 85 fF/sq micron and recently measured values of a magnetic penetration depth of 380 nm. Mixer noise temperatures as low as 134 K at 1.5 K have been obtained for properly tuned junctions. A significant improvement in mixer performance on cooling from 4.2 K to 1.5 K was observed. Edge-geometry junctions with an area of 0.3 sq microns and critical current density of 18-25 kA/sq cm have also been fabricated. These junctions give a mixer noise temperature of 145 K at 4.2 K without the use of integrated tuning elements. These are the best results ever achieved for NbN-based SIS mixers.

Mcgrath, W. R.↗