A5056845229- Superconducting and THz Device Technology
- Physics of Superconductivity and Magnetism
- Magnetic properties of thin films
- Advanced Memory and Neural Computing
- Ferroelectric and Negative Capacitance Devices
- Magnetic Properties and Applications
- Microwave Engineering and Waveguides
- Semiconductor Quantum Structures and Devices
- Photonic and Optical Devices
- Advanced Semiconductor Detectors and Materials
- Radio Astronomy Observations and Technology
- Semiconductor materials and devices
- Spectroscopy and Laser Applications
- Thermal Radiation and Cooling Technologies
- Calibration and Measurement Techniques
- Superconductivity in MgB2 and Alloys
- Atmospheric Ozone and Climate
- Quantum and electron transport phenomena
- Non-Destructive Testing Techniques
- Infrared Target Detection Methodologies
- Magnetic and transport properties of perovskites and related materials
- Characterization and Applications of Magnetic Nanoparticles
- Terahertz technology and applications
- Particle accelerators and beam dynamics
- Radio Frequency Integrated Circuit Design
IBM Research - Thomas J. Watson Research Center
2006-2016
IBM (United States)
1999-2016
Yale University
1993-2004
Goddard Space Flight Center
2003
Jet Propulsion Laboratory
1997-2002
California Institute of Technology
1995-1999
Space Micro (United States)
1997-1999
Massachusetts Institute of Technology
1987-1990
MIT Lincoln Laboratory
1987-1988
Spin torque switching is investigated in perpendicular magnetic tunnel junctions using Ta∣CoFeB∣MgO free layers and a synthetic antiferromagnet reference layer. We show that the Ta∣CoFeB interface makes key contribution to anisotropy. The quasistatic phase diagram for under applied field voltage reported. Low voltages, Vc 50 ns=290 mV are obtained, range required spin random access memory. Switching down 1 ns reported, with rise speed from increased overdrive eight times greater than...
Spin-transfer torque magnetic random access memory (STT-MRAM) is one of the most promising emerging non-volatile technologies. MRAM has so far been demonstrated with a unique combination density, speed, and non-volatility in single chip, however, without capability to replace any mainstream memory. In this paper, we demonstrate basic physics spin switching 20 nm diameter tunnel junctions perpendicular anisotropy materials. This deep scaling clearly indicates STT device itself may be suitable...
Recently developed magnetic tunnel junctions with full perpendicular magnetization that are spin-torque switchable allow for quantitative comparison of switching statistics a macrospin model. For typical devices above 50 nm in lateral size, the suggests presence subvolume excitations which often dominate process and degrade efficiency. A simple model spin-torque-driven is presented to account experimental observations. The origin thermal excitation traced competition between fluctuation...
It is convenient to define the spin-torque switching efficiency in nanostructured magnetic tunnel junctions as ratio between free-layers thermal activation barrier height ${E}_{b}$ and threshold current ${I}_{c0}$. Recent device exploration has led occasional observations of induced that exceeds macrospin limit by a factor 2--10. In this paper we examine possible origins for such enhancement, materials properties may allow full realization enhancements.
In this paper, we report the first demonstration of CMOS-integrated racetrack memory. The devices measured are complete memory cells integrated into back end line IBM 90 nm CMOS. We show good integration yield across 200 mm wafers. With magnetic field-assist, demonstrate current-driven read and write operations on within a 256-cell array.
Bit error rates below 10 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$^{-11}$</tex> </formula> are reported for a 4-kb magnetic random access memory chip, which utilizes spin transfer torque writing on tunnel junctions with perpendicular anisotropy. Tests were performed at wafer level, and error-free operation was achieved ns write pulses all nondefective bits during 66-h test. Yield in the array...
A three-terminal spin-torque-driven magnetic switch is experimentally demonstrated. The device uses nonlocal spin current and accumulation as the main mechanism for current-driven switching. It separates current-induced write operation from that of a tunnel junction based read. only passes through metallic structures, improving reliability. structure makes efficient use lithography capabilities, important robust process integration.
For CoFeB∕MgO-based magnetic tunnel junctions, the switching probability has an unusual dependence on bias voltage V and field H for pulse durations t long enough to allow thermally activated reversal. At high junction close 1V, of in spin-torque-driven switches sometimes appears decrease. This is shown be due a backhopping behavior occurring at bias, it asymmetric voltage, being more pronounced direction antiparallel-to-parallel spin-torque switch, i.e., electrons tunneling into free layer....
We describe a 1 THz quasioptical SIS mixer which uses twin-slot antenna, an antireflection-coated silicon hyperhemispherical lens, Nb/Al-oxide/Nb tunnel junctions, and aluminum normal-metal tuning circuit in two-junction configuration. Since the operates substantially above gap frequency of niobium (ν≳2Δ/h∼700 GHz), normal metal is used place to reduce Ohmic loss. The response device was measured using Fourier transform spectrometer agrees reasonably well with theoretical prediction. At 1042...
The noise performance of a Nb hot-electron bolometer mixer at 2.5 THz has been investigated. devices are fabricated from 12-nm-thick film, and have 0.30 μm×0.15 μm in-plane size, thus exploiting diffusion as the electron cooling mechanism. rf coupling was provided by twin-slot planar antenna on an elliptical Si lens. experimentally measured double sideband temperature receiver low 2750±250 K with estimated ≈900 K. bandwidth derived both IF impedance measurements ≈1.4 GHz. These results...
We report data from 4-kbit spin torque MRAM arrays using tunnel junctions (TJs) with magnetization perpendicular to the wafer plane. show for first time switching distribution of junctions. The percentage voltage width, σ(V <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</inf> )/<V > = 4.4%, is sufficient yield a 64 Mb chip. Furthermore we probability curves down error probabilities 5×10 <sup...
The OH radical is an important player in known ozone depletion cycles; however, due to its location the atmosphere, it must be studied from either a balloon or spaceborne platform. For long-term mapping over large portions of earth, platform most desirable. NASA's Earth Observing System Microwave Limb Sounder instrument slated house 2.5-THz Schottky-diode receiver for such measurements. In this paper, we describe design, fabrication, and testing front end. Measured double-sideband (DSB)...
The results of measurements the refractive index and power attenuation coefficient Zitex at 290, 77, 4 K in spectral region from 1 to 1000 microm are presented. is a porous Teflon sheet with filling factor approximately 50% manufactured several varieties as filter paper. found be an effective IR block, thin (200-microm) sheets transmitting less than 1% 1-50-microm range while attenuating < or = 10% wavelengths longer 200 microm. Some variation cutoff wavelength seen, tending...
We have demonstrated a robust magnetic tunnel junction (MTJ) with resistance-area product RA=8 Ω—μm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> that simultaneously satisfies the statistical requirements of high tunneling magnetoresistance TMR ≫ 15σ(R <inf xmlns:xlink="http://www.w3.org/1999/xlink">p</inf> ), write threshold spread σ(Vw)/≪Vw≫ ≪7.1%, breakdown-to-write voltage margin over 0.5V, read-induced disturbance rate below 10...
CoFeB-based magnetic tunnel junctions with perpendicular anisotropy are used as a model system for studies of size dependence in spin-torque–induced switching. For integrated solid-state memory applications, it is important to understand the and electrical characteristics these they scale junction size. Size-dependent energy, switching voltage, apparent damping, field systematically compared devices different materials fabrication treatments. Results reveal presence sub-volume thermal...
The prospects of a YBa2Cu3O7−δ hot-electron bolometer mixer for THz heterodyne receiver are discussed. modeled device is submicron bridge made from 10-nm-thick film on high thermal conductance substrate. performance expected this analyzed in the framework two-temperature model which includes heating both electrons and lattice. Also, contribution phonon diffusion through substrate to normal metal contacts evaluated. intrinsic conversion efficiency noise temperature have been calculated as...
We describe quasi-optical SIS mixers operating in the submillimeter band (500-750 GHz) which have very low noise, around 5 h/spl nu//k/sub B/ for double-sideband receiver noise temperature. The use a twin-slot antenna, Nb/Al-Oxide/Nb tunnel junctions fabricated with optical lithography, two-junction tuning circuit, and silicon hyperhemispherical lens novel antireflection coating to optimize efficiency. flown using these on Kuiper Airborne Observatory, detected transition of H/sub 2//sup 18/O...
We present an experimental study of the time scales for various quasiparticle processes in a superconducting single photon spectrometer. Processes studied include recombination, diffusion, trapping, tunneling, and energy redistribution. Experiments were performed with double junction, imaging x-ray detector whose charge output provides measure energy. Time are extracted simple model values several parameters, including diffusion constant recombination time, found to differ from theoretical...
We report on the development of low-noise quasi-optical SIS mixers for frequency range 400-850 GHz. The utilize twin-slot antennas, two-junction tuning circuits, and Nb-trilayer junctions. Fourier-transform spectrometry has been used to verify that response devices is well predicted by computer simulations. GHz band can be covered with four separate fixed-tuned mixers. measure uncorrected double-sideband receiver noise temperatures around 5h/spl nu//k/sub B/ 700 GHz, better than 540 K at 808...
A compact, narrow-linewidth, tunable source of THz radiation has been developed for spectroscopy and other high-resolution applications. Distributed-Bragg-reflector (DBR) diode lasers at 850 nm are used to pump a low-temperature-grown GaAs photomixer. Resonant optical feedback is employed stabilize the center frequencies narrow linewidths DBR lasers. The heterodyne linewidth full-width half-maximum two optically locked 50 kHz on 20 ms time scale 2 MHz over 10 s; free-running have 40 90 such...
We report a systematic, comprehensive set of measurements on the dynamics and noise processes in diffusion phonon-cooled superconducting hot-electron bolometer mixers which will serve as ultralow detectors THz heterodyne receivers. The conversion efficiency output devices varying lengths were measured with radio frequency between 8 40 GHz. studied consist 100-Å-thin film Nb bridges connected to thick (1000 Å), high conductivity normal metal (Au) leads. range from 0.08 3 μm. For longer than...
The implementation of magnetic random access memory (MRAM) hinges on complex film stacks and several critical steps in back-end-of-line (BEOL) processing. Although intended for use conjunction with silicon CMOS front-end device drivers, MRAM performance is not limited by technology. We report here a novel test site design an associated thin-film process integration scheme which permit relatively inexpensive, rapid characterization the elements fabrication. incorporates circuitry consistent...
We report on the development of a quasioptical Nb hot-electron bolometer mixer for 2.5 THz heterodyne receiver. The devices are fabricated from 12 nm thick film, and have 0.30 /spl mu/m/spl times/0.15 mu/m in-plane size, thus exploiting diffusion as electron cooling mechanism. rf coupling was provided by twin-slot planar antenna an elliptical Si lens. A specially designed system, using CO/sub 2/-pumped FIR laser local oscillator (LO), with hot/cold loads enclosed in vacuum to avoid...
We present a theory and measurements of noise mechanisms in superconducting tunnel-junction detectors used as single-photon spectrometers. These result from incomplete cooling the excited quasiparticles electrode. Due to cooling, only fraction initially created charge is collected by tunneling. Additional effects include reduced dynamic resistance, voltage dependence integrated charge, increased statistical broadening signal. demonstrate these our device, show that they explain measured...