Nanoscale engineered sensors and ultralow magnetic field metrology

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Nanoscale engineered sensors and ultra-low
magnetic field metrology
Coordinator David Pappas - EEEL
Principal Investigators Bill Egelhoff -
MSEL John Unguris - PL Steve Russek,
Pavel Kabos - EEEL Michael Donahue -
ITL Collaborators Bill Rippard -
EEEL Mark Stiles - PL Robert McMichael -
MSEL
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High sensitivity magnetic sensors can have high
impact

• Health care
• Non-invasive medical evaluation
• - Magneto-cardiography (MCG)
• - Magnetic bead tracking of blood flow stem
  cells
• Homeland security
• Magnetic tag detection ? pathogen sensors
• Low power distributed sensors
• Information technology knowledge management
• Non-destructive failure analysis
• Magnetic data storage and random access memories

Development of the metrological tools that enable
a high sensitivity, low noise sensor will have a
significant impact on security, industry, and
quality of life. Metrology matters
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Outline

• Definition of the problem
• Approach
• Organization
• Questions

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Definition of the problem

• Noise in (magnetic) thin films resistors
• Johnson noise
• Shot noise
• 1/f noise thin films ? 102 nV at 1 Hz
• magneto-resistor ? 104 nV at 1 Hz

I
V
R
50 ? magneto-resistor
50 ? thin film resistor
1/f
1/f
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Magnetic nanostructure fluctuations cause 1/f
noise
Resistance change due to fluctuation of an
individual magnetic domain. Random Telegraph
Noise
Voltage (mV)
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Noise level in magnetic sensors could
potentiallybe reduced by factor of 100 if
fluctuations are eliminated
Typical best - 200 pT / ?Hz at 1 Hz
Without fluctuations, this could be improved to
2 pT / ?Hz at 1 Hz
Honeywell HMC 1001/1002
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This would enable real-time biomedical
applications
Cardiac magnetic signal
Need 1-5 picotesla sensitivity for real time
monitoring
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QuestionCan we identify the nano-scale
magnetic fluctuations that cause noise and
engineer a new class of sensor that is free of
these effects?
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AnswerYes
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Approach multi-level magnetic metrology
development

• Synthesize novel nano-structured materials to
  reduce fluctuations and increase response.
• ? Fabricate devices with new materials.
• Dynamic imaging to understand and eliminate noise
  sources.
• ? At both the materials and device level.
• Model nano-magnetic behavior, compare and
  feedback to (1) and (2).
• ? Understand fluctuations in both materials and
  devices
• Apply new sensors to ultra-low field metrology
  and imaging.

Results - Potential high payoff at each
individual level - High risk, very high payoff
if they all succeed
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Leverage off new results in the magneto-resistive
(MR) effect

• Anisotropic MR - Lord Kelvin (1857)
• gt 1 change at room temperature at
  0.1 mT

Magnetic material
I

• Giant or Tunneling MR
• (1988) gt 10 50 change
  at 1 mT

• Objective
• Single, stable domain gt reduced noise by 10 -
  100
• Magnetization easier to rotate gt increased
  sensitivity by 10 - 50

Opportunity to increase room temperature sensor
performance by 100 -5000!!
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(1) Develop amorphous nanocrystalline materials
in thin film form for use as soft film
Source McHenry, Willard, Laughlin, Prog. Mat.
Sci. 44, 291 (1999).
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Unique NIST facility for deposition, processing,
and in situ characterization of magnetic thin
films
X-ray photoelectron and Auger spectroscopy studies
STM studies
Superconducting magnet for FMR studies
Ultrahigh vacuum system for impurity-free films
Magneto-optical Kerr studies
9 magnetron deposition sources

Neutralized beam Ar ion gun
6 molecular beam epitaxy evaporators
Electromagnet for magnetoresistance studies
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Integrate soft materials into thin film sensors

• Layer-by-layer fabrication of magnetic films
  informed by metrology
• Optimize deposition, annealing, and processing
  conditions
• Utilize in situ electrical and magnetic
  measurements for process feedback
• Optimize materials for application in specific
  device designs

Amorphous alloy sense film
Tunneling devices Tunneling-MR
Multi-layer devices Giant-MR
Single-layer devices anisotropic magneto-resista
nce
Co (pinned)
Co (pinned)
Al2O3
Cu
M
M
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(2a) Low frequency, single-layer magnetic imaging

• Scanning electron microscopy with polarization
  analysis (SEMPA)

M
Currently, SEMPA can measure a materials static
magnetic nano-structure in ambient magnetic
fields.
5 mm
M
We will modify SEMPA to enable imaging of wired,
electrically active devices in low or controlled
magnetic fields.
The goal is to correlate nanoscale magnetic
fluctuations with resistance noise in active,
single-layer devices.
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(2b) Time resolved multi-layer magnetic imaging

• Scanned probe microscope over multi-layer
  magnetic structure
• Ballistic electron magnetic microscopy (BEMM)
• Images the magnetization of buried, soft layers

I
Magnetic films
spacer
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BEMM shows evidence of thermal fluctuations at
defects
Will correlate these types of fluctuations with
noise in active devices.
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Time resolved BEMM imaging system
Calibrated Nano-RF-probe
I DC
H APP
B field
Stage
B field

• Applicable to multi-layer giant- and tunneling-
  magneto-resistors
• Extends time resolution from low frequency 1/f
  noise up to resonant frequencies (3 GHz) with
  high frequency calibrated probes on scanning
  tunneling microscope.

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(3) Micromagnetic modeling

• We will model real devices with disorder, thermal
  fluctuations, and dynamics on broad range of time
  scales.
• Determine physically correct method of
  introducing thermal fluctuations
• By mapping energy landscapes, determine
  dynamics out to 1 s
• Include effects of current flow (self fields and
  spin transfer)
• Model noise sources and help design materials
  and shapes for ultra low noise sensors
• Integrate code in usable, packaged form (OOMMF)

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(4) We will fabricate nano-engineered low noise
devices

• Target 1 to 5 pT/?Hz at 1 Hz noise level
• Build individual sensors and arrays in various
  configurations
• We will test devices in single and distributed
  sensor applications
• Health care work directly with NIH in targeted
  areas
• Homeland security collaborating with FBI, NSA,
  NARA, NRL
• Information technology transfer technology,
  Intel, Seagate,

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Reduced noise

• Decoupled structural and magnetic properties
  using soft amorphous and nano-crystalline
  materials
• ? Reduce anisotropy dispersion
• Trimmed shape of the sensors to reduce dipole
  energy
• ? Single domain ground state

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Integrate sensors into real-time metrology systems
?

• Configure sensors in close proximity and with
  desired geometry.
• Localize source by inverting the fields.
• Work with existing myocardial knowledge and MRI
  imaging techniques to create electrical circuit
  model.
• gt Improved localization and real-time monitoring
  capability

Distributed magnetic sensor array
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Triggered, time resolved MRI

• Catheter run to heart
• Trigger stimulates contraction
• MRI sampled at 25 ms/frame
• 1.5 mm resolution of myocardial mechanics
• Invasive
• Time consuming
• Doesnt study arrhythmias
• Doesnt give electrical circuit information

H Wen, NHLBI/NIH
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Real-time magneto-cardiography with 1 cm
localization would have revolutionary diagnostic
impact Bob Balaban, Director National
Heart, Lung, and Blood Institute National
Institutes of Health
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Blood flow visualization and measurements based
on tracking magnetic particles
Distribution of 12 micron intra-vascular
particles shown in a transverse slice slice of
the organ Captured at the arterial branching
points of the capillaries. 5-8 micron magnetic
particles will be able to move through the
capillary bed with erythrocytes.
The ability to track these particles at high
spatial precision will provide an unprecedented
wealth of information on blood flow in every
organ of the body.
H Wen, NHLBI/NIH
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Combination of the three opens a wide field of
clinical and basic research tools in the heart
Ischemic injury causes electrical abnormalities
Imaging of MCG activity
Imaging of blood flow
Supply and demand Injury causes mechanical
changes
Electro-mechanical coupling
Imaging of myocardial mechanics
How does ischemic injury lead to dead circuits in
the heart?
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Iron-oxide labeled stem cells
Monitor movement of cells in-vivo with arrays of
magnetic sensors Monitor lifetime of
cells Monitor progeny of cells
The ability to monitor stem cell delivery
non-invasively is crucial to stem cell therapy
research, which in turn is a revolution in
medicine if successful. Han Wen, P.I.,
NHLBI/NIH
H Wen, NHLBI/NIH
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Sensitivity needs for critical applications
Forensic industrial
1 nT
Border defense battlefield applications
Magneto- cardiography bead tracking
best MR
Detector Noise Floor
1 pT
Magneto- encephalography
1 fT
1
100
10,000
0.0001
0.01
Frequency (Hz)
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ARL
Motivation
Networked Microsensor Thrust

• Army program for network of unattended
• ground sensors to increase battlefield awareness
• Low-cost, high-sensitivity, low-power magnetic
• sensors are planned to be part of a suite of
  sensors
• Network will provide a cost-effective way of
• detecting targets over large areas and may
  minimize
• the need for land mines.

Vision
Distributed arrays of complementary battlefield
sensors telemetry Acoustic Seismic Magnetic
The Army is developing a technology tool box
for future small, low cost sensors
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Pathogen bio-hazard detection is critical for
both health care homeland security
Magnetic beads
MR sensor
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Bead Array Counter (BARC)

• Problem Lethal low level contamination may be
  missed
• Nanoscale arrays can provide single bead
  (molecule) sensitivity using sensitive magnetic
  sensors
• Greater sensitivity and nano-scale detection are
  important for this technology to succeed.
• Dr. L. Whitman, Naval Research Lab

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Homeland security nano-sensor arrays would be a
breakthrough technology for forensics
Problem existing prototypes rely on single, low
sensitivity scanned probes
Example analog audio tape
Audio test tones
Write head stop event
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Single multi-element magnetic field sensors
Magnetic scanner over an integrated circuit
Magnetic field
Current map
Need higher sensitivity gt quiescent power
consumption and signals
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Project Coordination

• Organizational Board
• Coordinator Dave Pappas
• Nanoscale materials metrology Bill Egelhoff
• Nanomagnetic metrology John Unguris
• Nanoscale device metrology Steve Russek
• Nanoscale magnetic modeling Mike Donahue
• Monthly Board meeting to review progress
• Quarterly video teleconference for all
  participants with highlights
• Yearly magnetic sensors workshop - two day event
• Invited covering magnetism applications in SFAs
  from external and internal sources
• Presentations from NIST researchers describing
  progress
• Planning session for focusing and directing
  research

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Flow chart of device development
Micromagnetic modeling
Philosophy/ theory
materials with soft magnetic properties
Processing
Time resolved SEMPA
Time resolved BEMM
Single layer device fabrication
Multilayer layer device fabrication
Analysis
Active device characterization Trimming and noise
measurements
Applications
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There are many customers collaborators that
will be benefit from these developments

• Government laboratories
• FBI, NSA, NTSB, NRL, NIST
• Industry
• Sensor fabrication
• Nonvolatile Electronics, San Diego Magnetics,
  Honeywell
• Integrated sensor systems
• Quantum Magnetics, TPL, Inc.
• Data storage Seagate, IBM, Headway,
• Semiconductors Intel, HP
• Academia centers and researchers

Customers will be able to make revolutionary
improvements in magnetic field sensing
applications
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Summary
Goal To develop the metrology of nanomagnetics
necessary to enable a new class of magnetic
sensors

• Pioneer the development of new metrologies for
  nanomagnetic devices.
• Strong potential impact on all four Strategic
  Focus Areas
• Metrology development and sensor demonstration
  will enable a wide range of applications.
• Our proposal coordinates the expertise of four
  strong magnetics groups for a high payoff result
  high sensitivity, low noise magnetic field
  sensors.

Metrology matters
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Milestones

• Materials - nanoengineered soft magnets
• Fabrication of soft, nano-crystalline materials
  FY04
• Incorporation into single layer sensors FY05
• Incorporation into multi-layer devices FY06
• Imaging
• Fluctuations in quiescent single layer devices
  FY04
• Complete constructuion of trBEMM FY04
• Fluctuations in active multilayer devices up to
  1 kHz FY05
• Correlation between nanostructure defects and
  noise spectra FY06
• Fluctuations in multilayer devices up to 1 GHz
  FY07
• Modeling
• Nanoscale thermal modeling (LLG/Langevin) FY04
• Long-scale thermal modeling (energy landscape) -
  FY06
• Devices
• TMR sensors with 10 mV/Oe and lt 5nV?Hz noise at
  10 Hz -FY04
• High resolution magnetic tape imaging with
  nano-arrays FY05
• Compatibility with single molecule bio-analysis
  bead array counters FY05
• Demonstrate capability of bead tracking FY06
• Demonstrate capability of magneto-cardiograpy
  FY07

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Budget