# Presentation: 681096

## 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

**Nanoscale engineered sensors and ultra-low magnetic field metrology**

## High sensitivity magnetic sensors can have high impact  

-  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

- High sensitivity magnetic sensors can have high impact

- 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**

## Outline

-  Definition of the problem
-  Approach
-  Organization
-  Questions

## Definition of the problem

- _Noise in (magnetic) thin films resistors_
-  Johnson noise
-  Shot noise
**1/f noise ****	****thin films ****	****	******** 10****2**** nV at 1 Hz**
**magneto-resistor  ****	******** 10****4**** nV at 1 Hz**

- 50  thin film resistor

- 50  magneto-resistor

- 1/f

- 1/f

- V

- R

- I

## Magnetic nanostructure fluctuations cause 1/f noise

- Voltage (V)

- Resistance change due to fluctuation of an individual magnetic domain.
- “Random Telegraph Noise”

**Notes:**
Nuke bottom figure

## Noise level in magnetic sensors could potentiallybe reduced by factor of 100 if fluctuations are eliminated

- Honeywell HMC 1001/1002

- Typical “best” - 200 pT / Hz at 1 Hz

- Without fluctuations, this could be
- improved to 2 pT / Hz at 1 Hz

## This would enable real-time biomedical applications

- Need ~1-5 picotesla sensitivity for real time monitoring

- Cardiac magnetic signal

## Question:“Can we identify the nano-scale magnetic fluctuations that cause noise and engineer a new class of sensor that is free of these effects?”

## Answer:“Yes”

## 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

## Leverage off new results in the magneto-resistive (MR) effect

- Magnetic material

*I*

-  “Anisotropic” MR - Lord Kelvin (1857)
- => 1 % change at room temperature           at ~ 0.1 mT

- Objective
- Single, stable domain => **reduced noise by 10 - 100**
- Magnetization easier to rotate => **increased sensitivity by 10 - 50**

-  “Giant” or “Tunneling” MR
- (1988)      => 10 – 50 % change                at ~ 1 mT

- Opportunity to increase room temperature sensor performance by 100 -5000!!

## (1) Develop amorphous & nanocrystalline materials in thin film form for use as soft film

- Source: McHenry, Willard, & Laughlin, Prog. Mat. Sci. 44, 291 (1999).

## Unique NIST facility for deposition, processing, and in situ characterization of magnetic thin films

- 6 molecular beam epitaxy evaporators

- Magneto-optical Kerr studies

- Superconducting magnet for FMR studies

- X-ray photoelectron and Auger spectroscopy studies

- Electromagnet for magnetoresistance studies

- STM studies

- Neutralized beam Ar ion gun

- Unique NIST facility for deposition, processing, and *in situ *characterization of magnetic thin films

- Ultrahigh vacuum system for impurity-free films

- 9 magnetron deposition sources

## Integrate soft materials into thin film sensors

-     Amorphous alloy sense film

- Cu

- Co (pinned)

- M

- Multi-layer devices
- “Giant-MR”

- Tunneling devices
- “Tunneling-MR”

- Al2O3

- M

-  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

- Single-layer devices
- “anisotropic
- magneto-resistance”

- Co (pinned)

## (2a) Low frequency, single-layer magnetic imaging

- Currently, SEMPA can measure a material’s static magnetic nano-structure in ambient magnetic fields.

- 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.

- |M|

- 5 m

**M**

## (2b) Time resolved multi-layer magnetic imaging

-  Ballistic electron magnetic microscopy (BEMM)
-  Images the magnetization of buried, soft layers

- Magnetic films

- spacer

- I

## BEMM shows evidence of thermal fluctuations at defects

-  Will correlate these types of fluctuations with noise in active devices.

## Time resolved BEMM imaging system

- B field

- B field

- Stage

- I DC

- H APP

-  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.

- Calibrated
- Nano-RF-probe

## (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)

## (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, ...

**Notes:**
Aren’t we rethinking the FIB based on Rippard’s comments

## 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

**Notes:**
Aren’t we rethinking the FIB based on Rippard’s comments

## 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.
- => Improved localization and real-time monitoring capability

- 

- Distributed magnetic sensor array

## Triggered, time resolved MRI

- H Wen, NHLBI/NIH

-  Catheter run to heart
- Trigger stimulates contraction
-  MRI sampled at  25 ms/frame
-  1.5 mm resolution of myocardial    	mechanics
-  Invasive
-  Time consuming
-  Doesn’t study arrhythmia’s
-  Doesn’t give electrical circuit   	information

## “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

## Blood flow visualization and measurements based on tracking magnetic particles

- H Wen, NHLBI/NIH

- 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.

## Combination of the three opens a wide field of clinical and basic research tools in the heart

- Imaging of MCG activity

- Imaging of blood flow

- Imaging of myocardial mechanics

- Electro-mechanical
- coupling

- Ischemic injury causes electrical abnormalities

- Supply and demand
- Injury causes
- mechanical changes

- How does ischemic injury lead to dead circuits in the heart?

## Iron-oxide labeled stem cells

- H Wen, NHLBI/NIH

- 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

## Sensitivity needs for critical applications

- 1 fT

- 1 nT

- 1

- 100

- 10,000

- 0.01

- 0.0001

- Frequency (Hz)

- Detector Noise Floor

- 1 pT

- “best” MR

**Forensic &**
**industrial**

**Border**
**defense****&**
**battlefield**
**applications**

**Magneto-**
**cardiography**
**& bead tracking**

**Magneto-**
**encephalography**

**Notes:**
Y axis is not field, and not s/n, maybe noise?

## ARL

- Motivation

** ****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***

*Networked Microsensor Thrust*

- Distributed arrays of complementary battlefield sensors & telemetry:
-  Acoustic
- Seismic
- Magnetic

***The Army is developing a “technology tool box” for future small, low cost sensors***

## Pathogen & bio-hazard detection is critical for both    				health care & homeland security

- Pathogen & bio-hazard detection is critical for both    				health care & homeland security

- MR sensor

- Magnetic
- beads

## Bead Array Counter (BARC)

-  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

## Homeland security – nano-sensor arrays would be a breakthrough technology for forensics

- Example analog audio tape

- Problem: existing prototypes rely on single, low sensitivity scanned probes

- Write head
- stop event

- Audio test tones

## Single & multi-element magnetic field sensors

- Magnetic scanner
- over an integrated circuit

- Magnetic field

- Current map

-  Need higher sensitivity => quiescent power consumption and signals

## 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 SFA’s from external 	and internal sources
-  Presentations from NIST researchers describing progress
-  Planning session for focusing and directing research

## Flow chart of device development

- soft magnetic
- properties

- Time resolved
- SEMPA

- Philosophy/
- theory

- Processing

- Analysis

- Applications

- Time resolved
- BEMM

- Single layer
- device fabrication

- Multilayer layer
- device fabrication

- Micromagnetic
- modeling

- Active device characterization
- Trimming and noise measurements

## There are many customers & collaborators that will be benefit from these developments

-  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

## Summary

-  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.

**Goal: To develop the metrology of nanomagnetics necessary to enable a new class of magnetic sensors**

**Metrology matters**

## 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 < 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

## Budget