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Nanoscale Electrodynamics Measurements with Radical New Forms of Microwave Microscopy. Steven Anlage, Michael Fuhrer. ONR AppEl Review 26 August, 2010. Work funded by ONR and DOE. UMD Microwave Microscopy Group. Faculty: Steven Anlage Michael Fuhrer Graduate Student Tamin Tai

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nanoscale electrodynamics measurements with radical new forms of microwave microscopy
Nanoscale Electrodynamics Measurements with Radical New Forms of Microwave Microscopy

Steven Anlage, Michael Fuhrer

ONR AppEl Review

26 August, 2010

Work funded by ONR and DOE

slide2

UMD Microwave Microscopy Group

Faculty:

Steven Anlage

Michael Fuhrer

Graduate Student

Tamin Tai

Undergraduate Students

John Abrahams

Post-Doc

Behnood Ghamsari

Collaborators:

Alexander Zhuravel, Kharkov, Ukraine

Alexey Ustinov, Karlsruhe Inst. Tech.

Dragos Mircea, Western Digital

Vladimir Talanov, Neocera

Lance Cooley, FermiLab

Gigi Ciovatti, Jefferson Lab

Funding: ONR AppEl and DOE

slide3

All-electric and munitions-free ships require new materials technologies

Superconducting RF cavities for free-electron lasers

Superconducting tapes and wires for compact, efficient motors

‘Quantum’ materials with novel properties

slide4

Motivations

The development of new materials with new functionalities depends

on establishing structure / property relationships

New forms of microscopy help to accelerate the development of

these novel materials

Development of new Nano-Electromagnetic devices requires

understanding of electrodynamics at the nano-scale

We are developing two new types of microscopy to establish structure / property

relations at high frequency and low temperatures, under conditions where

the materials will be utilized

Near-Field Microwave Microscopy of Nb for SRF applications

Laser Scanning Microscopy of superconductors and novel electronic materials

slide5

Localized Defects on Nb SRF Cavities

These defects can lead to hot spots on accelerator cavity within operating frequency region (1-2 GHz)

However, many defects are benign. How to distinguish the ‘good’ ones from the ‘bad’ ones?

Grain

Boundaries

welds, oxidation,hydrogen poisoning

welds, oxidation,hydrogen poisoning

T. Bieler

Mich. State Univ.

500 x 200 mm pit

http://www.helmholtz-berlin.de/events/srf2009/programs/tutorials_de.html

slide6

APPROACH

Near-Field Microwave Microscopy*

GOAL: To establish links between microscopic defects and

the ultimate RF performance of Nb at cryogenic temperatures

APPROACH:

1) Stimulate Nb with a concentrated and intense RF magnetic field

  • Drive the material into nonlinearity (nonlinear Meissner effect)
      • Why the NLME? It is very sensitive to defects…
  • Measure the characteristic field scale for nonlinearity: JNL

4) Map out JNL(x,y) → relate to previously-characterized defects

*S. M. Anlage, V. Talanov, A. Schwartz, "Principles of Near-Field Microwave Microscopy," in Scanning Probe Microscopy: Vol. 1,

edited by S. V. Kalinin and A. Gruverman (Springer-Verlag, New York, 2007), pages 215-253.

slide7

Nonlinear Near-Field Microscopy of Superconductors

P3f : NLME Nonlinearities

Pinput

sample surface

coaxial probe

K(x,y)

loop

Superconductor

Current distribution

geometry factor

Induce high m0K ~ 200 mT (Hc of Nb)

K(x,y) sharply peaked in space

► Better spatial resolution

D. Mircea, S. Anlage, Phys. Rev. B 80, 144505 (2009) + references therein

slide8

What do We Learn About the Superconductor?

on YBCO

P3f(x)

JNL(x)

Position

x

Defect 1

Defect 2

Measured at T=60 K (below Tc of YBCO)

Phys. Rev. B 72, 024527 (2005)

slide9

How to Generate Strong RF Magnetic Fields?

Cu coils

Permalloy shields

m

~2

m

Write Pole

Read Sensor

2 mm

Air bearing surface

RF Magnetic Fields

Permalloy

Magnetic Write Head

Magnetic recording heads provide

strong and localized BRF

Side View

SEM picture of the magnetic write head gap

Bottom View

BRF ~ 1 Tesla (in gap)

Gap

Lateral size ~ 100 nm x few-100 nm

Reference: IEEE Trans Magn. Vol . 37, No. 2 pp.613-618 2001

slide10

Experimental Setup

RF Coil

on slider

Superconductor

Goals: BRF ~ 200 mT

Lateral size ~ 100 nm

We need higher BRF and strongly localized field distributions

Probe

Head Gimbal Assembly (HGA)

slide11

Measurements on Superconductors

At a fixed location on MgB2 film

Excited power: 12 dBm; Excited frequency: 3.75GHz

Noise floor

MgB2 Film (25nm)/SiC

A peak in P3f(T) near the Tc of MgB2 is found.

No other P3f peak is found below Tc. It implies there is no defect near this measurement point.

Samples come from Prof. Xiao-Xing Xi Temple University, Philadelphia, PA

slide12

Tc

Noise floor

Measurements on Tl2Ba2CaCu2O8 Film

At a fixed location

Excited power: 6 dBm

Excited frequency: 3.75 GHz

Vortex or defects/ grain boundary contribution

slide13

Head Gimbal Assembly (HGA)

Top surface of bulk Nb (thickness: 0.1 inch)

Pit on Nb

Copper cold plate

Challenges for Measurements on Nb bulk materials

  • Probes may cause localized heating of Nb samples.
  • Temperature of cold plate reaches 4.2K but Nb surface remains warmer. (Next step: thermal grounding of probe and positioner)
  • Magnetic write head probe is still too far away from the superconductor surface.(Next step: nm-level positioning control)
slide14

Photolithography Result (thanks to Dr. Cihan Kurter)

Current Work---Micro Loop Design

Simulation Data from HFSS (Gregory Ruchti )

Micro loop design can enhance the current geometry factor G and increase our spatial resolution.

slide15

Laser Scanning Microscopy:

Principle of the measurement

modulated

laser

resonator transmission

laser OFF

Pout

|S21(f0)|2

Pin

laser ON

|S21(f0)|2

f

f0

co-planar resonator f0 ~ 5.2 GHz

D|S12|2 ~ [lJRF(x,y)]2 A dl

Local heating produces a change in

transmission coefficient proportional

to the local value of JRF2

J. C. Culbertson, et al. J.Appl.Phys. 84, 2768 (1998) @ NRL

A. P. Zhuravel, et al., Appl.Phys.Lett. 81, 4979 (2002)

slide16

Typical Spatial Profile of RF Photoresponse

Along a Lateral Cross Section of the Resonator Strip

YBCO/LaAlO3

CPW Resonator

T = 79 K

P = - 10 dBm

f = 5.285 GHz

fmod = 99.9 kHz

1 x 8 mm scan

P1 = in-plane rotated grain

P2 = crack in YBCO film

P3 = LAO twin domain blocks

Wstrip = 500 mm

slide17

Imaging of a YBa2Cu3O7 / LaAlO3 Resonator

Optical reflectivity

DC Photoresponse

Low-T RF PR

“PR” = Photo-response

Room Temp. Thermoelectric PR

A. Zhuravel, et al., J. Appl. Phys. 108, 033920 (2010)

slide18

Corner “A2” Detail of YBCO / LAO Resonator

Optical Reflectivity

RF PR

A. Zhuravel, et al., J. Appl. Phys. 108, 033920 (2010)

25 mm

slide19

Laser Scanning Microscope @ UMD

LSM in Karlsruhe, Germany

UMD Microscope: configured for bulk superconductors, closed cycle refrigerator

JLab Microscope: built inside a Nb SRF cavity

slide20

Current and Future Work

Complete the UMD Laser Scanning Microscope

Closed cycle refrigerator for week-long runs

Ukraine collaborator (Zhuravel) visits to commission the microscope

Preliminary results from Karlsruhe collaboration

RF Defect Imaging in bulk Nb

slide21

Collaborative Work on

Nb Cavity Laser Scanning Microscope at Jefferson Lab

Built by G. Ciovatti and P. Kneisel @ JLab

slide22

Nano Materials

Growth of aligned carbon nanotubes

Wiring of carbon nanotubes

Pt

3 CNTs

Enrique Cobas, M. Fuhrer

Cr

CNT Schottky diodes

E. Cobas, Appl. Phys. Lett. 93, 043120 (2008)

Diodes rectify for frequencies up to 40 GHz

Estimates: fcutoff ~ 100’s of GHz in some devices

slide23

High Resolution Microwave Microscopy

Scanning Tunneling Microscope

(STM)- Assisted

Microwave Microscopy

Atif Imtiaz, et al., Appl. Phys. Lett. 90, 143106 (2007)

Atif Imtiaz, et al., J. Appl. Phys. 97, 044302  (2005)

STM Topography

(constant current)

Cx

Rx

Simple circuit model of

probe-sample interaction

slide24

Experiments

Prepare nanotubes

suspended

over a trench

A100 mm-long

CNT should resonate

at 10 GHz

Excite resonance with

microwave microscope

or in a CPW geometry

Luttinger liquid physics

slide25

Intrinsic Inhomogeneity in Correlated-Electron Materials

Electron-Hole Puddles

in Graphene

Scanning SET microscopy

2 mm x 3 mm, 0.3 K

J. Martin, Nature Physics (2008)

Electron nematic phase in Co-Fe-As

Chuang, Science (2010)

slide26

Conclusions

Near-Field Microwave Microscopy

  • A magnetic write head, which can generate strong RF fields on sub-mm length
    • scales, is successfully integrated into the near field microwave microscope
    • operating at cryogenic temperatures.
  • A clear reproducible nonlinear response signal from TBCCO and MgB2 are
  • obtain by this magnetic write head probe.
  • Further improvements will enable SRF defect microscopy on bulk Nb surfaces.

Laser Scanning Microscopy

The LSM gives unique insights into structure / property relations at ~ mm length scales

Preliminary data on bulk Nb resonators is encouraging

Microscopy-related ongoing research efforts:

Purely evanescent probe: Time-reversed microscopy to eliminate far-field radiation,

S. M. Anlage, et al., Acta Physica Polonica A 112, 569 (2007)

Use of Metamaterials to enhance evanescent waves and resolution,

M. Ricci, et al., Appl. Phys. Lett. 88, 264102 (2006)