INFM – National Research Center – Modena - ItalyINFM – National Research Center – Modena - Italy

Alessandro di Bona (MO)Alessandro di Bona (MO)

Marco Liberati (MO)Marco Liberati (MO)

Paola Luches* (MO)Paola Luches* (MO)

Sergio Valeri (MO)Sergio Valeri (MO)

Gian Carlo Gazzadi (MO)Gian Carlo Gazzadi (MO)

Paolo Vavassori (FE)Paolo Vavassori (FE)

Diego Bisero (FE)Diego Bisero (FE)

* researcher position supported by this FIRB project* researcher position supported by this FIRB project

FIRB: Microsistemi basati su materiali magnetici innovativi strutturati su scala nanoscopicaFIRB: Microsistemi basati su materiali magnetici innovativi strutturati su scala nanoscopica

Nanopatterned Fe filmsNanopatterned Fe films

INFM – National Research Center – Modena - ItalyINFM – National Research Center – Modena - Italy

the Fe/MgO systemthe Fe/MgO systemepitaxial growth lattice mismatch < 3.5%epitaxial growth lattice mismatch < 3.5%easy substrate preparation (cleavage in air)easy substrate preparation (cleavage in air)no interaction with the substrate < 0.02 eno interaction with the substrate < 0.02 e--/atom/atom

OO

MgMg

FeFeFeFebccbcc

MgOMgOrocksaltrocksalt(two fcc)(two fcc)

interface interface distance distance 2.30 2.30 ÅÅ

MgOMgOsubstratesubstrate

(100)(100)

10 nm Fe10 nm Fe10 nm MgO10 nm MgO

FIBFIB

free standingfree standingnanostructuresnanostructures

INFM – National Research Center – Modena - ItalyINFM – National Research Center – Modena - Italy

the Fe/MgO continuous filmthe Fe/MgO continuous filmin

tens

ity (a

.u.)

-730 -720 -710 -700binding energy (eV)

10 ML

1 ML

5 ML

3 ML

8 ML

bulk

Fe/MgOFe2p

XPSXPS

inte

nsi

ty (

a.u

.)

60 45 30 15 0polar angle (deg)

[111]

MgOazimuth [110]

MgKLL

O1s

6045 3015polar angle (deg)

[101] azimuth [100]

MgKLL

O1s

inte

nsi

ty (

a.u

.)

75 60 45 30 15 0polar angle (deg)

[101]

substrate azimuth [110]5ML FeFe2p

756045 3015polar angle (deg)

[111] substrate azimuth [100]

XPDXPD

SEISEIMgO(001)MgO(001) Fe/MgO(001)Fe/MgO(001)

LEEDLEED

MgO(001)MgO(001) Fe/MgO(001)Fe/MgO(001)

INFM – National Research Center – Modena - ItalyINFM – National Research Center – Modena - Italy

Geometry of Dual Beam FEI Strata™ DB 235

Beams work at coincidence on the sample:

FIB machining + simultaneous SEM imaging on a nanometer scale.

3 nm, 1 – 30 3 nm, 1 – 30 keVkeV

7 nm @ 30 7 nm @ 30 keVkeV

Resolution @Resolution @

Coincidence Coincidence

1 pA – 50 nA1 pA – 50 nA1 pA – 20 nA1 pA – 20 nACurrent rangeCurrent range

200 eV – 30 200 eV – 30 keVkeV

5 – 30 keV5 – 30 keVEnergy rangeEnergy range

SFEGSFEGGaGa++ LMIS LMISSource typeSource type

SEMSEMFIBFIB

High Vacuum: 5x10 - 7 mbar

FIB + SEM = dual beamFIB + SEM = dual beam

FIBFIB

SEMSEM

INFM – National Research Center – Modena - ItalyINFM – National Research Center – Modena - Italy

inside the FIBinside the FIB

suppressor & LMISextractor cap

lens 1

beam defining aperture

beam blanking

deflection octopole

lens 2

the FIB columnthe FIB column

• LMIS is a field–emission point-source.

• High brightness: hundreds of pA in sub-m beam ion-solid interactions are effective.

• Liquid wets a W needle. At the needle tip liquid faces HV and forms the Taylor cone: field ion emission starts.

• Gallium because of high surface tension and low vapor pressure at a low melting point. Durable sources

the Liquid Metal Ion Source (LMIS)the Liquid Metal Ion Source (LMIS)

INFM – National Research Center – Modena - ItalyINFM – National Research Center – Modena - Italy

FIB machining & FIB depositionFIB machining & FIB deposition

precursor gas injector

deposited metal

INFM – National Research Center – Modena - ItalyINFM – National Research Center – Modena - Italy

dual beam applicationsdual beam applications

200 nm 100 nm 50 nm

INFM – National Research Center – Modena - ItalyINFM – National Research Center – Modena - Italy

MgO/Fe/MgO micropatterningMgO/Fe/MgO micropatterning

500 500 μmμm

10 10 μmμm

INFM – National Research Center – Modena - ItalyINFM – National Research Center – Modena - Italy

micropattern characterizationmicropattern characterizationlo

g flu

ores

cenc

e in

tens

ity [a

.u.]

1086420photon energy [keV]

on the structures between the structures

Mg KO K

Fe K

Fe K

Ga K

SEMSEM

1 µm

a

b

c

heig

ht [

nm]

2.01.51.00.50.0

distance [µm]

10 nm

4.9°

16.6 nm

1.8°

zRMS = 1.2 nm

a)

b)

c)

AFMAFM

INFM – National Research Center – Modena - ItalyINFM – National Research Center – Modena - Italy

magnetic characterizationmagnetic characterization

MOKE micromagnetometerMOKE micromagnetometer

lateral resolution < 30 lateral resolution < 30 μmμm

INFM – National Research Center – Modena - ItalyINFM – National Research Center – Modena - Italy

magnetic characterizationmagnetic characterization

-1500 -1000 -500 0 500 1000 1500

HC

MR

Film Fe/MgO, patterns 4,5

Film Hard axis (0 degs)

Sig

nal I

nten

sity

(m

V)

Field (Oe)

-400 -300 -200 -100 0 100 200 300 400

Film Fe/MgO, patterns 4,5

HC

MR

Film Easy axis (45 degs)

Field (Oe)

Sig

nal I

nten

sity

(m

V)

continuous filmcontinuous film K = 4-5 K = 4-5 · 10· 1055 erg/cm erg/cm33

Fe(100)

easy

Fe(110)hard

...and no perpendicular magnetization component...and no perpendicular magnetization component

INFM – National Research Center – Modena - ItalyINFM – National Research Center – Modena - Italy

magnetic characterizationmagnetic characterization

circular dotscircular dots

-1500 -1000 -500 0 500 1000 1500

Pattern 2

Film hard axis (0 degs)

HC

MR

Field (Oe)

Sig

nal I

nten

sity

(m

V)

-400 -300 -200 -100 0 100 200 300 400

H

1 m

2 m

HC

MR

Pattern 2

Film easy axis (45 degs)

Field (Oe)

Sig

nal I

nten

sity

(m

V)

Fe(100)

easyFe(110)

hard

coercitive field larger with respect to film = coercitive field larger with respect to film = μ-magnetic μ-magnetic OKOK

INFM – National Research Center – Modena - ItalyINFM – National Research Center – Modena - Italy

magnetic characterizationmagnetic characterization

squared dots with side // to the hard axissquared dots with side // to the hard axis

-400 -300 -200 -100 0 100 200 300 400

Pattern 6

1 m

2 m

H

MR

HC

Film easy axis (45 degs)

Field (Oe)

Sig

nal I

nten

sity

(m

V)

-1500 -1000 -500 0 500 1000 1500

HC

MR

Pattern 6

Film hard axis (0 degs)

Field (Oe)S

igna

l Int

ensi

ty (

mV

)

Fe(100)

easy

Fe(110)hard

different shape anisotropy causes even larger cohercitive fielddifferent shape anisotropy causes even larger cohercitive field

INFM – National Research Center – Modena - ItalyINFM – National Research Center – Modena - Italy

magnetic characterizationmagnetic characterization

squared dots with side // to the easy axissquared dots with side // to the easy axis

-400 -300 -200 -100 0 100 200 300 400

H

1 m

2 m

MR

HC

Pattern 5

Field (Oe)

Film easy axis (45 degs)

Sig

nal I

nten

sity

(m

V)

-1500 -1000 -500 0 500 1000 1500

HC

MR

Pattern 5

Film hard axis (0 degs)

Field (Oe)S

igna

l Int

ensi

ty (

mV

)

Fe(100)

easy

Fe(110)hard

different configuration anisotropy for different orientationsdifferent configuration anisotropy for different orientations

INFM – National Research Center – Modena - ItalyINFM – National Research Center – Modena - Italy

conclusionsconclusionsFe microstructures successifully fabricated by FIBFe microstructures successifully fabricated by FIB

the MgO passivation worksthe MgO passivation works

the Fe film crystal quality is OKthe Fe film crystal quality is OK

the geometric quality of the microstructures is goodthe geometric quality of the microstructures is good

the geometry of the microstructures changes their magnetic responsethe geometry of the microstructures changes their magnetic response

to do...to do...to improve the geometric quality of the structures (FIB)to improve the geometric quality of the structures (FIB)

to reduce the size of the structuresto reduce the size of the structures

micromagnetic simulations of the magnetic behaviourmicromagnetic simulations of the magnetic behaviour

INFM – National Research Center – Modena - ItalyINFM – National Research Center – Modena - Italy