Electron Beam Induced Depositioninvestigating a new tool for Spintronics

Graduation presentation

Michael Beljaars

Hans Mulders, FEI Company

Reinoud Lavrijsen, TU/e

Henk Swagten, TU/e

Physics of Nanostructures (FNA)

Spintronics

Electron• charge• spin

e-

spin + electronics =

Spintronics!

Electron Beam Induced Deposition

substrate

needle

electron beam

precursor

vacuum environment

EBIDEBIDEBIDmultiple passes

element of interest

contamination

precursor fluxdeposition

direct structuring deposition of arbitrary material resolution down to 10 nm

Possibilities of EBID

EBID deposited iron magnets

substrate

• What equipment is used ?• Which precursors are investigated?

Deposition yieldComposition

Magnetic properties

Shape analysis

• How fast can we make a deposition?• How much iron is in the magnet?• How strong is the magnet?

• How well defined is the shape of the deposition?

FEI dual beamInvestigated iron precursors

iron

NZ

FEI dual beam

view inside chamberoutside view

electron beam

sample holder

needle

vacuum chamber

Investigated iron precursors

Tri-iron-dodeca-carbonyl Di-iron-nona-carbonyl

Fe3(CO)12 Fe2(CO)9

low gas flux high gas flux

Deposition yield

substrate

deposition

beam

VY

I t

deposition volume V

high gas flux

low gas flux

Composition

iron

carbon

oxygen

high gas flux

low gas flux

Magnetic properties

AFMheight image

MFMmagnetic image

NZ

5 µm

Shape analysis

substrate

deposition

3D AFM image

Surface processes

substrate

needle

adsorption

desorption

diffusion

vacuum environment

high N

low N

surface occupation N

EBID and surface occupation

substrate

deposition

electron beamdepositiondeposition

adsorption desorption

diffusion diffusion

N

N

heig

ht

Simulation

• Adsorption• Desorption

• Diffusion

• Deposition

adsE

diffE

adsorptiondesorption

distance to surface

pote

ntia

l

adsEdiffE

distance along surface

pote

ntia

l

diffusion

Experiment and simulation

heig

ht (

a.u.

)

length (a.u.)

width (a.u.)

experiment simulation

Waiting time experiment

substrate

deposition

5

10

15

20

25

30

35

0 ms15 ms40 ms

0 1 2 3 4 50

heig

ht (

nm)

width (μm)1 1.2 1.4 1.6

0

5

10

15

20

25

30

35

width (μm)

high surface occupation

low surface occupation

diffusion

spiralingdeposition

inner to outer

Pass time 45 ms

Conclusions

• Depositions of two iron precursors characterized• Yield low yield for Fe3(CO)12, average yield for Fe2(CO)9

• Composition very high iron content (up to 60 atomic %)

• Magnetic properties indications for ferromagnetic behavior

• Deposition shapes understood• Model developed• Experimental results qualitatively explained by model

Outlook

• Model enhancement• determine energy barriers involved in surface processes• quantitative description of deposition process

• Deposition properties• further enhance composition• extensive magnetic characterization• investigate electrical conductance

Electron Beam Induced Deposition

substrate

needle

electron beam

Magnetic properties

FEI dual beam

Investigated iron precursors

Tri-iron-dodeca-carbonyl Di-iron-nona-carbonyl

Fe3(CO)12 Fe2(CO)9

methanol

Deposition - Diffusion regimes

N

N

heig

hthe

ight

Giant Magneto Resistance

spin + electronics = Spintronics!

Electron – Solid interactions

substrate

electron beam

secondary electrons

Increasing beam energy

0 1 2 3 4 50 . 0

0 . 5

1 . 0

1 . 5

2 . 0

2 . 5

SE y

ield

(SE

/ P

E)

elect ron beam energy (keV )

area of maximum SE yield

Electron Beam Induced Deposition

substrate

needle

electron beam

precursor

adsorption

desorption

precursor flux

diffusion

vacuum environment

Electron – Solid interactions

substrate

electron beam

Electron – Solid interactions

substrate

electron beam

secondary electrons

Increasing beam energy

0 1 2 3 4 50.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

SE

yie

ld (

SE

/ P

E)

P E energy (keV )

Outline

• Introduction to Spintronics• Electron Beam Induced Deposition• Investigated iron precursors• Characterization of depositions• Deposition geometry

• Conceptual model• Experiment

• Conclusions• Outlook

Deposition yield

substrate

deposition

beam

VY

I t

Beam current (nA)

Yie

ld (

μm

3 nC

-1)

deposition volume V

high gas flux

low gas flux

EBID deposited magnets

substrateEBIDEBIDEBIDmultiple passes

• What equipment is used ?• Which precursors are investigated?

Deposition yieldComposition

Magnetic properties

Shape analysis

• How fast can we make a deposition?• How much iron is in the magnet?• How strong is the magnet?

• How well defined is the shape of the deposition?

FEI dual beamInvestigated Iron precursors