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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