SPECIAL TOPICS IN ION BEAMANALYSIS –PART 2 SINGLE …

SPECIAL TOPICS IN ION BEAM ANALYSIS – PART 2SINGLE ION TECHNIQUES:STIM & IBIC

Milko JakšićLaboratory for Ion Beam Interactions, Experimental physics divisionRuđer Bošković Institute Zagreb, Croatia

Ion Beam Analysis & NUCLEAR MICROPROBE

Charge pulse

Recoil nuclei

Transmitted particles

Forward scattered particles

Light

X-rays

rays

Backscattered particlesTARGET

Ion beam

Nuclear reactionproducts

Secondary electrons

ANALYSIS (elements, isotopes)with MeV ION BEAMS - (nA, pA)

- elements - x-rays (PIXE)- backscattering (RBS)- recoil (ERDA)

- isotopes - nuclear reactions - rays (PIGE)particles (NRA)

CHARACTERISATION (density, charge transport, crystal structure, morphology,…) with MeV SINGLE IONS - (fA)

- density - transmitted ions (STIM)- charge transport - charge pulse (IBIC)- crystal structure - channelling- morphology - secondary electrons (SEI)

Single ion implantation

Why single ions?• Implantation of one particular atom

at exactly known position in exactly known time seems to be extremely attractive!

• And it is easy (to perform experimentaly) !

Single ions – ionisation & defects

Every ion:- Implants itself into

the substrate- Ionises many atoms

on its way - creates large number of charge pairs

Heavy ions:- Create many

vacancies - Some secondary

electrons- Some desorbed

molecules

Accelerator & nuclear microprobeIdeal radiation source

XY

protonbeam

scangenerator

XY

quadrupole doubletfocusing lens

sampleobject slits

IBIC signal

IBIC - chargecollection efficiency

imagesprotons

alphas7Li

12C16O

IONS- p, , Li, C, O,..

RANGE - 2 to 200 m

ION RATE- currents 0 - 106 p/s

ION POSITION- focusing and scanning

Accelerator & nuclear microprobeAvailable ion beams

Silicon I 127‐ Si 28 C 12 He 4 H 1

Range(µm)E=1 MeV

0.37 1.13 1.6 3.5 16.3

Range (µm)E=10 MeV

3.7 4.8 9.5 69.7 709

AT RBI ‐ terminal voltages – 0.1 to 6 MVIon sources – sputtering, RF alphatross, duoplasmatron

Good selection of ion ranges / dE/dx !!

Single ion characterisation:STIM – Scanning Transmission Ion Microscopy:imaging of areal densities (dE/dx)

STIM – Scanning ion transmission microscopy


10 µm

STIM image of copper grid using 8 MeV O3+ ions


Density map for flies wing: 6 MeV O ions (left) and 2 MeV protons (right)

Track shape characterisation


11 MeV 12C3+ ions

high energy lossd ~ 1.68 m

low energy lossd ~ 1.45 m

Combination of STIM with 3D analysisusing C ion induced coincidencespectroscopyO distribution and concentration in z direction ‐ small sample dimensions

~ 15 mm

Bi2Sr2CaCu2O8+ whiskers

17.7 mx

y

z

on axis STIM 28×28 m2

Channeling STIMSTIM (transmission) channeling • currents ≈ 1 fA radiation

damage can be neglected• but, only transmission samples

channeled ions

nonchanneled ions

E0

Ion beam induced charge - IBIC

a) Ions lose their energy dE/dxb) Creation of charge pairs e/h

Depth (m)

0 5 10 15 20 25

Ener

gy lo

ss (k

eV/

m)

0100200300400500600700800

2 MeV -particles

2 MeV protons

2

2

2

220

20

24

1ln2ln4cv

cv

IvmNZ

vmze

dxdE

Bethe formula:

ions

electrons

+-

--

-

--

-

-

+ +

++

+

++

Ion beam induced charge - IBIC1. for E 0 charge drift

+-

--

-

--

-

-

+ +

++

+

++

h

he

ed

xhd

xe e

Lde

Ld

QQ 110

h

he

ed

xhd

xe e

Lde

Ld

QQ 110

di = ()iEdi = ()iE

- Charge carriers produced alongthe ion path drift in electric field

- Charge pulse height depends on the local value of electric field, mobility and lifetime of charge carriers.- Collection length

- for constant E, Induced charge signal corresponds to the value of

2. for E = 0 charge diffuse

dxxxr

x dxdEdxx

dxdEY e xL

di

d

d

)(0

dxxxr

x dxdEdxx

dxdEY e xL

di

d

d

)(0

diffusion region

drift region

+

‐

a) Ions lose their energy dE/dxb) Creation of charge pairs e/hc) Charge transport:

1. Drift - in electric field 2. Diffusion

d) Induced chargee) IBIC signal





V

Q

V

Vout

d

T= 0

-2 0 2 4 6 8 10 12 14

0.000

0.025

0.050

0.075

0.0

0.2

0.4

0.6

0.8

1.0

I

Time

Q

Induced current

Induced charge

v

dvq)t(I

T

0

dt)t(I)t(Q





V

Q

V

Vout

d

T=10

Induced current

Induced charge

v

dvq)t(I

T

0

dt)t(I)t(Q

-2 0 2 4 6 8 10 12 14

0.000

0.025

0.050

0.075

0.0

0.2

0.4

0.6

0.8

1.0

I

Time

Q


-2 0 2 4 6 8 10 12 14 16

0.000

0.025

0.050

0.075

0.0

0.2

0.4

0.6

0.8

1.0

I

Time

QT

0

dt)t(I)t(Q

-2 0 2 4 6 8 10 12 14

0.000

0.025

0.050

0.075

0.0

0.2

0.4

0.6

0.8

1.0

I

Time

Q

t

dvqtI exp)(

In reality (charge carrier lifetime) can be short due to defects !

Velocity; v dTRMobility; d2/(TR *VBias)

Ion Beam Induced ChargePulse processing (visit ORTEC tutorial)

Charge sensitive preamplification‐ For high resolution PHA

(pulse height analysis)‐ Due to integration, time

structure of the signal is forgotten

‐ Shaping time constant

Current preamplifier‐ For studying of pulse time structure – TRIBIC)

t(s)

-1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

VO(mV)

-2

0

2

4

6

8

10

12

14

16

18

20

-100 V-200 V-40 V-80 V-1000 V

Electron mobility: e= 781 cm2/Vs

Vtd

r

2

CdZnTeOutput from the charge senistive preamlifier at digital osciloscope

ions

-+

Ion Beam Induced ChargePulse processing (time resolved IBIC)


250 nm

IBIC spatial resolution down to 0.25 μm

Frontal IBIC on polyCVD diamond

EFG siliconSchotky diode

Frontal IBIC images can identify distribution of electrically active defects !

Ion beam induced chargeFrontal IBIC

Ion beam induced chargeFrontal IBIC

By proper selection of ion type and energy, CCE (charge collection efficiency) at different sample depths can be imaged.

4.5 MeV Lirange 6μm

3 MeV protonsrange 90 μm

Si Schotky diode

surface

bulk

Ion beam induced charge - IBICLateral IBIC on Si power diode

E = 0

contact and/orheavily dopedregion

pn junction

E < 0

ion beam

0 zd z

(z<zd) = 1

(z>zd) = exp(‐(z‐zd)/Lp,n)hole or electrondiffusion length

50 100 150 200 2500,08

0,10,1

0,2

0,4

0,6

0,811

Lp = ( 27.3 ± 0.8 ) m = (0.57 ± 0.03)s 117.5 V

90.6 V

60.4 V28 V

Col

lect

ion

effic

ienc

y

Depth (m)

CdZnTe

U=+50V ST=2.0s U=+100V ST=2.0s U=+150V ST=2.0s U=+250V ST=2.0s

U=+50V ST=8.0s U=+100V ST=8.0s U=+150V ST=8.0s U=+250V ST=8.0s

In-Au ST=8s

depth (m)0 250 500 750 1000 1250 1500 1750 2000

effic

ienc

y (%

)

0,0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1,0

+50V+100V+150V+200V+250V

electrons

holes

electronsholes

ion beam

CCE 100%

fully depleted device(ideal case)


Ion beam induced damagedE/dx – nuclear stopping

dE/dx of Xe ions in silicon

50 Li7 m‐2 = 5 109 cm‐2

6 Li7m‐2 = 6 108 cm‐2

(4 events per pixel)

• For 100% ion impact detection efficiency, IBIC can be used to monitor irradiation fluence

• Irradiation of arbitrary shapes • On‐line monitoring of CCE degradation

Ion microprobe irradiation & IBIC probing

Ion microprobe irradiation & IBIC probing

• By excessive irradiation of small detector regions (e.g. 50 x 50 μm2) induced defects (charge carrier traps) degrade charge collection efficiency (CCE)

• Irradiation fluence and CCE are continuously monitored on-line

• Damaging/probing concept can be used for radiation hardness tests (e.g Si vs. diamond)

V. Grilj et al (RBI, JAEA)Nucl. Instr. Meth. B306 (2013) 191


1E11 1E12 1E13 1E140.5

0.6

0.7

0.8

0.9

1.0

scCVD (150V) membrane (80V) membrane (15V)

CC

E

d [MeV/g]

scCVD diamond membrane detector

CVD diamond membrane provides a trigger for each single ion transmitted to the air

Extreme radiation hardness– equivalent of 1016 cm-2 of 1 MeV neutrons !!


CCE = 1 – D* kσ kσ je svojstvo materijala D* efektivna doza

Zaključak da je otpornost na zračenje silicija i dijamanta vrlo slična !

Diamond: V. Grilj et al, Nucl. Instr. Meth. B372 (2016) 161Silicij: Ž. Pastuović et al, Appl. Phys. Lett. 98 (2011) 092101

Samples: • Si PIN diode Hammamatsu S1223• 4H-SiC Schottky diode

Probing the defect creation process (Si and SiC) Pulsed beam

Irradiation and IBIC probing:• 3.25 MeV C ions (both irradiation

and IBIC probing • Ion range 3.5 μm in Si ( as for 1

MeV He ions )• ton = 1 ms; toff = 0.1 to 50 ms• fluence:

346 μm-2 (Si) 33 μm-2 (SiC)

• 400 pulses

System is typicaly used for MeV SIMS & single ion implantation, irradiation and probing is controlled by SPECTOR

Probing the defect creation process (Si and SiC) Pulsed beam

Irradiation and IBIC probing:• 3.25 MeV C ions (both irradiation

and IBIC probing • Ion range 3.5 μm in Si ( as for 1

MeV He ions )• ton = 1 ms; toff = 0.1 to 50 ms• fluence:

346 μm-2 (Si) 33 μm-2 (SiC)

• 400 pulses

Si pin

4H SiC

Average distance between ions within a single pulse was > 1 μm .... too large for ‘dynamic annealing’ of defects

No statisticaly significant changes have been observed for different ton/toff cycles (millisecond range)

In air IBIC experiment • Large detector structures (e.g. high energy physics

detectors) can not be tested in small vacuum chamber

• Alternative – in air microbeam !• But - beam spot degradation

Degradation of beam spot (in micrometers) for SiN and diamond exit foil

• SOLUTION:• SiN exit foil• up to 2 mm working distance• Proton energy > 6 MeV !!

Energy / air path 100 nm Si3N4 6 µm diamond

3 MeV / 0.5 mm 1.02 9.0

3 MeV / 2.0 mm 4.39 30.6

6 MeV / 0.5 mm 0.50 4.3

6 MeV / 2.0 mm 2.06 14.8

9 MeV / 0.5mm 0.34 2.9

9 MeV / 2.0 mm 1.40 9.9

Si pin diode

SPECIAL TOPICS IN ION BEAMANALYSIS –PART 2 SINGLE …

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