review on the prospects for the use of al o for high ... · pdf filereview on the prospects...

Review on the prospects for the use of Al2O3 for high-efficiency solar cells

Erwin Kessels

Department of Applied [email protected]

Silicon surface passivation

16

18

20

22S

eff,backside=

103 cm/s

10 cm/s

Sola

r cell

effic

iency (

%)

Zhao et al., Appl. Phys. Lett. 73, 1991 (1998).Green et al., Prog. Photovoltaics 17, 85 (2009).

Record-efficiency c-Si solar cell (25.0%) Importance of rear-side passivation

Aberle, Prog. Photovolt: Res. Appl. 8, 473 (2008).

/Applied Physics - Erwin Kessels

10 100 100010

12

14

16

107 cm/s

105 cm/s

Sola

r cell

effic

iency (

%)

Solar cell thickness (µm)

Electronic losses at c-Si surface expressed in surface recombination velocity Seff

2/35

Collaborations & Acknowledgments

Dr. Bram Hoex (now: SERIS, Singapore) Gijs Dingemans (graduation Dec. 2011)


Dr. Bram Hoex (now: SERIS, Singapore) Gijs Dingemans (graduation Dec. 2011)

PV institutes Solar cells

Depositionequipment

Chemicals

3/35

Outline – Si surface passivation by Al2O3

1. Introduction• What are the properties of Al2O3?• What makes Al2O3 so interesting?• How does Al2O3 perform in solar cells?

2. On the passivation mechanism • Field-effect or chemical passivation - What is more important? • What are the underlying microscopic mechanisms?

3. Deposition methods & processing aspects 3. Deposition methods & processing aspects • What are the choices for film synthesis?• Optimum conditions in terms of temperature, anneal, thickness, etc.?• Do different methods yield different (key) properties?

4. Upscaling• Market push or pull?• Choice in precursors and precursor quality? • Availability of high-volume-manufacturing equipment?

/Applied Physics - Erwin Kessels 4/35

Al2O3 thin film properties

• Can be synthesized by vapor-phase deposition methods (ALD, PECVD, PVD)

• Wide band gap amorphous dielectric, fully transparent for visible light

• Refractive index (at 2 eV) n = ~1.65

• High thermal stability (Tcrystallization >800 ºC) and good stability against UV radiation

0.5

1.0

1.5

2.0

Refractive

index n

Extinction

coefficient k

J.A. Woollam Co.

Al2O3

c-Si

SiOx1-2 nm

• Can contain H, mostly as –OH groups

• When deposited on H-terminated c-Si: 1-2 nm interfacial SiOx is present between Al2O3 and Si

• Al2O3 is not completely new to c-Si: early work by Hezel and Jaeger (1989) already showed its unique attributesHezel and Jaeger, J. Electrochem. Soc. 136, 518 (1989).

TEMTEM

0 2 4 6 8 100.0

Photon energy (eV)



As-deposited Al2O3

(200 ºC)Annealed Al2O3

(400 ºC in N2, 10 min.)


Al2O3 Al2O3

1.2 nm SiOx 1.5 nm SiOx

c-Si c-Si

Hoex et al., Appl. Phys. Lett. 89, 042112 (2006).6/35


/Applied Physics - Erwin Kessels Hezel and Jaeger, J. Electrochem. Soc. 136, 518 (1989).7/35

Excellent passivation of n, p and p+ Si surfacesE

ffe

ctive

Su

rfa

ce

Re

co

mb

ina

tio

n

Se

ff (

cm

/s)

100

1-2 Ωcm FZ p-Si

SiNx

Em

itte

r S

atu

ratio

n C

urr

en

t D

en

sity

J0

e (

fA/c

m2)

102

103SiN

x

SiO2 (after 2 years storage)

a-Si/SiNx

Low Seff and weak-injection dependence (p-type)

Stable passivation of highly doped p+ Si


Injection Density ∆n (cm-3

)

1012 1013 1014 1015

Eff

ective

Su

rfa

ce

Re

co

mb

ina

tio

n

Ve

locity S

1

10a-Si

Al2O3

Hoex et al., Appl. Phys. Lett. 89, 042112 (2006).

Hoex et al., J. Appl. Phys. 104, 044903 (2008).Hoex et al., Appl. Phys. Lett. 91, 112107 (2007).

Sheet resistance (Ω/sq)

0 50 100 150 200 250Em

itte

r S

atu

ratio

n C

urr

en

t D

en

sity

100

101SiO

2 (after fabrication)

ALD-Al2O

3

a-Si/SiNx

p+ Si emitter

8/35

(Record) efficiencies for c-Si solar cells with atomic-layer-deposited (ALD) Al2O3

Front metal grid Random pyramids

n+ emitterN

P p -Si base

SiNx

n+ emitter

p-Si base

Front metal grid Random pyramids

n+ emitterN

P p -Si base

SiNx

n+ emitter

p-Si base

Rear surface passivationPassivated Emitter and Rear Cell (PERC)

B-diffussed front emitter passivationPassivated Emitter Rear Locally-diffused (PERL)

Point contacts

Aluminium

Al O or Al O /SiO stack2 3 2 3 x

Point contacts

Aluminium

Al O or Al O /SiO stack2 3 2 3 x

• p-type Si base material

• Excellent rear surface passivation, no parasitic shunting

• Efficiency: 20.6% (now: 21.5%)Schmidt et al., Prog. Photovolt. Res. Appl. 16, 461 (2008).Saint-Cast et al., IEEE Electron Device Lett. 31, 695 (2010)

• n-type Si base material

• Excellent p+ emitter passivationbecause of negative fixed charge

• Efficiency: 23.2% (now: 23.5%)Benick et al., Appl. Phys. Lett. 92, 253504 (2008).Benick et al., 35th IEEE PVSC (2010), in press.


Overview of c-Si solar cells with Al2O3

Cell type Front Rear Details Efficiency Reference

p-type PERC ALD Al2O3 + SiOx 4 cm2, PVD Al, photolithography 21.4% Schmidt, ISFH

p-type PERC PVD Al2O3 4 cm2, PVD Al, photolithography 20.1% Schmidt, ISFH

p-type PERC (SiO2 +) ALD Al2O3 + a-SiNx:H 7.1 cm2, printed Al, LFC 20.1% Sun, ITRI

p-type PERC ALD Al2O3 + SiOx 4 cm2, PVD Al, LFC 21.3% Saint-Cast, Fraunhofer ISE

p-type PERC PECVD Al2O3 + (SiOx) 4 cm2, PVD Al, LFC 21.5% Saint-Cast, Fraunhofer ISE

p-type PERC ALD Al2O3 + a-SiNx:H ALD Al2O3 + a-SiNx:H 4 cm2, 43 µm thick, Al2O3 tunnel 19.1% Petermann, ISFH

p-type PERC ALD Al2O3 + a-SiNx:H 4 cm2, EFG Si 18.1% Ebser, Univ. Konstanz


Note: incomplete list; not all results (or materials used) disclosed10/35

p-type PERC ALD Al2O3 + a-SiNx:H 156.25 cm2, screen-printed 19.0% Gatz, ISFH

n-type PERT ALD Al2O3 + a-SiNx:H 4 cm2, B-p+ emitter, fired contacts 20.8% Richter, Fraunhofer ISE

n-type PERL ALD Al2O3 + a-SiNx:H 4 cm2, B-p+ emitter 23.5% Benick, Fraunhofer ISE

n-type PERL ALD Al2O3 + a-SiNx:H 4 cm2, B-p+ emitter, PassDop process 22.4% Suwito, Fraunhofer ISE

n-type BJ 4 cm2, B-p+ emitter at rear 19.4% Benick, Fraunhofer ISE

n-type BJBC ALD Al2O3 + a-SiNx:H 4 cm2, Al-p+ emitter at rear 19.0% Bock, ISFH

n-type EWT ALD Al2O3 + a-SiNx:H ALD Al2O3 + a-SiNx:H 4 cm2, B-p+ emitter 21.6% Kiefer, ISFH

… … … … … …

… … … … … …

Field-effect passivation: fixed charge density Qf

+

5 - 10 kV

Tungsten

needle

Ionization of

air

molecules

by electric

field

-

Deposition of + or – corona charges on passivation layer

200

300

400

500

12 -2

Al2O

3

eff,m

ax (

cm

/s)

a-SiNx:H

Qf= +3x10

12 cm

-2

PECVD SiOx

Qf= +1x10

12 cm

-2

Corona charging experiments(corroborated by C-V and SHG experiments)


• Al2O3 is unique as it contains a very high density of negative fixed charge Qf

(Qf up to 1013 cm-2); fixed charge is located at the Si/Al2O3 interface

• Al2O3 leads also to a high level of chemical passivation (Qcorona + Qfixed = 0)

Dingemans et al., Electrochem. Solid State Lett. 14, H1 (2011).

10

V

+- Mesh

field

Al2O3

Al2O3

c-Si-8 -6 -4 -2 0 2 4 6 8 10

0

100

200Q

f= − − − −5x10

12 cm

-2

Se

ff,m

ax

Corona charge density (1012

cm-2)

Hoex et al., J. Appl. Phys. 104, 044903 (2008).11/35

Field-effect passivation vs. chemical passivation fixed charge density Qf and defect density Dit

C-V measurements

1011

(cm

-2)

annealed Al2O

3

1011

1012

1013

Thermal SiO2

Po

sitiv

e Q

f (c

m-2)

a-SiNx:H


1010

1011

1012

1013

1013

1012

Thermal ALD-O3

Plasma ALD

Thermal ALD-H2O

Ne

gative Q

f (cm

Dit (eV

-1 cm

-2)

Dingemans et al., 35th IEEE PVSC (2010);

• Al2O3 is unique as it contains a very high density of negative fixed charge Qf

(Qf up to 1013 cm-2); fixed charge is located at the Si/Al2O3 interface

• Al2O3 leads also to a high level of chemical passivation (Dit < 1011 cm-2 eV-1)

Dingemans et al., Electrochem. Solid State Lett. 14, H1 (2011).12/35

-1

0

1

annealed

(400 oC, N

2)

ED

MR

sp

ectr

um

∆V

(10

-4 V

)

as-deposited

On the chemical passivation induced by Al2O3

Electrically-detected magnetic resonance

Al2O3

SiOx1-2 nm

TEM image Si/Al2O3 interface

3220 3240 3260 3280 3300 3320

-2

ED

MR

sp

ectr

um

Magnetic field (G)

T=4.5K, 180 mW, 9.16 GHz

H II [011]

• Si/Al2O3 interface is basically Si/SiO2-like due to 1-2 nm interfacial SiOx

• Si dangling-bond-type center Pb0 is prominent defect (Si≡≡≡≡Si)

• Defects “disappear” upon annealing at 400 ºC in N2

Dingemans et al., Appl. Phys. Lett 97, 152106 (2010)./Applied Physics - Erwin Kessels

c-Si

13/35


1019

1020

1021

2x1021

3x1021

4x1021

as-deposited

annealed

(400 oC, N

2)

SiSiO2

D c

on

ce

ntr

atio

n (

cm

-3)

Al2O

3:D

SIMS on deuterated Al2O3/SiO2/Si stackTEM image Si/Al2O3 interface

Deuterated Al2O3

SiO70 nmSiO


• Hydrogen is released from the Al2O3 film and diffuses to the Si interface to passivate dangling bond defects

0 1 2 3 410

17

1018

10as-deposited

D c

on

ce

ntr

atio

n (

cm

Sputtering time (a.u)

/Applied Physics - Erwin Kessels Dingemans et al., Appl. Phys. Lett 97, 152106 (2010).

c-Si

SiO2SiO2

14/35

Deposition of Al2O3 films

1. Pyrolysis• Al(O-iPr)3

2. Atomic layer deposition (ALD)• Thermal ALD – Al(CH3)3 & H2O

• Thermal ALD – Al(CH3)3 & O3

• Plasma ALD - Al(CH ) & O plasma

Hezel & Jaeger

1989

IMEC & TU/e

2005

• Plasma ALD - Al(CH3)3 & O2 plasma

3. Plasma-enhanced CVD• Al(CH3)3 & O2 or CO2

4. Physical vapor deposition (PVD)• Al-target & Ar-O2 plasma

Tokyo Tech

2008

ANU

2009


ALD of Al2O3 from Al(CH3)3 & H2O

ALD of Al2O3

from Al(CH3)3 and H2O

3

6

9

12

15

O3 film

th

ickn

ess (

nm

)

~1 Å/cycle


ALD is an CVD-like process in which films are deposited by repeating cycles each yielding a submonolayer of film and with excellent uniformity & conformality

1 ALD cycle consists of 4 steps: 1) Precursor A [Al(CH3)3] exposure

2) Reactor purge

3) Reactant B [H2O/O3/O2 plasma] exposure

4) Reactor purge

0 25 50 75 100 125 1500

Al 2

O

Number of ALD cycles

Van Hemmen et al, J. Electrochem. Soc. 154, G165 (2007).16/35


Ultrathin high quality high-k gate oxides Excellent conformality on 3D topologies



1 ALD cycle consists of 4 steps: 1) Precursor A [Al(CH3)3] exposure

2) Reactor purge

3) Reactant B [H2O/O3/O2 plasma] exposure

4) Reactor purge





1 ALD cycle consists of 4 steps: 1) Precursor [Al(CH3)3] exposure

2) Reactor purge

3) Reactant [H2O/O3/O2 plasma] exposure

4) Reactor purge


Plasma ALD Al2O3 vs. thermal ALD Al2O3:Deposition temperature

• Growth rate (“growth per cycle” or GPC) is higher for plasma-assisted ALD than for thermal ALD.

• Growth rate decreases with increasing deposition temperature. 200 ºC optimum between film density and growth rate.

• Best passivation properties (lowest


• Best passivation properties (lowest Seff) obtained for 150 -200 ºC.

• Post-deposition anneal is key for surface passivation

Dingemans et al., Electrochem. Solid State Lett. 13, H76 (2010)18/35

Plasma ALD Al2O3 vs. thermal ALD Al2O3:Annealing & firing

101

102

103

Se

ff,m

ax (

cm

/s)

Thermal ALD Al2O

3

n-type p-type

Plasma ALD Al2O

3

n-type p-type

a) b)

After annealat 400 ºC

After firingat ~800 ºC

5 nm thermal and plasma ALD Al2O3As-dep.

200 250 300 350 400 450 500

100

Anneal temperature (oC)

Thermal Plasma Thermal Plasma


2000 µs100

lifetime mapping by µ-PCD

Dingemans et al., J. Appl. Phys. 106, 114109 (2009)Dingemans et al., Phys. Status Solidi RRL 4, 10 (2010)

• Optimum anneal temperature is within the range 350 – 450 ºC

• Films can be ultrathin (~5 nm) and are still sufficiently firing stable

19/35

1019

1020

1021

2x1021

3x1021

4x1021 295 nm

(1) as-deposited

(2) 400oC anneal

(3) "fired" (800oC anneal)

SiSiO2

D c

on

ce

ntr

atio

n (

cm

-3)

Al2O

3:D

(1)

(2)

(3)

(2)

(1)

100 nm


SIMS on deuterated Al2O3/SiO2/Si stackTEM image Si/Al2O3 interface

Deuterated Al2O3

SiO270 nmSiO

1 2 3 4

1017

1018

10

D c

on

ce

ntr

atio

n (

cm

Sputtering time (a.u)


• Hydrogen is released from the Al2O3 film and diffuses to the Si interface to passivate dangling bond defects

• Firing leads to significant out-diffusion of hydrogen, interface remains reasonably passivated.

/Applied Physics - Erwin Kessels Dingemans et al., Appl. Phys. Lett 97, 152106 (2010).

c-Si

SiO2

14/35

H2 and H2O effusion from Al2O3

2

3

4

5

6100°C

H e

ffu

sio

n r

ate

dN

/dt

(10

18

cm

-3s

-1)

Tdep

= 50°C

2

3

4

5

O e

ffu

sio

n r

ate

dN

/dt (a

.u.)

100°C

Tdep

= 50°C

300°C


200 400 600 800 10000

1

2

400°C

300°C 200°C

H e

ffu

sio

n r

ate

d

Temperature T [°C]

200 400 600 800 1000

0

1

Temperature T [°C]H

2O

effu

sio

n r

ate

d

100°C

400°C

200°C

Dingemans et al., to be published (2011)

• Annealing: effusion of H2 and H2O depends heavily on deposition temperature: balance between film mass density and as-deposited H-content

• Al2O3 deposited at 200 ºC can still release sufficient H during firing temperatures

20/35

Plasma ALD Al2O3 vs. thermal ALD Al2O3:Thickness dependence & fixed charge density

40

60

80

100

120

Qf =

12 -2

Qf =

-5x1012

cm-2

Thermal ALD

Seff

,max

(cm

/s)

Plasma ALD1

Thermal ALD

No

rma

lized

life

tim

e

Plasma ALD

• Passivation decreases for <5 nm (plasma ALD) and <10 nm (thermal ALD)

• Fixed charge density Qf is lower for thermal ALD than for plasma ALD Al2O3

• Fixed charge density Qf is located at the Si/SiOx –Al2O3 interface


0 1 2 3 4 5 6 7 8 9

0

20 -3x10

12 cm

-2

SCorona charge density (10

12 cm

-2)

0 5 10 15 20 25 300.1

No

rma

lized

life

tim

e

Al2O

3 thickness (nm)

Dingemans et al., J. Appl. Phys. 106, 114109 (2009)Dingemans et al., Phys. Status Solidi RRL 4, 10 (2010)21/35

Plasma ALD Al2O3 vs. thermal ALD Al2O3:Field-effect vs. chemical passivation

Fixed charge density Qf and interface state density Dit from C-V measurements

Plasma ALD 4.2×1012 ~1013 5.8×1012 9.6×1010

Qf

(cm-2)Qf

(cm-2)Dit

(eV-1cm-2)Dit

(eV-1cm-2)

Before anneal After anneal

• Fixed charge density Qf is lower for thermal-H2O ALD than for plasma ALD Al2O3

• (Very) good chemical passivation for (as-deposited) thermal-H2O ALD Al2O3

• Thermal-O3 ALD Al2O3 has similar (excellent) properties than plasma ALD Al2O3


Plasma ALD 4.2×1012 ~1013 5.8×1012 9.6×1010

Thermal ALD-H2O 1.3×1011 2.9×1011 2.5×1012 1.2×1011

Thermal ALD-O3 5.3×1012 ~1013 3.4×1012 1.0×1011

Dingemans et al., 35th IEEE PVSC (2010); Dingemans et al., Electrochem. Solid State Lett. 14, H1 (2011).22/35

PECVD of Al2O3 from Al(CH3)3 and O2

50

100

150

Plasma ALD

PECVD

Se

ff,m

ax (

cm

/s)

1

10

2.2 ΩΩΩΩ cm

p-type

3.5 ΩΩΩΩ cm

n-type

Effe

ctive life

tim

e (

ms) 0.8 cm/s

2.9 cm/s

14 cm/s

Dingemans et al., Electrochem. Solid State Lett. 13, H76 (2010)

• Also PECVD Al2O3 provide excellent passivation, even at a rate of 30 nm/min

• PECVD Al2O3 contains a high negative fixed charge density (Qf = 6.5x1012 cm-2)

• Passivation by Al2O3 is very robust and does not require very high quality films


0 2 4 6 8 10

Corona charge density (1012

cm-2)

1013

1014

1015

1016

1

1.0 ΩΩΩΩ cm

p-type

Effe

ctive life

tim

e (

ms)

Injection level (cm-3)

23/35

PECVD of Al2O3 from Al(CH3)3 and O2

Deposition temperature

• Growth rate decreases with increasing deposition temperature

• Film density increases with increasing deposition temperature.

• Best passivation properties (lowest Seff) obtained for 200 -300 ºC.

• Post-deposition anneal is key for


• Post-deposition anneal is key for surface passivation

Dingemans et al., Electrochem. Solid State Lett. 13, H76 (2010)24/35

Precursor quality and precursor alternatives

H3C Al

CH3

CH3

H3C Al

CH3

O

CH3

H3C

Al(CH3)2(OiPr) – “DMAI”

Non-pyrophoric

Al(CH3)3 – “TMA”Solar grade

4

6

8

10

p-type Si

Plasma ALD

semiconductor grade TMA

solar grade TMA

Thermal ALD

semiconductor grade TMA

solar grade TMA

eff,m

ax

(cm

/s)

10

Eff

ective life

tim

e (

ms)

Seff,max = 7.2 cm/s

Seff,max = 3.4 cm/s

• Lower purity “solar grade” Al(CH3)3 provides similar high level of surface passivation as semiconductor grade Al(CH3)3

• Non-pyrophoric Al-precursors provide good and “safe” alternative for Al(CH3)3


0 5 10 15 200

2

4

Se

ff,m

ax

Al2O

3 film thickness (nm)

n-type Si

1014

1015

1016

1

n-type (3.5 Ω cm)

p-type (2.5 Ω cm)

Eff

ective life

tim

e (

ms)

Minority carrier density (cm-3)

Seff,max = 7.2 cm/s

Dingemans and Kessels, 25th EU-PVSEC (2010). 25/35

High-volume manufacturing (HVM) equipment

Batch ALD In-line spatial ALD In-line PECVD

www.solaytec.com

www.levitech.nl

www.asm.com


www.beneq.com

www.roth-rau.de

www.generalplasma.com

26/35

High-volume manufacturing (HVM) equipment

Photon International March 2011


HVM equipment: Batch ALD

/Applied Physics - Erwin Kessels www.beneq.com

• 500 wafers/boat with 4 boats leads to nominal throughput of 3200 wafers/hr

• 4 s cycle time using Al(CH3)3 and O3

• 2 wafers per slot placed front-to-front to avoid double-side deposition (textured wafersmight be challenging)

28/35

HVM equipment: In-line spatial ALD (Levitrack)


• Levitrack: wafers are floating in a linear, atmospheric N2 gas track

• Al(CH3)3 and H2O injection from single side and separated by N2 curtain

• Single side deposition and only deposition at the wafers (no reactor cleaning)

• Speed of ~0.2 m/s leads to nominal throughput of 3600 wafers/hour

• 1 system shipped to European solar cell manufacturer

Granneman et al., 25th EU-PVSEC (2010). 29/35


10

100

Plasma ALD

reference

Se

ff,m

ax

(cm

/s)

Annealed

(400 oC, N )

After firing at ~850 oC

2 Ohm cm p-type FZ c-Si samples

1

10

Effe

ctive life

tim

e (

ms) Annealed, 1 min.

Annealed, 10 min.


0 5 10 15 20 251

Al2O

3 film thickness (nm)

(400 C, N2)

• High–throughput ALD yields similar high level of passivation as plasma ALD Al2O3

• Passivation decreases slightly for < 10 nm as typical for thermal ALD Al2O3

• High–throughput ALD Al2O3 (single layer) is sufficiently thermally stable against firing at ~850 ºC

1013

1014

1015

1016

0.1

400 oC, N

2

Effe

ctive life

tim

e (

ms)

Injection level (cm-3)

Dingemans and Kessels, 25th EU-PVSEC (2010). 31/35

HVM equipment: In-line spatial ALD


• Reactive gas bearing; wafers are floating and moved back-and-forth

• Process development (100 wafers/hr) and high-volume (3000 wafers/hr) tool

• For high-volume tool: several systems in parallel (not a long linear track)

• 4 systems sold (IMEC, Fraunhofer ISE, 2 partners in Asia)

Werner et al., Appl. Phys. Lett. 97, 162103 (2010). 32/35

HVM equipment: In-line PECVD

• PECVD based on MAiA®/SiNA® system with next generation plasma source

• Plasma: Al(CH3)3, N2O and Ar

• Stacks of 30 nm Al2O3 and 80 nm a-SiNx:H

• Nominal throughput 2476 wafers/hr

• Several systems upgraded for PECVD of Al2O3 in the field


www.roth-rau.de

• Al(CH3)3 chemical costs < 1 ct/cell and total CoO < 5 ct/layer

Sperlich et al., 25th EU-PVSEC (2010). 33/35

Summary – Si surface passivation by Al2O3

1. Al2O3 is a transparent, highly-stable, negative-charge dielectric

2. Al2O3 provides unique solutions for solar cells: rear surface passivationof p-type Si and p-type emitter passivation of n-type Si

3. Al2O3 leads to excellent chemical passivation (passivation of Si dangling bonds; Dit ~1011 cm-2eV-1), also when used in film stacks

4. Al2O3 can also induce an unique high level of field-effect passivationby negative fixed charges (Qf up to 1013 cm-2)

5. Al2O3 thickness < 10 nm, processing <425 ºC, sufficient firing stable

6. Excellent passivation can be obtained by various deposition methods providing choice between more chemical (thermal ALD-H2O) or more field-effect passivation (thermal ALD-O3, plasma ALD & PEVCD))

7. HVM equipment (ALD, PECVD, …) and processes under development

8. (Sufficiently) low cost-of-ownership, e.g. solar grade Al(CH3)3 and non-pyrophoric precursors can be used


More reading: www.phys.tue.nl/[email protected]/35

Acknowledgments

Dr. Peter Engelhart,

Stefan Bordihn,

Dr. David Rychtarik

Dr. Jörg Müller

And many others

Christophe Lachaud, Nicolas Blasco, Alain Madec

Plasma & Materials Processing group


Dr. Ernst Granneman, Jaap Beijersbergen, Pascal Vermont

Dr. Jan Schmidt

Dr. Jan Benick, Dr. Stefan Glunz

Alain Madec

Dr. Dieter Pierreux

More reading: www.phys.tue.nl/[email protected]

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