Aix-Marseille UniversitéInstitut Matériaux Microélectronique Nanosciences de Provence

Ecole Doctorale Physique et Sciences de la MatièreUniversité de Monastir

Ecole doctorale Matériaux, Dispositifs et Microsystèmes

Croissance et propriétés électroniques et optiques des nanostructures à base de SiGe

Maher NafoutiJuly 29th, 2016

Deterministic fabrication of Si and SiGe-based nanostructures via solid state dewetting of

thin silicon film on insulator

STANDARD METHODS FOR LIGHT MANIPULATION AT THE NANOSCALE

Top DBR

Bottom DBR

θ

SEMICONDUCTOR MICROCAVITIES: FABRY-PEROT RESONATORS

METALLIC NANOPARTICLES:PLASMONIC RESONATORS

HAMAMATSU

Bragg mirror

GaAs/AlAs

Cavity

Bragg mirror

GaAs/AlAs

TEM, G. Patriarche, LPN

Cavity

2

STANDARD METHODS FOR LIGHT MANIPULATION AT THE NANOSCALE

PURCELL EFFECT: enhancement of spontaneous emission rate of two-level system

𝐹𝑃 ∝𝑄

𝑉

QUALITY FACTOR (“photon life”)

MODE VOLUME

METALLIC NANOPARTICLES:PLASMONIC RESONATORS

Fan, SCIENCE 2010

V<<l3

Q~100

….but very small particles suffer from significant ohmic losses, which scale with volume V.

SEMICONDUCTOR MICROCAVITIES: “FABRY-PEROT” RESONATORS

Vahala NATURE 2003

Q=103-109

V>>l3

….small ohmic losses and very large Q but relatively large modal volume V.

Limitation techniques!!

3

Garcıa-Etxarri OPT. EXP 2011Kuznetsov, SCI. REP 2012

A NOVEL SOLUTION FOR LIGHT MANIPULATION AT THE NANOSCALE:DIELECTRIC MIE RESONATORS

DIELECTRIC PARTICLE

l

𝑛𝐷≈ 2𝑅

“[…] the polarization of the electric field is antiparallelat opposite boundaries of the sphere, which gives riseto strong coupling to circulation displacement currentswhile magnetic field oscillates up and down in themiddle.”

4

A NOVEL SOLUTION FOR LIGHT MANIPULATION AT THE NANOSCALE:DIELECTRIC MIE RESONATORS

Anti-reflection coatingsSpinelli, Nat. Comm. 2013

MirrorsMoitra, ACS Phot.2015

DetectorsGarin, Nat. Comm. 2014

APPLICATIONS

-Anti-reflection coatings(Spinelli, Nat. Comm. 2013)

-Mirrors(Moitra, ACS Phot.2015)

-Detectors(Garin, Nat. Comm. 2014)

-Topological edge states(Slobozhanyuk, PRL 2015)

-Electromagnetically induced transparency(Nat. Comm. 2015)

-Anapoles(Miroshnichenko, Nat. Comm. 2015)

5

FABRICATION METHODS FOR DIELECTRIC MIE RESONATORS

Evlyukhin, NANO letter 2012Kuznetsov, SCI. REP 2012Yan, NAT. COMM 2015 Permyakov, APL 2015

LASER ABLATION E-BEAM & RIE of SOI

Staude, ACS nano 2013Person, NANO Letters 2013Coenen, ACS nano, 2013

Spinelli, NAT. COMM. 2012

NANOIMPRINT

COLLOIDS

Shi, ADV. MAT. 2012Shi, NAT. COMM 2013Garin, NAT. COMM. 2014

CHEMICAL ALKALINE ETCHING

Proust, ADV. OPTICAL MATER. 20156

Outline

I: Dewetting of thin Silicon layer on insulator

II: Silicon-Based Mie Resonators via Silicon-on-Insulator dewetting

III: Templated solid-state dewetting to controllably produce complex patterns

IV: Fabrication of core-half shell nanostructures based on SiGe

7

Outline

II: Silicon-Based Mie Resonators via Silicon-on-Insulator Dewetting

III: Templated solid-state dewetting to controllably produce complex patterns

IV: Fabrication of core-half shell nanostructures via UTSOI dewettingand Ge condensation

I: Dewetting of thin Silicon layer on insulator

8

Wang, PHYS. REV B 2015

Young equation of the equilibrium contact angle for thin film

= surface energy density

s = substrate

v = vapour

f = film𝑆 = 𝛾𝑠𝑣 − (𝛾𝑓𝑠 + 𝛾𝑓𝑣)

What’s dewetting?

INSTABILITY OF THIN FILMS

s

f

v

sf

v

Ɵ = 𝒄𝐨𝐬 -1 [ 𝜸𝒔𝒗 − 𝜸𝒇𝒔 /𝜸𝒇𝒗]

9

THIN SILICON ON INSULTOR (SOI) ~10 nm ANNEALED AT HIGH TEMPERATURES (~750-900 C)DEWETS AND FORMS 3D ISLANDS (Rayleigh-like instability)

Danielson JOURN. APPL. PHYS 2006 Pierre-Louis PHYS. REV LETT 2007, 2009Jiang, ACTA MAT. 2012Aouassa New Journal of Physics 2012Wang, PHYS. REV B 2015

INSTABILITY OF THIN FILMS: THE CASE OF THIN SOI

Mullins equation: 𝑉𝑛(𝑠) ∝ 𝛻2𝑘(𝑠) The dewetting speed of an atom on the surface depends on the surface curvature

ENER

GY

METASTABLESTATE

NEW EQUILIBRIUMSTATE2D

3D

10

BUSSMAN New Journal of Physics 2011

- SOI (~ 10 nm)

- ANNEALED AT HIGH TEMPETARURES (750-900 C)

- IN ULTRA-HIGH VACUUM (< 10-9 Torr)

INSTABILITY OF THIN FILMS: THE CASE OF THIN SOI

BUSSMAN New Journal of Physics (2011)M.ABBARCHI and M. NAFFOUTI et al ., ACS nano (2014)

11

Mie Resonators: Ultrathin layer of silicon(h= 10 nm, size= 200 nm)

1,74 1,75 1,76 1,77 1,780,0

0,2

0,4

0,6

0,8

1,0

1,2

1,4

1,6

1,8

PL

In

ten

sit

y(u

,a)

Energy(eV)

SiO2-capped Si QDs (4nm)/SiO2/Si(001)

T=13K

P0=200mW

Quantum dots: Few nanometer of silicon layer(h= 1 nm, size= 20 nm)

INSTABILITY OF THIN FILMS: THE CASE OF THIN SOI

12

Outline

II: Silicon-Based Mie Resonators via Silicon-on-Insulator Dewetting

III: Templated solid-state dewetting to controllably produce complex patterns

IV: Fabrication of core-half shell nanostructures via UTSOI dewettingand Ge condensation

I: Dewetting of thin Silicon layer on insulator

13

Darkfield

Darkfield

WAFER SCALE FORMATION OF SILICON-BASED MIE RESONATORS

VIA SILICON-ON-INSULATOR DEWETTING

14

ATOMIC FORCE MICROSCOPY

WAFER SCALE FORMATION OF SILICON-BASED MIE RESONATORS

VIA SILICON-ON-INSULATOR DEWETTING

780 C, 1h

11 nm Si/145 nm SiO2 layer.780C, 1h

15M. ABBARCHI , M. NAFFOUTI et al ., ACS nano (2014)

WAFER SCALE FORMATION OF SILICON-BASED MIE RESONATORS

VIA SILICON-ON-INSULATOR DEWETTING

EXPERIMENT FEM SIMULATION

• Red shift with increasing size of MRs • Splitting Mode

• Single spot in the middle of the cavity• Two spots near the edge of the Si island and a strong

field intensity outside the resonator16

M. ABBARCHI , M. NAFFOUTI et al ., ACS nano (2014)

The dewetted islands present large fluctuations of the in-plane dimensions

WAFER SCALE FORMATION OF SILICON-BASED MIE RESONATORS

VIA SILICON-ON-INSULATOR DEWETTING

17

M. NAFFOUTI et al., Nanoscale (2016)

WAFER SCALE FORMATION OF SILICON-BASED MIE RESONATORS

VIA SILICON-ON-INSULATOR DEWETTING

18

Quick summary:

• Spontaneous dewetting is a fexible method for large-scale

applications

• Solid-state dewetting of an amorphous ultra-thin Si

layer

WAFER SCALE FORMATION OF SILICON-BASED MIE RESONATORS

VIA SILICON-ON-INSULATOR DEWETTING

19

Outline

I: Dewetting of thin Silicon layer on insulator

II: Silicon-Based Mie Resonators via Silicon-on-Insulator Dewetting

III: Templated solid-state dewetting to controllably produce complex patterns

IV: Fabrication of core-half shell nanostructures via UTSOI dewettingand Ge condensation 20

TIME, TEMPERATURE

SPONTANEOUS DEWETTING vs ASSISTED DEWETTING

E-BEAM AND RIE+ANNEALING

CONTROL OF SIZEAND SPACING

ANNEALING

INDEPENDENT FROMSAMPLE SIZE!!

21M. ABBARCHI , M. NAFFOUTI et al ., ACS nano (2014)

Darkfield

TEMPLATED SOLID-STATE DEWETTING TO CONTROLLABLY PRODUCE COMPLEX PATTERNS

22

This method opens new ways to design solar cells based on substrate with coupled Mie

resonators will have the active region or the p-n junction integrated inside the nanocrystals

TEMPLATED SOLID-STATE DEWETTING TO CONTROLLABLY PRODUCE COMPLEX PATTERNS

ANTIREFELECTION COATING

23

Ishikawa et al., Appl. Surf. Sci (2002)

TEMPLATED SOLID-STATE DEWETTING TO CONTROLLABLY PRODUCECOMPLEX PATTERNS

Different thermal agglomeration regimes:

• High annealing temperature : large assemblies of

islands based on Si and SiGe

• Low annealing temperature: individual islands

24

TEMPLATED SOLID-STATE DEWETTING TO CONTROLLABLY PRODUCECOMPLEX PATTERNS

25

Large fluctuations in the number of dewetted objects

Local changes of the SOI thickness, local defectivity, FIB alignment...

Islands number control

M. NAFFOUTI et al., Small (submitted )

TEMPLATED SOLID-STATE DEWETTING TO CONTROLLABLY PRODUCE COMPLEX PATTERNS

26

1. < N > increases linearly with the pattern area

2. Very different slopes for Si and SiGe are found

being the last much smaller

3. Relative error in the number of dewetted island in

about 10-25%

Small fluctuation in the number of islands, homogeneous size and a precise positioning are not always acheived M. NAFFOUTI et al., Small (submitted )

TEMPLATED SOLID-STATE DEWETTING TO CONTROLLABLY PRODUCE COMPLEX PATTERNS

27

Silicon Silicon-germanium

Relative error about 10-25%

M. NAFFOUTI et al., Small (submitted )

TEMPLATED SOLID-STATE DEWETTING TO CONTROLLABLY PRODUCE COMPLEX PATTERNS

J. YE Scientific Reports (2015)28

TEMPLATED SOLID-STATE DEWETTING TO CONTROLLABLY PRODUCE COMPLEX PATTERNS

The use of complex patterns geometries allows to reduce the

fluctuations of all the structural parameters shared by the

islands below 10% 29

Ishikawa et al., Appl. Surf. Sci (2002)

TEMPLATED SOLID-STATE DEWETTING TO CONTROLLABLY PRODUCECOMPLEX PATTERNS

Different thermal agglomeration regimes:

• High temperature, leading to larger

assemblies of islands

• Low annealing temperature, leading

to individual islands

30

TEMPLATED SOLID-STATE DEWETTING TO CONTROLLABLY PRODUCE COMPLEX PATTERNS

Low T annealing

High vs low temperature dewetting annealing

• High temperature is suitable for the production of complex islands arrangements

• The low temperature conditions allow for specific placement of islandISHIKAWA et al., Appl. Surf. Sci (2002)M. ABBARCHI, M. NAFFOUTI et al., ACS nano (2014)W.C. Carter et al ., Acta metallurgica et materialia (1995)

SURFACE ATTACHMENT LIMITED KINETICS (SALK)SURFACE DIFFUSION LIMITED KINETICS

31

MD

ED

MQ??

4 mm

8 mm

Darkfield

Darkfield

TEMPLATED SOLID-STATE DEWETTING TO CONTROLLABLY PRODUCE COMPLEX PATTERNS

32M. ABBARCHI , M. NAFFOUTI et al ., ACS nano (2014)

E-BEAM LITOGRAPHY vs FIB: COMPLEX DEWETTING SCENARIOS

E-BEAM LITOGRAPHYFIB

SURFACE ATTACHMENT LIMITED KINETICS (SALK) SURFACE DIFFUSION LIMITED KINETICS

TEMPLATED SOLID-STATE DEWETTING TO CONTROLLABLY PRODUCE COMPLEX PATTERNS

• Implantation• Amorphization

• Selective etching

33

TEMPLATED SOLID-STATE DEWETTING TO CONTROLLABLY PRODUCE COMPLEX PATTERNS

3534

• The capabilities of this top-down/bottom-up hybrid method in

engineering the dewetting

• Applied to produce high-densities of MRs with high or low

ordering, but also to create single mono-crystalline resonators

Quick summary:

E-BEAMFIB

TEMPLATED SOLID-STATE DEWETTING TO CONTROLLABLY PRODUCE COMPLEX PATTERNS

• Mass transport mechanisms in solids:

1. Surface Attachment Limited Kinetics

2. Surface Diffusion Limited Kinetics

35

Outline

I: Dewetting of thin Silicon layer on insulator

II: Silicon-Based Mie Resonators via Silicon-on-Insulator Dewetting

III: Templated solid-state dewetting to controllably produce complex patterns

IV: Fabrication of core-half shell nanostructures via UTSOI dewettingand Ge condensation

36

FABRICATION OF CORE-SHELL NANOSTRUCTURES BASED ON SiGe

• 12 nm of silicon bonded to a 25 nm thick SiO2 layer

• Annealed at high temperature (820-840° C) for two hours

• Three samples with supplying 6, 12 and 18 Ge MLs

During cooldown Ge leads to a further ultrafast dewetting of

the SOI and formation of two distinct areas, one with Si-rich

islands (formed before Ge supply) surrounded by Ge-rich

islands (formed after Ge supply).M. NAFFOUTI et al., Nanotechnology (2016)Selected for cover from the septembre issue

37

• Aspect ratio is doubled passing from sample 0 MLs to 18

MLs of Ge amount

• The increase of the Ge content leads to a progressive

increase in h and thus can be used as shape-tuning tool

FABRICATION OF CORE-SHELL NANOSTRUCTURES BASED ON SiGea ) b )

2 00 300 400 50 0 600

0

5 0

10 0

15 0

h(n

m)

< L > (n m )

G e- free 0 M Ls

A 6 M L s

B 12 M Ls

C 18 M Ls

A 6 M L s

B 12 M Ls

C 18 M Ls

0 6 1 2 1 8

0 .0

0 .1

0 .2

0 .3

G e M L s #

S i-r i c h

G e -r ic h

h

S i- r ic hG e -r ic h

38

Si-rich

M. NAFFOUTI et al., Nanotechnology (2016)

Ge composition of the shell is of the order of 15-20% Ge composition of about 25%

Ge-rich

FABRICATION OF CORE-SHELL NANOSTRUCTURES BASED ON SiGe

39

Silicon oxidation leads to Ge enrichment of external shell

M. NAFFOUTI et al., Nanotechnology (2016)T. David et al., Journal of Physical Chemistry C (2015)

FABRICATION OF CORE-SHELL NANOSTRUCTURES BASED ON SiGe

40

After condensation process

Ge-rich feature an external shell is a bit thicker,

about 30 nm and Ge composition of the islands

core is 20-30%.

Si-rich feature an external shell with a composition of

50% in Ge and a thickness of 15-30 nm surrounded by

70 nm of SiO2

M. NAFFOUTI et al., Nanotechnology (2016)

FABRICATION OF CORE-SHELL NANOSTRUCTURES BASED ON SiGe

41

Conclusion

DEWETTING IS A RELEVANT FABRICATION METHOD FOR DIELECTRIC RESONATORS

- PERFECTLY CRYSTALLINE ISLANDSWITH ATOMIC SMOOTH SURFACES

- ONE STEP FABRICATION PROCESS, INDEPENDENT FROM THE SAMPLE SIZE!!

- ALLOWS A PRECISE CONTROL OF THE RESONATOR NUMBER

- IMPLEMENTATION OF CORE-SHELL SIGE-BASED NANOCRYSTALS

- AMORPHOUS SILICON BASED MRs

42

Perspectives

• Electric control of the resonant scattering

• Near field optical spectroscopy in order toinvestigate the distribution of the electricmode and magnetic mode inside NCs

• Theoretical model to explain the nucleationof the complex assemblies of MieResonators

• Optical characterization of SiGe core-shellnanostructures

• C-V characterization

43