Si SiO 2 Si SiO 2 h si Si(100) “SOI” h si 5, 10, 20 nm Démouillage Film mince de SiNanostructures de Si Recuit (T>800 o C)

The end product: nanoislands are semi-organized (130) (100) (130) (150) (100) (150) (100) 10 μm

Surface energy driven kinetics of SOI dewetting LEEM / KMC Area (μm 2 ) t (s) LEEM Kinetic Monte Carlo simulations A (μm 2 ) t (arb. unit) Surface Energy driven SOS square lattice (3ML thick film) First neighbors interaction Substate/Film interaction Si(001) T=860°C H=21±2 nm Diffusion limited kinetics A~t 0.5 (Srolovitz et al. JAP, 1986) A~t 0.8 (Wong et al. Acta Mat., 2000) A~t (Pierre-Louis et al., PRL, 2009) Continuum models Nucleation on facet based model

Front velocity anisotropy versus local rim height Map of front position versus time (LEEM) Rim centers thicken and slow down (v ~ t -0.5 ) Void fingers exhibit constant velocity Rim height (AFM) 32±3 nm 29±3 nm Void fingers have constant rim height

Steady state dewetting of front The front velocity is stable and fingers are organized V front = 49±2 nm/s (T=900°C)

AFM versus KMC at the void finger tip AFMKMC Height (ML) x (atomic unit) x (μm) z (μm)

Finger void velocity model/experiment J=-D.grad (c) c eq,A > c eq,B Si film B A SiO 2 Receeding front J h L c eq,A ≈ c eq,B e E s /kTh DΩDΩ hL V finger ~ c eq,B (e -1) E s /kTh Top view Side view Void finger Receeding front Accumulated Si Si film A B Si rim E s : adsorbate-substrate excess energy 6nm h=21nm Danielson PhD (MIT, USA) 12nm 8nm 21 nm 6 nm

The thermal activation barrier to dewet Barrier surface smoothing on Si(100): E a =2.3±0.1 eV (T= o C)* *M.E. Keeffe, J. Phys. Chem. Solids (1994) Void finger speed E a =2.0 ±0.2 eV Top view Void finger Receeding front Accumulated Si Si film A B Si rim c eq,A > c eq,B Si film B A SiO 2 Receeding front J h L Side view Void fingers E s : adsorbate-substrate excess energy E a : activation energy

Dynamics of solid state dewetting: straight fronts a model system for dewetting

- and - Si/SiO 2 straight fronts H=21 nm; T=804 o C (84.7 min) Stable front Unstable front 15 µm Cheynis et al., accepted PRB 2011 Lithography e  m 60  m Atomic Force Microscopy 7  m Z (  m) 5  m 0.18  m 1D profile LEEM Optical Microscopy (Plateforme Planete C’Nano PACA)

Stable front: evidence of a facetted rim in situ LEEM 15 µm SiO 2 Si rim Rim profile of stable front is facetted Si  =0.31±0.05 T=970°C T=825°C Rim displacement: x  t   =0.38±0.05 Experiment:  exp =0.35±0.05 Theory:  theory =7/22  0.32 Pierre-Louis et al. PRL 2009 Dufay et al. PRL 2011 Leroy et al. En preparation

Aire (μm 2 ) t (s) 0s1250s 4 µm

Aire (μm 2 ) t (arb. unit)

Height (ML) x (unité atomique) x (μm) z (μm)

c eq,A > c eq,B Film de Si B A SiO 2 Recul du front J h L Vue de dessus Void finger Recul du front Si accumulé Film de Si A B Bourrelet de Si Vue de côté

Lithographie « Lift off » faisceau e - PMM A Si Si (wafer) SiO 2 Gravure du Si Microscopie Optique 500  m 60  m Microscopie à force atomique 7  m Z (  m) 5  m 0.18  m 1D profile

4 µm trou carrédoigtnanostructure

140 µm 100 µm 670 µm 530 µm fronts Nucléation hétérogène Film de Si Tranchée Film de Si démouillé 24 min 0 min 5 µm Front stable Front instable

Déplacement du front (µm) temps (min)  =0.31±0.05 T=970°C T=825°C  =0.38±0.05 x t

15 µm SiO 2 Bourrelet de Si

Croissance (couche/couche) temps (min) µm SiO 2 Bourrelet de Si

(1x2) (2x1) ∆t =0.36 min/monolayer ~ 22 s/monolayer ∆t (1x2) =26.1 s/monolayer ∆t (2x1) =17.4 s/monolayer ∆t (1x2) / ∆t (2x1) =1.5 Comportement moyen

ex situ AFM (20  20 µm)  25s in situ LEEM Lateral Instability: new branch -0.1 µm 0.25 µm 2.5 µm