Combinaison quantitative GISAXS et STM: un outil pour sonder les interfaces enterrées. E xemple du Co/ Au(111). O.Fruchart, Laboratoire Louis Néel (CNRS), Grenoble G. Renaud, M. Noblet, O. Ulrich ! DRFMC/SP2M/IRS (CEA), Grenoble J.-P. Deville, A. Barbier, F. Scheurer, J. Mané-Mané IPCMS (CNRS/ULP/ECPM), Strasbourg V. Repain, G. Baudot, S. Rousset GPS-Jussieu, Paris 11/ 10 / 2 0 0 2 Laboratoire Louis Néel. Laboratoire Louis Néel. Laboratoire Louis Néel. http:/ / lab http:/ / lab- neel neel.grenoble. .grenoble.cnrs cnrs.fr fr/ them es them es/ couches/ / couches/ ext ext/ http:/ / lab- neel.grenoble.cnrs.fr/ them es/ couches/ ext/
GISAXS : principle and set-up GISAXS: G razing I ncidence S mall A ngle X -ray S cattering Objects > > atom s Surface sensitive PRINCIPLE TECHNICAL ASPECTS • ID32 beamline at ESRF • In-situ under UHV: � real time � background substraction • No window before sample : low background � In-plane / out-of-plane diffusion � Probes size (H,d), shape, correlations Olivier Fruchart - 11/10/2002 - p.2 Laboratoire Louis Néel Laboratoire Louis Néel Laboratoire Louis Néel http:/ / lab http:/ / lab- neel neel.grenoble. .grenoble.cnrs cnrs.fr fr/ them es them es/ couches/ / couches/ ext ext/
GISAXS : lateral information Ex situ GI SAXS on self- assem bled dots : lateral inform ation Si 1-x Ge x islands � Information on dots shape and lateral order. M. Schm idbauer et al., PRB58, 10523 (1998) Olivier Fruchart - 11/10/2002 - p.3 Laboratoire Louis Néel Laboratoire Louis Néel Laboratoire Louis Néel http:/ / lab http:/ / lab- neel neel.grenoble. .grenoble.cnrs cnrs.fr fr/ them es them es/ couches/ / couches/ ext ext/
GISAXS : depth information Ex situ GI SAXS on self- assem bled dots Pd/ MgO(001) islands G. Renaud et al., unpublished Olivier Fruchart - 11/10/2002 - p.4 Laboratoire Laboratoire Louis Néel Louis Néel Laboratoire Louis Néel http:/ / http:/ / lab lab- neel neel.grenoble. .grenoble.cnrs cnrs.fr fr/ them es them es/ couches/ / couches/ ext ext/
3D self-organization : effect of corrugation Co/ Al 2 O 3 granular system (sputtering) (Co: 0.7 nm/Al 2 O 3 :3 nm) 14 REAL SPACE RECIPROCAL SPACE TEM cross-section (Sequential sputtering) GISAXS: G razing I ncidence S mall A ngle X -Ray S cattering Co-sputtering Sequential sputtering � FCC vertical stacking (not epitaxial !) D. Babonneau, Appl. Phys. Lett. 76, 2892 (2000) Olivier Fruchart - 11/10/2002 - p.5 Laboratoire Louis Néel Laboratoire Louis Néel Laboratoire Louis Néel http:/ / lab http:/ / lab- neel neel.grenoble. .grenoble.cnrs cnrs.fr fr/ them es them es/ couches/ / couches/ ext ext/
Au(111) > Basic s x √ 3 reconstruction Planar view of Au(111) HCP HCP FCC FCC M O O Z 50 x 28 nm Second layer atoms Cross-sectional view Site B Corrugation hcp : ABA fcc : ABC Atoms of the topmost layer C C A A B B B B B B B B B Site A A A A A A A A A A C C C C C C C C C Site C B B B B B B B B B Bride position A A A A A A A A A (smaller diameter for clarity only) Olivier Fruchart - 11/10/2002 - p.6 Laboratoire Laboratoire Louis Néel Louis Néel Laboratoire Louis Néel http:/ / http:/ / lab lab- neel neel.grenoble. .grenoble.cnrs cnrs.fr fr/ them es them es/ couches/ / couches/ ext ext/
Au(111) > secondary ‘ chevron’ reconstruction 250 x 250nm Corrugation ~ 0.2 Å Unit cell size : ~ 7.5 x 25nm J. V. Barth et al., Phys. Rev. B 4 2 ( 1 5 ) , 9 3 0 7 ( 1 9 9 0 ) � Isotropic surface relaxation A.R. Sandy et al., Phys. Rev. B 4 3 ( 6 ) , 4 6 6 7 ( 1 9 9 1 ) Olivier Fruchart - 11/10/2002 - p.7 Laboratoire Laboratoire Louis Néel Louis Néel Laboratoire Louis Néel http:/ / lab http:/ / lab- neel neel.grenoble. .grenoble.cnrs cnrs.fr fr/ them es them es/ couches/ / couches/ ext ext/
Au(111) > A template for self-organization 350 x 350 nm FACTS : Co, Ni, Fe, Cu, Rh growth on Au(111) gives rise to self-organized arrays of dots ORIGIN ? (0.20AL Co @300K) nm 2Co 0.4 0.3 0.2 0.1 0 See also: nm 0 5 10 15 20 D.D. Cham bliss et al., PRL 66, 1721 ( 1 9 9 1) Fe, Ni : 1 AL-high dots B.Voigtlander et al., PRB 4 4 , 1 0 3 5 4 ( 1 9 9 1 ) Co : 2 AL-high dots Olivier Fruchart - 11/10/2002 - p.8 Laboratoire Louis Néel Laboratoire Louis Néel Laboratoire Louis Néel http:/ / http:/ / lab lab- neel neel.grenoble. .grenoble.cnrs cnrs.fr fr/ them es them es/ couches/ / couches/ ext ext/
Au(111) deposits > nucleation stage Fe, Co, Ni (etc.) nucleation: atomic place exchange mechnism with Au atoms 0.25ML Ni @300K : 1ML-high dots Example: 0.002ML Ni@ 300K J.A.Meyer et al., Surf.Sci. 365 , L647 (1996) See also: S. Rousset et al. W. G. Cullen et al., Surf. Science 420, 53 (1999) Leading parameter (?) : deposit has a higher surface energy. (and Au atoms stress near chevrons) Olivier Fruchart - 11/10/2002 - p.9 Laboratoire Laboratoire Louis Néel Louis Néel Laboratoire Louis Néel http:/ / lab http:/ / lab- neel neel.grenoble. .grenoble.cnrs cnrs.fr fr/ them es them es/ couches/ / couches/ ext ext/
Au(111) deposits > continuous films Continuous film s t > 2 AL t > 5- 7 AL Continuous film s Perpendicular m agnetic anisotropy M J. Pommier el al., Phys. Rev. Lett. 65, 2054 (1990) M. Speckm ann et al., Phys. Rev. Lett. 75, 2035 (1995) Etc. From dots to film s S. Padovani et al., Phys. Rev . B 59, 11887 (1999) Olivier Fruchart - 11/10/2002 - p.10 Laboratoire Laboratoire Louis Néel Louis Néel Laboratoire Louis Néel http:/ / lab http:/ / lab- neel neel.grenoble. .grenoble.cnrs cnrs.fr fr/ them es them es/ couches/ / couches/ ext ext/
GI SAXS : inter- and intra-row order CCD Thickness: 1 Å ; coverage: 25% q ? INTRA-ROW ORDER: 4p/ ? SUPER-CRYSTAL ∆ Q/ Q= 3% q 2? INTER-ROW ORDER: 4p/ ? LIQUIDE-TYPE Κ = 8.5nm σ = 2.1nm Olivier Fruchart - 11/10/2002 - p.11 Laboratoire Louis Néel Laboratoire Louis Néel Laboratoire Louis Néel http:/ / http:/ / lab lab- neel neel.grenoble. .grenoble.cnrs cnrs.fr fr/ them es them es/ couches/ / couches/ ext ext/
GISAXS : similarity with RHEED ? � Ordered sample � ‘super’ reciprocal space ? � Grazing incidence and 2D detector � similarity with RHEED Olivier Fruchart - 11/10/2002 - p.12 Laboratoire Laboratoire Louis Néel Louis Néel Laboratoire Louis Néel http:/ / http:/ / lab lab- neel neel.grenoble. .grenoble.cnrs cnrs.fr fr/ them es them es/ couches/ / couches/ ext ext/
GI SAXS on Co/ Au(111) : « crystallography » on a three-fold textured super-crystal 1.5 µ m x 1.5 µ m STM image 3-fold symmetry of Au(111) crystal � 3 ‘equivalent domains’ FFT Olivier Fruchart - 11/10/2002 - p.13 Laboratoire Louis Néel Laboratoire Louis Néel Laboratoire Louis Néel http:/ / http:/ / lab lab- neel neel.grenoble. .grenoble.cnrs cnrs.fr fr/ them es them es/ couches/ / couches/ ext ext/
Co/ Au(111) « crystallography » : experimental GISAXS ‘reciprocal space’ GISAXS FFT of STM Transverse cross-section of a peak 550 Position (a.u.) 500 450 Similar patterns and good understanding 400 � Do we gain any new information from GISAXS ? 234 236 238 240 242 244 246 248 250 Azimuth Olivier Fruchart - 11/10/2002 - p.14 Laboratoire Louis Néel Laboratoire Louis Néel Laboratoire Louis Néel http:/ / lab http:/ / lab- neel neel.grenoble. .grenoble.cnrs cnrs.fr fr/ them es them es/ couches/ / couches/ ext ext/
Rod intensity analysis (intra-row) First order peak intensity Second / First order 0.1 0.01 1E-3 1E-4 0 5 10 15 20 25 30 35 0 5 10 15 20 Thickness ( Å) Thickness ( Å) Features to explain � Maximum at 6Å = 3 atom ic layers ? � Weak intensity ? � Significant intensity for continuous film ? � Intermediate minimum ? Olivier Fruchart - 11/10/2002 - p.15 Laboratoire Louis Néel Laboratoire Louis Néel Laboratoire Louis Néel http:/ / lab http:/ / lab- neel neel.grenoble. .grenoble.cnrs cnrs.fr fr/ them es them es/ couches/ / couches/ ext ext/
Rod intensity : I2/ I1 minimum : dot shape factor 0.1 1 0.1 RATIO: Second / First order peak intensity 1E-2 Calculated � Deposition rate calibration 1E-3 0.01 1E-4 0 1 2 3 Simple model of 1D coalescence Thickness ( ) Å Measured Intensity = Periodicity x dots form factor 1E-3 π Λ Period within lines : 2 / d S. Padovani et al., d PRB6 1 , 7 2 ( 2 0 0 0 ) Λ d WEAK COVE RAG E 1E-4 0 5 10 15 20 Thickness (Å) C OALE SCE NCE q 0 1 2 3 4 ~0.1Å (d=0.23 Λ) ~2Å (d= Λ) ~1Å (d= Λ/√2) First zero of dot form factor ~0.5Å (d= Λ/2) Olivier Fruchart - 11/10/2002 - p.16 Laboratoire Louis Néel Laboratoire Louis Néel Laboratoire Louis Néel http:/ / lab http:/ / lab- neel neel.grenoble. .grenoble.cnrs cnrs.fr fr/ them es them es/ couches/ / couches/ ext ext/
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