DÃ©formation photoinduite dans les films minces contenant des ...

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$G. M. Zaslavsky, Chaos, fractional kinetics, and anomalous transport ...$

Chapter 3. Microscopic mechanisms at the origin of the photo-induced deformation inazobenzene-containing thin films 106p-interferences-interferencetimeCalculateddeformationkinetics(a)pastel-00527388, version 1 - 19 Oct 2010Measureddeformationkinetics(PMMA)(b)Figure 3.35: PMMA-DR1: statistical model. (a) Simulations; (b) Experimentalresults (shear-force images of the photodeformation obtained on a 135 nm thick PMMA-DR1 sample, reproduced from ref. [15]). Sample thickness = 100 nm, laser wavelengthλ = 473 nm, laser power = 1 mW per beam.where θ and φ describe the molecule orientation in the space.So we obtain that: Ω = 2 Ω (3.33)We recall that our experimental illumination configuration is characterized by the superimpositionof a E ‖ and E ⊥ interference patterns, spatially shifted one from the otheralong the x-axis by half an interference period (see section 3.3.2). The relative intensityof both the interference pattern depends on the value of ϕ. Since the statistical displacementrelies strictly on the spatial distribution of the light field intensity, we can definea displacement efficiency η I as:η I = Ω(E 0 ‖ (ϕ) ) 2− < p⊥ > Ω(E0⊥ (ϕ) ) 2(3.34)where the first term describes matter migration away from the ‖ field component andthe second one matter migration away from the ⊥ field component. Therefore a positiveefficiency indicates matter migration towards the ⊥ field component.
Ipara - Iperp/2Chapter 3. Microscopic mechanisms at the origin Ipara - Iperp/2+Epol of the photo-induced speed_measured deformation inEmodpolazobenzene-containing thin films 107field_calc_2 15:20:11 29-10-2009speed_corr_new41! I+ ! pol! I=! E ! 0 (")! polEmodint( ) 2 #! 1 (2 E 0 $(")) 220-2-4PMMAsol-gel0.50-0.5-1deformation rate (nm/s)speed_corr0 15 30 45 60 75 90Sphi! (deg.)Ppastel-00527388, version 1 - 19 Oct 2010Figure 3.36: PMMA-DR1: deformation efficiency vs amplitude and polarization spatialmodulation. SRG growth rate: PMMA ( - estimated on the first 100 s), sol-gel(□); η pol (black dashed curve); η I (grey curve); η I + η pol (black solid curve).Figure 3.35 shows the calculated images of the deformation kinetics for a PMMA-DR1thin film having a thickness of ≃ 100 nm. Simulations are performed for both s andp polarizations and are compared with the experimental results obtained on samples ofthe same thickness. The model seems to describe very well the matter migration phenomenaobserved with both polarizations. In particular, it describes the main featuresof the deformation kinetics: matter transport away from the illuminated areas (for bothpolarizations) and p-induced transport more efficient than s-induced transport. Moreover,in the case of s-polarized light the simulation reproduces the central groove withinthe reliefs, experimentally observed, which supports the less efficient matter transportproduced by the E ⊥ field component.In Figure 3.36 we report the matter migration efficiency together with the variationof η I (grey curve) as a function of the polarization angle ϕ. We note a rather goodagreement between the variation of this parameter and the matter migration rate ()in PMMA. Very surprisingly, the sum η I + η pol (black solid curve) shows a remarkableagreement with the measured SRG growth rate.This indicates that in PMMA-DR1 the mass migration efficiency is governed by the superimpositionof two mechanisms: one which is well described by a statistical directionalmatter migration model, depending mainly on the photoisomerization rate, i. e. on theintensity pattern, and the other which depends on the spatial distribution of the lightpolarization and is compatible with models based on microscopic transport mechanismsoriginating from the electromagnetic forces [8].
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Thèse de doctorat de l’Ecole Pol
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AcknowledgementsAt the beginning it
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vpastel-00527388, version 1 - 19 Oc
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ContentsAbstractiAcknowledgementsii
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List of Figures1.1 The trans/cis ph
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List of Figuresxiipastel-00527388,
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pastel-00527388, version 1 - 19 Oct
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Introduction 2In this work, we stud
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Bibliography[1] A. Natansohn, P. Ro
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Introduction 6azobenzene-containing
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"##$%&'()')*#'+(%,-.(/#'011'2'"(%)(
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Chapter 1. The azobenzene molecules
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Chapter 2. Experimental setup and s
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pmma-dr1Chapter 2. Experimental set
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Chapter 3pastel-00527388, version 1
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Page 98 and 99: TOPOGRAPHYgratamplxxphotoexpansion
Page 120 and 121: pmmaChapter 3. Microscopic mechanis
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Page 140 and 141: P-250s-4VChapter 4. Photomechanical
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Page 152 and 153: Chapter 5Nanostructured hybrid syst
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Appendix A 156⎛ ⎞ ⎛n g sinθ
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Appendix A 158hence for each compon
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Appendix BPhotoisomerization dynami
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Appendix B 162( 1Since λ 2 = −(
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Appendix C 164L = 5000 nmu = 1 nmL!
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Appendix D 166n. light power densit
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Bibliography[1] A. Natansohn, P. Ro
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Bibliography 170azobenzene-containi
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Bibliography 172as estimated from a
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Bibliography 174[53] C. Barrett, A.
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