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

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pmmaChapter 3. Microscopic mechanisms at the origin of the photo-induced deformation inazobenzene-containing thin films 104PMMA_effic_norm80def_SS_PMMA_20080718_s116090˚PP_PMMAA (nm)402045˚0˚45˚90˚45_PMMA00˚pastel-00527388, version 1 - 19 Oct 2010Emodint(arbitrary units)420-2-4! pol-200 100 200 300 400 500Ipara - Iperp/2Ipara - Iperp/2+EpolEmodpoltime5(s)(a)field_calc_2 15:20:11 29-10-2009! polspeed_corr_newspeed_measuredPMMAsol-gel10.50-0.5-1deformation rate (nm/s)speed_corr0 15 30 45 60 75 90S! (deg.) phi(b)PFigure 3.34: PMMA-DR1: deformation efficiency vs amplitude and polarization spatialmodulation. (a) Mass migration kinetics for SS, PP and ±45 polarizations; (b)SRG growth rate estimated on the first 100 s in PMMA-DR1 () and in sol-gel Si-DR1(□). The variation of η pol is plotted on the same graph (dashed curve).
Chapter 3. Microscopic mechanisms at the origin of the photo-induced deformation inazobenzene-containing thin films 105pastel-00527388, version 1 - 19 Oct 2010a positive sign stands for matter transport towards the zones illuminated with the E ⃗ ⊥field components while a negative sign indicates matter migration away from these zones.According to this sign convention, in PMMA-DR1 s-polarized interference (ϕ = 0 ◦ ) producesnegative deformations, while p-polarized interference (ϕ = 90 ◦ ) and polarizationinterference (ϕ = 45 ◦ ) produce positive deformations.We consider the SRG growth rate during the first 100 s of illumination 28 as the relevantexperimental quantity that characterizes the matter migration efficiency. In Figure3.34(b) we plot this average growth rate, for both PMMA-DR1 () and sol-gelSi-DR1 (□). Clearly, the variation of the SRG growth rate is very different in the twomatrices. As reported in section 3.3.2 for a sol-gel matrix 29 , the matter migration efficiencyis very well described by the spatial modulation of the light field polarization E pol(dashed curve). The mass migration efficiency in PMMA-DR1 results quite uncorrelatedwith the spatial modulation of the polarization, which suggests that in the PMMA matrixE pol is not the appropriate quantity to describe the two mechanisms at the originof the photodeformation. Thus, we define two quantities η pol and η int that characterizethe respective efficiencies of the polarization-driven mechanism and the intensity-drivenmechanism. In order to keep coherence with what we have done for sol-gel samples, wetake η pol = E pol .In order to describe the intensity-driven matter transport mechanism we use a statisticaldirectional displacement model, so-called ’inch-worm’ like motion, similar to the oneproposed in ref. [25]. Under illumination, each molecule has a certain probability ofundergoing isomerization, according to its orientation with respect to the electric field.For each isomerization event, a displacement happens along the molecular axis. Itscontribution to the matter migration across the intensity modulation pattern (i.e. x-axis)depends on the orientation of the molecular axis. For example, molecules excited alongthe x-axis will fully contribute to the displacement, while molecules excited orthogonallyto the x-axis will not contribute. Considering an isotropic angular distribution of themolecules, we can calculate Ω , Ω , the displacement probabilities averagedon Ω = 4π str, corresponding respectively to the illumination with the E ‖ and the E ⊥components: Ω = 4 Ω = 4⎛⎝ 14π⎛28 Where the growth is quasi-linear.29 See Figure 3.13.⎝ 14π∫ π 20∫ π 20∫ πcos 2 (θ)cosθsinθ dθ0∫ πcos 2 (θ)sin 2 (θ) dθ0⎞dφ⎠ = 1 4⎞sinφdφ⎠ = 1 8(3.31)(3.32)
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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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Page 78 and 79: dose (mJ!mm )(a)dose (mJ!mm )(b)dos
Page 98 and 99: TOPOGRAPHYgratamplxxphotoexpansion
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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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Page 168 and 169: Conclusionspastel-00527388, version
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Bibliography[1] Chi-Ming Che et Al.
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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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