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

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Chapter 5Nanostructured hybrid systemspastel-00527388, version 1 - 19 Oct 2010The photodeformation phenomena observed in azo-containing materials have stimulateda wide variety of possible applications. One of the most studied field is the high densityholographic data storage [1–4], by using the photoinduced deformation to recordinformation. Also, light driven actuation has recently drawn great attention, and thedemonstration of bending free standing films [5–7] and oscillating micro-cantilevers [8]governed by the polarization of the light has shown the feasibility of this kind of applications.Finally, the nanostructuration obtained using the the photodeformable materialsas tools and moulds has been demonstrated to have a great potential in the field ofnanofabrication [9, 10].In this chapter we explore some possible applications of the deformation processesstudied in the previous chapters. These applications concern nanostructured hybridmetal/azo-polymer systems. First, we show preliminary results on the displacement ofgold nanoparticles deposited on the surface of a photochromic film. Then, we presenta large scale parallel nano-patterning experiment based on the combination of opticalpatterning and of subsequent deposition steps. Finally, we show an attempt to usea nano-structured material obtained with this technique for an experiment of opticalpattern transfer.5.1 Gold nanoparticlesIn the previous chapter we have studied the photoresponse of a hybrid metallic/photochromiclayered system, consisting in a 40 nm thick gold layer overlying an azobenzenecontaining photochromic thin film. We have observed that, while inhibiting thephotoexpansion deformation, the presence of the gold layer does not prejudice the massmigration mechanisms. An important question is whether the gold layer is also involved136
Chapter 5. Nanostructured hybrid systems 137in the transport process. In this case, it would be possible to use the photoinduced massmigration for the displacement of objects present on the surface of the photochromicfilm. In order to investigate on this point, we have studied the photo-response of a solgelSi-DR1 photochromic thin film whose surface was coated with gold nanoparticles.5.1.1 Gold nanoparticles on a non functionalized photochromic surfacepastel-00527388, version 1 - 19 Oct 2010In Figure 5.1(a) we show the structures obtained by spin coating, on a sol-gel Si-DR1 free surface, 10 µL of a colloidal solution of gold nanoparticles having a diameterφ = 20 nm synthesized using the Turkevitch method [11]. On the surface, most of thenanoparticles coalesce into 2D aggregates, having sizes ranging from 100 nm to 1 µm,and a thickness equal to a single nanoparticle diameter.The exposure of the sample to p-polarized interfering beams (1 mW/mm 2 per beam,λ = 473 nm) leads to the photo-induced deformation of the hybrid system, which isshown in figures Figure 5.1(b-e). On the left we report the topographic images showingthe time-evolution of the sample topography. In the middle we show the topographyprofile corresponding to the white dotted line, the small white arrow representing thedirection of the cut. In Figure 5.1(c) we also report the optical image (right) and thelight intensity profile (middle-top). The comparison with the corresponding topographyimage (left) and profile (middle-bottom) clearly shows that the deformation of the photochromicfilm in π − phase with the bright fringes of the interference pattern, which isin line with our previous findings.The gold structures follow the surface deformation. As an example, we clearly see thecollapsing of some structures into the evolving grooves, indicated by two white arrowson each image (and the corresponding black arrows on the profiles). On the other hand,all the structures that are located in a dark fringe raise up with the relief growth.However, we do not clearly observe structures located in a bright fringe moving towardsa darker one, so we cannot affirm that lateral displacement is observed. This may bedue to insufficient resolution, supposing that only small particle displacement could beappreciable, while the relative small movement of big structures is not visible or inhibited.On the other hand, it could indicate that the mass migration is more a bulk thana surface process.Similar results are obtained using a higher concentration of nanoparticles. In this caseFigure 5.2(a) we see a more dense aggregation, resulting in a series of gold domains.Exposed to p-polarized interference (b-c), they behave as in the previous case, followingthe deformation of the surface, in π − phase with the bright fringes of the interferencepattern. Plotting the profile of the deformation amplitude’s time evolution (d,
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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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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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Chapter 3. Microscopic mechanisms a
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dose (mJ!mm )(a)dose (mJ!mm )(b)dos
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TOPOGRAPHYgratamplxxphotoexpansion
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Page 134 and 135: sg+goldChapter 4. Photomechanical r
Page 140 and 141: P-250s-4VChapter 4. Photomechanical
Page 146 and 147: P-250s-4VChapter 4. Photomechanical
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Page 168 and 169: Conclusionspastel-00527388, version
Page 170 and 171: Bibliography[1] Chi-Ming Che et Al.
Page 172 and 173: Appendix A 156⎛ ⎞ ⎛n g sinθ
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Page 180 and 181: Appendix C 164L = 5000 nmu = 1 nmL!
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Page 184 and 185: Bibliography[1] A. Natansohn, P. Ro
Page 186 and 187: Bibliography 170azobenzene-containi
Page 188 and 189: Bibliography 172as estimated from a
Page 190 and 191: Bibliography 174[53] C. Barrett, A.
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