Déformation photoinduite dans les films minces contenant des ...

Chapter 3. Microscopic mechanisms at the origin of the photo-induced deformation inazobenzene-containing thin films 85()*%+,-./"01"420T (a. u.)()233*3+/"801"40timeI/I 0 !0 1 2 3 4 5A (nm)180-180 1 2 3 4 5A (nm)0-10-2000 100 200TIME (s)20090309_15 20090206_220090206_2!"I/I 0 !P-assistONP-interfON3(a) (b)X (!m)(c)time8400 1 2 3 4 58400 1 2 3 4 5A (nm)#"$%&'"0-30 1 2 3 4 5X (!m)180-180 1 2 3 4 5pastel-00527388, version 1 - 19 Oct 2010A (nm)-10-200-40-800 400 800p-interf.+ Pp-interf.20090310_20 100 200TIME (s)!"I/I 0 !00 1 2 3 4 5X (!m)lightON(d) (e) OPTICS (f)84A (nm)30-30 1 2 3 4 5X (!m)TOPOGRAPHYFigure 3.21: Photoinduced SRG formation with a p interference pattern assistedwith a p-polarized incoherent beam. Laser power density = 1 mW/mm 2 per beam(blue), 2.1 mW/mm 2 per beam (green); sample = sol-gel Si-DR1 ≃ 200 nm thick.(a-c) delayed assisting beam: (a) light profile (top) and the corresponding deformationamplitude (bottom, solid curve), the dotted curve indicates the deformation withoutthe assisting beam; (b) and (c) optical and topographical images recorded in the timerange of curve (a), scanning over one line, scan range = 5 µm; (d-f) same as (a-c) butwith simultaneous interfering and assisting beams: the inset in (d) represents the timeevolution over 800 s.t = 0. Subsequently, we clearly see that matter migration is less efficient then in thenon assisted case.Finally, in Figure 3.22 we report the photodeformation effects obtained under s-polarized assisting and interfering beams, which are simultaneously activated at t = 0. SS+SAs in the other cases, matrix photoexpansion is measured right after the exposure, withthe formation of weak amplitude gratings. Then the deformation amplitude drops tozero, producing almost a surface flattening after about 30 s, in agreement with previousresults [16]. Therefore, no matter migration is observed.The results so far obtained are summarized in Table 3.2. In particular, we notice that