2017年6月5日（月）
Effect of substrate flexibility on growth of AgCl nanorods.
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The growth mechanism of AgCl NRs on flexible film
The AgCl NRs grew rapidly as the substrate became thin (Fig. 2). To investigate the dependence of growth characteristics on the kind of substrate, XRD was measured on Ag-deposited PI film (Fig. 7a), glass (Fig. 7b) and c-sapphire (Supplementary Fig. 6) as a function of plasma time. As-deposited Ag film showed only metallic Ag peaks. As the plasma exposure time increased, AgCl peaks began to appear and the Ag peaks weakened. The ratio of AgCl (Fig. 7c) (that is, [area of AgCl peak]/[total areas of AgCl and Ag peaks]) reached 1.0 within 20 s on the PI film but it took 120 s on both glass and on c-sapphire; that is, AgCl grew six times faster on PI film than on the glass and on the c-sapphire. This fast growth on PI is due to the spontaneous bending with convex shape during the Cl2 plasma treatment (Fig. 7d). During NR growth, the flexible thin PI could bend to minimize the strain energy induced by lattice mismatch between Ag and AgCl, but the inflexible thick polycarbonate (PC) film and glass did not bend. This difference occurs because the PI film has the smallest bending radius due to its low thickness (d) and low Young’s modulus (E) from the Stoney equation50 (PI film: dPI=100 μm, EPI=2.5 GPa; glass: dglass=700 μm, Eglass=74 GPa). The details are described in Supplementary Table 1.
Figure 7: Effect of substrate flexibility on growth of AgCl nanorods.
Figure 7
X-ray diffraction (XRD) patterns of Cl2-exposed Ag film as a function of exposure time on (a) polyimide and (b) soda-lime glass; Ag (black squares); AgCl (red circles). (c) Partial AgCl ratio calculated from XRD patterns. (d) Photography of Ag-coated 100-μm-thick polyimide (PI), 130-μm-thick polyethylene terephthalate (PET), 500-μm-thick polycarbonate (PC) films and 700-μm-thick soda lime glass during Cl2 exposure. Calculated gradient of strain under volume expansion from Ag to AgCl on (e) rigid glass and (f) flexible PI film. Volume expansion was assumed to occur at interface of AgCl nanorods with Ag film. In flexible PI film, strain was localized at bottoms of AgCl nanorods.
Full size image
The growth mechanism of AgCl NRs on flexible film
The AgCl NRs grew rapidly as the substrate became thin (Fig. 2). To investigate the dependence of growth characteristics on the kind of substrate, XRD was measured on Ag-deposited PI film (Fig. 7a), glass (Fig. 7b) and c-sapphire (Supplementary Fig. 6) as a function of plasma time. As-deposited Ag film showed only metallic Ag peaks. As the plasma exposure time increased, AgCl peaks began to appear and the Ag peaks weakened. The ratio of AgCl (Fig. 7c) (that is, [area of AgCl peak]/[total areas of AgCl and Ag peaks]) reached 1.0 within 20 s on the PI film but it took 120 s on both glass and on c-sapphire; that is, AgCl grew six times faster on PI film than on the glass and on the c-sapphire. This fast growth on PI is due to the spontaneous bending with convex shape during the Cl2 plasma treatment (Fig. 7d). During NR growth, the flexible thin PI could bend to minimize the strain energy induced by lattice mismatch between Ag and AgCl, but the inflexible thick polycarbonate (PC) film and glass did not bend. This difference occurs because the PI film has the smallest bending radius due to its low thickness (d) and low Young’s modulus (E) from the Stoney equation50 (PI film: dPI=100 μm, EPI=2.5 GPa; glass: dglass=700 μm, Eglass=74 GPa). The details are described in Supplementary Table 1.
Figure 7: Effect of substrate flexibility on growth of AgCl nanorods.
Figure 7
X-ray diffraction (XRD) patterns of Cl2-exposed Ag film as a function of exposure time on (a) polyimide and (b) soda-lime glass; Ag (black squares); AgCl (red circles). (c) Partial AgCl ratio calculated from XRD patterns. (d) Photography of Ag-coated 100-μm-thick polyimide (PI), 130-μm-thick polyethylene terephthalate (PET), 500-μm-thick polycarbonate (PC) films and 700-μm-thick soda lime glass during Cl2 exposure. Calculated gradient of strain under volume expansion from Ag to AgCl on (e) rigid glass and (f) flexible PI film. Volume expansion was assumed to occur at interface of AgCl nanorods with Ag film. In flexible PI film, strain was localized at bottoms of AgCl nanorods.
Full size image
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