Fabrication of ordered array at a nanoscopic level: context

Transcription

1 Fabrication of ordered array at a nanoscopic level: context Top-down method Bottom-up method Classical lithography techniques Fast processes Size limitations it ti E-beam techniques Small sizes Slow processes Nanoimprinting, alternative lithography techniques, Nanomanipulation Small sizes Slow processes Self-assembly process Fast processes Small sizes Control, structural defects Structural limitations

2 Self-organization of nanoparticles Use of forces involved in the self-assembly phenomena to self-organize nanoparticles on a substrate, using various external forces. Examples: Chemically patterned substrate Electric field assisted self- organization Template assisted self-organization Biologically assisted selforganization Optically directed self-organization Solvent evaporation,

3 3D structure colloidal cristals : SiO 2 75nm particles Teflon ring Colloidal l suspension Substrate Film/substrate interface Film surface Film profile (fracture) 1μm 1μm F. Juillerat, P. Bowen, H. Hofmann, submitted and accepted to Langmuir 2005

4 2D structure monolayers: Theoretical approach Rep pulsive pot tential Attractive potential Capil lary forc ce Adhes sion forc ce V F V V PP LSA PW LSA PP H ( D) = 4 κ D 2 2 e ε ε0 a ψ 2a + D π a: Particle radius ( D) = 4π ε aψψ e w κ ( D+ a) A PP 2a 2a 4a + + ln D + 4aD ( D + 2a) ( D + 2a) = 2 A PW a a = + + ln 6 D D+ 2a D+ a PW 1 V H PP C 2 [ h (2 a h ) ][ sin (arcsin( r / a ) α ) ] 2 πγ LV k α ~ D PW FA 4 = 4π aγ SV D: Interparticle separation ψ: Surface potential κ: Debye-Hückel parameter A H : Hamaker constant ( J for silica in water) α: Wetting angle γ LV : Surface tension of the suspending fluid h: Emersion parameter γ SV : Solid-vapor surface energy ( J/m 2 for silica)

5 2D structure monolayers: Theoretical approach SiO 2 75nm particles in H 2 O estimation of the amplitude of the respective contributions at the liquid meniscus h h/2a =1 Attractive Adhesion: ~ N 0 < h/2a < 1 Attractive Capillary: Attractive Adhesion: ~ N ~ N h/2a =0 Attractive Van der Waals: ~10-11 N Repulsive Electrostatic (ph10): ~10-11 N Repulsive Electrostatic (ph2): ~10-12 N h/2a =0 Attractiveti Van der Waals: ~10-17 N Repulsive Electrostatic (ph10): ~10-24 N Repulsive Electrostatic (ph2): ~10-26 N

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7 0D-1D structure: substrates Deposition of an inorganic layer (Cr, SiO 2, ) H. Solak, J. Gobrecht, SLS, PSI Deposition of a PMMA layer (spin-coating) Demagnified image (~2 ) Substrate coated with resist Extreme-UV Interference Lithography (EUV-IL) Silicon wafer Mask with diffraction gratings Pinhole spatial filter Dip-coating Focussed EUV light 2 diffraction gratings 4 diffraction gratings

8 1D structure chains SiO 2 45nm particles PMMA SiO 2 /Cr Si 50nm Long chains of particles over large surface area p = 100nm h = 65nm ph = 10 I = -2 c 10 M p h Chains of agglomerates p = 100nm h = 65nm ph = 2 I c = 10-2 M Short chains p = 100nm h = 65nm ph 10 I c = 10-2 M F. Juillerat, H. Solak, P. Bowen, H. Hofmann, Nanotechnology 2005, 16(8),

9 0D structure isolated particles SiO 2 45nm and Au 50nm particles p = 100nm h = 65nm ph = 10 I c = 10-2 M SiO 2 45nm particles 2 p Gold 50nm particles 100nm 2μm Clusters of 10nm Fe x O y particles (ph = 2, I c = 10-2 M)

10 1D structure chains Gold 15 particles Surface plasmons resonance measurements Polarization of the excitation beam parallel to the particle chains Polarization of the excitation beam perpendicular to the particle chains M. Noyong, U. Simon, RWTH Aachen

11 First, octadecanethiol (C18) is stamped onto a native gold surface via an elastomer stamp, which had been previously dipped into ethanolic C18 solution for a few seconds and dried in air; next, the surface is covered with an aqueous thioglycolate (TG) solution for 1 h, to adsorb TG on the native gold areas For analysis the layer was coated with 20 nm thick gold film deposited via thermal evaporation. Pattern is exposed to a suspension of PS nanoparticles, which had been prepared according to the standard procedure. After 1 h, the suspension is washed off with DI water and a patterned PS particle layer is obtained

12 SEM micrographs of a patterning experiment by utilization of an elastomer stamp with a square pattern as structure for printing. The top micrograph gives a survey (a), while that t on the bottom one demonstrates the particle density within one square (b). Note the onset of regular close packing at several locations within the square. Dimensions of the pattern: squares (24μm) 2, gaps 15μm.

13 Langmuir-Blodget Films

14 Optical microscopic image of a monolayer of 1.4 μm polystyrene- 2,3-epoxypropyl methacrylate (PS- EPMA) (a) and silica (1.7μm) (b) particles transferred from the water/hexane interface. Inset: Corresponding diffraction images withbertrand lens (right insert) and 2DFFT transformation (left insert, 512 x 512 pixels).

15 AFM image of pencil shaped viruses

16 Fabrication methods: Particle synthesis (physical, chemical) Nanocomposite (Polymer based) Severe plastic deformations Template synthesis Biomimetics Self assembly / self organisation of building blocks

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20 Biologically mediated crystal growth Unknown protein selectively determines crystal phase formed Isolate protein+desired crystal phase PCR Refine Result gives highly selective bio-mediated crystal growth Large number of crystals can now be grown A. Belcher, Nature

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