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Thirty Years Ago!

Thirty Years Ago!. At the Max Planck. Resonant Brillouin Scattering. CdTe. Membrane Acoustics: Nanostructures to biological tissues. Supported layers – standing resonances SiON/GaAs; ZnSe/GaAs Freestanding Nanomembranes SiN SiN/Polymer Patterned nanowires Cornea and eye lens. θ.

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Thirty Years Ago!

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  1. Thirty Years Ago!

  2. At the Max Planck Resonant Brillouin Scattering CdTe

  3. Membrane Acoustics: Nanostructures to biological tissues • Supported layers – standing resonances • SiON/GaAs; ZnSe/GaAs • Freestanding Nanomembranes • SiN • SiN/Polymer • Patterned nanowires • Cornea and eye lens

  4. θ Longitudinal Standing Modes SiO3N4/ GaAs ZnSe/ GaAs

  5. Organ Pipe Modes d=3λ/4, f=3V/4d, Second harmonic d=λ, f=V/d Second harmonic

  6. Scattering Intensity E-O Elasto-Optic Contributions Film + Substrate Bortolani, Marvin, Nizzoli, Santoro J. Phys. C. 16, 1757 (1983)

  7. k3f(1) k3f(2) ZnSe k3f(2) k3f(1) GaAs Scattering Intensity

  8. ZnSe/GaAs: BLS Intensity

  9. Freestanding membranes • Ultra-light weight • Robust, pliable, flexible electronics • Mechanical/ elastic properties • Proximity of surfaces ~ phonon wavelengths • Lattice vibrations modified • Increased phonon relaxation rates • Nano-scale heat transport; Quantized thermal conductance • Consequence on electron transport • Composite hard-soft (inorganic-polymer) membranes • Phonon isolation • Lithography on soft layer • Nano-wires/ lines

  10. Freestanding Si3N4 membrane LSM, TSM, Dilational, Flexural Modes

  11. Freestanding Si3N4-PMMA bilayer nano-membranes

  12. PMMA/SiN: dispersion

  13. w = 300nm, D = 100, 200, 300nm h =dP= 75, 65, 60 nm ds = 100 nm Nanowires

  14. Nano-wire Dispersion Odd parity Even parity Resonant Ultrasound Spectroscopy (Migliori)

  15. In-plane Dispersion

  16. Mode Profiles q1= qx= mπ/w, q2= qy = 0 Edge type 1TSM 2TSM m= 0TSM 1TSM

  17. Mode Profiles Finite q

  18. Human Lens • Soft outer cortex, stiff inner nucleus • Transition between stiff nucleus to soft cortex results in mode doublet • No change in frequency and bulk modulus with age (B = ρλ2ν2/4n2). Heys KR, et.al Molecular Vision (2004)

  19. Bovine Lens and Cornea • Probe intact bovine eye globe, power ~5mW. • Frequency (bulk modulus) profile mapped through axial depth of eye globe. • Corneal modulus (BLS) excellent agreement with ultrasonics on same location • Cortex-nucleus transition in bovine lens not seen. • Corneal and lenticular thickness, distance between cornea and lens measured. • Probe fibril structure in cornea? • Bulk Modulus: Human Lens: 3.7 GPa, Bovine Lens: 4.1 GPa, Bovine Cornea: 2.6 GPa Mission, G. Ophthal. Physiol. Opt. 2007 27: 256-264.

  20. Conclusions • BLS of elasticity on nanoscale structures • Standing wave modes (LSM, TSM) distinct role of ripple and e-o contributions • Flexural and Dilational modes • Mode confinement across width and height of rectangular wires – role of sidewalls in trench structures • Corneal and Lens studies – non-invasive probe with potential clinical relevance

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