The Structure Liquid Surfaces P. S. Pershan DEAS & Dept . Of Physics, Harvard Un

The Structure Liquid Surfaces P. S. Pershan DEAS & Dept . Of Physics, Harvard Un www.phwiki.com

The Structure Liquid Surfaces P. S. Pershan DEAS & Dept . Of Physics, Harvard Un

Stradlater, George, Food and Wine Editor has reference to this Academic Journal, PHwiki organized this Journal The Structure Liquid Surfaces P. S. Pershan DEAS & Dept . Of Physics, Harvard Univ. Cambridge, MA 02421 DMR-0124936; NSF 03-03916; DE-FG02-88-ER45379 O. Shpyrko, A. Grigoriev, R. Streitel, P. Pershan, B. Ocko, in addition to M. Deutsch,” Surface Freezing in addition to Quasi-2D Phase Transitions in Binary Metal Liquids,” (March APS 2005) O. G. Shpyrko, A. Y. Grigoriev, R. Streitel, D. Pontoni, P. S. Pershan, M. Deutsch, B. M. Ocko, B. Lin, M Meron, T. Graber, J. Gebhardt, “Atomic-scale surface demixing in a eutectic liquid BiSn alloy.Phys. Rev.Lett. “Submitted (2005). Condensed Matter: 20th Century Solids: Bulk (3d) Structure B in addition to Gaps, exotic Fermi Surfaces, etc Surfaces (2d) Localized Electron States, physisorption, metal/semiconductor interface (rectification), etc. Liquids: Absence of Structure Less Phenomena Bulk (3d): Liquid Structure Factor Surfaces (2d): Surface tension, Langmuir monolayers, wetting. Ancient History of Liquid Surfaces: Pliny the Elder (~50 AD) & Ben Franklin Surfactants (oil) calm water surface waves Modern Era of Surface Science Ref: A. Zangwill, Physics at Surfaces (Cambridge University Press,1988) True emergence of solid state surface physics: Electron Spectroscopy (Brundle, 1974) & Auger Spectroscopy (Harris, 1974) followed by STM, AFM, etc Synchrotron: SSRL(1973), NSLS (1984), APS (1998) X-rays & Surfaces (Solid): Reflectivity (Parratt ’54) Grazing Incidence Diffraction(GID) (Marra, Eisenberger, Cho ’79) New tool: probe buried interfaces in addition to structure far below the surface (i.e. GaAs-Al interface) Liquid Surfaces: Reflectivity: Als-Nielsen in addition to Pershan ‘82 (Liquid Crystal) &’85 (Water): GID: Dutta ‘84 (Langmuir monolayer on water). THIS TALK: X-RAY AND LIQUID SURFACES

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X-Rays in addition to Solid Surfaces Surface In as long as mation: Intensity along truncation rods Extra Peaks due to Surface Phases (reconstruction) Liquid vs Solid Surfaces Surfaces ARE NOT FLAT! Liquid Surface In as long as mation: Surface Structure Factor (Qz) Extra peaks due to Langmuir monolayer or Surface Frozen phases. Surface Roughness Reflectivity Structure Factor + Debye -Waller

Fluctuations of Surface of Bulk Liquid qmax~1/Atom Not (Qxy) Effect of Resolution Scan Detector s Small angles liquids are like solids / large angles they are not! The Liquid Surface Reflectometer HasyLab: Als-Nielsen, Christensen, Pershan, PRL (`82). NSLS: X22B, X19C APS: CHEMMATCARS, CMC, CAT ESRF: ID15A (Alternate Design) H. Reichert ‘03

Data as long as Water with increasing Shpyrko, Fukuto, Pershan, Ocko, Gog, I. Kuzmenko, Deutsch,,Phys. Rev. B (2004). CMC CAT Surface Induced Layering: (Qz) Nematic Surface Smectic-A Order Nematic Phase: 1st Observed Surface Induced Layering First Data (Pershan, Als-Nielsen.PRL, ‘84) RF(Qz) T-TNA 0.05 C 2.8 11.6

Reflectivity & Surface Structure Factor (Layers) When do surface layers appear Quantitative Measure of F(Qz)! Prediction: Constructive Interference Qz=(4p/l)sin a =(2p/D) Molecular Simulations G. A. Chapela, G. Saville, S. M. Thompson, in addition to J. S. Rowlinson, “Computer simulation of a gas-liquid interace”,J. C. S. Faraday Trans II 73, 1133 (1977). Lennard-Jones (12,6) molecules Accepted Lore: Density Profile at Free Surface is Monotonic Liquid Crystals are Different: Why What else is different Simple Thoughts on Surface Layering Order Parameter (r): Electron, Mass, or Particle Density Bulk Susceptibility: Zsurf(Q0)

In Plane Surface Order Digest of Liquid Surface Order Experiments: Simulations: Why are Liquid Metals Different This influences the structure of the surface! Goal: Measure Intrinsic Surface Structure Factor (Qz)

Typical Liquid Metal Measurements Effect of T (Liquid Ga) Structure Factor Thermal Factor Magnussen, Ocko, Regan, Penanen, PershanM. Deutsch ,PRL (1995). Regan, Kawamoto, Pershan, Maskil, Deutsch, Magnussen, Ocko, L. E. Berman, PRL (1995). Tostmann,DiMasi, Pershan, Ocko, Shpyrko, M. Deutsch, PRB (1999). Removal of Thermal Factor Indium T- effects removed & not removed Ga & In with T-effects removed Metallic Layering Is not Due to High Surface Tension In(~550mN/m) Ga(~750mN/m) K(~100mN/m) H2O(73mN/m) H2O vs Liquid Metals

Gibbs Absorption: GaBi Alloy (Bi)= 398 mN/m (Ga)=750 mN/m Monolayer of Bi Coats Liquid Surface Thick Wetting Layer of Bi-Rich Liquid vs Temperature Liquid Metals of Electronic Interest (I): BiSn O. G. Shpyrko, A. Y. Grigoriev, R. Streitel, D. Pontoni, P. S. Pershan, M. Deutsch, B. M. Ocko, Meron, B. Lin .Phys. Rev.Lett. “Submitted (2005). Energy Dispersive Reflectivity 142 °C Tm=138°C Liquid Metals of Electronic Interest (II) Au80.5Si19.5 eutectic alloy Detector (S)-Scan Alloy is Liquid g=780 dynes/cm

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Surface Phase Transition vs T Reflectivity/(RF)2 Phases Not Divided by Thermal Model Density Profiles AuSi(Preliminary) 2D Order of Surface Phases (GID) Truncation Rod Monolayer

In-plane structure model: AuSi2 Low Temperature Phase AuSi, AuGe vs Elements The Future The Buried Liquid/Solid Interface Problems with conventional approach: Absorption in Liquid Bulk Diffuse Scattering Si Abs. Length ~17 mm(70 Kev) Beam Height ~10 m Path ~ 5 mm

Summary Solid vs Liquid Surfaces Reviewed X-ray Methods of Surfaces Special Requirements of Liquids CARS, -CAT, CMC Surface Roughness: Capillary Waves Examples of Liquid Surface Order Liquid Metals vs Non-Metals Alloys: AuSi >10 x Others: Surface Freezing Future: Buried Interfaces (Not DONE @APS)

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