Nanomaterials and their Optical Applications Winter Semester 2013 Lecture 04 rachel.grange@uni-jena.de http://www.iap.uni-jena.de/multiphoton
Module enrolment & Exams 2 Do not forget: module enrolment ( within few weeks) Exam form: oral or written, it depends on the numbre of student Examinations date: Tuesday 11 of February 2013 9-10h30 Website for Lecture Materials http://www.iap.uni-jena.de/teaching.html Labwork / HiWi position Send me your CV / transcript of record and motivations!
Bottom-up approaches 3 1. Epitaxial Growth Molecular beam epitaxy (MBE) Metal-organic chemical vapor deposition (MOCVD) Chemical beam epitaxy, Liquid-phase epitaxy, Laserassisted vapor deposition 2. Nanochemistry Self-assembly or seld organisation Micelles Films Colloidal synthesis
Why nanochemsitry? 4 Challenge To use chemical approaches to provide a precise control of composition, size and shape of the nanomaterials product formed Capabilites of nanochemistry: Preparation of nanoparticles of a wide range of metals, semiconductors, glasses, polymers, Preparation of multilayer structures, core-shell type of nanoparticles Nanopatterning of surfaces, surface functionalization and self-assembling of structures on this patterned template Organization of nanoparticles into periodic or aperiodic functional structures In situ fabrication of nanoscale probe, sensors and devices
Bottom-up approaches 5 Common aspects of all bottom-up approaches It involves thermodynamics and chemical kinetics Entropy plays a central role in self-assembling systems made by equilibrium methods Self-assembly of complex structures requires achieving just the right balance between entropy at a given temperature and the binding enthalpies of the various components Kinetic, relying on trapping the system in some nonequilibrium configuration by rapidly changing the concentration of a reactant, changing the solvent, or changing the temperature of the system
Bottom-up approaches 6 Chemical synthesis since the alchemists! synthetic methods, tools, and analytical techniques used by organic chemists Bottom-up : making complex nanostructures starting from the random collisions of the components dissolved in a solvent Complex macroscopic organisms emerge from the chaotic soup of the fertilized egg, and it is this self assembly of living systems that provides much of the inspiration for current research in this field. Entropy plays a central role in self-assembling systems made by equilibrium methods. The final structure must be reasonably stable at room temperature, but it also must be weakly enough bound so that erroneous structures dissociate, allowing the system to explore the large number of configurations needed to find the desired configuration of lowest free energy. Self-assembly of complex structures requires achieving just the right balance between entropy at a given temperature and the binding enthalpies of the various components. Kinetic methods rely on trapping the system in some nonequilibrium configuration by rapidly changing the concentration of a reactant, changing the solvent, or changing the temperature of the system.
Why is chemistry key in nanosciences? 7 Small structures have large surface to volume ratios The surfaces are covered with atoms, atoms that cannot satisfy chemical bonding requirements with the neighboring atom of the same material Experiments frequently require that nanoparticles, whether they be biological molecules or solid-state particles, be placed at specific locations on a solid surface.
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Bottom-up: self-organisation 9 Organic molecule for optoelectronics : must contain a certain amount of carbone Flexible Synthetic chemistry possible Molecule based device possible Spherical micelle Taken from rachel.grange@uni-jena.de Andreas Borgschulte Lecture 04
Bottom-up: self-organisation 10 Organic molecule for optoelectronics : must contain a certain amount of carbone Flexible Synthetic chemistry possible Molecule based device possible Spherical micelle Taken from rachel.grange@uni-jena.de Andreas Borgschulte Lecture 04
Reverse micelle synthesis 11 http://acswebcontent.acs.org/prfar/2011/paper11580.html
Bottom-up: self-organisation 12 Films Langmuir-Blodgett films = assemblies of hydrophilic and hydrophobic tails Chemical reactions: sel-assembly monolayer Chemisorption: -SH (sulfuric group or thiol) desorbs on gold
Colloidal suspensions 13 The synthesis of small particles as precipitates from solution phase reactions potassium iodide lead nitrate Lead iodide Faraday 1857 http://www.chembio.uoguelph.ca/edu cmat/chm19104/periodic/pbi2.jpg Wikipedia
Colloidal suspensions 14 Movie about the synthesis of CdSe http://chemgroups.northwestern.edu/odom/nan o-synthesis/cdse-trialframes.htm A cold solution of one of the components is injected into a hot solution of the other component. A precipitation reaction begins as soon as the two components intermingle, and because of the rapid cooling caused by the injection of the cold solution, further growth of crystallites is halted. The solution is subsequently reheated, causing small crystallites (which have a larger surface to volume ratio and are therefore less stable) to dissolve and recrystalize onto more stable existing crystallites to produce a much more uniform size distribution of crystallites (a process called Ostwald ripening)
Bottom-up: Kinetic control of growth 15 Vapor-liquid-solid method With catalyst a catalytic liquid alloy phase which can rapidly adsorb a vapor to supersaturation levels, and from which crystal growth can subsequently occur from nucleated seeds at the liquid solid interface. vapor phase deposition of silicon gold nanoparticle used as a seed for the growth of a silicon nanowire gold nanoparticles are deposited onto a surface and heated in the presence of the precursors that generate silicon (chemical vapor deposition) The silicon is rapidly incorporated into the gold to form a liquid alloy, which, when saturated with silicon, produces a silicon precipitate that grows under the nano droplet
Bottom-up: Kinetic control of growth 16 Template-wetting Infiltration of porous templates by precursor wetting Infiltration of polymers by capillary wetting
Bottom-up: colloidal synthesis 17 Tubes and wires Solution phase synthesis Hydrothermal synthesis = various techniques of crystallizing substances from high-temperature aqueous solutions at high vapor pressures Molten-salt synthesis KNbO3 NaNbO3 LiNbO 3 a) b) c) 2 m m 1 m
Bottom-up: self-organisation 18 Mostly metallic and inorganic material: gold, silver, ferroelectric oxides Sol-gel = starting from a chemical solution (sol, short for solution) which acts as the precursor for an integrated network (or gel) Pyramids, stars, NIST physicist Angela R. Hight Walker
Characterization of nanostructures 19 1. Optical microscopy Bright and dark field, fluorescence, confocal, High resolution: PALM (STORM), STED 2. Electron microscopy : SEM, TEM 3. Scanning probe microscopy: STM, AFM 4. Near field microscopy: SNOM 5. X-ray diffraction: XRD, EDS Chapter 4 in Basics of Nanotechnology,, Rubahn
Optical microscopy 20 1. Bright field vs dark field
Optical microscopy 21 Phase contrast Bright field Cross-polarized Dark field sample contrast comes from interference of different path lengths of light through the sample. sample contrast comes from absorbance of light in the sample. illumination, sample contrast comes from rotation of polarized light through the sample. illumination, sample contrast comes from light scattered by the sample. http://en.wikipedia.org/wiki/phase_contrast_microscopy
Optical microscopy 22 2. Confocal microscope The Journal of Cell Biology, Volume 105, 1987 3. Microscopy with fluorescent marker http://www.olympusconfocal.com/theory/index.html GFPs www.invitrogen.com QDs Dr. Kalju Kahn at UCSB
Optical microscopy 23 4. Nonlinear microscopy Single-photon vs two-photon confocal Small excitation volume Longer wavelength SHG 2-photon fluorescence Laser pump 400 425 450 (> 450 nm) 800 850 900
Optical microscopy 24 5. High resolution microscopy Photoactivated Localization Microscopy (PALM) Stochastic Optical Reconstruction Microscopy (STORM) 20 nm resolution Stimulated Emission Depletion microscopy, or STED microscopy 5.8 nm
Electron microscopy 25 Scanning electron microscope (SEM) 0.5 kev to 40 kev spot about 0.4 nm to 5 nm in diameter Reflected eletron Conductive substrate Surface technique Transmission electron microscopy (TEM) Ultrathin sample On a grid Diffraction is possible Inside structure Transmitted electrons SEM tutorial http://www.chems.msu.edu/reso urces/tutorials/sem http://www.lfg.techfak.uni-erlangen.de/forschung/rtaylor/index.shtml
How does the SEM works? 26 The electron beam hits the sample, producing secondary electrons from the sample. These electrons are collected by a secondary detector or a backscatter detector, converted to a voltage, and amplified. rachel.grange@uni-jena.de http://www-archive.mse.iastate.edu/microscopy/path.html Lecture 04
How does the TEM works? 27 The electron beam then travels through the specimen you want to study. Depending on the density of the material present, some of the electrons are scattered and disappear from the beam. At the bottom of the microscope the unscattered electrons hit a fluorescent screen, which gives rise to a "shadow image" of the specimen with its different parts displayed in varied darkness according to their density. The image can be studied directly by the operator or photographed with a camera. http://www.nobelprize.org/educational/physics/micros copes/tem/index.html The Nobel Prize in Physics, 1986 Ernst Ruska http://en.wikipedia.org
Scanning probe microscopy: STM, AFM 28 Scanning tunneling microscope (STM) An extremely fine conducting probe is held close to the sample. Electrons tunnel between the surface and the stylus, producing an electrical signal. The stylus is extremely sharp, the tip being formed by one single atom. It slowly scans across the surface at a distance of only an atom's diameter. The Nobel Prize in Physics, 1986 Gerd Binnig and Heinrich Rohrer http://www.nobelprize.org/educational/physics/microscopes/scanning/index.htm
Scanning probe microscopy: STM, AFM 29 Atomic force microscopy (AFM) scanning force microscopy (SFM) The AFM consists of a cantilever with a sharp tip (probe) at its end that is used to scan the specimen surface. The cantilever is typically silicon or silicon nitride with a tip radius of curvature on the order of nanometers. When the tip is brought into proximity of a sample surface, forces between the tip and the sample lead to a deflection of the cantilever according to Hooke's law. Depending on the situation, forces that are measured in AFM include mechanical contact force, van der Waals forces, capillary forces, chemical bonding, electrostatic forces, magnetic forces http://en.wikipedia.org
Near field microscopy : SNOM, PSTM 30 = mix between an AFM and an optical microscope a microscopy technique for nanostructure investigation that breaks the far field resolution limit by exploiting the properties of evanescent waves. This is done by placing the detector very close (distance much smaller than wavelength λ) to the specimen surface. 2 modes of operation Aperture probe Apertureless probe
Near field microscopy : SNOM, PSTM 31 = mix between an AFM and an optical microscope a microscopy technique for nanostructure investigation that breaks the far field resolution limit by exploiting the properties of evanescent waves. This is done by placing the detector very close (distance much smaller than wavelength λ) to the specimen surface. 2 modes of operation Aperture probe Apertureless probe
Near field microscopy : SNOM, PSTM 32 SNOM = NSOM= Scanning Near- Field Optical Microscopy, Photon Scanning Tunneling Microscope = PSTM = apertureless probe, evanescent waves created at the sample surface by oblique far-field illumination http://www.olympusmicro.com In the aperture case, light emanates from a small aperture (~ 20-100 nm), usually a hole drilled in a metal-coated optical fibre, giving a spatial resolution of ~ 50-100 nm. Low throughput, poor resolution and poor topography limit this technique. In the apertureless or tip-enhanced case, light is scattered from a sharp metal tip (typically 20-50 nm radius). This typically gives a resolution of 10-30 nm. Efficient scattering, the ability to combine with Atomic Force Microscopy (AFM), and spectroscopic measurements have enabled this technique to dominate over recent years. http://www.see.ed.ac.uk/cbee/snom1.html
X-ray diffraction 33 XRD, powder diffraction To characterize the crystalline form and sizes How? Elastic scattering of x-ray by a periodic lattice : well known Bragg equation Stoichiometry and the lattice constant Energy-dispersive X-ray spectroscopy (EDS or EDX)
Outline: Plasmonics 34 1. Plasmonics vs Electronics and Photonics a) Definitions: plasmon, polariton b) Surface plasmon polariton: Drude Model c) Localized surface plasmon: nanoparticles, nanorods, nanoshells d) Theoretical modelling : light scattering theory (Rayleigh and Mie) 2. Fabrication of Plasmonics nanostructures 3. Applications of plasmonics: Stained glass, Notre Dame de Paris, 1250
Why plasmonics? 35 The speed of photonics The size of electronics High transparency of dielectrics like optical fibre Data transport over long distances Very high data rate Nanoscale data storage Limited speed due to interconnect Delay times Brongersma, M.L. & Shalaev, V.M. The case for plasmonics. Science 328, 440-441 (2010).
Definition of Plasmonics 36 Metallic nanostructures = the field of plasmonics Not the confinment of electrons or holes as in semiconductors dots but Electrodynamics effect Modification of the dielectric environment How does plasmonic material look like? Metallic thin film Metallic nanoparticle Metallic nanorod Metallic nanoshell Different point of view of SURFACE PLASMON: Lycurgus cup (British Museum, London, UK). Electrodynamic: surface wave like in radiowave propagation along the earth Optics: modes of an interface Solid-state physics: collective oscillations of electrons
Plasmon 37 rachel.grange@uni-jena.de http://www.chemistry-blog.com/?s=plasmonics Lecture 04
Plasmon 38 rachel.grange@uni-jena.de http://www.chemistry-blog.com/?s=plasmonics Lecture 04
Plasmon 39 Special case when the charges are confined to the surface of a metal rachel.grange@uni-jena.de http://www.chemistry-blog.com/?s=plasmonics Lecture 04
Outlook 40 J. a Fan, C. Wu, K. Bao, J. Bao, R. Bardhan, N. J. Halas, V. N. Manoharan, P. Nordlander, G. Shvets, and F. Capasso, Selfassembled plasmonic nanoparticle clusters., Science, vol. 328, no. 5982, pp. 1135 8, May 2010. H. Atwater, The promis of Plasmonics, Scientific Amercian, 2007 Brongersma, M.L. & Shalaev, V.M. The case for plasmonics. Science 328, 440-441 (2010). D. W. Hahn, Light scattering theory, Notes, July 2009