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Articles 1 - 8 of 8
Full-Text Articles in Physical Sciences and Mathematics
Determination Of The Goos-Hänchen Shift In Dielectric Waveguides Via Photo Emission Electron Microscopy In The Visible Spectrum, Theodore Stedmark, Robert Campbell Word, Rolf Kӧnenkamp
Determination Of The Goos-Hänchen Shift In Dielectric Waveguides Via Photo Emission Electron Microscopy In The Visible Spectrum, Theodore Stedmark, Robert Campbell Word, Rolf Kӧnenkamp
Physics Faculty Publications and Presentations
Photoemission Electron Microscopy (PEEM) is a versatile tool that relies on the photoelectric effect to produce high-resolution images. Pulse lasers allow for multi-photon PEEM where multiple photons are required excite a single electron. This non-linear process can directly image the near field region of electromagnetic fields in materials. We use this ability here to analyze wave propagation in a linear dielectric waveguide with wavelengths of 410nm and 780nm. The propagation constant of the waveguide can be extracted from the interference pattern created by the coupled and incident light and shows distinct polarization dependence. The electromagnetic field interaction at the boundaries …
Direct Imaging Of Optical Diffraction In Photoemission Electron Microscopy, Robert Campbell Word, Joseph Fitzgerald, Rolf Kӧnenkamp
Direct Imaging Of Optical Diffraction In Photoemission Electron Microscopy, Robert Campbell Word, Joseph Fitzgerald, Rolf Kӧnenkamp
Physics Faculty Publications and Presentations
We report the visualization of optical diffraction at the boundaries of semiconductor and metal nanostructures in non-linear photoemission electron microscopy. We observe light diffracting into photonic and plasmonic modes of planar samples, and into photonic vacuum modes above sample surfaces. In either case, the electron photoemission rate from the sample material is spatially modulated resulting in photoemission images with information on the electric field distribution at the sample/vacuum interface. The resolution in these images is typically ∼30 nm, i.e., significantly below the wavelengths of the exciting light. Optical phase shifts and absorption losses for the diffracted modes can be determined.
Controlled Spatial Switching And Routing Of Surface Plasmons In Designed Single-Crystalline Gold Nanostructures, Rolf Kӧnenkamp, Robert Campbell Word, Joseph Fitzgerald, Athavan Nadarajah, S. D. Saliba
Controlled Spatial Switching And Routing Of Surface Plasmons In Designed Single-Crystalline Gold Nanostructures, Rolf Kӧnenkamp, Robert Campbell Word, Joseph Fitzgerald, Athavan Nadarajah, S. D. Saliba
Physics Faculty Publications and Presentations
Electron emission microscopy is used to visualize plasmonic routing in gold nano-structures. We show that in single-crystalline gold structures reliable routing can be achieved with polarization switching. The routing is due to the polarization dependence of the photon-to-plasmon coupling, which controls the mode distribution in the plasmonic gold film. We use specifically designed, single-crystalline planar structures. In these structures, the plasmon propagation length is sufficiently large such that significant plasmon power can be delivered to the near-field region around the end tips of the router. Solid state devices based on internal electron excitation and emission processes appear feasible.
Proton-Fountain Electric-Field-Assisted Nanolithography (Pen): Fabrication Of Polymer Nanostructures That Respond To Chemical And Electrical Stimuli. An Overview In The Context Of The Top-Down And Bottom-Up Approaches To Nanotechnology, Andres H. La Rosa, Mingdi Yan, Rodolfo Fernandez, Elia Zegarra
Proton-Fountain Electric-Field-Assisted Nanolithography (Pen): Fabrication Of Polymer Nanostructures That Respond To Chemical And Electrical Stimuli. An Overview In The Context Of The Top-Down And Bottom-Up Approaches To Nanotechnology, Andres H. La Rosa, Mingdi Yan, Rodolfo Fernandez, Elia Zegarra
Physics Faculty Publications and Presentations
The development of chemically functionalized materials, such that their physical properties can vary in response to external mechanical, chemical, or optical stimuli, offers potential applications in a wide range of fields, namely microfluidics, electronic memory devices, sensors and actuators. In particular, patterned structures built with stimuli-responsive polymer materials are attractive due to their inherent lower cost production and for building soft scaffolds that mimic closer natural bio-environments. In addition, harnessing the construction of patterns with nanoscale dimensions would not only a) allow building lab-on-a-chip devices that require minimal chemical reactants volumes, but also b) find applications in the area of …
Photoemission From Localized Surface Plasmons In Fractal Metal Nanostructures, Robert Campbell Word, Rolf Könenkamp, T. T. Dornan
Photoemission From Localized Surface Plasmons In Fractal Metal Nanostructures, Robert Campbell Word, Rolf Könenkamp, T. T. Dornan
Physics Faculty Publications and Presentations
We use photoemission microscopy to characterize localized surface plasmon distributions in nanostructured gold layers on indium-tin-oxide/glass substrates. The Au films have a fractal dimension of ∼1.3 and smallest feature sizes of ∼100 nm. We use femtosecond laser pulses at a wavelength of ∼800 nm for the plasmon excitation. Photoelectron emission occurs by a three-photon process in localized areas of indium-tin-oxide with ∼70 nm diameter. In these areas the photoemission rate is enhanced several thousand fold compared to nonstructured surface areas. The results show that plasmon enhanced photoemission can be induced in a nonabsorbing material in proximity to a plasmon-active metal …
Electron Microscopy And Optical Characterization Of Cadmium Sulphide Nanocrystals Deposited On The Patterned Surface Of Diatom Biosilica, Timothy Gutu, Debra K. Gale, Clayton Jeffryes, Wei Wang, Chih-Hung Chang, Gregory L. Rorrer, Jun Jiao
Electron Microscopy And Optical Characterization Of Cadmium Sulphide Nanocrystals Deposited On The Patterned Surface Of Diatom Biosilica, Timothy Gutu, Debra K. Gale, Clayton Jeffryes, Wei Wang, Chih-Hung Chang, Gregory L. Rorrer, Jun Jiao
Physics Faculty Publications and Presentations
Intricately patterned biosilica obtained from the shell of unicellular algae called diatoms serve as novel templates for fabrication of optoelectronic nanostructures. In this study, the surface of diatom frustules that possessed hierarchical architecture ordered at the micro and nanoscale was coated with a nanostructured polycrystalline cadmium sulphide (CdS) thin film using a chemical bath deposition technique. The CdS thin film was composed of spherical nanoparticles with a diameter of about 75 nm. The CdS nanoparticle thin film imparted new photoluminescent properties to the intricately patterned diatom nanostructure. The imparted photoluminescent properties were dependent on the CdS coverage onto the frustules …
Nano-Structure Formation Driven By Local Protonation Of Polymer Thin Films, Carsten Maedler, Harald Graaf, Mingdi Yan, Andres H. La Rosa
Nano-Structure Formation Driven By Local Protonation Of Polymer Thin Films, Carsten Maedler, Harald Graaf, Mingdi Yan, Andres H. La Rosa
Physics Faculty Publications and Presentations
We report the creation of nano-structures via Dip Pen Nanolithography by locally exploiting the mechanical response of polymer thin films to an acidic environment. Protonation of cross linked poly(4-vinylpyridine) (P4VP) leads to a swelling of the polymer. We studied this process by using an AFM tip coated with a pH 4 buffer. Protons migrate through a water meniscus between tip and sample into the polymer matrix and interact with the nitrogen of the pyridyl group forming a pyridinium cation. The increase in film thickness, which is due to Coulomb repulsion between the charged centers, was investigated using Atomic Force Microscopy. …
Creation Of Nanopatterns By Local Protonation Of P4vp Via Dip Pen Nanolithography, Carsten Maedler, S. Chada, Xiquan Cui, M. Taylor, Mingdi Yan, Andres H. La Rosa
Creation Of Nanopatterns By Local Protonation Of P4vp Via Dip Pen Nanolithography, Carsten Maedler, S. Chada, Xiquan Cui, M. Taylor, Mingdi Yan, Andres H. La Rosa
Physics Faculty Publications and Presentations
The elastic mechanical response of a poly(4-vinylpyridine) film is exploited to create nanostructures under ambient conditions via dip pen nanolithography. Using a pH 4 phosphate buffer solution as the "ink," a series of experimental results indicates that the nanometer-sized structures are due to local swelling of the film’s pyridyl groups upon their protonation with the hydronium ions delivered by the tip. Control over the structures’ height is gained by properly selecting the writing velocities or the dwell time, respectively.