Laboratory for Surface Modification (LSM)

Seminars Archives

September 2017 | October 2017 | November 2017

Thursday, October 05, 2017
Plasmons in Complex Materials
Stephanie Law
Materials Science and Engineering
University of Delaware
12:00 Noon CHEM 260

The fields of plasmonics and metamaterials have seen significant growth in recent years, due to the interest in confining light to subwavelength volumes both for fundamental physics studies as well as novel device architectures. Much of this work has been done in the visible spectral range with traditional metals such as gold and silver. In this talk, I will discuss our work using heavily-doped InAs grown by molecular beam epitaxy for mid-infrared plasmonic and metamaterial devices. I will explain the advantages of these new materials over traditional plasmonic materials in the infrared and demonstrate that they act as near-perfect Drude metals with tunable optical properties that can also be integrated with existing semiconductor optoelectronic devices. I will present work on the growth of metamaterials and demonstrate both bulk negative refraction as well as the excitation of high-wavevector volume plasmon polaritons. I will close by discussing some of our recent work using topological insulators as THz plasmonic materials. We have mapped out the dispersion relation for the plasmons excited in these materials and have demonstrated that they are indeed Dirac plasmons.
Thursday, October 19, 2017
CANCELLED Tuning Quantum Materials with Uniaxial Strain
Abhay Narayan Pasupathy
Columbia University
12:00 Noon CHEM 260

What is the effect of stretching a crystal along a given direction by a small amount? In general, one might not expect much: a change in lattice constant, accompanied by corresponding changes in the electronic and vibrational properties of a crystal. I will describe a few cases of materials where the effect of stretching (ie, uniaxial strain) lead to large and unexpected effects. These include the iron-based superconductors (where large electronic nematic effects are seen), layered transition-metal dichalcogenides (where we can observe the formation of strain solitons) and two-dimensional semiconductors (where we can cause large changes in band gap and even cause structural phase transitions). I will discuss these from an experimental perspective - in particular, I will describe new experimental techniques where we can apply calibrated uniaxial strain to crystals and measure their response with atomic-resolution scanning tunneling microscopy techniques.
Thursday, October 26, 2017
CANCELLED: Science and Applications of Optical Metamaterials
Gennady Shvets
Cornell University
12:00 Noon CHEM 260

Metamaterials are artificial electromagnetic materials exhibiting unusual optical responses that are difficult to elicit from naturally-occurring media. Those include negative refractive index, strong magneto-electric response, and strong concentration of optical energy. Metamaterials and their two-dimensional implementations (metasurfaces) represent a remarkably versatile platform for light manipulation, biological and chemical sensing, and nonlinear optics. Many of these applications rely on the resonant nature of metamaterials, which is the basis for extreme spectrally selective concentration of optical energy in the near field. In addition, metamaterial-based optical devices lend themselves to considerable miniaturization because of their sub-wavelength features. I will review the history of electromagnetic metamaterials, which is now fifteen years in the making, and review some of the more recent trends in metamaterials research and applications using the examples of my group’s work. Those include (i) the development of “active” (i.e. rapidly tunable and reconfigurable) metasurfaces functionalized with single-layer graphene, (ii) applications of metamaterials to chemical and biological sensing of proteins and cellular membranes, and (iii) the development of the so-called photonic topological insulators that emulate the eponymous electronic materials. Recent experimental results covering a wide swath of the electromagnetic spectrum (from microwaves to infrared light) will be presented.
Friday, October 27, 2017
Structural, optical and gas sensing properties of swift heavy ions irradiated metal oxide thin films
Azher Siddiqui
Department of Physics
Jamia Millia Islamia, New Delhi
1:30 pm - NPL 201

In this work, we report the effects of 100 MeV Ag9+ and O7+ ions irradiation on the structural, optical and gas sensing properties of thermally oxidized thin films of tin and indium. XRD, SEM and RBS techniques have been employed to study the structural, modifications induced in the films as a result of irradiation. It was observed that irradiation with 100 MeV Ag9+ and O7+ ions resulted in a decrease in the crystallinity of the films along with a decrease in the grain size due to increase in the lattice strain. The structural modifications induced have been correlated with the simulations based on the thermal spike model. The optical properties of the pristine and SHI irradiated films was examined using UV-Vis spectroscopy. It was noticed that the optical band gap of the films increased upon irradiation with 100 MeV Ag9+ and O7+ ions. The changes in the response characteristics of indium oxide and tin oxide films towards methane and hydrogen respectively due to SHI irradiation are extensively discussed.

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