Abstract:The search for alternative plasmonic materials with improved optical properties, easier fabrication and integration capabilities over those of the traditional materials such as silver and gold could ultimately lead to real-life applications for plasmonics and metamaterials. In this work, we show that titanium nitride could perform as an alternative plasmonic material in the visible and near-infrared regions. We demonstrate the excitation of surface-plasmon-polaritons on titanium nitride thin films and discuss the performance of various plasmonic and metamaterial structures with titanium nitride as the plasmonic component. We also show that titanium nitride could provide performance that is comparable to that of gold for plasmonic applications and can significantly outperform gold and silver for transformation-optics and some metamaterial applications in the visible and near-infrared regions. References and links1. W. Barnes, A. Dereux, and T. Ebbesen, "Surface plasmon subwavelength optics," Nature 424, 824-830 (2003). 2. S. Lal, S. Link, and N. Halas, "Nano-optics from sensing to waveguiding," Nat. Photonics 1, 641-648 (2007). 3. D. Smith, J. Pendry, and M. Wiltshire, "Metamaterials and negative refractive index," Science 305, 788-792 (2004). 4. W. Cai and V. Shalaev, Optical Metamaterials: Fundamentals and Applications (Springer Verlag, 2009). 5. J. Pendry, D. Schurig, and D. Smith, "Controlling electromagnetic fields," Science 312, 1780-1782 (2006). 6. C. Soukoulis, S. Linden, and M. Wegener, "Physics: negative refractive index at optical wavelengths," Science 315, 47-49 (2007). 7. V. Shalaev, "Transforming light," Science 322, 384-386 (2008). 8. J. Pendry, "Negative refraction makes a perfect lens," Phys. Rev. Lett. 85, 3966-3969 (2000). 9. Z. Jacob, L. Alekseyev, and E. Narimanov, "Optical Hyperlens: Far-field imaging beyond the diffraction limit,"Opt. Express 14, 8247-8256 (2006). 10. S. Ramakrishna, J. Pendry, M. Wiltshire, and W. Stewart, "Imaging the near field," J. Mod. Opt. 50, 1419-1430 (2003). 11. W. Cai, U. Chettiar, A. Kildishev, and V. Shalaev, "Optical cloaking with metamaterials," Nat. Photonics 1, 224-227 (2007). 12. A. Kildishev and V. Shalaev, "Engineering space for light via transformation optics," Opt. Lett. 33, 43-45 (2008). 13. E. Narimanov and A. Kildishev, "Optical black hole: Broadband omnidirectional light absorber," Appl. Phys.Lett. 95, 041106 (2009). 14. N. Fang, H. Lee, C. Sun, and X. Zhang, "Sub-diffraction-limited optical imaging with a silver superlens," Science 308, 534-537 (2005). (Springer Verlag, 2007). 51. A. Hibbins, J. Sambles, and C. Lawrence, "Surface plasmon-polariton study of the optical dielectric function of titanium nitride," J. Mod. Opt. 45, 2051-2062 (1998). 52. X. Ni, Z. Liu, A. Boltasseva, and A. Kildishev, "The validation of the parallel three-dimensional solver for analysis of optical plasmonic bi-periodic multilayer nanostructures," Appl. Phys. A 100, 365-374 (2010).

Indium–gallium nitride (InGaN) multiple-quantum-well (MQW) light-emitting diode (LED) membranes, prefabricated on sapphire growth substrates, were created using pulsed-excimer laser processing. The thin-film InGaN MQW LED structures, grown on sapphire substrates, were first bonded onto a Si support substrate with an ethyl cyanoacrylate-based adhesive. A single 600 mJ/cm2, 38 ns KrF (248 nm) excimer laser pulse was directed through the transparent sapphire, followed by a low-temperature heat treatment to remove the substrate. Free-standing InGaN LED membranes were then fabricated by immersing the InGaN LED/adhesive/Si structure in acetone to release the device from the supporting Si substrate. The current–voltage characteristics and room-temperature emission spectrum of the LEDs before and after laser lift-off were unchanged.

Narrow Bi2Te3 nanowire arrays, where the individual wires are dense and parallel, have been fabricated by electrodeposition. The array–template composites have a high wire density over a large area (see Figure) and are relatively thick, which makes them ideally suited for direct incorporation into existing device structures for thermoelectric or other applications.

Gallium nitride thin films grown on sapphire substrates were successfully separated and transferred onto Si substrates using single 38 ns KrF excimer laser pulses directed through the transparent substrate at fluences in the range of 400–600 mJ/cm2. The absorption of the 248 nm radiation by the GaN at the interface induces rapid thermal decomposition of the interfacial layer, yielding metallic Ga and N2 gas. The substrate is easily removed by heating above the Ga melting point of 30 °C. Scanning electron microscopy and x-ray diffraction of the GaN films before and after lift-off demonstrate that the structural quality of the GaN films is not altered by the separation and transfer process.

Indium–gallium nitride (InxGa1−xN) single-quantum-well (SQW) light emitting diodes (LEDs), grown by metalorganic chemical vapor deposition on sapphire, were transferred onto Si substrates. The thin-film InxGa1−xN SQW LED structures were first bonded onto a n+-Si substrate using a transient-liquid-phase Pd–In wafer-bonding process followed by a laser lift-off technique to remove the sapphire growth substrate. Individual, 250×250 μm2, LEDs with a backside contact through the n+-Si substrate were then fabricated. The LEDs had a typical turn-on voltage of 2.5 V and a forward current of 100 mA at 5.4 V. The room-temperature emission peak for the InxGa1−xN SQW LEDs was centered at 455 nm with a full width at half maximum of 19 nm.

We have successfully grown ferromagnetic MnGa ultrathin films on GaAs substrates by molecular beam epitaxy. Reflection high energy electron diffraction and cross-sectional transmission electron microscopy show that monocrystalline MnGa films are grown with the c axis of the tetragonal unit cell normal to the (001) GaAs substrates. Both magnetization measurements by vibrating sample magnetometer and extraordinary Hall effect (EHE) measurements indicate perpendicular magnetization, with the remnant magnetization of 225 emu/cm3 and EHE resistivity in the range of 0.5–4 μΩ cm at room temperature. The material possesses properties ideal for certain nonvolatile magnetic memory coupled with underlying III-V circuitry.

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The technique of high resolution transmission electron microscopy (TEM) permits the first real space observations of the ordering of copper in the sulfur sublattices of chalcocite (Cu2S) and djurleite (Cu1.97 to 1.94S). Copper sulfide thin films formed by the ion exchange process in CdS single crystals are shown to be composed of small domains of the two phases (≈ 10 to 100 nm in diameter), separated by abrupt coherent interfaces. Strain calculations for these interfaces agree qualitatively with experimental observations. In addition, the chalcocite in the vicinity of chalcocite/djurleite interfaces is found to contain a high density of 1/4[010] faults. Structural considerations show that these faults are likely sites for copper vacancies.