Adjunct Professor of Physics
Dr. Everitt is one of the Army's chief scientists. He works at the Army's Aviation and Missile RD&E Center at Redstone Arsenal, AL. Through his adjunct appointment in the Duke Physics Department, he leads an active experimental research group in condensed matter physics, nanophotonics, molecular physics, and novel terahertz imaging with colleagues on campus and through an international network of collaborators. Four principal research areas are being pursued:
1) Ultrafast Spectroscopy. This effort concentrates on the ultrafast spectroscopic characterization of wide bandgap semiconductor heterostructures and nanostructures. We use independently tunable pump and probe wavelengths that span the ultraviolet-visible-infrared regions from 200 nm to 12 microns with pulses shorter than 150 fs. The objective is to mapout and control carrier, exciton, and phonon transport and relaxation pathways in metal oxide and III-N semiconductors, sometimes doped with rare-earth atoms, using quantum efficiency, cw and time-resolved photoluminescence and differential transmission measurements. Areas of recent interest include characterization of efficient phosphorescence in sulfur-doped ZnO, carrier dynamics in III-N epilayers and multiple quantum wells, and characterization of radiative and nonradiative recombination of rare earth dopants in wide bandgap semiconductor hosts.
2) Ultraviolet Nanoplasmonics. Using metal nanoparticles to concentrate electromagnetic fields locally is an area of active research, most of which concentrates on using Au or Ag in the visible or near infrared spectral regions. Neither metal works in the ultraviolet, but there are significant advantages of extending plasmonics into the ultraviolet, including enhanced Raman cross sections, accelerated photo-degradation of toxins, and accelerated excitonic recombination. In partnership with Profs. April Brown (Duke ECE), Naomi Halas (Rice Univ.), Fernando Moreno (Univ. Cantabria), and others, we have been identifying and exploring new nanostructured metals including gallium and aluminum for ultraviolet plasmonics. We have recently demonstrated accelerated emission rates and surface enhanced Raman spectra in the ultraviolet.
3) Molecular Physics. The longest research effort involves the use of molecular rotational spectroscopy and time-resolved techniques to investigate molecular collision dynamics. These studies will help us develop more efficient terahertz sources, detect and identify clouds of trace gases, and understand nonequilibrium atmospheres and interstellar media. In collaboration with Prof. Frank De Lucia of Ohio State Univ., Dr. Everitt was the first to map out the complete rotational and vibrational energy transfer map of methyl fluoride, leading to the demonstration of a compact, tunable, coherent source of terahertz radiation for use in ground-based spectroscopy and astronomical observation. This double resonance technique has now been adapted as a new means for remotely identifying the constituents of a trace gas cloud at distances up to 1 km.
4) Terahertz Imaging. This newest activity uses powerful, cw, tunable millimeter- and submillimeter-wave sources to adapt various coherent imaging techniques to the terahertz spectral region. Interferometry, digital holography, tomography, synthetic aperture RADAR, ISAR, ellipsometry, and polarimetry are all explored to develop practical tools for non-destructive measurements of visually opaque materials. The lab contains a unique combination of tunable sources, Schottky diode detectors, heterodyne receivers, and bolometers, plus a one-of-a-kind THz beam characterization and imaging instrument. The lab also explores ways of optimizing and accelerating these slow imaging methodologies using digital reconstruction and compressive sampling techniques pioneered by on-campus collaborator Prof. David Brady and novel beam forming metamaterials with Prof. David Smith.
Mrozack, Alex, et al. “Adaptive millimeter-wave synthetic aperture imaging for compressive sampling of sparse scenes.” Optics Express, vol. 22, no. 11, June 2014, pp. 13515–30. Epmc, doi:10.1364/oe.22.013515. Full Text Open Access Copy
Roberts, Adam T., et al. “Optical characterization of electron-phonon interactions at the saddle point in graphene.” Physical Review Letters, vol. 112, no. 18, May 2014, p. 187401. Epmc, doi:10.1103/physrevlett.112.187401. Full Text Open Access Copy
Sanz, J. M., et al. “Metals for UV plasmonics.” Optics Infobase Conference Papers, Jan. 2014.
Akyildiz, H. I., et al. “Formation of novel photoluminescent hybrid materials by sequential vapor infiltration into polyethylene terephthalate fibers.” Journal of Materials Research, vol. 29, no. 23, Jan. 2014, pp. 2817–26. Scopus, doi:10.1557/jmr.2014.333. Full Text
Mohanta, A., et al. “Effect of pressure and Al doping on structural and optical properties of ZnO nanowires synthesized by chemical vapor deposition.” Journal of Luminescence, vol. 146, Jan. 2014, pp. 470–74. Scopus, doi:10.1016/j.jlumin.2013.10.028. Full Text Open Access Copy
Avrutin, V., et al. “Saga of efficiency degradation at high injection in InGaN light emitting diodes.” Turkish Journal of Physics, vol. 38, no. 3, Jan. 2014, pp. 269–313. Scopus, doi:10.3906/fiz-1407-23. Full Text
Simmons, J. G., et al. “The dependence of ZnO photoluminescence efficiency on excitation conditions and defect densities.” Applied Physics Letters, vol. 103, no. 20, Nov. 2013. Scopus, doi:10.1063/1.4829745. Full Text
Roberts, A. T., et al. “Spectroscopic investigation of coupling among asymmetric InGaN/GaN multiple quantum wells grown on non-polar a-plane GaN substrates.” Applied Physics Letters, vol. 103, no. 18, Oct. 2013. Scopus, doi:10.1063/1.4827536. Full Text Open Access Copy
Sanz, J. M., et al. “UV plasmonic behavior of various metal nanoparticles in the near- and far-field regimes: Geometry and substrate effects.” Journal of Physical Chemistry C, vol. 117, no. 38, Sept. 2013, pp. 19606–15. Scopus, doi:10.1021/jp405773p. Full Text
Avrutin, V., et al. “Morphology and optical properties of ZnO nanorods grown by catalyst-assisted vapor transport on various substrates.” Materials Research Society Symposium Proceedings, vol. 963, 2006, pp. 153–58.
Xie, J., et al. “Characterization of GaN epitaxial films grown on SiN x and TiN x porous network templates.” Proceedings of Spie the International Society for Optical Engineering, vol. 6121, 2006. Scopus, doi:10.1117/12.646858. Full Text
Özgür, U., et al. “Thermal conductivity of bulk ZnO after different thermal treatments.” Journal of Electronic Materials, vol. 35, no. 4, 2006, pp. 550–55. Scopus, doi:10.1007/s11664-006-0098-9. Full Text
Özgür, U., et al. “Improved structural quality and carrier decay times in GaN epitaxy on SiN and TiN porous network templates.” Materials Science Forum, vol. 527–529, no. PART 2, 2006, pp. 1505–08. Scopus, doi:10.4028/0-87849-425-1.1505. Full Text
Munasinghe, C., et al. “GaN:Eu interrupted growth epitaxy (IGE): Thin film growth and electroluminescent devices.” Materials Research Society Symposium Proceedings, vol. 866, 2005, pp. 41–52.
Muth, J., et al. “Optical properties of II-IV-N2 semiconductors.” Materials Research Society Symposium Proceedings, vol. 831, 2005, pp. 745–49.
Peng, H. Y., et al. “Relaxation dynamics in rare earth-doped GaN.” Optics Infobase Conference Papers, 2005.
Foreman, J. V., et al. “Bright, eye-matched visible emission from ZnO nanowires.” Optics Infobase Conference Papers, 2005. Scopus, doi:10.1364/fio.2005.ftuf4. Full Text
Özgür, U., et al. “Ultrafast carrier relaxation in group III-nitride multiple quantum wells.” Proceedings of Spie the International Society for Optical Engineering, vol. 5352, 2004, pp. 158–68. Scopus, doi:10.1117/12.529426. Full Text
Neogi, A., et al. “Effects of strain on carrier recombination in GaN quantum dots.” Conference on Quantum Electronics and Laser Science (Qels) Technical Digest Series, vol. 89, 2003.