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Han Htoon

Phone: 505-665-5444
Email: htoon@lanl.gov

Appointments

• Nov. 2005 - present: Technical Staff Member, Los Alamos National Laboratory
• Dec. 2001-Nov. 2005: Director’s Postdoctoral Fellow, Los Alamos National Lab

Education

• Dec. 2001: PhD, Physics, The University of Texas at Austin
• May 1996: MS, Physics, Western Illinois University, Macomb, IL
• Dec. 1991: BS, Physics (Honors), University of Yangon, Myanmar

Research Interests

• Fundamental photo-physics of semiconductor nanostructures (semiconductor nanocrystals, nanowires, carbon nanotubes, etc.) and metal-semiconductor hybrid nanostructures. Understanding the effects of dimensionality on electronic structures, the competition between radiative and non-radiative electron-hole recombination processes, and plasmon-exciton interactions. Development of novel low temperature single nanostructure optical spectroscopy and imaging techniques. Integration of nanowires and nanocrystals into light emitting diodes as well as photo-voltaic devices.

Recent Research Accomplishments

• Magneto PL study of individual CdSe NCs that reveals different spin states of band-edge excitons.
• The first low temperature photoluminescence (PL) studies of individual single walled carbon nanotubes and observation of Fermi-edge singularity
• The first low temperature, single nanotube PL excitation studies revealing surprisingly dominant roles of phonons-assisted processes in optical absorption.
• Development of a novel, single NC PL excitation (PLE) spectroscopy technique that could account for the PL intermittency behaviors of single NCs and acquisition of the first low T PLE spectra of individual CdSe NCs.
• Discovery of exciton-exciton annihilation process in CdSe nano-rods and use of this effect to improve optical gain performance of proto-type nanorod lasers
• Direct observation of exciton Rabi oscillation in InGaAs self assembled quantum dots.
• I am one of the lead scientists for the Nano-opitc laboratory of the DoE Center Integrated Nanotechnology (CINT) jointly operated by LANL and Sandia National Laboratories. Our nano-optic laboratory houses one-of-a-kind low temperature, scanning probe (AFM/NSOM) facility and state-of-the-art photo-detectors, lasers and other advanced spectroscopy instrumentations.

Awards

• LANL Associate Directorate for Chemistry, Life, and Earth Sciences Achievement Award for Program Development (2009)
• Postdoctoral Distinguish Performance Award, Los Alamos National Laboratory (2005)
• Achievement Award, Los Alamos National Laboratory (2003)
• Director’s Postdoctoral Fellowship, Los Alamos National Laboratory (2001)
• Outstanding Poster Award, MRS 1999 Fall Meeting
• Best Graduate Student Award (1996), Department of Physics, Western Illinois University

Selected Publications

• Htoon, H., Crooker, S. A., Furis, M., Jeong, S., Efros, A. L. & Klimov, V. I. Anomalous Circular Polarization of Photoluminescence Spectra of Individual CdSe Nanocrystals in an Applied Magnetic Field. Phys. Rev. Lett. 102, 017402 (017404 pp.), (2009).
• Glennon, J. J., Tang, R., Buhro, W. E., Loomis, R. A., Bussian, D. A., Htoon, H. & Klimov, V. I. Exciton localization and migration in individual CdSe quantum wires at low temperatures. Phys. Rev. B 80, 081303 (081304 pp.), (2009).
• Srivastava, A., Htoon, H., Klimov, V. I. & Kono, J. Direct observation of dark excitons in individual carbon nanotubes: inhomogeneity in the exchange splitting. Phys. Rev. Lett. 101, 087402-087401-087404, (2008).
• Htoon, H., Furis, M., Crooker, S. A., Jeong, S. & Klimov, V. I. Linearly polarized “fine structure” of the bright exciton state in individual CdSe nanocrystal quantum dots. Phys. Rev. B 77, 035328-035321-035327, (2008).
• Chen, Y., Vela, J., Htoon, H., Casson, J. L., Werder, D. J., Bussian, D. A., Klimov, V. I. & Hollingsworth, J. A. "Giant" multishell CdSe nanocrystal quantum dots with suppressed blinking. J. Am. Chem. Soc. 130, 5026-+, (2008).
• Furis, M., Htoon, H., Petruska, M. A., Klimov, V. I., Barrick, T. & Crooker, S. A. Bright-exciton fine structure and anisotropic exchange in CdSe nanocrystal quantum dots. Phys. Rev. B 73, 241313-241311-241314, (2006).
• Htoon, H., O'Connell, M. J., Doorn, S. K. & Klimov, V. I. Single carbon nanotubes probed by photoluminescence excitation spectroscopy: the role of phonon-assisted transitions. Phys. Rev. Lett. 94, 127403/127401-127404, (2005).
• Htoon, H., O'Connell, M. J., Cox, P. J., Doorn, S. K. & Klimov, V. I. Low temperature emission spectra of individual single-walled carbon nanotubes: Multiplicity of subspecies within single-species nanotube ensembles. Phys. Rev. Lett. 93, 027401-027401-027401-027404, (2004).
• Htoon, H., Cox, P. J. & Klimov, V. I. Structure of excited-State transitions of individual semiconductor nanocrystals probed by photoluminescence excitation spectroscopy. Phys. Rev. Lett. 93, 187402/187401-187404, (2004).
• Htoon, H., Hollingsworth, J. A., Dickerson, R. & Klimov, V. I. Effect of zero- to one-dimensional transformation on multiparticle Auger recombination in semiconductor quantum rods. Phys. Rev. Lett. 91, 227401/227401-227404, (2003).

August 2010