Nanostructures

  1. Optical Properties of Nanostructures

(A) Linear and Nonlinear Optical Properties of Colloidal Semiconductor Nanocrystals

Semiconductor quantum dots have many behaviors like atoms and sometimes can be considered as “artificial atoms” since their emission wavelengths (or bandgaps) can be engineered and tuned in a broad range. We have studied linear and nonlinear optical properties of various colloidal semiconductor nanostructures (like quantum dots, quantum rods, and spherical quantum wells) synthesized by chemical techniques as well as interactions between them. We investigated the radiative lifetimes of various colloidal nanocrystals and studied how the radiative lifetimes of the nanocrystals can be altered and controlled by external environments, such as near a high-reflector, in a photonic crystal, and on a 2D-metal grating (interacting with plasmon polariton modes). Also, the external environment can change the optical emission properties of the nanocrystals, which can be used to design chemical gas sensors. We studied electronic structure transition from zero-dimensional quantum dots to one-dimensional quantum wires, and optical properties of spherical quantum wells with different thicknesses. Many other interesting optical properties have also been studied in the past few years.

  • “Fluorescence Lifetime of Mn-doped ZnSe Quantum Dots with Size Dependence”, C, Gan, Y. Zhang, and  Min Xiao (with D. Battaglia and X. Peng), Appl. Phys. Lett. , ,   92,  241111  (2008).
  • “Linear and Nonlinear Optical Refractions of CR-39 Composite with CdSe Nanocrystals”, C. Gan, Y. Zhang, S. Liu, and Min Xiao (with Yunjun Wang), Optical Materials, 30, 1440, 2008.
  • “Size Dependence of Nonlinear Optical Absorption and Refraction of Mn-doped ZnSe Nanocrystals”, C. Gan and Min Xiao  (with D. Battaglia, N. Pradhan, and X. Peng), Appl. Phys. Lett.,  91, 201103 (2007).
  • “Enhanced Dipole-Dipole Interactions of CdSe/CdS nanocrystal Quantum Dots inside a Planar Microcavity”, X. Wang, C.K. Shih, J. Xu, and Min Xiao, Appl. Phys. Lett., 89, 113114 (2006).
  • “Coupling between Semiconductor Quantum Dots and Two-Dimensional Surface Plasmons”, J. Zhang, Y.H. Ye, X. Wang, P. Rochon, and Min Xiao, Phys. Rev. B,  72  Rapid Communications, 201306(R) (2005).
  • “Lasing Action in Colloidal CdS/CdSe/CdS Quantum Wells”, J. Xu and Min Xiao, Appl. Phys. Lett., 87, 173117 (2005).
  • “Exciton Radiative Recombination in Spherical CdS/CdSe/CdS Quantum-Well Nanostructures”, J. Xu, D. Battaglia, X. Peng, and Min Xiao, Appl. Phys. Lett., 87, 043107 (2005).
  • “Photoluminescence from Colloidal CdS/CdSe/CdS Quantum Wells”,J. Xu, D. Battaglia, X. Peng, and Min Xiao, J. of Opt. Soc. Am. B   22, 1112 (2005).
  • “Suppression of Radiative Decay of CdTe Quantum Dots in Photonic Crystal with Pseudogap”, J. Zhang, X. Wang, Y. Ye, and Min Xiao, J. of Modern Optics, 51, 2493 (2004).
  • “Environmental Effects on the Photoluminescence of Highly Luminescent CdSe and CdSe/ZnS Core/Shell Nanocrystals in Polymer Thin Films”, A. Nazzal, X. Wang, L. Qu, W. Yu, Y. Wang, X. Peng, and Min Xiao, Journal of Physical Chemistry B  108, 5507 (2004).
  • “Photoluminescence Up-Conversion in Colloidal CdTe Quantum Dot”, X. Wang, W. Yu, J. Zhang, J. Aldana, X. Peng, and Min Xiao, Phys. Rev. B   68, 125318 (2003).
  • “Surface-Related Emission in Highly Luminescent CdSe Quantum Dots”, X. Wang, L. Qu, J. Zhang, X. Peng, and Min Xiao, Nano Letters, 3, 1103 (2003).
  • “Photo-Oxidation-Enhanced Coupling in Densely-Packed CdSe Quantum-Dot Films”, X. Wang, J. Zhang, A. Nazzal, and Min Xiao, Appl. Phys. Lett., 83, 162 (2003).
  • “Modified Spontaneous Emission of CdTe Quantum Dots inside Photonic Crysta”¡±, J.Y. Zhang, X.Y. Wang, Y.H. Ye, and Min Xiao, Opt. Lett.,  28,1430 (2003).
  • “Photo-Activated CdSe Nanocrystals as Nanosensors for Gases”, A.Y. Nazzal, L. Qu, X. Peng, and Min Xiao, Nano Letters, 3, 819 (2003).
  • “Electronic Structure Transformation from a Quantum-Dot to a Quantum-Wire System: Photoluminescence Decay and Polarization of Colloidal CdSe Quatum Rods”, X. Wang, J. Zhang, A. Nazzal, M. Darragh, and Min Xiao, Appl. Phys. Lett., 81, 4829 (2002).
  • “Lattice Contraction in Free-Standing CdSe Nanocrystals”, J. Zhang, X. Wang, and Min Xiao  (with L. Qu and X. Peng), Appl. Phys. Lett., 81, 2076 (2002).
  • “Modification of Spontaneous Emission from CdSe/CdS Quantum Dots in the Presence of a Semiconductor Interface”, J. Zhang, X. Wang, and Min Xiao, Opt. Lett., 27, 1253 (2002).

(B) Optical Properties of MBE-grown Semiconductor Nanostructures

Various semiconductor nanostructures have been grown by the MBE facility in the department. Carrier transfer and tunneling can occur between quantum dots in different layers and on the same layer through the wetting layer. Using optical polarization spectroscopy, we have studied the electronic transformations between low-dimensional nanostructures, i.e. from 0D quantum dots to 1D quantum wires, and from 1D quantum wires to 2D quantum wells. Otheer intersting coherent optical properties and interections between quantum dots have been studied.

  • “Resonance Fluorescence from a Coherently Driven Semiconductor Quantum Dot in a Cavity”, A. Muller, E.B. Flagg, P. Bianucci, X.Y. Wang, D.G. Deppe, W. Ma, J. Zhang, G.J. Salamo, Min Xiao, and C.K. Shih, Phys. Rev. Lett., 99, 187402 (2007).
  • “Growth of and Optical Emission from GaMnAs Thin Films Grown by Molecular Beam Epitaxy”, J. Xu, S. Liu, Min Xiao, and P.M. Thibado, J. Vac. Sci. Technol. B  25, 1467 (2007).
  • “Electrical and Optical Studies of GaMnAs/GaAs(001) Thin Films Grown by Molecular Beam Epitaxy”, J. Xu, S. Liu, Min Xiao, P.M. Thibado, J. of Crystal Growth, 301-302, p.101 (2007).
  • “Optical Switching in Arrays of Quantum Dots with Dipole-Dipole Interactions”, J. Gea-Banacloche, M. Mumba, and Min Xiao, Phys. Rev. B  74, 165330 (2006).
  • “Strong Optical Nonlinearity in Strain-Induced Laterally Ordered In0.4Ga0.6As Quantum Wires on GaAs (311)A Substrate”, Y.I. Mazur, Z. Wang, G.G. Tarasov, H. Wen, V. Strelchuk, D. Guzun, Min Xiao, G.J. Salamo, T.D. Mishima, G.D. Lian, and M.B. Johnson, J. Appl. Phys., 98, 053711 (2005).
  • “Photoluminescence Intermittency of InGaAs/GaAs Quantum Dots Confined in a Planar Microcavity”, X. Wang, W. Ma, J. Zhang, G.J. Salamo, Min Xiao, and C.K. Shih, Nano Letters,  5, 1873 (2005).
  • “Interdot Carrier Transfer in Asymmetric Bilayer InAs/GaAs Quantum Dot Structures”, Y.I. Mazur, Z. Wang, Min Xiao, G.J. Salamo, J.W. Tomm, V.Talalaev, T. Elsaesser, and H. Kissel, Appl. Phys. Lett., 86, 063102 (2005).
  • “Anisotropic Photoconductivity of InGaAs Quantum Dot Chains Measured by Terahertz Pulse Spectroscopy”, D. Cooke, F.A. Hegmann, Y. Mazur, W. Ma, X. Wang, Z. Wang, Min Xiao, G.J. Salamo, T. Mishima, and M. Johnson, Appl. Phys. Lett., 85, 3839 (2004).
  • “Polarization Spectroscopy of InGaAs/GaAs Quantum Wires Grown on (331)B GaAs Template with Nanoscale Fluctuations”, X. Wang, Z. Wang, V. Yazdanpanah, G.J. Salamo, and Min Xiao, J. of Appl. Phys., Communications, 95, 1609 (2004).
  • “Hidden Resonant Excitation of Photoluminescence in Bi-Layer Arrays of InAs/GaAs Quantum Dots”, Y. Mazur, Z.M. Wang, G.J. Salamo, and Min Xiao (with G.G. Tarasov, Z.Y. Zhuchenko, W.T. Masselink, and H. Kissel), Appl. Phys. Lett., 83, 1866 (2003).
  • “InGaAs/GaAs Three-Dimensionally-Ordered Array of Quantum Dots”, Y. Mazur, W. Ma, X. Wang, Z. Wang, G.J. Salamo, and Min Xiao (with T.D. Mishima and M.B. Johnson), Appl. Phys. Lett., 83, 987 (2003).
  • “Piezoelectric Effect in Elongated (In,Ga)As Islands on GaAs(100)”, W. Ma, X. Wang, M. Hussein, J. Shultz, Min Xiao, and G.J. Salamo, Phys. Rev. B  67, 035315 (2003).
  • “Photoluminescence Study of Carrier Transfer among Vertically-Aligned Double-Stacked InAs/GaAs Quantum Dot Layers”, Yu. I. Mazur, X. Wang, Z. Wang, G.J. Salamo, and Min Xiao (with H. Kissel), Appl. Phys. Lett., 81, 2469 (2002).

(C) Linear and Nonlinear Optical Properties of Ferroelectric Materials, Transition Metal Oxide Superlattices, and Other Novel Solid Materials & Structures

Using various techniques, we have investigated linear and nonlinear optical properties of some novel materials and structures, such as ferroelectric thin films, ZnO nano/micro rods, and transition metal oxide thin films/superlattices. We are developing new techniques to study electro-optical and magneto-optical properties of nevel multi-ferro materials.

  • “Atomic Control and Characterization of Surface Defect States of TiO 2 Terminated SrTiO3 Single Crystals”, M. Kareev,  S. Prosandeev,  J. Liu,  C. Gan,  A. Kareev,  J. W. Freeland, Min Xiao, and J. Chakhalian, Appl. Phys. Lett. , ,   to appear, 2008.
  • “Far-field Second-harmonic Fingerprint of Twinning in Single ZnO Rods”, S. Liu, H. Zhou, A. Ricca, R. Tian, and Min Xiao, Phys. Rev. B, 77, 113311, 2008.
  • “Reflective Second Harmonic Generation near Resonance in the Epitaxial Al-Doped ZnO Thin Film”, S. Liu, J.L. Weerasinghe, and Min Xiao (with J. Liu, J. Weaver, C.L. Chen, and W. Donner), Optics Express, 15, 10666 (2007).
  • “Domain Microstructures and Ferroelectric Phase Transition in Pb0.35Sr0.65TiO3 Films Studied by SHG in Reflection Geometry”, S.W. Liu, S. Jolly, and Min Xiao, (with C.L. Chen, J. Liu, Z. Yuan, W. Zhu), J. Appl. Phys., 101, 104118 (2007).
  • “Second Harmonic Generation and Ferroelectric Phase Transition in Thick and Ultra-thin Pb0.35Sr0.65TiO3 Films on (001) MgO Substrates”, S. Liu, J. Chakhalian, and Min Xiao (with C. Chen), Appl. Phys. Lett., 90, 042901 (2007).
  • “Nonlinear Optical Absorption and Refraction of Epitaxial Ba0.6TiO3 Thin Films on (001) MgO Substrates”, S. Liu, J. Xu, D. Guzun, G.J. Salamo, C.L. Chen, Y. Lin, and Min Xiao, Applied Physics B  82, 443 (2006).
  • “Optical Limiting and Enhanced Optical Nonlinearity in Boron-Doped Carbon Nanotubes”, J. Xu, Min Xiao, R. Czerw, and D.L. Carroll, Chemical Physics Letters, 389, 247 (2004).
  • “High-Efficiency Blue Light Generation by Frequency Doubling of Picosecond Pulses in a Thick KNbO3 Crystal”, Y. Li, D. Guzun, G. Salamo, and Min Xiao, J. Opt. Soc. Am. B 20, 1285 (2003).
  • “Compression and Broadening of Phase-Conjugate Pulses in Photorefractive Self-Pumped Phase Conjugators”, C. Yang, Min Xiao, and M. Kaczmarek, J. of Opt. Soc. Am. B  17, 1390 (2000).
  • “Pulse Evolution in a Photorefractive Self-Pumped Phase Conjugator with Transmission Grating Geometry”, C. Yang and Min Xiao, IEEE Journal of Quantum Electronics,  36, 698 (2000).
  • “Blue-Light Generation in Single-Pass Frequency Doubling of Femtosecond Pulses in KNbO3”, D. Guzun, Y. Li, and Min Xiao, Optics Communications, 180, 367 (2000).
  • “Observation of New Domain Structures in Fe:KNbO3 Crystals”, Z. Lu and Min Xiao, J. of Appl. Phys. 76, 4451 (1994).

(D) Optical Microscopy of Single Quantum Dots, Molecules, and Biological Cells

Using confocal optical microscopy, we investigate the optical properties of single nanostructures including PL, Raman, fluorescence intermittency, and interactions with external environments. Such studies can be very useful for fundamental understanding of semiconductor nanostructures such as (carrier diffusion in the colloidal nanocrystals, mechanism of fluorescence intermittency, et al) and for studying fundamental quantum optics (such as cavity-QED) and single-photon sources. Also, such investigations can lead to useful applications in biophysics and biomedical techniques. This is a renewed interest in our group and interesting research projects are underway in the laboratory.

  • “Controlling Fluorescence Intermittency of a Single Colloidal CdSe/Zns Quantum Dot in a Half-cavity”, Y. Zhang, V. K. Komarala, C. Rodriguez,   and Min Xiao, Phys. Rev. B, Rapid Communications  , accepted, (2008).
  • “Enhanced Fluorescence Intermittency in Mn-doped Single ZnSe quantum Dot”, Y. Zhang, C. Gan, J. Muhammad, D. Battaglia, X. Peng,   and Min Xiao, J. of Physical Chemistry  , accepted, (2008).
  • “Photoluminescence from Single CdSe Quantum Rods”, X. Chen, A. Nazzal, and Min Xiao (with Z. Peng, and X. Peng), J. of Luminescence, 97, 205 (2002).
  • “Polarization Spectroscopy of Single CdSe Quantum Rods”, X. Chen, A. Nazzal, D. Goorskey, and Min Xiao (with Z. Peng and X. Peng), Phys. Rev. B  64, 245304 (2001).