Luminescence mechanisms of defective ZnO nanoparticles.

ZnO nanoparticles (NPs) synthesized by pulsed laser ablation (PLAL) of a zinc plate in deionized water were investigated by time-resolved photoluminescence (PL) and complementary techniques (TEM, AFM, μRaman). HRTEM images show that PLAL produces crystalline ZnO NPs in wurtzite structure with a slightly distorted lattice parameter a. Consistently, optical spectra show the typical absorption edge of wurtzite ZnO (Eg = 3.38 eV) and the related excitonic PL peaked at 3.32 eV with a subnanosecond lifetime. ZnO NPs display a further PL peaking at 2.2 eV related to defects, which shows a power law decay kinetics. Thermal annealing in O2 and in a He atmosphere produces a reduction of the A1(LO) Raman mode at 565 cm(-1) associated with oxygen vacancies, accompanied by a decrease of defect-related emission at 2.2 eV. Based on our experimental results the emission at 2.2 eV is proposed to originate from a photo-generated hole in the valence band recombining with an electron deeply trapped in a singly ionized oxygen vacancy. This investigation clarifies important aspects of the photophysics of ZnO NPs and indicates that ZnO emission can be controlled by thermal annealing, which is important in view of optoelectronic applications.

[1]  H. Zeng,et al.  An insight into defect relaxation in metastable ZnO reflected by a unique luminescence and Raman evolutions. , 2015, Physical chemistry chemical physics : PCCP.

[2]  M. Cannas,et al.  Oxidation of Zn nanoparticles probed by online optical spectroscopy during nanosecond pulsed laser ablation of a Zn plate in H 2 O , 2015 .

[3]  H. Xiong,et al.  Photoluminescent ZnO Nanoparticles and Their Biological Applications , 2015, Materials.

[4]  Haibo Zeng,et al.  A general one-pot strategy for the synthesis of high-performance transparent-conducting-oxide nanocrystal inks for all-solution-processed devices. , 2014, Angewandte Chemie.

[5]  T. Uchino,et al.  Variations in Decay Rate of Green Photoluminescence in ZnO under Above- and Below-Band-Gap Excitation , 2014 .

[6]  M. Villani,et al.  Zn vacancy induced green luminescence on non-polar surfaces in ZnO nanostructures , 2014, Scientific Reports.

[7]  Davoud Dorranian,et al.  Effect of laser pulse energy and wavelength on the structure, morphology and optical properties of ZnO nanoparticles , 2014 .

[8]  M. Cannas,et al.  Luminescent silicon nanocrystals produced by near-infrared nanosecond pulsed laser ablation in water , 2014 .

[9]  H. Zeng,et al.  Controlling oxygen vacancies and properties of ZnO , 2014 .

[10]  V. Sigaev,et al.  Light-emitting Ga-oxide nanocrystals in glass: a new paradigm for low-cost and robust UV-to-visible solar-blind converters and UV emitters. , 2014, Nanoscale.

[11]  M. Kawasaki,et al.  Challenges and opportunities of ZnO-related single crystalline heterostructures , 2013, 1311.5088.

[12]  G. Mondio,et al.  ZnO nanostructures produced by laser ablation in water: Optical and structural properties , 2013 .

[13]  G. Xing,et al.  Origin of green emission and charge trapping dynamics in ZnO nanowires , 2013 .

[14]  P. Holtz,et al.  Surface related and intrinsic exciton recombination dynamics in ZnO nanoparticles synthesized by a sol-gel method , 2013 .

[15]  D. Chrisey,et al.  Pulsed laser ablation in liquid for micro-/nanostructure generation , 2012 .

[16]  T. Uchino,et al.  Thermally activated below-band-gap excitation behind green photoluminescence in ZnO , 2012 .

[17]  Alberto Diaspro,et al.  Luminescent silicon nanoparticles prepared by ultra short pulsed laser ablation in liquid for imaging applications , 2012 .

[18]  Shikuan Yang,et al.  Nanomaterials via Laser Ablation/Irradiation in Liquid: A Review , 2012 .

[19]  G. Schütz,et al.  Amorphous interlayers between crystalline grains in ferromagnetic ZnO films , 2012 .

[20]  Aleksandra B. Djurišić,et al.  ZnO nanostructures: growth, properties and applications , 2012 .

[21]  T. Okuno,et al.  Fabrication of ZnO nanoparticles by laser ablation of sintered ZnO in aqueous solution , 2012 .

[22]  J. Song,et al.  Formation of ZnO nanoparticles by laser ablation in neat water , 2011 .

[23]  R. Ismail,et al.  Preparation and characterization of colloidal ZnO nanoparticles using nanosecond laser ablation in water , 2011 .

[24]  P. Shen,et al.  ZnO and ε-Zn(OH)2 Composite Nanoparticles by Pulsed Laser Ablation on Zn in Water , 2011 .

[25]  A. Ng,et al.  ZnO nanostructures for optoelectronics: Material properties and device applications , 2010 .

[26]  Dong Xiang,et al.  Origin of Visible Photoluminescence of ZnO Quantum Dots: Defect-Dependent and Size-Dependent , 2010 .

[27]  Shikuan Yang,et al.  Blue Luminescence of ZnO Nanoparticles Based on Non‐Equilibrium Processes: Defect Origins and Emission Controls , 2010 .

[28]  Anderson Janotti,et al.  Fundamentals of zinc oxide as a semiconductor , 2009 .

[29]  S. Jokela,et al.  Defects in ZnO , 2009 .

[30]  Dong Chan Kim,et al.  Comparative luminescence properties of ZnO nanorods grown on various substrates by low-temperature metalorganic chemical vapour deposition , 2008 .

[31]  Ram Gopal,et al.  Synthesis of colloidal zinc oxide nanoparticles by pulsed laser ablation in aqueous media , 2008 .

[32]  M. Jayaraj,et al.  Luminescence from Surfactant-Free ZnO Quantum Dots Prepared by Laser Ablation in Liquid , 2008 .

[33]  Dilip K. Singh,et al.  Correlation between microstructure and optical properties of ZnO nanoparticles synthesized by ball milling , 2007 .

[34]  R. K. Thareja,et al.  Synthesis and characterization of zinc oxide nanoparticles by laser ablation of zinc in liquid , 2007 .

[35]  Li Yang,et al.  Growth of self-assembled ZnO nanoleaf from aqueous solution by pulsed laser ablation , 2007 .

[36]  L. Schmidt‐Mende,et al.  ZnO - nanostructures, defects, and devices , 2007 .

[37]  C. Klingshirn.  ZnO: material, physics and applications. , 2007, Chemphyschem : a European journal of chemical physics and physical chemistry.

[38]  Yoshiki Shimizu,et al.  Preparation of metal oxide-based nanomaterials using nanosecond pulsed laser ablation in liquids , 2006 .

[39]  A. Uedono,et al.  Improvements in quantum efficiency of excitonic emissions in ZnO epilayers by the elimination of point defects , 2006 .

[40]  David J. Huntley,et al.  An explanation of the power-law decay of luminescence , 2006 .

[41]  Baoping Zhang,et al.  Temperature-dependent exciton dynamics in a ZnO thin film , 2005 .

[42]  W. K. Chan,et al.  Time-resolved photoluminescence from ZnO nanostructures , 2005 .

[43]  Magnus Willander,et al.  Deep-level emissions influenced by O and Zn implantations in ZnO , 2005 .

[44]  H. Zeng,et al.  Composition/structural evolution and optical properties of ZnO/Zn nanoparticles by laser ablation in liquid media. , 2005, The journal of physical chemistry. B.

[45]  H. Morkoç,et al.  A COMPREHENSIVE REVIEW OF ZNO MATERIALS AND DEVICES , 2005 .

[46]  Alexander A. Balandin,et al.  Micro-Raman investigation of optical phonons in ZnO nanocrystals , 2005 .

[47]  A. Uedono,et al.  Direct comparison of photoluminescence lifetime and defect densities in ZnO epilayers studied by time-resolved photoluminescence and slow positron annihilation techniques , 2004 .

[48]  S. Nie,et al.  In vivo cancer targeting and imaging with semiconductor quantum dots , 2004, Nature Biotechnology.

[49]  N. Koshizaki,et al.  Synthesis of Ultrafine SnO2-x Nanocrystals by Pulsed Laser-Induced Reactive Quenching in Liquid Medium , 2003 .

[50]  Yoshihiro Takeda,et al.  Formation of Stable Platinum Nanoparticles by Laser Ablation in Water , 2003 .

[51]  Bixia Lin,et al.  Green luminescent center in undoped zinc oxide films deposited on silicon substrates , 2001 .

[52]  T. Kondow,et al.  Structure and Stability of Silver Nanoparticles in Aqueous Solution Produced by Laser Ablation , 2000 .

[53]  G. Ceder,et al.  First-principles study of native point defects in ZnO , 2000 .

[54]  Andries Meijerink,et al.  The luminescence of nanocrystalline ZnO particles: the mechanism of the ultraviolet and visible emission , 2000 .

[55]  Masayuki Watanabe,et al.  Time-resolved study of photoluminescence in anatase TiO2 , 2000 .

[56]  Andries Meijerink,et al.  The Kinetics of the Radiative and Nonradiative Processes in Nanocrystalline ZnO Particles upon Photoexcitation , 2000 .

[57]  K. Kihara,et al.  ANHARMONIC THERMAL VIBRATIONS IN Zno , 1985 .

[58]  R. Callender,et al.  Dispersion of Raman Cross Section in CdS and ZnO over a Wide Energy Range , 1973 .

[59]  R. Grigorovici,et al.  Optical Properties and Electronic Structure of Amorphous Germanium , 1966, 1966.

[60]  D. G. Thomas,et al.  Kinetics of Radiative Recombination at Randomly Distributed Donors and Acceptors , 1965 .

[61]  J. Song,et al.  Characterization of ZnO Nanoparticles Grown by Laser Ablation of a Zn Target in Neat Water , 2009 .

[62]  Z. Q. Chen,et al.  Production and recovery of defects in phosphorus-implanted ZnO , 2005 .