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Size-Distribution and Emission Spectroscopy of W Nanoparticles Generated byLaser-Assisted CVD for Different WF6/H2/Ar Mixtures
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science, Materials Physics.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
2003 (English)In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 107, no 42, 11615-11621 p.Article in journal (Refereed) Published
Abstract [en]

Tungsten nanoparticles were produced by ArF excimer laser-assisted chemical vapor deposition fromWF6/H2/Ar gas mixtures. Subsequent pulses excited the gas-phase particles, allowing optical emissionspectroscopy to monitor the intensity of the emitted radiation and temperature of the laser-heated particles.A systematic study on size-distributions of the deposited particles, determined by electron microscopy, inconnection with emission spectroscopy and rate of deposition measurements is presented, with respect todifferent partial pressures of the reactants. The rates of deposition of W nanoparticle films were determinedby X-ray fluorescence spectroscopy. In addition, the intensity of the scattered 193 nm laser line was alsomonitored as the partial pressure of H2 was varied.

Place, publisher, year, edition, pages
2003. Vol. 107, no 42, 11615-11621 p.
National Category
Engineering and Technology Natural Sciences
URN: urn:nbn:se:uu:diva-90506DOI: 10.1021/jp0343077OAI: oai:DiVA.org:uu-90506DiVA: diva2:162881
Available from: 2003-05-13 Created: 2003-05-13 Last updated: 2013-07-10Bibliographically approved
In thesis
1. Formation of nanoparticles by laser-activated processes
Open this publication in new window or tab >>Formation of nanoparticles by laser-activated processes
2003 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Due to the small dimensions, nanoparticles and materials consisting of nano-sized building blocks exhibit unique — mostly superior — properties, well differing from their bulk counterpart. Most of the novel properties of nanoparticles (and nanomaterials) are size-dependent, while the majority of the common gasphase methods used for generation of nanopowders result in different, usually wide, size-dispersions. Further understanding of the fundamental processes leading to particle formation is therefore required, leading to better control of size and distribution of the nanoparticles, thus allowing engineering of the desired properties for both nanoparticles and nanomaterials.

In this present thesis, nanoparticles were produced by two different gasphase techniques activated by lasers, namely laser chemical vapor deposition (LCVD) and pulsed laser ablation (PLA). Optical emission spectroscopy (OES) was performed on thermal (blackbody-like) radiation originating from laser-excited particles during LCVD and coupled to measured size-distributions. In-situ monitoring of size-distributions by a differential mobility analyzer (DMA) was employed during PLA. In addition, deposited nanoparticles were characterized by a variety of standard techniques.

Different cooling mechanisms of the laser-excited gasphase particles were identified based on temperature and emitted intensity data extracted from OES measurements. The strong evaporation at elevated temperatures also allowed direct size manipulation of the particles. By monitoring the intensity of the emitted thermal radiation and the scattered laser line, strong indications about the so called coagulation limit, where a broadening of the size-distribution occurred, was obtained. The DMA monitoring, supported by modeling, gave information about different mechanisms (thermal and photochemical) of the ablation process, and particle condensation well below the ablation threshold was also found.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2003. 66 p.
Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1104-232X ; 855
Inorganic chemistry, nanoparticles, laser-assisted CVD, laser ablation, emission spectroscopy, size-distribution, Oorganisk kemi
National Category
Inorganic Chemistry
Research subject
Inorganic Chemistry
urn:nbn:se:uu:diva-3454 (URN)91-554-5664-2 (ISBN)
Public defence
2003-06-03, Häggsalen, The Ångström Laboratory, Uppsala, 10:15
Available from: 2003-05-13 Created: 2003-05-13Bibliographically approved

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