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Kolloidale Nanosysteme aus magnetischen und metallischen Materialien : Synthese und CharakterisierungSobal, Neli January 2003 (has links)
Ein Spezialgebiet der modernen Mikroelektronik ist die Miniaturisierung und Entwicklung von neuen nanostrukturierten und Komposit-Materialen aus 3d-Metallen. Durch geeignete Zusammensetzungen können diese sowohl mit einer hohen Sättigungsmagnetisierung und Koerzitivfeldstärke als mit besserer Oxidationsbeständigkeit im Vergleich zu den reinen Elementen erzielt werden.<br />
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In der vorliegenden Arbeit werden neue Methoden für die Herstellung von bimetallischen kolloidalen Nanopartikeln vor allem mit einer Kern-Hülle-Struktur (Kern@Hülle) präsentiert. Bei der überwiegenden Zahl der vorgestellten Reaktionen handelt es sich um die thermische Zersetzung von metallorganischen Verbindungen wie Kobaltcarbonyl, Palladium- und Platinacetylacetonate oder die chemische Reduktion von Metallsalze mit langkettigem Alkohol in organischem Lösungsmittel. Daneben sind auch Kombinationen aus diesen beiden Verfahren beschrieben. Es wurden Kolloide aus einem reinen Edelmetall (Pt, Pd, Ag) in einem organischen Lösungsmittel synthetisiert und daraus neue, bisher in dieser Form nicht bekannte Ag@Co-, Pt@Co-, Pd@Co- und Pt@Pd@Co-Nanopartikel gewonnen.<br />
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Der Kobaltgehalt der Ag@Co-, Teilchen konnte im Bereich von 5 bis 73 At. % beliebig eingestellt werden. Der mittlere Durchmesser der Ag@Co-Partikel wurde von 5 nm bis 15 nm variiert. Bei der Herstellung von Pt@Co-Teilchen wurde eine unterschiedlich dicke Kobalt-Hülle von ca. 1,0 bis 2,5 nm erzielt. Im Fall des Palladiums wurden sowohl monodispere als auch polydisperse Pd-Nanopartikel mit einer maximal 1,7-2,0nm dicken Kobalthülle synthetisiert.<br />
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Ein großer Teil dieser Arbeit befasst sich mit den magnetischen Eigenschaften der kolloidalen Teilchen, wobei die SQUID-Magnetometrie und Röntgenzirkulardichroismus (XMCD) dafür eingesetzt wurden. Weil magnetische Messungen alleine nur indirekte Schlüsse über die untersuchten Systeme erlauben, wurde dabei besonderer Wert auf die möglichst genaue strukturelle Charakterisierung der Proben mittels moderner Untersuchungsmethoden gelegt. Röntgendiffraktometrie (XRD), Röntgenabsorptionsfeinstruktur- (EXAFS) und UV-Vis-Spektroskopie sowie Transmissionselektronenmikroskopie (TEM) in Kombination mit Elektronen Energieverlustspektroskopie (EELS) und energiedispersive Röntgenfluoreszensanalyse (EDX) wurden verwendet. / Magnetic colloidal particles are attractive because of their possible application to ultra-high-density magnetic data storage media, sensors, electronic devices and medical diagnostics. The properties of small particles depend on their composition, shape, and method of preparation. The combination of 3d-metals (Fe, Co, Ni) with noble metals improves the stability of the colloids and leads to new properties of the magnetic systems, often distinct from those of the corresponding monometallic particles. Core-shell particles, where dia- or paramagnetic noble metal-cores are surrounded by a ferromagnetic Co-shell, are an interesting system to study surface and interfacial magnetism such as an induced polarization or a giant magnetoresistance effect. <br />
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In this work, new synthetic routes for the preparation of monometallic (Pt, Pd, Ag) and bimetallic magnetic nanocrystals (Ag@Co, Pt@Co, Pd@Co) with core-shell structure are presented. Stable colloids with a narrow particle size distribution were obtained in organic solvents using methods of wet chemistry. The method of preparation of Ag@Co is based on the thermal decomposition of dicobalt octycarbonyl in combination with a transmetalation reaction with water free AgClO4. The cobalt amount in the Ag@Co system could be tuned from 5 to 73 at. %. The average diameter of the particles was varied from 5 to 15 nm. <br />
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The reduction of platinum and palladium salts in organic solution using long chained alcohol as the reductant leads to stable metal nanostructures. Monodisperse Pd and Pt particles with average sizes of 1.7 to 7.0 nm were synthesized via thermal decomposition of metal-surfactant complexes too. Alkylamines and alkylphosphines were used in this procedure. The thickness of the Co-shell was controlled by a simple high-temperature thermolysis of dicobalt octacarbonyl at the presence of Pd and Pt seeds and was tunable from 0.5 to 2.5 nm. <br />
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The crystalline structure of the samples was characterized by transmission electron microscopy (TEM), energy dispersive x-ray spectroscopy (EDX), UV-VIS and electron-energy loss spectroscopy (EELS). SQUID magnetometry, x-ray magnetic circular dichroism (XMCD) and extended x-ray absorption fine structure (EXAFS) measurements gave information about the magnetic properties of the bimetallic systems and revealed their dependency on the particle size and the chemical composition. A high spin to orbital moments ratio µL/µS of 0.26±0.06 for Ag@Co and 0.22±0.05 for Pt@Co nanocrystals was observed at XMCD measurements due to the lowered dimensionality the investigated systems.
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ALD of Copper and Copper Oxide Thin Films For Applications in Metallization Systems of ULSI DevicesWaechtler, Thomas, Oswald, Steffen, Roth, Nina, Lang, Heinrich, Schulz, Stefan E., Gessner, Thomas 15 July 2008 (has links) (PDF)
<p>
As a possible alternative for growing seed layers
required for electrochemical Cu deposition of
metallization systems in ULSI circuits,
the atomic layer deposition (ALD) of Cu is
under consideration. To avoid drawbacks related
to plasma-enhanced ALD (PEALD), thermal growth
of Cu has been proposed by two-step processes
forming copper oxide films by ALD which are
subsequently reduced.
</p>
<p>
This talk, given at the 8th International
Conference on Atomic Layer Deposition
(ALD 2008), held in Bruges, Belgium from
29 June to 2 July 2008, summarizes the results
of thermal ALD experiments from
[(<sup><i>n</i></sup>Bu<sub>3</sub>P)<sub>2</sub>Cu(acac)]
precursor and wet O<sub>2</sub>. The precursor is of particular
interest as it is a liquid at room temperature
and thus easier to handle than frequently
utilized solids such as Cu(acac)<sub>2</sub>,
Cu(hfac)<sub>2</sub> or
Cu(thd)<sub>2</sub>. Furthermore the substance is
non-fluorinated, which helps avoiding a major
source of adhesion issues repeatedly observed
in Cu CVD.
</p>
<p>
As result of the ALD experiments, we obtained composites of metallic and
oxidized Cu on Ta
and TaN, which was determined by
angle-resolved XPS analyses. While smooth,
adherent films were grown on TaN in an ALD
window up to about 130°C, cluster-formation due to
self-decomposition of the precursor was observed
on Ta. We also recognized a considerable
dependency of the growth on the degree of
nitridation of the TaN. In contrast, smooth
films could be grown up to 130°C on SiO<sub>2</sub>
and Ru, although in the latter case the ALD window
only extends to about 120°C. To apply the ALD
films as seed layers in subsequent electroplating
processes, several reduction processes are
under investigation. Thermal and plasma-assisted
hydrogen treatments are studied, as well as
thermal treatments in vapors of isopropanol,
formic acid, and aldehydes. So far these
attempts were most promising using formic
acid at temperatures between 100 and 120°C,
also offering the benefit of avoiding
agglomeration of the very thin ALD films on
Ta and TaN. In this respect, the process
sequence shows potential for depositing
ultra-thin, smooth Cu films at temperatures
below 150°C.
</p>
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ALD of Copper and Copper Oxide Thin Films For Applications in Metallization Systems of ULSI DevicesWaechtler, Thomas, Oswald, Steffen, Roth, Nina, Lang, Heinrich, Schulz, Stefan E., Gessner, Thomas 15 July 2008 (has links)
As a possible alternative for growing seed layers required for electrochemical Cu deposition of metallization systems in ULSI circuits, the atomic layer deposition (ALD) of Cu is under consideration. To avoid drawbacks related to plasma-enhanced ALD (PEALD), thermal growth of Cu has been proposed by two-step processes forming copper oxide films by ALD which are subsequently reduced.
This talk, given at the 8th International Conference on Atomic Layer Deposition (ALD 2008), held in Bruges, Belgium from 29 June to 2 July 2008, summarizes the results of thermal ALD experiments from [(<sup><i>n</i></sup>Bu<sub>3</sub>P)<sub>2</sub>Cu(acac)] precursor and wet O<sub>2</sub>. The precursor is of particular
interest as it is a liquid at room temperature and thus easier to handle than frequently utilized solids such as Cu(acac)<sub>2</sub>,
Cu(hfac)<sub>2</sub> or Cu(thd)<sub>2</sub>. Furthermore the substance is non-fluorinated, which helps avoiding a major source of adhesion issues repeatedly observed in Cu CVD.
As result of the ALD experiments, we obtained composites of metallic and oxidized Cu on Ta and TaN, which was determined by angle-resolved XPS analyses. While smooth, adherent films were grown on TaN in an ALD window up to about 130°C, cluster-formation due to self-decomposition of the precursor was observed on Ta. We also recognized a considerable dependency of the growth on the degree of nitridation of the TaN. In contrast, smooth films could be grown up to 130°C on SiO<sub>2</sub>and Ru, although in the latter case the ALD window only extends to about 120°C. To apply the ALD films as seed layers in subsequent electroplating processes, several reduction processes are
under investigation. Thermal and plasma-assisted hydrogen treatments are studied, as well as thermal treatments in vapors of isopropanol, formic acid, and aldehydes. So far these attempts were most promising using formic acid at temperatures between 100 and 120°C, also offering the benefit of avoiding agglomeration of the very thin ALD films on
Ta and TaN. In this respect, the process sequence shows potential for depositing ultra-thin, smooth Cu films at temperatures below 150°C.
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