Metal organic precursors

Sol-gel primers use inorganic or metal-organic precursors (generally aluminum, silicon or titanium alkoxides) whose chemistry is closely related to the silane coupling agents discussed previously. These precursors are dissolved in alcohol, then hydrolyzed by the addition of water ... 

Even acetophenone reacts with the magnesium compound 17 (R1 = R2 = H) to yield the w-diastereomer 18 with 90 % de 22 24. The structure of the metal-organic precursor and, as well, of the major product was determined by an X-ray crystal structure analysis23. 

The reactive crystallization has some peculiar characteristics like insoluble product, initiation of reaction by change in pH and conductivity. In this case the solution becomes saturated and eventually supersaturated with respect to reactant nucleation [30], The ultrasound assisted decomposition precursors includes dissolving metal organic precursors in organic solvents/water with the assistance of surfactants leads to monodisperse and reduced metal/metal oxide nanoparticles. 

For some elements, there are a variety of possible precursors, sulfur for instance (Figure 11). Use of metal-organic precursors, used in MOMBE or MOVPE, are possible if they are soluble in water, or a nonaqueous solvent is used. Mixed aqueous-organic solvents could improve solubility. Overall, there would be an increased probability of carbon contamination, however. One of the benefits of using inorganic salts in aqueous solutions is that the number of constituents is limited, and thus the... 

Typically, in solution-phase film deposition, a precursor coating is applied to a surface and heated, whereupon the elimination of solvent leads to localized crystallization and separation of solid particles. To prevent these processes, metal-organic precursors can be commonly employed for sol-gel deposition (see Chapter 2), wherein the organic ligands essentially act as vehicles to promote glass formation. Ultimately, embedded organic ligands... 

Figure 14.2. Ultrasonic spray deposited CuInSe2 film for photovoltaic applications using mixed-metal organic precursors. XRD shows (left) the growth of nearly phase pure CuInSe2, and optical micrographs show reasonable morphologies (right).

This method involves the thermolysis of organometallic or metal organic precursors in a high-boiling solvent. Mostly this solvent is also a capping agent for the nanoparticles. A typical synthetic route for monodisperse nanoparticles is shown in Fig. 1. 

Heterometal alkoxide precursors, for ceramics, 12, 60-61 Heterometal chalcogenides, synthesis, 12, 62 Heterometal cubanes, as metal-organic precursor, 12, 39 Heterometallic alkenes, with platinum, 8, 639 Heterometallic alkynes, with platinum, models, 8, 650 Heterometallic clusters as heterogeneous catalyst precursors, 12, 767 in homogeneous catalysis, 12, 761 with Ni—M and Ni-C cr-bonded complexes, 8, 115 Heterometallic complexes with arene chromium carbonyls, 5, 259 bridged chromium isonitriles, 5, 274 with cyclopentadienyl hydride niobium moieties, 5, 72 with ruthenium—osmium, overview, 6, 1045—1116 with tungsten carbonyls, 5, 702 Heterometallic dimers, palladium complexes, 8, 210 Heterometallic iron-containing compounds cluster compounds, 6, 331 dinuclear compounds, 6, 319 overview, 6, 319-352... 

Metal-organic materials, photophysical properties, 12, 133 Metal-organic precursors to materials, 12, 37 overview, 12, 35-70 transformation to materials... 

For the chemical vapor deposition of ZnO, the ratio of the various precursors that participate in the chemical reaction leading to ZnO formation is an important parameter it influences the stoichiometry of the deposited films and therefore, also, their properties. DEZ and DMZ, which are the metal-organic precursors mostly used for ZnO formation, react in the presence of oxidizing agents like O2 or H2O. The equation for the complete oxidation reaction of DEZ as well as the equation for the complete reaction of DEZ with H2O are given here as examples ((6.5) and (6.6)) ... 

All these results are in good accordance with (6.5) and (6.6), which state that 7 mol of O2 are necessary to oxidize 1 mol of DEZ for ZnO formation, whereas only lmol of H2O is necessary to react with DEZ to form ZnO. Furthermore, once the threshold ratio for O/Zn is reached, i.e., once one has reached the ratio that ensures complete ZnO reaction, the growth rate becomes linearly dependent on the flow rate of the metal-organic precursor. This is illustrated in Fig. 6.26 for the growth of AP-CVD ZnO from DMZ and O2, and in Fig. 6.27 for the growth of LP-CVD ZnO from DEZ and H2O. 

Fig. 6.26. Growth rate in dependence of metal-organic precursor flow (DMZ) for AP-CVD ZnO F films deposited at a substrate temperature of 300°C. These films are deposited from DMZ, oxygen, and fluorocarbon doping gas. Reprinted with permission from [24]...

Fig. 6.27. Growth rate in function of metal-organic precursor flow (DEZ) for LP-CVD ZnO B films deposited at 155°C and 0.5mbar...

These techniques have crossovers in the sense that, for example, LCVD can be done with metal-organic precursors. Cheon and Zink (1997) deposited thin films of ZnS, CdS, and Zn,Cdi S onto quartz substrates. The source of the metal and the sulfur was the organometallic compound diethyl dithiocarbamate zinc or cadmium M(S2CNEt2)2- In this case a single precursor was used to produce a binary compound as a thin film. 

Electronic Structure of Solids Fluorides Solid-state Chemistry Halides Solid-state Chemistry Macrocyclic Ligands Metallic Materials Deposition Metal-organic Precursors Oxides Solid-state Chemistry Periodic Table Trends in the Properties of the Elements Sol-Gel Synthesis of Solids Sohds Characterization by Powder Diffraction Structure Property Maps for Inorganic Solids Superconductivity Thin Film Synthesis of Solids. 

Metallic Materials Deposition Metal-organic Precursors... 

Based in part on the article Metalhc Materials Deposition Metal-organic Precursors by Herbert D. Kaesz, Alfred Zinn, Lutz Brandt which appeared in the Encyclopedia of Inorganic Chemistry, First Edition. 

Chemical beam epitaxy a process in which one or more beams of volatile metal-organic precursors is directed to the substrate surface to effect film growth Chemical vapor deposition (CVD also termed vapor-phase epitaxy) the deposition of a thin film of an element or compound using some form of excitation for the decomposition of a volatile precursor... 

METALLIC MATERIALS DEPOSITION METAL-ORGANIC PRECURSORS... 

Many different embodiments of the CVD techniqne are available for the growth of thin films, and the readers is referred to excellent recent monographs for more detail. " The last review on metal-organic precursors that appeared in this encyclopedia contained a detailed overview of thermal CVD processes, schematics of several reactors, as well as a listing of common variants of thermal CVD processes. In addition to these well-known techniques, several new CVD techniqnes have gained importance in recent years. 

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