Metal-containing precursors

Ion layer gas reaction (ILGAR) is an alternative sequential chemical deposition technique for which a metal-containing precursor solution is first transferred to the substrate by dipping (dip-ILGAR) or spraying (spray-ILGAR)... 

The volatile metal-containing precursors which satisfy the ALD criteria fall into four main categories (i) halides, (ii) y0-diketonate complexes, (iii) alkoxides, and (iv) true organometallics, viz. metal alkyls and cyclopentadienyl-type compounds (Fig. 3). Also amido complexes have recently gained attention as possible ALD precursors. Occasionally other compounds have been used as ALD precursors for thin films, for instance, metal nitrates, carboxy-lates and isocyanates [17,18]. 

Generally two approaches can be used to prepare metal clusters in zeolites. One involves direct evaporation and deposition of metals into the pores of zeolites, whereas the other is to load the metal-containing precursors into the zeolite pores followed by formation of metal clusters in the zeolite pores through decomposition or reduction.[3] According to the preparation techniques used, these two approaches can be further divided into the following sub-approaches ... 

The ion source is a custom designed variable temperature EI/CI source. Metal containing precursor ions are formed by electron impact (150 eV) ionization and fragmentation of volatile precursors such as Fe(CO)5 Co(CO)3NO. T ical source pressures are lO torr, and source temperatures are kept below 280 K to minimize decomposition of the organometallics on insulating surfaces. Adduct formation results from reaction of an atomic metal ion or metal containing species with small molecules. The ion source is operated under nearly field free conditions to prevent translational excitation of the ions, which are accelerated to 8 kV before mass analysis. 

Krocher et al. (184) reported preparation of neutral Ru(ll), lr(l), and Pt(ll) trimethoxysilyl phosphine complexes that were obtained in high yield and purity by synthesis in methanol followed by evaporation of solvent, extraction into CH2CI2, filtration through Celite and evaporation, which afforded the products as oils. Reaction of appropriate metal-cod (cod= 1,4-cycloocatadiene) precursors resulted in mixtures of isomers, however, which were not separated. In particular, mthenium complexes proved troublesome—up to five isomeric complexes were discernible by NMR, and purification was not possible. The authors noted that the presence of the silylated sidechains hampered purification by standard methods (see above). This result illustrates the difficulties associated with preparation of pure metal-containing precursors for sol-gel syntheses. 

Metal-containing polymers may be produced by various methods, such as chemical reactions of precursors— in particular, reactions of metal salts in polymer solutions, the treatment of polymers with metal vapors, or the polymerization of various metal-monomer systems [1-4], Depending on the metal nature and the polymer structure, these processes lead to organometallic units incorporated into polymer chains, metal-polymer complexes, or metal clusters and nanoparticles physically connected with polymer matrix. Of special interest are syntheses with the use of metal vapors. In this case, metal atoms or clusters are not protected by complexones or solvate envelopes and consequently have specific high reactivity. It should be noted that the apparatus and principles of metal vapor synthesis techniques are closely related to many industrial processes with participation of atomic and molecular species [5]—for example, manufacturing devices for microelectronic from different metals and metal containing precursors [6]. Vapor synthesis methods employ varying metals and... 

It must be noted that the metal-containing precursors and the nanoparticle interactions with the polymer matrix (formed under the pyrolysis), as well as the product topography, are not sufficiently studied, but it is no question that a role of metal centers and their activities are very important for the general picture of the metal particles interaction with a polymer matrix. 

---