Thin Film Deposition By Sol-Gel and CVD Processing of Metal-Organic Precursors

Molecule Derived Synthesis of Nanocrystalline YFeO3 and Investigations on Its Weak Ferromagnetic Behavior

“…Thermodynamically labile phases cannot be selectively prepared by traditional processing routes due to rather harsh reaction conditions that are driven by equilibrium thermodynamics. In this context, the chemical reactions based on controlled interaction of atoms or molecules in vapor or liquid phase are viable alternatives to obtain metastable compounds as nanostructured films or particles. − ,, ,, However, a straightforward synthesis is not guaranteed by all chemical approaches, and the processing of mixed-oxide ceramics by conventional wet-chemical techniques does not always lead to a stoichiometric compound. The major problems faced are component segregation, mixed phases, or nonideal stoichiometry in the final ceramic material caused by intrinsic differences in the chemical properties of the reacting species.…”

“…Chemical synthesis of nanomaterials is based on the transformation of molecular compounds into materials in which the structural units present in the precursor molecule are carried forward to the target solid-state structure. − This strategy provides the means to grow the solid-state structures from molecular “seeds”. For instance, metal alkoxides (M(OR) x ) in view of preformed metal−oxygen bonds are efficient precursors to metal oxides (MO x ). − Although monometal nanocrystalline ceramics (e.g., Al 2 O 3 , TiO 2 , ZrO 2 , CeO 2 , SnO 2 , and Nb 2 O 5 ) have been obtained from molecular chemistry routes, the extension of this approach to multicomponent oxides is rather limited mainly due to the (i) misbelief that the heterometal framework would break down into monometal constituents during the processing steps, and (ii) commercial unavailability of heterometal precursors. − The use of precursors containing two or more different metallic elements is especially important where the simultaneous growth of different phases and the presence of metastable compounds in the phase-diagram make the phase-selective synthesis a difficult task. For instance, the synthesis of the title compound, YFeO 3 , is not straightforward because of the preferred formation of Y 3 Fe 5 O 12 (YIG) composition in the Y 2 O 3 −Fe 2 O 3 system .…”

“…We describe here the sol−gel processing of a Y−Fe mixed-metal alkoxide, [YFe(OPr i ) 6 (Pr i OH)] 2 that is an effective molecular scaffold to synthesize YFeO 3 nanoparticles with a precise chemical composition and particle size control. The existence of −Y−O(R)−Fe− linkages in the precursor and an appropriate Y/Fe ratio enforces the formation of YFeO 3 with a precise stoichiometry control and prevents any element segregation generally observed in conventional methods. , …”

Nanocrystalline Bimetallic Oxides from Molecular Precursors

“…Our investigations on the application of heterometal alkoxides in nanomaterial synthesis [4][5][6][7][8][9][10]13,14] show that owing to their chemical constitution, these compounds can act as molecular templates for directing the evolution of solid-state structures. The following section contains selected examples of the synthesis of nanocrystalline ceramics from molecular precursors that illustrate the synthetic opportunities in terms of precursor designing and the potential of molecular chemical concepts in nanomaterial synthesis.…”

Chemical Vapor Deposition of MgAl2O4 Thin Films Using Different Mg−Al Alkoxides: Role of Precursor Chemistry

“…MgAl 2 O 4 films have been grown by conventional CVD using MgCl 2 , Al, HCl, CO 2 , and H 2 as starting materials and carrier gases, however high growth temperature (980 °C) and poor stoichiometry in the film were the major shortcomings . Despite the promises of molecular precursors, their application is seen with skepticism mainly due to lack of (i) suitable precursor compounds, especially for bimetallic oxides, with adequate vapor pressure, and (ii) evidence for the conservation of stoichiometry present in the molecular source, during the CVD process ( proof of the concept ). In addition, systematic studies on precursor chemistry and its relation to the final material properties are missing.…”