We have studied the chemical and material aspects of molecular precursor-derived materials taking the example of the spinel MgAl2O4. Three Mg−Al alkoxides, [MgAl2(OPri)8], [MgAl2(OBut)8] and [MgAl2(OBut)4H4] were used as single molecular precursors in the gas-phase synthesis of the MgAl2O4 films. A comparative evaluation of the growth rates, morphology, microstructure, average particle size, consistency of elemental ratio, and carbon contamination in the films shows that material properties of the CVD deposits are a function of the chemical design of the precursor molecule. The intrinsic precursor properties (physical state, vapor pressure, decomposition temperature, etc.) can be tuned by a judicious choice of ligand(s) or their combination. For instance, [MgAl2(OPri)8] based on isopropoxide ligands displays a potential to oligomerize upon aging due to the presence of an unsaturated metal center (Mg) in the precursor framework. Nevertheless, the liquid state of [MgAl2(OPri)8] provides adequate vapor pressure for growing high-quality spinel films. In contrast, the bulkier tert-butoxide groups in [MgAl2(OBut)8] make it thermally and structurally more stable, however causing a lower vapor pressure and higher decomposition temperature. [MgAl2(OBut)4H4] exhibits substantially high vapor pressure but the films obtained contain small amounts of residual organics, although the combination of hydride and tert-butoxide ligands in [MgAl2(OBut)4H4] induces a designed ligand elimination, based on the β-hydride elimination. Despite the fact that microstructured MgAl2O4 films with sufficient crystallinity and a columnar microstructure could be obtained by tuning the growth parameters of the three Mg−Al compounds, this study underscores the importance of precursor chemistry in designing an efficient CVD process.

Detecting small quantities of gases and chemicals is becoming increasingly important for consumer, health and security applications such as monitoring the ecological constituents, concentration control of toxic and hazardous gases. [1][2][3][4] Nanostructures are especially attractive for detector and quantifier applications, particularly due to their high surface-to-volume ratio and higher sensitivity towards surface reactions, which results in charge penetration layers being comparable to nanostructure dimensions. The signal transduction in metal oxide nanostructures based on magnitude of alteration in their electrical properties has been reported for various components, however adsorption of oxidising or reducing species and their effect on surface potential, which influences the electrical properties of semiconductor nanostructures, have been reported with mostly an optimization of their performance. [5][6][7][8][9][10][11] Tin oxide (SnO 2 ) represents the class of IV-VI compound semiconductors with a wide band gap (3.6-4.0 eV) at room temperature and intrinsic n-type electrical conductivity. [12,13] Given their low electrical resistivity (10 -2 -10 -4 Xcm), high chemical resistance, thermal stability and mechanical strength, [14] SnO 2 nanostructures offer promising potential for improved chemical sensing behaviour particularly due to the enhancement of redox reactions between different oxidation states of tin. [15] This redox switching facilitates a reversible transformation of the surface composition from Sn 4+ cations on the surface into a reduced surface with Sn 2+ cations depending on the oxygen chemical potential of the system. [16] Tin oxide nanostructures have been synthesized by a number of methods such as chemical vapor transport at high temperatures, [17,18] thermal evaporation of tin oxide powders [19] and plasma enhanced chemical vapor deposition. [20] Although a large body of data is available on the synthesis of tin oxide nanostructures (particles, films, nanowires and nanobelts) in pure and doped compositions, synthetic pathways for their controlled growth and modification remains an overarching task. We have recently reported a molecule-based chemical vapor deposition (CVD) process for the synthesis of tin oxide and other semiconductor nanowires. [21][22][23] The preformed Sn-O units in the precursor molecule [Sn(O t Bu) 4 ] and the facile and clear stripping of organic ligands resulted in single crystalline SnO 2 nanowires at relatively low temperatures. Herein we describe the controlled growth of single crystal tin oxide platelets followed by modulation of their morphology and composition induced by argon and oxygen plasma.Semiconductor oxide nanostructures with ideal stoichiometric balance (electro-neutrality) are poor transducers for chemical sensing due to low signal-to-noise ratio, making excessive signal amplifications and/or high operating temperatures mandatory for optimal sensing performance. Since electrical properties of tin oxide depend on oxygen vacancies, mobility and concent...

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Transparent and scratch‐resistant zirconium oxide thin films were deposited in radio‐frequency plasma‐enhanced chemical vapor deposition process on glass and polycarbonate substrates using zirconium‐tetra‐tert‐butoxide, [Zr(OtBu)4], as the precursor. Investigations on film morphology (AFM), thickness (cross‐sectional SEM), phase structure (X‐ray diffraction), chemical composition (X‐ray photoelectron spectroscopy), and optical properties (UV/Vis, ellipsometry) revealed the interplay of process parameters (plasma power, gas composition, deposition time, and precursor flux) on the composition and properties of the coatings. High‐quality transparent coatings (>90%) with a tunable refractive index (n=1.7–2.1) and abrasion‐resistant properties were deposited on both polymer and glass substrates. Despite low deposition temperatures (<100°C), the coatings showed good adherence to the substrate and extraordinary barrier properties that were further improved by depositing intermediary SiOx‐layers. Phase analysis of the predominantly amorphous films showed the incipient crystallization of ZrO2.