2 research outputs found
Reaction Pathway: Aqueous Hexatantalate Clusters to High-Density Tantalum Oxide Nanofilms
The reaction path from aqueous oxohydroxometalate
[(CH<sub>3</sub>)<sub>4</sub>N]<sub>6</sub>[H<sub>2</sub>Ta<sub>6</sub>O<sub>19</sub>]·<i>x</i>H<sub>2</sub>O to Ta<sub>2</sub>O<sub>5</sub> thin film explains observed thin-film morphological
characteristics–high
density, uniform, pore free, and smooth. Film dehydration and tetramethylammonium
thermal decomposition were observed via temperature-programmed desorption.
The morphological, structural, and optical properties of the films
were examined by X-ray diffraction, X-ray reflectivity, scanning electron
microscopy, transmission electron microscopy, atomic force microscopy,
and spectroscopic ellipsometry. Evolution of (CH<sub>3</sub>)<sub>4</sub>N<sup>+</sup> reaction products in concert with condensation
of the polyoxometalate clusters and structural relaxation led to film
densities as high as 95% of single-crystal β-Ta<sub>2</sub>O<sub>5</sub>. The process enabled film deposition with single-digit-nanometer
thickness
Role of Combustion Chemistry in Low-Temperature Deposition of Metal Oxide Thin Films from Solution
Metal-oxide thin
films find many uses in (opto)electronic and renewable
energy technologies. Their deposition by solution methods aims to
reduce manufacturing costs relative to vacuum deposition while achieving
comparable electronic properties. Solution deposition on temperature-sensitive
substrates (e.g., plastics), however, remains difficult due to the
need to produce dense films with minimal thermal input. Here, we investigate
combustion thin-film deposition, which has been proposed to produce
high-quality metal-oxide films with little externally applied heat,
thereby enabling low-temperature fabrication. We compare chemical
composition, chemical structure, and evolved species from reactions
of several metal nitrate [In(NO<sub>3</sub>)<sub>3</sub>, Y(NO<sub>3</sub>)<sub>3</sub>, and Mg(NO<sub>3</sub>)<sub>2</sub>] and fuel
additive (acetylacetone and glycine) mixtures in bulk and thin-film
forms. We observe combustion in bulk materials but not in films. It
appears acetylacetone is removed from the films before the nitrates,
whereas glycine persists in the film beyond the annealing temperatures
required for ignition in the bulk system. From analysis of X-ray photoelectron
spectra, the oxide and nitrate content as a function of temperature
are also inconsistent with combustion reactions occurring in the films.
In(NO<sub>3</sub>)<sub>3</sub> decomposes alone at low temperature
(∼200–250 °C) without fuel, and Y(NO<sub>3</sub>)<sub>3</sub> and Mg(NO<sub>3</sub>)<sub>2</sub> do not decompose
fully until high temperature even in the presence of fuel when used
to make thin films. This study therefore distinguishes bulk and thin-film
reactivity for several model oxidizer-fuel systems, and we propose
ways in which fuel additives may alter the film formation reaction
pathway