Chemical Vapor Deposition

The problem of simultaneous growth and competition of intermediate phases is presented. The volume continuity equation is used to compute the material velocity in a reacting system in which reactions occur at several moving interfaces. The growth of multiphase layers is show. The CVD process and annealing in a non-oxidizing atmosphere are simulated. The kinetics and concentration profile of the reactive diffusion in an Al-Ni system are compared with experiments.

Microscopic liquid monomer droplets are encapsulated in an ultrathin polymeric film grown by photo-DLICVD. When the temperature increases, the liquid expands. The monomer (i.e., the encapsulated liquid) expands faster, exerting a strain on the polymer (solid membrane). This strain (ε_τ) is proportional to the difference in temperature (ΔT). Beyond a threshold value, the strain leads to a rupture of the polymeric film and a release of the liquid internal phase.

ZnO nanostructures are grown under a number of different conditions yielding a wide range of microstructures from “nano-stars”, “nano-caterpillars”, urchin-like structures to vertically aligned forests of hexagonal nanorods. For the nano-caterpillars, hexagonal crystals grow from the catalytic substrate allowing propagation of parent pillars, which subsequently form “daughter” rods propagating sideways from the faces.

Full Paper: Dense, crack-free thin films (<5 µm) of a nanostructured scandia-zirconia system (Sc₂O₃:ZrO₂), both partially and fully stabilized in the cubic-fluorite phase (c-ZrO₂), are deposited onto porous substrates (Al₂O₃ and NiO/YSZ cermet) through conventional LP-MOCVD. The crystal structure, the morphology, and the composition of deposits are investigated. To evaluate the ionic transport properties, the in-plane conductivity of the thin films is measured.

The growth of zinc-doped indium oxide nanostructures from mesocontainers to nanowires by the use of thermal vapor transport of an In₂O₃ + ZnO mixed precursor under oxidizing and reducing environments is reported. Surprisingly, a change of the growth environment from reducing to oxidizing (or inert) results in the growth of In₂O₃-ZnO nanowires (or nanorods). This study provides insight into the growth of In₂O₃-ZnO ternary oxide nanostructures.

Boron-doped homoepitaxial diamond films are deposited from ethanol/trimethyl borate/hydrogen mixtures activated by a microwave discharge plasma. Measurements of film surface roughness show their excellent smoothness, which usually corresponds to a low concentration of growth defects. A uniform distribution of boron atoms located predominantly in substitution positions and low concentration of the nitrogen compensating impurity is achieved.

Atmospheric-pressure, linear, cold plasma is employed to deposit TiO₂ photocatalytic films uniformly on a moving substrate. Raman, XRD, and FTIR spectra prove that the structures of the as-deposited and calcined TiO₂ films are mainly hydro-oxygenated amorphous (a-TiO_x:OH) and anatase, respectively. All the as-deposited TiO₂ films exhibit clear photocatalytic activity in complete oxidation of HCHO to CO₂.

The deposition of ZnO and CoO thin films using ALD on γ-alumina nanoporous particles and membrane discs with the objective of converting their surfaces into mechanically more robust, nanoporous, alumina spinel phases is described. The porosity is maintained by utilizing subsequent reactions between the coated layer and γ-alumina, based on the Kirkendall mechanism. This represents a new way to produce highly porous spinel.

Carbon nanotubes (CNTs) are grown by catalytic CVD on Al foils using a variety of supported catalyst combinations. The morphology of the nanotube arrays is found to be dependent on the nature of the catalyst combination used. Thermodynamic calculations are performed to clearly understand the correlation between the chemical constitution of catalyst mixtures and the morphology of the resulting nanotube arrays.

Using MOCVD, gold films and arrays of gold nanoparticles are obtained from volatile organometallic dimethylgold(III) complexes with O, N, S donor ligands. The deposition processes are carried out within an LPCVD reactor with additional VUV stimulation, with and without hydrogen as the reactant gas. The influence of the structure of the precursor on the morphology, structure, and composition of the thin gold films and gold nanoparticles are investigated.