An Aerosol-Assisted Chemical Vapor Deposition Route to Tin-Doped Gallium Oxide Thin Films with Optoelectronic Properties

Gallium oxide is a wide-bandgap compound semiconductor material renowned for its diverse applications spanning gas sensors, liquid crystal displays, transparent electrodes, and ultraviolet detectors. This paper details the aerosol assisted chemical vapor deposition synthesis of tin doped gallium oxide thin films using gallium acetylacetonate and monobutyltin trichloride dissolved in methanol. It was observed that Sn doping resulted in a reduction in the transmittance of Ga2O3 films within the visible spectrum, while preserving the wide bandgap characteristics of 4.8 eV. Furthermore, Hall effect testing revealed a substantial decrease in the resistivity of Sn-doped Ga2O3 films, reducing it from 4.2 × 106 Ω cm to 2 × 105 Ω cm for the 2.5 at. % Sn:Ga2O3 compared to the nominally undoped Ga2O3

Recent advances in low oxidation state aluminium chemistry

Documenting the synthesis and isolation of novel low oxidation state aluminium (Al) compounds, which until recently has seen relatively slow progress over the 30 years since such species were first isolated

Transparent and conducting boron doped ZnO thin films grown by aerosol assisted chemical vapor deposition.

ZnO based transparent conducting oxides are important as they provide an alternative to the more expensive Sn : In O that currently dominates the industry. Here, we investigate B-doped ZnO thin films grown aerosol assisted chemical vapour deposition. B : ZnO films were produced from zinc acetate and triethylborane using either tetrahydrofuran or methanol (MeOH) as the solvent. The lowest resistivity of 5.1 × 10 Ω cm along with a visible light transmittance of ∼75-80% was achieved when using MeOH as the solvent. XRD analysis only detected the wurtzite phase of ZnO suggesting successful solid solution formation with B substituting Zn sites in the lattice. Refinement of the XRD patterns showed minimal distortion to the ZnO unit cell upon doping when MeOH was the solvent due to the immiscibility of the [BEt ] solution (1.0 M solution in hexane) in methanol that limited the amount of B going into the films, thus preventing excessive doping. [Abstract copyright: This journal is © The Royal Society of Chemistry.

Aluminum Amidinates: Insights into Alkyne Hydroboration.

The mechanism of the aluminum-mediated hydroboration of terminal alkynes was investigated using a series of novel aluminum amidinate hydride and alkyl complexes bearing symmetric and asymmetric ligands. The new aluminum complexes were fully characterized and found to facilitate the formation of the (E)-vinylboronate hydroboration product, with rates and orders of reaction linked to complex size and stability. Kinetic analysis and stoichiometric reactions were used to elucidate the mechanism, which we propose to proceed via the initial formation of an Al-borane adduct. Additionally, the most unstable complex was found to promote decomposition of the pinacolborane substrate to borane (BH3), which can then proceed to catalyze the reaction. This mechanism is in contrast to previously reported aluminum hydride-catalyzed hydroboration reactions, which are proposed to proceed via the initial formation of an aluminum acetylide, or by hydroalumination to form a vinylboronate ester as the first step in the catalytic cycle

Metal β-diketoiminate precursor use in aerosol assisted chemical vapour deposition of gallium- and aluminium-doped zinc oxide

Aerosol assisted chemical vapour deposition (AACVD) has been used to deposit thin films of ZnO from the single-source precursor [Zn(OC(Me)CHC(Me)N( i Pr)) 2 ] (1) affording highly transparent ( > 80%) and conductive films (sheet resistance ∼70 KΩ/sq). Extension of this AACVD method whereby related precursors of the type, [R 2 M(OC(Me)CHC(Me)N( i Pr))] (R = Et, M = Al (2); R = Me, M = Ga (3)), isolated as oils, were added to the precursor solution allowed for the deposition of aluminium- and gallium-doped ZnO (AZO and GZO) films, respectively. Complexes 1–3 were characterised by elemental analysis, NMR and mass spectrometry. Films were deposited in under 30 min at 400 °C, from CH 2 Cl 2 /toluene solutions with a N 2 carrier gas. Herein we report the bulk resistivity, ρ, of AZO (0.252 Ω cm) and GZO (0.756 Ω cm) films deposited from this novel approach. All the films transparency exceeded 80% in the visible, X-ray diffraction (XRD) showed all films to crystallise in the wurtzite phase whilst X-ray photoemission spectroscopy (XPS) confirmed the presence of the Al and Ga dopants in the films, and highlighted the low C-contamination ( < 5%) this route offers. Investigation of a mechanism analogous to the Kirkendall effect confirmed that heating of GZO films at 1000 °C produced the spinel structure GaZn 2 O 4

Visible-Light-Active Iodide-Doped BiOBr Coatings for Sustainable Infrastructure

The search for efficient materials for sustainable infrastructure is an urgent challenge toward potential negative emission technologies and the global environmental crisis. Pleasant, efficient sunlight-activated coatings for applications in self-cleaning windows are sought in the glass industry, particularly those produced from scalable technologies. The current work presents visible-light-active iodide-doped BiOBr thin films fabricated using aerosol-assisted chemical vapor deposition. The impact of dopant concentration on the structural, morphological, and optical properties was studied systematically. The photocatalytic properties of the parent materials and as-deposited doped films were evaluated using the smart ink test. An optimized material was identified as containing 2.7 atom % iodide dopant. Insight into the photocatalytic behavior of these coatings was gathered from photoluminescence and photoelectrochemical studies. The optimum photocatalytic performance could be explained from a balance between photon absorption, charge generation, carrier separation, and charge transport properties under 450 nm irradiation. This optimized iodide-doped BiOBr coating is an excellent candidate for the photodegradation of volatile organic pollutants, with potential applications in self-cleaning windows and other surfaces

Scalable Production of Ambient Stable Hybrid Bismuth-based Materials: AACVD of Phenethylammonium Bismuth Iodide Films

Large homogeneous and adherent coatings of phenethylammonium bismuth iodide were produced using the cost-effective and scalable aerosol-assisted chemical vapour deposition (AACVD) methodology. The film morphology was found to depend on the deposition conditions and substrates, resulting in different optical properties to those reported from their spin-coated counterparts. Optoelectronic characterization revealed band bending effects occurring between the hybrid material and semiconducting substrates (TiO2 and FTO) due to heterojunction formation, and the optical bandgap of the hybrid material was calculated from UV-visible and PL spectrometry to be 2.05 eV. Maximum values for hydrophobicity and crystallographic preferential orientation were observed for films deposited on FTO/glass substrates, closely followed by values from films deposited on TiO2/glass substrates

In situ mass spectrometry analysis of chemical vapour deposition of TiO2 thin films to study gas phase mechanisms

Deposition of TiO2 thin films are studied using a newly developed in situ mass spectrometry technique to observe gas phase reactions. Atmospheric pressure chemical vapour deposition (APCVD) reactions were carried out using titanium chloride and titanium tetraisopropoxide precursors, with ethyl acetate acting as an oxygen source in the case of the former, depositing on to float glass substrates at 300 and 600 °C. Using an atmospheric sampling mass spectrometer, the vapour phase was analysed during deposition and signals assigned to intermediate species that were measured during the formation of the thin films. The films deposited were characterised via scanning electron microscopy, X-ray photoelectron spectroscopy and thin film X-ray diffraction analysis

Crystal Violet-Impregnated Slippery Surface to Prevent Bacterial Contamination of Surfaces

Biofilms which are self-organized communities can contaminate various infrastructural systems. Preventing bacterial adhesion on surfaces is more desirable than cleaning or disinfection of bacteria-contaminated surfaces. In this study, a 24 h bacterial adhesion test showed that “slippery surfaces” had increased resistance to bacterial contamination compared to polydimethylsiloxane and superhydrophobic surfaces. However, it did not completely inhibit bacterial attachment, indicating that it only retards surface contamination by bacteria. Hence, a strategy of killing bacteria with minimal bacterial adhesion was developed. A crystal violet-impregnated slippery (CVIS) surface with bactericidal and slippery features was produced through a simple dipping process. The CVIS surface had a very smooth and lubricated surface that was highly repellent to water and blood contamination. Bactericidal tests against Escherichia coli and Staphylococcus aureus showed that the CVIS surface exhibited bactericidal activity in dark and also showed significantly enhanced bactericidal activity (>3 log reduction in bacteria number) in white light