Martyn E. Pemble

Bio: Martyn E. Pemble is an academic researcher from Tyndall National Institute. The author has contributed to research in topics: Thin film & Photonic crystal. The author has an hindex of 37, co-authored 263 publications receiving 5981 citations. Previous affiliations of Martyn E. Pemble include University of Manchester & National University of Ireland.

Intelligent window coatings: Atmospheric pressure chemical vapor deposition of tungsten-doped vanadium dioxide

Abstract: Thin films of tungsten-doped vanadium(IV) oxide were prepared on glass substrates from the atmospheric pressure chemical vapor deposition of vanadium(IV) chloride, tungsten(VI) ethoxide, and water at 500−600 °C. The films were characterized by Raman microscopy, glancing angle X-ray diffraction (GAXRD), X-ray photoelectron spectroscopy (XPS), Rutherford backscattering (RBS), scanning electron microscopy (SEM), and vis/IR reflectance−transmittance. The films showed a reduction in thermochromic transition temperatures from 68 °C in VO2 to 42 °C in V0.99W0.01O2approaching that required for commercial use as an intelligent window coating.

Intelligent window coatings: atmospheric pressure chemical vapour deposition of vanadium oxides

Abstract: Thin films of the vanadium oxides, V2O5, VO2, VOx (x = 2.00–2.50) and V6O13 were prepared on glass substrates by atmospheric pressure chemical vapour deposition (APCVD) of vanadium tetrachloride and water at 400–550 °C. The specific phase deposited was found to be dependent on the substrate temperature and the reagent concentrations. The films were characterised by Raman microscopy, X-ray diffraction (XRD), Rutherford backscattering (RBS), scanning electron microscopy (SEM), energy dispersive analysis by X-rays (EDX), reflectance/transmittance and UV absorption spectroscopy. The VO2 films show by Raman microscopy and reflectance/transmittance spectroscopy, reversible switching behaviour at 68 °C associated with a phase change from monoclinic (MoO2 structure) to tetragonal (TiO2, rutile structure).

The role of nitrogen doping on the development of visible light-induced photocatalytic activity in thin TiO2 films grown on glass by chemical vapour deposition

Abstract: A brief review of the findings of a range of studies aimed at describing the influence of the N-doping of TiO2 thin films and particles on possible visible light induced photoactivity is presented. By way of a new approach to the direct growth of N-doped TiO2 thin films, the physical and photochemical effects of the addition of ammonia during atmospheric chemical vapour deposition (CVD) growth of TiO2 are described. It is found that the addition of ammonia to the CVD reactive gas mixture causes a dramatic change in film morphology and a reduction in growth rates. In addition, it is found that although we have clear evidence for the incorporation of ?O-substitutional N atoms within the growing film, there is no evidence of any appreciable photocatalytic activity of the doped TiO2 films when irradiated with visible light. In fact the degradation in film morphology results in a decrease in conventional uv-induced photoactivity as compared to that for an undoped film. These findings are discussed in terms of the findings of other studies of N-doped TiO2 films that have been reported.

The langmuir-blodgett approach to making colloidal photonic crystals from silica spheres.

Abstract: The area of colloidal photonic crystal research has attracted enormous attention in recent years as a result of the potential of such materials to provide the means of fabricating new or improved photonic devices. As an area where chemistry still predominates over engineering the field is still in its infancy in terms of finding real applications being limited by ease of fabrication, reproducibility and 'quality'- for example the extent to which ordered structures may be prepared over large areas. It is our contention that the Langmuir-Blodgett assembly method when applied to colloidal particles of silica and perhaps other materials, offers a way of overcoming these issues. To this end the assembly of silica and other particles into colloidal photonic crystals using the Langmuir-Blodgett (LB) method is described and some of the numerous papers on this topic, which have been published, are reviewed. It is shown that the layer-by-layer control of photonic crystal growth afforded by the LB method allows for the fabrication of a range of novel, layered photonic crystals that may not be easily assembled using any other approach. Some of the more interesting of these structures, including so-called heterostructured photonic crystals comprising of layers of spheres having different diameters are presented and their optical properties described. Finally, we offer our comments as to future applications of this interesting technology.

Magnetic Field-Induced Ferroelectric Switching in Multiferroic Aurivillius Phase Thin Films at Room Temperature

Abstract: Science Foundation Ireland ((SFI FORME Strategic Research Cluster Award number 07/SRC/I1172), (SFI Starting Investigator Research Grant (09/SIRG/I1621)), (SFI 09/SIRG/I1615)); European Commission (COST Action MP0904 (Single and multiphase ferroics and multiferroics with restricted geometries (SIMUFER)).

Surface chemistry of atomic layer deposition: A case study for the trimethylaluminum/water process

Abstract: Atomic layer deposition(ALD), a chemical vapor deposition technique based on sequential self-terminating gas–solid reactions, has for about four decades been applied for manufacturing conformal inorganic material layers with thickness down to the nanometer range. Despite the numerous successful applications of material growth by ALD, many physicochemical processes that control ALD growth are not yet sufficiently understood. To increase understanding of ALD processes, overviews are needed not only of the existing ALD processes and their applications, but also of the knowledge of the surface chemistry of specific ALD processes. This work aims to start the overviews on specific ALD processes by reviewing the experimental information available on the surface chemistry of the trimethylaluminum/water process. This process is generally known as a rather ideal ALD process, and plenty of information is available on its surface chemistry. This in-depth summary of the surface chemistry of one representative ALD process aims also to provide a view on the current status of understanding the surface chemistry of ALD, in general. The review starts by describing the basic characteristics of ALD, discussing the history of ALD—including the question who made the first ALD experiments—and giving an overview of the two-reactant ALD processes investigated to date. Second, the basic concepts related to the surface chemistry of ALD are described from a generic viewpoint applicable to all ALD processes based on compound reactants. This description includes physicochemical requirements for self-terminating reactions,reaction kinetics, typical chemisorption mechanisms, factors causing saturation, reasons for growth of less than a monolayer per cycle, effect of the temperature and number of cycles on the growth per cycle (GPC), and the growth mode. A comparison is made of three models available for estimating the sterically allowed value of GPC in ALD. Third, the experimental information on the surface chemistry in the trimethylaluminum/water ALD process are reviewed using the concepts developed in the second part of this review. The results are reviewed critically, with an aim to combine the information obtained in different types of investigations, such as growth experiments on flat substrates and reaction chemistry investigation on high-surface-area materials. Although the surface chemistry of the trimethylaluminum/water ALD process is rather well understood, systematic investigations of the reaction kinetics and the growth mode on different substrates are still missing. The last part of the review is devoted to discussing issues which may hamper surface chemistry investigations of ALD, such as problematic historical assumptions, nonstandard terminology, and the effect of experimental conditions on the surface chemistry of ALD. I hope that this review can help the newcomer get acquainted with the exciting and challenging field of surface chemistry of ALD and can serve as a useful guide for the specialist towards the fifth decade of ALD research.

Two-photon polymerization initiators for three-dimensional optical data storage and microfabrication

Abstract: Two-photon excitation provides a means of activating chemical or physical processes with high spatial resolution in three dimensions and has made possible the development of three-dimensional fluorescence imaging, optical data storage, and lithographic microfabrication. These applications take advantage of the fact that the two-photon absorption probability depends quadratically on intensity, so under tight-focusing conditions, the absorption is confined at the focus to a volume of order λ3 (where λ is the laser wavelength). Any subsequent process, such as fluorescence or a photoinduced chemical reaction, is also localized in this small volume. Although three-dimensional data storage and microfabrication have been illustrated using two-photon-initiated polymerization of resins incorporating conventional ultraviolet-absorbing initiators, such photopolymer systems exhibit low photosensitivity as the initiators have small two-photon absorption cross-sections (δ). Consequently, this approach requires high laser power, and its widespread use remains impractical. Here we report on a class of π;-conjugated compounds that exhibit large δ (as high as 1, 250 × 10−50 cm4 s per photon) and enhanced two-photon sensitivity relative to ultraviolet initiators. Two-photon excitable resins based on these new initiators have been developed and used to demonstrate a scheme for three-dimensional data storage which permits fluorescent and refractive read-out, and the fabrication of three-dimensional micro-optical and micromechanical structures, including photonic-bandgap-type structures.