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Placido F.,University of West of Scotland | Gibson D.,Thin Film Solutions Ltd
Chinese Optics Letters | Year: 2010

A plasma source utilizing direct current (DC) voltage between an anode and a hot hollow cathode is employed to create high-density plasma. Plasma spatial distribution, ion energy, plasma neutralisation, and current densities are found to be separately tunable. Ion current densities >0.5 mA/cm2 have been demonstrated over coating areas >1 m diameter. The primary advantage of plasma, as opposed to the ion source approach, is its ability to fill in the vacuum chamber and the couple with evaporant. This induces partial evaporant ionisation, providing uniform ion-assisted deposition over extended coating areas. Optical thin film properties deposited using the adapted high ion current plasma source are likewise described. © 2010 Chinese Optics Letters.

Oliver J.B.,University of Rochester | Kupinski P.,University of Rochester | Rigatti A.L.,University of Rochester | Schmid A.W.,University of Rochester | And 10 more authors.
Applied Optics | Year: 2011

Plasma-assisted electron-beam evaporation leads to changes in the crystallinity, density, and stresses ofthin films. A dual-source plasma system provides stress control of large-aperture, high-fluence coatings used in vacuum for substrates 1 m in aperture. © 2011 Optical Society of America.

Gibson D.,Thin Film Solutions Ltd | Waddell E.,Thin Film Solutions Ltd | Placido F.,University of West of Scotland
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2011

This paper describes optical, durablility and environmental performance of a germanium carbide based durable anti-reflection coating. The coating has been demonstrated on germanium and zinc selenide infra-red material however is applicable to other materials such as zinc sulphide. The material is deposited using a novel reactive closed field magnetron sputtering technique, offering significant advantages over conventional evaporation processes for germanium carbide such as plasma enhanced chemical vapour deposition. The sputtering process is "cold", making it suitable for use on a wide range of substrates. Moreover, the drum format provide more efficient loading for high throughput production. The use of the closed field and unbalanced magnetrons creates a magnetic confinement that extends the electron mean free path leading to high ion current densities. The combination of high current densities with ion energies in the range ∼30eV creates optimum thin film growth conditions. As a result the films are dense, spectrally stable, supersmooth and low stress. Films incorporate low hydrogen content resulting in minimal C-H absorption bands within critical infra-red passbands such as 3 to 5um and 8 to 12um. Tuning of germanium carbide (Ge( 1-x)C x) film refractive index from pure germanium (refractive index 4) to pure germanium carbide (refractive index 1.8) will be demonstrated. Use of film grading to achieve single and dual band anti-reflection performance will be shown. Environmental and durability levels are shown to be suitable for use in harsh external environments. © 2011 SPIE.

Gibson D.,University of West of Scotland | Child D.,University of West of Scotland | Song S.,University of West of Scotland | Zhao C.,University of West of Scotland | And 2 more authors.
Thin Solid Films | Year: 2015

Three dimensional nanostructures of mesoporous (pore diameter between 2-50nm) nanocrystalline titania (TiO2) were produced using glancing angle deposition combined with plasma ion assisted deposition, providing plasma enhanced glancing angle deposition eliminating the need for post-annealing to achieve film crystallinity. Electron beam evaporation was chosen to deposit nanostructures at various azimuthal angles, achieving designed variation in three dimensional nanostructure. A thermionic broad beam hollow cathode plasma source was used to enhance electron beam deposition, with ability to vary in real time ion fluxes and energies providing a means to modify and control TiO2 nanostructure real time with controlled density and porosity along and lateral to film growth direction. Plasma ion assisted deposition was carried out at room temperature using a hollow cathode plasma source, ensuring low heat loading to the substrate during deposition. Plasma enhanced glancing angle TiO2 structures were deposited onto borosilicate microscope slides and used to characterise the effects of glancing angle and plasma ion energy distribution function on the optical and nanostructural properties. Variation in TiO2 refractive index from 1.40 to 2.45 (@ 550nm) using PEGLAD is demonstrated. Results and analysis of the influence of plasma enhanced glancing angle deposition on evaporant path and resultant glancing angle deviation from standard GLAD are described. Control of mesoporous morphology is described, providing a means of optimising light trapping features and film porosity, relevant to applications such as fabrication of dye sensitised solar cells. © 2015 Elsevier B.V.

Zhao C.,University of West of Scotland | Child D.,University of West of Scotland | Gibson D.,University of West of Scotland | Gibson D.,Thin Film Solutions Ltd | And 2 more authors.
Materials Research Bulletin | Year: 2014

Anatase TiO2 films were synthesized on glass substrates using a plasma ion assisted deposition (PIAD) without external heating or subsequent annealing. The low temperature PIAD process produced crystalline anatase films with increased hardness and Young's modulus, reduced film surface roughness and improved optical properties compared with those deposited without ion assistance, as well as a possibility to be applied to a wider range of substrates. Photocatalytic characterization showed that significant increases in photocatalytic stability and efficiency were achieved after using the PIAD process, although surface roughness and porosity of the films decreased slightly. © 2014 Elsevier Ltd. All rights reserved.

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