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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.,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.


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 3 more authors.
Thin Solid Films | Year: 2015

Three dimensional nanostructures of mesoporous (pore diameter between 2-50 nm) 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 (@ 550 nm) 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.


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.


Child D.,University of West of Scotland | Gibson D.,University of West of Scotland | Placido F.,University of West of Scotland | Waddell E.,Thin Film Solutions Ltd.
Surface and Coatings Technology | Year: 2015

A self-sustaining hollow cathode plasma source has been demonstrated to operate at an order of magnitude lower deposition pressure than previously reported, enabling plasma ion-assisted electron beam deposition at pressures of ≈. 2.0E-. 4. mbar.This method uses a restrictor plate to create a pressure differential in gas flow between a hollow cathode region and the main deposition area. The cathode operates in higher density plasma, enhancing the hollow cathode effect and enabling self-sustaining plasma formation at lower gas pressures in the deposition region. It is also demonstrated that ion energy distribution and current density at the substrate plane can be varied by changing the orifice geometry and/ or gas flow.It has been shown that by varying the restrictor orifice the proportion of thermalised ions to translational ions can be reduced, thereby reducing both substrate heating by typically 60% and defect incorporation into the deposited film. This is significant when coating low temperature materials such as plastics. Moreover the variation in ion current density over the calotte area can also be controlled by varying the geometry of the restrictor plate.The hollow cathode design described in this work utilises both the interior and exterior cathode surfaces, with the additional electrons generated removing the need for a separate neutralising source as verified by Langmuir probe measurement of electron and ion densities at the substrate plane.The effects on plasma assisted electron beam deposited TiO2 film optical and mechanical properties have been assessed and correlated with plasma source characteristics.In contrast to other hollow cathode plasma source configurations, this system has a converging magnetic field allowing electron concentration within the orifice. © 2014 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.


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.,Thin Film Solutions Ltd | Waddell E.,Thin Film Solutions Ltd | Child D.,University of West of Scotland | Placido F.,University of West of Scotland
Optics InfoBase Conference Papers | Year: 2013

Description of a plasma source including a LaB6 hollow cathode hybrid configuration operating at low gas flows and low deposition pressures provides self-sustaining plasma generation over large areas. © 2013 Optical Society of America.


Waddell E.,Thin Film Solutions Ltd. | Gibson D.,Thin Film Solutions Ltd. | Lin L.,Changchun University of Science and Technology | Fu X.,Changchun University of Science and Technology
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2011

This paper describes a method for modelling film thickness variation across the deposition area within plasma enhanced chemical vapour deposition (PECVD) processes. The model enables identification and optimization of film thickness uniformity sensitivities to electrode configuration, temperature, deposition system design and gas flow distribution. PECVD deposition utilizes a co-planar 300mm diameter electrodes with separate RF power matching to each electrode. The system has capability to adjust electrode separation and electrode temperature as parameters to optimize uniformity. Vacuum is achieved using dry pumping with real time control of butterfly valve position for active pressure control. Comparison between theory and experiment is provided for PECVD of diamond-like-carbon (DLC) deposition onto flat and curved substrate geometries. The process utilizes butane reactive feedstock with an argon carrier gas. Radio-frequency plasma is used. Deposited film thickness sensitivities to electrode geometry, plasma power density, pressure and gas flow distribution are demonstrated. Use of modelling to optimise film thickness uniformity is demonstrated. Results show DLC uniformity of 0.30% over a 200 mm flat zone diameter within overall electrode diameter of 300mm. Thickness uniformity of 0.75% is demonstrated over a 200mm diameter for a non-conformal substrate geometry. Use of the modelling method for PECVD using metal-organic chemical vapour deposition (MOCVD) feedstock is demonstrated, specifically for deposition of silica films using metal-organic tetraethoxy-silane. Excellent agreement between experimental and theory is demonstrated for conformal and non-conformal geometries. The model is used to explore scalability of PECVD processes and trade-off against film thickness uniformity. Application to MEMS, optical coatings and thin film photovoltaics is discussed.. © 2011 SPIE.


Fu X.,Changchun University of Science and Technology | Yang Y.,Changchun University of Science and Technology | Liu G.,Changchun University of Science and Technology | Li L.,Changchun University of Science and Technology | And 2 more authors.
Hongwai yu Jiguang Gongcheng/Infrared and Laser Engineering | Year: 2013

According to the special requirement of optical instrument to the uniformity of thin film thickness on infrared window, Femm42 software was adopted to analyze the potential in the vaccum of radio frequence plasma enhanced chemical vapor deposition system, by changing the height of DOME, and adding a metal ring behind the DOME, the problem of delamination on the edge of dome had solved. Taguchi experimental method was used to decrease times of experiment, at the same time, the secondary condition of effecting performance of thin film was found. The effects of the process parameters on the results of thin film thickness uniformity were analyzed. Finally, the optimal parameters had comfired. The DLC film that the uniformity is less 3% and can endure the bad environment test had successfully prepared.

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