Surface Modification via Atomic Layer Deposition

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Atomic Layer Deposition (ALD) is a thin-film technique that owes much to Chemical Vapour Deposition (CVD), but provides for atomic level control of the growing film and therefore unique opportunities for depositing complex and layered thin-films. The deposited films are pinhole free and, crucially, have a low defect density, whilst the inherent 100% film density provides near 'ideal' properties for a given material. ALD is a technique that can be used for surface modification and has the advantage that it is a low temperature technique in contrast to CVD. The aim of this project is to investigate the use of ALD to modify surfaces in order to tune the surface's hydrophilic/hydrophobic property (metal oxides or polymers). ALD will be used to modify surfaces, such as oxides, to be either hydrophobic or hydrophilic by changing deposition mode from thermal to plasma-enhanced. Hydrophobicity is a key surface property for a range of applications, where water adsorption can deteriorate the performance such as for protective coatings on microelectromechanical systems (MEMSs) or gas diffusion barrier layers on polymer substrates. To alter a surface, such as a metal oxide, from hydrophilic to hydrophobic, typically requires the use of fluorinated polymers, which are harmful to the environment. Using ALD, the proposed project will take advantage of the low temperature of deposition and the ease of modification of the surface to achieve coatings on polymers, such as those utilised in slip resistant PVC safety flooring and hygienic PVC wall cladding. Together this combination could create an innovative new 'easy-to-clean' coating for slip-resistant flooring and hygienic PVC wall cladding. This will link in with healthcare and manufacturing technologies theme area of the EPSRC. The ALD-deposited metal oxide films on PVC would also act as an effective passivation layer between the PVC and the environment. This could then be expanded into other applications such as in coatings for solar cells.