DEPOSITION OF NANOSTRUCTURED THIN FILMS

Deposition of Nanostructured Thin Films

Deposition of Nanostructured Thin Films

Nanotechnology is set to revolutionize the conventional “top-down” manufacturing approach with a new class of materials termed as nanostructured materials. The concept of manipulating and assembling atoms and molecules at nanoscale level to build macroscale substance has produced materials with unique and novel properties not previously attainable by conventional manufacturing technique. This new class of materials, often characterized by a physical dimension of 1-100 nm in at least one dimension and the presence of very high surface area has found potential application in many areas such as electronics, magnetism, optics, energy storage, electrochemistry, and biomedical sciences.

The controlled synthesis of nanostructured materials is vital to the success of nanotechnology where various synthesis methods have since been introduced. They can be broadly classified into physical and chemical routes. Inert gas condensation, sputtering, and high-energy ball milling are among the examples of physical route, while chemical route includes sol-gel and precipitation technologies, electrodeposition, and chemical vapor condensation.

Fluorocarbon films with compositions very close to bulk PTFE were deposited from modulated discharges fed with hexafluoropropylene oxide (HFPO), with F/C ratios as high as 1.8-1.9. Lately, several studies have been devoted to the tailoring of film morphology, in addition to film chemical composition, as a way to control film properties. Superimposing a controlled surface roughness with a tunable chemical composition results in an additional tool for modulating hydrophobicity of the deposited fluorocarbon coating, eventually reaching ultra-hydrophobic character, as predicted by the Wenzel equation. In the literature, several strategies have been described to obtain water-repellent surfaces. Washo reported contact angles of 165°-170° for plasma-polymerized PTFE films deposited in the powder formation region. Other techniques include two-step processes, the first one being a roughening procedure. On the other hand, single-step deposition of fluorocarbon films by modulated discharges fed with alkene precursors containing long perfluoroalkyl chains and a maximum contact angle value of 130° was found. The field of films and coating continues to develop with new materials, processing, and applications being envisaged. This special edition of Journal of Nanomaterials examines some of the latest developments in nanostructured thin films and coatings.

Nanostructured thin films and coatings possess properties different to homogenous materials due to the deliberate engineering of nanoscale features into the structure. The seven papers presented in this special edition examine the challenges faced in fabricating nanoscale systems and composites, as well as the electrical and light interactions that occur with such small-scale systems.In the first paper, glass plate-supported nanostructure ZnO thin films were deposited by sol-gel spin coatings. The ZnO thin films are transparent ca 80-90% in visible range, and have absorption edge at about 370?nm. The c-axis orientation improves and the grain size increases, which was indicated by an increase in intensity of the (002) peak at 34.40 in XRD corresponding to the hexagonal ZnO crystal. The photocatalytic degradation of X6G, an anionic monoazo dye, in aqueous solutions was investigated, and the effects of some operational parameters such as the number of layers and ...