This paper aims to discuss and review developments in plasma surface modification techniques which have been seen over the past few years, with particular emphasis on low enrgy or soft plasma assisted surface polymerisation processes. While early work focussed mainly on protective coatings and surface activation, the advancements in microtechnology in the 1980s followed by those in nanotechnology in the 1990s and 2000s have resulted in new challenges for surface processing and surface modification processes. The latest advancements in plasma polymer chemistry have shown tremendous potential for the synthesis of reasonably well defined molecular structures with a high retention of functional groups. Some of the latest achievements and newest insights into the behaviour of such deposits in a liquid environment will be discussed, with a particular focus on bionanotechnological applications. Utilising novel approaches in surface and interface analysis, it will be shown that plasma polymers can be tailored to have considerable elasticity with reversible swelling characteristics, offering a three-dimensional interface for biomolecular immobilisaton procedures in a liquid environment.

Soft plasma treated surfaces: Tailoring of structure and properties for biomaterial applications

Fabricated super-hydrophobic film with potentiostatic electrolysis method on copper for corrosion protection

The polymerization of aniline under continuous and pulsed RF-plasma conditions is studied using the same plasma reactor. The effects of input power, on and off-times, frequency and duty cycle variations on the growth kinetics and on the chemical structure of the obtained layers are examined. The chemical structure of the films is characterized using Fourier Transform Infra-Red, X-ray photoelectron and UltraViolet–Visible spectroscopies. The thickness of the films is determined by profilometry. The results show a strong dependence of film chemistry and deposition rates on the discharge power and on-time. The film deposited by pulsed plasma grows mainly during the plasma-on period. Furthermore, this work shows that the retention of aromatic rings can be evaluated by Fourier transform infrared analysis whereas oxidation degree of plasma polyaniline can be determined by X-ray photoelectron and UV–Vis spectroscopies.

Film Chemistry Control and Growth Kinetics of Pulsed Plasma-Polymerized Aniline

XPS and NEXAFS spectroscopy results were used for chemical characterization of pulsed plasma deposited allyl alcohol films before and after exposure to ambient air. The influence of the composite plasma parameter, effective plasma power (P) to monomer flow rate (F) ratio on the spectroscopic results was investigated. From this data, information about the chemical character of the plasma polymerized films, such as retention of the hydroxyl groups in the deposited sample, the amount of long living radicals and branching and/or crosslinking was derived. A high degree of hydroxyl retention was observed, which, however, decreased along with the oxygen content of the film, as the P/F ratio increased. A trend in the extent of the oxygen loss according to the variation of the P/F ratio was deduced, which agrees with earlier ToF-SSIMS findings (Plasma Process. Polym. 2005, 2, 563).

Surface Analysis of Plasma‐Deposited Polymer Films, 6

In this study, we conducted the plasma polymerization of allylamine using radio frequency (RF) glow discharge with continuous wave (CW) in order to make an organic thin film with an amine functional group retained. Allylamine as a monomer was deposited on a glass in a bell-jar type plasma reactor and polymerized to plasma-polymerized allylamine (PPAa). The parameter to control the property of plasma polymer was input power at other conditions remaining constant. The chemical structure and the surface morphology of plasma-polymerized allylamine (PPAa) film were characterized by contact angle measurement, Attenuated Total Reflection Fourier Transform Infrared (ATR-FTIR), X-ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscopy (SEM). The property of PPAa film was highly dependent upon the plasma input power. The input power, which determines the plasma density, results in a property of PPAa thin film such as hydrophilicity, high retention of functionality of PPAa’s surface. Surface energy calculated by contact angle measurement indicated that increasing input power (from 30W to 90W) decreased the hydrophilic property of PPAa due to loss of amine functional group and high cross-linking. The increase of the energy causes the films to be harder. ATR-FTIR and XPS results showed that high input energy fragmented the amine group from monomer with increasing nitrogen atomic content and nitrile group. The high retention of amine groups seems mainly favored by low input power (<30 W). From thickness measurement usingα-stepper, the deposition rates were 0.43, 0.83, 1.11, 1.37 nm/s at 30, 50, 70, 90W, respectively. The change of surface morphology of plasma-polymerized thin films was investigated after soaking the PPAa film into ethanol. Due to weak adhesion with substrate and internal stress in plasma polymer film, the surface morphology of PPAa film revealed some irregular network pattern.

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Ying Guo

Papers

The characterization of structure-tailored plasma films deposited from the pulsed RF discharge