Smooth polymer surfaces can be generated by VUV laser ablation at 157 nm. This has been demonstrated for poly-methyl-metacrylate (PMMA) by atomic force microscopy (AFM) analysis of laser-exposed surfaces. At excimer laser fluences below 30 mJ/cm2 the mean roughness (Ra) remains below 10 nm for both single and 10 shot exposures.

A detailed characterization of the surface nano-morphology distribution carried out by the “power spectral density” (PSD) analysis, shows that the surface is smoothened by the VUV laser for lateral scales smaller than 20 μm.

Coatings of biologically active molecules on synthetic ”bulk“materials are of much interest for biomedical applications since they can in principle elicit specific, predictable. controlled responses of the host environment to an implanted device. However, issues such as shelf life. storage conditions, biological safety, and enzymatic attack in the biological environment must be considered; synthetic proteins may offer advantages. In this study we investigated the covalent immobilization onto polymeric materials of synthetic proteins which possess some properties that mimic those of the natural protein collagen, particularly the ability to form triple helical structures, and thus may provide similar bio-responses while avoiding enzymatic degradation. In order to perform immobilization of these collagen-like molecules (CLMs) under mild reaction conditions, the bulk materials are first equipped with suitable surface groups using rf plasma methods. Plasma polymer interlayers offer advantages as versatile reactive platforms for the immobilization of proteins and other biologically active molecules. Application of a thin plasma polymer coating from an aldehyde monomer is particularly suitable as it enables direct immobilization of CLMs by reaction with their terminal amine groups, using reductive amination chemistry. An alternative route is via plasma polymer layers that contain carboxylic acid groups and using carbodiimnide chemistry. A third route makes use of alkylamme plasma polymer interlayers, which are less process sensitive than aldehyde and acid plasma coatings. A layer of poly-carboxylic acid compounds such as carboxylic acid terminated PAMAM-starburst dendrimers or carboxymethylated dextran is then attached by carbodiimide chemistry onto the amine plasma layer. Amine-terminated CLMs can then be immobilized onto the poly-carboxylic acid layer. Surface analytical methods have been used to characterize the immobilization steps and to assess the surface coverage. Initial cell attachment and growth assays indicate that the biological performance of the CLMs depends on their amino acid sequence.

A cylindrically-configured plasma treatment system in Radio Frequency Glow Discharges fed with ammonia was used to modify the internal surface of ePTFE arterial prostheses. The effects of RF-power on the surface chemical composition were characterized by XPS. Results show that the treatment at 20 W, for 250 seconds and under an ammonia pressure of 300 mtorr yielded a good compromise between ablation and substitution phenomena on the surface. With this treatment, fluorine content was decreased, while up to 20 % of the surface atoms were substituted by nitrogen.

Low-pressure plasmas are now being used for sterilization at ambient temperature. In this work, we have studied the possible mechanism of spore destruction by plasma, and compare it with etching of synthetic polymers. Bacillus subtilis spores were inoculated at the bottom of special glass vials and subjected to different plasma gas compositions, all known to etch polymers. The mortality rate of spores was found to vary with gas composition, between less than a 2 log decrease in 8 minutes for a pure oxygen plasma, to a 6 log decrease with 02CF4 mixture. Examination by scanning electron microscopy (SEM) showed that spores were significantly etched after 30 minutes of plasma exposure, but not completely. We speculate about their etch resistance, compared with that of synthetic polymers, on the basis of their morphology and their complex coating structure.

Human keratinocytes have been cultured on plasma co-polymers (PCPs), self assembled monolayers (SAMs), tissue culture poly(styrene) (TCPS) and collagen I. The degree of keratinocyte attachment was measured over 24 hours and cell proliferation and growth monitored over 7 days using optical microscopy and DNA concentrations. Cell attachment and proliferation and growth on the PCP surfaces were compared with 2 self assembled monolayer (SAM) systems. PCP surfaces containing carboxylic acid functionalities promoted keratinocyte attachment, with optimum attachment levels seen on surfaces containing less than 5% acid groups. The level of attachment on these surfaces was comparable to that seen on collagen I, a preferred substratum for the culturing of keratinocytes. After several days in culture the cells were well attached and proliferative. Keratinocytes attached well to acidterminated SAMs but attached poorly to methyl-terminated SAMs.

Amine-functionalized thin films were prepared by plasma induced deposition of allylamine. Radio frequency (rf) plasma polymerization was carried out under both continuous wave (CW) and pulsed plasma conditions to control the film chemistry, all other process variables being held constant. Using plasma polymerized films for subsequent grafting reactions or for direct biomedical applications usually involves exposure of the films to a solvent environment. It was the major focus of this work to investigate both the chemical and physical effects of solvents on plasma polymerized allylamine films. Film properties were determined using Fourier Transform Infrared Spectroscopy (FTIR), X-ray Photoelectron Spectroscopy (XPS), Waveguide Mode Spectroscopy (WaMS) and Surface Plasmon Spectroscopy (SPS). WaMS provided an ideal opportunity to study the complex swelling and drying behaviour of these films by allowing a simultaneous study of the changes in film thickness and refractive index. Although the amine groups of the monomer were increasingly retained in the films as the RF duty cycle was lowered, a larger amount of oxygen was also found to be incorporated upon exposure to air. Extraction in ethanol led to a decrease in film thickness, especially for the films produced at low duty cycles, but appeared to have little effect on the film composition, as measured by XPS and FTIR.

Inner pores of porous PTFE was modified photochemically by using ArF excimer laser for improvement of water permeability. In this study, two modification methods are described. One is using ethanol solution, and another is H20 vapor as a reaction gas. These reaction sources were employed for modification of inner pores. In the case of using ethanol solution, the modified sample indicates both hydrophilication and oleophilication. On the contrary, the hydrophilic groups are substituted into the inner pore with H20 vapor. The hydrophilication of modified samples were evaluated by the measurement of contact angle with water and water permeability. The substituted OH radicals were inspected by ATR-FTIR measurement.

Plasma treatment and deposition techniques have been used to facilitate the covalent attachment of DNA to polymer surfaces. The variety of surface functional groups that can be created by plasma techniques enables different chemical conjugation routes to be explored. For example, a phosphodiester linkage can be used for surfaces with hydroxyl groups. Likewise, a carboxyamide linkage can be used for surfaces with carboxyl or amine groups. The primary application of the engineered materials has been the hybridization-based separation of multiplexed DNA sequencing products. Traditionally, sequencing reactions are performed individually on single templates. Multiplex sequencing offers reagent and time savings by permitting multiple sequencing reactions on single or multiple templates. The method developed uses recoverable DNA sequencing primers with additional “capture sequences” attached to the 5' end. The capture sequences are designed to be complementary to “binding sequences” covalently attached to the plasma-treated polymer supports. When a solution of the extended recoverable primers is exposed to a polymer support, primers with complementary capture sequences hybridize to the immobilized binding sequences. Contacting a multiplexed sample with a series of solid supports (each having a different binding sequence) selectively removes each set of sequencing products from the mixture. Washing each solid support, followed by releasing the hybridized DNA, results in isolated and purified sequencing products that are amenable to analysis by gel or capillary electrophoresis.

FTIR spectroscopy has been applied to a radio-frequency discharge in hexamethyldisiloxane (HMDSO) diluted with oxygen and helium, as typically used for industrial SiOx, deposition. By measuring the infrared absorption of the HMDSO molecule, the gas consumption during processing can be monitored, allowing process optimization. Additional information on various infrared active radicals formed within the plasma, such as CO, CO2 and aldehydes, helps to elucidate the plasma chemistry in HMDSO plasmas. Besides information on the formation of gaseous components in the plasma, infrared transmission spectra give at the same time important data on the nature of the particle contamination.

An original method is developed to investigate vibrational properties of thin films using infrared (IR) ellipsometry. The procedure is based on in-situ measurements as a function of deposition time. Out of absorption bands, the IR refractive index can be determined and related both to film density and oscillator strengths of electronic transitions. Thanks to band decomposition performed for a given film at different thicknesses, line frequency, band width and intensity of each vibration can be precisely determined, even in case of band overlapping or low IR oscillator strengths. As an illustration, C-H bonding of 1000 Å-thick plasmadeposited polymerlike hydrogenated carbon (PLC) films has been studied. Analysis of the interface between highly saturated PLC films and crystalline silicon reveals the formation of a 20 Å interlayer. Bulk analysis evidences weak vibrations located at 1405 and 1440 cm−1 which had not been observed so far and which are related to π bonds. By combining elastic recoil detection measurements and IR analysis, effective charges of sp3 CHn groups have been calculated. For methyl and methylene groups, these charges are similar to those of hydrocarbon compounds. As far as the sp3 CHn group is concerned, a strong decrease of the effective charge versus film density is evidenced and attributed to the formation of distorted weakly hydrogenated regions induced by ion bombardment.

Film chemistry control issues, as well as key properties of polymers synthesized under pulsed plasma conditions, are discussed. Distinctions between pulsed and continuous wave plasmas are examined, particularly as they relate to differences in the energy efficiency of film formation rates and to the range of available power inputs. Film stabilities, with special reference to polymers formed under very low power input conditions, are considered. Finally, selected applications involving use of the inherently high film chemistry controllability made available by the variable duty cycle pulsed plasma technique are described.

Hydrogenated and nitrogenated amorphous carbon films, a-C:H and a-C:H:N, were elaborated by Plasma Enhanced Chemical Vapor Deposition (PECVD) in a dual Electron Cyclotron Resonance - Radio Frequency (ECR-RF) discharge of methane and/or nitrogen. The use of a low pressure plasma (2.6 mTorr) and a capacitive coupling of the substrate, separately from the electrical power of the ECR source, leads to reach new conditions of preparation. The ions and radicals fluxes, Φi and ΦR, determined respectively from the Langmuir probe measurements and the Mass Spectrometry (MS) give a ratio ΦR/Φi of order of 20. The CH3 radicals were identified and their concentration was measured from the technique of threshold ionization. It is shown that, even at low pressure, numerous ion-molecule reactions take place in the gas phase which explain the formation of major ions CH5+. and C2H5+. The plasma-surface interaction is studied by in-situ kinetic ellipsometry and by ex-situ X-ray Photoelectron Spectroscopy (XPS) measurements of deposited films. The role of the impact energy of ions, during the growth of films, is studied by Ultra-Violet-Visible spectroscopic ellipsometry. A new technique of deposition by alternating sequences of «C H4 deposition - treatment by N2, plasma » is described in this paper. The resulted a-C:H:N films are compared to those elaborated from CH4-N2 plasmas. The aim of the discussion on the presented results is to better understand the mechanism of the growth of amorphous carbon films by PECVD.

Diamond is a metastable phase, while graphite is a stable phase in low pressure equilibrium phase diagrams of carbon. However, diamond with saturated structure of π bonds is more stable than graphite with unsaturated structure of n bonds during the existence of activated particles generated by plasma. That provides an excellent explanation for the plasma and other activated CVD diamond growth under low pressure taking place with simultaneous graphite etching.

The interest in incoherent sources for wavelength selective photochemistry has increased lately, but little is still known about the behavior of polymers when exposed to far UV and vacuum UV (VUV) radiation, for example that emitted from low-pressure plasmas. In order to study VUV-UV effects on several polymers (polyethylene - PE, polystyrene - PS, hexatriacontane - HTC, polymethylmethacrylate - PMMA and polycarbonate - PC), we used the wellcharacterized emissions from hydrogen and hydrogen/argon mixture plasmas as light sources. Mass changes were measured in-situ using a quartz crystal microbalance (QCM); irradiated samples were analyzed ex-situ by XPS, spectroscopic ellipsometry, and AFM.

Plasma treatments in power modulated NH3 RF glow discharges have been performed for modifying the surface of polyethylene (PE). Time Resolved Optical Emission Spectroscopy (TR-OES) has been utilized for monitoring the emission of active species during the modulation period of the discharge, Electron Spectroscopy for Chemical Analysis (ESCA) has been used for studying the surface composition of PE before and after the derivatization of plasmagrafted -NH2 groups. We present our preliminary results here, which show how modulated NH3 plasmas can effectively improve the grafting selectivity of -NH2 respect to all other N-containing groups.

Recent advances in atomic force microscopy (AFM) allow one to perform complex analysis of materials surfaces and near-surface regions with a nanometer scale resolution; this includes the imaging of surface topography and the measurements of stiffness, elasticity, hardness and nano-tribological characteristics. Understanding of the complex AFM response is still in its early stage, and it frequently requires the use of multiple complementary techniques. In the present work we have applied AFM for the study of the surface and nearsurface mechanical properties of plasma-treated polycarbonate. The results from AFM analysis, such as the stiffness and the relative Young modulus, were compared with the hardness values obtained by depth-sensing indentation and by the micro-scratch technique. The characteristics of the observed hardened surface layer are discussed with respect to the role of the “interphase” in adhesion en1hancement of plasma-deposited films on polymers.

Non stoichiometric thin tin oxide films have been deposited using the PACVD technique in a RF glow discharge diode or triode reactor at low pressure (15 Pa) and at low temperature (25–100°C). The films deposited in the diode configuration were amorphous and presented a high transmittance (95%) in the visible region. The conductivity of the films deposited in the triode configuration can be increased by 4 orders of magnitude with respect to the ones deposited in the diode configuration (from 0.01 to 100 ω−1 cm−1) with a decrease of the gap energy (from 3.5 to 2.5 eV). This increase of the conductivity was accompanied by a slight decrease of the grain size (95 to 45 nm). The very small grain size of the deposited films makes them excellent candidates for gas sensors due to their good sensitivities to different molecules such as ethanol and propane.

Plasma graft polymerized styrene was formed by a reactor with a parallel plate electrode system on a pulsed plasma polymerized styrene film in a monomer vapor, where the pulsed plasma polymerization was performed by a low frequency 100%pulse modulation of 13.56 MHz power source in styrene vapor. The pulse duration was varied in the range of 0.01∼1 sec and ON time/duty cycle ratio was 1/10 and 1/20. The processes were monitored by a quartz crystal microbalance. The initial stage of plasma polymerization and grafting are discussed in this paper. Also sub 100 nm lines and spaces pattern on the resist delineated by an electron-beam pattering machine was developed by hexane.

We describe a new approach to deposition of Parylene N thin films. It utilizes a small scale, sonic speed, Jet Vapor DepositionTM (JVDTM) process technology in place of the conventional larger scale, slow flow, Gorham apparatus. It employs a simple but powerful strategy to promote radical polymerization: exposure of the growing film, during deposition, to a high flux of atomic hydrogen. We believe that H atoms have two effects: they clean oxygen from the substrate, and they promote crosslinking in the Parylene film by abstraction of H atoms from the Parylene ring or side groups. With “H atom assisted JVD” Parylene N deposits and adheres even on warm substrates; it has reduced index of refraction and dielectric constant.