C.A. Anderson

The surface oxidation of selected polymers using an atmospheric pressure air dielectric barrier discharge. Part I

Abstract In this paper, complementary to Part I published earlier herein, we report and discuss the results of surface treatment, using a dielectric barrier discharge (DBD), on various polymer films, which already contain intrinsically structurally bonded oxygen in their structures prior to treatment. Surface analysis and characterisation of the materials studied were performed using X-ray photoelectron spectroscopy (XPS), contact angle measurement and scanning electron microscopy (SEM) before and following the DBD processing described. The influence of the discharge parameters, i.e. the energy deposited by the discharge at the electrodes, the inter-electrode gap and the treatment time, are related to the changes in the surface characteristics found post-processing. Our results show that polar functional polymers carrying intrinsically bound oxygen can be further oxidised on short exposures to a random filamentary dielectric barrier discharge of relatively low power running in air at atmospheric pressure. The outermost layer of the surface is modified very rapidly and remarkably uniformly within fractions of a second of DBD exposure. Moreover, there appears to be a limit in the level of oxidation which can be induced by such DBD treatment, i.e. the maximum level attainable is ∼45 at.% O. These data thus become complementary to our first series of experiments, as the degree of modification of the surfaces, in terms of oxygen content, seems to depend in the present case both on the “polarity” of the samples prior to treatment and on the respective chemical structure of the polymers.

Control and mass selection of CnHm+ fragments in an inductively coupled pulsed plasma

We report on a method of selecting CnHm+ fragments using a pulsed inductively coupled plasma (ICP) driven by a rf supply and a pulse control unit providing user-defined on/off regimes. Langmuir probe and mass-energy spectrometric data show that the characteristics of the plasma can be monitored so demonstrating that hydrocarbon clusters of different C:H ratios and abundances can be generated preferentially by using appropriately chosen on/off regimes. Postdeposition x-ray photoelectron spectroscopy (XPS) analysis underlines clearly the influence of the deposition regimes, on the structure and composition of CxNy:H films grown via CnHm+ clusters generated using adamantane (C10H16) vapor in an argon/nitrogen mixture.

Time-Resolved Electron Energy Distribution Function Measurements in a Low-Frequency r.f. Glow Discharge

Langmuir-probe-based measurements of the time-resolved electron energy distribution function, EEDF, in a low-frequency (100 kHz) r.f. glow discharge are presented. These high-resolution measurements show the contrasting nature of the EEDF in a molecular (N2) and atomic (Ar) plasma. The effect of the interaction of the electrons with excited species in the plasma is observed and supports previously untested theoretical calculations. This interaction results in a highly non-Maxwellian EEDF for electron energies above a few eV and has strong implications for the understanding of the chemistry of plasma reactors, and the basic physics of r.f. glow discharges.

Time‐resolved plasma parameter measurements in a low‐frequency rf glow discharge

A new approach to the use of Langmuir probes in a rf driven plasma is presented. The periodic nature of the rf is utilized to overcome the distortion of the probe characteristics caused by averaging over many rf cycles. Time‐resolved measurements of the electron density, electron temperature, plasma potential, and floating potential in the negative portion of the rf cycle are obtained. The technique is used to characterize a low‐pressure 100‐kHz capacitively coupled rf argon discharge. The measured electron temperature is found to be approximately 0.5 eV.

PLASMA PARAMETERS OF A RADIO-FREQUENCY DISCHARGE

A low‐frequency (100 kHz) radio frequency discharge has been characterized by making time‐resolved measurements of the basic plasma parameters, including the electron energy‐distribution function. Measurements obtained when operating with H2, D2, and Ar are compared. Surprisingly low electron temperatures (∼0.2 eV) have been found in H2 and D2 discharges.A low‐frequency (100 kHz) radio frequency discharge has been characterized by making time‐resolved measurements of the basic plasma parameters, including the electron energy‐distribution function. Measurements obtained when operating with H2, D2, and Ar are compared. Surprisingly low electron temperatures (∼0.2 eV) have been found in H2 and D2 discharges.