This multi‐centre investigation explores the variability that results from using the power/flow rate ratio (W/F) to describe plasma treatment and plasma polymerization processes. Results from fourteen reactors of different design and spread across ten laboratories, showed that the chemistry of the treated and deposited polymer/plasma polymer films is highly variable between reactor systems, and that there was no clear pattern linking these variations to other properties of the reactor systems (e.g. pressure, volume, electrode configuration). Although W/FM provides a useful rule‐of‐thumb for process optimization within a single system, it does not provide sufficient information to enable the same plasma polymer to be produced on a different system.

A discharge of nitrogen-hydrogen mixture by 50 Hz pulsed dc in the presence of active screen cage is investigated by optical emission spectroscopy (OES). The aim is to identify the parameters (mixture ratio, filling pressure and current density) that may lead to high concentration of active species (N 2 , N 2 + and N). The maximum concentration in this experiment is found with 40% H 2 -60% N 2 , at filling pressure of 3 mbar with current density of 5 mAcm -2 . High carbon steel samples are nitrided for 1-4 hours at 500°C and the treated samples are characterized by X-ray diffraction (XRD), Raman spectroscopy and Vicker's micro-hardness testing. The XRD spectra show different phases of nitrides (Fe 2-3 N, FeN, CrN) along with iron oxides. The Raman spectra confirm the formation of α-β (C 3 N 4 ). The surface hardness is found to increase up to six times for 2 hour treatment.

In this paper, E-H mode transition in magnetic-pole-enhanced inductively coupled neon-argon mixture plasma is investigated in terms of fundamental plasma parameters as a function of argon fraction (0%-100%), operating pressure (1 Pa, 5 Pa, 10 Pa and 50 Pa), and radio frequency (RF) power (5-100 W). An RF compensated Langmuir probe and optical emission spectroscopy are used for the diagnostics of the plasma under study. Owing to the lower ionization potential and higher collision cross-section of argon, when its fraction in the discharge is increased, the mode transition occurs at lower RF power; i.e. for 0% argon and 1 Pa pressure, the threshold power of the E-H mode transition is 65 W, which reduces to 20 W when the argon fraction is increased. The electron density increases with the argon fraction at a fixed pressure, whereas the temperature decreases with the argon fraction. The relaxation length of the low-energy electrons increases, and decreases for high-energy electrons with argon fraction, due to the Ramseur effect. However, the relaxation length of both groups of electrons decreases with pressure due to reduction in the mean free path. The electron energy probability function (EEPF) profiles are non-Maxwellian in E-mode, attributable to the nonlocal electron kinetics in this mode; however, they evolve to Maxwellian distribution when the discharge transforms to H-mode due to lower electron temperature and higher electron density in H-mode. The tail of the measured EEPFs is found to deplete in both E-and H-modes when the argon fraction in the discharge is increased, because argon has a much lower excitation potential (11.5 eV) than neon (16.6 eV).

No abstract