M. Moisan

X-RAY PHOTOELECTRON SPECTROSCOPY OF CARBON NITRIDE FILMS DEPOSITED BY GRAPHITE LASER ABLATION IN A NITROGEN POSTDISCHARGE

Carbon nitride thin films have been deposited on silicon substrates, using a newly developed surface wave discharge/pulsed laser deposition system. Nitrogen incorporation in the films is examined by x‐ray photoelectron spectroscopy (XPS). It shows that interaction between the laser ablated carbon species and nitrogen atoms from the surface‐wave N2 plasma enhances the incorporation of N in the carbon nitride layers, for example, up to 19% at a deposition pressure of 2 mTorr. Increasing the deposition temperature decreases nitrogen incorporation and changes the local chemical environment of nitrogen atoms.

Waveguide-based single and multiple nozzle plasma torches : the TIAGO concept

Various microwave-sustained, atmospheric-pressure plasma torches have been developed, investigated and applied over the last few decades. To avoid some of their shortcomings, we have designed a novel torch termed TIAGO (Torche a Injection Axiale sur Guide dOndes, in French). Its main advantages are simplicity, smooth impedance matching (low sensitivity to changes in operating conditions) and a short gas channel to prevent vapour condensation. Furthermore, it is possible to arrange TIAGOs in arrays to form a compact torch system which can be supplied, with equal distribution of power between plasma flames, from a single waveguide. This unique feature makes the new device particularly suitable when high gas throughputs or sequential processing are required. We describe the design, electrodynamic characteristics and experimental investigation of various torch arrangements based on the TIAGO principle, operated at 2.45 GHz with powers of a few hundred watts up to 2-3 kW per nozzle.

Influence of the field frequency on the nitrogen atom yield in the remote plasma of an high frequency discharge

An discharge sustained by an electromagnetic surface wave is investigated in order to develop an efficient nitrogen atom source. We take advantage of the flexibility of surface-wave discharges (SWDs) in terms of operating frequency to examine the influence of the field frequency (f = 13.56, 40.68, 440 and 2450 MHz) on the nitrogen atom concentration in the discharge spatial afterglow. The effects of absorbed power (up to 200 W), pressure p (1 to 8 Torr) and discharge tube diameter (4.5 and 15 mm) are also considered. The N atom concentration is determined through emission spectroscopy from the afterglow following validation by NO titration. We find that: (i) the N atom concentration increases with but saturates past a certain power, the value of which decreases with increasing f, (ii) the N atom saturation concentration is at 2450 MHz but only at ; (iii) the vibrational `temperature of the state in the discharge varies in the same way as the N atom concentration with respect to f and ; (iv) whatever f, saturation of the N atom concentration occurs at a threshold value -600 K of the molecule rotational `temperature in the discharge, suggesting that too high a gas temperature is the limiting factor of the N atom yield (v) the N atom concentration increases with increasing p and decreasing .

XPS and FTIR analysis of nitrogen incorporation in CNx thin films

Abstract CNX thin films have been deposited on Si(100) substrates using a new hybrid deposition system. This system combines excimer laser ablation of a graphite target and an atomic nitrogen source from a remote surface wave plasma. The films were characterized using X-ray photoelectron spectroscopy (XPS), elastic recoil detection (ERD) and Fourier transform infrared spectroscopy (FTIR). We found that the atomic nitrogen source enhances the incorporation of N in the CN x layers, for example, from N/C = 0.04 (plasma off) to 0.18 (plasma on). In addition, as nitrogen pressure in the deposition chamber is increased from 2mTorr to 1 Torr, the N/C ratio increases from 0.18 to 0.56. The XPS and FTIR spectra indicate that at deposition pressures above 100 mTorr, nitrogen incorporation is enhanced through the formation of hydrogenated carbon nitride groups, while at lower pressures, only simple and double CN bonds are detected.

Designing an efficient microwave-plasma source, independent of operating conditions, at atmospheric pressure

The surfaguide is a waveguide-based electromagnetic-surface-wave launcher that allows sustaining long plasma columns using microwaves. Its electrodynamic characteristics are examined experimentally and theoretically in the perspective of achieving an efficient plasma source without any need for impedance matching retuning as operating conditions are varied over a broad range. The plasma source design and its modelling using equivalent-circuit theory are described and a simple procedure is provided to determine the optimum dimensions of the surfaguide that maximize the transfer of microwave power to plasma. As an example, with an optimized surfaguide, the reflected power in an N2 discharge at atmospheric pressure stays below 3% for powers in the 2?6?kW range and gas flow rates in the 30?150?l?min?1 domain under varying concentrations (< 2%) of admixed gases such as SF6, O2 and argon.

The influence of atomic nitrogen flux on the composition of carbon nitride thin films

Carbon nitride (CNx) thin films have been deposited using a hybrid system combining pulsed laser deposition of graphite with the surface-wave discharge atomic nitrogen source (3% N2 in Ar). Using this system, an experiment is designed to study the influence of the atomic nitrogen flux on the composition of the CNx thin films at various laser intensities. The nitrogen percentage in the thin films is positively correlated with the N atom flux impinging on the substrate surface but it is counter-productive to use excessively high values of laser intensities on the graphite target. For a laser intensity of 6×108u2009W/cm2, the nitrogen percentage increases with the N atom flux and saturates at only about 16 at.u2009%. On the other hand, a maximum nitrogen percentage of 30 at.u2009% is obtained at the much lower laser intensity of 5×107u2009W/cm2.