In order to characterize a nonequilibrium molecular plasma from the point of view of translational, vibrational and rotational degrees of freedom and their interaction, the characteristic temperatures of such a plasma were measured in an ICP rf reactor. Both pure nitrogen and argon–nitrogen mixture plasmas were examined for this purpose.The experimental results of rotational (Tr), vibrational (Tv) and electron (Te) temperatures are presented. Vibrational and rotational temperatures were measured as a function of nitrogen content for both E and H modes of ICP discharge using a power range of 45–200 W and pressure range of 2.6–13.3 Pa. Additionally, the pressure dependence of electron temperature in a pure nitrogen discharge was studied. Results show that rotational temperature is ≈370 K for E mode and ≈470 K for H mode and almost does not depend on either the applied rf power or the nitrogen content in the discharge. Vibrational temperature groups in the range 5000–12 000 K increase with applied rf power and constantly decay with an increase of nitrogen content. The measured values and behaviour of electron temperature are comparable with those for the positive column of the dc glow discharge. The results also prove that these three temperatures obey the classical inequality Te > Tv > Tr, as well as clarifying the differences in both vibrational and rotational temperature for different modes of the ICP discharge.
The need for 2D vertical graphene nanosheets (VGNs) is driven by its great potential in diverse energy, electronics, and sensor applications, wherein many cases a low-temperature synthesis is preferred due to requirements of the manufacturing process. Unfortunately, most of today's known methods, including plasma, require either relatively high temperatures or high plasma powers. Herein, we report on a controllable synthesis of VGNs at a pushed down lowtemperature boundary for synthesis, the low temperatures (450 o C) and low plasma powers (30 W) using capacitively coupled plasma (CCP) driven by radio-frequency power at 13.56 MHz. The strategies implemented also include unrevealing the role of Nickel (Ni) catalyst thin film on the substrates (Si/Al). It was found that the Ni catalyst on Si/Al initiates the nucleation/growth of VGNs at 450 °C in comparison to the substrates without Ni catalyst.With increasing temperature, the graphene nanosheets become bigger in size, well-structured and well separated. The role of Ni catalysts is hence to boost the growth rate, density, and quality of the growing VGNs. Furthermore, this CCP method can be used to synthesize VGNs at the lowest temperatures possible so far on a variety of substrates and provide new opportunities in the practical application of VGNs.
A confocal Fabry–Perot interferometer was utilized to study Ar–Ti, Ar–Cu and Ar–Cr dc magnetron discharges during sputtering of the corresponding metallic targets. Doppler broadening of Ar and Ti emission lines was measured in the wide range of Ar pressures and at different powers applied to the discharge. Spatial characterization of Ar and Ti line broadening through the discharge volume was also performed. Corresponding temperatures of Ar and thermalized Ti atoms were determined by Doppler broadening of the corresponding emission lines. Results show that the Ar temperature depends mainly on the working pressure in the reactor and it was found to be on average in the range 700–1300 K for the working pressure range 2–240 mTorr. The temperature of Ti was found to be about 600–800 K; it slightly increases with increasing applied power and does not depend on the working pressure in the reactor. Ar temperature measurements were verified by adding nitrogen in the discharge and by the measuring of the N2(C, v′ = 0 − B, v″ = 2) vibrational band shape.
Thermal properties of two types of porous silicon are studied using the pulsed-photothermal method (PPT). This method is based on a pulsed-laser source in the nanosecond regime. A 1D analytical model is coupled with the PPT technique in order to determinate thermal properties of the studied samples (thermal conductivity and volumetric heat capacity). At rst, a bulk single crystal silicon sample and a titanium thin lm deposited on a single crystal silicon substrate are studied in order to validate the PPT method. Porous silicon samples are elaborated with two dierent techniques, the sintering technique for macroporous silicon and electrochemical etching method for mesoporous silicon. Metallic thin lms are deposited on these two substrates by magnetron sputtering. Finally, the thermal properties of macroporous (30% of porosity and pores diameter between 100 nm and 1000 nm) and mesoporous silicon (30% and 15% of porosity and pores diameter between 5 nm and 10 nm) are determined in this work and it is found that thermal conductivity of macroporous (73 W.m-1 .K-1) and mesoporous (between 80 and 50 W.m-1 .K-1) silicon is two times lower than the single crystal silicon (140 W.m-1 .K-1).
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