The optical properties of nonideal plasmas within the electron concentration range 10 17 cm -3 < N e < 10 22 cm -3 are studied experimentally. According to these results, as well as to the data available in the literature, we obtain the experimental dependence of the ΔE (the difference between the atom ionization potential and the excitation potential of the upper level of the last observed emission or absorption line) value on the electron concentration within the range taken. The dependence is compared to the earlier obtained theoretical formulas. Recommendations on application of the experimental formula to determine the elec tron concentration in the external layers of the non ideal plasma at N e < 10 22 cm -3 are presented.
The results of experimental researched dealing with the bias voltage influence on the evolution of spectra emitted by plasma at the etching of gallium nitride in a plasma-chemical reactor with the controlled magnetic field are reported. At high bias voltage values above-250 V, there appear lines in the plasma emission spectra which belong to the excited atoms of the material of a working electrode. Under the influence of a negative potential, the active electrode is sputtered, and metal ions are redeposited onto its surface, which results in the lower etching rate. K e y w o r d s: bias voltage, plasma-chemical etching, sputtering, plasma-chemical reactor, radio-frequency discharge, optical spectroscopy.
Pulsed electric discharges in a liquid with the sufficiently wide range of energy contributions to them can generate diverging shock waves. А significant part of this energy is carried away by these waves from the center of the system to its periphery. At the same time, pulsed plasma-liquid systems limited by reflecting walls of both cylindrical and spherical geometry are insufficiently studied. A fundamental feature of such systems is the generation of a sequence of both diverging and converging (reflected) shock waves by a single pulse discharge. It was shown earlier that in a cylindrical plasma-liquid system with a height of the cylinder (h) comparable with the interelectrode distance (d), radius of the cylinder base R (at R >> h), when discharge current is increased, the ratio of the second diverging shock wave amplitude to the amplitude of the first diverging shock wave can be → 1. This leads to effective return of the energy carried away to the periphery back to the center of the system by converging shock waves. The collapse of the converging shock waves and initiated processes in the center of such plasma-fluid systems can be very interesting. The paper presents the results of experimental studies of pulsed cylindrical plasma-liquid system using both H 2 O and a mixture of H 2 O / D 2 O and pure D 2 O as a liquid. The energy-storage capacitor is charged by using a high voltage DC power supply (up to 70 kV).
The article presents the research results on the influence of the amount of oxygen in a mixture with sulfur hexafluoride on the rate and anisotropy of the silicon etching in the plasma-chemical reactor with the controlled magnetic field. The etching was performed under the pressure of (0,3—2,0)×10–3 Torr in the working chamber and the energy of chemically active ions of 50—80 eV. It was possible to etch the silicon to the depth of 100 µm with anisotropy 10, using a thick (0.4—1 µm) nickel mask.The obtained results make it evident, that maximums do not coincide for speed of etch and anisotropy. The maximum of etch rate is observed at oxygen maintained at 5%. While the maximum of anisotropy is observed at 10% oxygen. The authors discovered the influence of the magnetic field on the rate and anisotropy of etching. Etch rate of the silicon at the increase of the magnetic-field tension increases virtually twofold at other discharge parameters remaining unchanged. The anisotropy first increases, and then decreases sharply. Thus, the increase of the tension of magnetic field results in worsening of anisotropy. Thus, the process of deep plasma-chemical etching of silicon has been developed and optimized.
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