In this paper, N-doped diamond-like carbon (DLC) films were deposited on silicon substrates by using helicon wave plasma chemical vapor deposition (HWP-CVD) with the Ar/CH 4 /N 2 mixed gas. The surface morphology, structural and mechanical properties of the N-doped DLC films were investigated in detail by scanning electron microscopy (SEM), x-ray photoelectron spectroscopy (XPS), Raman spectra, and atomic force microscopy (AFM). It can be observed from SEM images that surface morphology of the films become compact and uniform due to the incorporation of N. The maximum of the deposition rate of the films is 143 nm min −1 , which is related to the high plasma density. The results of XPS show that the N incorporates in the films and the C−C sp 3 bond content increases firstly up to the maximum (20%) at 10 sccm of N 2 flow rate, and then decreases with further increase in the N 2 flow rate. The maximum Young's modulus of the films is obtained by the doping of N and reaches 80 GPa at 10 sccm of N 2 flow rate, which is measured by AFM in the scanning probe microscope mode. Meanwhile, friction characteristic of the N-doped DLC films reaches a minimum value of 0.010.
An experimental research on multi-stable mode transitions and hysteresis loops in a high magnetic field helicon wave plasma source is conducted by adjusting matching network parameters. The correspondence relation between the electric circuit and plasma parameters is explored by measuring the plasma absorbed power, plasma electron density, and power transfer efficiency. The details of mode transitions are recorded by measuring the transmission coefficient to understand the feedback effects on the electric circuit from the plasma. Three discharge modes are observed in helicon discharge: the capacitively coupling mode (E mode), the inductively coupling mode (H mode), and the wave coupling mode (W mode). When the plasma absorbed power increases, the discharge mode directly jumps from the E mode to the W mode, while the discharge mode jumps in the order of W–H–E when the plasma absorbed power decreases. In such multi-stable systems, the plasma may be in different modes under the same set of circuit conditions. Hysteresis loops exist even when the dissipative power in the matching network is subtracted, which indicates that the main cause of hysteresis is nonlinearities inside the plasma.
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