Characterization of diamond-like carbon (DLC) thin films prepared by r.f. magnetron sputtering

An investigation by Optical Emission Spectroscopy (OES) was performed on RF (13.56 MHz) magnetron sputtering discharge used for Tungsten Carbide/Diamond-Like Carbon (W-C/DLC) multilayer thin film deposition. The multilayer deposition is obtained from a single tungsten (99.99%) and carbon (99.99%) binary compound target by gradual variation of methane (CH4) concentration in the argon/methane (ArCH4) gas mixture. The optical emission spectra supply information about the chemical species present in the plasma, and the densities of these species can be correlated with the structure and composition of the deposited layers. The electron temperature dependence on gas pressure and methane concentration in ArCH4 gas mixture by using some Ar, W and H emission line intensities, are studied in the center of the discharge. A simple model for the excitation process of the Ar, W and H atoms allows us to calculate the density of sputtered atoms in the plasma. At high methane concentrations for deposition of DLC layers, OES shows that besides the atomic hydrogen peaks Hα (656.3 nm) and Hβ (486.1 nm) of Balmer series, emission spectra are dominated by neutral CH species and the most intense peak in the spectra corresponds to CH-band head at 431.5 nm, which is supposed to be the precursor species in the diamond-like films. Owing to the transport regime of the W and C sputtered species across the discharge, the existence of correlation between the target composition, tungsten density in the plasma, multilayer thin film composition, and microstructure determined by XPS, XRD, IR and Raman spectroscopy are studied.

Optical emission spectroscopy study of r.f. magnetron sputtering discharge used for multilayers thin film deposition

Methane and hydrogen discharges has been studied at different discharge frequencies (35 kHz, 13.56 MHz, and 2.45 GHz) and feeding gas ratios (up to 100% of methane) during diamond and diamond‐like deposition by plasma chemical vapor deposition techniques. Optical emission spectroscopy shows that the intensity of atomic hydrogen line (Hα) is the highest at the microwave frequency (2.45 GHz). In addition, at this frequency and low methane concentrations (<7.5%) the emission of CH+ species is also detected, which has been associated to the presence of the diamond phase in the films. On the contrary, at the lower frequencies (35 kHz and 13.56 MHz), the emission spectra are dominated by neutral CH species that are supposed to be the precursor species in the diamond‐like films deposited at these frequencies.

Optical emission characterization of CH4+H2 discharges for diamond deposition

Optical emission diagnostics and film growth during microwave-plasma-assisted diamond CVD

Pulsing of a microwave discharge is a promising new technique to improve the control of the diamond deposition process. A small amount of argon (5% Ar) was added to the usual feed stock (0.5% methane in hydrogen) to act as an actinometer. Plasma emission was observed during the pulse on-times for pulse repetition rates from 50 Hz to 10 kHz by time-resolved optical spectroscopy. Determined relaxation time constants for atomic hydrogen are on the order of 1 ms. Thus, the atomic hydrogen concentrations do not vary very much at a pulse repetition rate of 20 kHz, whereas at 50 Hz the radical concentrations vary between a saturation value and zero. The saturation value of atomic hydrogen increases with increasing peak power, but mean values are generally lower as in the continuous wave mode with the same average power and decrease with decreasing duty cycles and pulse repetition rates. The results are consistent with deposition experiments.

Atomic hydrogen concentrations in pulsed microwave discharges used for diamond synthesis

Low pressure microwave plasmas are of growing interest for plasmachemical applications since they have special and in some cases unique advantages with respect to other plasma excitation methods. Subject of this paper are spatially resolved measurements of the optical emission of a special planar microwave plasma source utilized to investigate different plasmachemical processes. The optical emission spectroscopy (OES) is used as a tool to get information concerning the spatially distribution of reactive atom and molecule concentration by actinometry and concerning the neutral gas temperature by measurements of Doppler line broadening. The results refer to hydrocarbon containing hydrogen plasmas which gas pressures above 100 Pa. Surprisingly measurements confirm an earlier developed simplified two layer model consisting of a preferentially physically active plasma layer near the microwave window followed by a preferentially chemically active decaying region. They give evidence that this model is more adequate to the real physical situation as assumed until now.

Optical emission diagnostic of a low pressure planar microwave discharge for plasmachemical deposition

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Optical emission diagnostic of a low pressure planar microwave discharge for plasmachemical deposition