Plasma-assisted CVD of hydrogenated diamond-like carbon films by low-pressure dielectric barrier discharges

Abstract

Hydrogenated diamond-like carbon (DLC) films have been deposited on silicon substrates from dielectric barrier discharge (DBD) plasmas of CH4 at room temperature under a pressure of 0.4-4.0 Torr. The effects of discharge gas pressure (P), the applied peak voltage and the distance of the discharge gas spacing (d) on the film quality have been systematically investigated. The film hardness is mainly dependent on the Pd value and applied peak voltage. The best films of ϕ40-70 mm with Knoop hardness up to 20 GPa can be deposited at 30 kV peak voltage with a Pd value of about 2 Torr mm. The deposited films were characterized by scanning electron microscopy, Raman and FTIR spectroscopy. These analyses show that the deposited films are homogeneous hydrogenated amorphous carbon films with very smooth surfaces containing significant amounts of sp3 C-C bonding. The high-voltage and current waveform measurements of the discharge indicate that the low-pressure DBD consists of uniform (along the whole electrode) glow-like single breakdowns with half-widths of several microseconds. The DBD-induced deposition technique used in this work has many advantages, including the simplicity of the experimental set-up, large area deposition of DLC films and a lower consumption of feed gas and electric power.

Plasma enhanced CVD of fluorocarbon films by low-pressure dielectric barrier discharge

“…Low-pressure dielectric barrier discharge consists of spatially (along the electrode) uniform glow-like single breakdowns with pulse width of several microseconds [19,20]. The breakdown number per voltage period mainly depends on discharge pressure, distance of discharge gas spacing, and applied peak voltage.…”

“…The particles have a spherical form and their sizes are typically in the order of 0.1-1 μm. Recently, we have reported the attempt to deposit diamond-like carbon (DLC) films in low-pressure DBD plasmas of CH 4 [19,20]. The deposited DLC films show high film hardness (Knoop hardness; 20 GPa) and extremely low surface roughness (root mean square (rms) roughness: 0.11-0.27 nm).…”

Deposition of Large‐Area and Protective Diamond‐like Carbon Coatings on Glass Substrates by Low‐Pressure Dielectric Barrier Discharges

“…The averaged power of the discharge was calculated from the current and voltage waveforms over one cycle. [8] About 50 À 80 W was consumed under a CH 4 pressure of 30 -1000 Pa. Our Fourier transform infrared (FTIR) spectroscopy analysis clearly shows an absorption section in the range 2700 À 3100 cm À1 due to C-H stretch vibrations. [10] The absorption intensity was found to significantly increase with P, which indicates an increase in the hydrogen fraction, therefore resulting in a change in film structure from diamond-like to polymerlike.…”

“…[8] According to the well-known Paschen Law of gas discharge, while the Pd value decreases, the CH 4 breakdown voltage rises steeply at small Pd values (Pd < 1330 PaÁmm). [8] The increased breakdown voltage at small Pd values causes a large potential decline across the alternative and impulse DBD cathode sheath, and the low pressure causes an increase in the mean free path of collisions, so that the positive hydrocarbon ions can become more energetic through such a sheath, leading to the increase in film hardness. The averaged power of the discharge was calculated from the current and voltage waveforms over one cycle.…”

“…Largearea uniform (along the whole electrode) glow discharges are formed in low-pressure DBDs, which contribute to the formation of smooth surfaces of DLC films. [8,9] Variations of film nanohardness with P are shown in Figure 2. When P varies from 30 Pa to 200 Pa, film hardness dramatically decreases from 24.8 GPa to 3.2 GPa, then decreases slowly at P > 200 Pa.…”