Abstract
Recently, the use of Ne as a processing gas has been shown to increase the ionization degree of carbon in High Power Impulse Magnetron Sputtering (HiPIMS) plasmas. In this work, time-resolved measurements of the substrate’s current density were carried out in order to study the time evolution of the ionic species arriving at the growing film. The addition of Ne to the plasma resulted in a steep increase of the sp3/sp2 ratio in the films once the Ne contents in the processing atmosphere exceeded 26%. Increasing the Ne content is shown to increase both the total number of C ions generated in the plasmas and the ratio of C/gaseous ions. The time-resolved substrate ion current density was used to evaluate the possibility of substrate biasing synchronizing with the discharge pulses in the HiPIMS process. It is shown that in pure Ar plasmas, substrate biasing should be confined to the time interval between 25 and 40 µs after the pulse starts, in order to maximize the C+/Ar+ ratio bombarding the substrate and minimize the formation of film stresses. However, Ne addition to the processing gas shortens the traveling time of the carbon species towards the substrate, reducing the separation between the gaseous and carbon ion arrival times.
Highlights
The physical vapor deposition of hard Diamond-like Carbon (DLC) films, such as tetragonal amorphous films, relies on the subplantation of C ions into the subsurface region of the growing film, in order to promote the formation of sp3 sites
This conclusion agrees well with the results reported by Schmidt et al [35] and of the out Energy Resolved Mass Spectroscopy (ERMS) in High Power Impulse Magnetron Sputtering (HiPIMS) plasmas obtained from a C target in pure al.Ar plasmas in plasma pure Arwell using carbon chromium targets
The shoulder observed in the ion saturation current (ISC) obtained in this work between t = 25 and 35 μs is attributed to the arrival of C+ ions at the probe and the pronounced decrease of ISCs in this time interval corresponds to the extinction of the sputtering process at the target
Summary
The physical vapor deposition of hard Diamond-like Carbon (DLC) films, such as tetragonal amorphous films (ta-C), relies on the subplantation of C ions into the subsurface region of the growing film, in order to promote the formation of sp sites. This process is implemented in ionized deposition technologies, such as filtered cathodic arc deposition (FCA) and pulsed laser deposition (PLD), as carbon ions are naturally produced [1,2]. In DCMS, the vast majority of energetic species impinging on the growing film are Ar ions extracted from the plasma by substrate biasing, causing additional stresses without significantly contributing to sp formation
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