Principles for designing sputtering-based strategies for high-rate synthesis of dense and hard hydrogenated amorphous carbon thin films

Abstract

Principles for designing sputtering-based strategies for high-rate synthesis of dense and hard hydrogenated amorphous carbon thin films, Diamond and related materials, 2014. 44, pp.117-122. http AbstractIn the present study we contribute to the understanding that is required for designing sputtering-based routes for high rate synthesis of hard and dense hydrogenated amorphous carbon (a-C:H) films. We compile and implement a strategy for synthesis of a-C:H thin films that entails coupling a hydrocarbon gas (acetylene) with high density discharges generated by the superposition of high power impulse magnetron sputtering (HiPIMS) and direct current magnetron sputtering (DCMS). Appropriate control of discharge density (by tuning HiPIMS/DCMS power ratio), gas phase composition and energy of the ionized depositing species leads to a route capable of providing ten-fold increase in the deposition rate of a-C film growth compared to HiPIMS Ar discharge (Aijaz et al. Diamond and Related Materials 23 (2012) 1). This is achieved without significant incorporation of H (< 10 %) and with relatively high hardness (> 25 GPa) and mass density (~2.32 g/cm 3 ). Using our experimental data together with Monte-Carlo computer simulations and data from the literature we suggest that: (i) dissociative reactions triggered by the interactions of energetic discharge electrons with hydrocarbon gas molecules is an important additional (to the sputtering cathode) source of film forming species and (ii) film microstructure and film hydrogen content are primarily controlled by interactions of energetic plasma species with surface and sub-surface layers of the growing film.

Synthesis of hydrogenated diamondlike carbon thin films using neon–acetylene based high power impulse magnetron sputtering discharges

“…22 The presence of C 2 H 2 introduced additional interactions of plasma electrons leading to dissociation and ionization of C 2 H 2 along with the interactions of plasma electrons with the buffer gas and sputtered C. This process facilitated an increased amount of deposited C (tenfold increased deposition rates), and the resulting films exhibited hardness higher than 25 GPa and mass densities in the order of 2.32 g/cm 3 . The promising prospect of the resulting DLC:H films was their low H content which did not exceed 10 at.…”

“…In order to elucidate the effect of admixing Ne in Ar and Ar/C 2 H 2 atmosphere, we also compare the resulting film properties with our previous studies. 21,22 The plasma properties are investigated by measuring electron energy distribution functions (EEDF) (thereby determining electron temperature and electron density from EEDF), which, contrary to our expectations, shows that higher electron temperatures are obtained when the process gas (Ne þ Ar) contains C 2 H 2 . The plasma properties are also investigated by studying the behavior of the discharge current under different gas phase composition.…”

“…5 and 6, we compare the properties of the films synthesized using Ne þ Ar/C 2 H 2 process (only from 2 Pa) with the films synthesized in our earlier works under similar process conditions: films synthesized using Ar/ C 2 H 2 , pure Ar and Ne þ Ar based HiPIMS discharges. 21,22 Figure 5 shows mass densities of the films resulting from different processes. For the discharge processes operated without C 2 H 2 , the mass densities are higher as compared to those operated using 2% C 2 H 2 .…”

Manufacturing and Characterization of a Carbon-Based Amorphous (a-CNX) Coating Material

“…Nonetheless, Aijaz et al [23] demonstrated that hydrogenated amorphous carbon thin film can be synthesized with low hydrogen quantity in Ar/ C 2 H 2 discharge. They argued that the high plasma density of superimposed HiPIMS and dcMS facilitates to reduce the hydrogen quantity in the deposited film through chemical sputtering of growing film surface, and thereby hardness and mass density of the film are increased.…”

“…The mechanical and tribological properties of carbonbased coatings can be tailored by controlling the energy and flux of the depositing ions, radicals and molecules to substrates [17,18] in various high plasma density discharge-based deposition processes such as cathodic vacuum arc (CVA) [19], pulsed laser deposition (PLD) [20], inductively coupled plasma (ICP) [21], plasma-enhanced chemical vapor deposition (PECVD) coupled with electron cyclotron resonance [22], and magnetron sputtering [23]. Comparing to direct current magnetron sputtering (dcMS) and radio frequency magnetron sputtering (RFMS), highpower impulse magnetron sputtering (HiPIMS) process is known to generate higher plasma density (10 19 m -3 comparing to 10 17 m -3 in dcMS) [24,25].…”