Tailored electrochemical behavior of ta-C film by glancing angle deposition

A review of plasma-assisted deposition methods for amorphous carbon thin and ultrathin films with a focus on the cathodic vacuum arc technique

“…In addition, higher film deposition rates were instigated with the deposition angle decreasing from 70 to 0° (normal incidence). A significant decrease of the internal stresses of a-C films deposited by FCVA was reported for relatively high incidence angles attained by substrate tilting, in conjunction with the decrease of the sp 3 content and hardness [117,241]. These observations can be explained by delving into the dependence of the evolution of the carbon film's structure on the ion incidence angle.…”

“…Particularly, improvements in duct instrumentation further enhanced the particle filtration efficiency, which was dictated by growing demands for high-quality films of thickness only a few nanometers. Hence, several innovative duct-filter designs were introduced to augment the level of particle filtration, such as 45° filters [71] also known as knee filters, 45° double-bend filters [79,117], filters with different rectangular cross sections [74,75], segmented filters [73,78], single 90° bend filters [126,201,203], in-plane S-shaped filters [72], twist filters [204], and second-generation planar filters with two 90° bends twisted by 45° [70]. However, despite these new filtering designs, particle reflection from the duct walls persisted even with ribbed duct structures, leading to the growth of films with embedded particles.…”

“…Characteristic features and design intricacies of different CVA systems are summarized in Table 1. Macroparticle filter/duct design Primitive designs exploring initial curvilinear plasma physics [68,199] Annular cathode integrated with a straight duct [200] Direct line-of-sight deposition with no macroparticle filter [65] Duct walls Ribbed duct [66] No walls (open filter) [65,70] Bent filters (angle of bend) 45° [71,79,117] 90° [17,69,126,140,201,203] Rectangular cross-sectioned duct [74,75] In-plane S-shape configuration [72] Out-of-plane configuration S-shaped [54,64] Double bend [76,77] Twist filter [204] CVA Magnetic field stabilization Direct line-of-sight deposition without magnetic coils [65] Curved solenoid coil [65] Strategically located solenoid coils at entrance and exit [69] Cusp configuration magnetic field near the cathode for stabilizing the arc current [14,53,54,81,82]…”

“…Since this diffusion process relaxes the film stress, it inhibits the development of a compressive mechanical environment, which is conducive to sp 3 hybridization. Indeed, 60% [125,205] 50% [186] Pulse frequency of substrate biasing 600-1000 Hz [242] 25 kHz [54] Substrate bias voltage for optimized tribo-thermo-mechanical properties − 120 V − 100 to − 150 V [15,195] Substrate-plasma beam inclination for optimized tribo-thermo-mechanical properties 45° [97] 59-77° [240] 10° [53,82,206] 0° (normal incidence) [117,239,241] Substrate-plasma beam inclination for minimal internal residual stress 60° [97,241] 75° [117] Species selective biasing applied to the substrate Applied via a computer controlled bias amplifier [57,61] Software controlled (LabView) [56,59,60] Working pressure ~ 5 × 10 a strong transition to sp 2 -dominated a-C film growth has been found for substrate temperatures above 200 °C [115], consistent with simulation results revealing film amorphization at 200 °C [250]. Despite valuable insight into the thermal stability of carbon films at elevated temperatures and inert environments derived from earlier studies, profound changes in the film microstructure may be encountered in oxidizing atmospheres.…”

Thermal stability and diffusion characteristics of ultrathin amorphous carbon films grown on crystalline and nitrogenated silicon substrates by filtered cathodic vacuum arc deposition

“…In concurrence with the synthesis of ultrathin a -C films, specialized characterization methods were also developed in response to high demands for imaging techniques that can elucidate the composition and structure of films with thicknesses in the low nanometer range. The ion incidence angle, substrate bias voltage, and duty cycle of pulse biasing strongly affect the thickness, composition, and structure of a -C films grown by the FCVA deposition method 17 – 20 . Deciphering the local nanostructure and ascertaining the chemical composition at the nanoscale have enabled more accurate estimations of the sp 2 and sp 3 fractions and the thickness of individual layers comprising the layered structure of ultrathin a -C films 13 , 18 – 22 .…”