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Nitrogen-incorporated tetrahedral amorphous carbon (ta-C:N) has electrochemical properties that are comparable to boron-doped diamond (BDD), but can be deposited at low temperatures, and is scalable across substrate areas substantially exceeding what is currently possible for BDD. Most published studies of ta-C:N electrodes focus on films deposited on conductive substrates due to the relatively high resistivity of ta-C:N compared to other carbon and metal-based electrodes. However, some of the most compelling applications of electrochemistry, for example, optically transparent spectroelectrochemical devices, require insulating substrates such as fused silica glass (FSG) or polymers. In this study, we deposited 50 nm of ta-C:N by laser controlled pulsed cathodic vacuum arc (Laser-Arc) onto insulating FSG to investigate the electrochemical response compared to conductive silicon (c-Si) substrates. No oxidation or reduction of potassium ferrocyanide during cyclic voltammetry (CV) could be observed at the FSG electrode. To address this, we introduced a 5 nm chromium (Cr) interlayer deposited by magnetron sputtering between ta-C:N and FSG. This electrode configuration led to clear cathodic and anodic CV peaks of potassium ferro/ferricyanide but with an increased peak separation compared to the c-Si electrode. However, the peak separation could be reduced to values comparable to ta-C:N deposited on c-Si by optimizing Cr sputtering conditions and introducing an argon plasma pretreatment of the FSG surface. Atomic force microscopy revealed that these changes improved the Cr growth homogeneity, which in turn increased the electrical conductivity of the Cr interlayer as determined by 4-point probe measurements. [ABSTRACT FROM AUTHOR]

A single-beam plasma source was developed and used to deposit hydrogenated amorphous carbon (a-C:H) thin films at room temperature. The plasma source was excited by a combined radio frequency and direct current power, which resulted in tunable ion energy over a wide range. The plasma source could effectively dissociate the source hydrocarbon gas and simultaneously emit an ion beam to interact with the deposited film. Using this plasma source and a mixture of argon and C2H2 gas, a-C:H films were deposited at a rate of ∼26 nm/min. The resulting a-C:H film of 1.2 µm thick was still highly transparent with a transmittance of over 90% in the infrared range and an optical bandgap of 2.04 eV. Young's modulus of the a-C:H film was ∼80 GPa. The combination of the low-temperature high-rate deposition of transparent a-C:H films with moderately high Young's modulus makes the single-beam plasma source attractive for many coatings applications, especially in which heat-sensitive and soft materials are involved. The single-beam plasma source can be configured into a linear structure, which could be used for large-area coatings. [ABSTRACT FROM AUTHOR]

A single beam plasma source was used to deposit hydrogenated amorphous carbon (a-C:H) coatings at room temperature. Using methane source gas, a-C:H coatings were deposited at different radio frequency (RF) power to fabricate transparent and durable coatings. The film deposition rate was almost linearly proportional to the ion source power. Hydrogenated amorphous carbon films of ~100 nm thickness appeared to be highly transparent from UV to the infrared range with a transmittance of ~90% and optical bandgap of ~3.7 eV. The coatings also possess desirable mechanical properties with Young's modulus of ~78 GPa and density of ~1.9 g/cm3. The combined material properties of high transmittance and high durability make the ion-source-deposited a-C:H coatings attractive for many applications. [ABSTRACT FROM AUTHOR]