Thickness dependency of field emission in amorphous and nanostructured carbon thin films

Thickness dependency of the field emission of amorphous and nanostructured carbon thin films has been studied. It is found that in amorphous and carbon films with nanometer-sized sp2 clusters, the emission does not depend on the film thickness. This further proves that the emission happens from the surface sp2 sites due to large enhancement of electric field on these sites. However, in the case of carbon films with nanocrystals of preferred orientation, the emission strongly depends on the film thickness. sp2-bonded nanocrystals have higher aspect ratio in thicker films which in turn results in higher field enhancement and hence easier electron emission.Published versio

Electrowetting control of Cassie-to-Wenzel Transitions in superhydrophobic carbon nanotube-based nanocomposites

The possibility of effective control of the wetting properties of a nanostructured surface consisting of arrays of amorphous carbon nanoparticles capped on carbon nanotubes using the electrowetting technique is demonstrated. By analyzing the electrowetting curves with an equivalent circuit model of the solid/liquid interface, the long-standing problem of control and monitoring of the transition between the "slippy" Cassie state and the "sticky" Wenzel states is resolved. The unique structural properties of the custom-designed nanocomposites with precisely tailored surface energy without using any commonly utilized low-surface-energy (e.g., polymer) conformal coatings enable easy identification of the occurrence of such transition from the optical contrast on the nanostructured surfaces. This approach to precise control of the wetting mode transitions is generic and has an outstanding potential to enable the stable superhydrophobic capability of nanostructured surfaces for numerous applications, such as low-friction microfluidics and self-cleaning

Wettability, nanoscratch resistance and thermal stability of filtered cathodic vacuum arc grown nitrogenated amorphous carbon films

International audienceComposition, structure, surface energy, nanoscratch resistance and thermal stability of nitrogenated amorphous carbon films grown by filtered cathodic vacuum arc (FCVA) are studied in this paper. X-ray photoelecti-on spectroscopy and electron energy loss spectroscopy studies reveal that by controlling the nitrogen flow rate and substrate bias carbon films with different bonding structures and composition are formed. Higher nitrogen flow rate results in higher nitrogen content of the film and the stability of C equivalent to N bonds. Increasing the nitrogen content of the films (0 to 16 at.%) increases the polar surface energy (10 to 22 mJ/m(2)) of the films while the dispersive surface energy does not change significantly. Thermal stability of the films strongly depends on the composition and bonding structure. The films deposited at higher substrate bias "(300 V) and containing higher nitrogen content undergo graphitization at lower annealing temperatures. There is no significant difference in the scratch resistance of the films at small scratch loads (up to 35 mu N). Further increase in the scratch load results in larger scratch depth in the film deposited at high nitrogen flow rate (40 sccm)

Microstructure and electrical properties of in-situ annealed carbon films

The microstructure and electrical properties of in-situ annealed carbon films is studied in this paper. The structure of the films is studied by transmission electron microscopy, electron energy loss spectroscopy and Raman spectroscopy. The microstructure of the films strongly depends on the deposition temperature for the films deposited at high temperatures (higher than 400°C). However, at low temperatures the substrate bias is the other crucial factor which governs the microstructure of the film. Electrical conductivity of the film strongly depends on the formation of preferred orientation in the microstructure of the films.Accepted versio

Superhydrophobic carbon nanotube/amorphous carbon nanosphere hybrid film

Fabrication of superhydrophobic surfaces has been widely investigated due to their wide range of applications. Here, synthesis of self-assembled aligned carbon nanotubes (ACNT)/amorphous carbon (a-C) nanosphere hybrid film is reported. Carbon plasma produced by FCVA was used to deposit a-C nanospheres on the ACNT films fabricated by PECVD. The superhydrophobic properties of the surface was investigated by static contact angle (CA) measurement. It is found that the surface morphology of the film which depends on the size of the a-C nanospheres, has a great influence on the hydrophobic properties of the surface. The hydrodynamic properties of the surface is discussed in terms of both Cassie and Wenzel mechanisms. The microstructure of the films is also investigated by XPS and HRTEM. It is shown that the bombardment of the CNTs with high energy carbon ions will damage the crystalline structure of the CNT walls as well

Highly conductive aligned carbon film for interconnect application

We demonstrate here an amorphous carbon film with a highly conductive transition phase for interconnect application. The uniform orientation of graphite-like sheet provides an effective carriers transport channel, thus significantly improves the conductivity of the amorphous carbon film. The electrical properties of the aligned carbon film are investigated using Kelvin structure. Our results show that the resistivity of aligned carbon film is comparable with that of Cu, and the aligned carbon film holds promise for future interconnect application.Accepted versio

Electrical properties of textured carbon film formed by pulsed laser annealing

Previous works have showed that textured carbon film can be fabricated by applying suitable ion energy and substrate temperature. In this experiment, the effect of laser annealing on amorphous carbon films was studied. Atomic force microscopy shows the effect of laser irradiation on surface morphology of carbon film, and visible Raman spectroscopy shows that the G peak position shifted from 1540 cm− 1 to 1600 cm− 1, and the increase in I(D)/I(G) intensity ratio indicates the formation of more graphitic film at higher laser energy. High resolution transmission electron microscopy (HRTEM) shows the vertical alignment formation at suitable laser energy. Electrical measurement shows that the vertical aligned carbon films exhibit low resistance, ohmic current–voltage characteristics, which suggests that vertical aligned films formed by laser irradiation may be promising material for future nano-device interconnects