M. J. Rose

Microstructural properties of amorphous carbon nitride films synthesised by dc magnetron sputtering

Amorphous carbon nitride (a-C:N) films have been prepared on silicon(1 0 0) substrates by direct current magnetron sputtering of graphite using a gaseous mixture of Ar and N2. Raman spectra have shown that these a-C:N films have a graphitic structure. The incorporation of nitrogen in the films has been confirmed by Fourier transform infrared (FTIR) spectroscopy. Graphitic and disordered sp2-bonded carbon which are present in Raman spectra and are normally forbidden (not observed) in FTIR become infrared active in our films as the symmetry of the hexagonal carbon rings is broken by nitrogen incorporation. X-ray photoelectron spectroscopy has been used to study the type of chemical bonding in these a-C:N films. The C 1s and N 1s X-ray photoelectron peaks have been deconvoluted and studied. We have found that for the C6-point triple bond; length half of m-dashN and C=N components of the C 1s and N 1s photoelectron peaks, there is a maximum peak intensity ratio of C6-point triple bond; length half of m-dashN:C=N in the films deposited when the gaseous mixture contains 35% N2 in the sputter gas.

X-ray photoelectron spectroscopy studies of the effects of plasma etching on amorphous carbon nitride films

The effects of post-treated oxygen plasma etching procedures have been investigated for amorphous carbon nitride (a-C:N) films deposited by dc magnetron sputtering. X-ray photoelectron spectroscopy (XPS) has been used to study the microstructure of these films. It has been found that the relative concentration of the beta-C3N4-like phase in the a-C:N films is enhanced significantly by oxygen plasma etching and by increasing the dc bias voltages during the etch experiments. This study reveals that an oxygen plasma can work as an effective chemical etchant for the graphite-like carbon-nitrogen phase in a-C:N films. This suggests a very promising way of obtaining harder a-C:N films.

The effect of postdeposition annealing on chemical bonding in amorphous carbon nitride films prepared by DC magnetron sputtering.

Abstract The effects of thermal annealing on the surface morphology, composition and chemical bond structure of amorphous carbon nitride (a-C:N) films deposited by dc magnetron sputtering are reported. Atomic force microscopy (AFM) results show that thermal annealing can gradually change the surface structure of the films from a cauliflower-like texture eventually to a uniform granular texture. Fourier transform infrared absorption (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) have been used to characterise the change of chemical bonding induced by annealing. By detailed analysis of both C 1s and N 1s photoelectron spectra, we have found that annealing can break the CN bonds in the films and that the graphite-like CN bonds are relatively more stable with the increase of anneal temperature.

Characterisation of cubic boron nitride films at different stages of deposition

Cubic boron nitride (c-BN) films have been prepared by tuned substrate RF magnetron sputtering with different deposition times. The films have been characterised by Fourier Transform Infrared Absorption (FTIR) spectroscopy, X-ray Photoelectron Spectroscopy (XPS) and by Atomic Force Microscopy (AFM) measurements. The results show changes in composition and microstructure of the films with different deposition times that correspond to different growth stages of the BN films. By analysing the AFM images, we believe the BN layer formed at the early stages of deposition have a hillock morphology.

Variation of bonding structure near the surface of carbon nitride films

Abstract Amorphous carbon nitride (a-C:N) films were deposited by reactive direct current magnetron sputtering of graphite using a gaseous mixture of Ar and N 2 . X-ray photo electron spectroscopy analysis (XPS) showed that there is an optimum volume ratio of nitrogen:argon in the sputter gas that results in a maximum content of incorporated nitrogen in the films. By using different take-off angles in XPS experiments, the variation gradient of bonding structure near the surface of a-C:N films has also been studied. In the surface layer of the a-C:N films, it was found that some of the initially formed β-C 3 N 4 -like phase transforms to a graphite-like carbon–nitrogen phase. This structural change is driven by the nitrogen in the sputter gas during deposition.

Microstructural studies of copper incorporated amorphous carbon nitride films

The effects of the incorporation of copper on the microstructure of amorphous carbon nitride films has been studied. Copper incorporated amorphous carbon nitride films (a-C : N : Cu) with different copper concentrations have been prepared by a magnetron co-sputtering technique. Both X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) have been used to characterise the bonding structures in the films. It is found that the N/(N+C) atomic ratio increases due to the incorporation of copper. The results also show that copper incorporation promotes formation of the sp3-bonded carbon nitrogen phase. The diamond nucleation in a-C : N : Cu films, which is determined from the observation of two-phonon diamond absorption FTIR bands, has been ascribed to the favorable formation of the sp3-bonded carbon nitrogen phase in the a-C : N : Cu films.

Cubic boron nitride films prepared with different deposition times

Since the physicochemical properties of cubic BN (c-BN) makes it a very useful material for various industrial and technological applications, cubic boron nitride films have aroused much attention in recent years. In this paper, c-BN films have been prepared by tuned substrate rf magnetron sputtering with different deposition time, which correspond to different growth stages of the BN films. Fourier Transform Infrared Absorption spectroscopy, X-ray Photoelectron Spectroscopy and Atomic Force Microscopy (AFM) have been used to characterize the films. We have found a change of composition and microstructure of the films with different deposition times. AFM images of thicker films showed that there are two BN layers on the substrate and nucleation lines were observed on the lower BN layer of the film. We believe that the thickness difference between the edge and the center of the c-BN sheets of the film, which was also observed in the AFM profile, gives some information about the growth mechanism of c-BN films.

Influence of rf power on carbon nitride films prepared by rf magnetron sputtering

Since (beta) -C3N4 has been predicted to be a superhard material with a higher hardness than diamond, many research groups have attempted to synthesize carbon nitride materials. We have prepared amorphous carbon nitride (a-C:N) films by rf magnetron sputtering of graphite with N2 as the sputter gas. In this investigation, a series of film samples have been deposited at different rf power. AFM images have shown that the higher the rf power, the bigger the cluster size on the films and the rougher the surface of the films. By analyzing the results of our XPS experiments, we have found that with the decrease of the rf power, not only the incorporated nitrogen but also the concentration of sp3-bonded nitrogen in the films increased. We believe this is because f lower rf power results in smaller carbon clusters on the surface of the films, leading to larger carbon surface area. A larger film surface area makes it easier for the nitrogen to bond with carbon.