M. Benlahsen

Correlation between plasma parameters, microstructure and optical properties of sputtering magnetron CNx films

Abstract Analysis of carbon nitride films (CN x ) deposited by radio frequency (RF) magnetron sputtering on crystalline silicon, under different target self-bias, is reported. Plasma characterisation was performed using mass spectroscopy (MS) and the properties of films were determined in their as deposited state using elastic recoil detection analysis (ERDA), nuclear reaction analysis (NRA), X-ray photoelectron spectroscopy (XPS), infrared absorption, transmission spectroscopy and photothermal deflection spectroscopy (PDS) experiments. A good correlation is observed between the variation of N/C ratio and the growth rate. The resulting changes in the microstructure can be analyzed in terms of surface processes, nitrogen incorporation within the films and the Csp 2 content.

Optical investigations and Raman scattering characterisation of carbon bonding in hard amorphous hydrogenated carbon films

Abstract Hydrogenated amorphous carbon films were prepared by plasma enhanced chemical vapour deposition (PECVD) of methane–argon (5%) gas mixtures at low pressure, in a dual electron cyclotron resonance (ECR)-rf glow discharge. Optical transmission spectroscopy, Raman spectroscopy, elastic recoil detection analysis (ERDA) and infra-red (IR) absorption spectra were combined to examine the relationship between the local microstructure (Cue5f8H and Cue5f8C bonds) and the optical properties at different negative bias voltage. The amount of bonded H, obtained by IR spectra, is higher in series deposited at low bias voltage, in qualitative agreement with the ERDA results. In all cases, most of the incorporated H is bonded to sp3C sites, with a predominance of CH3 methyl groups. These results are also consistent with the Raman spectroscopy measurements. The positions, widths, and relative intensities of the two characteristic features, the D and G peaks are found to vary systematically with deposition conditions and film properties. The series prepared at high bias voltage shows a higher disorder (D) over the graphitic (G) band ratio, which also indicates a structure with a high disorder form of Csp2 sites.

Effect of annealing on the structural and electrical properties of d.c. multipolar plasma deposited a-C:H films

Abstract The changes upon annealing in Cue5f8H and Cue5f8C bonding in relation to the structural and electronic properties have been investigated in two different series of a-C:H samples prepared in a direct current (d.c.) multipolar plasma system from pure methane at quite different substrate bias (−40 and −600 V). Using a combination of infrared absorption, elastic recoil detection analysis, high resolution transmission electron microscopy and electrical resistance measurements, we fully characterize the samples in their as-deposited state as well as after successive annealing cycles at increasing temperatures up to 700°C. The results show clearly that the two types of series exhibit quite different microstructures and hydrogen incorporation in their as-deposited state. The low bias (−40 V) series exhibits a highly disordered structure, while the high bias (−600 V) one already contains well ordered regions. They also have a completely different behavior upon annealing up to high temperature. A microstructure conversion such as from hydrogenated as well as non-hydrogenated sp 3 C sites to sp 2 C ones occurs in the temperature range 400–500°C in all cases. However, a more efficient graphitization is observed in the high bias series (−600 V) for annealing temperatures as high as 700°C. Quite surprising results are obtained for the low bias series (−40 V): contrarily to what is usually observed for this type of sample, this series is found to be more thermally stable for high annealing temperature (>400°C) than the high bias one (−600 V). These results are discussed and explained in terms of the relaxation process in the local microstructure.

Growth and bonding structure of hard hydrogenated amorphous carbon thin films deposited from an electron cyclotron resonance plasma

Analysis of hard hydrogenated amorphous carbon films (a-C:H) deposited from an electron cyclotron resonance radio frequency discharge of methane–argon (5%) mixture at low pressure is reported. The properties of films were determined in their as deposited state using elastic recoil detection analysis, infrared absorption, Raman spectroscopy, transmission spectroscopy, photothermal deflexion spectroscopy, and residual stress measurements. The microstructural changes (i.e., hydrogen content and C-sp3/C-sp2 ratio) have been explained qualitatively in terms of a balance between implantation and relaxation processes. A good correlation is observed between the variation of Raman features and the optical gap as a function of the self-bias substrate. The residual stress versus bias plot shows behavior similar to that already obtained for tetrahedral amorphous carbon films and the optimum energy, which corresponds to films of maximum C–Cu200asp3, is similar to those obtained in the literature.

Optical behavior of reactive sputtered carbon nitride films during annealing

The effect of annealing temperature (TA) on amorphous carbon nitride (a-CNx) thin films, deposited using radio-frequency (rf) magnetron sputtering technique of a graphite target in a pure nitrogen (N2) atmosphere at different rf power, is investigated. Film composition was analyzed using Fourier transform infrared absorption (FTIR), Raman spectroscopy, optical transmission, and photothermal deflection spectroscopy (PDS) experiments. The refractive index and the mass density were determined using optical transmission spectroscopy and elastic recoil detection analysis measurements. The microstructure analysis revealed the porous character of films, which decreases slowly with increasing annealing temperature (TA). The results of Raman spectroscopy, FTIR, and PDS experiments demonstrate that the films below 400°C mainly consist of aromatic cluster component and polymeric component. With increasing TA, the progressive graphitization of the material is accompanied by a high disorder form of Csp2 sites.

On the induced microstructure changes of the amorphous carbon nitride films during annealing

The analysis of the stress release and structural changes caused by postdeposition thermal annealing of amorphous carbon nitride thin films (a‐CNx) has been carried out. The a‐CNx films were deposited on Si (100) using reactive radio frequency (rf) magnetron sputtering of a high-purity graphite target in a pure nitrogen plasma under various different rf powers. Combined Fourier transform infrared (FTIR), Raman spectroscopy, transmission spectroscopy, photothermal deflexion spectroscopy, and residual stress measurements were used to fully characterize the films. Annealing of the samples in vacuum at temperature up to 600°C produces changes in their structural properties and the intrinsic stress. These changes are found to be strongly dependent on both the deposition conditions and microstructure changes occurring within the films during heating. FTIR spectra showed the existence of N–C sp3, Nue5fbC sp2, and Cue5fcN triple bonds in the deposited films. The analysis of the spectra versus annealing temperature (TA) r...