P. Guérin

Interdependence between stress, preferred orientation, and surface morphology of nanocrystalline TiN thin films deposited by dual ion beam sputtering

To clarify the underlying mechanisms that cause the preferred orientation in TiN films, we investigated the evolution with the thickness of the texture, surface morphology, and residual stress in TiN thin films deposited by dual ion beam sputtering. The films, with thickness h ranging from 50to300nm, were grown on oxidized Si substrates using a primary Ar ion beam accelerated under 1.2kV and different voltages Va of the (Ar+N2) assistance beam: 25, 50, and 150V. The influence of temperature was also investigated by varying the substrate temperature Ts (25–300°C) during growth or by performing a postdeposition annealing. X-ray diffraction (XRD) as well as transmission electron microscopy were used to study the microstructure and changes of texture with thickness h, while x-ray reflectivity and atomic force microscopy measurements were performed to determine the surface roughness. Residual stresses were measured by XRD and analyzed using a triaxial stress model. The crystallite group method was used for a s...

Yttrium oxide thin films, Y2O3, grown by ion beam sputtering on Si

Thin films of yttrium sesquioxide, Y2O3, have been deposited on Si by ion beam sputtering at room temperature and 700 °C under an oxygen pressure of 4×10-3 Pa or by oxygen ion beam assisted deposition. The stoichiometry of these films was analysed by Rutherford backscattering spectrometry. The thickness and refractive index of the oxide were studied as functions of the wavelength by ellipsometry. The crystalline orientations of the deposited films were determined by x-ray diffraction. The micro- and nano-structure were investigated by transmission electron microscopy on cross section samples.

In situ stress evolution during magnetron sputtering of transition metal nitride thin films

Stress evolution during reactive magnetron sputtering of TiN, ZrN, and TiZrN layers was studied using real-time wafer curvature measurements. The presence of stress gradients is revealed, as the result of two kinetically competing stress generation mechanisms: atomic peening effect, inducing compressive stress, and void formation, leading to a tensile stress regime predominant at higher film thickness. No stress relaxation is detected during growth interrupt in both regimes. A change from compressive to tensile stress is evidenced with increasing film thickness, Ti content, sputtering pressure, and decreasing bias voltage.

Zirconium nitrides deposited by dual ion beam sputtering : physical properties and growth modelling

Abstract Zirconium nitrides reveal interesting optical and electrical properties which highly depend on the nitrogen stoichiometry. Indeed, the material exhibits a transition from the stable metallic ZrN (optical index for bulk at 633 nm: N=0.5−i3.2) to the metastable semi-transparent insulating Zr3N4 (N=3.2−i0.4). This work deals with the elaboration of homogeneous ZrN-like and Zr3N4-like coatings. These have been prepared using reactive Dual Ion Beam Sputtering (DIBS) using a Zr target and N2 or N2+Ar reactive gas. The influence of different elaboration parameters (ion energy, gas composition of the reactive beam and substrate temperature) on the nitrides composition and on their optical and electrical properties was particularly studied. A model was proposed to explain the influence of energy and temperature on the nitrogen composition. The nitrogen stoichiometry was shown to be controlled by a competitive mechanism between implantation of excess nitrogen amount in the subsurface and their elimination by exodiffusion. The first phenomenon is mainly controlled by the ion energy whereas the second one is enhanced by a high temperature and a high irradiation defects density. Therefore, the Zr3N4-like nitrides were obtained with low temperature and high energy (200 eV) conditions whereas high temperature and low energy led to ZrN-like materials.

Structure and properties of carbon onion layers deposited onto various substrates

120 keV carbon ions implantations at high fluences (0.5–8×1017 ions cm−2) were performed at elevated temperature (⩾500 °C) in silver layers deposited on various substrates (Si (100), 304 L stainless steel, and pure fused silica). Spherical carbon onions (3–15 nm in diameter) were so produced in the silver layers. A pure carbon onion thin film deposited on the substrate was obtained after annealing in vacuum. Atomic force microscopy and high-resolution transmission electron microscopy experiments were performed to characterize the structure of the thin films. Optical transmittance spectra of carbon onion layers deposited onto silica substrates revealed two absorption peaks centered at 220–230 nm and at 265 nm that were attributed to the presence of carbon onions and residual disordered graphitic carbon, respectively. Tribological experiments performed on silver–carbon onions composite thin films revealed that the friction coefficient is close to that of a pure silver film (0.2) but with much better wear be...

Carbon onions formation by high-dose carbon ion implantation into copper and silver

High-fluence (>1016 cm−2) ion implantations of 120-keV carbon ions have been performed at elevated temperature (≥400°C) into metals (Ag, Cu) in which carbon is almost immiscible. The different carbon structures so synthesized have been characterized by transmission electron microscopy and atomic force microscopy. It mainly results in the formation of numerous carbon onions composed of concentric graphitic layers. We will show that pure carbon onion layers can even be obtained by carbon ion implantation into a silver thin film deposited onto silica. Furthermore, we discuss the potential of the technique in adjusting the size and controlling the microstructure of the carbon onions by varying implantation parameters such as temperature and fluence. We also briefly discuss the nucleation and growth mechanisms of the carbon onions during the ion implantation process.

Yttrium sesquioxide, Y2O3, thin films deposited on Si by ion beam sputtering: microstructure and dielectric properties

Abstract Y2O3 thin films were in-situ deposited by ion beam sputtering on Si substrate. The influence of the deposition parameters are studied by X-ray diffraction, electrical measurements and high resolution transmission electron microscopy observations. The stress sate of the oxide layers is investigated by the sin2ψ method as a function of the deposition parameters and the post-annealing treatments. Oxygen ion beam assisted deposition process or post-annealing of as-deposited thin films lead to the same relaxation of the internal compressive stress within the oxide layer. An SiO2 layer sandwiched between Si and Y2O3 is always observed and should play a role both in the growing process and electrical properties of the MOS structure based on Y2O3 oxide layer. The results are interpreted in terms of diffusional process in the oxide, which are directly related to the temperature and the oxygen partial pressure during the growth process.

Nucleation and growth of carbon onions synthesized by ion-implantation: a transmission electron microscopy study

Carbon onions were synthesized by 120 keV carbon ion-implantation into silver substrates heated at high temperature (>400 °C). Their nucleation and growth mechanisms are discussed from plane view and cross-sectional transmission electron microscope (TEM) characterizations of implanted samples. Implanted carbon atoms precipitate inside the bulk of the silver substrate, allowing the formation of spherical carbon nanostructures distributed in the silver matrix. A progressive transformation of these precipitates into onion-like structures as well as the growth of the carbon nanostructures occurred in the bulk of the substrates when the fluence increased. Furthermore, the correlation between the size of the carbon onions and the carbon concentration into the silver matrix is discussed.

Relation between the optical properties of composite Si3N4 thin films with embedded Cu clusters and the clusters morphology: Irradiation effects

Ion beam sputtering codeposition has been used to elaborate ceramic–metal (cermet) composite thin films consisting of copper nanoclusters embedded in an amorphous Si3N4 matrix. As prepared, the clusters have a size smaller than 3 nm and postirradiation by high energetic Ar+ ions leads to an homogenization of the clusters’ morphology and an increase of the clusters’ size to an average diameter of 4.5 nm. This work deals with the relation between the morphology of the clusters, characterized by extended x-ray absorption fine spectroscopy and grazing incidence small angle x-ray scattering, and the optical properties (obtained by spectroscopic ellipsometry) of the cermets, which are classically modeled with the help of the effective medium theory. In the case of the as-prepared sample, the Bruggeman effective medium theory has been successfully used. This comes from the fact that the clusters are sufficiently close to each other to create mutual interactions. On the other hand, the morphology of the postirrad...

Formation of (Ti,Al)N∕Ti2AlN multilayers after annealing of TiN∕TiAl(N) multilayers deposited by ion beam sputtering

By using ion beam sputtering, TiN∕TiAl(N) multilayers of various modulation wavelengths (Λ=8, 13, and 32nm) were deposited onto silicon substrates at room temperature. After annealing at 600°C in vacuum, one obtains for Λ=13nm a (Ti,Al)N∕Ti2AlN multilayer as it is evidenced from x-ray diffraction, high resolution transmission electron microscopy, and energy filtered electron imaging experiments. X-ray photoelectron spectroscopy (XPS) experiments show that the as-deposited TiAl sublayers contain a noticeable amount of nitrogen atoms which mean concentration varies with the period Λ. They also evidenced the diffusion of aluminum into TiN sublayers after annealing. Deduced from these observations, we propose a model to explain why this solid-state phase transformation depends on the period Λ of the multilayer.