E. Elizalde

SiCN alloys deposited by electron cyclotron resonance plasma chemical vapor deposition

Silicon–carbon–nitrogen alloys have been deposited by electron cyclotron resonance plasma chemical vapor deposition. Nitrogen, methane, and argon diluted silane have been used as precursor gases. The properties of the deposited films were studied by spectroscopic ellipsometry, Fourier transform infrared spectroscopy, X‐ray photoelectron, and Auger electron spectroscopy. The structure and bond formation in the SiCN films is discussed in terms of the present results.

Friction mechanisms of amorphous carbon nitride films under variable environments: a triboscopic study

Abstract In this work, a carbon nitride film prepared by ion-beam-assisted deposition onto silicon was investigated using reciprocating sliding tests under different surrounding atmospheres (ambient air, dry air, dry nitrogen (DN), and ultra-high vacuum) and testing conditions (contact pressure, nature of the counterface). The carbon–nitrogen (CNx) coating provided a ‘superlow’ friction coefficient of 0.007–0.008 in DN atmosphere independently of the mating material (steel or sapphire balls). The build-up of a smooth transfer film onto the ball surface was detected by optical microscopy. The change in the friction coefficient was spatially recorded along the track as sliding progressed. This technique, called ‘triboscopy’, combined with variable amplitude tests performed on the same wear track, revealed that the nature of both counterfaces (ball and film) has to be modified during a short running-in period before achievement of the superlow friction regime. When other surrounding atmospheres are used, the superlow friction coefficient is not attained even if the counterfaces are previously rubbed in DN. This assembly of tools allowed the characterization of environmental influence on the tribological behavior of CNx coatings in terms of friction coefficient, material transfer, and chemistry of the sliding interface, and the comparison with that observed for diamond-like coatings.

Dielectric properties of Zr, ZrN, Zr3N4, and ZrO2 determined by quantitative analysis of electron energy loss spectra

The dielectric properties of Zr, ZrN, Zr3N4, and ZrO2 in the energy range from 1 to 80 eV were determined by quantitative analysis of electron energy loss spectroscopy in the reflection mode (REELS) using a recently proposed model. Collective excitations and electronic transitions are well characterized in the REELS spectra after analysis of the respective energy loss function, real and imaginary parts of the dielectric constant, and the optical joint density of states for the four compounds studied here.

On the determination of the optical constants n(λ) and α(λ) of thin supported films

Abstract A general method was developed to determine the optical constants n(λ) and α(λ) for a thin semiconducting or metallic supported film from five or three measurements of the transmittance and the reflectance. Exact formulae were deduced for oblique incidence transmittance and reflectance considering multiple coherent reflections in the films and incoherent reflections in the non-absorbing substrate. A computer program was developed that, when used as a subroutine of a European Organization for Nuclear Research program called MINUIT, allowed the method to be tested for gold, silicon, CdS, Cu2S (chalcocite) and Cu1.96S (djurleite) polycrystalline films. A residual function shows good agreement between the calculated and measured values of the transmittance and the reflectance when a careful choice of the value of the thickness is made.

Determination of thickness and optical constants of thin films from photometric and ellipsometric measurements

We describe a computational method of determining the optical constants n(λ),k(λ) and the film thickness d from photometric R(λ),T(λ) and ellipsometric Ψ(λ),Δ(λ) data. Combinations of three or four of the measured quantities are compared using Newton-Raphson and Simplex techniques. The method is applied to thin films of gold and amorphous metallic alloys. The results are discussed.

Correlation between N 1s core level x-ray photoelectron and x-ray absorption spectra of amorphous carbon nitride films

This work presents a comparative analysis of the N 1s core level spectra, as measured by x-ray photoelectron spectroscopy (XPS) and x-ray absorption spectroscopy (XAS), of amorphous CNx films which gives evidence of the existing correlation between the different components that constitute the respective spectra. After annealing, the contribution of XPS at 399.3 eV and the components of XAS at 399.6 and 400.8 eV are clearly enhanced. They are assigned to sp2 with two neighbors and to sp states of nitrogen. In addition, the XPS component at 401.3 eV is related to the XAS feature at 402.0 eV and has been assigned to sp2 nitrogen bonded to three carbon neighbors.

Study of the optical constants determination of thin films: Dependence on theoretical assumptions

We present a critical study of the known reflectance (R) and transmittance (T) method to extract the optical constants of thin film–substrate systems. In order to study the effect of the usual assumptions (homogeneous layers, semi‐infinite substrate, normal incidence angle for reflectance measurement, etc.) in the loss of solution during the numerical inversion process, we have developed a theoretical model that overcomes these approximations. Simulated film–substrate systems as well as RT measurements from a ZnSe film onto a CaF2 substrate have been used to show how accurate film thickness and optical constants can be obtained using a more complete optical model.

Mechanical and tribological properties of TiCxN1−x wear resistant coatings

The aim of this work is to investigate the mechanical and tribological properties of Tic x N 1-x wear resistant coatings grown on a Ti-0.2 Pd alloy substrate. Films were deposited by dual ion beam sputtering (DIBS) system with different proportions of N 2 and Ar in the assisting beam. The friction tests have been carried out with a pin-on-disc tribometer with different applied loads. The films present high hardness and elastic properties whose values depend upon preparation conditions. The mechanical properties and the tribological behaviour of the coatings seem to depend on their stoichiometry and microstructure. The coating TiC 0.5 N 0.5 shows less hardness and better wear resistance than the coating with stoichiometry Tic 0.15 N 0.85 . The influence of the stoichiometry and the local structure of the films on its mechanical properties have been ruled out.

Preparation of hollow magnetite microspheres and their applications as drugs carriers

AbstractHollow magnetite microspheres have been synthesized by a simple process through a template-free hydrothermal approach. Hollow microspheres were surface modified by coating with a silica nanolayer. Pristine and modified hollow microparticles were characterized by field-emission electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, FT-IR and Raman spectroscopy, and VSM magnetometry. The potential application of the modified hollow magnetite microspheres as a drug carrier was evaluated by using Rhodamine B and methotrexate as model drugs. The loading and release kinetics of both molecules showed a clear pH and temperature dependent profile.Graphical abstractHollow magnetite microspheres have been synthesized. Load-release experiments with Rhodamine-B as a model drug and with Methotrexate (chemotherapy drug used in treating certain types of cancer) demonstrated the potential applications of these nanostructures in biomedical applications.

Bonding and morphology study of carbon nitride films obtained by dual ion beam sputtering

Thin carbon–nitrogen films (i.e., CNx) have been obtained by dual ion beam sputtering. The chemical composition and the type of bonding of the CNx material have been examined, as a function of the deposition parameters, by Fourier transform infrared spectroscopy, x-ray photoelectron spectroscopy (XPS), and electron energy loss spectroscopy (EELS). The high concentration of C≡N bonds present in some of the samples, as stated by FT-IR, allowed us to correlate this type of bonding with some of the features observed in the corresponding XPS and EELS spectra. Nitrogen concentrations of up to 45 at. %, depending on the deposition conditions, have been estimated by XPS and EELS. The films deposited at low energy were rather homogeneous, as demonstrated by Auger electron spectroscopy depth profiling, and show the highest C–N simple bonds concentration. On the contrary, the use of high energy assisting nitrogen ions leads to the formation of carbonitrile groups (i.e., C≡N), as well as resputtering effects that significantly reduce the thickness of the films and even hinder the growth of a film. The topography and morphology of the different films, as determined by atomic force microscopy, were also observed to depend on the conditions of assistance.Thin carbon–nitrogen films (i.e., CNx) have been obtained by dual ion beam sputtering. The chemical composition and the type of bonding of the CNx material have been examined, as a function of the deposition parameters, by Fourier transform infrared spectroscopy, x-ray photoelectron spectroscopy (XPS), and electron energy loss spectroscopy (EELS). The high concentration of C≡N bonds present in some of the samples, as stated by FT-IR, allowed us to correlate this type of bonding with some of the features observed in the corresponding XPS and EELS spectra. Nitrogen concentrations of up to 45 at. %, depending on the deposition conditions, have been estimated by XPS and EELS. The films deposited at low energy were rather homogeneous, as demonstrated by Auger electron spectroscopy depth profiling, and show the highest C–N simple bonds concentration. On the contrary, the use of high energy assisting nitrogen ions leads to the formation of carbonitrile groups (i.e., C≡N), as well as resputtering effects that sig...