This paper reports the structural and electrochemical behaviour of TiN thin films prepared by d.c. reactive magnetron sputtering. x
X-Ray diffraction showed the development of the hexagonal a-Ti phase, with strong w002x orientation, for low nitrogen contents.
For nitrogen contents of 20 and 30 at.%, the ´-Ti N phase appears with w200x orientation. With further increasing the nitrogen 2
content, the d-TiN phase becomes dominant. Composition and the resulting changes in microstructure (crystalline phases and the
lattice distortion induced by the growth conditions) are the two main parameters that seem to rule coating properties. Results of
potentiodynamic polarisation tests showed that all films have a high corrosion resistance reflected by corrosion current densities
below 0.7 mAycm . Also, electrochemical impedance spectroscopy tests corroborated the results obtained in the polarisation tests, 2
showing that films containing low percentages of nitrogen (less than 8%) reveal the best corrosion resistance. Further increases
in nitrogen content lead to a decrease in the corrosion resistance. An exception to this behaviour was found for the film with 30
at.% N. This sample presents an excellent corrosion resistance, which in fact...
This paper reports on the preparation of TiNx thin films by d.c. reactive magnetron sputtering. The coating thickness ranged from 1.7 to
4.2 Am and the nitrogen content varied between 0 and 55 at.%. X-Ray diffraction showed the development of the hexagonal a-Ti phase, with
strong  orientation for low nitrogen contents, where the N atoms fit into octahedral sites in the Ti lattice as the amount of nitrogen is
increased. For nitrogen contents of 20 and 30 at.%, the q-Ti2N phase appears with  orientation. With further increasing the nitrogen
content, the y-TiN phase becomes dominant. The electrical resistivity of the different compositions reproduces this phase behavior. The
hardness of the samples varied from approximately 8 GPa for pure titanium up to 27 GPa for a nitrogen content of 30 at.%, followed by a
slight decrease at the highest contents. A similar increase of stresses with nitrogen is observed. Structure and composition with the
consequent changes in crystalline phases and the lattice distortion were found to be crucial in the evolution of the mechanical properties.
Ti–Si–C–ON films were deposited by DC reactive magnetron sputtering using different partial pressure ratio of oxygen (pO2) and nitrogen (pN2). Compositional analysis revealed the existence of three different growth zones for the films; (I) N/Ti = 2.1 (high atomic ratio) and low oxygen content; (II) 0.76 < N/Ti < 2.1 (intermediate atomic ratio) and (III) N/Ti ≤ 0.12 (low ratio) and high oxygen content. For high N/Ti atomic ratio (N/Ti = 2.1) the XRD pattern exhibits reflections that correspond to a mixture of two different phases: a metallic-like Ti and a fcc NaCl type structure. Its electrical resistivity presents a metallic character and, consequently, has high infrared reflectivity. For the intermediate N/Ti ratio (0.76 < N/Ti < 2.1), the films crystallize in a B1-NaCl crystal structure typical for TiC0.2N0.8. Their FTIR spectra present C–N modes, besides the TiN ones, that indicate a progressive substitution of nitrogen by carbon atoms with increasing oxygen content (and lowering N/Ti ratio). For the highest oxygen content (and lower N/Ti ratio) the presence of the Ti–O–Ti stretching mode shows the formation of highly resistive Ti–O compounds consistent with the semiconductor character of this film. Biofilm formation as well as material cytotoxicity seemed to be related with the presence of the Ti.
Raman spectroscopy results obtained under visible (non-resonant) and UV (resonant) excitation for nanocrystalline ZnO, ZnO:Mn and ZnO:Mn:Al thin films grown by radio frequency magnetron sputtering are presented and compared. The origin of the multiple longitudinal optical (LO) phonon Raman peaks, strongly enhanced under resonance conditions, and the effects of the dopants on them are discussed in the framework of the ‘cascade’ model. It is
suggested that the observed suppression of the higher-order LO phonon lines for ZnO:Mn:Al is caused by the dissociation of excitons in the heavily n-type doped material. On the basis of the cascade model interpretation of the higher-order Raman peaks in the resonant spectra, the LO
phonon frequencies for wavevectors away from the gamma point are evaluated and compared topreviously published phonon dispersion curves.; Financial support from the FCT through
project PTDC/FIS/72843/2006 is acknowledged.
The present work is devoted to the optical properties of Au:TiO2 thin films in order to clarify the role of the Au clusters inclusions in the TiO2 dielectric matrix. Three series of films containing about 30 at.% (29.2), 20 at.
% (19.8) and 10 at.% (9.3) Au were deposited by dc reactive magnetron sputtering. On thermal annealing in the range from 300 to 800 °C in protective atmosphere, significant changes on the crystalline phases and clusters dimensions were detected. The most promising optical behavior was found
for the film 20% Au:TiO2, where the films revealed some colour changes, evolving from several shades of grey to different tones of red. This change in the optical behaviour of the films was found to be correlated with a
cluster size increase from 2 to 17 nm. For higher size values (>20 nm) the films, independently of the Au content, showed a golden appearance colour. The optical changes were confirmed by reflectivity and CIELab colour measurements. Regarding the films with 10 and 30 at.% Au, the results confirmed that there is an evident range of compositions and clusters size where the SPR is more evident. Sample A (10 at.% Au) it
seems to be in the lower limit of the SPR showing a typical interferometric behavior on the reflectivity measurements...
For the first time, the TiO2 nanorod arrays have been prepared on ITO substrates at room temperature by dc reactive magnetron sputtering technique. These TiO2 nanorods have a preferred orientation along the (220) direction and are perpendicular to the ITO substrate. Both the X-ray diffraction and Raman scattering measurements show that the highly ordered TiO2 nanorod arrays have an anatase crystal structure. The diameter of the nanorod varies from 30 nm to 100 nm and the nanorod length can be varied from several hundred nanometers to several micrometers depending on the deposition time. The TiO2 nanorod arrays with about 3 micrometers length have been used as an electrode for dye-sensitized solar cell (DSSC). Short-circuit photocurrent density, open-circuit voltage, fill factor and light-to-electricity conversion efficiency at 100 mW/cm2 light intensity are estimated to be 12.76 mA/cm2, 0.65 V, 0.63 and 5.25%, respectively, for the DSSC made of the TiO2 nanorods.; SFRH/BSAB/862/2008, FCT
Dark Ti-C-O-N thin films were deposited by dc reactive magnetron sputtering. A titanium target was sputtered while three different gas flows were injected into the deposition chamber: argon (working gas), acetylene and a mixture of oxygen and nitrogen (reactive gases). The films were produced with variation of the gases flow rates, maintaining the remaining parameters constant. Varying the ratio between the reactive gases flow (gas mixture/acetylene) allowed obtaining films with different characteristics. The colour of the films was characterized by spectral reflectance spectroscopy, and expressed in
the CIE 1976 L*a*b* colour space. An accurate control of the deposition conditions allowed obtaining intrinsic and stable dark colours for decorative applications. Composition analysis by electron probe microanalysis was done to quantify the
elemental concentrations in the films. X-ray diffraction experiments revealed the evolution of the film structure which showed to be essentially amorphous, but with evidences of fcc structure.; Fundação para a Ciência e Tecnologia (FCT) - SFRH/BPD/27114/2006 and PTDC/CTM/69362/2006.
Erbium-doped low-dimensional Si films with different microstructures were grown by reactive magnetron sputtering on glass substrates by varying the deposition parameters. Their structure and chemical composition were studied by micro-Raman and Rutherford backscattering spectrometry, respectively. In this contribution the Erbium emission is studied as a function of nanocrystalline fraction and average crystal sizes and also as a function of the matrix chemical composition. We discuss the temperature dependence of the Er3+ emission as well as the possible explanations of the low Er active fraction.; FCT (POCTI/CTM/39395) and INTAS
In this work, a study of the structure and optical properties of undoped ZnO thin films produced by r.f. magnetron sputtering technique as a function of the growth parameters is reported. Modification under annealing conditions is also analysed. Raman spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction and optical transmittance have been used. From the position of the (002) X-ray diffraction peak and the E2 (high) mode detected in Raman spectra, the residual stress both in the as-grown and in the annealed samples has been estimated.
Erbium-doped low-dimensional Si films with different microstructures were deposited by reactive magnetron sputtering on glass substrates by varying the hydrogen flow rate during deposition. Amorphous, micro- and nanocrystalline samples, consisting of Si nanocrystalls embedded in silicon-based matrices with different structures, were achieved with optical properties in the visible and IR depending on nanocrystalline fraction and matrix structure and chemical composition. Structural characterization was performed by X-ray diffraction in the grazing incidence geometry and Raman spectroscopy. The chemical composition was studied using RBS/ERD techniques. Spectroscopic ellipsometry was combined with the previous techniques to further re-solve the film microstructure and composition. In particular, the distribution along the film thickness of the volume fractions of nanocrystalline/amorphous silicon and SiOx phases has been obtained.
In this contribution we discuss visible and infrared photoluminescence as a function of sample microstructure and of the oxygen/ hydrogen concentration ratio present in the matrix.; FCT (POCTI/CTM/39395); INTAS Project #03-51-6486
In this contribution we present the Visible and near IR photoluminescence (PL) analysis of Er doped nanocrystalline silicon thin films produced by rf magnetron sputtering method. Efficient photoluminescence was observed in these structures in both visible and 1.54µm wavelength regions. We show the strong influence of the presence of nanocrystalline fraction in films on their luminescence efficiency at 1.54 μm that has been studied on the series of specially prepared samples with the different crystallinity, i.e. percentage and sizes of Si nanocrystals. The mechanism involved in the visible photoluminescence of highly a crystalline nc-Si:H consisting of about 7 nm silicon nanocrystals embedded in an amorphous matrix is discussed.
We have produced and studied undoped and erbium-doped nanocrystalline silicon thin films in order to evaluate the erbium influence on the film microstructure and how this correlates with the photoluminescence properties. Films were grown by reactive RF sputtering. For the doped films metallic erbium was added to the c-Si target. The structural parameters and the chemical composition of the different samples were investigated by X-ray in the grazing incidence geometry, Raman spectroscopy, ellipsometry and Rutherford Back Scattering. The effect of the nc-Si/SiOx matrix ,i.e., nc-Si volume fraction and the presence of SiO and/or SiO2 phases, on the erbium photoluminescence efficiency is discussed.
Microcrystalline silicon thin films doped with erbium were produced by RF sputtering and their structural, chemical and optical properties were studied by X-ray diffractometry at grazing incidence, Rutherford back scattering and optical transmission spectroscopy. The samples exhibit a sharp photoluminescence (PL) spectrum from the Er centres with the strongest peak positioned at 1.536 microm with a full width at half maximum of about 8 nm. When the temperature varies between 5K and 300K the photoluminescence decreases only five fold, in contrast to the behaviour reported for monocrystalline silicon.
Microcrystalline silicon thin films were produced by reactive magnetron sputtering on glass substrates under several different conditions (RF power and gas mixture composition). The film structure was studied by X-ray diffractometry (XRD), transmission electron microscopy (TEM) and Raman spectroscopy, allowing the determination of crystal sizes, crystallinity and mechanical strain. These parameters were evaluated by fitting a pseudo-Voigt function to the X-ray data, and by the application of the strong phonon confinement model to the Raman spectra. The degree of crystallinity and the presence of single crystals or crystal agglomerates, which was confirmed by TEM, depends on the preparation conditions, and strongly affects the optical spectra and the electrical transport properties.; Fundação para a Ciência e a Tecnologia (FCT) - PRAXIS XXI
Staphylococcus epidermidis has emerged as one of the major nosocomial pathogens associated with infections of implanted medical devices. The initial adhesion of these organisms to the surface of biomaterials is assumed to be an important stage in their colonization. The main objective of this work is to assess the influence of surface features on the adhesion of S. epidermidis to Ag–TiCN coatings deposited by dc reactive magnetron sputtering. The
structural results obtained by x-ray diffraction show that the
coatings crystallize in a B1-NaCl crystal structure typical of TiC0.3N0.7. The increase of Ag content promoted the formation of Ag crystalline phases. According to the results obtained with atomic force microscopy, a decrease on the surface roughness of the films from 39 to 7 nm is observed as the Ag content increases from 0 to 15 at.%. Surface energy results show that the increase of Ag promotes an
increase in hydrophobicity. Bacterial adhesion and biofilm formation on coatings were assessed by the enumeration of the number of viable cells. The results showed that the surface with lower roughness and higher hydrophobicity leads to greater bacterial adhesion and biofilm formation, highlighting that surface morphology and hydrophobicity rule the colonization of materials.
TiO2 nanorods were prepared by DC reactive magnetron sputtering technique and applied to dye-sensitized solar
cells (DSSCs). The length of the TiO2 nanorods was varied from 1 μm to 6 μm. The scanning electron microscopy
images show that the nanorods are perpendicular to the substrate. Both the X-ray diffraction patterns and Raman
scattering results show that the nanorods have an anatase phase; no other phase has been observed. (101) and
the (220) diffraction peaks have been observed for the TiO2 nanorods. The (101) diffraction peak intensity
remained constant despite the increase of nanorod length, while the intensity of the (220) diffraction peak
increased almost linearly with the nanorod length. These nanorods were used as the working electrodes in
DSSCs and the effect of the nanorod length on the conversion efficiency has been studied. An optimum photoelectric
conversion efficiency of 4.8% has been achieved for 4 μm length nanorods.
Nowadays, with the increase of elderly population and related health problems, knee and hip joint prosthesis are being widely used worldwide. However, failure of these invasive devices occurs in a high percentage thus demanding the revision of the chirurgical procedure. Within the reasons of failure, microbial infections, either hospital or subsequently-acquired, contribute in high number to the statistics. Staphylococcus epidermidis (S. epidermidis) has emerged as one of the major nosocomial pathogens associated with these infections. Silver has a historic performance in medicine due to its potent antimicrobial activity, with a broad-spectrum on the activity of different types of microorganisms. Consequently, the main goal of this work was to produce Ag-ZrCN coatings with antimicrobial activity, for the surface modification of hip prostheses.
Thin films of ZrCN with several silver concentrations were deposited onto stainless steel 316 L, by DC reactive magnetron sputtering, using two targets, Zr and Zr with silver pellets (Zr + Ag target), in an atmosphere containing Ar, C2H2 and N2. The antimicrobial activity of the modified surfaces was tested against S. epidermidis and the influence of an activation step of silver was assessed by testing samples after immersion in a 5 % (w/v) NaClO solution for 5 minutes.
The activation procedure revealed to be essential for the antimicrobial activity...
We have produced and studied erbium doped nanocrystalline silicon thin films with different oxygen and hydrogen content in order to evaluate the influence of the matrix on the Er3+ emission and on the 0.89 eV and 1.17 eV bands. Films were grown by reactive magnetron sputtering on glass substrates under several different conditions (RF power, Er content and gas mixture composition) in order to obtain different microstructures. The structural parameters and the chemical composition of the samples were obtained by X-ray in the grazing incidence geometry, Raman spectroscopy and Rutherford back scattering analysis. Using X-ray technique combined with Raman spectroscopy information on the crystalline fraction and the average crystallite size of Si nanocrystals was obtained. Dependence of the 0.89 eV and 1.17 eV peaks in Si heterogeneous matrixes on the films crystallinity and O/H ratio has been analyzed.; FCT - POCTI/CTM/39395/2001; INTAS #03-51-6486
Sm-Co/Fe, hard/soft magnetic bilayers have been fabricated on 70 nm Cr buffered Si (100) substrate by dc and rf magnetron sputtering and annealed at 525O C for 30min. Very thin Mo layers (0-0.7 nm) were introduced between Sm-Co and Fe layers. The samples were analyzed by X-Ray Diffraction (XRD) and Alternating Gradient Magnetometer (AGM). All of the samples showed strong exchange coupling between hard and soft magnetic phases. Magnetization, coercivity and energy product (BH)max suggest a sinusoidal behavior. The energy product was found increased to 45% for 0.3 nm Mo interlayer as compared to sample without Mo layer.