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The present paper reports on an experimental investigation of the structural, electrical and optical properties of Ru rich Ru1-xTixO2 thin films. Rutile single-phase Ru1-xTixO2 thin films have been deposited by reactive hybrid High-power impulse magnetron sputtering (HiPIMS) and direct current magnetron sputtering (DCMS) at a substrate temperature of 250 °C. The HiPIMS source was applied to the Ru target while the DCMS source was connected to the Ti target in order to vary the Ti content in the films. The films are well crystallized and compact with randomly orientated nanocrystallites. The optical properties have been investigated by ellipsometric measurements in the optical energy range from 1.3 eV to 3.3 eV, while the electrical resistivity has been measured in the Van der Paw configuration at room temperature. The electrical resistivity increases gradually from 70 μΩcm for pure RuO2 to about 243 μΩcm for Ru1-xTixO2 films with x = 0.13. The optical properties are correlated with the Ti doping. The refractive index n changes from a strong dispersion relationship to a moderate one with increasing Ti content.

DC reactive magnetron sputtered NbzAlyNx coatings with various Al contents (y/(y + z)) ranging from 0 to 0.75 were deposited using different ratios of the currents applied to the Al and Nb targets in order to systematically control their chemical composition and crystalline structure, and to enhance their mechanical, tribological and thermal stability performance. The film microstructure and properties were assessed by various complementary techniques such as electron probe microanalysis, X-ray diffraction, nanoindentation, ball-on-disc test, and scanning electron microscopy. It was found that the solubility limit of Al in the NbN lattice is in the range 0.44 0.44, the hardness of the NbzAlyNx coatings is reduced due to the formation of the soft hexagonal AlN phase. In addition, the coatings exhibit interesting tribological properties: the coefficient of friction is in the range of 0.74 to 0.85, and wear rate is in the range of 4.8–9.1 × 10− 6 mm3/Nm. Thermal stability shows a dependence on the Al content; specifically, the Nb0.33Al0.17N0.50 coating was found to be thermally stable up to 700 °C.

Sputter deposited AlScN films with an Sc content of 38 at. % were investigated by X-ray diffraction and electron microscopy to study the influence of the radio frequency (RF) bias on the growth of abnormally oriented grains (AOG). Scanning electron microscopy investigations showed that the nucleation and growth of AOGs occurs with applied negative RF-bias till 4 W (51 mW/cm2), while the complete loss of AOGs happens at biases larger than 6 W (76 mW/cm2). The lack of AOGs within the film occurs together with the loss of the preferred (0001)-texture. At high bias powers, the (0001)-texture nucleates due to the strong (111)-texture of Pt-layer, but grain orientation becomes random during growth. The change of film microstructure with higher biases is reflected in the decay of piezoelectric properties. The concentration of trapped Ar atoms into the films increased with increasing bias power. The variation of the Ar-content along the film cross-section was ascribed to RF bias instabilities.

Chemical Beam Vapour Deposition is a gas phase deposition technique, operated under high vacuum conditions, in which evaporated chemical precursors are thermally decomposed on heated substrates to form a film. In the particular equipment used in this work, different chemical beams effuse from a plurality of punctual precursor sources with line of sight trajectory to the substrate. A shadow mask is used to produce 3D-structures in a single step, replicating the apertures of a stencil as deposits on the substrate. The small gap introduced between substrate and mask induces a temperature difference between both surfaces and is used to deposit selectively solely on the substrate without modifying the mask, taking advantage of the deposition rate dependency on temperature. This small gap also enables the deposition of complex patterned structures resulting from the superposition of many patterns obtained using several precursor beams from different directions through a single mask aperture. A suitable process parameter window for precursor flow and substrate temperature is evidenced to maximize resolution. (C) 2015 Elsevier B.V. All rights reserved.

Micro-Raman spectroscopy is a convenient tool to probe individual objects with a feature size on the submicron scale. The phase, composition, and orientation of Pb(Zr,Ti)O-3 fibers fabricated via hydrothermal processing have been characterized by this technique, with the working principles given in the paper. It is shown that the prepared PZT subrnicron fibers are of a tetragonal pervoslcite phase, with Zr/(Zr + Ti) varying from 0.05 to 0.25. The spontaneous polarization has been confirmed to be along the length direction and one of its {1 0 0} planes parallel to the substrate plane. (C) 2014 Elsevier Ltd. All rights reserved.

A five-layer stack of lead zirconate titanate (PZT) thin films with Pt electrodes was fabricated for potential applications in nanoactuator systems. The 1 mu m thick PZT films were deposited by a sol-gel technique, the platinum electrodes by sputtering. The PZT films were crack-free, in spite of the use of silicon as a substrate, suggesting an increased toughness of the metal-ceramic composite. For piezoelectric characterization, the intermediate electrodes were liberated by successive etching of the PZT and Pt layers, obtaining a functional three-layer stack. A total thickness change of 5.2 nm was achieved with 10 V, measured by double beam laser interferometry. The small signal response was obtained as 0.49 nm/V. Finite element simulations were made to account for the thickness change in the substrate due to the transverse piezoelectric effect. The average response corresponds to an average d(33,f) of 120 pm/V. The multiple annealed buried layers show clearly a better performance with up to 175 pm/V. It is concluded that the electrode interfaces in the interior exhibit higher qualities, as supported by transmission electron microscopy, and that the multiple anneals were beneficial for PZT thin film quality.

The formation mechanism of hydrothermally grown monocrystalline ferroelectric PZT nanowires is investigated. It is shown that the growth proceeds via a two-step process. Particles of the centrosymmetric PX-phase grow initially, having a fibrous morphology which is compatible with the highly anisotropic crystalline structure of this material. In the second stage, the PX-phase transforms into the ferroelectric perovskite phase, retaining the initial fibrous morphology. The solubility limit of Zr ions in the PX phase is maintained into the perovskite phase. While the PX and the perovskite phases have a similar composition, the reconstructive transformation process, in which edge-sharing octahedra chains of the PX-phase transform into a 3D network of corner sharing octahedra in the perovskite, involves incorporation and then release of oxygen (or hydroxyl). (C) 2012 Elsevier B.V. All rights reserved.

The fibrous PX-phase of lead titanate (PT), which can be synthesized by a hydrothermal method, has been studied to clarify its structural aspects on the atomic level. By combining synchrotron X-ray diffraction and electron microscope analysis with a first-principles calculation, a unique open-channel structure with a 5.529 angstrom diameter bore through the whole wire is determined. First-principle modeling reveals that the PX-phase structure has an indirect wide band gap and a higher formation enthalpy than the tetragonal perovskite phase. Both the frequency and symmetry of Raman-active lattice vibrational modes have been identified with polarized Raman spectra on individual monocrystalline PX-phase PT wires, showing a good match with the first-principles calculation. Furthermore, the doping of Zr in the PX-phase PT and the influence on the structure were investigated, showing a limit of 17% incorporation of Zr in the PX-phase PT.

Sputter deposited Al(1-x)ScxN thin films with a Sc content from x = 0 to 43 at% are investigated by electron microscopy in order to study and explain the formation and growth of abnormally oriented grains (AOG). It is found that the latter did not nucleate at the interface with the substrate, but at high energy grain boundaries, at which systematically higher Sc concentrations are detected. The AOGs are thus formed during the growth of c-textured grains. They grow faster than those, and finally protrude from the c-textured film surface, having at their end a pyramidal shape with three facets of a hexagonal wurtzite crystal: one (0001) and two (112 over bar 0) facets. Process conditions favoring less compact grain boundaries, and lower surface diffusion across grain boundaries are thought to promote nucleation of AOGs. Finally, a 4-step growth mechanism explaining the nucleation from a Sc-rich complexion and proliferation of AOGs with increasing film thickness is proposed.

Yttria stabilized zirconia (YSZ) with 8 mol% Y was deposited by reactive magnetron sputtering onto oxidized (100) silicon substrates. It was possible to switch film texture from (111) to (200) by applying a strong RF substrate bias. Transmission electron microscopy showed that the film deposited under bias is porous and exhibits nanoscaled grains. whereas the film deposited without bias is dense and columnar. The ionic conductivity as a function of temperature revealed an activation energy of 1.04 eV. The mechanical stress could be tuned to low values by thermal post-annealing. Using the dense (111) film as electrolyte layer, and the porous (200) film as an interlayer to a porous Pt anode, an open circuit voltage of 0.85 V was obtained in a micro machined fuel cell structure. (C) 2009 Elsevier B.V. All rights reserved.

By addition of Si to a binary transition metal nitride MN (e.g. TiN, ZrN, NbN, CrN), the hardness, thermal stability and chemical inertness of films have been considerably improved. The formation of a ternary M–Si–N ternary phase is possible under specific conditions such as low temperature, high deposition rate and low nitrogen pressure. The formation of nanocomposite materials (e.g. crystallites of MN + a thin layer of SiNx) is also possible under a wide range of deposition conditions. In such nanocomposite thin films the crystallite sizes are on the order of a few nanometers. The grain surfaces and boundaries have an important effect on the physical properties. The arrangement and chemical composition of the so-called “amorphous” minority phase (SiNx) are crucial for electrical and mechanical properties. The location, composition and thickness of the amorphous phase must therefore be known precisely. Their experimental determination is challenging due to the small concentration and in particular the geometry of the “amorphous” phase: approximately one monolayer either completely or partially covering the MN nanocrystallites. TEM investigations on such composites are known to have their limitations. It will be shown that the electrical resistivity, measured as a function of temperature, provides an experimental means for following the thickness evolution of the SiNx coverage layer, in such nanocomposite films.

Multilayered niobium oxynitride films were deposited onto (100) Si using DC magnetron sputtering with a reactive gas pulsing process. The argon and nitrogen flows were kept constant during sputtering of a pure niobium target and the oxygen flow was pulsed during deposition. Pulse durations of T = 10, 40 and 100 s and duty cycles α = tON / T of 0.3, 0.6 and 0.9 were chosen (tON = injection time of high oxygen flow). A mounting triangle was used as the pulse shape for the oxygen injection. During thin film deposition the cathode voltage, Ucath, the O2 and N2 partial pressures, p(O2) and p(N2), were recorded. A delay of both parameters (Ucath, p(O2)) was observed after each pulse, for the return to the values during tOFF = T − tON (off-time of oxygen injection with high flow). High resolution scanning electron microscopy revealed a multilayered structure for coatings deposited with T = 40 and 100 s. Transmission electron microscopy was used to verify that also the coatings with T = 10 s possess a multilayered structure with a period of λ = 10 nm. Despite this low period small crystallites (< 7 nm) were present in these layers. The indentation hardness and the Youngs modulus were in the range of 8.3–16.5 GPa and 154–180 GPa, respectively.

DC reactive magnetron sputtering was used for the deposition of Zr–Si–N thin films. Four series of samples have been deposited at various substrate temperatures TS: 300 K, 510 K, 710 K and 910 K. Depending on TS, different N2 partial pressures pN2 were required to obtain nearly stoichiometric ZrN films. Si content (CSi) was varied in each series by changing the power applied on the Si target, whereas the power on the Zr target was kept constant. The microstructure of the coatings was examined by XRD and in cross-section by transmission electron microscopy (TEM). Depending on TS and pN2, the deposition rate showed significant variations from 0.04 to 0.18 nm/s. The correlation between film morphology (preferential orientation of crystallites, grain size, column dimensions, thickness of the SiNx layer covering ZrN crystallites) and the deposition conditions (power applied on Si target, temperature, nitrogen partial pressure and deposition rate) provides useful information for optimizing the deposition process.

Thin films of M–X–N (M stands for early transition metal and X = Si, Ge, Sn) are studied as protective coatings. To extend the knowledge about the formation of nanocomposite films, various M–X–N systems have been compared. Ti–Si–N, Ti–Ge–N, Ti–Sn–N, Nb–Si–N, Zr–Si–N and Cr–Si–N thin films were deposited by reactive magnetron sputtering, from confocal targets in a mixed Ar/N2 atmosphere. The chemical reactivity of germanium and tin with nitrogen is significantly lower than that of Si and Ti. Therefore, the Ti–Ge–N and Ti–Sn–N systems are different from Ti–Si–N. Important changes in the morphology and structure of M–X–N films are induced by X addition. Nanocrystalline composite films are formed in all these investigated ternary systems. As a function of increasing X content (CX), the size of the crystallites D in the Ti–Si–N, Ti–Ge–N, Nb–Si–N and Zr–Si–N films decreases (from tens of nm to 2 nm) following the relationship CX ∼ 1 / D. The segregation of X atoms on the MN crystallite surface is responsible for the limitation of their growth. It results in the formation of a SiNy or TiGey amorphous phase on the crystallite surfaces. In the case of Nb–Si–N and Zr–Si–N systems, Si atoms can substitute metal atoms in the cubic MN lattice up to a critical concentration (solubility limit). Ti–Si–N, Ti–Ge–N and Ti–Sn–N systems are different: no solubility of Si, Ge and Sn in the TiN lattice is observed. For every composite film, the morphology changes result in a maximum hardness value at a typical concentration 2 ≤ CX ≤ 12 at.%. Resistivity measurements provide experimental mean for determining the limit of Si solubility in M–Si–N ternary systems and for following the thickness evolution of the SiNy coverage layer in the composite films.

DC reactive magnetron sputtering was used for the deposition of Nb–Si–N thin films at 250 °C substrate temperature. Si content was varied by changing the current applied on the Si target, whereas that on Nb target was kept constant. The evolution of morphology, grain size and lattice constant has been analyzed by Transmission Electron Microscopy and X-rays diffraction investigations. Hardness, stress and resistivity measurements provide complementary information concerning the macroscopic properties of the films. In the Nb–Si–N films, 3 distinct concentration regions have been observed depending on the Si content. For low Si content ( C Si ≤ 4 at.%) the Si atoms substitute the Nb atoms in the NbN lattice. Exceeding the solubility limit, a nanocomposite film grows; it is made of NbN:Si nanocrystallites surrounded by an amorphous SiN y layer. Further increase of Si content ( C Si ≥ 7 at.%) implies a reduction of the crystallite size, while the thickness of the SiN y layer at the crystallite surface remains constant (∼ 1.3 monolayer). The amount of the SiN y amorphous phase in the films increases through the increase of the surface to volume ratio of the crystallites. The structure of the films is responsible for the increase of hardness from 25 to 34 GPa through a 2-step mechanism, i.e., by forming a solid solution of Si atoms in NbN lattice and by forming a nanocomposite material. The large variation of the temperature coefficient of resistivity is well correlated with the thickness of SiN y layer on the NbN:Si crystallite surface. Based on the three concentration regions, a three-step model is proposed for the film formation of the Nb–Si–N thin films. This model correlates nanoscale structures with macroscopic properties of the films.

The thermal stability of the metastable fcc Zr 1 − x Al x N thin films has been investigated by heating the samples in ultra high vacuum ( P − 7 Pa). For this purpose, two films with chemical composition Zr 0.65 Al 0.35 N and Zr 0.57 Al 0.43 N were grown by reactive magnetron sputtering. The films were heated for duration of 60 min between 400–850 °C by steps of 50 °C. The structural evolution of the annealed films has been investigated by using X-ray diffraction (XRD), transmission electron spectroscopy (TEM) and by atomic force microscopy (AFM). Results show that up to annealing temperature of 600 °C the pristine structural and mechanical properties of all the films are retained. At annealing temperatures above 600 °C, important structural modification result as deduced from the shift of the XRD peaks towards the low 2θ values indicating changes in the unit cell dimension. Structural modifications are accompanied by hardness enhancement. In Zr 0.57 Al 0.43 N films annealed at 850 °C, chemical analysis by X-ray energy dispersive spectrometry evidenced Al-rich regions inhomogeneously distributed in the plane of the film. The results are discussed in terms of the transformation of the fcc Zr 1 − x Al x N structure in a two-phase system composed of Al-poor Zr 1 − x Al x N and low crystallized h-AlN via spinodal decomposition.

Thin films of TM–X–N (TM stands for early transition metal and X = Si, Al, etc.) are used as protective coatings. The most investigated among the ternary composite systems is Ti–Si–N. The system Ti–Ge–N has been chosen to extend the knowledge about the formation of nanocomposite films. Ti–Ge–N thin films were deposited by reactive magnetron sputtering on Si and WC–Co substrates at T s = 240 °C, from confocal Ti and Ge targets in mixed Ar/N 2 atmosphere. The nitrogen partial pressure and the power on the Ti target were kept constant, while the power on the Ge target was varied in order to obtain various Ge concentrations in the films. No presence of Ge–N bonds was detected, while X-ray photoelectron spectroscopy measurements revealed the presence of Ti–Ge bonds. Transmission Electron Microscopy investigations have shown important changes induced by Ge addition in the morphology and structure of Ti–Ge–N films. Electron Energy-Loss Spectrometry study revealed a significant increase of Ge content at the grain boundaries. The segregation of Ge atoms to the TiN crystallite surface appears to be responsible for limitation of crystal growth and formation of a TiGe y amorphous phase.

The electronic structure of hexagonal β-Nb 2 N and δ′-NbN, and cubic fcc δ-NbN, grown by magnetron sputtering, have been investigated by X-ray photoemission spectroscopy and ellipsometric measurements. The valence band (VB) energy distribution curves (EDC) of these nitrides significantly differ each from each other. The hybridized N2p–Nb4d bands of β-Nb 2 N originate a featureless peak centered at 6 eV below the Fermi level, those of the δ′-NbN are characterized by two narrow peaks centered at 5 eV and 6.5 eV. Striking changes are also observed in the EDCs near the Fermi level, these features are associated with the nearly metallic Nb4d states. The dielectrical function of these nitrides reveals structures near the screened plasma edge which correlate well with their associated electronic structure. The dielectric function spectra can be used in the phase identification of the hexagonal and fcc phases. Comparing hexagonal and fcc electronic structures, both β-Nb 2 N and δ′-NbN are more covalent that the cubic δ-NbN. The prominent covalent bonding in these hexagonal nitrides can be related to their higher hardness values compared to that of the cubic phase.

Ti–Ge–N single-layer and TiN/GeN-multilayer thin films were deposited by reactive magnetron sputtering on Si and WC–Co substrates at constant temperature T s = 240 °C, from confocal Ti and Ge targets in a mixed Ar/N 2 atmosphere. The nitrogen partial pressure, the TiN deposition time t Ti and the power on the Ti and Ge targets were kept constant. In order to obtain various GeN layer thicknesses in the films, the deposition time ratio t Ge / t Ti was varied. TiN/GeN multilayer films with TiN thickness ∼ 5 nm and various GeN thicknesses between 0.5 and 5 nm were deposited. A nanocrystalline multilayer film is formed, where the suppression of crystal growth is controlled by the successive deposition of two phases. TEM investigations revealed important changes induced by GeN x thickness variation: the columnar single-layer morphology switches into a multilayer morphology. The critical GeN thickness for changing the type of morphology is controlled by the diffusion of Ge atoms at the TiN crystallite boundaries. The morphology modification from single-layer to multilayer type determines the film hardening. Electron probe microanalyses (EPMA), scanning tunneling microscopy (STM), transmission electron microscopy (TEM), nanoindentation and X-ray diffraction (XRD) techniques were employed to characterize single- and multilayer films. The properties of alternate-deposited films are compared to those of co-deposited ones and interpreted.

Indium Tin Oxide (ITO) thin films have been deposited by the Sol–Gel Dip-Coating technique, the starting solutions being prepared from chlorides. These multilayered films were crystallized by means of a classical heat treatment at temperatures ranging from 500 to 600 °C. Five stacked layers are necessary to obtain a global electrical resistivity value of 2.9×10 −3 Ω cm, for 500 °C annealed film. The paper focuses on the study of the structure of such multilayered deposits, and on the densification process, using transmission electron microscopy, Rutherford Back-scattering Spectrometry and electrical resistivity measurements. This analysis reveals structural inhomogeneities and different crystallite growth processes as a function of annealing temperature and number of deposited layers.

Synchrotron X-ray diffraction (XRD) measurements of Pb-Ti-O fine acicular crystals (nanowires) of the so-called PX-phase have been performed. The theta-2 theta patterns of the nanowires dispersed on substrates with two different geometries indicated that the PX-phase Pb-Ti-O nanowire has [1 1 0] along its short axis and [0 0 1] along its longitudinal axis. Using a focused micro-X-ray beam, we first demonstrated the XRD analysis of a single nanowire of PX-phase Pb-Ti-O. Bragg reflections from the same single nanowire with scattering vectors at two different angles suggested its tetragonal unit cell having the rather large a-axis lattice constant. (C) 2010 Elsevier Ltd. All rights reserved.

e report an investigation concerning the influence of ion bombardment on the nanostructure and physical properties of Zr–Si–N nanocomposite thin films. The films were deposited by reactive magnetron sputtering from individual Zr and Si targets. The Si content was varied by changing the power applied to the Si target. The increase of ion bombardment energy was obtained by applying a negative potential Ub = − 150 V to the substrate. The evolution of the film texture, grain size and lattice constant was mapped out using X-ray diffraction measurements. Zr–Si–N films deposited at a substrate temperature Ts = 510 K with a bias voltage of Ub = − 150 V exhibit less pronounced columnar structure with small crystallites having various orientations. The maximum nanohardness of 39 GPa is reached for the films at about 2.5 at.% Si, 8 nm grain size and 0.3 Si surface coverage. The increased energy of ionic species reaching the substrate when a negative bias voltage is applied seems to have the opposite effect to that of increasing substrate temperature: reduced SiNx coverage on the ZrN nanocrystallites.