Search

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.

“Sybilla” equipment has been developed for two decades to propose solutions to the challenges faced by the very promising and expanding field of oxide thin film deposition. The underlying technology named Chemical Beam Vapor Deposition (CBVD) inherits its basic concept from Chemical Beam Epitaxy (CBE), and consists in effusing (in high vacuum conditions) beams of organometallic compounds towards a substrate on which they decompose under energy activation to form the film. The technique enables deposition of multi-element oxides (up to 3 was tested, up to 5 possible), either homogenously or in combinatorial mode (i.e with controlled precursor flow gradient emitted onto the substrate, in good agreement with theoretical model predictions). High homogeneity films can be achieved, even on large substrates (scaling between 150 mm and 450 mm wafer was shown). Precursor decomposition can be initiated either thermally (substrate heating) or by irradiating with energetic beams (laser and electron activations were studied). Additive growth can be obtained by such localized irradiation, or alternatively depositing through shadow masks and benefiting from the line-of-sight nature of the technique (and exploiting the precursor decomposition kinetics not to damage masks). The multi-parameter nature of the deposition technology (precursor nature, different flows, temperature) allows to tune growth rate (from few nm/h to several μm/h) as well as thin film physico-chemical properties (chemical composition, film morphology, crystallinity, etc.) and functional properties. Combinatorial growth reveals a very efficient facility to optimize processes (in one shot, saving time and resources) and address new thin film architectures.

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.

High quality optical thin film materials form a basis for on-chip photonic micro- and nano-devices, where several photonic elements form an optical circuit. Their realization generally requires the thin film to have a higher refractive index than the substrate material. Here, we demonstrate a method of depositing amorphous 25% Si doped TiO2 films on various substrates, a way of shaping these films into photonic elements, such as optical waveguides and resonators, and finally, the performance of these elements. The quality of the film is estimated by measuring thin film cavity Q-factors in excess of 10^5 at a wavelength of 790 nm, corresponding to low propagation losses of 5.1 db/cm. The fabricated photonic structures were used to optically address chromium ions embedded in the substrate by evanescent coupling, therefore enabling it through film-substrate interaction. Additional functionalization of the films by doping with optically active rare-earth ions such as erbium is also demonstrated. Thus, Si:TiO2 films allow for creation of high quality photonic elements, both passive and active and also provide access to a broad range of substrates and emitters embedded therein.

Gadolinium doped ceria is a well-known oxygen ion conduction material for solid fuel cell electrolytes. With its centrosymmetric average lattice and relatively low bulk dielectric constant it does not look interesting for electromechanical applications. However, a giant electrostriction (ES) effect was recently found in Ce0.8Gd0.2O2-X thin films. It was explained by the dynamic response of oxygen vacancies to an external electric field. In this work, the giant ES response has been reproduced in sputter deposited thin films. The proper transverse bulk ES coefficient has been derived from the measured clamped value. For this purpose, the Young's modulus was measured by nanoindentation. The highest ES coefficient was found as 9.0 x 10(-19) (m/V)(2) for the strain coefficient, and 2.3 x 10(-7) N/V-2 for the effective stress coefficient. Specific growth conditions must be chosen in order to obtain a microstructure exhibiting the giant ES effect. There is evidence for a higher oxygen deficiency than needed to compensate the gadolinium dopants (Gd'). It was observed that the nature of the bottom electrode impacts on the size of the effect. The highest response was obtained at films grown on Al bottom electrodes. To learn more on the mechanisms of the giant ES effect, a bipolar cycling was performed to test the delay time for the ionic reorientation in changing the sign of polarization, as observed in the stress loop. The maximal response was observed below 100 Hz in this bipolar mode, showing that the time for 180 degree reorientation amounts to several milliseconds. (C) 2016 Acta MateriaIia Inc. Published by Elsevier Ltd. All rights reserved.

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.

Deposition of nano-composite Mg–F–Si–O films on optical grade silica glass was studied employing RF magnetron co-sputtering from magnesium fluoride (MgF2) and fused silica (SiO2) targets. The aim was to obtain a stable and reliable sputtering process for optical coatings exhibiting a refractive index lower than the one of quartz glass (1.46 at 550 nm) without adding gaseous fluorine to the deposition process. The two magnetrons were installed in a confocal way at 45° off-axis with respect to a static substrate, thus creating a lateral gradient in the thin-film composition. The deposited Mg–F–Si–O coatings were structurally analysed by electron dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The obtained films consist of MgF2 nanocrystals embedded in a SiO2-rich amorphous matrix. Spectroscopic ellipsometry and spectrophotometry measurements showed that they are highly transparent exhibiting a very-low extinction coefficient k and a refractive index n in the desired range between the one of MgF2 (1.38) and SiO2 (1.46). Films with n = 1.424 and 1.435 at 550 nm were accomplished with absorption below the detection threshold.

In this work, we study MgF2 thin-film synthesis by reactive pulsed DC magnetron sputtering from a metallic magnesium target in a gas mixture of argon, oxygen, and carbon tetrafluoride (CF4). Nanocrystalline films on silicon and glass substrates with excellent properties for optical application are achieved. The plasma discharge is analyzed with a differentially pumped mass spectrometer before and during the deposition process. Without breaking the vacuum, monochromatic photoelectron spectroscopy (XPS) is performed for in situ determination of the atomic C and O concentration. Film microstructure, topography, and thickness are investigated by electron microscopy (SEM and TEM), atomic force microscopy (AFM), and X-ray diffraction (XRD). The optical constants n and k are determined by spectroscopic ellipsometry and spectrophotometry: a consistent parametric fit of the ellipsometric angles and spectral transmittance and reflectance based on three Lorentz oscillators to determine n and k is achieved for a wide spectral range (300–2 300 nm). At 550 nm, a refractive index of 1.382 and near-zero absorption is obtained, which is in excellent agreement with n = 1.383 of polycrystalline MgF2. The measured light reflection at 760 nm is reduced by 3% for a quarter-wave nanocrystalline MgF2 coating on glass compared to the uncoated glass substrate.

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.

Unique properties of domain walls in ferroelectrics have been recently discovered but methods of their controlled engineering remain underdeveloped. Here we investigate the domain structure of Bi0.9La0.1FeO3 epitaxial thin films with piezoelectric force microscopy and transmission electron microscopy. We show that with increasing Bi0.9La0.1FeO3 thickness, a transition from randomly-oriented 71° domain walls to 109° domain walls stripe occurs. At intermediate thicknesses, 71° and 109° domain walls coexist together with non-ferroelastic 180° domain walls. TEM cross-section images show complex domain structure due to the interplay between electrostatic constrains imposed by the SrRuO3 electrode and mechanical constrains imposed by the DyScO3 substrate.

Partial substitution of Al by Sc in AlN wurtzite films leads to a strong enhancement of the piezoelectric properties as long as the wurtzite phase is maintained. This is very promising for improving piezoelectric MEMS devices and enlarging their application range. Nucleation of (0001)-AlScN works particularly well on Pt (111) thin films. However, in some applications, the growth on insulating substrates may be required. Even though AlN can be grown well oriented on smooth amorphous surfaces of SiO 2 , it is not the case for AlScN. AlN seed layers are an evident solution when there is no vacuum break between the AlN and AlScN growth. However, when a vacuum break is unavoidable, an oxide layer is formed on AlN, which makes the “regrowth” difficult. In this contribution we show that a mild RF etch can solve the problem.

Aluminium scandium nitride (ASN) exhibits a largely enhanced piezoelectric response as compared to aluminium nitride (AlN), which makes it an upcoming piezoelectric material for use in next generation RF filters, sensors, actuators and energy harvesting devices. In this work, process-microstructure-property relationships of such sputtered ASN films containing up to 42 at% Sc were investigated. Hereby, the influence of the process parameters on the film structure, the intrinsic stress and the piezoelectric response were carefully investigated. A high piezoelectric response (e(31),(f) = -2.67 C/m(2) and d(33,f) = 10.3 pm/V) was measured for films with 42 at% and 34 at% Sc, respectively. The results are very promising towards industrial applications.

It is more difficult to nucleate AlN-ScN alloy thin films (AlScN) in pure (0001)-texture than it is with pure AlN thin films. AlN thus can serve as seed layer for AlScN. Equipment limitations may lead to the problem of a vacuum break between AlN and AlScN deposition, as it leads to oxidation of the AlN surface. This issue was studied with high resolution TEM and electron diffraction. The formed oxide layer disturbed a lot the epitaxial growth, leading to additional grain orientations. A mild RF etching step introduced before AlScN deposition was able to remove the oxide layer, and allowed for growing Al 0.84 Sc 0.16 N in local epitaxy on AlN, as shown by Hyper map EDX images. The resulting AlScN films show a pure (0001) texture. Double beam laser interferometry and finite element modeling were used to determine d 33, f of both layers together as 6.6 pm/V, and of 6.85 pm/V for AlScN alone when using the standard value of 3.9 pm/V for pure AlN. At the same time, the relative dielectric constant of Al 0.84 Sc 0.16 N was determined as 14.1.

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.

Charged domain walls in ferroelectric materials are of high interest due to their potential use in nanoelectronic devices. While previous approaches have utilized complex scanning probe techniques or frustrative poling here we show the creation of charged domain walls in ferroelectric thin films during simple polarization switching using either a conductive probe tip or patterned top electrodes. We demonstrate that ferroelectric switching is accompanied - without exception - by the appearance of charged domain walls and that these walls can be displaced and erased reliably. We ascertain from a combination of scanning probe microscopy, transmission electron microscopy and phase field simulations that creation of charged domain walls is a by-product of and as such is always coupled to, ferroelectric switching. This is due to the (110) orientation of the tetragonal (Pb,Sr)TiO3 thin films and the crucial role played by the limited conduction of the LSMO bottom electrode layer used in this study. This work highlights that charged domain walls, far from being exotic, unstable structures, as might have been assumed previously, can be robust, stable easily-controlled features in ferroelectric thin films.

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.

AlN thin films were grown by reactive sputtering on amorphous SiO2 thin films. Film texture, x-ray rocking curve width, mechanical stress, and the clamped piezoelectric constant d33,f were studied as a function of rf bias power and substrate roughness. A high d33,f of 5.0 pm/V was achieved at low substrate roughness and low mechanical AlN film stress. Increasing substrate roughness and stress leads to a deterioration of d33,f, which is correlated with a higher density of opposite polarity grains detected by piezoresponse force microscopy. Extrapolating to 100% uniform polarity, a d33,f of 6.1 pm/V is derived as highest possible value, probably corresponding to the d33,f=e33/c33E of perfect single crystalline material. Growth mechanisms are proposed and underlined by high resolution transmission electron microscopy to explain the observed phenomena.

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.

Replacing platinum as an oxygen reduction catalyst is an important scientific and technological challenge. Herein we report a simple synthesis of a complex carbon with very good oxygen reduction reaction (ORR) activity at pH 13. Pyrolysis of magnesium nitrilotriacetate yields a carbon with hierarchical micro/meso/macro porosity, resulting from in situ templating by spontaneously forming MgO nanoparticles and from etching by pyrolysis gases. The mesopores are lined with highly graphitic shells. The high ORR activity is attributed to a good balance between high specific surface area and mass transport through the hierarchical porosity, and to improved electronic conductivity through the graphitic shells. This novel carbon has a high surface area (1320 m(2) g(-1) ), and high nitrogen content for a single precursor synthesis (∼6 %). Importantly, its synthesis is both cheap and easily scalable.

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.

Defect engineering is one of the cornerstones of the modern electronics industry. Almost all electronic devices include materials that have been doped by ion bombardment. For materials where crystallinity is essential, such as ferroelectrics, defect type and concentration can vastly influence properties and are often used to optimize device performance. This study shows a method to effectively control the density and position on the nanoscale of defect sites in thin films of Pb(Zr,Ti)O3 via focused ion beam microscopy. This allows for exceptional clarity of observation of the role of defects in nucleation, polarization switching, and domain wall interaction through investigation with piezoresponse force microscopy and transmission electron microscopy, adding insight to accepted but seldom-demonstrated facts on defect-induced effects. This nanoscale defect engineering can be used as a tool to control material properties, and furthermore, a route is demonstrated toward a practical application.

In the pursuit of ferroic-based (nano) electronics, it is essential to minutely control domain patterns and domain switching. The ability to control domain width, orientation and position is a prerequisite for circuitry based on fine domains. Here, we develop the underlying theory towards growth of ultra-fine domain patterns, substantiate the theory by numerical modelling of practical situations and implement the gained understanding using the most widely applied ferroelectric, Pb(Zr, Ti)O-3, demonstrating controlled stripes of 10 nm wide domains that extend in one direction along tens of micrometres. The observed electrical conductivity along these thin domains embedded in the otherwise insulating film confirms their potential for electronic applications.

Sol-gel HfO2 thin films, prepared from etoxid precursor, were deposited onto silicon wafer substrates by dip-coating. Low fluence multipulse excimer laser processing was used for sol-gel film densification. The small duration of the laser pulse heating limits the quantity of oxygen atoms arriving from the surface at the HfO2/Si interface. Laser irradiations were performed using a XeCl (308 nm) excimer laser, with a homogeneous laser beam. The nanostructure evolution of the laser irradiated films, using different laser fluences between 30 and 120 mJ/cm2 and different number of pulses, was studied by systematic cross section transmission electron microscope (XTEM) observations. Dielectric constant measurements were performed on the sol-gel HfO2 films samples after laser annealing. The optimum laser processing conditions were found to be a laser fluence of 80 mJ/cm2 and 5000 to 10000 laser pulses. In these conditions, uniform densified HfO2 amorphous films with a dielectric constant of about 25 were obtained.

While there is extensive literature on the influence of both compressive and tensile strain on the domain patterns of (001) tetragonal ferroelectric thin films, little is known regarding domain engineering in (110) films. The primary reason is the absence of suitable substrates that allow the growth of epitaxial films with this orientation. However, recent works emphasized the importance of this orientation with the possibility for e.g. to achieve ultra-high ferroelectric domain density. This work reports the controlled growth of a/c domain patterns in highly tetragonal monocrystalline (110) oriented Pb(Zr-0.05, Ti-0.95)O-3. It is demonstrated that while a/c patterns can easily be realized in the single layer film relaxed under compressive misfit strain, modulation of tensile misfit strain through the use of buffer layers allows for consistent control of domain periodicity, in which case the average domain period was tuned between 630 and 60 nm. The effects of domain density and defects on both switching behavior and piezoelectric properties in single and multilayered structures are also investigated, revealing an optimum composition of the buffer layer for improved domain compliance and piezoelectric properties. (C) 2016 Author(s).

Perpetual demand for higher transfer speed and ever increasing miniaturization of radio and microwave telecommunication devices demands new materials with high electrical tunability. We have investigated built in electrical and strain fields' influence on the electrical tunability in Ba0.7Sr0.3TiO3 thin film hetero-system grown by pulsed laser deposition technique. We observed the built in electrical field by local piezo-force microscopy (as deflected hysteresis loops) and macroscopic impedance analysis (as asymmetric tunability curves), with the calculated 88 kV/cm built in field at room temperature. Negative −1.4% misfit strain (due to clamping by the substrate) enhanced ferroelectric phase transition temperature in Ba0.7Sr0.3TiO3 thin film by more than 300 K. Built in fields do not deteriorate functional film properties—dielectric permittivity and tunability are comparable to the best to date values observed in Ba1−xSrxTiO3 thin films.

Combinatorial CBVD (Chemical Beam Vapor Deposition) is a thin film deposition technology which has the ability to produce multi-element thin films with large controlled composition spread gradients. If functional characterizations can be carried out systematically and rapidly on such graded films over full wafers, they enable to identify precisely the best film composition for a given application, and CBVD then easily allows for the deposition of the optimized film homogeneously on large wafers. In this article, we demonstrate the efficiency of such a process development based on the optimization of new Transparent Conductive Oxide thin films (TCO) of few % Nb doped TiO 2 . We have developed a full wafer metrology instrument which maps the optical thickness and the sheet resistance with a lateral resolution below 400um. We discuss the performance of various algorithms to extract the optical thickness from the white light reflectance measurement in the case of very small thickness. The sheet resistance is measured with an array of four AFM-like conductive cantilevers, allowing accurate sheet resistance (R) measurement where the standard tungsten four probes destroy porous thin oxide films. Application of these measurements to several Nb doped TiO 2 films deposited on 4" wafer by CBVD is presented.

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.

We report a 2-step approach to prepare tetragonal perovskite PbZr(0.1)Ti(0.9)O(3) submicro/nano wires in gram scale and with over 95% wire content. Non-perovskite precursor wires were first fabricated by hydrothermal processing. A subsequent annealing in a PbO atmosphere at 600 degrees C converted these wires into perovskite structures which retain the one-dimensional shape. Binding of the perovksite nanowires to a conductive substrate could be achieved by a similar heat treatment of the non-perovskite precursor wires on a flat Pt coated substrate. Taking advantage of the strong mechanical attachment and good electrical contact between the wires and the metallic layer, piezoresponse force microscopy (PFM) was used to measure the local piezoelectric and ferroelectric properties of the individual wires. Enhanced piezoelectric response relative to sputtered epitaxial PbZr(0.2)Ti(0.8)O(3) film and squared hysterisis loop with sharp switching indicate pronounced electro-mechanical and ferroelectric behavior. The 90 degree domain structure of the as-prepared perovskite PZT wires was confirmed by both PFM and transmission electron microscopy investigations.

In this work, the lack of adhesion occurred during the up-scaling of the deposition of tribological coatings in a semi-industrial apparatus is interpreted. The adhesion problems were detected for both hard and self-lubricant coatings from W–Ti–N and W:C systems, respectively, when they were deposited in a 4 cathodes TEER® chamber by reactive unbalanced magnetron sputtering. In spite of cleaning the substrates surface by ion bombardment prior to deposition, by establishing a discharge close to the substrate, insufficient adhesion critical load values were measured by scratch-testing. A powerful set of complementary techniques was used to the detailed analysis of the interfaces in order to understand and overcome the adhesion problems: RBS gave some insights on the nature of the problem by detecting composition anomalies in the substrate/coating interface; Auger spectroscopy was used for identifying the underneath chemical composition close to the interface; cross section TEM gave the final evidence of the presence of a contamination layer attributed to malfunctioning of the ion cleaning process, which was the cause of the lack of adhesion.

The relative concentration of BaTiO3 and CeO2 is shown to control the inclination of composite growth. The oblique composite structures consist of tunable BaTiO3 nanofibers embedded in a CeO2 matrix, which lowers considerably the permittivity while significantly enhancing the tunable response to an electric field. This is of interest in reconfigurable microelectronics.

The use of interdigitated electrodes (IDEs) in conjunction with ferroelectric thin films shows many attractive features for piezoelectric MEMS applications. In this work, growth of {1 0 0}-textured lead zirconate titanate (PZT) thin films was achieved on insulating MgO buffered, oxidized silicon substrates. IDEs were fabricated by lift-off techniques and cantilevers were formed by dicing. The deflection upon application of a sweeping voltage was measured as large signal response in parallel to the ferroelectric polarization (PV loop). Likewise, the small signal piezoelectric response was measured in parallel to the capacitance-voltage (CV) measurement. In this way, a complete picture of the ferroelectric-piezoelectric element was obtained. From the deflection, the in-plane piezoelectric stress in the PZT thin film was derived and, from this, the effective piezoelectric coefficients. For the latter, two types were defined: an engineering type corresponding to the average value along the IDE, which can directly be compared to coefficient of a parallel plate electrode (PPE) capacitor and a second one that approximately yields the idealized coefficient governing between the electrode fingers. The IDE structures were experimentally compared with PPE structures of identical film thickness. The resulting coefficients were of opposite sign, as expected. In spite of a much better polarization loop, the IDE device showed a lower average piezoelectric stress. The estimated peak value between the fingers was about the same as in the PPE device, corresponding to about 20 C m(-2). Nevertheless, the result is very promising for cases where compressive piezoelectric stresses are required and for preventing cracking due to large piezoelectric tensile stresses in PPE systems.

The dependence of the formation of ferroelastic stripe domain patterns on the thermal history is investigated by detailed piezoresponse force microscopy and X-ray diffraction experiments after and during annealing of tensile strained tetragonal Pb(Ti,Zr)O-3 epitaxial thin films on DyScO3 substrates. In particular, the ferroelastic pattern is reversibly interchanged between a cross-hatched and a stripe domain pattern if the films are cooled at different rates after annealing above the formation temperature of a-domains. Different types of 180 degrees and non-180 degrees patterns can be created, depending on the thermal treatment. The changes in the 180 degrees domain structure and lattice parameters are attributed to a change of oxygen vacancy concentration, which results in a modification of the internal electric field and unit cell size, causing also a shift of T-C. Thermal treatment is done on rhombohedral La:BiFeO3 thin films as well. It is observed that also in these films, appropriate heat treatment modifies the domain pattern and films with a stripe domain pattern can be created, confirming the general validity of the developed model. (C) 2015 AIP Publishing LLC.

We have successfully applied laser annealing to sol–gel deposited SnO2:Sb thin films in order to achieve their crystallization. The as-deposited films are quasi-amorphous and electrically non-conductive. After laser annealing they crystallize and become conductive. This paper presents a comparative study of the laser annealed films and shows the influence of the irradiation parameters on the crystallization process and the electrical behavior of the films. Our results are quite promising in view of applying this kind of treatment to films deposited on thermally sensitive substrates (e.g. polymers).

This paper reports on the potentialities of sol-gel deposited Sb doped SnO 2 (T)) as a new transparent conducting oxide (TCO) for anode in organic light emitting diodes (OLED). Multilayered films with transparency over 85% and resistivity lower than 5 10 3 (Omega) -cm were obtained. Structural observations by Transmission Electron Microscopy (TEM) show that the films are nanocrystallized. Smaller and more uniform grains are obtained upon rapid thermal annealing. Atomic Force Microscopy (AFM) imaging shows the surface roughness does not exceed 20 A. TO films are very stable and cannot be chemically etched. Anode patterning by reactive ion etching (RIE) in a Methane- Hydrogen plasma has been experienced and is described. Typical etching around 250 A/min were obtained. TO/PEDOT/PVK/Al hole only diodes were realized to assess sol gel TO films as hole injection electrodes. Devices with threshold voltages of 6 volts were obtained. A comparison with ITO deposited by low temperature cathodic sputtering is given.

AlN films are employed in RF filters for wireless communication. We report on enhanced coupling factors kt2 obtained by partial substitution of Al by Sc. Al0.88Sc0.12N films were deposited by reactive magnetron sputtering from an Al0.9Sc0.1 alloy target. They grew in the piezoelectric wurtzite phase with a similar microstructure as pure AlN films. The clamped d33,f increased considerably from 5.1 to 7.8 pm/V. The admittance measured at thin film bulk acoustic wave resonators was fitted to an equivalent circuit model and to 2-dimensional finite element simulation, yielding a kt2 of 7.3% and a quality factor of 650. The material softens considerably.