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We present measurements of significant thermal diffusivity by surface electromagnetic waves of an ultra-thin polar and amorphous dielectric film deposited on silicon (Si). We used a photothermal-beam-deflection technique with a modulated mid-infrared heating source to excite and launch surface electromagnetic waves onto the surface of an amorphous silicon carbide (a-SiC) film deposited on Si and generate periodic temperature and refractive index gradients above the sample surface. These gradients are capable of periodically deflecting a probe beam, passing very close to the surface, at the modulation frequency of the heating beam. We have fitted the measured probe beam deflection to an analytical model for the mirage effect that takes into account the thermal anisotropy of the measured sample to infer the contribution of the surface electromagnetic waves of the a-SiC film to thermal diffusivity in the plane of the sample under study. We found that reducing the thickness of the a-SiC film promotes the interaction between the surface electromagnetic waves propagating on either side of the a-SiC film, which significantly enhances thermal diffusivity in the plane of the measured sample. We also found that in-plane thermal diffusivity by surface electromagnetic waves on an amorphous silicon carbide film a few nanometers thick is several orders of magnitude greater than thermal diffusivity by phonons in silicon. We believe that the results obtained provide a better understanding of the physics of electromagnetic waves confined to solid surfaces.

Electron-microscope investigations in situ, concerning the crystallization of amorphous films, are systematized. Based on the analysis of the structure and morphology of crystals growing in amorphous films as a result of electron beam influence, a quantitative interpretation of layer polymorphic crystallization (LPC), island polymorphic crystallization (IPC) and dendrite polymorphic crystallization (DPC) is given. For each crystallization mode the parameter of dimensionless relative length δ0, equal to the ratio of the characteristic length to the value, characterizing the size of the unit cell of the crystal, was respectively assigned. Based on the video recording of the process, the kinetic curves of LPC, IPC and DPC are constructed. LPC (Cr₂O₃, V₂O₃, Sb₂S₃, Se and others) is regarded as morphological analog of Frank-van der Merwe (FM) growth mode of a crystal from the vapor phase. In the case of LPC in the zone of observation in amorphous film grows a single flat crystal. By analogy with FM growth mode an energy criterion of the LPC can be written as σa≥ σc + σ>ac + εd, where σa is the free energy of the amorphous phase-vacuum interface, σc is the free energy of the crystalline phase-vacuum interface, σac is the free energy of the amorphous-crystalline phase interface, and εd is the energy of deformation of the growing crystalline layer. For LPS the quadratic dependence of the fraction of the crystalline phase x on time t takes place and δ0 ~ 2500-4700. IPC (Al₂O₃, ZrO₂, Ni, Re and others) is regarded as morphological analog of Volmer-Weber growth mode of a crystal from the vapor phase. In the case of IPC in the zone of observation in amorphous film grows a lot of small disoriented crystals. By analogy with VW growth mode an energy criterion of the IPC can be written as σa ≤ σc + σac + εd. For IPS the exponential dependence of x(t) takes place and δ0 ~ 100-900. DPC (films of Fe-C, HfO₂) is regarded as morphological analog of Stranski-Krastanov growth mode of a crystal from the vapor phase. A characteristic sign of DPC is the formation of dendrite branches along the sides of a flat single crystal. For DPC the quadratic dependence of x(t) takes place and δ0 ~ 3900.

Organisms in nature can alter the short-range order of an amorphous precursor phase, thereby controlling the resulting crystalline structure. This phenomenon inspired an investigation of the effect of modifying the short-range order within the amorphous phase of a selected material. Amorphous thin films of aluminum oxide deposited by the atomic layer deposition method were found to vary structurally as a function of size. Thinner films, as predicted and also confirmed by atomistic simulations, exhibited more 4 coordinated alumina sites. These atomistic alterations were expected to change the amorphous thin film average density. The density indeed varied with the alumina layer thickness, and the measured effect was even stronger than predicted theoretically. This effect is explained in terms of the deposition process, where each newly deposited layer is a new surface layer that remembers its structure, resulting in thin films of substantially lower density.

Based on the framework of long-range empirical formulas, the interatomic potentials were constructed for the Ni-Nb-Mo (fcc-bcc-bcc) and Ni-Zr-Mo (fcc-hcp-bcc) ternary metal systems. Applying the constructed potentials, atomistic simulations were performed to predict the energetically favored glass formation regions (GFRs) in the respective composition triangles of the systems. In addition, the amorphization driving forces (ADFs), i.e., the energy differences between the solid solutions and disordered phases, were computed and appeared to correlate with the so-called glass forming abilities. To verify the atomistic prediction, ion beam mixing with nano-multiple-metal-layers was carried out to produce ternary amorphous films. The results showed that the composition of ternary amorphous films obtained by ion beam mixing all locate inside the GFRs, supporting the predictions of atomistic simulations. Interestingly, the minimum ion dosage required for amorphization showed a negative correlation with the calculated ADF, implying that the predicted amorphization driving force could be an indicator of the glass formation ability.

Amorphous films of HfO₂ are prepared by laser ablation of Hf target in an oxygen atmosphere. Its crystallization was performed under the electron beam impact in a column of electron microscope. Formation and growth of HfO₂ crystals are investigated in situ. The transformation kinetic curves are plotted on the basis of a frame-by-frame analysis of the video recorded flick during the film crystallization. According to the structural and morphological features, the phase transformation corresponds to the dendrite polymorph crystallization and can be either single-stage or two-stage in nature. In the latter case, the size-phase effect takes place, consisting in the fact, that when the crystal of orthorhombic modification of HfO₂ reaches a critical size (~0.2 μm), it splits into domains with orthorhombic and monoclinic crystal lattices. The kinetic parameters of the crystallization are determined and it is shown, that the quadratic dependence of the fraction of the crystalline phase on time takes place. The average value of the relative length for the dendrite polymorphic crystallization is about 3075. The phase transition from the amorphous state to the crystalline one is accompanied by increasing of the relative density of matter of the film by about 2.5 %. The crystallized film consists predominantly of dendrites of the monoclinic modification of HfO₂.

Measurements of magnetization [M(H, T)] and anomalous Hall resistance [Rxy(H, T)] are performed over a broad range of magnetic field (H) and temperatures (T) on sputter deposited 10 nm thick films of (FeCo)1−xGdx. The Gd content (x) in the films was changed by varying the Gd source power from 20 W to 50 W, in steps of 5 W. The saturation magnetization (Ms) of these films at 300 K shows a distinct minimum for the source power of 40 W. Measurements of M(H) for the 40 W sample at several temperatures establish full compensation of the antiferromagnetically coupled magnetic sublattices of Gd and FeCo at Tcomp = 270 K ± 10 K. The approach to compensation is characterized by the emergence of perpendicular magnetic anisotropy (PMA) and a diverging coercive field. The Rxy (H) of this sample, as well as of those prepared at 30 W and 50 W, scales with M(H) at T > Tcomp and T < Tcomp. However, this scaling fails in the vicinity of Tcomp where the Rxy undergoes a sign reversal. Our analysis of these data in the framework of the existing models for Rxy(H, T) in ferrimagnets suggests that the role of spin disorder and its topological contribution to Rxy may be necessary to account for the observed behavior. A precise identification of Tcomp is also important to stabilize technologically useful non-trivial spin textures and PMA in these systems.

In this work we report the electrodeposition parameters of Sn-graphene films in aqueous solutions and silicon films in propylene carbonate. The galvanostatic electrodeposition of tin-graphene films from a sulfate-based acidic solution on copper substrates has been studied evaluating the effect of stirring on the morphology and the electrochemical performance. SEM analysis of films deposited galvanostatically at -10 mA.cm−2 for 20 minutes at 25 °C reveals that electrodeposition is suitable to generate continuous and homogeneous films with thickness values in the micrometer range. XRD analysis shows many intermetallic Cu-Sn crystalline phases are formed, as opposed to a pure amorphous tin layer. So far, electrochemical characterization has only been performed over a short number of charge-discharge cycles. The galvanostatic electrodeposition of silicon from propylene carbonate in galvanostatic mode has been carried out, but is currently extremely challenging to obtain continuous and homogeneous films. The XRD characterization has suggested the possible presence of amorphous phases in the films deposited at -1.0 mA.cm-2 for 30 minutes at 25 °C.\ud \ud

International audience; Laser Desorption Ionization Time-of-Flight Mass Spectrometry was exploited for the characterization of Ge-As-Se chalcogenide glasses and corresponding thin films fabricated using pulsed laser deposition. Main achievement of the paper is the determination of laser generated clusters' stoichiometry. The clusters observed were As-b(+) (b = 1-3), Se-2(-), binary AsbSe+ (b = 1-3), AsbSec- (b = 1-3, c = 1-4), Ge2Sec- (c = 2-3), As3Se2+, Ge2Asb- (b = 2-3), Ge3Asb- (b = 1-2), Ge3Se4-, As5Sec- (c = 4-5), GeAsSe4-, GeaAsSe5- (a = 1-4), GeAs2Se3-, GeAs3Se2-, Ge2As2Se2-, Ge2AsSec- (c = 6-7), and GeAs3Sec- (c = 5-6) (in positive as well as in negative ion mode). The stoichiometries of identified species are compared with the structural units of the glasses/thin films revealed via Raman scattering spectra analysis. Some species are suggested to be fragments of bulk glass as well as thin films. Described method is useful also for the evaluation of the contamination of chalcogenide glasses or their thin films.

Co-Fe-B films were prepared by electroless plating. As-deposited films were thermomagnetically treated in the applied magnetic field of 500 Oe with different field directions at 300°C for 1 hour. The effects of magnetic field direction of thermomagnetic treatment on the structure and magnetic properties of Co-Fe-B thin films were investigated. It is found that two phases existed in annealed Co-Fe-B films: one is weak crystallized CoFe phase, the other being amorphous phase. The surface morphologies of the treated films are found to be affected by the direction of thermomagnetic treatment field. The results also show that the magnetic properties of thermomagnetically treated films are influenced greatly by the treatment field direction.

Phonon spectroscopy measurements were used to examine the scattering of high frequency phonons (300 GHz-1 THz) in amorphous materials. The experiments were done with the use of time and frequency resolved measurements of the phonon transmission behaviour through amorphous single films of different thicknesses. The typical film thicknesses were of the order of 10 nm. In contrast to the pure amorphous semiconductors Si and Ge our experiments show inelastic phonon scattering processes in the case of SiO 2 and Si:H. This inelastic phonon scattering also occurs when the pure semiconductors Si and Ge are prepared in an O 2 or H 2 atmosphere, but is missing when the preparation process is done in an N 2 atmosphere. In films of the pure semiconductors a-Si and a-Ge we only found evidence to elastic scattering processes. In further experiments at heated a-Si:H samples we could examine the atomical bonded hydrogen to be the center of the inelastic phonon scattering.

The phase change processes of as-deposited Sb-Zn films were investigated. The as-deposited amorphous SbZn film showed an unusual increase in resistance during heating, which was attributed to crystallization of the metastable SbZn phase. Further heating up to more than 300oC resulted in a structural transformation into the stable SbZn phase accompanied by a drop in resistance as in conventional phase change materials. Even though off-stoichiometric Sb-rich films exhibited crystallization into the metastable phase as well, the precipitation of Sb crystalline grains caused an undesirable drop in resistance at temperatures lower than that of the SbZn film. A memory device using an SbZn film showed typical switching behavior and successfully switched from the amorphous to crystal state and vice versa by the application of an electric pulse. These results revealed that stoichiometric SbZn film is a promising novel phase change material for phase change memory with high thermal stability.

Köçkar, Hakan (Balikesir Author), Compositions. of Fe81B13.5Si3.5C2, Fe67Co18Si1B14 and Fe5.85Co72.15Mo2B15Si5 were deposited on to rigid and flexible substrates for the first time using a dc sputtering source as part of a novel Rotating Cryostat (RC). The films sputtered on silicon and glass show only isotropic magnetisation, whereas those sputtered on a polyimide (Kapton(TM)) substrate exhibited either isotropic or anisotropic magnetisation depending upon composition. Similar findings were obtained for equivalent evaporated films.

Thin transparent amorphous films of aluminum oxide have been obtained using PE MOCVD technique and aluminum β-diketonate as precursor in controlled mixture of gas reagents Ar and O 2 . The films were deposited on glass, quartz and stainless steel substrates at temperature range of 100-250°C. The correlation between electric properties and such deposition parameters as r.f. power Wp, the total gas pressure in chamber P o , O 2 partial pressure, the substrate temperature T, and gas carrier flow rate were determined. Optimal deposition conditions of Al 2 O 3 layers with high dielectric characteristics were established. Auger analysis showed that the composition of films obtained was stoichiometric. Auger depth profiles showed the existence of the transition area enriched with oxygen in the film/substrate heterostructure.

The fluctuating component of the flux‐flow voltage, δV(t), about the average voltage is measured in the low‐temperature (T) liquid phase of amorphous MoxSi1−x films. For the 100‐nm‐thick film δV(t) originating from the vortex motion is clearly visible in the quantum‐yortex‐liquid (QVL) phase, where the distribution of δV(t) is asymmetric, suggestive of the unusual vortex motion. For the 6‐ and 4‐nm‐thick films, in which the QVL phase is not determined from the resistance vs T curves, the similar unusual vortex motion is observed in nearly the same reduced‐T regime.

Lead halide perovskites are among the most exciting classes of optoelectronic materials due to their unique ability to form high-quality crystals with tunable bandgaps in the visible and near-infrared using simple solution precipitation reactions. This facile crystallization is driven by their ionic nature; just as with other salts, it is challenging to form amorphous halide perovskites, particularly in thin-film form where they can most easily be studied. Here, rapid desolvation promoted by the addition of acetate precursors is shown as a general method for making amorphous lead halide perovskite films with a wide variety of compositions, including those using common organic cations (methylammonium and formamidinium) and anions (bromide and iodide). By controlling the amount of acetate, it is possible to tune from fully crystalline to fully amorphous films, with an interesting intermediate state consisting of crystalline islands embedded in an amorphous matrix. The amorphous lead halide perovskite has a large and tunable optical bandgap. It improves the photoluminescence quantum yield and lifetime of incorporated crystalline perovskite, opening up the intriguing possibility of using amorphous perovskite as a passivating contact, as is currently done in record efficiency silicon solar cells.

International audience; Functionalizing the surface of chalcogenide films is of major interest due to the wide use of these materials in infrared integrated optics. A functionalization route via short peptides that has been already used for silicon, ZnSe and other semiconductors is applied to amorphous films of the ternary Ge-Se-Te system. The biotinylated 12-mer peptides LLADTTHHRPWT and SVSVGMKPSPRP were chosen and used to capture streptavidin. High-resolution atomic force microscopy images highlight that the 12-mer peptide LLADTTHHRPWT provides better interface layers for streptavidin molecule detection.

In-Sb-Te when is a thin film presents a huge difference in its electrical resistivity when transform from the amorphous (insulating) to the crystalline (conducting) phase. This property made this system one of the main phase-change materials used in the data storage industry. The change in the electrical conductivity is probably associated to a change in the bonding geometry of some of its constituents. To explore this point, we present in this work an study of the bonding geometry of In atoms in In-Sb-Te films by means of In K-edge X-ray absorption near edge structure (XANES) spectroscopy using synchrotron radiation in both as deposited (amorphous) and crystalline thin films obtained as a result of resistance (R) vs temperature (T) measurements. Comparison of the XANES spectra obtained for ternary amorphous films and binary crystalline reference films suggests that in amorphous films the bonding geometry of In atoms is tetrahedral-like. After the thermal annealing has been carried out the differences in the XANES spectra of the as deposited and the annealed films indicate that the bonding geometry of In atoms changes. Based on X-ray diffraction results and ab initio calculations in the framework of the Density Functional Theory (DFT) we show that the new coordination geometry is associated with a tendency of In atoms towards octahedral-like. Fil: Bilovol, Vitaliy. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Tecnologías y Ciencias de la Ingeniería "Hilario Fernández Long". Universidad de Buenos Aires. Facultad de Ingeniería. Instituto de Tecnologías y Ciencias de la Ingeniería "Hilario Fernández Long"; Argentina Fil: Gil Rebaza, Arles Víctor. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; Argentina Fil: Mudarra Navarro, Azucena Marisol. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; Argentina Fil: Errico, Leonardo Antonio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; Argentina Fil: Fontana, Marcelo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Tecnologías y Ciencias de la Ingeniería "Hilario Fernández Long". Universidad de Buenos Aires. Facultad de Ingeniería. Instituto de Tecnologías y Ciencias de la Ingeniería "Hilario Fernández Long"; Argentina Fil: Arcondo, Bibiana Graciela. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Tecnologías y Ciencias de la Ingeniería "Hilario Fernández Long". Universidad de Buenos Aires. Facultad de Ingeniería. Instituto de Tecnologías y Ciencias de la Ingeniería "Hilario Fernández Long"; Argentina

© 2019 IOP Publishing Ltd. Solid-state amorphization, the growth of an amorphous phase during annealing, has been studied in a wide variety of thin film structures. Whereas research on the remarkable growth of such a metastable phase has mostly focused on strictly binary systems, far less is known about the influence of impurities on such reactions. In this paper, the influence of nitrogen, introduced via ion implantation, is studied on the solid-state amorphization reaction of thin (35 nm) Ni films with Si, using in situ x-ray diffraction (XRD), ex situ Rutherford backscattering spectrometry, XTEM, and synchrotron XRD. It is shown that due to small amounts of nitrogen (

Thin-film transistors (TFTs) are the fundamental building blocks of today’s display industry. To achieve higher drive currents and device density, it is essential to scale down the channel lengths of TFTs. To be able to fabricate short-channel TFTs in large volumes is also equally important in order to realize lower fabrication costs and higher throughput. In this paper, we demonstrate the application of substrate conformal imprint lithography (SCIL) to pattern top-gate (TG) self-aligned (SA) amorphous indium gallium zinc oxide TFTs down to channel length ${L}_{\textsf {G}} = \textsf {450}$ nm with good device scaling properties resulting in average field-effect mobility ( ${\mu }_{FE}$ ) $= \sim 10$ cm $^{\textsf {2}}\cdot \text{V}^{-\textsf {1}}\cdot \text{s}^{\textsf {-1}}$ , ${V}_{\mathrm{ON}} = \,\sim 0.5$ V, and subthreshold swing (SS) $= \sim 0.3$ V/decade. The device performance as a function of channel length outlines the importance of dopant diffusion control for realizing submicrometer SA TFTs. The results demonstrate the compatibility of SCIL-based large-area patterning for the realization of submicrometer TG SA TFTs with a potential for high throughput.

Initial stages of vacuum condensation of As-S amorphous films on carbon substrates at the stages of nucleation and formation of condensed phase islands are studied using the electron microscopy technique. Two stages of the processes of critical nuclei formation were found: intense primary nucleation and slow secondary nucleation that occurs in parallel with the growth of the formed nuclei. The sizes of the critical nuclei of the amorphous As-S films, the primary nuclei density, the size distribution of the condensed phase islands at the moment of the nucleation processes termination and the mean diffusion length for different atomic particles of the As-S vapor phase on the substrate surface were determined. The results obtained show that at room condensation temperatures most of various multi atomic particles of the AsnSm vapor have rather high diffusion mobility over the carbon substrate surface. Therefore, when simulating the condensation processes, the As-S materials could be considered as a non-equilibrium two-dimensional gas with an extremely complicated chemical composition.

International audience; Cu, Mo-doped and pristine BiVO4 thin films were realized by coupling rf sputtering and mechanochemical synthesis technique. These monoclinic thin films were deposited over silicon substrate under the pure argon atmosphere (Ar 72 sccm). The sputtering targets were prepared by the respective ball-milled powders hydraulically pressed at optimal conditions. XRD analysis shows that the as-deposited thin films are amorphous and the monoclinic structure is obtained with a post-annealing process in the air at 450 °C for 2 h. Compositional, morphological and optical studies were thoroughly investigated by using FE-SEM, AFM and UV–Vis absorption spectroscopies respectively and discussed as a function of photocatalytic degradation of methyl orange organic dyes in solution. The pseudo first-order degradation rate constant values were estimated as 0.028, 0.031 and 0.022 min−1 for Cu, Mo-doped and pristine BiVO4 thin films respectively. Degradation performances are correlated as a function of their structural, surface morphological and film thickness aspects as well as the role of doping agent. Mo-doped high crystalline BiVO4 thin films with thickness 130 nm and morphology of small nano-sized islands on the surface (RMS = 5.08 nm) contributed well to the amplification of photocatalytic performance and followed by Cu doped and pristine BiVO4 thin films. © 2018, Springer Science+Business Media, LLC, part of Springer Nature.

Thin bismuth films obtained by vacuum deposition were recrystallized under electron beam of scanning electron microscope at 5 kV and examined in a transmission electron microscope at 200 kV. In recrystallized films, various microstructures were detected: single-crystal, polycrystalline and amorphous regions, more or less faceted grains, single crystals and untransparent drop-shaped particles. In the crystallized film, a strong internal bending of the crystal lattice is detected, up to 110 deg/μm. © Published under licence by IOP Publishing Ltd. Partial support of project 3.6121.2017/8.9 (The Ministry of Education and Science of the Russian Federation) and Agreement No 02.A03.21.0006 (Act 211 Government of the Russian Federation) is acknowledged.

We demonstrated self-aligned amorphous-Indium-Gallium-Zinc-Oxide (a-IGZO) thin-film transistors (TFTs) where the source–drain (S/D) regions were made conductive via chemical reduction of the a-IGZO via metallic calcium (Ca). Due to the higher chemical reactivity of Ca, the process can be operated at lower temperatures. The Ca process has the additional benefit of the reaction byproduct calcium oxide being removable through a water rinse step, thus simplifying the device integration. The Ca-reduced a-IGZO showed a sheet resistance (RSHEET) value of 0.7 kΩ/sq., with molybdenum as the S/D metal. The corresponding a-IGZO TFTs exhibited good electrical properties, such as a field-effect mobility (μFE) of 12.0 cm2/(V s), a subthreshold slope (SS−1) of 0.4 V/decade, and an on/off current ratio (ION/OFF) above 108. Cop. 2015 The Korean Information Display Society.

Zr-59 at.% Cu glassy film was deposited by co-magnetron sputtering using pure metal targets. The film exhibits an XRD-amorphous structure and smooth surface morphology. Isothermal annealing at 370 °C, for 30 and 60 min, modify the local structural ordering and promote nucleation of Cu10Zr7 nanocrystalline-like domains as confirmed by TEM analysis. The mechanical properties of the film are far higher than those of pure metals, and are still improved after nanocrystallization. Keywords: Local nanocrystallization, Mechanical properties, Glassy films, Microstructure

To evaluate the effects of different concentrations of noble metal in a TiO2 matrix, different films of both Ag:TiO2 and Au:TiO2 systems were prepared. Mechanical and tribological characterization was carried out to evaluate the coatings response as a function of the noble metals composition and (micro)structure of the films. The overall set of results indicates that the amorphous films reveal better results than the crystalline ones. For the amorphous samples, the reduced Young’s modulus and the adhesion critical loads followed similar tendencies in both sets of films. Wear rates were similar for all samples except for the one with the highest silver content. To improve brittleness of TiO2 films, the results seem to indicate that a slight metal doping is preferred, and Au showed to be a better choice than Ag. In fact, the sample with the lowest Au content revealed a better mechanical behaviour than the pure TiO2 film., This research was sponsored by FEDER funds through the COMPETE program (Programa Operacional Factores de Competitividade) and by FCT (Fundação para a Ciência e a Tecnologia), under the projects PEST-C/FIS/UI607/2013 and PEst-C/EME/UI0285/2013. The authors also acknowledge the financial support by the project Nano4color – Design and develop a new generation of color PVD coatings for decorative applications (FP7 EC R4SME Project No. 315286).

Amorphous InGaZnO (a-IGZO) is a candidate material for thin-film transistors (TFTs) owing to its large electron mobility. The development of high functionality circuits requires accurate and efficient circuit simulation that, in turn, is based on compact physical a-IGZO TFTs models. Here we propose a compact physical-based and analytical model of the drain current of a-IGZO TFTs. The model accounts for both trapped and free charges by means of an effective density of states that accurately approximate the actual a-IGZO density of states in the energy range relevant for the TFT operation. The model is implemented in a circuit simulator and it is validated with the measurements of both coplanar and staggered a-IGZO TFTs fabricated on flexible substrates.

cited By 4; International audience; Zr-based thin film metallic glasses appear as promising coatings for biomedical applications, due to their microstructural and physicochemical properties. Materials used as medical instruments or devices require antibacterial activity to avoid nosocomial infections. In this paper, an optimized Zr-Cu-Ag thin film metallic glass deposited by PVD magnetron sputtering is evaluated for antibacterial applications. Ternary Zr39Cu39Ag22 TFMG was elaborated by PVD magnetron sputtering using a multi-target reactor. It has been demonstrated that this thin film is amorphous, uniformly thick and chemically homogenous. Mechanical, electrochemical properties and thermal stability were also characterized. These films display high hardness and Young's modulus, as well as an interesting passive behavior. Finally, this TFMG exhibits a strong antibacterial effect against Staphylococcus aureus. © 2016 Elsevier B.V.

International audience; Photoelectron Energy Loss Spectroscopy (PEELS) is a highly valuable non destructive tool in applied surface science because it gives access to both chemical composition and electronic properties of surfaces, including the near-surface dielectric function. An algorithm is proposed for real materials to make full use of experimental X-ray photoelectron spectra (XPS). To illustrate the capabilities and limitations of this algorithm, the near-surface dielectric function ε(ℏω) of a wide range of amorphous carbon (a-C) thin films is derived from energy losses measured in XPS, using a dielectric response theory which relates ε(ℏω) and the bulk plasmon (BP) loss distribution. Self-consistent separation of bulk vs surface plasmon excitations, deconvolution of multiple BP losses and evaluation of Bethe-Born sensitivity factors for bulk and surface loss distributions are crucial to obtain several material parameters: (1) energy loss function for BP excitation, (2) dielectric function of the near-surface material (3–5 nm depth sensitivity), (3) inelastic mean free path, λP (E0), for plasmon excitation, (4) surface excitation parameter, (5) effective number NEFF of valence electrons participating in the plasma oscillation. This photoelectron energy loss spectra analysis has been applied to a-C and a-C:H films grown by physical and chemical methods with a wide range of (sp3/sp2 + sp3) hybridization, optical gap and average plasmon energy values. Different methods are assessed to accurately remove the photoemission peak tail at low loss energy (0–10 eV) due to many-body interactions during the photo-ionization process. The σ + π plasmon excitation represents the main energy-loss channel in a-C; as the C atom density decreases, λP (970 eV) increases from 1.22 nm to 1.6 nm, assuming a cutoff plasmon wavenumber given by a free electron model. The π-π* and σ-σ* transitions observed in the retrieved dielectric function are discussed as a function of the average (sp3/sp2 + sp3) C hybridization and compared with literature results.

A number of thin silicon films are deposited on crystalline silicon, native oxidized crystalline silicon, and optical quality fused quartz substrates through the use of ultra-high-vacuum evaporation at growth temperatures ranging from 98 to 572 °C. An analysis of their grazing incidence X-ray diffraction and Raman spectra indicates that a phase transition, from amorphous-to-crystalline, occurs as the growth temperature is increased. Through a peak decomposition process, applied to the Raman spectroscopy results, the crystalline volume fractions associated with these samples are plotted as a function of the growth temperature for the different substrates considered. It is noted that the samples grown on the crystalline silicon substrates have the lowest crystallanity onset temperature, whereas those grown on the optical quality fused quartz substrates have the highest crystallanity onset temperature; the samples grown on the native oxidized crystalline silicon substrates have a crystallanity onset temperature between these two limits. These resultant dependencies on the growth temperature provide a quantitative means of characterizing the amorphous-to-crystalline phase transition within these thin silicon films. It is noted that the thin silicon film grown on an optical quality fused quartz substrate at 572 °C, possessing an 83% crystalline volume fraction, exhibits an optical absorption spectrum which is quite distinct from that associated with the other thin silicon films. We suggest that this is due to the onset of sufficient long-range order in the film for wave-vector conservation to apply, at least partially. Finally, we use a semi-classical optical absorption analysis to study how this phase transition, from amorphous-to-crystalline, impacts the spectral dependence of the optical absorption coefficient.

Thin film transistors (TFTs) employing an amorphous indium gallium zinc oxide (a-IGZO) channel layer exhibit a positive shift in the threshold voltage under the application of positive gate bias stress (PBS). The time and temperature dependence of the threshold voltage shift was measured and analysed using the thermalization energy concept. The peak energy barrier to defect conversion is extracted to be 0.75 eV and the attempt-to-escape frequency is extracted to be 107 s-1. These values are in remarkable agreement with measurements in a-IGZO TFTs under negative gate bias illumination stress (NBIS) reported recently (Flewitt and Powell, J. Appl. Phys. 115, 134501 (2014)). This suggests that the same physical process is responsible for both PBS and NBIS, and supports the oxygen vacancy defect migration model that the authors have previously proposed. cop. 2016 AIP Publishing LLC.

In this work, we present the synthesis of a nanostructured TiOx film on a Ti foil by using a scalable and environmental friendly methodology such as the laser irradiation in liquid. The obtained black-TiOx film is composed by amorphous titanates and shows a high absorption in both visible and UV range. The introduction of a thin layer of Pt nanoparticles (PtNps) on the rear side of the Ti foil, gave rise to a stacked layered structure (TiOx/Ti/PtNps) that boosted the quantum photocatalytical efficiency, according to ISO 10678:2010. Such enhancement is discussed in terms of hole trapping by surface states and electron scavenging by the Pt Nps. (C) 2016 Elsevier B.V. All rights reserved.

International audience; Amorphous chalcogenide thin films were fabricated by the pulsed laser deposition technique. Thereafter, the stacks of multilayered thin films for reflectors and microcavity were designed for telecommunication wavelength. The prepared multilayered thin films for reflectors show good compatibility. The microcavity structure consists of Ge25Ga5Sb10S65 (doped with Er3+) spacer layer surrounded by two 5-layer As40Se60/Ge25Sb5S70 reflectors. Scanning/transmission electron microscopy results show good periodicity, great adherence and smooth interfaces between the alternating dielectric layers, which confirms a suitable compatibility between different materials. The results demonstrate that the chalcogenides can be used for preparing vertical Bragg reflectors and microcavity with high quality. © 2016, Tianjin University of Technology and Springer-Verlag Berlin Heidelberg.

A computer-controlled procedure is outlined here that first determines the position of the amorphous-crystalline interface in an image. Subsequently, from a time series of these images, the velocity of the crystal growth front is quantified. The procedure presented here can be useful for a wide range of applications, and we apply the new approach to determine growth rates in a so-called fast-growth-type phase-change material. The growth rate (without nucleation) of this material is of interest for comparison with identical material used in phase-change random access memory cells. Crystal growth rates in the amorphous phase-change layers have been measured at various temperatures using in situ heating in a transmission electron microscope. Doped SbTe films (20 nm thick) were deposited on silicon nitride membranes, and samples with and without silicon oxide capping layer were studied. The activation energy for growth was found to be 3.0 eV. The samples without capping layer exhibit a nucleation rate that is an order of magnitude higher than the samples with a silicon oxide capping layer. This difference can be attributed to the partial oxidation of the phase-change layer in air. However, the growth rates of the samples with and without capping are quite comparable.

Structural and electrochemical aspects of vanadium oxide films recently reported from ICMCB/ENSCPB have been examined using appropriate structural models. It is shown that amorphous films are nonstoichiometric as a result of pre-deposition decomposition of $V_2O_5$. It is proposed that the structure of amorphous films corresponds to a nanotextured mosaic of $V_2O_5$ and $V_2O_4$ regions. Lithium intercalation into these regions is considered to occur sequentially and determined by differences in group electronegativities. Open circuit voltages (OCV) have been calculated for various stoichiometric levels of lithiation using available thermodynamic data with approximate corrections. Sequestration of lithium observed in experiments is shown to be an interfacial phenomenon. X-ray photoelectron spectroscopic observation of the formation of $V^{3+}$ even when $V^{5+}$ has not been completely reduced to $V^{4+}$ is shown to be entirely consistent with the proposed structural model and a consequence of initial oxygen nonstoichiometry. Based on the structural data available on $V_2O_5$ and its lithiated products, it is argued that the geometry of $VO_n$ polyhedron changes from square pyramid to trigonal bipyramid to octahedron with increase of lithiation. A molecular orbital based energy band diagram is presented which suggests that lithiated vanadium oxides, $Li_xV_2O_5$, become metallic for high values of x.

This paper analyzes the three-dimensional (3D) surface texture of amorphous hydrogenated carbon films with sputtered iron nanoparticles (FeNPs@a-C:H) deposited by a radio-frequency plasma-enhanced chemical vapor deposition method on the quartz substrates. The prepared FeNPs@a-C:H films were used as research materials. The synthesized samples were deposited at four different pressures of 2.5, 3, 3.35, and 3.5 N/m2 in an acetylene gas atmosphere. The Fe and C contents of the thin films were obtained from X-ray photoelectron spectroscopy. The X-ray diffraction profile and electron diffraction pattern indicate that iron nanoparticles with body-centered-cubic crystalline structure are formed in these films. The localized surface plasmon resonance peak that is the signature of the existence of the iron core nanoparticles appears in visible spectra of these films. The sample surface images were recorded using an atomic force microscope operating in a noncontact mode and analyzed to reveal the statistical, fractal, and functional surface properties of prepared samples. Analysis of the 3D surface texture is essential for the correct interpretation of surface topographic features as well as its functional role for the test surface. It also helps to understand the relationship between the surface topography and functional properties.

cited By 5; International audience; Thin film metallic glasses are a new class of promising materials for advanced structural applications. In this work, binary Zr-based thin film metallic glasses (TFMGs) were deposited by the magnetron co-sputtering process from pure metal targets. Two similar enrichments were investigated (44 at.% for the nickel, 43 at.% for the cobalt), in order to determine the effect of the alloying element's nature on the structural, mechanical and electrochemical behaviors. Structure of films was determined by in situ XRD measurements carried out during heating up to 600 °C, while their morphology was characterized by SEM observations. Mechanical properties of amorphous and crystallized films (hardness and Young's modulus) were measured by nanoindentation. Intrinsic electrochemical properties are deduced from polarization curves and electrochemical impedance spectroscopy measurements carried out in Na2SO4 aqueous solution. It is found that the surface morphology of TFMGs was very smooth with a compact and dense microstructure. When heated, glassy films exhibit a high structural stability (up to 440 °C) with crystallization occurring through a multistage process for the Co-containing film. Whatever the coating, Zr affords its beneficial passive-ability, while crystallization process accelerates the global corrosion kinetics. Corrosion mechanisms of the Zr-based TFMGs were discussed in the light of the alloying element (Ni or Co) and the structure of films (amorphous or crystallized). © 2015 Acta Materialia Inc.

The self-assembly of anisotropic particles into two or three dimensional ordered arrays has diverse applications in several areas of science and engineering. In this article, we report the formation of a multi-layer film of nano-sized ellipsoids with long-range orientation and positional order through an evaporation driven vertical deposition technique. Using nano-sized ellipsoids of tunable surface charge, we show that electrostatic interactions can be exploited to control the arrangement of ellipsoids in the film. The pH of the aqueous suspensions used for vertical deposition is adjusted such that the surface charge and hence the electro-static interactions can be controlled. We show that the interplay between various Derjaguin and Landau, Verwey and Overbeek (DLVO) interactions can be effectively controlled to fabricate films with a random arrangement of particles as well as to create particulate films with three-dimensional ordering of ellipsoids. When the particles are weakly charged, the nano-ellipsoids in the film are randomly oriented giving an amorphous particulate film. However, when the particles are highly charged, the nano-ellipsoids in the film are oriented with major axis parallel to each other and ordered in three dimensions. These particulate film are observed to have parallel cracks across the entire width of the film. The major axis of the particle is found to be parallel to the crack direction and therefore, the direction of crack formation can be exploited to indicate the nature of particle ordering. � The Royal Society of Chemistry 2015.

In this work we propose the use of one single device (p-doped/intrinsic/n-doped amorphous silicon thin film diode) acting as both temperature and photo sensor. The two modalities are accomplished by applying two different bias conditions to the diode. In order to prove the correct device operation, we have analyzed the crosstalk effects of the temperature variation on light measurement and those of the light intensity variation on the accuracy in the temperature measurement. We found that the temperature variation induces an error lower than 0.55 pW/K in the light intensity measurement at 550 nm if the diode is biased in short circuit condition, while, an error below 1 Κ/μνν results in the temperature measurement, if a forward bias current higher than 25 μΑ/cm2 is applied. The use of a single sensor for the simultaneous measurement of two different physical parameters increases the integration level in miniaturized system as, for example, in lab-on-chip devices, where optical detection is often required during a heat treatment of the analyte.

International audience; SOI circuit exhibits excellent performance and rehabilitee but with the component miniaturization trend and the clock frequency increase, the self-heating phenomena that arise from the SOI structure itself must not be underestimated. In order to minimize this problem, several candidates have been identified to replace the buried silicon oxide (SiO2) by high thermal conductive dielectric layers such as HfO2, Si3N4, diamond or Al2O3. In order to elaborate a SOI structure using this kind of innovative buried dielectric, first of all, their direct bonding with silicon has to be studied. In this work, we investigate the bonding thermal behaviour of Si/Al2O3 and Al2O3/Al2O3 direct bonded structures: bondings are submitted to room temperature up to 900 A degrees C annealing. Amorphous or crystallized Al2O3 thin films were used in this study. Bonding energies are measured in an anhydrous atmosphere and bonding defectivity is analysed using scanning acoustic microscope (SAM). With amorphous a-Al2O3 layer, for T > 200 A degrees C, high bonding energy are obtained even if high defect density appeared when annealing temperature exceeded 400-500 A degrees C. Spontaneous debonding phenomena even occurred for a-Al2O3/a-Al2O3 direct bonding. This defectivity, unobservable using infrared camera, may be explained by chemical or structural Al2O3 modification such as gases desorption, internal stress or crystallisation state. Bonding with crystallized Al2O3 film has been also characterized by infrared spectroscopy and complementary analysis. No high defect density is observed with crystallized Al2O3 layer. Based on these results, an Al2O3 bonding mechanism is proposed.

Tantalum oxynitride thin films were produced by magnetron sputtering. The films were deposited usinga pure Ta target and a working atmosphere with a constant N2/O2ratio. The choice of this constant ratiolimits the study concerning the influence of each reactive gas, but allows a deeper understanding of theaspects related to the affinity of Ta to the non-metallic elements and it is economically advantageous.This work begins by analysing the data obtained directly from the film deposition stage, followed bythe analysis of the morphology, composition and structure. For a better understanding regarding theinfluence of the deposition parameters, the analyses are presented by using the following criterion: thefilms were divided into two sets, one of them produced with grounded substrate holder and the otherwith a polarization of −50 V. Each one of these sets was produced with different partial pressure of thereactive gases P(N2+ O2). All the films exhibited a O/N ratio higher than the N/O ratio in the depositionchamber atmosphere. In the case of the films produced with grounded substrate holder, a strong increaseof the O content is observed, associated to the strong decrease of the N content, when P(N2+ O2) is higherthan 0.13 Pa. The higher Ta affinity for O strongly influences the structural evolution of the films. Grazingincidence X-ray diffraction showed that the lower partial pressure films were crystalline, while X-rayreflectivity studies found out that the density of the films depended on the deposition conditions: thehigher the gas pressure, the lower the density. Firstly, a dominant -Ta structure is observed, for lowP(N2+ O2); secondly a fcc-Ta(N,O) structure, for intermediate P(N2+ O2); thirdly, the films are amorphousfor the highest partial pressures. The comparison of the characteristics of both sets of produced TaNxOyfilms are explained, with detail, in the text., This work was supported by FEDER through the COMPETE Program and by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Project PEST-C/FIS/UI607/2013. This paper was also supported by the Sectoral Operational Programme Human Resources Development (SOPHRD), ID134378 financed from the European Social Fund and by the Romanian Government.

The purpose of this paper is to analyze surface properties of AlGaN thin film produced using thermionic vacuum arc technique. Thermionic vacuum arc is an alternative deposition technique for GaN thin films that produces in a very short production time for GaN-based solid-state applications. XRD results showed that AlGaN thin film with cubic crystal structure on a amorphous glass was grown. Conductivity type of AlGaN thin film is determined as p-type by hot-probe method which is a very simple method. The surface morphology was analyzed and discussed using field emission scanning electron microscopy (FESEM) and atomic force microscopy. The contact angles in four different testing liquid and surface free energy of the AlGaN thin film were investigated by optical tensiometer. © 2015 Elsevier B.V.

Ferroelectric polymers and amorphous metal oxide semiconductors have emerged as important materials for re-programmable non-volatile memories and high-performance, flexible thin-film transistors, respectively. However, realizing sophisticated transistor memory arrays has proven to be a challenge, and demonstrating reliable writing to and reading from such a large scale memory has thus far not been demonstrated. Here, we report an integration of ferroelectric, P(VDF-TrFE), transistor memory arrays with thin-film circuitry that can address each individual memory element in that array. n-type indium gallium zinc oxide is used as the active channel material in both the memory and logic thin-film transistors. The maximum process temperature is 200 °C, allowing plastic films to be used as substrate material. The technology was scaled up to 150 mm wafer size, and offers good reproducibility, high device yield and low device variation. This forms the basis for successful demonstration of memory arrays, read and write circuitry, and the integration of these. cop. 2015 IOP Publishing Ltd.

The electrical and Hall resistivities of Tbx Fe100-x thin films in the temperature range 13-300 K were investigated. The sign of Hall resistivity at 300 K is found to change from positive for x=28 film to negative for x=30 film, in accordance with the compensation of Tb and Fe moments. All the films are seen to have planar magnetic anisotropy at 13 K. The temperature coefficients of electrical resistivities of the amorphous films with 19?x?51 are seen to be negative. The temperature dependence of Hall resistivity of these films is explained on the basis of random magnetic anisotropy model. The temperature dependences of Hall resistivities of the x=22 and 41 films are seen to exhibit a nonmonotonous behavior due to change in anisotropy from perpendicular to planar. The same behavior is considered for the explanation regarding the probable formation of Berry phase curvature in these films. � 2009 American Institute of Physics.

Tantalum oxynitride (TaNxOy) thin films were produced by magnetron sputtering. This work analyzes and compares the mechanical properties and the wear behavior of the films, taking into account the differences promoted by changes in composition and structure, caused by the variation of the partial pressure of the reactive gases (P(N2+O2)) and by the polarization of the substrate holder. Besides the change in composition, the variation of P(N2+O2) causes significant changes in the morphology and structure of the films. Those produced with low P(N2+O2) evidence a higher crystallinity and, in these conditions, the films exhibit hardness around 20 GPa. Films producedwith higher P(N2+O2) exhibit higherO content, are amorphous and the hardness is significantly lower. The substrate bias does not influence the adhesion of the films to the high speed steel substrate, but influences the mechanical properties, particularly the hardness, at low P(N2+O2) regime. Films with higher crystallinity exhibit higher hardness, but in the low P(N2 + O2) regime, those who were produced with polarization are harder. Although some dependence may be established for set B films, the hardness is not as influent on the wear resistance of the TaNxOy films as the friction coefficient., This work was supported by FEDER through the COMPETE Program and by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Project PEST-C/FIS/UI607/2013 and by the Sectoral Operational Programme Human Resources Development (SOP HRD), financed by the European Social Fund and by the Romanian Government under the project number POSDRU/159/1.5/S/ 134378.

cited By 2; International audience; Asymmetric polystyrene-b-polymethylmethacrylate (PS-b-PMMA) block copolymers are used to fabricate nanoporous PS templates with different pore diameter depending on the specific substrate neutralization protocol. The resulting polymeric templates are used as masks for the subsequent deposition of a thin (h = 5 nm) amorphous Si layer by electron beam evaporation. After removal of the polymeric film and of the silicon excess, well-defined hexagonally packed amorphous Si nanodots are formed on the substrate. Their average diameter (d

Date of Conference: 3–6 February 2013 Conference name: Proceedings of SPIE, Oxide-based Materials and Devices IV In this study, TiO2 films were deposited using thermal Atomic Layer Deposition (ALD) system. It is observed that asdeposited ALD TiO 2 films are amorphous and not suitable as TFT channel material. In order to use the film as channel material, a post-annealing process is needed. Annealed films transform into a polycrystalline form containing mixed anatase and rutile phases. For this purpose, devices are annealed at 475°C and observed that their threshold voltage value is 6.5V, subthreshold slope is 0.35 V/dec, Ion/Ioff ratios 2.5×106 and mobility value is 0.672 cm2/V.s. Optical response measurements showed that devices exhibits decent performance at ultraviolet region where TiO 2 has band to band absorption mechanism. © 2013 SPIE.

This study investigates the effects of the deposition process and coating composition on microstructural and tribological properties of TiN and CrN based coating systems. Coatings were produced using various PVD based processes - electron beam (EB), cathodic arc (CA) and plasma enhanced magnetron sputtering (PEMS). All coated samples were evaluated for their composition, microstructure and surface morphology. Coating mechanical properties such as hardness, Young's modulus and coefficient of friction were also studied and related to their microstructures, wear and erosion resistances. It was found that hardness (H), Young's modulus (E) and coefficient of friction had impact on both wear and erosion rates. In particular, the H3/E2 ratio was inversely proportional to the specific wear rate. For erosion behaviour, higher H3/E2 ratios relate to lower erosion rates at low impingement angles; whereas higher H3/E2 ratios relate to higher erosion rates at high impingement angles., ASME Turbo Expo 2012: Turbine Technical Conference and Exposition, GT 2012, June 11-15, 2012, Copenhagen, Denmark