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Purpose. As40 − x Sb x S60 amorphous films are suitable for creation of highly efficient, diffraction gratings, optical diffraction elements, optical compact-disks and sensors, waveguides, elements for infrared and nonlinear optics. This paper is devoted to investigation of Raman spectra of glasses and films and transmission spectra of films in As-Sb-S system with the Sb content up to 12 at % and their changes under laser radiation. Methods. Raman and optical spectroscopy, atomic forse microscopy. The transmission spectra were studied in 400-750 nm range at room temperature using a diffraction monochromator “MDR-23”. The spectral resolution was no worse than 10-3 eV. Results and discussion: Increased concentration of antimony in the composition of As40 − x Sb x S60 (0 ≤ x ≤ 12) amorphous films and laser irradiation ( λ =530 nm) of them result in the shift of their absorption edge to the longwave range. In this case the pseudogap width E g decreases, whereas the index n increases. Under the same conditions of irradiation, the largest changes in optical parameters occur in the As36Sb4S60 film. Changes in the optical characteristics of films are caused by photostructural transformations taking place in them under the laser irradiation. The nanoheterogenous structure of the studied films was established. The structural matrix of As40 − x Sb x S60 films is built from As(Sb)S3 pyramidal units connected by bridging S atoms. No molecular fragments with Sb-Sb bonds in the structure of films were detected. However, the large amount of structural groups with homopolar As-As (As4S4, As4S3) and S-S bonds (Sn) are present in the structure of films. The laser irradiation of As40 − x Sb x S60 films leads to the breaking and switching of As-As and S-S bonds in As4S4, As4S3, and Sn type structural fragments. Accompanied with the formation of structural units with heteropolar bonds As-S (AsS3). These structural transformations are related with the decreasing content of molecular fragments possessing homopolar bonds in films matrix. Conclusions. Transmission and Raman spectra of as-prepared and irradiated As40 − x Sb x S60 amorphous films were investigated. The nanoheterogenous structure of the studied films was confirmed by Raman spectra. It was established that the growth of the Sb content in composition of films and irradiation induced the absorption edge shift to the longwave region, E g decreased and n increased. The largest changed in optical parameters of as-prepared and irradiated films occur in the As36Sb4S60 film. These changes are caused by the photostructural transformations, which are accompanied by decreasing in the number of structural groups with homopolar bonds in films matrix.

Li–Nb–O amorphous films were deposited onto Si substrates by the radio-frequency magnetron sputtering method in an Ar environment. As-grown films are crystallized under thermal annealing (TA) at the temperature of up to 600 °C with a formation of LiNbO3. Capacitance–voltage and current–voltage analysis revealed a positive fixed oxide charge existed in the films. TA influences the structure and electrical properties of as-grown films. The fraction of a crystalline phase in the film increases from 45 to 100% when raising the annealing temperature from 450 to 475 °C. The effective positive charge in the amorphous films changes non-monotonically with TA reaching a minimum value at the temperature of 450 °C when the effective dielectric constant has a maximum value. The concentration of traps in the films depends on the annealing temperature and reaches a minimum value at T = 600 °C which is caused by the formation of the large-block crystalline structure. Charge transport mechanisms are also discussed.

The fragmentation and interfacial stress transfer of Cu75Zr25 amorphous films with varying film thickness (h) on polyimide substrates were systematically investigated by using uniaxial tensile testing, in combination with in situ optical microscope and atomic force microscope characterizations. It is revealed that the interfacial stress transfer length increases monotonically as h increases. The interfacial stress transfer mechanism changes from elastic-plastic to approximately linear elastic at a critical point of h = 250 nm. This is related to h-dependent deformation-induced devitrification (DID) near the interfaces that the thinner Cu-Zr amorphous films display more DID. This study elucidates for the first time the effect of DID on the interfacial stress transfer, which will be helpful to design the interface with desired property for nanotechnological applications.

The phenomenon of spontaneous spin reorientation in Gd–Сo amorphous films, which results from the competition between the perpendicular magnetic anisotropy and shape anisotropy, is studied. It is shown that the reorientation occurs via the formation of a fine-grained nonuniform magnetic structure called hypercritical state in a wide temperature range. Magnetic domains in the spin-reorientation region are characterized using magnetic and magneto-optical measurements. Based on the experimental magnetometric data and results of simulating the temperature dependences of spontaneous magnetization, the phase diagram of the films containing 16–26 at % Gd is constructed, which, being plotted on coordinates elemental composition—temperature, exhibits the ranges of existence of the perpendicular anisotropy, transition magnetic anisotropy (hypercritical state), and planar magnetization state.

Bulk glassy Se98Te2 and Se96Te2X2 (X = Zn and Cd) were prepared by melting quenching method. Thin films of various thicknesses (200 – 670 nm) were obtained by the thermal evaporation method. The structure of the prepared compositions was investigated by X-ray and EDX analysis. We studied the effect of Zn and Cd addition on the electric and dielectric properties of Se98Te2 thin films. Our measurements were studied in the temperature range (298-323K) below the glass transition temperature and frequency range (100 Hz-1 MHz). DC conductivity showed a single conduction mechanism by hopping of charge carriers at the band edges for the studied system. The dependence of Ac conductivity on frequency is linear with frequency exponent s lies very close to unit and is independent of temperature. This can be explained by the correlated barrier hopping (CBH) model. The dielectric constant ε1 and dielectric loss ε2 noticed to decrease with frequency and increase with temperature. The maximum barrier height Wm was calculated according to Guinitin.

Side-chain substitutions have important influence on the aggregation of perylene diimide (PDI), which show a great impact on their excited-state dynamics as well. Herein, by employing photoluminescence (PL), time-resolved photoluminescence (TRPL) and transient absorption (TA) spectroscopy, we investigated excited-state dynamics of two perylene diimide (PDI) derivative amorphous films, i.e. undecane-substituted PDI (PDI-1) and diisopropylphenyl-substituted PDI (PDI-2), fabricated with spin coating method. Femtosecond transient absorption spectra reveal that both films show pronounced ground state bleach (GSB) with lifetime longer than 10 ns while the relaxation of excited state absorption (ESA) has typical lifetime less than 1 ns. The significant feature of excited state decay in PDI-2 is dominated by transforming the singlet excited state into two triplet states via singlet fission, which is evidenced by the appearance of triplet state absorption. By contrast, the absence of triplet state absorption and the appearance of long-lived emission species in PDI-1 suggest that the decay of excited-like state could be dominated by the formation of excimer. Our present study reveals for the first time that the singlet fission does occur in amorphous PDI film, the study also demonstrates that side-chain substitutions have great impact on the excited-state dynamics of PDI.

Stray fields of magnetic systems with a known degree of structural and magnetic nonuniformities have been mapped using indicator amorphous films with a perpendicular anisotropy. The characteristic magnetooptical patterns have been determined, which correspond to the distribution of the magnetic-field component normal to the plane of the indicator films. The theoretical patterns of model magnetic systems that are similar to the studied systems in the degree of the structural and magnetic nonuniformity have been calculated. The validity of the magnetooptical visualization has been confirmed by comparison of the experimental and theoretical patterns. The possibility of the express monitoring of the parameters of the magnetic system has been shown using a laboratory model of a magnetooptical visualizer by the observation of the magnetooptical contrast of gadolinium–cobalt indicator films under the action of an ac magnetic field.

Through electroless plating, the Al0.3CoCrFeNi high-entropy alloys were successfully coated with the Ni-P amorphous film with a thickness of 1.2 μm. For studying the surface change of samples after chemical plating, the surface morphologies of the as-cast HEA substrate and HEA with the Ni-P film were contrasted by atomic-force microscopy. The tensile properties of the samples with and without the Ni-P film, and the deformational behavior of thin Ni-P film were researched, respectively. In addition, the effect of the Ni-P amorphous film on corrosion resistance of the coated HEAs was also investigated. The experimental results show that in contrast to the uncoated samples with a yielding strength of 275 MPa, the yielding strength of the coated samples exhibits 400 MPa, with a 45% improvement, which can be attributed to the very high yield strength of the Ni-P amorphous film. A tensile strain up to 10% was achieved in the Ni-P film since the propagation of one primary shear band was inhibited, and the stress/strain concentration was retarded by the plastic substrate. The corrosion resistance of the HEA with the Ni-P film is superior to that of the bare HEA in the 3.5 wt percent NaCl solutions due to the chemical homogeneity and the absence of microscopic defects in the Ni-P amorphous film. The current results indicate that the surface coating is an effective means for optimizing the properties of HEAs, and the thin Ni-P coating can remarkably improve the strength of the present HEAs.

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.

The architecture consisting of a thin film resting on a substrate is a common feature in a wide variety of applications. Understanding of the failure mechanisms is essential for design of reliable film/substrate systems. Recent experiments showed that shear banding induced fracture and brittle cracking of films are two major fracture modes in the structure composed of an amorphous metallic glass film bonded to a metal substrate. In this study, we carry out numerical analyses of fracture in amorphous films resting on ductile substrates, with the aim to unveil the mechanisms governing the competition between the two fracture modes observed in the experiments. In the calculations, the brittle cracking of amorphous films is modeled using the cohesive zone framework and the shear banding induced fracture in films is characterized by a simple local fracture criterion. The results show that brittle cracking of amorphous films occurs in the case of thin films, while the shear banding induced fracture dominates in the case of thick films. For the films with intermediate thickness, the mixed fracture modes are observed. Such a film thickness effect predicted by numerical simulations is consistent with the experimental observations. We further reveal that the film thickness effect is related to substrate constraint. In addition, it is identified that the cohesive strength and toughness of amorphous films also play an important role in controlling the fracture modes of the film/substrate systems.

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.

WOS: 000452762000010, Amorphous films of two varieties of zinc stannate (ZnSnO3 and Zn2SnO4) have been considered that were fabricated by radio-frequency sputtering of ceramic compound targets containing ZnO and SnO2 in 1: 1 and 2: 1 ratios. The elemental and phase compositions of the films and their optical and electrical parameters were determined. The transparency of the films in the visible spectral range is on average 87%. Zinc stannate amorphous films have a high electrical conductivity in contrast to amorphous ZnO and SnO2. This phenomenon, which makes it possible to use zinc stannate amorphous films in transparent and flexible electronics, is explained., Russian Foundation for Basic Research and TUBITAK [12-02-91373_CT_a], This study was supported in part by the Russian Foundation for Basic Research and TUBITAK, grant no. 12-02-91373_CT_a.

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.

In metallic glasses (MGs), plastic deformation at room temperature is dominated by highly localized shear bands. Here we report the non-localized deformation under tension in Cu Zr multi-layer MGs with a pure amorphous structure using large-scale atomistic simulations. It is demonstrated that amorphous samples with high layer numbers, composed of Cu64Zr36 and Cu40Zr60, or Cu64Zr36 and Cu50Zr50, present obviously non-localized deformation behavior. We reveal that the deformation behavior of the multi-layer-structured MG films is related but not determined by the deformation behavior of the composed individual layers. The criterion for the deformation mode change for MGs with a pure amorphous structure, in generally, was suggested, i.e., the competition between the elastic-energy density stored and the energy density needed for forming one mature shear band in MGs. Our results provide a promising strategy for designing tensile ductile MGs with a pure amorphous structure at room temperature.

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.

We investigate the role of oxygen vacancies in photochromism of molybdenum oxide amorphous films. MoO3−x films with a wide range of initial stoichiometries are deposited using R.F. unbalanced magnetron sputtering. The evolution of visible light absorption in conjunction with Raman spectra for these films is studied in detail during the course of UV-irradiation to correlate the color change to the Mo6+ to Mo5+ conversion. For films which have an initially more complete stoichiometry, and hence lower oxygen vacancy concentration, the color change fully correlates with conversion of Mo6+ to Mo5+. This behavior is consistent with the group of models of photochromism of transition metal oxides which disregard the presence of oxygen vacancies in the films. However, coloration of the films with initially greater deviation from complete stoichiometry, and hence higher oxygen vacancy concentration, is not accompanied by any significant conversion of Mo6+ to Mo5+. This behavior is consistent with the group of models of photochromism of transition metal oxides which rely on the presence of oxygen vacancies. Overall, the reported results demonstrate the importance of the initial stoichiometry in the photochromism of MoO3−x amorphous films, particularly in the initial stages of UV-irradiation.

We have detected that surface relief gratings (SRG) in amorphous chalcogenide films As20Se80 can be optically recorded at low temperature, such as 77 K. A diffusion mechanism of photo-induced (PI) mass transport is proposed. A driving force of PI mass transport is a lateral steady state electric field induced by light interference. The kinetics of PI SRG growth depends on temperature due to temperature dependence of PI diffusion coefficients and concentration of radiation defects. By comparison of low temperature kinetics with that at 300 K we estimated diffusion activation energy, which turned out 0.09 eV. We present a model that explains low diffusion activation energy.

The giant magnetic-impedance (GMI) effect in FeCoSiB thin films was investigated. By introducing the role of demagnetizing field, based on linear Maxwell’s equations and Landau-Lifshitz-Gilbert (LLG) equation, the expressions of permeability and impedance were obtained and the theoretical model in this paper was significantly improved. A numerical simulation was conducted using MATLAB. For the thickness of thin film being close to the skin depth when the frequency of alternating current was up to megahertz, it could be found that the calculation results could match the experimental data very well when the thickness of the FeCoSiB thin film was greater than skin depth, while when the thin film thickness was less than skin depth, the calculation results had a big distortion. The influence of the demagnetization factor of FeCoSiB thin films on the GMI effect was also researched. This work was a tentative research on the simulation of the GMI effect of thin films. It might provide an attempt on the theoretical calculation of the GMI effect of thin films and guidance for the fabrication of thin-film GMI sensors.

Laser pulse processing of surfaces and thin films is a useful tool for amorphous thin films crystallization, surface nanostructuring, phase transformation and modification of physical properties of thin films. Here we show the effects of nanostructuring produced at the surface and under the surface of amorphous GeTiO films through laser pulses using fluences of 10–30 mJ/cm2. The GeTiO films were obtained by RF magnetron sputtering with 50:50 initial atomic ratio of Ge:TiO2. Laser irradiation was performed by using the fourth harmonic (266 nm) of a Nd:YAG laser. The laser-induced nanostructuring results in two effects, the first one is the appearance of a wave-like topography at the film surface, with a periodicity of 200 nm and the second one is the structure modification of a layer under the film surface, at a depth that is related to the absorption length of the laser radiation. The periodicity of the wave-like relief is smaller than the laser wavelength. In the modified layer, the Ge atoms are segregated in spherical amorphous nanoparticles as a result of the fast diffusion of Ge atoms in the amorphous GeTiO matrix. The temperature estimation of the film surface during the laser pulses shows a maximum of about 500 °C, which is much lower than the melting temperature of the GeTiO matrix. GeO gas is formed at laser fluences higher than 20 mJ/cm2 and produces nanovoids in the laser-modified layer at the film surface. A glass transition at low temperatures could happen in the amorphous GeTiO film, which explains the formation of the wave-like topography. The very high Ge diffusivity during the laser pulse action, which is characteristic for liquids, cannot be reached in a viscous matrix. Our experiments show that the diffusivity of atomic and molecular species such as Ge and GeO is very much enhanced in the presence of the laser pulse field. Consequently, the fast diffusion drives the formation of amorphous Ge nanoparticles through the segregation of Ge atoms in the GeTiO matrix. The nanostructuring effects induced by the laser irradiation can be used in functionalizing the surface of the films.

The aim of this study was to investigate the effect of Zr as alloying element to carbon films, particularly in respect to film structure and mechanical properties. The films were deposited by magnetron sputtering in reactive (Ar + CH4) and non-reactive (Ar) atmosphere with different Zr contents (from 0 to 14 at.%) in order to achieve a nanocomposite based films. With an increase of Zr content a broad peak was observed in X-ray diffraction spectra suggesting the presence of nanocrystalline (nc) ZrC phase for the coatings with Zr content higher than 4 at.%. The application of Scherrer formula yielded a grain sizes with a dimension of 1.0–2.2 nm. These results were supported by X-ray photoelectron spectroscopy showing typical charge transfer at Zrsingle bondC nanograins and carbon matrix interface. The nc-ZrC phase was also observed by transmission electron microscopy. The hardness of the coatings was approximately independent of Zr content. However, the Young modulus increased linearly. The residual stress of the coatings was strongly improved by the presence of nc-ZrC phase embedded in the a-C matrix. Finally, the incorporation of H into the matrix led to denser and harder films.

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

By using wavelength-tunable, low fluence picosecond pulses at a 1 kHz repetition rate in a transient grating pump and probe configuration, we show that photoexcitation to higher vibrational levels leads to slower singlet exciton fission rates in rubrene. After the 1 ps photoexcitation, the initial growth of the triplet exciton population is exponential, with its time-constant systematically varying from 2.5 ± 0.7 ps to 40 ± 15 ps as the excitation photon energy is increased from the lowest to the third main vibrational band in the vibrational progression of rubrene’s absorption spectrum. We also determine that short-pulse-induced fluorescence in amorphous rubrene films deposited by molecular beam epitaxy in high vacuum decays as a single exponential with a lifetime of 15.2 ns, close to rubrene’s radiative lifetime for molecules in solution. This shows that singlet fission is non-existent in fully amorphous rubrene films, despite the close molecular packing, which indicates that in these films there is no short range molecular order matching the molecular arrangement in orthorhombic rubrene crystals.

Configurations of magnetic domain structure of gadolinium-cobalt amorphous films with a perpendicular anisotropy under the effect of spatially nonuniform magnetic stray fields produced by various miniature sources have been studied. The domain structure of the amorphous films has been shown to qualitatively and quantitatively reflect the symmetry and magnitude of the normal component of the nonuniform magnetic fields and, similar to iron garnets, can be used for topographying stray fields. New features of the domain structure have been found during the visualization of small-scale sources of stray fields, on the one hand, and fields characterized by a small gradient, on the other hand.

Although inorganic crystalline phosphors can exhibit high quantum efficiency, their use in phosphor films has been limited by a reliance on organic binders that have poor durability when exposed to high-power and/or high excitation energy light sources. To address this problem, Sn2+ -doped transparent phosphate films measuring several micrometers in thickness have been successfully prepared through heat treatment and a subsequent single dip-coating process. The resulting monolithic inorganic amorphous film exhibited an internal quantum efficiency of over 60% and can potentially utilize transmitted light. Analysis of the film’s emissivity revealed that its color can be tuned by changing the amount of Mn and Sn added to influence the energy transfer from Sn2+ to Mn2+. It is therefore concluded that amorphous films containing such emission centers can provide a novel and viable alternative to conventional amorphous films containing crystalline phosphors in light-emitting devices.

The optical transmissions spectra of amorphous Ge-S-Se films of chemical compositions (GeS2)50(GeSe2)50 and (GeS3)50(GeSe3)50, prepared by thermal evaporation, have been measured over the whole 400 to 800 nm spectral range. It has been ascertained that annealing of the films leads to the absorption edge shift into the short-wave spectral region. The values of pseudo-gap width Eg and film refraction index n have been determined. Changes in optical properties of films are caused by structural transformations taking place in them under laser illumination and annealing.

We report the compositional and temperature dependence of magnetic compensation in amorphous ferrimagnetic Gd x Fe 93− x Co 7 alloy films. Magnetic compensation is attributed to the competition between antiferromagnetic coupling of rare-earth (RE) with transition-metal (TM) ions and ferromagnetic interaction between the TM ions. The low-Gd region of x between 20 and 34 was found to exhibit compensation phenomena characterized by a low saturation magnetization and perpendicular magnetic anisotropy (PMA) near the compensation temperature. Compensation temperature was not observed in previously unreported high-Gd region of x =52–59, in qualitative agreement with results from recent model calculations. However, low magnetization was achieved at room temperature, accompanied by a large PMA with coercivity reaching ~6.6 kOe. The observed perpendicular magnetic anisotropy of amorphous GdFeCo films probably has a structural origin consistent with certain aspects of the atomic-scale anisotropy. Our findings have broadened the composition range of transition metal-rare earth alloys for designing PMA films, making it attractive for tunable magnetic anisotropy in nanoscale devices.

Weakly absorbing films of tantalum oxide Ta2O5 with the crystallization kinetics typical of amorphous films have been investigated. The films have been prepared by reactive magnetron sputtering on substrates of different natures (titanium and optical silica glass). The crystallization heat treatment of the films has been performed at temperatures ranging from 500 to 700 °C. Changes in the optical properties of the films in the visible range have been studied at the initial stage of the formation of nanosized nuclei. Investigations have been carried out using X-ray powder diffraction, atomic-force microscopy, and optical measurements. It has been demonstrated that a new reflecting layer with the refractive index smaller than that of the film is formed on polycrystalline substrates due to the heterogeneous nucleation of the crystalline phase at the film-substrate interface. The crystallization of the films on amorphous substrates occurs through the homogeneous mechanism and leads to a change in the transmission coefficient of the film as a result of light scattering from the nanocrystalline phase.

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.

A new route to prepare polycrystalline CdTe films using electrodeposition of amorphous Cd-Te films and subsequent annealing was investigated. Amorphous Cd-Te films with Te-rich compositions could be electrodeposited from ammoniacal alkaline aqueous solutions. The deposition rate of the amorphous film was much higher than that of crystalline CdTe. Annealing of the Te-rich amorphous Cd-Te film at 400 °C in air yielded a crystallized CdTe film with a nearly stoichiometric composition. Thermodynamic calculations of the vapor pressures of Cd and Te species suggested that the decrease in the Te content of the annealed film was due to the vaporization of Te in the forms of oxides. Although an isothermal annealing generated a number of large holes in the film, an annealing with a slow temperature ramp resulted in a crystalline CdTe film without the large holes.

Ru underlayer effects on the thermal stability of the magnetic properties in Co-Sm amorphous films have been investigated in terms of its robustness for the thermal-process in the fabrication of GHz band micro-magnetic devices. The anisotropy magnetic field Hk of the Co-Sm film was tending to decrease with an increase in the annealing temperature, but the reduction in Hk due to thermal-process became small by introducing the Ru underlayer. The high-resolution transmission electron microscopy (HR-TEM) observations revealed the presence of nanosized crystalline Sm segregation at the interface between the Co-Sm film and SiO2/Si substrate in the films without Ru underlayer, while there is no Sm segregation in the film with Ru underlayer. Sm segregation and the subsequent thermally induced phase-separation are one of the factors for the reduction in Hk. Ru underlayer effectively prevents the segregation of crystalline Sm and the resulting reduction in Hk. High-frequency magnetic property of Co-Sm film with Ru underlayer was superior to that without Ru underlayer for same annealing condition.

Anisotropic formation of equilibrium-thickness Bi2O3-enriched surficial amorphous films (SAFs) on ZnO has been documented [Luo J, Chiang Y-M. Acta Mater 2000;48:4501]. This study further explores anisotropic wetting of ZnO single crystals by Bi2O3-rich liquid with and without SAFs. For Bi2O3 on the ZnO { 1 1 2 ¯ 0 } surfaces wherein nanometer-thick SAFs are present in equilibrium with partial wetting drops, the measured (advancing) contact angle decreases with increasing temperature, but it stabilizes at ∼6° above ∼860 °C. In contrast, the contact angle is virtually a constant on the { 1 1 ¯ 0 0 } surfaces where SAFs are not present. This observation suggests that wetting in the presence of nanoscale SAFs follows a generalized Cahn wetting model. Faceted ridge formation at the triple lines and associated pinning effects are observed. Observation and analysis of unique two-stage isothermal drop receding kinetics show that complete wetting does not occur up to 1050 °C and that the receding contact angle is estimated to be ∼4° via two methods. Quantitative evaluation of a thermodynamic model shows that the observed “residual” contact angle of ∼4–6° and the extended SAF stability can be explained on the basis of a significant attractive London dispersion force.

Experimental observations of the creep response of a commercial sintered silicon nitride ceramic are presented. The stable microstructure of this material at high temperature contains secondary crystalline phases which result from partial devitrification of the intergranular phase. The widths of amorphous films along grain boundaries (between silicon nitride grains) and phase boundaries (between silicon nitride and secondary phase grains) are characterized by transmission electron microscopy. The thickness distributions of grain-boundary films before and after creep are analyzed by a statistical method. While the film widths are highly uniform before creep, a bimodal distribution is observed after creep. The results suggest that viscous flow of the boundary amorphous films occurs during creep deformation.

Kinetic formation and distribution of amorphous films at grain boundaries during grain growth have been studied in a model ceramic system, BaTiO3, using single crystal/polycrystal bi-layers. Single crystal containing BaTiO3 powder compacts with different TiO2 additions (0.1, 0.4 and 1.0 mol%) were heat-treated at 1250 °C for 10 h in H2 and then annealed at 1350 °C, above the eutectic temperature, in air for up to 50 h. During the air-annealing the single crystals grew into fine matrix grains of ∼2.0 μm diameter while no grain growth occurred in the matrix. With the growth of the single crystal, an amorphous film formed at the boundaries between the crystal and the matrix grains, and its thickness increased. As the amount of TiO2 increased from 0.1 to 1.0 mol%, the film thickness increased about ten times. These experimental results show for the first time that: (i) grain growth in solid–liquid two phase materials can induce the formation and thickening of intergranular amorphous films at dry grain boundaries, and (ii) the film thickening is mainly due to the penetration of liquid pockets at triple junctions into the films formed during grain growth.

B–C and B–C:Si films were deposited by r.f. magnetron sputtering from a hot-pressed B4C polycrystalline target with Si pieces placed on the preferentially eroded zone. The effect of Si content, ranging from 2 to 6 at.-%, on the B–C films was studied at a fixed substrate bias of −70 V. Preliminary depositions with different substrate bias showed that with −70 V the deposition of free carbon was avoided. All deposited films were X-ray diffraction (XRD) amorphous, and the result was confirmed by Fourier transform infrared spectroscopy (FTIR). Si-containing films were harder than Si-free ones, reaching 30 GPa for compositions up to 4.5 at.-% Si. After thermal annealing of the B–C:Si films up to 700 °C, an increase of the hardness was observed. The maximum hardness of 37 GPa was obtained for 2 at.-% Si film annealed at 600 °C, which corresponds to an increase of ∼23% in relation to the as-deposited conditions. No vestiges of crystallinity were found either by XRD or FTIR analysis suggesting that the structure of the Si-containing films consisted of a local order arrangement of boron-rich icosahedral units.

Mechanical properties were detected by the nanoindentation method for the Cu–Ta amorphous films with Ta content from 25.6 to 96 at.%. The hardness and elastic modulus are found to vary linearly with the Ta concentration. The incremental change of the elastic modulus is 1.35 GPa per Ta atom and that of the hardness is 0.205 GPa per Ta atom. The samples with Ta content higher than 71 at.% have higher elastic moduli than the crystalline counterparts of the mechanical mixture. This is similar to the supermodulus effect observed in the multilayers in many immiscible binary alloy systems. A model based on the inter-atomic potential is proposed to explain the enhanced modulus and relate it to the additional Gibbs free energy stored in the alloy after amorphization.

To test the stability of intergranular amorphous films against crystallization, a model experiment was conducted wherein a thin SiO{sub 2} film was deposited on a single-crystal TiO{sub 2} substrate, annealed to form a eutectic liquid in equilibrium with the substrate, then quenched and crystallized below the eutectic temperature. This geometry is free of residual stresses and capillary effects proposed by others as kinetic limitations to complete crystallization. Furthermore, using a binary system removes solute rejection barriers to complete crystallization. A remnant amorphous film {approximately}1.5 nm thick retained at the hetero-interface shows unequivocally that the amorphous film is thermodynamically preferred to a crystal/crystal interface in this system.

CoNiFe-based amorphous films were magnetron-sputtered to investigate their structural and magnetic properties, including annealing-induced effects and interfacial influence from additional layers of Ta and Cu. The amorphous structure was confirmed by diffraction experiments. The magnetic measurements showed a well-defined uniaxial anisotropy in plane, arising possibly from atom oblique incidence effects competing with the stray field of the magnetron. The anisotropy could be influenced by using a Ta buffer layer, though the interfacial reaction gives rise to a dead layer. A coercive force H c of 1–2 Oe and a magnetization of 680 emu/cm3 were measured at room temperature; properties which show promise for application in magnetotunneling junction devices. Thermal analyses showed a two-stage crystallization behavior, which started at 400°C and ended at about 600°C. The Curie temperature of the amorphous phase was estimated to be about 440°C.

Influences of electron beam (EB) irradiation on magnetostriction and its susceptibility of Fe2.6Sm alloy thin films have been investigated. The alloy thin film deposited on a (100) plane of a silicon wafer is prepared by using a direct current magnetron sputtering apparatus. The irradiation enhances compressive magnetostriction and its susceptibility. The large magnetostriction of the irradiated Fe2.6Sm sample occurs, because the irradiation prevents generating the Fe3Sm crystalline with small magnetostriction. On the other hand, the high susceptibility is explained by randomization, induced by EB-irradiation, of Fe2.6Sm amorphous sample, where the magnetic moment rotates easily.

The local structure of vacuum evaporated In-Se amorphous films, containing 50, 60, and 66 at.% Se, was studied using differential anomalous X-ray scattering and extended X-ray absorption fine structure. Both intensity andabsorption spectra were measured in the vicinity of the absorption K-edge of Se. The differential anomalous X-ray scattering data were converted to real space by the inverse Fourier transform yielding the differential radial distribution functions. The obtained results provide evidence for the presence of Se-In spatial correlations for In 5 0 Se 5 0 and Se-In and Se-Se correlations for In 4 0 Se 6 0 and In 3 4 Se 6 6 within the first coordination sphere.

It is shown that the solid-state equilibrium configuration of Bi-doped ZnO grain boundaries is a nanometer-thick amorphous film. Polycrystalline Bi-doped ZnO was investigated using high-resolution transmission electron microscopy (HRTEM) and scanning transmission electron microscopy (STEM). The equilibrium state below the eutectic temperature and at 1 atm total pressure was approached from three different routes: samples were cooled from above the eutectic temperature (T{sub eutectic} = 740 C), processed entirely below the eutectic temperature, and desegregated by high applied pressure (1 GPa) followed by annealing at ambient pressure to restore segregation. In all instances, the final state is an amorphous intergranular film 1.0--1.5 nm in thickness. The results show that a thin intergranular film in this system has lower free energy than the crystal-crystal grain boundary. The implications of these results for creation of electrically active grain boundaries in zinc oxide varistors are discussed.