Analysis and Characterization of Relationships Between the Processing and Optical Responses of Amorphous BaTiO3 Nanothin Films Obtained by an Improved Wet Chemical Process

In the present work, we have tried to study and develop the processing of amorphous BaTiO₃ nanothin films, which have amorphous structure and nanometric thickness. It was seen that they exhibit enhanced optical responses. An improved method was used to prepare amorphous BaTiO₃ nanothin films, which, compared to other approaches, is simple, cost-effective, and environmentally friendly. It was found that amorphous BaTiO₃ films exhibit better optical transmittance in contrast to the similar nanocrystalline, polycrystalline, or thick films. This finding is due to the absence of grain boundaries, which have an important role in light scattering processes. AFM and SEM results indicate that the surface of the nanothin film is uniform, smooth, and amorphous. Moreover, the surface of the nanothin film exhibits a dense structure with no crack and voids. RMS roughness of the prepared nanothin film was quite small and equal to 0.7 nm. This value is very less than other reported RMS roughness values which were in the range of 5 to 11 nm. XRD results indicate that all of the prepared thin films in this work are amorphous, independent of number of dip-coated layers and preparation conditions. The work also aims to study and develop the processing of the amorphous BaTiO₃ nanothin films deeply. The results showed that annealing temperature has a more pronounced effect on transmittance, thickness, and shift in the absorption edge of the thin films than annealing time. It was found that the viscosity of the sol has remarkable influence on the transmission spectrum and shift in the absorption edge of the films. The transparency of the films decreases with an increase in the viscosity and concentration of the sol. It was found that size of particle within the sol and rate of the sol–gel reactions have important roles on the transmittance of the films.     

退火对AlCN非晶薄膜结构及力学性能的影响

利用磁控溅射方法在单晶硅基片上制备出不同Al含量AlCN非晶薄膜,随后分别在700℃和1000℃进行真空退火热处理.使用X射线衍射仪和高分辨透射电镜研究了沉积态和退火态薄膜的组织和微观结构,用纳米压痕仪测试硬度和弹性模量.结果表明,退火态薄膜组织和微观结构强烈依赖于薄膜的Al含量.经1000℃退火后,低Al含量AlCN薄膜没有出现结晶现象,但形成了分层;高Al含量AlCN薄膜中,退火促使AlN纳米晶的生成,使薄膜形成了非晶包裹纳米晶的复合结构,随着距表面深度的增加,形成的纳米晶密度和尺寸均有减小的趋势.随着退火温度的升高,AlCN薄膜的硬度和弹性模量均降低;而对于高Al含量AlCN薄膜,由于形成了纳米复合结构,硬度和弹性模量下降幅度减少.     

Microstructure and mechanical properties of sputter-deposited Cu1−x Ta x alloys

The microstructures and mechanical properties of a family of sputter-deposited Cu_1−x Ta _x (0<x<0.18) alloys have been investigated. The as-deposited microstructures for all film compositions consisted of a polycrystalline, face-centered-cubic (fcc) Cu matrix, with varying levels of Ta in solid solution, plus a very high density of discrete, 1 to 3 nm, fcc Ta particles. Decreased deposition temperature (−120 °C vs 100 °C) increased the level of Ta in solid solution. After annealing (900 °C for 1 hour) the as-deposited 6 at. pct Ta films, the Cu matrix grains remained submicron and the Ta particles remained fcc with no apparent particle coarsening. Additionally, the fcc Ta particles were found before and after annealing to be oriented identically with the Cu matrix and aligned on {111} and {100} habit planes. Annealing 17 at. pct Ta films at 900 °C for 1 hour resulted in the formation of body-centered-cubic (bcc) Ta particles (>50-nm diameter) in addition to the much smaller fcc Ta particles. Annealing the low and high Ta composition films at 900 °C for as long as 100 hours produced no observed change in either the Cu matrix grain size or the size and distribution of the fcc and bcc Ta particles. Microhardness and nanoindentation mechanical property evaluations of bulk hot-pressed materials indicated that the high strengths of the composites were unchanged, even after annealing for 100 hours at 900 °C.     

Nanocrystalline films of soft magnetic iron-based alloys

The physicochemical and structural aspects of designing soft magnetic alloys Fe-MX (where M is a Group III–V metal of the periodic table and X = C, N, O) in the form of nanocrystalline films precipitation-hardened by refractory interstitial phases are discussed and developed. The results of studying the structure and magnetic properties of Fe₇₈Zr₁₀N₁₂ films are reported. The films in the amorphous state are produced by reactive magnetron sputtering. Upon annealing at 300–600°C, the amorphous films crystallize to form mainly a bcc α-Fe-based phase and the fcc ZrN phase. The grain size of the bcc phase is shown to increase from ～3 nm to ～30 nm as the annealing temperature increases; the grain size of the fcc phase does not exceed 2–3 nm. Films annealed at 400°C exhibit a record level of magnetic properties: H _c = 5–6 A/m and B _s = 1.7–1.8 T. The experimental results obtained confirm the validity of our scientific approach.     

Kinetics of interaction of tantalum disilicide with tantalum and other metals

The rate of growth of Ta₅Si₃ in the Ta?TaSi₂ system has been measured with good accuracy in the temperature range of 1150° to 1370°C (2100° to 2500°F) using couples consisting of dense wafers of the components. The isothermal growth is shown to be parabolic and the temperature dependence of the growth constant is given byk=5 exp (?77,000/RT) It has been shown that tantalum diffusion is negligible by comparison with silicon diffusion. The Ta₅Si₃ was found to exist in both tetragonal and hexagonal forms. A more limited investigation of silicon loss from TaSi₂ to W, Mo, Nb, Zr, Ti, and Re indicates that none of these is superior to tantalum in limiting the degradation of the tantalum disilicide. In most instances a layer of composition M₅Si₃ forms on the metal side of the couple.     

Adhesion Behaviour,Nanohardness and Surface Roughness of Ti–6Al–4V–6B<Subscript>4</Subscript>C Thin Films Grown on AISI 1040 Steel

The nanohardness of Ti–6Al–4V–6B₄C thin film coated AISI 1040 steel were investigated using nanoindentation based on an AFM measurement technique. Thin films of Ti–6Al–4V–6B₄C were grown by the magnetron sputtering deposition method. X-ray diffraction analysis revealed that the deposited thin films were highly purified. The nanohardness of 18, 14 and 11.3 GPa were obtained for the coating of Ti–6Al–4V–6B₄C, Ti–6Al–4V, and bare substrate respectively. The surface roughness (R_a) of 0.5 and 1 h coating were 3.39 and 15.74 nm respectively. The results showed that the B₄C particles had a significant effect on the microstructural and mechanical properties of the coatings. The Ti–6Al–4V–6B₄C coating was obtained for a coating thickness of 40 and 100 nm for 0.5 and 1 h coating time respectively. In the meantime, the respective coating thickness of Ti–6Al–4V was obtained as 30 and 80 nm for 0.5 and 1 h coating time respectively. Strong adhesion was observed between the Ti–6Al–4V–6B₄C coating and AISI 1040 steel substrate than Ti–6Al–4V samples. The adhesion mechanism between the Ti–6Al–4V–6B₄C coating, AISI 1040 steel substrate, and the interfacial structure were studied by using scanning electron microscope (SEM). The use of Ti–6Al–4V–6B₄C coating could be a novel technique for developing high-performance applications due to excellent adhesion and nanohardness.     

The oxidation resistance of alloys of zirconium boride with molybdenum disilicide

Summary A study was made of the oxidation of pure zirconium boride and alloys of zirconium boride with molybdenum disilicide-(ZrB_1.9)₂₃MoSi_1.1 and (ZrB_1.7)₁₃MoSi_1.2-obtained by sintering a mixture of zirconium boride with 5 and 10% molybdenum disilicide. The rate of oxidation was determined from the time dependences of specimen weight and oxide film thickness. On the basis of the kinetic oxidation curves and microstructural analysis, conclusions are drawn regarding the nature of the resultant oxide films. Alloys of zirconium boride with molybdenum disilicide have high oxidation resistance at up to 1550°C as a result of the formation of a borosilicate film on the surface.     

Methods of production, structure, and properties of film materials based on the carbon—nitrogen system (survey)

About 50 papers devoted to producing and investigating the properties of carbon nitride films are critically reviewed. It is shown that reasonable experimental confirmation of synthesis of the hypothetical β-C₃N₄ does not yet exist. Carbon nitride films can be produced practically by all PVD and CVD methods. They may contain up to 50% nitrogen, have an amorphous structure, and atoms in carbon nitride sp²-bonded. The microstructure of amorphous CN films is mostly based on two types of clusters—cyanogen polymers and graphite-like domains with carbon atoms partially substituted by nitrogen. The relation between two microstructure types depends on the deposition conditions and crucially influences the film properties. The smaller the graphite-like clusters size and the more chaotically they are oriented in the film the harder will be the film. The factor which influences most the type of film microstructure and properties is the ion bombardment of the film during the deposition. The small friction coefficient, high elasticity, and relatively high hardness of nitride carbon films may make them useful as protective coatings of a storage medium in computers.     

Grain-size effect on shape-memory behavior of Ti35.0Ni49.7Zr15.4 thin films

The grain-size effect on shape-memory behavior of fine-grained Ti_35.0Ni_49.7Zr_15.4 thin films was investigated by transmission electron microscopy. The films, with various grain sizes ranging from about 150 to about 400 nm, were prepared by heat treatment of amorphous films at the three different annealing temperatures of 773, 873, and 973 K, for three different annealing times of 5 minutes, 1 hour, and 10 hours. The film annealed at 773 K for 5 minutes showed a nearly single phase of (Ti,Zr)Ni, while the films annealed at high annealing temperatures and/or long annealing times showed λ ₁ precipitates. For a high annealing temperature of 973 K, the critical yield stress (σ _c) was dominantly dependent on the grain size of the matrix, obeying the Hall-Petch equation. On the other hand, for a low annealing temperature of 773 K, σ _c was dominantly dependent on the amount of λ ₁ precipitates. The M _S temperature decreases almost linearly with increasing σ _c. The films showed sufficient fracture toughness, probably due to the nanometer scale of the grain size and the agglomerated shape of λ ₁ particles.     

Texture Evolution of Abnormal Grains with Post-Deposition Annealing Temperature in Nanocrystalline Cu Thin Films

We have examined the evolution of abnormal grain growth texture with increasing post-deposition annealing temperature in nanocrystalline Cu films (20 nm thick) deposited on an amorphous SiN _x (20 nm)/Si substrate. Texture is analyzed by a TEM-based orientation and phase mapping technique based on precession electron diffraction. The as-deposited film, which has an initial grain size of ~12 nm in diameter, already shows a signature of abnormal grain growth, exhibiting a bimodal grain size distribution. Texture is analyzed by calculating area fractions of major components. The overall texture of the as-deposited film is identified to be ??110??, but ??100?? grains occupy the largest fraction in the abnormally grown grain areas, followed by ??111?? grains. After annealing at 398 K, 573 K, and 773 K (125 °C, 300 °C, and 500 °C), the overall texture turns to ??112??. After annealing at 398 K (125 °C), abnormally grown grains have a major ??112?? component. The situation is similar for the film annealed at 573 K (300 °C). After annealing at 773 K (500 °C), the abnormal grain growth texture evolved into major ??111??. The ??100?? component found in the abnormal grain growth texture for the as-deposited film is clearly explained by elastic strain energy minimization and the ??111?? component for the as-deposited film and the film annealed at 773 K (500 °C) is explained by surface energy minimization. The development of the ??112?? texture obtained after annealing at 398 K and 573 K (125 °C and 300 °C) is not explained by either elastic strain energy minimization or surface energy minimization. We suggest that it is clarified by assuming that the Cu film system is perfectly elastic?Cplastic, which is associated with the Taylor factors.     

Structural disordering in WC thin films induced by SiC additions

An investigation has been conducted into the structural disordering in WC thin films induced by SiC additions. The effect of this disordering on film hardness is also reported. In this investigation, WC-SiC films with a SiC content varying from 11.6 to 38.2 pct were deposited using dual rf magnetron sputtering. The relative Si and W content in the films was determined using electron microprobe analysis. Analysis by X-ray diffraction (XRD) confirmed that, within this compositional range, the film structure transformed from crystalline to amorphous. The XRD patterns showed that the crystalline films consisted primarily of WC_1−x , along with a small amount of W₂C; no clear evidence for a separate crystalline SiC phase was found. High-resolution transmission electron microscopy (HRTEM) studies showed that with a lower Si content, the films consisted of crystallites 3 to 5 nm in diameter embedded in an amorphous phase. As the Si content increased, the amorphous phase content increased, both as interlayers between crystallites and as particles within the crystallites. Further Si increases led to a structure consisting of a high density of interconnected amorphous particles within well-defined semicrystalline domains separated by a thin amorphous interlayer. At the highest Si content, a clear two-phase morphology evolved, consisting of two nearly amorphous but distinct phases, which suggests a fine-scale partial-phase separation between the WC and the SiC. At the atomic level, it was found that Si decreased the coherence length within the crystalline phase, resulting in a structure of mixed crystalline/highly disordered phases scaled in the range of 2 to 4 nm. Despite the significant alterations in the film structures due to SiC additions, the hardness and modulus of the films were essentially constant within the compositional range of the transition, although films with SiC contents of less than ∼11 pct had significantly lower hardness levels. It is proposed that the effects of Si on hardness can be explained in terms of competition between the percolation threshold and the amorphization-inducing effect of Si.     

Synthesis and characterization of Ti-Si-C-N films

This study represents one of the first attempts to deposit multicomponent (more than three components) thin films by magnetron sputtering of multiphase composite targets (three phases or even more). Films of Ti-Si-C-N were synthesized through dc magnetron sputtering of xTiC+yTi₃SiC₂+zA composite targets (A was TiSi₂, SiC, or a mixture of these phases) in an argon atmosphere or in a gaseous mixture of argon and nitrogen. The as-deposited films were characterized using Auger electron spectroscopy, X-ray diffraction, transmission electron microscopy using selected area electron diffraction and high-resolution techniques, and microhardness. It was shown that the substrate temperature and the nitrogen concentration in the reactive gas had a strong influence on the structure and the composition of the as-deposited films. The films deposited from the Si-poor targets were either polycrystalline or contained a mixture of nanocrystalline and amorphous phases. An amorphous phase formed as individual grains rather than as intergrain amorphous layers. All films deposited from the Si-rich target were amorphous in nature. Particular attention has been paid to the atomic structure of grains and grain boundaries in the crystalline films. Polycrystalline grains contained a high density of dislocations and exhibited a curved appearance of the lattice fringes that is probably due to the presence of the long-range stress fields. The measurements of the lattice parameters using the selected area electron diffraction pattern (SA EDP) method indicated, with a high probability, that the polycrystalline grains consist of clusters of atoms with varying compositions. The grain boundaries in the nanocrystalline Ti-Si-C-N films had both ordered and disordered regions, although some regions close to the interface exhibited neither a fully crystalline nor a homogeneously amorphous structure. The atomic structure of an interface was shown to depend on the orientation relationship between adjacent grains. The atomic planes were perfectly matched when the two grains were oriented close to the [110] _fcc1//[110] _fcc2 zone axis. However, the interface dislocations were frequently observed at or near the grain boundary when [110] _fcc1//[001] _fcc2. The contribution of compressive stress as determined by an increase in the fcc lattice parameter is also discussed.     

Development of Mathematical Model for Prediction and Optimization of Particle Size in Nanocrystalline CdS Thin Films Prepared by Sol-Gel Spin-Coating Method

Nanocrystalline CdS thin films have been prepared by the sol-gel spin-coating method. The influence of spin-coating process parameters such as, thiourea concentration (U), annealing temperature (A), rotational speed (S), and annealing time (T), and so on, on the properties of the prepared films have been studied. The experiments have been carried out based on four factor-five-level central composite designs with the full replication technique, and mathematical models have been developed using regression technique. The central composite rotatable design has been used to minimize the number of experimental parameters. The analysis of variance technique is applied to check the validity of the developed models. The developed mathematical model can be used effectively to predict the particle size in CdS nanocrystalline thin films at 95 pct confidence level. The results have been verified by depositing the films using the same condition. An ultraviolet-visible optical spectroscopy study was carried out to determine the band gap of the CdS nanocrystalline thin films. The band gap has been observed to depend strongly on particle size, and it indicated a blue shift caused by quantum confinement effects. The high-resolution transmission electron microscopy analysis showed the grain size of the prepared CdS film to be 6 nm. The main and interaction effects of deposition parameters on the properties of CdS nanocrystalline thin films also have been studied.     

Influence of Melt-Spinning Parameters on the Structure and Soft Magnetic Properties of (Fe0.65Co0.35)88Zr7B4Cu1 Alloy

Melt-spun ribbons of (Fe_0.65Co_0.35)₈₈Zr₇B₄Cu₁ alloy have been prepared at different wheel speeds, namely, 47, 39, 34, and 17 m/s, and subsequently annealed at 773 K (500 °C) under controlled atmosphere. Structural and soft magnetic properties have been evaluated using X-ray diffraction, differential scanning calorimetry, transmission electron microscopy, and vibrating sample magnetometer. The structure of as-spun ribbons changes from fully amorphous to partially amorphous/nanocrystalline to fully nanocrystalline (bcc α-Fe(Co) + Fe₂Zr) on decreasing the wheel speed. Annealing of amorphous ribbons leads to the precipitation of nanocrystalline bcc α-Fe(Co) phase. The Curie temperature (T _c ) of the amorphous phase is found to increase with decreasing wheel speed possibly due to the effect of exchange field penetration of nanocrystals present in the amorphous matrix. The saturation magnetization (4πM _s ) of as-spun ribbons having partially nanocrystalline bcc α-Fe(Co) phase is high as compared to the ribbons with completely amorphous phase, and it remains almost the same even after annealing. The lowest coercivity has been achieved in the ribbons that are fully amorphous, and the coercivity was found to increase with decreasing wheel speed.     

Structural characterization of Nd-doped in silica host matrix prepared by wet chemical process

Silica host matrix containing neodymium which is potentially important for the formation of nanocrystalline metal oxides was prepared by solgel method, using tetra-ethoxysilane and Nd(NO₃)₃ as precursor materials. The prepared samples were changed from amorphous to nanocrystallites phase at sintered temperature 550 °C (4 h), 750 °C (8 h) and 950 °C (12 h). The thermally treated sample microstructures were investigated using X-ray diffraction (XRD), Fourier transformation infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). While a further increase of the temperature at 750 °C and annealing time (8 h) resulted in the formation of cubic and hexagonal Nd₂O₃ nanocrystallites. At constant sintering temperature 950 °C for 12 h, the samples showed sharper and intense peaks. The sizes of Nd₂O₃ nanocrystallites were characterized by XRD with average size ～46 nm.     

Defect structures in cosputtered thin films of transition-metal disilicides with C11<Subscript><Emphasis Type="Italic">b</Emphasis></Subscript>, C40 and C54 structures

Defect structures in crystallites of the stable phases in thin films of transition-metal (TM) disilicides (C11 _b MoSi₂, C40 TaSi₂, and C54 TiSi₂) produced by cosputtering and subsequent annealing have been investigated by transmission electron microscopy (TEM). Crystallites in thin films of MoSi₂, TaSi₂, and TiSi₂ all contain planar faults parallel to hexagonally arranged TMSi₂ planes, which are a characteristic feature commonly observed in all three crystal structures. These planar faults are twin boundaries in all cases. Twins in thin films of these disilicides, thus, have a common characteristic that the twin habit plane is parallel to hexagonally arranged TMSi₂ stoichiometric planes. For twins in thin films of C11 _b MoSi₂, and C54 TiSi₂, the twining elements can be deduced and the twin habit plane is found not to be parallel to the twinning (K ₁) plane, but to be perpendicular to it. Twins formed in C40 TaSi₂ thin films are different from those formed in C11 _b MoSi₂ and C54 TiSi₂ thin films, in that the crystal orientation of the twin is exactly the same as that of the matrix, since they are racemic twins that are only enantiomorphically (space groups of P6₂22 or P6₄22) related to each other. This article is based on a presentation in the symposium “Terence E. Mitchell Symposium on the Magic of Materials: Structures and Properties” from the TMS Annual Meeting in San Diego, CA in March 2003.     

Effect of magnetic layer thickness on magnetic properties of Ce-Fe-B thin films

The Ce_2 Fe_(14)B thin films with a notable out-of-plane c-axis texture were prepared by DC magnetron sputtering on a Ta buffer layer. The morphological and magnetic properties were investigated. The thickness of the magnetic layer had a dramatic effect on the formation of Ce_2 Fe_(14)B phase,and excellent magnetic properties(H_(ci)≈4.25 kOe, M_r/M_s≈0.81) were observed for the Ce-Fe-B film with the thickness d_m = 200 nm. The results of the hysteresis loops for Ce-Fe-B film(d_m = 200 nm) at various measured temperatures show that a decoupling between the hard and the soft phases is observed at low temperatures, which is due to the regions with quite low anisotropy provided by the a-Fe. Moreover. it is clear that significantly various magnetization behaviors between the films with d_m = 200 and 300 nm were observed with a similar trend due to the existence of the a-Fe soft phase.     

Interdiffusion of Fe and Mg layers during annealing and deuterium absorption

Abstract

We compared the interdiffusion of a Ta/Mg/Fe/Ta/Pd thin film system after deuterium absorption and desorption at 250°C with an annealing of the film structure to 250°C. The combined X-ray and neutron reflectometry study shows that the layers start to interdiffuse at 250°C with the film structure still clearly visible. In contrast, after deuterium absorption and desorption the changes of the film structure are more severe. We observe an intermixing of the Mg/Fe/Ta/Pd layers with only the bottom Ta layer staying intact.     

Structure and Electrochemical Activity of C60 Fullerite Films

Results are presented from structural and electrochemical researches on C₆₀ films. The fullerite films were made by thermal vacuum evaporation and deposition on NaCl crystals. The substrate temperatures were 293-473 K. The examinations were made in a transmission electron microscope at 100 kV and by x-ray diffraction. Dark-field images were obtained from the individual fullerite particles and particularly from grains in continuous thin films, which showed stacking faults or twin boundaries. The numbers of these defects increase with the substrate temperature. The x-ray diffraction patterns of the fullerite films show extremely diffuse reflections together with a weak reflection around the FCC (111), which may be assigned to a hexagonal close packed HCP modification of fullerite. Rietveld's method was used in processing the x-ray patterns. The best fit between the experimental and theoretical diffraction lines was obtained with the following structure parameters: ratio of FCC phase (a = 1.4117 nm) and HCP phase (a = 0.9756 nm and c = 1.7084 nm) was 46/54 mass%. The electrochemical data indicate that a palladium-activated fullerite film shows prominent hysteresis, which confirms that certain hydride phases are formed at the surface of the C₆₀ film.

     

Structure and Electrochemical Activity of C60 Fullerite Films

Results are presented from structural and electrochemical researches on C₆₀ films. The fullerite films were made by thermal vacuum evaporation and deposition on NaCl crystals. The substrate temperatures were 293-473 K. The examinations were made in a transmission electron microscope at 100 kV and by x-ray diffraction. Dark-field images were obtained from the individual fullerite particles and particularly from grains in continuous thin films, which showed stacking faults or twin boundaries. The numbers of these defects increase with the substrate temperature. The x-ray diffraction patterns of the fullerite films show extremely diffuse reflections together with a weak reflection around the FCC (111), which may be assigned to a hexagonal close packed HCP modification of fullerite. Rietveld's method was used in processing the x-ray patterns. The best fit between the experimental and theoretical diffraction lines was obtained with the following structure parameters: ratio of FCC phase (a = 1.4117 nm) and HCP phase (a = 0.9756 nm and c = 1.7084 nm) was 46/54 mass%. The electrochemical data indicate that a palladium-activated fullerite film shows prominent hysteresis, which confirms that certain hydride phases are formed at the surface of the C₆₀ film.