Phase separation in immiscible silver–copper alloy thin films

Far from equilibrium, immiscible nanocrystalline Ag–Cu alloy thin films of nominal composition Ag–40 at.% Cu have been deposited by co-sputter deposition. Both X-ray and electron diffraction studies indicate that the as-deposited films largely consist of nanocrystalline grains of a single alloyed face-centered cubic (fcc) phase. However, detailed three-dimensional atom probe tomography studies on the same films give direct evidence of a nanoscale phase separation within the columnar grains of the as-deposited Ag–Cu films. Subsequent annealing of these films at 200 °C leads to two effects; a more pronounced nanoscale separation of the Ag and Cu phases, as well as the early stages of recrystallization leading to the breakdown of the columnar grain morphology. Finally, annealing at a higher temperature of 390 °C for a long period of time leads to complete recrystallization, grain coarsening, and a complete phase separation into fcc Cu and fcc Ag phases.     

Si<Subscript>3</Subscript>N<Subscript>4</Subscript>/TiN composites produced from TiO<Subscript>2</Subscript>-Modified Si<Subscript>3</Subscript>N<Subscript>4</Subscript> powders

Si₃N₄/TiN composites have been produced by hot pressing at temperatures from 1600 to 1800°C in a nitrogen atmosphere, using silicon nitride powders prepared by self-propagating high-temperature synthesis and surface-modified with titanium dioxide nanoparticles. We examined the effect of TiO₂ content on the microstructure, phase composition, and mechanical strength of the ceramics. It is shown that titanium nitride can be formed by the reaction Si₃N₄ + TiO₂ → TiN + NO + N₂O + 3Si. The Si₃N₄/TiN composites containing 5–20% TiN have a low density, high porosity, and a bending strength of 60 MPa or lower. In Si₃N₄/TiN ceramics produced using calcium aluminates as sintering aids, the silicon nitride grains are densely packed, which ensures an increase in strength to 650 MPa.     

Structural, morphological, and mechanical properties of amorphous carbon and carbon nitride thin films deposited by reactive and ion beam assisted laser ablation

Amorphous carbon nitride thin films have been prepared on Si (100) wafers by nitrogen ion beam assisted Nd:YAG laser ablation techniques. Amorphous carbon and carbon nitride films have also been prepared by the conventional laser ablation techniques for comparison. Raman spectroscopy and spectroscopic ellipsometry have been performed for the films to analyze structural properties, atomic force microscopy to observe surface morphologies, and scratch, acoustic emission, and Vicker hardness test to examine mechanical properties. The amorphous carbon nitride films deposited by the ion beam assisted laser ablation techniques had generally better mechanical properties compared to the amorphous carbon films and amorphous carbon nitride films deposited in N₂ atmosphere. The amorphous carbon nitride films deposited at optimum ion beam current of 10 mA and laser power density of 1.7 × 10⁹ W/cm² showed excellent mechanical properties: root mean square surface roughness of 0.33 nm, friction coefficient of 0.02–0.08, the first crack and critical load of 11.5 and 19.3 N respectively, and Vicker hardness of 2300 [Hv]. It is considered that the films have high potential for protective coatings for microelectronic devices such as magnetic data storage media and heads.     

Synthesis of nanocrystalline ZrO<Subscript>2</Subscript> with tailored phase composition and microstructure under high-power sonication

The effect of sonication on the composition and properties of zirconia precipitated from aqueous zirconyl nitrate solutions at various pH values has been studied using thermal analysis, X-ray diffraction, and low-temperature nitrogen adsorption measurements. The results demonstrate that acoustic processing considerably reduces the content of sorbed ions in amorphous ZrO₂ · xH₂O gels and allows one to control the composition and microstructure of the nanocrystalline zirconia produced through thermal decomposition of the gels.     

Multi-phase structured silicon carbon nitride thin films prepared by hot-wire chemical vapour deposition

In this work, Silicon Carbon Nitride (Si-C-N) thin films were deposited by Hot Wire Chemical Vapour Deposition (HWCVD) technique from a gas mixture of silane (SiH₄), methane (CH₄) and nitrogen (N₂). Six sets of Si-C-N thin films were produced and studied. The component gas flow rate ratio (SiH₄:CH₄:N₂) was kept constant for all film samples. The total gas flow-rate (SiH₄ + CH₄ + N₂) was changed for each set of films resulting in different total gas pressure which represented the deposition pressure for each of these films ranging from 40 to 100 Pa. The effects of deposition pressure on the chemical bonding, elemental composition and optical properties of the Si-C-N were studied using Fourier transform infrared (FTIR) spectroscopy, Auger Electron Spectroscopy (AES) and optical transmission spectroscopy respectively. This work shows that the films are silicon rich and multi-phase in structure showing significant presence of hydrogenated amorphous silicon (a-Si:H) phase, amorphous silicon carbide (a-SiC), and amorphous silicon nitride (a-SiN) phases with Si-C being the most dominant. Below 85 Pa, carbon content is low, and the films are more a-Si:H like. At 85 Pa and above, the films become more Si-C like as carbon content is much higher and carbon incorporation influences the optical properties of the films. The properties clearly indicated that the films underwent a transition between two dominant phases and were dependent on pressure.     

Synthesis and optical properties of CeO<Subscript>2</Subscript> nanocrystalline films grown by pulsed electron beam deposition

The nanocrystalline cerium dioxide (CeO₂) thin films were deposited on soda lime (SLG) and Corning glass by pulsed e-beam deposition (PED) method at room temperature. The structure of the produced CeO₂ thin films was investigated by X-ray diffraction (XRD) analysis, X-ray photoelectron spectroscopy (XPS), and micro Raman spectroscopy. The surface topography of the films was examined by atomic force microscopy (AFM). Film thickness and growth morphologies were determined with FEG-SEM from the fracture cross sections. XPS studies gave a film composition composed of +4 and +3 valent cerium typical to nanocrystalline ceria structures deficient in oxygen. The ceria films were polycrystalline in nature with a lattice parameter (a) of 0.542 nm. The Raman characteristics of the source material and the films deposited were very similar in character. Raman lines for thin film and bulk CeO₂ was observed at 465 cm⁻¹. The optical properties of the CeO₂ films were deduced from reflectance and transmittance measurements at room temperature. From the optical model, the refractive index was determined as 1.8–2.7 in the photon energy interval from 3.5 to 1.25 eV. The optical indirect band gap (E _g) of CeO₂ nanocrystalline films was calculated as 2.58 eV.     

Structure of heterosystems formed by a SnO<Subscript>2</Subscript> film and island metal (Ag,Au, or Pd) condensate

We have studied the phase composition and microstructure of thin tin(IV) oxide films surfacemodified with silver, gold, and palladium nanoislands. Using high-energy electron diffraction, we have shown for the first time that the thermal oxidation of the Sn films leads to the formation of nanocrystalline multiphase SnO₂ films in which the major phase is orthorhombic. Also present are (in order of decreasing content) tetragonal and cubic phases. Blocks of SnO₂(O) subgrains with 〈101〉 texture contain dislocations and stacking faults, which are interpreted as layers of the tetragonal phase. It has been shown that vacuum condensation makes it possible to modify the surface of SnO₂ films with noble metals and obtain homogeneous nanoisland coatings characterized by a unimodal, uniform island size distribution.     

Fe<Subscript>73.5</Subscript>Cu<Subscript>1</Subscript>Nb<Subscript>3</Subscript>Si<Subscript>15.5</Subscript>B<Subscript>7</Subscript> Thin Films Deposited by HiPIMS: Magnetic and Magnetostrictive Behavior

Results concerning the magnetic, magnetostrictive, structural, morphological, and topological properties of amorphous and nanocrystalline Fe _73.5Cu ₁Nb ₃Si _15.5 B ₇ thin films deposited using the high power impulse magnetron sputtering (HiPIMS) technique are reported. In as-deposited state, the samples are amorphous, the nanocrystalline state being achieved for samples isothermally annealed at adequate temperatures, in an electric furnace. For the optimum annealing temperature (475 ^°C), a decrease by about 70 % for the coercive magnetic field (50 A/m) and up to 1 order of magnitude for the saturation magnetostriction (~1×10^?6), compared to the as-deposited state, was obtained. The X-ray diffractometry (XRD) and scanning electron microscopy (SEM) results for samples thermally treated at 475 ^°C revealed a 53.6 % crystalline volume fraction of α-Fe(Si) nanograins with an average size of about 15 nm and a Si content of 10.78 %, uniformly dispersed in a residual amorphous matrix. Using the saturation magnetostriction values determined using the cantilever deflection method and the crystalline volume fraction of α-Fe(Si) nanograins, the contribution of crystalline phase to the saturation magnetostriction was also determined.     

Mechanical properties and density of BC<Emphasis Type="Italic">x</Emphasis>N<Emphasis Type="Italic">y</Emphasis> films grown by low-pressure chemical vapor deposition from triethylamine borane

Boron carbonitride (BC _x N _y ) films of different compositions have been grown by low-pressure chemical vapor deposition using triethylamine borane as a single-source precursor and ammonia as an additional nitrogen source. Experiments were performed at various initial vapor compositions. The resultant films have been characterized by ellipsometry, IR spectroscopy, energy dispersive X-ray spectroscopy, scanning electron microscopy, nanoindentation, and surface acoustic wave spectroscopy. The mechanical properties of the films are shown to correlate with their density and chemical composition. With increasing initial ammonia partial pressure in the vapor phase, the elemental composition of the films moves away from boron carbide, approaching boron nitride, which is accompanied by a reduction in the Young’s modulus, hardness, and density of the films.     

Structural and mechanical characterization of BCxNy thin films deposited by pulsed reactive magnetron sputtering

BC_xN_y thin films deposited at 250 °C by pulsed reactive magnetron sputtering of a B₄C target in an Ar/N₂ plasma were studied by elastic recoil detection analysis, Fourier transform infrared, Raman, and photoelectron spectroscopy, electron microscopy, and nanoindentation. In the concentration range of 6% to 100% N₂ in the sputter plasma the segregation into nanocrystalline hexagonal boron nitride and amorphous sp² carbon is the dominant process during the film growth. The stoichiometric ratio and structural details of the major phases depend on the N₂ concentration in the plasma and have significant influence on the Young′s modulus and the elastic recovery of the BC_xN_y thin films.     

Effect of deposition pressure on the adhesion and tribological properties of a-CN<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>H films prepared by DC-RF-PECVD

Hydrogenated carbon nitride (a-CN _x H films) was deposited on n-type single-crystal Si (100) by direct current radio frequency plasma-enhanced chemical vapor deposition (DC-RF-PECVD), under the working pressure of 5.0–17.0 Pa, using the CH₄ and N₂ as feedstock. The composition and surface morphology of the a-CN _x H films were characterized by means of Raman spectroscopy and atomic force microscopy, while the Young’s modulus, elastic recovery, adhesion strength, and tribological properties were evaluated using nano-indentation, scratch test and friction test system. It was found that the surface roughness and Raman spectra peak intensity ratio I _D/I _G of the films increased with the increase of working pressure, while the Young’s modulus, elastic recovery and adhesion strength of the films significantly decreased. Moreover, the tribological properties of the films also varied with the working pressure. The wear life sharply increased with the increase of working pressure from 5.0 Pa to 7.5 Pa, further, an increase in the deposition pressure led to a gradual decrease in the wear life, consequently, the a-CN _x H film deposited at 7.5 Pa exhibited the longest wear life. The deposition pressure seemed to have slight effect on the average friction coefficients, whereas the surface roughness and adhesion strength have deteriorated with increasing deposition pressure.     

Effect of N<Subscript>2</Subscript> gas annealing and SiO<Subscript>2</Subscript> barrier on the optical transmittance and electrical resistivity of a transparent Sb-doped SnO<Subscript>2</Subscript> conducting film

During the fabrication process of transparent conducting thin films of ATO (antimony-doped tin oxide) on a soda lime glass substrate by a sol-gel dip coating method, the effects of the SiO₂ buffer layer formed on the substrate and N₂ annealing treatment were investigated quantitatively. The deposited ATO thin film was identified as a crystalline SnO₂ phase and the film thickness was about 100 nm/layer at a withdrawal speed of 50 mm/min. Optical transmittance and electrical resistivity of the 400 nm-thick ATO thin film that was deposited on SiO₂ buffer layer/soda lime glass and then annealed under nitrogen atmosphere were 84% and 5.0 × 10^–3cm, respectively. The XPS analysis confirmed that a SiO₂ buffer layer inhibited Na ion diffusion from the substrate, preventing the formation of a secondary phase such as Na₂SnO₃ and SnO and increasing Sb ion concentration and ratio of Sb⁵⁺/Sb³⁺ in the film. It was found that N₂ annealing treatment leads to the reduction of Sn⁴⁺ as well as Sb⁵⁺, however the reduction of Sn⁴⁺ is more effective, and consequently results in a decrease in the electrical resistivity to produce excellent electrical properties in the film. © Springer Science + Business Media, Inc.     

Transmission electron microscopy of nanocomposite CrB-N thin films

This paper reports on the preparation and characterization of CrBN nanocomposite coatings for low friction, low wear and high thermostability applications. Sputtered CrBN thin films were prepared in order to obtain a composite structure consisting of hard CrB₂ and CrN crystallites as well as hexagonal BN lubricant phase by unbalanced magnetron sputtering (UBM) of a CrB₂ target in an Ar/N₂ gas discharge. Coatings, with a total thickness of 4.5-5.5 μm, were deposited at 450 °C on silicon single-crystal substrates. A nanocomposite structure was obtained by increasing the nitrogen content of the sputtering gas. The coating microstructure was investigated on selected samples by high-resolution transmission electron microscopy. The films were generally found to consist of crystallites of a 1-4 nm size embedded in amorphous matrix. This crystalline phase was identified by electron diffraction as hexagonal CrB₂ for low nitrogen content and cubic CrN for high nitrogen content. In the medium composition range, the structure was amorphous, still keeping the two-phase morphology. The use of high-resolution imaging mode helped to reveal the composition of the amorphous phase which seems predominantly to consist of boron nitride.     

An investigation in InGaO<Subscript>3</Subscript>(ZnO)<Subscript>m</Subscript> pellets as cause of variability in thin film transistor characteristics

Indium–gallium–zinc oxide (IGZO) is a novel amorphous oxide semiconductor, which recently has received much attention for thin film transistors (TFTs) in flat panel displays. Published literature reports significant variations in the properties of thin films and TFTs prepared from IGZO even though the reported process conditions are similar. We demonstrate that these differences could arise from the method for preparation of targets from which the films are made. Accordingly, we also propose simple and appropriate conditions, specifically using much lower sintering temperatures and thus avoiding use of sealed Pt tubes for preparation of IGZO targets in composition range, InGaO₃(ZnO) _m , with 1 ≤ m ≤ 5. These target materials are suitable in physical vapour deposition processes such as pulsed laser deposition and sputtering. In developing the process for sintering, the phase analysis of the target pellets was carried out using X-ray diffraction (XRD). The chemical compositions of the phases are also confirmed with inductively coupled plasma optical emission spectrometry (ICP-OES) and energy dispersive X-ray (EDX) techniques. We also demonstrate successful deposition of amorphous IGZO thin films by pulse laser deposition using the targets prepared by the proposed sintering process. Finally, we demonstrate that unmonitored method of making pellets for films deposition is a cause of variability associated in published literature on IGZO TFTs.     

Nb–Al–N thin films: Structural transition from nanocrystalline solid solution nc-(Nb,Al)N into nanocomposite nc-(Nb,Al)N/a–AlN

Structures and mechanical properties of thin films of the Nb–Al–N system produced by magnetron sputtering of targets from niobium and aluminum in the Ar–N₂ atmosphere have been studied. It has been shown that as the aluminum concentration increases, the structure of a thin film transforms from the nanocrystalline into the nanocomposite one, which consists of nanocrystallites of solid solutions in a matrix of amorphous aluminum nitride. Hardness, elastic modulus, and yield strength of Nb–Al–N thin films have been studied by nanoindentation in the mode of continuous control of the contact stiffness. It has been found that the transition of the structures of Nb–Al–N thin films from the nanocrystalline to the nanocomposite structures results in an increase of hardness and decrease of elastic modulus due to the formation of a thin amorphous interlayer between grains of nanocrystallites. A high hardness to elastic modulus ratio of Nb–Al–N nanocomposite thin films indicates that the films are a promising material for wear-resistant coatings.     

Nitrogen-substituted TiO<Subscript>2</Subscript>: investigation on the photocatalytic activity in the visible light range

Nitrogen-doped titanium oxides are attractive materials for the degradation of organic pollutants in water due to their photocatalytic activity in the visible light range. The evolution of the photocatalytic properties was studied on a number of TiO _x N _y powder samples where x varied from 2 to 0 (TiO₂ to TiN) through increasing the nitrogen content (y = 0–1). X-ray diffraction and Raman spectroscopy showed that an anatase type TiO _x N _y was obtained at low nitrogen contents (<2 wt%). With increasing nitrogen content a structural transition from anatase to cubic TiN was observed. Electron spin resonance measurements of the TiO _x N _y samples confirmed the presence of unpaired electrons and defects for the TiO _x N _y materials with low nitrogen content (<2 wt%). The photo-induced activity of the TiO _x N _y materials was evaluated under VIS illumination of solutions containing methylene blue as an organic probe. The TiO _x N _y samples exhibited an improved photocatalytic activity under visible light illumination compared to TiO₂ at nitrogen levels lower than 2 wt%. A photocatalytic activity could not be detected at nitrogen levels higher than 10 wt% and after conversion of the TiO _x N _y into the cubic phase. Optimum photocatalytic activity in the visible range can be achieved at nitrogen levels lower than 2 wt% for TiO _x N _y materials.     

Influence of radio frequency power on structure and ionic conductivity of LiPON thin films

Lithium phosphorus oxynitride (LiPON) thin films as solid electrolytes were prepared by radio frequency magnetron sputtering of a Li₃PO₄ target in ambient nitrogen atmosphere. The influence of radio frequency (rf) power on the structure and the ionic conductivity of LiPON thin films has been investigated. The morphology, composition, structure and ionic conductivity of thin films were characterized by scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy and a.c. impedance measurement. It was found that ionic conductivity of LiPON thin films increases with N content in thin films. XPS measurements reveal that ionic conductivity also keeps relativity with the structure of thin films. Higher the N _t/N _d ratio, higher will be the ionic conductivity of LiPON thin films. And both of them can be improved by increasing rf power from 1·5 W/cm² to 5·5 W/cm².     

Structural transformations in thin Ge<Subscript>2</Subscript>Sb<Subscript>2</Subscript>Te<Subscript>5</Subscript> films

Structural transformations in thin Ge₂Sb₂Te₅ films for phase-change memory applications have been studied by differential scanning calorimetry. As-grown, amorphous films have been shown to undergo structural transitions to a cubic and then to a hexagonal phase. A reproducible endothermic peak has been detected, which had not been reported earlier. A mechanism for the underlying process has been proposed.     

Magnetic and structural properties of Fe<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Pt<Subscript>100−<Emphasis Type="Italic">x</Emphasis></Subscript> on MgO(110) substrates

Fe _x Pt_100−x (70.1 ≤ x ≤ 83.4) thin films with ordered Fe₃Pt phase were grown successfully onto MgO(110) substrates by electron beam evaporation. The unit cell of ordered Fe₃Pt phase is elongated along c-axis direction and the thin films become more chemically ordered with decreasing Fe content. The magnetization of thin films shows a decrease when Fe content is around 79 at.%. The relationship between magnetic anisotropy and structural parameters suggests that the change of magnetic anisotropy in ordered Fe₃Pt thin films with different compositions most likely stems from the magnetocrystalline origin.     

Evolution of the microstructure and mechanical properties of eutectic Fe<Subscript>30</Subscript>Ni<Subscript>20</Subscript>Mn<Subscript>35</Subscript>Al<Subscript>15</Subscript>

The microstructure of the eutectic alloy Fe₃₀Ni₂₀Mn₃₅Al₁₅ (in at.%) was modified by cooling at different rates from 1623 K, i.e., above the eutectic temperature. The lamellar spacing decreased with increasing cooling rate, and in water-quenched specimens lamellae widths of ~100 nm were obtained. The orientation relationship between the fcc and B2 lamellae was found to be sensitive to the cooling rate. In a drop-cast alloy the Kurdjumov–Sachs orientation relationship dominated, whereas the orientation relationship in an arc-melted alloy with a faster cooling rate was \textfcc( [`1]12 )//\textB2( 0 1 1 );  \textfcc[ 1[`1]1 ]//\textB2 [ 1[`1]1 ]  \textand \textfcc( 0[`1]1 )//\textB2( 00 1 );\text fcc[ 0 1 1 ]//\textB2[ [`1][`1]0 ] {\text{fcc}}\left( {\bar{1}12} \right)//{\text{B2}}\left( {0 1 1} \right);\;{\text{fcc}}\left[ {1\bar{1}1} \right]//{\text{B2 }}\left[ {1\bar{1}1} \right] \,{\text{and}}\,{\text{fcc}}\left( {0\bar{1}1} \right)//{\text{B2}}\left( {00 1} \right);{\text{ fcc}}\left[ {0 1 1} \right]//{\text{B2}}\left[ {\bar{1}\bar{1}0} \right] . The hardness increased with microstructural refinement, obeying a Hall–Petch-type relationship. The strength of the alloy decreased significantly above 600 K due to softening of the B2 phase.