Shape-controlled silver metal of nanospheroids from a polymer-assisted autocombustion reaction in open air

Nanospheroids of silver, D = 18–27 nm diameters, have been synthesized following an autocombustion reaction of a polymer complex of polyvinyl alcohol (PVA) containing Ag⁺ → Ag species in open air. It is shown that, when heating with Ag⁺ species in water, PVA molecules induce a local Ag⁺ → Ag reaction, forming such a complex of Ag-nanoparticles dispersing in situ in the PVA molecules. A viscous sample (hot) could be cast and dried in 3–5 wt.% Ag-PVA films (50–100 μm thickness) at room temperature. Ag metal of nanospheroids occurs upon heating 5–10 mm pieces of the films over 300–500 °C in air. According to the X-ray diffraction, it has an Fm3m cubic crystal structure. After 300 °C, the sample consists of small crystallites (D = 24 nm), with the lattice parameter a = 0.4071 nm (density ρ = 10.618 g/cm³), which relaxed nonlinearly to a value 0.4085 nm (ρ = 10.509 g/cm³) upon D-value growing to be as large as 27 nm over higher temperatures.     

Microstructure and room temperature properties of a high-entropy TaNbHfZrTi alloy

A new refractory alloy, Ta₂₀Nb₂₀Hf₂₀Zr₂₀Ti₂₀, produced by vacuum arc-melting followed by hot isostatic pressing (HIPing) at T = 1473 K and P = 207 MPa for 3 h has predominantly a single-phase body-centered cubic (BCC) structure with the lattice parameter a = 340.4 pm. The alloy density and Vickers microhardness are ρ = 9.94 g/cm³ and H_v = 3826 MPa. The alloy has high compression yield strength (σ_0.2 = 929 MPa) and ductility (? > 50%). The alloy shows considerable strain hardening and homogeneous deformation. A simple model of solid-solution strengthening is proposed to explain the behavior.     

CuIn1−xAlxS2 thin films prepared by sulfurization of metallic precursors

CuIn_1−xAl_xS₂ thin films (x = 0, 0.09, 0.27, 0.46, 0.64, 0.82 and 1) with thicknesses of approximately 1 μm were formed by the sulfurization of DC sputtered Cu-In-Al precursors. All samples were sulfurized in a graphite container for 90 min at 650 °C in a 150 kPa Ar + S atmosphere. Final films were studied via X-ray diffraction (XRD), scanning electron microscopy (SEM) and micro-Raman spectroscopy. It was found that all samples were polycrystalline in nature and their lattice parameters varied slightly nonlinearly from {a = 5.49 Å, c = 11.02 Å} for CuInS₂ to {a = 5.30 Å, c = 10.36 Å} for CuAlS₂. No unwanted phases such as Cu_2−xS or others were observed. Raman were recorded at a room temperature and the most intensive and dominant A₁ phonon frequency varied nonlinearly from 294 cm⁻¹ (CuInS₂) to 314 cm⁻¹ (CuAlS₂).     

Study of post annealing influence on structural, chemical and electrical properties of ZTO thin films

Zinc-Tin-Oxide (ZTO) thin films were deposited on glass substrate with varying concentrations (ZnO:SnO₂; 100:0, 90:10, 70:30 and 50:50 wt.%) at room temperature by flash evaporation technique. These deposited ZTO films were annealed at 450 °C in vacuum. These films were characterized to study the effect of annealing and addition of SnO₂ concentration on the structural, chemical and electrical properties. The XRD analysis indicates that crystallization of the ZTO films strongly depends on the concentration of SnO₂ and post annealing where annealed films showed polycrystalline nature. Atomic force microscopy (AFM) images manifest the surface morphology of these ZTO thin films. The XPS core level spectra of Zn(2p), O(1s) and Sn(3d) have been deconvoluted into their Gaussian component to evaluate the chemical changes, while valence band spectra reveal the electronic structures of these films. A small shift in Zn(2p) and Sn(3d) core level towards higher binding energy and O(1s) core level towards lower binding energy have been observed. The minimum electrical resistivity (ρ ≈ 3.69 × 10⁻² Ω-cm), maximum carrier concentration (n ≈ 3.26 × 10¹⁹ cm⁻³) and Hall mobility (μ ≈ 5.2 cm² v⁻¹ s⁻¹) were obtained for as-prepared ZTO (50:50) film thereafter move towards lowest resistivity (ρ ≈ 1.12 × 10⁻³ Ω-cm), highest carrier concentration (n ≈ 2.96 × 10²⁰ cm⁻³) and mobility (μ ≈ 18.8 cm² v⁻¹ s⁻¹) for annealed ZTO (50:50) thin film.     

Synthesis of the pyrrolo[3,2-b]pyrrole-based copolymer with enhanced open circuit voltage

A new accepter unit, pyrrolo[3,2-b]pyrrole-2,5-dione, was prepared and utilized for the synthesis of the conjugated polymer containing electron donor–acceptor pair for OPVs. Pyrrolo[3,2-b]pyrrole-2,5-dione unit, regioisomer of the known pyrrolo[3,4-c]pyrrole-1,4-dione, is originated from the structure of stable synthetic pigment. The new conjugated polymer with pyrrolo[3,2-b]pyrrole-2,5-dione, thiophene and carbazole was synthesized using Suzuki polymerization to generate P1. The solid thin film of P1 shows absorption band with maximum peaks at 374 and 548 nm, and the absorption onset at 679 nm, corresponding to band gap of 1.83 eV. The field-effect hole mobility of P1 is 2.2 × 10⁻⁵ cm²/Vs. The device based on the polymer:PCBM (1:2) blend without thermal treatment showed a V_OC of 0.82 V, a J_SC of 6.28 mA/cm², and an FF of 0.39, giving a PCE of 2.00%.     

New complex intermetallic in the Al-Rh-Ru alloy system

A ternary orthorhombic phase (Pbma, a = 2.34, b = 1.62 and c = 2.00 nm) was revealed around the Al₇₇Rh₁₅Ru₈ composition. It is structurally related to the Al-Rh and Al-Pd ?-phases.     

Morphology and structure of highly crystalline polyaniline films

The morphology of polyaniline films grown by self-organization on a silicon substrate, modified previously with a self-assembled monolayer, has been investigated by conductive AFM, which showed conducting crystalline domains corresponding to the well-faceted crystallites scattered over the films. The film morphology studied by conductive AFM revealed the higher conductivity crystalline domains of the film. We also use transmission electron microscopy in bright-field and dark-field imaging modes, as well as selected area electron diffraction (SAED) to study the single crystal and polycrystalline regions of the films. SAED of single crystals showed diffraction pattern with well-defined spots. Rectangular symmetry is observed for the first time for PANI single crystals. The film regions with polycrystalline domains showed diffraction pattern with sharp rings. The indexing was carried out based on the orthorhombic structure and the unit cell parameters obtained are a = 4.2 Å, b = 5.9 Å and c = 9.8 Å. The nanocrystallite size distribution obtained from C-AFM is in the range of 10–60 nm and corroborates well with the TEM data.     

Adhesion improvement of poly (vinyl alcohol) coating on silicon substrate

The adhesion of the biocompatible hydrophilic polymer, poly (vinyl alcohol) to a model substrate, silicon, was investigated. Contact angle measurements were used to reveal the effect of various substrate cleaning procedures including sonication and UV-ozone treatment prior to casting a 35 μm coating. Raman microspectrometry and X-ray reflectometry were used to characterise the composition and the thickness of PVA thin films. The use of mechanical abrasion of the substrate followed by a 131 nm primer layer of PVA in combination with vacuum treatment at temperatures higher than the glass transition temperature (T_g = 80 °C) provided the best resistance to delamination as demonstrated by visual observation during prolonged immersion of the coatings in water.     

Electrical properties of sub-100 nm Cu films deposited by electroless plating on amino-terminated silicon oxide activated with Au nano-particles

Self-assembled organic monolayers (SAMs) are good coupling agents and diffusion barriers at Cu/SiO₂ and Cu/low-k interfaces and are considered therefore as important elements of future all-wet ULSI metallization with sub-45 nm Cu deposited by electroless plating (ELD). We formed SAM of 3-aminopropyltrimethoxy silane (APTMS) onto SiO₂/Si substrate, activated the surface of APTMS with 5, 8, 15 and 25 nm Au nano-particles (AuNPs), deposited (30-100) nm films of Cu by ELD and measured electrical resistivity ρ of the films in the as-deposited state and after vacuum annealing at 220 C. The size of AuNPs was found to be a key factor in getting low resistance sub-100 nm Cu films by ELD. The resistivity ρ ≈ 4 ± 0.8 μΩ·cm - considerably smaller compared to the previously reported data - was achieved with the use of 5 nm AuNPs. XPS and AFM revealed nano-pores, which can contribute to ρ but do not compromise likely the diffusion barrier properties of the SAM.     

Effect of deposition temperature on structural, surface, optical and magnetic properties of pulsed laser deposited Al-doped CdO thin films

The objective of this work is to study the influence of deposition temperature on structural, surface, optical and magnetic properties of the Al doped CdO thin films prepared by pulsed laser deposition (PLD) technique. KrF excimer laser (λ = 248 nm, τ_l = 20 ns, ν = 10 Hz, ?_l = 2.5 J/cm²) was employed for the deposition of thin films. It is observed by XRD results that films grown at room temperature and 100 °C show preferential growth along (1 1 1) and (2 0 0) directions while high temperatures (200-400 °C) lead to preferential growth along the (2 0 0) direction only. The optical constants (n, k, α, and optical band gap energy) of films measured by spectroscopic ellipsometry show strong dependence upon deposition temperature. M-H loop of films, measured by vibrating sample magnetometer, deposited at 25 °C and 100 °C show paramagnetic nature while films deposited at temperatures (200-400 °C) exhibit ferromagnetic character. Scanning electron micrographs show degraded elongated grains at lower deposition temperatures, while smooth and compact surface is observed for films deposited at higher deposition temperatures.     

Fabrication of GdBa2Cu3O7−x films by TFA-MOD process

GdBa₂Cu₃O_7−x (GdBCO) films have been deposited on LaAlO₃ (LAO) (0 0 l) single crystal substrates by trifluoroacetate metal organic deposition (TFA-MOD) method. The effects of oxygen partial pressure and firing temperature on microstructure and critical properties of GdBCO films were discussed. The phase formation, texture and microstructure of films were characterized by X-ray diffraction and scanning electron microscopy. The oxygen partial pressure was considered to play a great role for formation of impurity phase and a-axis oriented grains. The degree of c-axis orientation was also influenced by the firing temperature. The highly c-axis oriented GdBCO film obtained at 815 °C under an oxygen partial pressure of 100 ppm has a high performance critical current density J_c (77 K, self field) = 1.8 MA/cm².     

Passivation oxide film on Nd-Fe-B permanent magnets in borate buffer solution by ellipsometry

The passivation of Nd-Fe-B permanent magnet was investigated in neutral borate solution at pH 8.4. The thickness of the passive oxide film on the magnets was measured by ellipsometry and the composition was estimated by glow discharge optical emission spectroscopy (GD-OES).The passivation of the magnets takes place in the potential range between −0.2 and 1.0 V vs. Ag/AgCl/Sat. KCl. In the potential range, current density decays to the lower than 10⁻⁶ A cm⁻² after potentiostatic oxidation for 1800 s. The passive oxide film growth is assumed to be optically simulated from a model with a homogeneous film with complex refractive index, N = 2.1 − j0.086. The thickness estimated from the refractive index linearly increases with potential from 3.6 nm at −0.2 V to 7.8 nm at 1.0 V. The passive film growth follows the ionic migration model under high electric field, i.e., the Cabrera-Mott growth model. The ionic conductivity estimated from the model is about κ = 1.7 × 10⁻¹⁶ Ω⁻¹ cm⁻¹. The passive oxide film is preferentially composed of iron oxide/hydroxide. Boron and neodymium are, respectively, concentrated at the surface of the oxide film and at the inner layer in the oxide film.     

Polymer light-emitting diode using a new trialkoxyalkyl substituted PPV derivative

A new light-emitting poly(p-phenylenevinylene) (PPV) derivative containing trialkoxyalkyl substituents (TAA) as color tunable groups was synthesized through a Gilch polymerization, and the light-emitting properties of the polymer (TAA-PPV) were investigated. The emission of TAA-PPV was found to be highly blue-shifted to the green region, with peak absorption and band edge near 399 and 490 nm, respectively. The PL emission maximum of TAA-PPV thin films was found to be at approximately 493 nm. Light-emitting devices were fabricated with the configuration ITO (indium–tin oxide)/PEDOT/polymer/Ca/Al and produced very bright green emission. This device with TAA-PPV as the emissive layer had a maximum brightness of 3600 cd/m² and a maximum power efficiency of 0.77 lm/W.     

Effect of Ag nanoparticle size on the plasmonic photocatalytic properties of TiO2 thin films

Photocatalytic TiO₂ films combined with Ag nanoparticles (NPs) embedded-SiO₂ films were fabricated by means of a RF magnetron sputtering and subsequent rapid thermal annealing (RTA). X-ray diffraction results show that the TiO₂ films have anatase phase when annealed at 500 °C. The Ag NPs were formed by deposition and subsequent annealing at 600 °C. Scanning electron microscopy (SEM) results show that the density of the NPs decreases with increasing Ag film thickness. For example, the average NP diameter varies from ~ 19.3 to ~ 55.9 nm as the film thickness increases from 2 to 12 nm. Transmittance measurements show that as the Ag NP size decreases, the plasmonic peaks shift towards the shorter-wavelength region and become narrower. It is further shown that under UV-illumination (352 nm), all the TiO₂ films with the Ag NPs show higher methylene blue decomposition rates compared to the TiO₂ only films and the TiO₂ films with Ag NP (a 7 nm-thick Ag film) show the best decomposition rate among the samples possibly due to the combined effects of optimized localized field amplification and radiative efficiency.     

Effective segregation during Czochralski growth and spectral properties of Nd in GSAG crystal

GSAG and Nd:GSAG crystals were grown by standard Czochralski technique. The refractive index of GSAG in the wavelength range 500-3000 nm, effective segregation coefficient and absorption cross sections of Nd³⁺ in GSAG were determined by optical absorption method. The effective segregation coefficient was calculated to be 0.525. The spectroscopic and laser properties of Nd:GSAG crystal were studied by Judd-Ofelt analysis. The Judd-Ofelt parameters were calculated to be Ω₂ = 1.32 × 10⁻²¹ cm², Ω₄ = 2.93 × 10⁻²⁰ cm² and Ω₆ = 3.91 × 10⁻²⁰ cm². With these intensity parameters, the values of absorption and emission oscillator strengths, transition probabilities, fluorescence ratios and radiative lifetimes were obtained. The large fluorescence ratio of |[4F]3/2〉 is very favorable for laser operation at 942 nm. These results confirm that Nd:GSAG is a suitable laser material for water vapor detection by DIAL.     

Effects of oxygen partial pressure on film growth and electrical properties of undoped ZnO films with thickness below 100 nm

The dependences of electrical and structural properties on film thickness below 100 nm have been studied on polycrystalline undoped zinc oxide (ZnO) thin films on glass substrates at 200 °C prepared by plasma-assisted electron-beam deposition. From Hall effect measurements, we find that resistivity decreases from 0.47 to 0.02 Ω cm with increasing film thickness, whereas carrier concentration remains almost constant, 1.65-2.0 × 10¹⁹ cm^− 3, Hall mobility increases from 1.7 to 16.7 cm²/Vs with increasing film thickness. From both high-resolution out-of-plane and in-plane X-ray diffraction (XRD) data, we find substantial changes in the lattice parameters with increasing film thickness below 40 nm; a reduction in the lattice parameter of the a-axis and an increase in the lattice parameter of the c-axis. Williamson-Hall analysis reveals an increase in in-plane grain size with increasing film thickness. This indicates that the dominant scattering mechanism that determines electrical properties is a boundary scattering mechanism.     

A study of the Al-rich region of the Al-Cu-Mo alloy system

Partial isothermal sections at 810, 700 and 585 °C are presented for a high-Al compositional range of Al-Cu-Mo. The maximal solubility of Cu in the Al₅Mo phase(s) was found to be ∼3 at.%. The previously reported Al₃Ti-type phase was found to be formed around the Al_68.5Cu_6.5Mo₂₅ composition. The other ternary phase forming in a small compositional range around Al₇Cu₂Mo has a hexagonal structure with a = 0.86796(8) and c = 1.51948(12) nm.     

Bulk Mg-3Al-Zn alloy with ultrafine grain size produced by powder metallurgy

Ultrafine-grained Mg-3Al-Zn alloys with an average grain size of 180 nm have been made by powder metallurgy. First, the nanocrystalline powders with mean grain size of 45 nm were produced by ball milling under argon atmosphere, and then through vacuum hot pressing at 633 K for 40 min and warm extrusion at 373 K, bulk solid samples were compacted successfully from the mechanically milled powders, and the relative density of the samples was about 98.87% (1.8003 g/cm³). XRD, SEM and TEM analysis showed that the microstructure of the samples consists of homogeneous equiaxed grains and grain growth has taken place during the consolidation process.     

Structural and optical study of samarium doped cerium oxide thin films prepared by electron beam evaporation

Samarium doped cerium oxide films were grown on the glass substrate using e-beam deposition technique and then characterized using different techniques: X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), Raman spectroscopy and UV-visible spectroscopy measurements. XRD analysis shows that all the films have cubic structure and the crystallite size decreases from 18 to 13 nm as the samarium (Sm) concentration increases. The FE-SEM images indicate that all the films have columnar growth. UV-visible measurements reflect that the films have high transparency (>80%) in the visible region. From the Raman spectra, we have observed two peaks at 466 and 565 cm⁻¹. The peak at 466 cm⁻¹ is assigned to the F_2g mode of cerium oxide (CeO₂) whereas the peak at 565 cm⁻¹ is due to the presence of the oxygen vacancies. The increase in the intensity of the peak at 565 cm⁻¹ indicates that the oxygen vacancy increases with Sm doping.     

The effect of the microstructure and the surface topography on the electrical properties of thin Ag films deposited by high power pulsed magnetron sputtering

In this work thin silver (Ag) films are grown employing high power pulsed magnetron sputtering (HPPMS) for various pulse on/off time configurations, as well as by dc magnetron sputtering (dcMS), for reference. It is shown that the increase of the pulse off-time from 450 μs to 3450 μs, while the pulse on-time is kept constant at 50 μs, results in an increase of the peak target current (I_Tp) from 3 A to 22 A. The increase of I_Tp is accompanied by an increase of the ion flux towards the growing film. This is particularly pronounced for I_Tp > 11 A. The microstructure, the surface topography and the electrical properties of Ag films grown at I_Tp = 11 A, I_Tp = 22 A and by dcMS are investigated, as a function of the film thickness d. It is shown that for d > 20 nm the electrical resistivity of films sputtered at I_Tp = 22 A is similar to that of films grown by dcMS. Slightly higher values are measured for films grown at I_Tp = 11 A. It is found that in this thickness range the film conductivity is strongly affected by the vertical grain size and the scattering of the charged carriers at the film interfaces. For d < 15 nm the resistivity of films deposited at I_Tp = 22 A is substantially lower as compared to that of films grown by dcMS. Films deposited at I_Tp = 11 A exhibit also in this case a higher conductivity. In this thickness regime the electronic transport and, thus the conductivity are profoundly determined by the surface topography and the film density.