Effect of annealing temperature on the microstructure and photoluminescence of low resistivity Si/SiN/TaN thin films using magnetron sputtering

A lot of studies have been devoted to the porous Si, erbium-doped Si and Si-embedded in dielectric matrix of SiO or SiN together with long-time conventional furnace annealing. Besides, it is noted that these Si nanostructured films were highly resistive and non-conducting. In this paper, we have investigated the effect of annealing temperature on the microstructure and photoluminescence of low-resistivity Si/SiN/TaN nanocomposite thin films which are deposited by magnetron sputtering and followed by rapid thermal annealing (RTA). All samples are of luminescence and staying low resistivity at about 1462–2162 μΩ cm which increases with increasing annealing temperatures. The asymmetric broad photoluminescence (PL) peak covered the wavelengths of 400–700 nm. The wide visible PL spectra can be deconvoluted into three bands of blue (~ 455 nm), green-yellow (~ 525 nm), and orange emissions (~ 665 nm), which correspond to the emission origins from unsatisfied states in imperfections of interface between the Si:O and SiN:O, located states related to the mixed SiO or SiN bonds in SiN:O layer and nc-Si embedded in SiN:O matrix. The detailed mechanism of broad visible PL was investigated in terms of microstructure and bonding configuration evolution. The relationship between the annealing temperature, microstructure and PL behavior of Si/SiN/TaN multilayer films is discussed and established.     

Metakaolin-based inorganic polymer composite: Effects of fine aggregate composition and structure on porosity evolution,microstructure and mechanical properties

This paper examines the phase transformation, pore evolution, microstructural and mechanical changes that occur in inorganic polymer cement (IPC) in the presence of three different grade of fine aggregates (ф < 100 μm) of ladle slag, nepheline syenite and quartz sand. Experimental results indicate that polycondensation was enhanced in nepheline syenite based specimens, compared to quartz sand, due to the increase in HMAS phases in relation to the dissolution and interaction of amorphous/disordered fraction of aggregates. HCS and HCAS with HMAS phases were identified in the ladle slag based specimens. The formation of these new phases reduced both the cumulative pore volume and pores size. The apparent increase in volume of capillary pores in ladle slag based specimens was explained by the residual bubbles from the carbonates included in raw slag. The flexural strength of the inorganic polymer cement increases from 4 MPa to 4.2, 4.8 and 6.8 MPa with the addition of 20 wt% of quartz sand, nepheline syenite and ladle slag respectively. These values increase significantly between 28 and 180 days of curing (9.1 MPa for ladle slag and 10.0 MPa for nepheline syenite). It was concluded that fines can be used to remove the HM and poorly bounded alumina oligomers in metakaolin based inorganic polymer matrices and improve the interfacial zone for the design of an optimum grade and high-performance composites.     

Phase constitutions of MoSiN anti-oxidation multi-layer coatings on CC composites by fused slurry

To improve the oxidation resistance of MoSi fused slurry coating fabricated in vacuum, MoSiN multi-layer coatings were synthesized on C/C composites in nitrogen atmosphere by fused slurry using same Mo and Si element powders. The phase compositions and microstructures were characterized by X-ray diffractometry (XRD), optical microscopy (OM), scanning electron microscopy (SEM) with energy-dispersive spectroscopy (EDS). The results indicate that the MoSiN coating contains SiC inner layer and MoSi₂/Si main layer, which was similar with MoSi coating. Additionally, a thin outer layer with nano-filiform morphology has been found on the coating surface, which consists of SiC, Si₃N₄, AlN, Al₂O₃ and sialon phase. Oxidation experiments show that the MoSiN multi-layer coating exhibits excellent oxidation resistance at 1400 °C and anti-oxidizing potential ability at 1450 °C.     

Synthesis,crystal structure,luminescent properties and photo degradation of mer-tris(8-Hydroxy-quinolinato-N,O)-indium(iii) hydrate 0.5 methanol solvate

Tris-(8-hydroxyquinioline) aluminium (Alq₃) is widely used in organic light emitting diodes as an emission and electron transport layer. In this study the effect of solvent molecules, in the solid state crystal lattice, on the photoluminescence properties of synthesized mer-tris(8-Hydroxy-quinolinato-N, O)-indium(iii) hydrate 0.5 methanol solvate (mer-[In(qn)₃]⋅H₂O⋅0.5 CH₃OH) was studied. Single crystals were obtained through a recrystallization process and single crystal X-ray diffraction was performed to obtain the unit cell structure. The main absorption peaks were assigned to ligand centered electronic transitions, while the solid state photoluminescence excitation peak at 440 nm was assigned to the 0–0 vibronic state of In(qn)₃. Broad emission at 510 nm was observed and was ascribed to the relaxation of an excited electron from the S₁–S₀ level. A powder sample was annealed at 130 °C for 2 h. A decrease in intensity was observed and could possibly be assigned to a loss of solvent species. To study the photon degradation, the sample was irradiated with an UV lamp for ∼15 h. The emission data was collected and the change in photoluminescence intensity with time was monitored. High resolution X-ray photoelectron spectroscopy (XPS) scans of the O-1s peak revealed that after annealing the binding energy shifted to lower energies indicating a possible loss of the H₂O and CH₃OH present in the crystal. The O-1s peak of the degraded sample indicated the possible formation of CO (∼532.5 eV), COH and OCOH (∼530.5 eV) on the phenoxide ring.     

Fibroblast functionality on novel Ti30Ta nanotube array

In this study, the mechanical substrate and topographical surface properties of anodized Ti30Ta alloy were investigated using scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS) and contact angle measurement. The anodization process was performed in an electrolyte solution containing HF (48%) and H₂SO₄ (98%) in the volumetric ratios 1:9 with the addition of 5% dimethyl sulfoxide (DMSO) at 15 V, 25 V and 35 V for 20 and 40 min, producing a nanotube architecture when anodized at 35 V for 40 min. Human dermal fibroblasts (HDF, neonatal) were utilized to evaluate the biocompatibility of Ti30Ta nanotubes and Ti30Ta alloy after 1 and 3 days of culture. Cellular adhesion, proliferation, viability, cytoskeletal organization and morphology were investigated using fluorescence microscope imaging, biochemical assay and SEM imaging respectively. The results presented identify altered material properties and improved cellular interaction on Ti30Ta nanotubes as compared to Ti30 Ta alloy.     

Nanoparticles of the giant dielectric material,calcium copper titanate from a sol–gel technique

The precursor of CaCu₃Ti₄O₁₂ (CCTO) nano particles have been successfully synthesized by sol–gel method at 90 °C. The dried precursor powder was milled and then calcined at 450 °C, 550 °C, 650 °C, 800 °C, 850 °C and 950 °C for 3 h. The phase formation of CCTO was analyzed by step by step using FTIR and XRD. Particle size and shape were evaluated by AFM. The XRD results of the powder calcined at 800 °C indicated the formation of CCTO phase. AFM studies showed that average particle size of the CCTO powder range 90–120 nm. The absorption bands corresponding to vibrations of CaO, CuO and TiOTi were observed at 606, 525 and 463 cm^? 1 using FTIR. The samples sintered at 1040 °C showed the densities as high as 96% of theoretical density. The grain sizes of sintered pellets were determined by FE-SEM. The dielectric properties of prepared samples were studied by LCR meter.     

Effect of water content in sol on optical properties of hybrid sol–gel derived TiO2/SiO2/ormosil film

Sol–gel derived TiO₂/SiO₂/ormosil hybrid planar waveguides have been deposited on soda-lime glass slides and silicon substrates, films were heat treated at 150 °C for 2 h or dried at room temperature. Different amounts of water were added to sols to study their impacts on microstructures and optical properties of films. The samples were characterized by m-line spectroscopy, Fourier transform infrared spectroscopy (FT-IR), UV/VIS/NIR spectrophotometer (UV–vis), atomic force microscopy (AFM), thermal analysis instrument and scattering-detection method. The refractive index was found to have the largest value at the molar ratio H₂O/OR = 1 in sol (OR means OCH₃, OC₂H₅ and OC₄H₉ in the sol), whereas the thickest film appears at H₂O/OR = 1/2. The rms surface roughness of all the films is lower than 1.1 nm, and increases with the increase of water content in sol. Higher water content leads to higher attenuation of film.     

Surface aspects of discolouration in Bisphenol A Polycarbonate (BPA-PC), used as lens in LED-based products

The surface-related reactions during discolouration of Bisphenol A Polycarbonate (BPA-PC), used as LED lens plates, under thermal stress are studied. X-ray photoelectron spectroscopy (XPS) has been used to monitor the changes in the surface chemistry of BPA-PC plates over a temperature range of 100–140 °C for a period up to 3000 h. Increasing time under thermal stress is associated with the discolouration, and increase in the yellowing index (YI) of PC plastic lens. The XPS results show that discolouration is associated with oxidation at the surface, finding a significant increase in the signal ratio O_1s/C_1s in the XPS spectra of degraded specimens. During thermal ageing, the CH concentration decreases and new oxide features CO and OCO form, with the latter being a support for oxidation at the surface being a major reaction during discolouration. Results also show that irradiation with blue light during thermal ageing accelerates the kinetics of discolouration and the increased O_1s/C_1s ratio in XPS spectra.     

Luminescence at 1.53 μm for a new Er3+-doped transparent oxyfluoride glass ceramic

Transparent 45SiO₂25Al₂O₃5CaO10NaF15CaF₂ glass ceramics doped with different levels of Er³⁺ were prepared. The spherical CaF₂ nanocrystals with 10–20 nm in size were verified to be homogeneously embedded among the glassy matrix. Room temperature absorption and emission spectra corresponding to ⁴I_13/2 ↔ ⁴I_15/2 transitions of Er³⁺ ions in precursor glasses and glass ceramics, respectively had been measured. For glass ceramics, with increasing of Er³⁺ content from 0.1 to 2.0 mol%, the FWHM values of the emission bands increased from 42 to 71 nm; meanwhile, the lifetime of ⁴I_13/2 level slightly reduced. However, both the values of FWHM and lifetime were larger than those of precursor glasses due to the change of ligand field of Er³⁺ ions.     

Optical properties of TiO2 and disperse red-19 composite

Characteristic absorption and photoluminescence (PL) of TiO₂ and disperse red-19 (DR-19) composite have been investigated. Two step synthetic processes were employed to incorporate the DR-19 to the TiO₂ sol–gel. Firstly, urethane bonds between the DR-19 (OH) and 3-isocyanatopropyl triethoxysilane (ICPTES, NCO) were fabricated (ICPDR) prior incorporation to the TiO₂ sol–gel. Secondary, hydrolysis of the ethoxy group from the ICPDR and condensation reaction between silanol groups from ICPDR and TiO₂ sol–gel were performed by adding ICPDR to the TiO₂ sol–gel and aged for several days at room temperature (ICPDRTiO₂). There was no absorption peak shift with increasing the DR-19 concentration in methanol. However, UV–visible absorption band was shifted toward red approximately 0.09 eV for the ICPDRTiO₂ film, which indicated the formation of dimmer or more aggregates. The PL peaks of ICPDRTiO₂ were red-shifted compared with DR-19 in methanol (0.12 eV) and ICPDR film (0.09 eV). The relatively large emission peak shift toward red could be due to the fluorescence resonance energy transfer (FRET) between DR-19 and TiO₂ in ICPDRTiO₂ matrix.     

Poly (hydroxyethyl methacrylate-glycidyl methacrylate) films modified with different functional groups: In vitro interactions with platelets and rat stem cells

Copolymerization of 2-hydroxyethylmethacrylate (HEMA) with glycidylmethacrylate (GMA) in the presence of α-α′-azoisobisbutyronitrile (AIBN) resulted in the formation of hydrogel films carrying reactive epoxy groups. Thirteen kinds of different molecules with pendant NH₂ group were used for modifications of the p(HEMA-GMA) films. The NH₂ group served as anchor binding site for immobilization of functional groups on the hydrogel film via direct epoxy ring opening reaction. The modified hydrogel films were characterized by FTIR, and contact angle studies. In addition, mechanical properties of the hydrogel films were studied, and modified hydrogel films showed improved mechanical properties compared with the non-modified film, but they are less elastic than the non-modified film. The biological activities of these films such as platelet adhesion, red blood cells hemolysis, and swelling behavior were studied. The effect of modified hydrogel films, including NH₂, (using different aliphatic CH₂ chain lengths) CH₃, SO₃H, aromatic groups with substituted OH and COOH groups, and amino acids were also investigated on the adhesion, morphology and survival of rat mesenchymal stem cells (MSCs). The MTT colorimetric assay reveals that the p(HEMA-GMA)-GA-AB, p(HEMA-GMA)-GA-Phe, p(HEMA-GMA)-GA-Trp, p(HEMA-GMA)-GA-Glu formulations have an excellent biocompatibility to promote the cell adhesion and growth. We anticipate that the fabricated p(HEMA-GMA) based hydrogel films with controllable surface chemistry and good stable swelling ratio may find extensive applications in future development of tissue engineering scaffold materials, and in various biotechnological areas.     

Green synthesis of Au–Pd bimetallic nanoparticles: Single-step bioreduction method with plant extract

A facile and eco-friendly method for the preparation of Au–Pd bimetallic nanoparticles (~ 7 nm) has been developed based on simultaneous bioreduction of Au(III) and Pd(II) precursors with Cacumen Platycladi leaf extract in aqueous environment. The morphology, structure, and size were confirmed with the aid of transmission electron microscopy, selected area electron diffraction, UV–vis spectroscopy, X-ray diffraction, and energy dispersive X-ray spectroscopy. The results from Fourier transform infrared spectroscopy showed that the CO and CO groups in the plant extract played a critical role in capping the nanoparticles. Importantly, the process can be described as pure “green chemistry” technique since no additional synthetic reagents are used as reductants or stabilizers.     

Surface modification on polyethylene terephthalate films with 2-methacryloyloxyethyl phosphorylcholine

In this study, the surface of polyethylene terephthalate (PET) was modified to improve the protein and cell adhesion behavior with low temperature ammonia plasma treatment followed by 2-methacryloyloxyethyl phosphorylcholine (MPC) grafting. The x-ray photoelectron spectroscopy (XPS) results showed that the COO^?, NCO and POH groups were successfully incorporated onto the sample surface after MPC grafting. Furthermore, formation of new bonds, N and NH on the sample surface grafted with MPC was recorded by Fourier transform infrared spectroscopy (FTIR). A large number of spherical particles at submicron to nanometer scale were also observed on the surface by atomic force microscopy (AFM). The cell adhesion experiments on PET film surfaces were evaluated and the highly hydrophilic surfaces could not promote cell adhesion and spreading. All results achieved in this study have clearly indicated that the method combining low temperature ammonia plasma treatment and MPC grafting is an effective way of producing a suitably hydrophilic PET surface with the capability of weakening the protein adsorption greatly.     

Room temperature solid–solid reaction preparation of ironboron alloy nanoparticles and Mössbauer spectra

The amorphous ironboron alloy can be prepared very easily by a room temperature solid–solid reaction of the FeCl₃·6H₂O, CrCl₃·6H₂O and KBH₄ powders. The characterizations show that the product is mainly composed of amorphous ironboron alloy nanoparticles. ⁵⁷Fe Mossbauer spectra at 84 and 295 K show that there are three kinds of Fe-containing components in the sample. There are the superparamagnetic relaxation in Mössbauer spectra and the continuous distribution of internal magnetic field in the ironboron alloy.     

Synergistic effects of oxidized CNTs and reactive oligomer on the fracture toughness and mechanical properties of epoxy

The soft modifiers added to improve the fracture toughness of epoxies generally deteriorate their mechanical properties. Hence, oxidized multi-walled carbon nanotubes (O-CNTs) were added to the epoxy modified with reactive oligomer. The NCO terminated reactive oligomer acts as a cross-linker between the O-CNTs and the OH groups of the epoxies. The impact strengths of the 15 wt.% oligomer modified epoxy containing 0.5 wt.% of O-CNTs at room temperature (RT) and cryogenic temperature (CT) are enhanced by 23.6% and 69.5% compared to that of the unmodified epoxy. In addition to increasing fracture toughness, the tensile strength (TS) of the modified epoxy/O-CNTs at CT is found to be 91.7 MPa, which is comparable to that of the unmodified epoxy (92.1 MPa). Hence, the attachment of O-CNTs to the reactive oligomer modified epoxy can be an efficient approach to toughen epoxy resins without compromising their tensile properties.     

High contrast glasses for all-solid fibers fabrication

We present composition development of borosilicate glasses for fabrication of high refractive index contrast, all-solid photonic crystal fibers. An oxide system composed of SiO₂B₂O₃Al₂O₃Li₂ONa₂OK₂O was adjusted to match thermal properties of selected highly nonlinear, lead bismuth gallium silicate glass. A high difference of refractive index of 0.376 is achieved at a wavelength of 1550 nm. We proved experimentally that the developed pair of glasses enables to draw optical fibers, and we propose a design of a photonic crystal fiber structure for broadband supercontinuum generation.     

Investigation on the film-coating mechanism of alumina-coated rutile TiO2 and its dispersion stability

The alumina and alumina-coated rutile TiO₂ samples were synthesized by the chemical liquid deposition method under various pH values and aging temperature. The prepared samples were characterized by X-ray diffraction (XRD), Transmission electron microscopy (TEM), ζ-potential as well as X-ray photoelectron spectroscopy (XPS). The relationship between pH values, the dispersion stability, crystalline types and microstructure of alumina-coated rutile TiO₂ samples were studied. It is indicated that the coating film exhibited amorphous hydrous alumina (at pH 3–7), boehmite (at pH 7–9) and bayerite (pH > 11), respectively. And the higher aging temperature was in favor of the elevation of boehmite content of coating film. As the boehmite content increased, the dispersion stability was gradually enhanced and the prepared sample exhibited optimum dispersion stability at pH 9 and aging temperature 200 °C, respectively. The increase of steric hindrance and electrostatic repulsion led to the promotion of dispersion stability via coating hydrous alumina film on the surface of rutile TiO₂. The detection of AlO and the significantly enhancement of AlOTi intensity confirmed that the film coating process should be main attributed to both chemical bonding and physical adsorption.     

The effects of the SiOSi segment presence in BAPP/BPDA polyimide system on morphology and hardness properties for opto-electronic application

Recent technological advances demanded incorporation of SiOSi segment into polyimides (PI)s to improve versatility in terms of processing, morphology and optoelectronic properties. In order to study the role of SiOSi segment in the morphology and hardness properties of PI, the SiOSi segment have been introduced into the PI backbone through the conventional copolymerization and in PI matrix through sol gel method. The PI series were characterized by Fourier transform infra-red (FT-IR), nuclear magnetic resonance (NMR) spectroscopy, elemental analysis, solution viscosity and gel permeation chromatography (GPC). Scanning electron microscope (SEM) analysis suggested a microphase separation between the two components. FT-IR spectra confirmed the presence of silicone segment, as well as a complete imidization of PI series. Micrograph suggested a homogeneous phase between the PI and silicone segment for copolymerization series while sol gel technique revealed the inorganic particles were distributed homogenously in PI matrix. It was also found that the presence SiOSi segment in PI backbone and PI matrix influenced the opto-electronic properties.     

Degradation performance of biodegradable FeMnC(Pd) alloys

Biodegradable metals offer great potential in circumventing the long-term risks and side effects of medical implants. Austenitic FeMnCPd alloys feature a well-balanced combination of high strength and considerable ductility which make them attractive for use as degradable implant material. The focus of this study is the evaluation of the degradation performance of these alloys by means of immersion testing and electrochemical impedance spectroscopy in simulated body fluid. The FeMnCPd alloys are characterized by an increased degradation rate compared to pure Fe, as revealed by both techniques. Electrochemical measurements turned out to be a sensitive tool for investigating the degradation behavior. They not only show that the polarization resistance is a measure of corrosion tendency, but also provide information on the evolution of the degradation product layers. The mass loss data from immersion tests indicate a decreasing degradation rate for longer times due to the formation of degradation products on the sample surfaces. The results are discussed in detail in terms of the degradation mechanism of Fe-based alloys in physiological media.     

NiB deposits on p-silicon using borohydride as a reducing agent

A solution, with various deposition parameters optimized to deposit electroless NiB films on p-silicon, has been developed, using sodium borohydride as the reducing agent. This has been done with a view to replace the existing silver–aluminum back contact for crystalline silicon solar cells with NiB films. The deposition has been studied by varying the temperature, time of deposition and the concentration of the reducing agent used, keeping the pH of the solution unchanged. Sheet resistance of the deposited films were measured to confirm the growth. Preliminary studies on contact resistance between NiB film and p-Si have been carried out.