Papers by Keyword: Transmission Electron Microscopy (TEM)

Abstract: CuO/TiO₂ nanocomposites were synthesized using an economical drop-casting method and subsequently irradiated with high-energy C⁺ ions at fluence levels of 1 × 10¹⁴, 1 × 10¹⁵, 1 × 10¹⁶, and 1 × 10¹⁷ ions cm⁻². While ion irradiation of metal oxide materials is well established, the systematic investigation of C⁺ ion effects on the structural and optical properties of CuO/TiO₂ nanocomposites under these specific fluence conditions has been limited. This study therefore contributes new insight into how controlled C⁺ irradiation can tailor the behavior of this composite. These un-irradiated and irradiated nanocomposites were characterized using various techniques such as Energy Dispersive X-Ray Spectroscopy (EDX), Raman Spectroscopy, Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Photoluminescence (PL) Spectroscopy and Diffuse Reflectance Spectroscopy (DRS) to analyze structural, morphological and optical properties of these nanocomposites. The Raman and EDX analysis confirmed the formation of pure CuO/TiO₂ nanocomposites. The SEM results represent the spherical morphology of these nanocomposites in aggregated form. PL spectra’s depicted the pure and C⁺ ions irradiated nanocomposites were the same before and after C⁺ irradiation in the Photoluminescence emission. DRS results indicated that band gap energy was decreased as the fluence rate of C⁺ ions increased up to 1 × 10¹⁷ ions cm^-2.

Abstract: M₆C carbides were found to form during short-term creep tests at 600 °C for 1100 h in an 11Cr ferritic/martensitic (F/M) steel with the normalized and tempered condition. The M₆C carbides have a face-centered cubic crystal structure, and a metallic element composition of 41-45Fe, 30-33W, 19-21Cr, 3Co/5Ta in atomic pct. The M₆C carbides were a dominant phase in the crept steel. δ-ferrite in high-Cr F/M steels may lead to a premature formation of large-sized M₆X precipitates during high temperature creep.

Abstract: Ternary (Si_1-xC_y)Ge_x+y solid solutions were grown on Si-face 4H-SiC applying atomic layer molecular beam epitaxy at low temperatures. The grown layers consist of twinned 3C-SiC revealed by cross section electron microscopy. The germanium was incorporated on silicon lattice sites as revealed by atomic location by channeling enhanced microanalysis transmission electron microscopy studies. The Ge concentration of the grown 3C-(Si_1-xC_y)Ge_x+y heteroepitaxial layers decreases with increasing growth temperatures, but exceeds the solid solubility limit.

Abstract: In this work, we have studied the crystal defectiveness and doping activation subsequent to ion implantation and post-annealing by using various techniques including photoluminescence (PL), Raman spectroscopy and transmission electron microscopy (TEM). The aim of this work was to test the effectiveness of double step annealing to reduce the density of point defects generated during the annealing of a P implanted 4H-SiC epitaxial layer. The outcome of this work evidences that neither the first 1 hour isochronal annealing at 1650 - 1700 - 1750 °C, nor the second one at 1500 °C for times between 4 hour and 14 hour were able to recover a satisfactory crystallinity of the sample and achieve dopant activations exceeding 1%.

Abstract: Electron energy loss spectroscopy (EELS) and ab initio simulations are combined in this study to produce an atomistic interpretation of the interface morphology in lateral 4H-SiC / SiO₂ MOSFETs with deposited gate oxides. This allows the question of interface abruptness, and the presence the postulated SiO_xC_y interlayer to be explored for a subset of devices with deposited oxides. From comparison between EELS and ab initio calculation the interfaces considered are best described as abrupt, but stepped, transitioning without any of the carbon excess or SiO_xC_y interlayer that have been described for other devices observed.

Abstract: Step-controlled growth of 4H-SiC epitaxial layers leads to the formation of a step-bunched morphology along the surface with larger macrosteps, composed of smaller microsteps of several Si-C bilayer heights. As thermal oxidation is an orientation-dependent process, a multi-faceted surface is expected to exhibit a different oxidation behavior compared to a perfectly planar surface. In this work, step-bunched surfaces after oxidation are investigated by high-resolution atomic force microscopy (HR-AFM) and transmission electron microscopy (TEM) indicating a morphological change in the early stages of thermal oxidation. An orientation-dependent oxidation model is used to correctly describe variations of the oxide thicknesses at isolated macrosteps.

Abstract: InGaN/GaN multiquantum well (MQW) structures have been grown on cone-shaped patterned sapphire substrates (CPSS) by metalorganic chemical vapor deposition (MOCVD). From the transmission electron microscopy (TEM) results, we found that most of the threading dislocations (TDs) in the trench region of the CPSS were bent by lateral growth mode. Also the staircase-like TDs were observed near the slant region of the cone pattern, they converged at the slope of the cone patterned region by staircase-upward propagation, which seems to effectively prevent TDs from vertical propagation in the trench region. The associated dislocation runs up into the overgrown GaN layer and MQW, and some (a+c) dislocations were shown to decompose inside the multi-quantum well, giving rise to a misfit segment in the c-plane and a V-shape defect. From cross-sectional TEM, we found that all V defects are not always connected with TDs at their bottom, some V defects are generated from the stacking mismatch boundaries induced by stacking faults which are formed within the MQW due to the strain relaxation.

Abstract: Mechanical and biological functions of b-tricalcium phosphate (b-TCP) ceramics is of importance with respect to medical application such as bone graft substitute. The degrees of crystallynity and morphology of as-prepared b-TCP powders are concerned with the above functions. Mechanochemical synthesis is a process of producing a fine particle of b-TCP through an intermediate phases (precursor) of calcium phosphate. The b-TCP precursor synthesized by mechanochemical reaction, followed by heat-treatment, was analysed by using transmission electron microscopy, X-ray diffraction and Fourier transformation infrared spectroscopy. The hydrate layer and carbonate ions involved in the precursor were found to affect the degrees of crystallinity and morphology of as-prepared b-TCP particles at a certain temperature, 700 °C. The specific characteristics of crystallinity and morophology of as-prepared b-TCP particle is expected to be favorble to forming and sintering of b-TCP ceramics.

Abstract: Recently nano-hydroxyapatite (nano-HA) has been used as a new biomaterial in medical and dental fields. There are many methods to synthesize the nano-HA. In the present study, the nano-HA was synthesized under various reaction conditions by a wet method using neutralization reaction of calcium hydroxide suspension and phosphoric acid solution. The physicochemical properties of the nano-HA were characterized by XRD, FTIR, TG and TEM. The XRD, FTIR and TEM results indicated that the nano-HA samples were pure and the sizes were less than 50 nm. However, all samples contained carbonate and the contents were determined to be 2-4% by TG. The crystallinity of the nano-HA increased higher at body temperature of 37°C than at lower temperature of 7-10°C.

Abstract: In this article, we have studied the process of silver nanoparticles (AgNPs) aggregation and to stop aggregation 0.3% Polyvinylpyrrolidone (PVP) was used. Aggregation study carried out via UV-vis spectroscopy and it is reported that the absorption spectrum of spherical silver nanoparticles were found a maximum peak at 420 nm wavelength. Furthermore, Transmission Electron Microscopy (TEM) were used to characterized the size and shape of AgNPs, where the average particle size is around 10 to 25 nm in diameter and the AgNPs shape is spherical. Next, Dynamic Light Scattering (DLS) were used, owing to observed size distribution and self-correlation of AgNPs.