Papers by Keyword: Surface Morphology

Abstract: Boron (B) doping sources and crucible materials for stable, reproducible and high concentration B doping in fluorescent SiC (f-SiC) were investigated. When a Ta crucible was used with BN powder as a B doping source were used, B doping did not occur owing to too low C/Si ratio. On the other hand, when a C crucible and suitable Ta components inside the crucible were used, a high B concentration of 1.58 × 10¹⁹ cm^-3 was obtained, owing to the high C/Si ratio. The results indicate that a C crucible with optimal Ta components and BN powder are suitable for high concentration B doping.

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: This research is aimed to study the effect of sintering temperature on crystalline structure and surface morphology of NdFeO₃ oxide alloy materials. NdFeO₃ was synthesized by solid state reaction method with mixing of 99.9% Nd₂O₃ and 99.9% Fe₂O₃ as precursors. Three samples with different process were made in this experiment. The 1^st (#1) and 2^nd (#2) samples were sintered for 84 hours at 950°C and 600°C. Calcination procces was carried out at 950°C for 50 hours. The 3^rd (#3) sample was sintered for 84 hours at 600°C without calcination process. The samples were characterized by using SEM (Scanning Electron Microscopy) and XRD (X-Ray Diffraction). Based on the SEM characterization result, it was obtained that the sintering temperature influence on surface morphology of NdFeO₃ grain size. The XRD analyze was obtained FWHM (Full Width at Half Maximum) value of sample #1, #2 and #3 are 0.11°, 0.10°, and 0.31°, respectively. The value of FWHM was associated with the peak at 2Θ of 32.53° for all sample, it is indicated of hkl (121). Further calculation based on crystallography data was carried out by rietveld method with rietica software and the best quality will be applied as a gas sensor materials.

Abstract: A promising two-dimensional material for applications in optoelectronic and photonics, MoS₂ is in focus since last decade. Its optical, structural and electronic properties are of practical importance along with its exciton dynamics. MoS₂ thin films were synthesized with Chemical Vapour Deposition (CVD) technique on Si/SiO₂ substrates. The thickness dependent regularities were controlled and examined to quantitatively control the film quality with thickness variation. Various characterization techniques were employed to investigate structural and morphological changes induced systematically to reveal the van der waal stacked layers of MoS₂ material. The In-plane characteristic mode E¹_2g and out of plane A_1g vibrational modes were detected in different configurations of film’s structure. Optical absorption spectra gave us information on photon energy with the absorbance; extrapolation of this curve gave optical bandgap (E_g) in the form of Tauc plot. These energies can be associated to interband electronic transitions in the Brillouin zone. The intrinsic excitonic response as a consequence of layer stacking and velly indexing can be attributed to this change in bandgap from 1.68 to 1.91 eV. Surface morphology of the as-grown films also provides better understanding of MoS₂ material with root mean square (RMS) roughness in the range of 1.32 to 3.85 nm.

Abstract: In this work, the reaction and nucleation mechanisms of the electrochemical deposition of copper on an indium-doped tin oxide (ITO) conductive glass substrate in a sulfate solution were characterized respectively by electrochemical methods Such as: cyclic voltammetry and chronoamperometry.The transients (current-time) obtained were analyzed by the model of Scharifker and Hills. The deposited copper layer can be described by a model involving instantaneous nucleation at active sites and diffusion controlled 3D growth. The values of the diffusion coefficient D for the Cu^{2 +} ions are also calculated. Electrochemical techniques were followed by morphological characterizations with atomic force microscopy (AFM).All experiments were carried out in an acid solution at pH 4.

Abstract: Heteroepitaxially grown multilayered thin film structures have been attracted of great interest due to its potential applications in photovoltaic/light emitting/electronics devices. The thin film morphology plays an important role in enhancing its related physical properties. It is not easy to simulate the multi-layered thin film structures due to the influence of the interface/surface fluctuation. However, the phase field method, based on thermodynamics and Cahn-Hilliard diffusion model, can predict the thin film morphologies without tracking the interfaces. In this paper, a new phase field model was developed for predicting multi-layer structures with multi-order parameters. The morphologies with strain distributions of the quantum wells, quantum dots and buffer layers structures were investigated in the current study. We found that the strain distribution has a strong effect on the suface/interface morphologies in the multilayered structures. Some simulation results are consistent with experimental observations.

Abstract: We aimed to investigate the effects of alumina blasting and alkaline treatment on the immobilization of gelatin-fluvastatin complexes on titanium disks. Blasted titanium disks were submicron-sized porous while the alkaline treated disks were submicron-and nanoporous. XPS analysis revealed homogeneous coverage of titanium disks with a gelatin layer on top of an intermediate polydopamine treatment. The highest amount of fluvastatin immobilization was observed on top of alkaline treated titanium as compared to the blasted disk. A combination of alkaline pre-treatment followed by polydopamine-assisted immobilization of gelatin facilitated optimal loading of fluvastatin onto titanium dental implants.

Abstract: The paper dwells upon the specifics of worn spots being formed on a silicon-carbide crystal in microscratching of iron, cobalt, and nickel. Analysis was done using a Versa 3D dual-beam electron microscope. The chemical composition of worn spots was studied by local X-ray microanalysis. It was found out that the amount of metal transferred to the silicon-carbide worn spot was associated with the electron structure of metal atoms.

Abstract: The defect structure at the growth front of 4H-SiC boules grown using the physical vapor transport (PVT) method has been investigated using high resolution x-ray diffraction and x-ray topography. The crystal parameters such as the c-lattice constant exhibited characteristic variations across the growth front, which appeared to be caused by variation in surface morphology of the as-grown surface of the boules rather than the defect structure underneath the surface. X-ray topography also revealed that basal plane dislocations are hardly nucleated at the growth front during PVT growth of 4H-SiC crystals.

Abstract: We have investigated the dependence of the macrostep height on various additives in solution growth of n-type 4H-SiC. Surface modification by adding transition elements in periods 4‒6 (Sc, Ti, V, Mn, Fe, Co, Ni, Cu, Y, Nb, Mo, Ce, and W) and group 13‒14 elements (B, Al, Ga, Ge, Sn) was systematically studied to find additives improving smoothness of the growth surface. We found that Sc, Co, Mo, and Ge improved surface smoothness in addition to the already-known additives, such as Al, B, and Sn. Besides, these additives (Sc, Co, Mo, Ge) give no measurable influence on the conductivity of n-type grown crystals. These results demonstrated that Sc, Co, Mo, Ge and Sn are useful additives for solution growth of n-type 4H-SiC.