Papers by Keyword: Surface Reconstruction

Abstract: In this paper, we study high-temperature H₂, N₂, and H₂/N₂ surface conditioning processes prior to the SiO₂ deposition as a promising approach for SiO₂/4H-SiC interface preparation in metal-oxide-semiconductor field-effect transistors (MOSFET). A thorough electrical analysis is presented, consisting of temperature-dependent transfer characteristics as well as reliability studies regarding bias temperature instabilities (BTI) and dielectric breakdown behavior. Especially N₂-containing surface pretreatments were found to greatly suppress electron traps, whereas hole trapping is enhanced. Finally, X-ray photoelectron spectroscopy (XPS) was utilized to elucidate the elemental surface composition after the different annealing procedures. The obtained results are in good agreement with the electrical characterization and complement already published results regarding the formation of surface reconstructions on 4H-SiC through H₂ and H₂/N₂ annealings.

Abstract: Characterizing a fruit’s mechanical behavior is an important step towards reducing economic losses due to bruising. Several 3D scanning technologies allow to obtain the external geometry of a fruit, but no easily accessible tools exist for the acquisition of the geometry of internal structures such as the core. We propose a low-cost destructive method for tomographic reconstruction of a fruit from scanned slices. A method for overcoming the difficulties in registering the different images is also presented.

Abstract: The new reconstructions formed by sodium adsorption on Pb-terminated Si (111) surface were obtained: 2x2+2sqrt3x2sqrt3, 4x1, 3x3 and others. These surface structures have been observed by low-energy electron diffraction (LEED) and phase diagram for 2D binary (Na,Pb)/Si (111) system has been obtained. The (Na,Pb)/Si (111) system is considered as a two-dimensional alloy layer with highly ordered structure. Influence of two-dimensional alloys on surface conductivity of Si (111) substrate has been studied in situ by four-point-probe method.

Abstract: With the extended applications of hexagonal silicon carbide (h-SiC) in the various fields, particularly in the application of the electronic devices, more and more attentions have been focused on the micro structures as well as their physical properties of h-SiC surface. In this study, we have performed the first principal calculations to compare the formation energies of four typical defects (Vc, Vsi, C_I and Si_I) on the 4H-SiC (0001) surface as well as in the interior layers. Due to the surface reconstruction and the reduced lattice constrain, the optimized structures of the defects on/near the 4H-SiC (0001) surface are quite different from the ones in the deeper layers. The distinguished formation energies as function of chemical potential indicate that we may control the defects concentrations in different layers by tuning the environmental conditions. This theoretical work provides a significant understanding to the formation mechanism of the point defects on the 4H-SiC surface, and paves a way to the modification of the SiC surface via electron irradiation or ion implantation with micro-defects introduced.

Abstract: Graphene is a 2D material with potential for almost any purpose, thanks to a combination of excellent characteristics, e.g. high electrical conductivity. Graphene grown on SiC wafers is one of the promising routes for graphene integration into planar technology electronic applications. Synthesis is based on the decomposition of a SiC single crystal surface at high temperature, where Si-terminated SiC substrates require the formation of the C buffer layer. In spite of numerous experimental and theoretical works the understanding and control upon crucial factors such as step and terrace stability or surface roughening is far from been fully comprehended and then technologically optimized. We present experimental results on the deposition of graphene onto Si-terminated 6H-SiC. We analyze the effect of ex situ and in situ conditionings of the SiC surface in the thermal decomposition and reconstruction of the SiC terraces, toward higher control upon the growth process of graphene films.

Abstract: The absolute surface energies of three major low index surfaces of cubic silicon carbide (3C-SiC) are determined by first-principles density functional theory calculations. Calculations show that among clean 3C-SiC surfaces the Si-terminated 3C-SiC(001)-(3x2) surface has the lowest energy. The second and third lowest energy surfaces are the Si-terminated 3C-SiC(111)-(√3x√3) surface and the nonreconstructed 3C-SiC(110) surface. Hydrogen passivation greatly reduces both the absolute surface energies of the low index 3C-SiC surfaces and the surface energy anisotropy. In particular, the surface energies of fully passivated 3C-SiC(110) and (111) surfaces become indistinguishable at hydrogen-rich deposition conditions.

Abstract: When remanufacturing complex surface parts, such as twisted blade, it is difficult to obtain an accurate model. An iterative Genetic-algorithm-based-surface reconstruction method for repair of twisted blade is presented. Genetic algorithm is applied in parametrizing data points and computing knot vectors. Then, the control points of the fitting B-spline surface are calculated by least-squares approximation through either SVD or LU methods. It shows that the accuracy of the method is improved significantly when three different twisted blades surfaces are verified by using the method.

Abstract: Topography and surface roughness is defined as a set of surface textures formed due to used machining or other production technology. It is a key factor mainly for dynamically stressed components. Greater surface roughness negatively affects the fatigue strength of component or its wear resistance.The paper deals with the visualization and processing of data obtained from a laser confocal microscope Zeiss LSM 700. Data acquired by LSM software ZEN2009 are exported in the text form of 3D coordinates of the image data points and are arranged as a set of 2D profiles with resolution 1.10^-7 m. The aim is to describe an alternative method of evaluating raw data extracted from z-stack of acquired TIFF images in order to achieve higher precision and identify the topography of the scanned sample surface. Different methods of data processing have been tested to eliminate deficiencies located mainly in the parts of the scanned surface with low intensity.

Abstract: B-spline curve parameters were estimated by the least squares. The influences of the scanning angle to point cloud density was discussed. In the case of scanning distance and horizontal being sure, the smaller the vertical scanning angle, the larger point cloud density, it can reflect the characteristics of the surface cross-section more accurately. The factors affecting the accuracy of the surface reconstruction were discussed. The surface fitting order has a greater degree of influence on the accuracy of surface reconstruction. When the surface order was 4 and the number of control points was 75, the surface-point cloud deviation was 0.188mm by the segmented fitting.

Abstract: Use Geomagic Qualify software, take the distance between the measure point and the surface model as the main evaluation index, respectively evaluate the quality of the shoe last surface reconstructed by tradition surface modeling way and quickly surface modeling approach, through 3D comparison, 2D comparison and special point comparison, get the 3D deviation chart and the error percentage distribution list, through the analysis and comparison of the charts, the two ways of surface reconstruction method are in line with the requirements of the surface, select the appropriate method of surface reconstruction according to the different requirements of surface reconstruction quality, provide the reference basis to surface measurement and surface reconstruction of other models.