Papers by Keyword: Channeling

Abstract: Ion implantation, as a way of doping the 4H-SiC crystal, is one of the key components of modern power device fabrication. Aluminum is used to form p-type wells for the body of n-MOSFETs and low resistance p-type contacts using heavy doping. Therefore, the ion implantation process needs to be controlled over a wide range of process conditions including implant energies and doses. The fact that Al in 4H-SiC exhibits very low diffusion puts additional burden on the accuracy and predictability of any ion implantation engineering. In device design, these requirements can be addressed by applying computer simulations to predict doping profiles ahead of the actual implant step performed in a manufacturing facility. The accepted way to predict doping profiles is based on the binary-collision approximation (BCA), numerically implemented as a statistical Monte-Carlo (MC) method [1]-[3]. Nowadays, one can refer to simulation packages available from commercial vendors [4] for studying ion implantation using BCA-MC algorithms. However, while the physical accuracy of BCA models implemented in these packages has shown to be quite remarkable, predictable simulations for a complex material system as 4H-SiC requires calibration from data including secondary ion mass spectrometry (SIMS) and scanning electron microscopy (SEM).

Abstract: Channeling of B and Al ions in 4H-SiC(0001), has been investigated by secondary ion mass spectrometry (SIMS). Ion implantations have been performed between room temperature (RT) and 600 °C at various fluences. Before implantation, the major crystal axes were determined and the sample was aligned using the blocking pattern of backscattered protons. As expected, the depth distribution of the implanted ions along a crystal direction penetrates much deeper compared to non-channeling directions. At elevated temperatures, the channeling depth for 100 keV Al-ions is decreased due to lattice vibrations. For 50 keV B-ions, the temperature effect is minor, indicating a smaller interaction between target atoms and B. Simulations has been performed using SIIMPL, a Monte Carlo simulation code based on the binary collision approximation, to predict experimental data and get a deeper insight in the channeling process.

Abstract: During ion implantation into monocrystalline semiconductors, some of the implanted atoms will be deflected to crystal directions along which they may penetrate deeply into the crystal. We investigate such channeling effects for Al and N implantation into 4H-SiC by Monte Carlo simulations. The focus of the work is on the effects of channeling on doping profiles, the relevance for the net doping of typical power electronic devices, and the influence of scattering oxides.

Abstract: In the present investigation, the innovated drawing method combined with calibration process by elastic steel element of hemispheric surface part is studded. During drawing process strong meridional lengthen strength appears. That influence on necking and differential deformation distribution. In its tern, that influence on sizes and surface accuracy. Elastic element, produced of spring steel and placed along with solid punch designed to calibrate part in final drawing stage due to elastic strength happened in it. A simulation of hemispheric surface part drawing with elastic element was held. Experiment demonstrates positive influence of elastic element to decrease necking till 15-18% from started thickness. The produced part has correct strain-stress state, exact surface and minimum dispersion of dimensions.

Abstract: In an experiment conducted at the Tomsk synchrotron "Sirius", the photon yield of parametric X-ray radiation generated by 500 MeV electrons in a tungsten monocrystal in Bragg geometry has been studied. The (111) tungsten monocrystal, having a thickness of 1.7 mm and a surface mosaicity of not more than 80^², was oriented at the Bragg angle θ_B = 45^° to the direction of the electron beam. The photons were detected at the angle 2θ_B = 90° relative to the electron beam. A comparison of PXR angular distributions with calculations has been carried out with taking into account the actual conditions of the experiment.

Abstract: The previously revealed features of orientation dependences in the experimental research devoted to the channeling of ions in the multicomponent crystals of yttrium iron garnet are the reflection of the complex structure of a crystalline material. The study incorporates the development of a numerical model describing the distribution of fast ion flux in the crystal of garnet in the framework of the binary collision theory. The model is intended for the detailed elucidation of the causes of the discovered features. The calculation demonstrated the orientation dependence features similar to those established in the experiments.

Abstract: This paper mainly focuses on the investigation to the Zhongguancun Street and western North Fourth Ring Road intersection which is the traffic centre of Zhongguancun. Through traffic survey, traffic simulation and analysis, the depth dissection is carried on for the intersection’s congestion question. Improvement measures are proposed for signal timing and traffic channeling, and VISSIM is used for the simulation. Finally the performance is evaluated with analysis of delay time, travel time and queue length.

Abstract: In this work under-mask penetration of Al+ ions implanted in 4H-SiC is investigated by computer simulation based on the Monte-Carlo binary collision approximation (MC–BCA). Results indicate that a small fraction of ions, implanted normal to a (0001) 4H-SiC wafer (8° off-axis towards the {11-20}), is scattered and become channeled in the <1120> directions perpendicular to the <0001> axis. Due to this phenomenon, doped regions with concentration ≤ 10− 4 of the peak value, may extend laterally for a few µm below the edge of a SiO2 mask.

Abstract: We investigate theoretically the angular distributions and the rainbows of 1 GeV protons channeled in the ropes of (10, 0) single-wall carbon nanotubes. The rope length is varied between 0.53 and 5.29 µm. The angular distributions of channeled protons are generated using the numerical solution of the proton equations of motion in the transverse plane and the computer simulation method. We use Molière’s expression for the continuum interaction potential of the proton and the rope. The rainbow lines in the impact parameter plane and scattering angle plane are also determined numerically. We show that these lines ensure the full explanation of the angular distributions. The possible applications of these results are discussed.

Abstract: 500 keV nitrogen implantations at different tilt angles (0o, 0.5o, 1.2o, 1.6o, 4o) with respect to the c-axis of 6H-SiC were carried out. Radiation damage distributions have been investigated by Backscattering Spectrometry combined with channeling technique (BS/C) using 3550 keV 4He+ ion beam. A comparative simultaneous evaluation of the damage depth distributions in the Si and C sublattices of 6H-SiC led to a correction factor of 0.8 in the electronic stopping power of 4He+ ions along <0001> channel. Full-cascade Crystal-TRIM simulations with the same set of damage accumulation model parameters could reconstruct the measured shapes and heights of damage distributions for all implantation tilt angles. Secondary defect generation effects in addition to the primary point defect accumulation were assumed in the analysis.