N.G. Chechenin

Damage and aluminum distributions in sic during ion implantation and annealing

Abstract Damage buildup in SiC during ion implantation of Al + with an energy of 90 keV and flucnces of 10 13 –10 16 ions/cm 2 at room temperature was studied. It was observed that the surface concentration of displaced host atoms and χ min increase rapidly in the fluence range of 3 × 10 13 –10 15 cm −2 and change weakly outside this range. The amorphization of the surface layer occurred at a fluence of φ c ≈ 8 × 10 14 cm −2 . The thickness of the amorphous layer as well as the depth and the width of the Al-atoms profile exceed the values calculated lor an amorphous target. The possibility of recrystallizing the damaged layer depended on the ion fluence. The precipitation of Al-atoms at structural defects was observed.

Depth distribution analysis of martensitic transformations in Xe implanted austenitic stainless steel

Abstract In recent years the implantation of noble gases in metals has been found to induce some exciting phenomena such as formation of inclusions containing solid gas at extremely high pressures. In stainless steels these inclusions are the origin of a stress-induced martensitic fcc → bcc phase transformation in the implanted layer. In this work we present results from a depth distribution analysis of the martensitic phase change occurring in Xe implanted single crystals of austenitic stainless steel. Analysis was done by in situ RBS/channeling analysis, X-ray diffraction and cross-section transmission electron microscopy (XTEM) of the implanted surface. It is found that the martensitic transformation of the surface layer occurs for fluences above 1 × 10 20 m −2 . The thickness of the transformed layer increases with fluence to ≈ 150 nm at 1 × 10 21 m −2 , which far exceeds the range plus straggling of the implanted Xe as calculated by the TRIM computer simulation code. Simulations using the MARLOWE code indicate that the thickness of the transformed layer coincides with the range of the small fraction of ions channeled under random implantation conditions. Using cross sectional TEM on the Xe implanted crystals, the depth distribution of gas inclusions and defects can be directly observed. Besides microstructural details of the near surface region, this technique offers a well calibrated depth scale to be compared with that derived by RBS. Using X-ray diffraction on implanted single crystals, the solid epitaxial nature of the Xe inclusions, induced prior to the martensitic transformation, was established. The lattice constant obtained from the broad diffraction peak indicates that the pressure in the inclusions is ≈ 5 GPa.

Investigation of laser-induced defect formation in CdTe crystals by Rutherford backscattering

Rutherford backscattering has been used to study defect formation processes in a CdTe surface layer exposed to pulsed laser radiation. It was established that scattering centers are formed only at laser pulse energies exceeding the melting threshold of the surface. The spatial distributions of Cd and Te and of structural defects in the irradiated layer were determined. The data are interpreted assuming intensive evaporation of one of the components (Cd).

A channeling study of ion-produced disorder in silicon carbide

Abstract The RBS/C technique is used to study the disorder buildup in silicon carbide (SiC) produced by Al+ and Ga+ ions with energies of 40 and 90 keV. The damage rate increases sharply in the fluence range near the critical value for amorphization, Φ ≈ 1 × 1014 cm−2 and = 8×1014 cm−2 for Ga+ and Al+ ions, respectively. The defect concentration rises slowly with fluence outside this range. At fluences Φ > Φc, the concept of elastic energy loss density is used in the analysis of the amorphous layer thickness. A strong decrease of the critical energy loss density, Wc, is observed when the amorphous layer expands due to fluence accumulation.

SiC amorphlzation as a result of Ga+ implantation

Abstract The ion implantation of 40 and 90 keV Ga+ ions at high doses into silicon carbide was studied. The thickness of layers randomized by ion implantation determined as a function of the ion dose and energy was compared with that expected from the theory of energy loss in elastic collisons. It was found that the data for two implantation energies could not be described by one value of critical energy deposition. Two factors are proposed to be responsible for the discrepancy: buffer layer formation and beam annealing.

Sputtering of copper crystals by soluble and nonsoluble ions

Abstract Single crystals of copper have been implanted along the 〈111〉 direction with 100 keV tin ions and 150 keV lead ions to fluences from 6 × 10 20 to 2 × 10 22 m −2 . Angular distributions and total amounts of sputtered atoms have been determined by collecting the sputtered material on hemicylindrical aluminum strips. Furthermore, the total sputter yields have been measured by the weight-loss method. In the case of implantations with tin ions, the total sputter yield of copper atoms and the partial sputter yield of tin atoms agree with the saturation concentration of tin measured by RBS analysis. This is also true for low-fluence implantations of lead, but at higher fluences the sputter yields of lead and copper are conflicting with the near-surface concentration of lead. This may partly be ascribed to changes in the shape of the RBS spectra associated with the onset of severe surface topography starting at fluences around 5 × 10 21 m −2 .

Channeling in RBa2Cu3O7 − x single crystals

Abstract The results of He + ion channeling in RBa 2 Cu 3 O 7 − x (RBaCuO) single crystals (where R = Y , Pr ) are reported. The channeling effects in Pr + Ba and Cu sublattices of the tetragonal PrBaCuO crystals are compared. The normalized yield of the backscattered particles from the channeling in the Cu sublattice is higher and the width of the angular dependence of the RBS yield is lower than those in the Pr + Ba sublattice. The experimental aligned spectra are compared with the calculated ones. The calculations take into account the diffusion in the transverse motion and energy loss of the particles. The results of channeling in orthorhombic YBaCuO crystals are also briefly discussed.

Channeling study of the orientational dependence of laser-induced damage in GaAs and GaP

Abstract Channeling was used for the study of laser-induced damage in GaAs and GaP samples with different crystallographic orientations of the surface. The greatest damage was observed for (111) GaAs and (111) GaP samples. Possible mechanisms for the damage production are discussed.

Channeling study of laser-induced damage in GaP

Abstract The damage induced by excimer-laser irradiation in a GaP single crystal is studied by channeling and Rutherford backscattering. With this technique, the displacements of Ga and P atoms are observed at a laser pulse energy as low as W = 0.1 J/cm 2 At W = 0.3–0.4 J/cm 2 the 40–60 nm surface layer is strongly randomized. Possible mechanisms for the damage production are discussed.

Visual TCAD simulation of total ionizing dose effects on advanced CMOS devices for space applications

The performance of wireless communication systems is affected mainly by the environment of its associated channel, which is characterized by a dynamic and unpredictable behaviour. In this paper different statistical satellite channel models are studied with emphasize on two main models, first is the Rice-Log normal model, due to its close representation for the satellite channel environment including shadowing and multi-path components that affect the propagated signal along its path, and second a three state model that take into account different fading conditions (clear area, moderate shadow and heavy shadowing). The communication system is enhanced through the usage of Residue-Number-System coding making benefit of its inherent features that is highlighted in the paper. The transmission system Bit Error Rate (BER), Peak-Average-Power Ratio (PAPR), and the channel capacity for each fading models are measured and analysed. These simulations are implemented using MATLAB tool and the results had shown the performance of transmission system over different channel models.The National Space Strategy (NSS) for 20-year (2016 2035) of The Royal Thai Government, in The 2nd Strategy : “To Create the Ability of Competition” with the aim to increase the cost of investment in R&D and increase the proportion of research and development personnel, is regarded as the first packing Space Technology in the economic and social development of the NSS goals. In this regard, the National Research Council of Thailand (NRCT) and the Thailand Research Fund (TRF) have agreed to provide a research cluster in the development of satellites and related space technologies including the successful creation of miniaturized satellites corresponding to the national space policy of the Royal Thai Government Currently, the size of 1U, 3U CubeSat and miniaturized observation satellites are a key target for the space technology development of many state government. Geo-Informatics and Space Technology Development Agency (GISTDA), the space technology development agency of Thai Government, is developing a 3U CubeSat for space exploration mission which is the first 3U concept designed by GISTDA, Thai universities and private sectors. A period of three-year development is already planned. The satellite mission, payloads & subsystem requirements are designed in 2017. In 2018, it is to research and develop the various subsystems. Finally in 2019, it will be built to assembly and test by GISTDA-AIT facilities and the launch opportunity will take into account. In this paper, the mission design for space exploration and subsystem requirements conceptual design are presented including the development of TT&C communication subsystem. The TT&C subsystem is built-up after the EM satellite structure manufactured. The main mission of the 3U CubeSat, to explore the space at altitude of 600km in a polar orbit, is also presented. Briefly, the National Astronomical Research Institute of Thailand (NARIT) and Mahidol University needs to study the formation of high energy particles in space : cosmic ray. Hence, the space exploration