Papers by Keyword: Electron Irradiation

Abstract: Deep level transient spectroscopy (DLTS) was used to characterize the defects introduced in n-type, N-doped, 4H-SiC while being exposed to electron beam evaporation conditions. This was done by heating a tungsten source using an electron beam current of 100 mA, which was not sufficient to evaporate tungsten. Two new defects were introduced during the exposure of 4H-SiC samples to electron beam deposition conditions (without metal deposition) after resistively evaporated nickel Schottky contacts. We established the identity of these defects by comparing their signatures to those of high energy particle irradiation induced defects of the same materials. The defect E_0.42 had acceptor-like behaviour and could be attributed to be a silicon or carbon vacancy. The E_0.71 had intrinsic nature and was linked to a carbon vacancy and/or carbon interstials.

Abstract: There has been an increased interest in improving the properties of alumina ceramic to be used in nuclear applications. This paper focuses on the effect of electron beam irradiation on the morphology of alumina ceramic. Alumina ceramic pellet was prepared by compacting of fine alumina powder then subjected for sintering process at 1500oC for 2 hours using electrical heating furnace. Then, the pellets were irradiated with electron beam of total dose 200 kGy with vary of electron beam speed of 100kGy/pass and 25kGy/pass. Scanning Electron Microscope and Atomic Force Microscope were used to observe the morphology of the sample. The results show that the irradiation changes the grain of the alumina ceramic due to bonding of particles caused by energy from electron beam especially at high speed. Furthermore, the surface roughness decreases after irradiation and become lower at low speed. Finer grain is obtained on the surface after irradiated at lower speed. The high energy of electron beam destroyed the particles during long contact period to the surface when low speed of electron beam is applied.

Abstract: Effects of electron irradiation in n-4H-SiC have been studied by the methods of the capacitance--voltage characteristics and photoluminescence. It was found that the carrier removal rate (Vd) reached a value of ~0, 25 cm^{- 1}. Full compensation of samples with an initial concentration of 1.2 10¹⁵ cm ^-3 was observed at doses of about 5 10¹⁵ cm ^-2. Simultaneously with the increase in the degree of compensation, the intensity of the “defect luminescence”, typical of 4H SiC, became higher. The physical compensation mechanisms were analyzed for the samples under study.

Abstract: Silicon carbide (SiC) is an important material that has the potential to be used in the nuclear industry. The surface of 0001 silicon carbide, 4H polytype wafer has been irradiated by electron accelerator at the accelerator voltage of 3 MeV and 10 mA beam current. Samples were irradiated to dose received of 1000 kGy, 1500 kGy and 2000 kGy. Characterization of the samples have been done using X-ray diffraction (XRD) and scanning electron microscopy (SEM) to investigate the electron irradiation effect on structure as well as current-voltage tests to study electrical property.

Abstract: Molecular dynamics was used to simulate the electron irradiation of two adjacent single-walled carbon nanotubes (SWNTs) via the Primary Knock-on Approximation. Temperature effects on the creation and evolution of defects were studied. The most prevalent defect was atomic vacancy which evolved into multi-vacancy over successive irradiation impacts. Cross linking was also observed. As temperature increased, mending of damage was promoted and the stability of bonds decreased. A new morphology of cross linking in the form of interconnecting carbon rings is presented.

Abstract: In freestanding n-type 4H-SiC epilayers irradiated with low-energy (250 keV) electrons at room temperature, the electron paramagnetic resonance (EPR) spectrum of the negative carbon vacancy at the hexagonal site, VC- (h), and a new signal were observed. From the similarity in defect formation and the spin-Hamiltonian parameters of the two defects, the new center is suggested to be the negative C vacancy at the quasi-cubic site, VC- (k). The identification is further supported by hyperfine calculations.

Abstract: To solve the problem of the limitation to improve device performance in standard Si integration technologies and to develop radiation-harsh devices, the irradiation effects of Si_1-xC_x source/drain (S/D) n-type metal oxide semiconductor field effect transistors (n-MOSFETs) have been investigated. It is shown that the drain current and the maximum electron mobility of Si_1-xC_x n-MOSFETs decrease by electron irradiation. The reduction of the device performance can be explained by the radiation-induced lattice defects in the devices. However, the electron mobility enhancement effect by adding C remained after an electron irradiation up to 5×10¹⁷ e/cm².

Abstract: We investigated annealing behavior of the carrier lifetime and the deep levels in electron irradiated n-type and semi-insulating 4H-SiCs. We observed two peaks for each sample by photo induced current transient spectroscopy (PICTS) measurements, and their heights depended on annealing temperature. By comparing the annealing behavior of the peak height with reported temperature dependence of concentrations of various defects, we speculated that the observed peaks originate from either V_SiV_C, C_SiV_C or EI4.

Abstract: This paper presents the thermoluminescence (TL) response and sensitivity of various dopant concentration of Dy into borate glass. Borates glass present absorption coefficient that closely to human bone and teeth. This fact makes borate as an ideal material for TL material either for medical or environmental dosimeter. Therefore, a series of glasses based on xCaO-(100-x)B₂O₃ system (0 x 100) % weight has been prepared by using melt quenching method. In this research, Dy doped (0.01-0.4) mol% to 30CaO-70B₂O₃ glass sample were studied to investigate the TL properties in terms of dose-response relationship and sensitivity. Samples were irradiated to various doses range 0.5-4.0 Gy subjected to 6 MV photon irradiation by using LINAC Primus MLC 3339. The TL intensity of various dopant concentration were studied and it was founds that the 0.3 mol% Dy has the highest TL response and has linear dose response relationship. The highest sensitivity was calculated as 58 nC.mg^-1.Gy^-1 for 0.3 mol% Dy concentration.

Abstract: Structural defects induced by electron irradiation of n-Cz-Si wafers were identified. The influence of the annealing conditions in a chlorine-containing atmosphere on the structural and luminescent properties of the samples was examined and the optimal annealing conditions were found. Light-emitting diodes based on electron-irradiated and high-temperature-annealed wafers were fabricated by a vapour-phase epitaxy technique and their luminescence properties were studied. A high-intensity dislocation-related D1 line was observed at 1.6 μm in the room-temperature electroluminescence spectrum.