Papers by Keyword: Electron Trap

Abstract: The long afterglow luminescent materials Sr₃Al₂O₆: Eu, Sm and Sr₃Al₂O₆: Eu, Dy (denoted as S1 and S2, respectively) were synthesized via solid-state reaction. X-ray diffraction, fluorescence spectrophotometer and thermal luminescent spectroscope were employed to characterize the phosphors. The excitation spectra are all well simulated by eight Gaussian curves, indicating that they originate from the 4f⁷(⁸S_7/2)–4f⁶5d(⁸H_J) transitions of Eu²⁺. The excitation spectra intensity of S1 is much stronger than that of S2, which indicates that there is a more efficient energy transfers from Sm³⁺ to Eu²⁺. The thermally stimulated luminescence (TSL) curve can be fitted to four TSL peaks and the low-temperature TSL peak is responsible for the long lasting phosphorescence. The proposed explanation for the afterglow property is discussed.

Abstract: The distribution of electron trap depths in hydrocarbons seems to be continuous in the range from 0.6 eV to 2.2 eV. However, it seems that among the deepest traps in n-heptane also the discrete ones appear as well. The influence of the admixture of other alkane on Ps intensity in alkanes was examined. As far as the admixture of an alkane with a shorter chain is concerned, the depth of the traps and their amount remain almost the same like in the case of the pure solvent. When it comes to essentially non-miscible solid heptane and nonane, a total lack of electron accumulation effects was observed. It is an exception among the mixed alkanes investigated here and needs a careful study.

Abstract: A systematic study of o-Ps intensity quenching by different wavelength of SWIR light was performed for a set of n-alkanes which form different crystal structures. The maximal wavelength able to quench was determined for two temperatures. The results for odd- and even-numbered alkanes were compared from this point of view. A systematic decrease in the maximal wavelength with shortening the carbon chain was found. Two kinds of traps were observed in the alkanes with chain length exceeding 30 carbon atoms, one kind only in the shorter ones. It was found that in a binary mixture of alkanes the traps are shallower than in the neat ones.

Abstract: Lithium tetraborate (LBO or LTO) single crystal seems to be a promising new material for thermoluminescent dosimeter (TLD) and SAW resonators. In the present work, thermoluminescence (TL) characteristic and TL spectra of LTO single crystal grown by Bridgman method were measured, the kinetic parameters of TL traps were calculated, and TL spectra were analyzed. The result shows: The primary glow peaks are at about 186oC and 313oC. The activation energies of the traps corresponding to the two TL peaks are 0.96eV and 1.56eV, and the frequency factors are about 7.94×109s-1 and 6.31×1012s-1. The TL spectra of LTO crystal extends from 350nm to 460nm, and has its maximum at about 381nm. The intrinsic luminescent centers can send the energy from crystal lattice to Cu+ ions, because the activation energies of two are quite similar, and the Cu+ ions become new luminescent centers to increase TL sensitivity when Cu ions are doped into LTO crystals.

Abstract: Dense tin oxide based ceramics are a new type of varistor materials. To further understand the electrical properties of SnO2 varistors doped with CoO, Nb2O5, and Cr2O3, the techniques of capacitancevoltage (C-V) measurement and deep level transient spectroscopy (DLTS) were used to investigate the electron traps in the SCN samples (doped with 1.0 mol% CoO and 0.05mol% Nb2O5) and SCNCr samples (doped with 1.0 mol% CoO, 0.05mol% Nb2O5 and 0.05mol% Cr2O3). Two electron traps were detected: trap T1 is located at Ec - 0.30 ± 0.01eV and trap T2 is located at Ec – 0.69 ± 0.03eV for both SCN and SCNCr samples. The variations in the donor density and trap density could be related to the addition of chromium oxide. The features of these traps are discussed based on the defect theory related to the SnO2 varistors.

Abstract: The authors have investigated deep levels in electron-irradiated n- and p-type 4H-SiC epilayers by deep level transient spectroscopy (DLTS). By low-energy electron irradiation at 116 keV, the Z1/2 and EH6/7 concentrations are increased in n-type samples, and the concentrations are almost unchanged after annealing at 950°C for 30 min. In p-type samples, the unknown centers, namely EP1 and EP2, are introduced by irradiation. By annealing at 950°C, the unknown centers are annealed out. The HK4 center (EV + 1.44 eV) is increased by the electron irradiation and subsequent annealing at 950°C. The dependence of increase in the trap concentrations by irradiation (NT) on the electron fluence reveals that NT for the Z1/2 and EH6/7 centers is in proportional to the 0.7 power of electron fluence, while the slope of the plot is 0.5 for the HK4 center. The Z1/2 and EH6/7 centers show similar annealing stage and are thermally stable up to 1500-1600°C, while the HK4 center is annealed out at about 1350°C. The Z1/2 and EH6/7 centers may be derived from a same origin (single carbon vacancy: VC) but different charge state. The HK4 center may be a complex including VC.

Abstract: In this paper, the electrical properties of pre- and post-rapid thermal annealed 4H SiC-based gate oxide grown in 10% nitrous oxide (N2O) and in dry oxygen have been investigated, compared, and reported for the first time. After treating the nitrided gate oxide in rapid thermal annealing (RTA), oxide breakdown characteristic has been improved significantly. This improvement has been attributed to the reduction of SiC–SiO2 interface-trap density and the generation of positive oxide charge, acting as an electron-trapping center. However, deleterious effects have been observed in non-nitrided oxide after subjected to the same RTA treatment. The differences in oxide-breakdown strength of these oxides have been explained and modeled.