P. Iacconi

Contribution of SiO/sub 2/ in neutron-induced SEU in SRAMs

The aim of this work is to show the contribution of nuclear events occurring with oxygen nuclei in SRAM-oxide such as SiO/sub 2/ and emphasize that they are likely to increase the soft error rate by about several tens of percent. Recoil energies are calculated with a dedicated subroutine, which accounts for elastic and nonelastic reactions in the 5-150-MeV energy range. SEU cross sections are evaluated using the criterion of critical energy deposited in a cubic sensitive volume.

TL characterisation of a CVD diamond wafer for ionising radiation dosimetry

Abstract This work reports some thermoluminescent features of 28 samples cut from a free-standing polycrystalline diamond wafer grown by microwave assisted plasma CVD. All these samples show the same thermoluminescence (TL) peak at 540 K, particularly suitable for ionising radiation dosimetry. The homogeneity of synthesis in terms of TL responses as well as some criteria usually required for dosimetry work are studied.

Photoluminescence and thermoluminescence of titanium ions in sapphire crystals

Abstract Several titanium species (Ti 3+ , Ti 4+ , Ti 4+ -V Al clusters) were identified in sapphire samples from their optical spectra. In highly reduced samples, we observed only Ti 3+ centres while oxidized samples contain Ti 3+ and Ti 4+ ions as well. The formation of Ti 4+ ions occurs simultaneously with the formation of aluminium-vacancies which are charge compensators for Ti 4+ ions and act as hole traps in charge exchange process. We could observe locally and non-locally compensated Ti 4+ as well. It is shown that Ti 3+ is a deep hole trap while Ti 4+ is a deep electron trap. In the TL process they act as recombination centers for electrons and holes, respectively. However, in TL we observed only the emission of locally compensated Ti 4+ , probably because of spatial correlation.

Thermally Stimulated Conductivity and Luminescence in Polycrystalline Diamond Films

Thermally stimulated currents (TSC) and thermoluminescence (TL) have been studied in polycrystalline diamond films of different qualities in order to gain information about the deep levels present within the bandgap of this material. The TL has been studied between 300 and 670 K after UV light illumination, and the TSC between 300 and 600 K after various excitations (UV light, from a tungsten ]amp, X-rays). TL and TSC peaks are observed at 470 and 560 K, and depend on the quality of the diamond and on the illumination conditions. At low temperature three TSC peaks appear at 245, 283 and 312 K after illumination with a tungsten lamp. A spectral analysis of the 470 K luminescence and electron emission measurement shows that the defect associated with this signal is an acceptor, and the hole released is trapped on a level 2.6 eV deep. Complementary ESR measurements show that paramagnetic nitrogen centers are not involved in the peak observed at 560 K.

Thermoluminescence of a mixed rare earth phosphate powder La1−x−yCexTbyPO4

The properties of thermoluminescence (TL) observed from various mixed rare earth (RE) phosphate powders La1−x−yCexTbyPO4 are reported. TL peaks appear around −175°C, −135°C, −80°C, −35°C and +25°C and the TL emission spectra of La1−x−yCexTbyPO4 are mainly composed of characteristic line transitions of Tb3+ ions. The results show that the co-doping with Ce3+ is not required to observe the TL emission of Tb3+. A model for the recombination mechanisms of the various TL peaks is discussed.

Zircon in charnockitic rocks from Rogaland (southwest Norway)" Petrogenetic implications

Zircons separated from monzonoritic rocks and quartz mangerites (igneous and metamorphic) have been studied for various mineralogical, chemical and physical properties (colour, zoning, presence of core, U distribution, morphology, lattice parameters, thermoluminescence) to determine the relationships with chemical composition of the host rocks and geological setting. The zircons grade from nearly perfectly crystalline to slightly metamict types. The crystal morphology shows prismatic habits and a striking lack of well-developed pyramidal faces, possibly indicating growth in a dry formation environment. The zircons can be divided into two groups. The first one comprises zircons from monzonoritic rocks. They are unzoned, devoid of brownish core, with a uniform U distribution, and low U content (except in Hidra). The second group comprises zircons from igneous and metamorphic quartz mangerites; they contain brownish, zoned, U-rich cores. In rocks where temperature of crystallization can be determined, Watson and Harrisons (1983) experimental data indicate strong zircon saturation. The cores are considered as inherited, a fact that can be accounted for either by dry anatexis or bulk contamination. In the Bjerkreim-Sokndal layered lopolith, previous isotopic data are confirmed, which indicate that the acidic upper part of the massif is not comagmatic with the anorthosito-noritic lower part and the monzonoritic rocks.

A Semi-empirical Approach for Heavy Ion SEU Cross Section Calculations

The main goal of this paper is to propose an approach to calculate heavy ion SEU cross sections. The starting point is the diffusion model theory, which allows the charges diffusion but does not account for electrical field in the device. This electrical field is not necessary known in the device and is difficult to be introduced simply in the calculations. For this reason, we have empirically modified the diffusion model to account for electrical field. With only one empirical parameter, our Monte Carlo simulations allow reproducing the Weibull curves obtained for several technologies. In the last section, we focus on sub-threshold events and emphasize that they are partly due to the Rutherford scattering

Theoretical model for thermally stimulated luminescence, conductivity and exoelectronic emission

A theoretical model which takes into account thermally stimulated luminescence (TSL), conductivity (TSC) and exoelectronic emission (TSEE) is proposed in this article. The model is established for the case of a single type of electron trap, a single type of recombination centre and in the presence of thermally disconnected traps. It generalizes the model of Lewandowski and McKeever by taking the TSEE phenomenon into consideration. TSEE is described as resulting from the thermionic effect and so the model applies only to a thin solid film about 10 nm thick. As an application example, the influence of various parameters involved in the model on peak shape and position is investigated.

Thermally stimulated properties of CVD diamond films

Thermally stimulated luminescence ( TL), current (TSC ) and exoelectronic emission ( TSEE ) of diVerent CVD diamond films grown on silicon substrates have been studied in order to obtain information on defects created during the growth and which induce levels within the gap. TL and TSC have been performed between 100 and 600 K, whereas TSEE has been measured from 300 to 700 K. Several TL peaks located between 275 and 540 K are observed, with diVerent relative intensities depending on the samples. A single TL peak located at about 515‐540 K is associated with a trap level 0.8 eV deep. This level gives rise to TSC, whereas the peak located at 275 K, and which may be attributed to the presence of boron, does not give a TSC signal. A TSEE peak located at 595 K is measured for all the samples but cannot be correlated with TL and TSC peaks. This is probably due to the presence of defects that are present only near the surface of the films.

Thermoluminescence of nickel-doped synthetic diamond crystals

An investigation of the thermoluninescent response of nickel-doped synthetic diamond samples is reported. The glow curve obtained after x-ray irradiation or ultraviolet light illumination exhibits a main peak around 500 K, and three weaker ones around 380, 645, and 715 K. Among these peaks, two are attributed to nickel-related centers at 1.4±0.1 and 2.4±0.2 eV, respectively. Spectral analysis of the main thermoluminescence peak indicated a broad band around 2.3 eV, similar to the photoluminescence spectrum. Linearity of the response versus x-ray doses, thermal, and optical fading properties are reported. The results indicated that nickel-doped synthetic diamond overcomes most of the disadvantages of other synthetic diamond crystals for ionizing radiation dosimetry applications.