Recharging process of commercial floating-gate MOS transistor in dosimetry application

We investigated the recharging process of commercial floating gate device (EPAD) during the six different dose rates and ten irradiation cycles with the highest dose rate. Dose rate dependence of the floating gate dosimeter was observed from 1 Gy/h to 26 Gy/h (H2O). There is no change of the dosimetric characteristic with a constant dose rate of 26 Gy/h for ten cycles. The absorbed dose does not affect the drift of the threshold voltage readings after the irradiation steps. The reprogramming characteristic is not degrading with the absorbed dose for the ten irradiation cycles, giving the promising potential in the application for dosimetric purposes

Commercial P-Channel Power VDMOSFET as X-ray Dosimeter

The possibility of using commercial p-channel power vertical double-diffused metal-oxide-semiconductor field-effect transistors (VDMOSFETs) as X-ray sensors is investigated in this case study. In this aspect, the dependence of sensitivity on both the gate voltage and the mean energy for three X-ray beams is examined. The eight gate voltages from 0 to 21 V are applied, and the dependence of the sensitivity on the gate voltage is well fitted using the proposed equation. Regarding X-ray energy, the sensitivity first increases and then decreases as a consequence of the behavior of the mass energy-absorption coefficients and is the largest for RQR8 beam. As the mass energy-absorption coefficients of SiO2 are not found in the literature, the mass energy-absorption coefficients of silicon are used. The behavior of irradiated transistors during annealing at room temperature without gate polarization is also considered

PS-BBICS: Pulse stretching bulk built-in current sensor for on-chip measurement of single event transients

The bulk built-in current sensor (BBICS) is a cost-effective solution for detection of energetic particle strikes in integrated circuits. With an appropriate number of BBICSs distributed across the chip, the soft error locations can be identified, and the dynamic fault-tolerant mechanisms can be activated locally to correct the soft errors in the affected logic. In this work, we introduce a pulse stretching BBICS (PS-BBICS) constructed by connecting a standard BBICS and a custom-designed pulse stretching cell. The aim of PS-BBICS is to enable the on-chip measurement of the single event transient (SET) pulse width, allowing to detect the linear energy transfer (LET) of incident particles, and thus assess more accurately the radiation conditions. Based on Spectre simulations, we have shown that for the LET from 1 to 100 MeV cm2 mg−1, the SET pulse width detected by PS-BBICS varies by 620–800 ps. The threshold LET of PS-BBICS increases linearly with the number of monitored inverters, and it is around 1.7 MeV cm2 mg−1 for ten monitored inverters. On the other hand, the SET pulse width is independent of the number of monitored inverters for LET > 4 MeV cm2 mg−1. It was shown that supply voltage, temperature and process variations have strong impact on the response of PS-BBICS

Spherical aromaticity of Jahn–Teller active fullerene ions

Density functional theory was applied to compute the nucleus-independent chemical shifts of fullerene (C₆₀), the fullerene ion C₆₀ ¹⁰⁺, and the Jahn–Teller active fullerene anion C₆₀ ⁻ and cation C₆₀ ⁺. Positioning a ³He nucleus inside the cage of each of these fullerene species facilitates investigations of the substantial differences among them, ³He NMR chemical shifts can provide important data on the aromatic behavior of these molecular cages. Thus, we also calculated the NMR chemical shift of a ³He atom positioned at the center of each fullerene species investigated (C₆₀, C₆₀ ¹⁰⁺, C₆₀ ⁻, and C₆₀ ⁺). The data obtained revealed significant differences in the aromatic behavior of the C₆₀ (moderately aromatic) and C₆₀ ¹⁰⁺ (highly aromatic) species. The values of the nucleus-independent chemical shift parameters were also scanned along the intrinsic distortion path for the C₆₀ ⁻ and C₆₀ ⁺ species. In both cases, antiaromatic character decreases with increasing deviation from high-symmetry structures to low-symmetry global minimum points, resulting in the antiaromatic C₆₀ ⁻ and weakly aromatic C₆₀ ⁺

Sensitivity and fading of irradiated RADFETs with different gate voltages

The radiation-sensitive field-effect transistors (RADFETs) with an oxide thickness of 400 nm are irradiated with gate voltages of 2, 4 and 6 V, and without gate voltage. A detailed analysis of the mechanisms responsible for the creation of traps during irradiation is performed. The creation of the traps in the oxide, near and at the silicon/silicon-dioxide (Si/SiO2) interface during irradiation is modelled very well. This modelling can also be used for other MOS transistors containing SiO2. The behaviour of radiation traps during postirradiation annealing is analysed, and the corresponding functions for their modelling are obtained. The switching traps (STs) do not have significant influence on threshold voltage shift, and two radiation-induced trap types fit the fixed traps (FTs) very well. The fading does not depend on the positive gate voltage applied during irradiation, but it is twice lower in case there is no gate voltage. A new dosimetric parameter, called the Golden Ratio (GR), is proposed, which represents the ratio between the threshold voltage shift after irradiation and fading after spontaneous annealing. This parameter can be useful for comparing MOS dosimeters