Numerical investigation on the convergence of self-consistent Schrödinger-Poisson equations in semiconductor device transport simulation.

Semiconductor devices at the nanoscale with low-dimensional materials as channels exhibit quantum transport characteristics, thereby their electrical simulation relies on the self-consistent solution of the Schrödinger-Poisson equations. While the non-equilibrium Green's function (NEGF) method is widely used for solving this quantum many-body problem, its high computational cost and convergence challenges with the Poisson equation significantly limit its applicability. In this study, we investigate the stability of the NEGF method coupled with various forms of the Poisson equation, encompassing linear, analytical nonlinear, and numerical nonlinear forms Our focus lies on simulating carbon nanotube field-effect transistors (CNTFETs) under two distinct doping scenarios: electrostatic doping and ion implantation doping. The numerical experiments reveal that nonlinear formulas outperform linear counterpart. The numerical one demonstrates superior stability, particularly evident under high bias and ion implantation doping conditions. Additionally, we investigate different approaches for presolving potential, leveraging solutions from the Laplace equation and a piecewise guessing method tailored to each doping mode. These methods effectively reduce the number of iterations required for convergence.

Ultra-Strong Comprehensive Radiation Effect Tolerance in Carbon Nanotube Electronics.

Carbon nanotube (CNT) field-effect transistors (FETs) have been considered ideal building blocks for radiation-hard integrated circuits (ICs), the demand for which is exponentially growing, especially in outer space exploration and the nuclear industry. Many studies on the radiation tolerance of CNT-based electronics have focused on the total ionizing dose (TID) effect, while few works have considered the single event effects (SEEs) and displacement damage (DD) effect, which are more difficult to measure but may be more important in practical applications. Measurements of the SEEs and DD effect of CNT FETs and ICs are first executed and then presented a comprehensive radiation effect analysis of CNT electronics. The CNT ICs without special irradiation reinforcement technology exhibit a comprehensive radiation tolerance, including a 1 × 104 MeVcm2 mg-1 level of the laser-equivalent threshold linear energy transfer (LET) for SEEs, 2.8 × 1013 MeV g-1 for DD and 2 Mrad (Si) for TID, which are at least four times higher than those in conventional radiation-hardened ICs. The ultrahigh intrinsic comprehensive radiation tolerance will promote the applications of CNT ICs in high-energy solar and cosmic radiation environments.

A FIN-LDMOS with Bulk Electron Accumulation Effect.

A thin Silicon-On-Insulator (SOI) LDMOS with ultralow Specific On-Resistance (Ron,sp) is proposed, and the physical mechanism is investigated by Sentaurus. It features a FIN gate and an extended superjunction trench gate to obtain a Bulk Electron Accumulation (BEA) effect. The BEA consists of two p-regions and two integrated back-to-back diodes, then the gate potential VGS is extended through the whole p-region. Additionally, the gate oxide Woxide is inserted between the extended superjunction trench gate and N-drift. In the on-state, the 3D electron channel is produced at the P-well by the FIN gate, and the high-density electron accumulation layer formed in the drift region surface provides an extremely low-resistance current path, which dramatically decreases the Ron,sp and eases the dependence of Ron,sp on the drift doping concentration (Ndrift). In the off-state, the two p-regions and N-drift deplete from each other through the gate oxide Woxide like the conventional SJ. Meanwhile, the Extended Drain (ED) increases the interface charge and reduces the Ron,sp. The 3D simulation results show that the BV and Ron,sp are 314 V and 1.84 mΩ∙cm-2, respectively. Consequently, the FOM is high, reaching up to 53.49 MW/cm2, which breaks through the silicon limit of the RESURF.

Heavy Ion Displacement Damage Effect in Carbon Nanotube Field Effect Transistors.

Recent advances in carbon nanotube (CNT)-based integrated circuits have shown their potential in deep space exploration. In this work, the mechanism governing the heavy-ion-induced displacement damage (DD) effect in semiconducting single-walled CNT field effect transistors (FETs), which is one of the factors limiting device robustness in space, was first and thoroughly investigated. CNT FETs irradiated by a Xe ion fluence of 1012 ions/cm2 can maintain a high on/off current ratio, while transistors' performance failure is observed as the ion fluence increased to 5 × 1012 ions/cm2. Controllable experiments combined with numerical simulations revealed that the degradation mechanism changed as the nonionizing radiation energy built up. The trap generation in the gate dielectric, instead of the CNT channel, was identified as the dominating factor for the high-energy-radiation-induced device failure. Therefore, CNT FETs exhibited a >10× higher DD tolerance than that of Si devices, which was limited by the channel damage under irradiation. More importantly, the distinct failure mechanism determined that CNT FETs can maintain a high DD tolerance of 2.8 × 1013 MeV/g as the technology node scales down to 45 nm node, suggesting the potential of CNT-based VLSI for high-performance and high-robustness space applications.

Radiation damage and abnormal photoluminescence enhancement of multilayer MoS2under neutron irradiation.

In this work, neutron irradiation effects on the optical property of multilayer MoS2have been investigated in depth. Our results display that the intensity of the photoluminescence (PL) spectra of MoS2flakes tends to slightly decrease after exposed to neutron irradiation with low fluence of 4.0 × 108n/cm2. An unexpected improvement of PL intensity, however, is observed when the irradiation fluence accumulates to 3.2 × 109n/cm2. Combined with the experimental results and first-principles calculations, neutron irradiation damage effects of multilayer MoS2are analyzed deeply. Sulfur vacancy (VS) is found to be responsible for the attenuation of the PL intensity as a major defect. In addition, our results reveal that the adsorbed hydroxyl groups (OH) and oxygen atoms (O) on the surface of MoS2flakes not only promote the transition from trion excitons to neutral excitons, but also repair theVSin MoS2, both of which contribute to the enhancement of luminescence properties. The detailed evolution process of irradiation-induced defects is discussed to reveal the microscopic mechanism of the significantly difference in luminescence intensity of MoS2under different irradiation stages. This work has great significance for evaluating the neutron radiation hardness of multilayer MoS2, which is helpful to enrich the fundamental research on neutron irradiation effects.

Antitumor activity of the procyanidins from Pinus koraiensis bark on mice bearing U14 cervical cancer.

Pinus koraiensis Bark Procyanidins Extract (PKBPE) has been used in traditional Chinese medicine for thousands of years. In this study, we determined PKBPE effect on tumor weight, SOD (superoxidate dismutase) activity, the content of MDA (malondialdehyde) through colorimetric analysis antigenic, and expression of Ki-67, p53 and Bcl-2 on mice bearing U14 cervical cancer. Treatment with PKBPE (158 and 250 mg/kg body weight, p.o.) could inhibit U14 cervical carcinoma growth up to 47.68 and 58.94%. In addition, PKBPE enhance the activity of SOD (p<0.01) and decrease MDA content. Furthermore, we also observed that PKBPE treatment significantly inhibited the expression of Ki-67, mutant p53 and Bcl-2 protein (p<0.01). The results suggested that PKBPE showed antitumor activities on U14 cervical carcinoma mice. The mechanism of PKBPE antitumor activity might be associated with free radical production inhibition and regulation of the expression of Ki-67, mutant p53 and Bcl-2 protein.