다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

Two-dimensional crystals have emerged as a class of materials that may impact future electronic technologies. Experimentally identifying and characterizing new functional two-dimensional materials is challenging, but also potentially rewarding. Here, we fabricate field-effect transistors based on few-layer black phosphorus crystals with thickness down to a few nanometres. Reliable transistor performance is achieved at room temperature in samples thinner than 7.5 nm, with drain current modulation on the order of 10(5) and well-developed current saturation in the I-V characteristics. The charge-carrier mobility is found to be thickness-dependent, with the highest values up to ∼ 1,000 cm(2) V(-1) s(-1) obtained for a thickness of ∼ 10 nm. Our results demonstrate the potential of black phosphorus thin crystals as a new two-dimensional material for applications in nanoelectronic devices.

Black phosphorus field-effect transistors

We introduce the 2D counterpart of layered black phosphorus, which we call phosphorene, as an unexplored p-type semiconducting material. Same as graphene and MoS2, single-layer phosphorene is flexible and can be mechanically exfoliated. We find phosphorene to be stable and, unlike graphene, to have an inherent, direct, and appreciable band gap. Our ab initio calculations indicate that the band gap is direct, depends on the number of layers and the in-layer strain, and is significantly larger than the bulk value of 0.31–0.36 eV. The observed photoluminescence peak of single-layer phosphorene in the visible optical range confirms that the band gap is larger than that of the bulk system. Our transport studies indicate a hole mobility that reflects the structural anisotropy of phosphorene and complements n-type MoS2. At room temperature, our few-layer phosphorene field-effect transistors with 1.0 μm channel length display a high on-current of 194 mA/mm, a high hole field-effect mobility of 286 cm2/V·s, and an...

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Phosphorene: An Unexplored 2D Semiconductor with a High Hole Mobility

The polarization switching speed of ferroelectric (FE) hafnium zirconium oxide (HZO) is studied with the device size down to sub-μm in lateral dimension. Ultrafast measurement of transient switching current on metal-ferroelectric-metal (MFM) device with a crossbar array or a single crossbar structure is performed to analyze the switching dynamics. A record fast polarization switching of 360 ps is achieved for 15 nm thick HZO with 0.1 μm2 crossbar array device structure. The observed record switching speed is found to be limited by domain wall propagation speed in the nucleation limited switching process. It is further verified after significant reduction of RC delay of the devices and the implementation of crossbar array structure.

Record Fast Polarization Switching Observed in Ferroelectric Hafnium Oxide Crossbar Arrays

In this paper, we report a novel chemical doping technique to reduce the contact resistance (Rc) of transition metal dichalcogenides (TMDs) - eliminating two major roadblocks (namely, doping and high Rc) towards demonstration of high-performance TMDs field-effect transistors (FETs). By using 1,2 dichloroethane (DCE) as the doping reagent, we demonstrate an active n-type doping density > 2*1019 cm-3 in a few-layer MoS2 film. This enabled us to reduce the Rc value to a record low number of 0.5 kohm*um, which is ~10x lower than the control sample without doping. The corresponding specific contact resistivity (pc) is found to decrease by two orders of magnitude. With such low Rc, we demonstrate 100 nm channel length (Lch) MoS2 FET with a drain current (Ids) of 460 uA/um at Vds = 1.6 V, which is twice the best value reported so far on MoS2 FETs.

High-Performance MoS2 Field-Effect Transistors Enabled by Chloride Doping: Record Low Contact Resistance (0.5 kohm*um) and Record High Drain Current (460 uA/um)

We have demonstrated well-behaved accumulation-mode all oxide NMOSFETs with amorphous atomic-layer-deposited (ALD) LaAlO 3 gate dielectric stacks on crystalline SrTiO 3 substrates. A maximum drain current exceeding 10 mA/mm has been obtained on a 3.75µm-gate-length device, proving a very conductive channel can be formed at the oxide-oxide interface. Four different gate dielectric stacks, which are Lafirst cycle LaAlO 3 , Al-first cycle LaAlO 3 , LaAlO 3 with 1.5 nm La 2 O 3 interfacial layer, and LaAlO 3 with 1.8 nm Al 2 O 3 interfacial layer, have been deposited on SrTiO 3 substrates to systematically study their effects on the conductivity at the different oxide-oxide interfaces. The experimental results show that a La-initiated interfacial layer is preferable to form a more conducting channel at the LaAlO 3 /SrTiO 3 interface. Low temperature characteristics have also been utilized to provide an in-depth understanding of the channel formation at the oxide-oxide interface. The availability of the MBE technology to epitaxially grow SrTiO 3 on Si substrate provides the pathway to integrate ALD LaAlO 3 /SrTiO 3 devices on Si platform.

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Atomic-layer-deposited LaAlO 3 /SrTiO 3 all oxide field-effect transistors

We investigate the polarization switching mechanism in ferroelectric-dielectric (FE-DE) stacks and its dependence on the dielectric thickness (TDE). We fabricate HZO-Al2O3 (FE-DE) stack and experimentally demonstrate a decrease in remnant polarization and an increase in coercive voltage of the FE-DE stack with an increase in TDE. Using phase-field simulations, we show that an increase in TDE results in a larger number of reverse domains in the FE layer to suppress the depolarization field, which leads to a decrease in remanent polarization and an increase in coercive voltage. Further, the applied voltage-driven polarization switching suggests domain-nucleation dominant characteristics for low TDE, and domain-wall motion-induced behavior for higher TDE. In addition, we show that the hysteretic charge-voltage characteristics of the FE layer in the FE-DE stack exhibit a negative slope region due to the multi-domain polarization switching in the FE layer. Based on our analysis, the trends in charge-voltage characteristics of the FE-DE stack with respect to different TDE (which are out of the scope of single-domain models) can be described well with multi-domain polarization switching mechanisms.

Multi-domain Polarization Switching in Hf0.5Zr0.5O2-Dielectric Stack: The Role of Dielectric Thickness.

In this work, ultrafast pulses with pulse widths ranging from 100 ps to seconds were applied on the gate of Ge ferroelectric (FE) nanowire (NW) pFETs with FE Hf 0.5 Zr 0.5 O 2 (HZO) gate dielectric exhibiting steep subthreshold slope (SS) below 60 mV/dec bi-directionally. With applied gate bias pulses (V G = -1 to -10 V), high-mobility Ge drain current was monitored as a test vehicle to capture the polarization switching of HZO. It was found that HZO could switch its polarization directly by a single pulse with the minimum pulse width of 3.6 ns. The polarization switching triggered by pulse train with pulse width as short as 100 ps was demonstrated for the first time.

First Direct Experimental Studies of Hf 0.5 Zr 0.5 O 2 Ferroelectric Polarization Switching Down to 100-picosecond in Sub-60mV/dec Germanium Ferroelectric Nanowire FETs

Peide D. Ye

Papers

Record Fast Polarization Switching Observed in Ferroelectric Hafnium Oxide Crossbar Arrays

High-Performance MoS2 Field-Effect Transistors Enabled by Chloride Doping: Record Low Contact Resistance (0.5 kohm*um) and Record High Drain Current (460 uA/um)

Atomic-layer-deposited LaAlO 3 /SrTiO 3 all oxide field-effect transistors

Multi-domain Polarization Switching in Hf0.5Zr0.5O2-Dielectric Stack: The Role of Dielectric Thickness.

First Direct Experimental Studies of Hf 0.5 Zr 0.5 O 2 Ferroelectric Polarization Switching Down to 100-picosecond in Sub-60mV/dec Germanium Ferroelectric Nanowire FETs