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91.
We fabricated a set of symmetric gate-recess devices with gate length of 70 nm.We kept the source-to-drain spacing(LSD)unchanged,and obtained a group of devices with gate-recess length(Lrecess)from 0.4μm to 0.8μm through process improvement.In order to suppress the influence of the kink effect,we have done SiNX passivation treatment.The maximum saturation current density(IDmax)and maximum transconductance(gm,max)increase as Lrecess decreases to 0.4μm.At this time,the device shows IDmax=749.6 mA/mm at VGS=0.2 V,VDS=1.5 V,and gm,max=1111 mS/mm at VGS=?0.35 V,VDS=1.5 V.Meanwhile,as Lrecess increases,it causes parasitic capacitance Cgd and gd to decrease,making fmax drastically increases.When Lrecess=0.8μm,the device shows fT=188 GHz and fmax=1112 GHz. 相似文献
92.
Heterogeneous integrated InP high electron mobility transistors(HEMTs)on quartz wafers are fabricated successfully by using a reverse-grown InP epitaxial structure and benzocyclobutene(BCB)bonding technology.The channel of the new device is In0.7Ga0.3As,and the gate length is 100 nm.A maximum extrinsic transconductance gm,max of 855.5 mS/mm and a maximum drain current of 536.5 mA/mm are obtained.The current gain cutoff frequency is as high as 262 GHz and the maximum oscillation frequency reaches 288 GHz.In addition,a small signal equivalent circuit model of heterogeneous integration of InP HEMTs on quartz wafer is built to characterize device performance. 相似文献
93.
A double-recessed offset gate process technology for InP-based high electron mobility transistors (HEMTs) has been developed in this paper. Single-recessed and double-recessed HEMTs with different gate offsets have been fabricated and characterized. Compared with single-recessed devices, the maximum drain-source current (ID,max) and maximum extrinsic transconductance (gm,max) of double-recessed devices decreased due to the increase in series resistances. However, in terms of RF performance, double-recessed HEMTs achieved higher maximum oscillation frequency (fMAX) by reducing drain output conductance (gds) and drain to gate capacitance (Cgd). In addition, further improvement of fMAX was observed by adjusting the gate offset of double-recessed devices. This can be explained by suppressing the ratio of Cgd to source to gate capacitance (Cgs) by extending drain-side recess length (Lrd). Compared with the single-recessed HEMTs, the fMAX of double-recessed offset gate HEMTs was increased by about 20%. 相似文献
94.
Circular dichroism spectra of α -lactose molecular measured by terahertz time-domain spectroscopy
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Researchers have long studied circular dichroism (CD) for its enormous prospects in life sciences. Many biomolecules have vibration modes in the terahertz region, and terahertz CD spectra are robust to detect biomolecular structures. However, few studies explore the terahertz CD spectra on even natural materials due to technical challenges in both fields. Here, we report a setup of home-built terahertz time-domain spectroscopy to measure the polarization states of terahertz waves. By carefully measuring the transmission Jones matrix, we obtain terahertz CD spectra of α -lactose tablets and D-glucose tablets. Our results show that the terahertz CD spectra are sensitive to vibrational motions in biochemical compounds, which will find wide applications in biosensing and biomedical diagnostics. 相似文献
95.
The E-field of pulse line ion accelerator (PLIA) is unique with high frequency (~MHz), large magnitude (~MV/m), and limited measuring space (~cm). The integrated optical E-field sensor (IOES) has remarkable advantages and has been used for PLIA E-field measurement. Firstly, the transfer function of the IOES has been calibrated to ensure measurement accuracy. The time-domain response illustrates that the sensor has a fast dynamic performance to effectively follow a 4 ns rising edge. Then, the E-field distribution along the axis and near the insulator surface of the PLIA was measured, showing that propagation of the E-field is almost lossless and the E-field near the insulation surface is about 1.1 times larger than that along the axis, which is in accordance with the simulation result. 相似文献
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面向连续体拓扑优化的多样性设计求解方法 总被引:1,自引:0,他引:1
拓扑优化可以在概念设计阶段为工业产品结构的概念设计提供新颖的设计思路. 传统的连续体结构拓扑优化方法通常只能获得一个优化的拓扑构型,但在实际工程应用中,这个构型在后续设计阶段可能会由于分析模型逐步细化、设计要求的进一步明确而无法满足改变后的设计目标和约束. 针对此问题,提出了多样性设计求解方法(multiple designs approach,MDA),使得能够在优化过程中获得若干个多样性设计,以此减少在可能在设计初期由于信息不完整所带来的风险. 给出MDA 基本的优化列式,将目标函数定义为多个设计构型的目标性能加权之和,并通过加入对多样性度量的约束条件,在优化过程中驱动各个设计产生几何构型上差异. 给出了一种具体的多样性度量方法,并对其物理意义和特征进行描述和讨论. 以基于变密度法的最小柔顺性问题作为优化算例,给出了具体的优化列式及敏度推导. 在算例中,研究了目标函数和约束中不同参数对结果的影响,并对目标函数之外的其他潜在结构性能进行了讨论和比较. 结果表明,通过MDA 能够有效地给出一批多样性设计构型,为后续的精细化设计提供多种设计方案和思路. 相似文献
100.
以咪唑和吡啶作为阳离子基体, 设计合成了3种具有烷基膦酸功能基团的功能型离子液体, 利用傅里叶变换红外(FTIR)光谱、 核磁共振氢谱(1H NMR)和元素分析对离子液体的结构进行了确认, 测定了离子液体的相转变温度、 热稳定性、 密度和黏度等物理性能, 并对硝酸介质中萃取铀酰离子进行了研究. 结果表明, 所制备的功能离子液体可同时作为稀释剂和萃取剂, 在室温环境下实现对铀(Ⅵ)的萃取, 萃取率可达到90%以上. 相似文献