Silicon nanowire possesses great potential as the material for renewable energy harvesting and conversion. The significantly reduced spectral reflectivity of silicon nanowire to visible light makes it even more attractive in solar energy applications. However, the benefit of its use for solar thermal energy harvesting remains to be investigated and has so far not been clearly reported. The purpose of this study is to provide practical information and insight into the performance of silicon nanowires in solar thermal energy conversion systems. Spectral hemispherical reflectivity and transmissivity of the black silicon nanowire array on silicon wafer substrate were measured. It was observed that the reflectivity is lower in the visible range but higher in the infrared range compared to the plain silicon wafer. A drying experiment and a theoretical calculation were carried out to directly evaluate the effects of the trade-off between scattering properties at different wavelengths. It is clearly seen that silicon nanowires can improve the solar thermal energy harnessing. The results showed that a 17.8 % increase in the harvest and utilization of solar thermal energy could be achieved using a silicon nanowire array on silicon substrate as compared to that obtained with a plain silicon wafer.

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Silicon Nanowires for Solar Thermal Energy Harvesting: an Experimental Evaluation on the Trade-off Effects of the Spectral Optical Properties

The recent discovery of ferroelectricity in thin hafnium oxide films has led to a resurgence of interest in ferroelectric memory devices. Although both experimental and theoretical studies on this new ferroelectric system have been undertaken, much remains to be unveiled regarding its domain landscape and switching kinetics. Here we demonstrate that the switching of single domains can be directly observed in ultrascaled ferroelectric field effect transistors. Using models of ferroelectric domain nucleation we explain the time, field and temperature dependence of polarization reversal. A simple stochastic model is proposed as well, relating nucleation processes to the observed statistical switching behavior. Our results suggest novel opportunities for hafnium oxide based ferroelectrics in nonvolatile memory devices.

Switching Kinetics in Nanoscale Hafnium Oxide Based Ferroelectric Field-Effect Transistors

The capacitor is a key element of electronic devices and is characterized by positive capacitance. However, a negative capacitance (NC) behaviour may occur in certain cases and implies a local voltage drop opposed to the overall applied bias. Therefore, a local NC response results in voltage enhancement across the rest of the circuit. Within a suitably designed heterostructure, ferroelectrics display such an NC effect, and various ferroelectric-based microelectronic and nanoelectronic devices have been developed, showing improved performance attributed to NC. However, the exact physical nature of the NC response and direct experimental evidence remain elusive or controversial thus far. In this Review, we discuss the physical mechanisms responsible for ferroelectric NC, tackling static and transient NC responses. We examine ferroelectric responses to voltage and charge, as well as ferroelectric switching, and discuss proof-of-concept experiments and possibilities for device implementation. Finally, we highlight different approaches for the optimization of the intrinsic NC response to maximize voltage amplification. Ferroelectrics-based materials can display a negative capacitance (NC) effect, providing an opportunity to implement NC in electronic circuits to improve their performance. In this Review, the authors discuss static and transient NC responses in ferroelectrics and highlight proof-of-concept experiments and possibilities for device implementation.

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Ferroelectric negative capacitance

Three-dimensional (3D) bioprinting, an additive manufacturing based technique of biomaterials fabrication, is an innovative and auspicious strategy in medical and pharmaceutical fields. The ability of producing regenerative tissues and organs has made this technology a pioneer to the creation of artificial multi-cellular tissues/organs. A broad variety of biomaterials is currently being utilized in 3D bioprinting as well as multiple techniques employed by researchers. In this review, we demonstrate the most common and novel biomaterials in 3D bioprinting technology further with introducing the related techniques that are commonly taking into account by researchers. In addition, an attempt has been accomplished to hand over the most relevant application of 3D bioprinting techniques such as tissue regeneration, cancer investigations, etc. by presenting the most important works. The main aim of this review paper is to emphasis on strengths and limitations of existence biomaterials and 3D bioprinting techniques in order to carry out a comparison through them.

An Overview on Materials and Techniques in 3D Bioprinting Toward Biomedical Application

Since their introduction in 2001, SiNW-based sensor devices have attracted considerable interest as a general platform for ultra-sensitive, electrical detection of biological and chemical species. Most studies focus on detecting, sensing and monitoring analytes in aqueous solution, but the number of studies on sensing gases and vapors using SiNW-based devices is increasing. This review gives an overview of selected research papers related to the application of electrical SiNW-based devices in the gas phase that have been reported over the past 10 years. Special attention is given to surface modification strategies and the sensing principles involved. In addition, future steps and technological challenges in this field are addressed.

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Silicon nanowire-based devices for gas-phase sensing.

In this paper, we propose and investigate the high-performance and low-power design space of nonhysteretic negative capacitance (NC) MOSFETs for the 14-nm node based on the calibrated simulations using an experimental gate-stack with PZT ferroelectric to obtain the NC effect. All necessary parameters are extracted by carefully characterizing experimentally fabricated ferroelectric capacitors, to ensure realistic simulation results. The ferroelectric thickness obtained by the proposed approach leads to the maximum enhancement in the nonhysteretic operation of NC transistors. We report a clear and significant double improvement in: 1) subthreshold swing and 2) gate overdrive, using the NC effect. Simulations using Silvaco TCAD coupled with a realistic Landau model of ferroelectrics demonstrates that a 14-nm node ultrathin body and box fully depleted silicon-on-insulator FET can operate at 0.26 V instead of 0.9 V gate voltage using the NC effect, with an average subthreshold swing of 55 mV/decade at room temperature. The double-gate structure is proposed to overcome the large mismatch between the ferroelectric and MOS capacitor to enhance the NC effect and reduce the ferroelectric’s optimized thickness. A 14-nm node double-gate negative capacitance FET can operate at 0.24 V gate voltage with an average subthreshold swing of 45 mV/decade.

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Double-Gate Negative-Capacitance MOSFET With PZT Gate-Stack on Ultra Thin Body SOI: An Experimentally Calibrated Simulation Study of Device Performance

This letter reports for the first time a full experimental study of performance boosting of tunnel FETs (TFETs) and MOSFETs by negative capacitance (NC) effect. We discuss the importance of capacitance matching between a ferroelectric NC and a device capacitance to achieve hysteretic and non-hysteretic characteristics. PZT ferroelectric capacitors are connected to the gate of three terminals TFETs and MOSFETs and partial or full matching NC conditions for amplification and stability are obtained. First, we demonstrate the characteristics of hysteretic and non-hysteretic NC-TFETs. The main performance boosting is obtained for the non-hysteretic NC-TFET, where the ON-current is increased by a factor of 500 times, transconductance is enhanced by three orders of magnitude, and the low slope region is extended. The boosting of performance is moderate in the hysteretic NC-TFET. Second, we investigate the impact of the same NC booster on MOSFETs. Subthreshold swing as steep as 4 mV/decade with a 1.5-V hysteresis is obtained on a commercial device fabricated in 28-nm CMOS technology. Moreover, we demonstrate a non-hysteretic NC-MOSFET with a full matching of capacitances and a reduced subthreshold swing down to 20 mV/decade.

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Negative Capacitance as Performance Booster for Tunnel FETs and MOSFETs: An Experimental Study

Nanowire tunnel field-effect transistors (TFETs) have been proposed as the most advanced one-dimensional (1D) devices that break the thermionic 60 mV/decade of the subthreshold swing (SS) of metal oxide semiconductor field-effect transistors (MOSFETs) by using quantum mechanical band-to-band tunneling and excellent electrostatic control. Meanwhile, negative capacitance (NC) of ferroelectrics has been proposed as a promising performance booster of MOSFETs to bypass the aforementioned fundamental limit by exploiting the differential amplification of the gate voltage under certain conditions. We combine these two principles into a single structure, a negative capacitance heterostructure TFET, and experimentally demonstrate a double beneficial effect: (i) a super-steep SS value down to 10 mV/decade and an extended low slope region that is due to the NC effect and, (ii) a remarkable off-current reduction that is experimentally observed and explained for the first time by the effect of the ferroelectric dipoles, which set the surface potential in a slightly negative value and further blocks the source tunneling current in the off-state. State-of-the-art InAs/InGaAsSb/GaSb nanowire TFETs are employed as the baseline transistor and PZT and silicon-doped HfO2 as ferroelectric materials.

Nanowire Tunnel FET with Simultaneously Reduced Subthermionic Subthreshold Swing and Off-Current due to Negative Capacitance and Voltage Pinning Effects.

The implementation and operation of the nonvolatile ferroelectric memory (NVM) tunnel field effect transistors with silicon-doped HfO2 is proposed and theoretically examined for the first time, showing that ferroelectric nonvolatile tunnel field effect transistor (Fe-TFET) can operate as ultra-low power nonvolatile memory even in aggressively scaled dimensions. A Fe-TFET analytical model is derived by combining the pseudo 2-D Poisson equation and Maxwell’s equation. The model describes the Fe-TFET behavior when a time-dependent voltage is applied to the device with hysteretic output characteristic due to the ferroelectric’s dipole switching. The theoretical results provide unique insights into how device geometry and ferroelectric properties affect the Fe-TFET transfer characteristic. The recently explored ferroelectric, silicon-doped HfO2 is employed as the gate ferroelectric. With the ability to engineer ferroelectricity in HfO2 thin films, a high-K dielectric well established in memory devices, the silicon-doped HfO2 opens a new route for improved manufacturability and scalability of future 1-T ferroelectric memories. In the current research, a Si:HfO2 based Fe-TFET with large memory window and low power dissipation is designed and simulated. Utilizing our presented model, the device characteristics of a Fe-TFET that takes full benefits from Si:HfO2 is compared with the same devices using well-known perovskite ferroelectrics. Finally, the Fe-TFET is compared with a conventional ferroelectric memory transistor highlighting the advantages of using tunneling memory devices.

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Modeling and simulation of low power ferroelectric non-volatile memory tunnel field effect transistors using silicon-doped hafnium oxide as gate dielectric

This work experimentally demonstrates that the negative capacitance effect can be used to significantly improve the key figures of merit of tunnel field effect transistor (FET) switches. In the proposed approach, a matching condition is fulfilled between a trained-polycrystalline PZT capacitor and the tunnel FET (TFET) gate capacitance fabricated on a strained silicon-nanowire technology. We report a non-hysteretic switch configuration by combining a homojunction TFET and a negative capacitance effect booster, suitable for logic applications, for which the on-current is increased by a factor of 100, the transconductance by 2 orders of magnitude, and the low swing region is extended. The operation of a hysteretic negative capacitance TFET, when the matching condition for the negative capacitance is fulfilled only in a limited region of operation, is also reported and discussed. In this late case, a limited improvement in the device performance is observed. Overall, the paper demonstrates the main beneficial effects of negative capacitance on TFETs are the overdrive and transconductance amplification, which exactly address the most limiting performances of current TFETs.

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Ali Saeidi

Papers

Double-Gate Negative-Capacitance MOSFET With PZT Gate-Stack on Ultra Thin Body SOI: An Experimentally Calibrated Simulation Study of Device Performance

Negative Capacitance as Performance Booster for Tunnel FETs and MOSFETs: An Experimental Study

Nanowire Tunnel FET with Simultaneously Reduced Subthermionic Subthreshold Swing and Off-Current due to Negative Capacitance and Voltage Pinning Effects.

Modeling and simulation of low power ferroelectric non-volatile memory tunnel field effect transistors using silicon-doped hafnium oxide as gate dielectric

Effect of hysteretic and non-hysteretic negative capacitance on tunnel FETs DC performance.