Nanoelectronics Devices: Design, Materials, and Applications (Part I)

Nanotechnology is concerned with creating and applying materials with nanoscale dimensions in various facets of life. Additional features have been introduced to the world of electronics due to advancements in nanotechnology. The development and cost-effective manufacturing of cutting-edge components that function quickly, use less power and can be packed at much higher densities is made possible by nanotechnology's new and unique features. There is a revolution in biotechnology, food, the military, and medicine using nanotechnology.

This chapter focuses on molecular tunnel junctions (MTJ), the basic building block of molecular electronics (ME), which consist of either a single molecule or an ensemble of molecules in the form of a self-assembled monolayer (SAM) sandwiched between two electrodes. MTJs based on SAMs find practical applications such as diode rectifiers, switches, and molecular memory devices. The predominant charge transport mechanism in two-terminal junctions is tunneling; therefore, perturbances in the bond length scale will translate into nonlinear electrical responses, allowing MTJ to induce and control electronic activity on nanoscopic length scales with various inputs. For this reason, the subject is now progressing to devices based on finite ensembles of molecules, and many studies are underway to develop devices that can augment and complement traditional semiconductor-based electronics. SAM-based tunnel junctions are like single molecular junctions, demonstrating effects like quantized conductance, tunneling, hopping, and rectification; they also possess a unique set of properties. In addition, several new problems that need to be addressed arise from the unique characteristics of SAM-based junctions. General aspects of the two terminal molecular junctions, roles of the electrode, molecule, and molecule electrode interfaces, and how to differentiate the components of a molecular junction using impedance spectroscopy are discussed in this chapter. Different testbeds to measure the charge transport in SAM-based tunnel junctions are discussed, and a comparison of the reported charge transport data on alkanethiolate SAMs is presented. Finally, the molecular rectifiers are briefly discussed.

The shrinking of the device parameters' dimensions could be a solution for improving the performance and high transistor density of traditional MOSFETs. However, the short-channel effects could create a problem in the performance of the device. This chapter examines and performs comprehensive simulations of the standard junctionless double-gate transistor. In this research, silicon thickness and work function engineering are used to better understand the junctionless transistor's operation. As silicon thickness increases, the junctionless double-gate FET's performance begins to decline. Additionally, the typical double-gate junctionless FET is modelled, and the change in silicon thickness, work function, gate dielectric, and doping concentration is studied. The findings of the analysis and simulation are found to be quite similar. As a result, the device is referred to as a rectangular core-shell double-gate junctionless transistor because of the core being sandwiched between the two shells of the device (RCS-DGJLT). While the core-shell is doped with acceptor impurities in an n-type RCS-DGJLT, donor impurities are used in the shells. The device performance parameters have been improved such that IOFF of order ~10-14A, ION ~10-5A, ION/IOFF ~109 , SS nearly 68.9mV/decade, DIBL nearly 52.6mV/V are obtained at a total silicon thickness of 12nm and channel length of 20nm. The effect of channel length variation on RCS-DGJLT is also studied. RCS-DGJLT is found to have better performance than conventional DGJLT.

Scaling down the metal-oxide- semiconductor (MOS) technology in the nanometer regime has been performed to achieve high device performance, but reliability and power consumption are the main concern for the semiconductor industry. In the past few years, area-scaled tunneling field-effect transistors (TFETs) have been researched aggressively to enhance the tunneling cross-sectional area of devices. Although the area-scaled Tfet increases the device footprint for the same channel length when compared to the conventional TFET structure. This problem can be resolved by considering a nonplanar device structure. The LTFET structure enhances the on-state current and reduces the device footprint area. In the present study, a detailed analysis of the electrical characteristics of L-shaped TFET (LTFET) through 2-D TCAD simulations is presented. The proposed hetero-junction LTFET with 20 nm gate length exhibits a high ION of 1.08×10-4 A/µm, low IOFF of 1.57×10-14 A/µm, high ION/IOFF of 1010, and steep sub-threshold slope (SS) of 25 mV/dec at room temperature. The analysis has been carried out to encounter the effect of Gaussian traps at the channel–gate oxide interface at a wide range of temperatures from 250 K to 350 K. An extensive study on the influence of temperature variations on various DC analysis, AC analysis, linearity analysis, and electrical noise analysis has been carried out. The study reveals that the electrical parameters like ION, IOFF, and SS, on which all figures of merit (FOMs) of the device depend, show a small variation with increasing temperature. The drain current noise spectral density (SID) changes from 2.12×10-26 A 2 /Hz to 2.42×10-20 A2 /Hz, and voltage noise spectral density (SVG) changes from 1.79×10-11 V2 /Hz to 1.97×10-5 V2 /Hz on increasing temperature from 250 K to 350 K. The change in temperature does not impact the on-current of the device, while a small variation in the off-current occurs. The various FOMs of the device also show small variations in the results with increasing temperature. The only unfavorable factor where the evident change in the results has been observed is the electrical noise characteristics of the device. The reliability analysis clarifies that the proposed LTFET device performs well at a wide range of temperatures and can be well-suited for low-power applications.

With the rapid scaling of transistors in the nanometer regime, various shortchannel effects emerge in short-channel devices; researchers are looking for an alternative device to replace complementary MOSFET (CMOS) in circuit applications. TFETs are considered to be a good replacement for the conventional MOSFET in the upcoming technologies. The methods used for making ION higher also impacts the IOFF current. So, the overall current ratio remains unaltered. To overcome this problem, a technique has been developed and adopted in this work that not only improves the current ratio but also makes the subthreshold swing steeper. The major improvements are the reduction of short channel effects, enhancing current ratio reducing dynamic power consumption. Negative capacitance being a new phenomenon, helps in providing improvised results. The device optimized in this work has given values of Subthreshold swing as 53.75 mV/decade, ION and IOFF as 4.295*10-5 A/μm, 6.01*10-15 A/μm, respectively. DIBL calculated for conventional NCTFET is 61.2 mV/V, and for proposed NCTFET is 31.92 mV/V. So DIBL improvement of 52.2% has been achieved.

In this chapter, the author demonstrates a triple metal double gate TFET with a uniformly doped source pocket (TMG-SP-DG-TFET) to investigate the impact of triple metal length variation (Length of an electrode implanted above the oxide region) on the device performance. When the electrode length near the drain and source region varies, the electrostatic potential and electric field near the source-channel (SCi) and drain-channel interface (DCi) may vary accordingly. Due to these deviations, the tunneling improves or reduces for a moderately doped drain and a highly doped source region. Therefore, the ION (ON-state current) has shown significant functionalities with electrode length variation. This extensive study was carried out for the investigation of analog parameters, including EBD (ON/OFF state), Efield, Potential, gm (Trans-conductance), Cgs and Cgd (Gate-to-source and Gate-to-Drain capacitance), Maximum cut-off frequency (ft ), Gain bandwidth product (GBP), Transit Time (τ), with Linearity figure of merit that includes, gm2, gm3, VIP2 , VIP3 , IIP3 , IMD3 , and 1dB compression point. This comprehensive study shows that varying the length of the metal electrode with a fixed doping level of the source pocket will improve the overall performance of TMG-SP-DG-TFET.

 Implementing gas sensors incorporating nanoelectronic devices to detect pollution and improve the safety control of industrial, medical, and domestic sectors has opened up a novel world with immense interest. As a promising renewable energy carrier and a potential replacement for fossil fuels, there is the paramount importance of hydrogen gas storage at extensive facilities worldwide. The sustainable production of hydrogen is increasing owing to its enormous energy per mass of any fuel. Nevertheless, due to its extreme flammability, simple and highly accurate sensors with promising sensing materials are required to detect the slightest traces of timely leak detection for developing a hydrogen economy. Various hydrogen detectors already exist, but expensive cost, large size, sluggish response, and high temperature limit their potential for widespread applications. The integral objective of the present chapter is to focus on a systematic investigation of Pd-Ti/ZnO Schottky TFT-based room temperature hydrogen sensors excluding any heating element. With high chemical and thermal stability, ZnO is a promising candidate for sensors in a hazardous atmosphere. The developed sensor exhibited room temperature detection with a maximum response of 33.8% to 4500 ppm H2 in dry air. The selectivity analysis toward H2 in the presence of other reducing and oxidizing gas species has also been investigated to ensure the real-time applicability of the sensor. Reliable operation of the sensor in a wide range of 500 ppm to 4500 ppm H2 has been confirmed from the linear behavior of the sensor. The hydrogen sensing mechanism of the proposed sensor in terms of Schottky barrier height reduction at the interface of Pd-Ti/ZnO has also been detailed in this chapter. Room temperature detection of the hydrogen sensor presented here competes favorably with the existing studies. This study can be extended in exploring new routes to realize hydrogen sensing applications at room temperature for commercialization with precise control over film thickness and target gas concentrations. 

A review of the electrical and physical characteristics of FinFETs is presented here. This work focuses on the latest structures of FinFET according to its classifications and three-dimensional schematics. Through studying the output I-V characteristics, the transfer characteristics, and the subthreshold current in the FinFET channel, the electrical characteristics of FinFETs have been analyzed. Considerations were made of coulomb, phonon, and surface roughness scattering to examine effective charge carrier mobility in the FinFET channel. Lastly, in this chapter, the impact of the Fin layer shape on device performance is studied.

This chapter presents a vertical tunnel FET (VTFET) designed for light sensing application to use in medical diagnosis and treatment, tracking of targets, analysis of the chemical composition, surveillance cameras, etc. Various aspects related to this optimized VTFET photosensor are analyzed to benchmark its performance among those available in the literature. A brief discussion on the conventional TFET geometry is presented to give a better understanding of the advantages of its working methodologies. The concept of sensing using optically gated VTFET is studied with a remarkable focus on design perspective and detection principle. The modified TFET geometry has a photosensitive gate called an optically gated VTFET to use in near-infrared sensing applications. The design approach based on Synopsys Technology Computer-Aided Design (TCAD), along with suitable physics-based models of simulation, is introduced in this chapter. A wavelength range of 0.7µm to 1µm is considered in the simulation process. Analyses of different sensing parameters, such as sensitivity, responsivity, etc., at low intensity of illumination, are brought to light with the main focus on the viability of the proposed sensor to be a superior one. Through such analysis, this chapter presents a low-power, highly sensitive, cost-effective, faster response time photodetector that may be applicable for next-generation photosensors.

This chapter focuses on the evolution of Self-powered Photodetectors, from single nanobelt to highly sophisticated Pyro-phototronic effect-assisted devices. The essentials of the self-powered photodetector, from material characterization to device engineering mechanism, are discussed in detail, such as Pyro-phototronic enriched devices. This study provides a state-of-the-art research trend of the Pyro-phototronic enriched self-powered photodetectors. Finally, a summary of various device structures with their figures of merit and conclusions, along with the research gap, is presented. This review focuses on providing valuable insights into improving self-powered photodetectors.

Owing to the strong interest in sustainable and renewable energy in the past recent years, the solar cell industry has grown vastly. Conventional solar cells are simply not efficient enough and are expensive to manufacture for large-scale electricity generation. There are potential and sustainable advancements in nanotechnology that have opened the door to the production of efficient nanostructured optoelectronics. Nanotechnology has depicted tremendous breakthroughs in the field of solar technology. Nanomaterials and quantum dots (QDs) have proved to be potential candidates in the field of solar cells. Nanotechnology is able to enhance the efficiency of solar cells, meanwhile helping in the reduction of manufacturing costs. Photovoltaics (PVs) based on inorganic, organic, and polymer materials are designed and synthesized with the aim of reducing cost per watt, even if it declines reliability and conversion efficiency. Such PVs absorb sunlight more efficiently with wider absorption spectra which also show better conversion of power to efficiency. Herein, we have highlighted nanoparticles based on inorganic, organic, or graphene-based functional materials, which exhibit enhanced physicochemical properties along with excellent surface-to area ratio to be used as nanostructured thin layers coated with solar cell panels. Utilizing nanotechnology in developing low-cost and efficient solar cells would help to preserve the environment.

This chapter provides insights about the Perovskite type of Solar Cell (PVSC) that can be utilized as a probable substitute for existing solar panels. Pros of reduced lead participation in chemical structure and better end-of-life supports have boosted research explorations. Combinatorial-based explorations in perovskites have created a collection of various chemical designs with unique properties and improved functionalities. Investigations in terms of catalytic nature, environment adaptability, and spintronic properties provide vivid structural arrangements. But still, constraints based on application-specific composition, raw material utilization, problems of stability issues, and the reduction in lead content are the objectives yet to be achieved at the commercial level. Interlinking of chemical structural, the nature of multiple layers created for building the material can be improvised with nanomaterials integration as detailed in the chapter. Comparative lab results analysis and efforts over raised stability and reduced lead content are taken into the study to present PVSC as upcoming commercialized products. Moreover, future scope briefs about existing nanomaterials composites with improvised electron and hole transport layers. Also, findings related to back electrode-based placement to achieve better efficiency and stability are submitted to reveal suitable obtains of the experiments covered in the study.

The rapid advancement in technologies and a surge in the global population with the swift Industrialization led to severe challenges in fulfilling global energy demand. In the last few decades, researchers have been fiercely looking for the development of sustainable energy sources to achieve the goal of carbon neutrality and green energy generation. Among the various approaches to green energy generation, solar and thermoelectric conversions are the most lucrative. In both solar and thermoelectric means of energy generation, direct conversion of sunlight and temperature gradient into useful electricity is possible without involving heavy mechanical instruments or hazardous gases, which makes it more robust and prone to environmental degradation. Despite the several advantages, solar cell and thermoelectric power generation are still suffering from the challenges of low power conversion efficiency and long-term stability. In 2004, graphene was discovered, ushering in a new age of 2D materials research. The family of two-dimensional materials has been intensively explored in recent years as a reliable and effective alternative material for numerous applications, including thermoelectric power conversion and solar cell components, due to their distinctive material features. Geometric symmetry has a big impact on the electrical characteristics of 2D layered nanomaterials because they are highly sensitive to structural perfection. Numerous nanomaterials have recently been exfoliated, and computational predictions have been made for their potential applications in solar cells and thermoelectric generators. In this chapter, we will basically discuss the insight of emerging nano-materials, their key properties, and applications for designing renewable energy devices. The ultra-thin layer-based solar cells and nano-materials-based thermoelectric generators will also be introduced as a section of the chapter. The concept of emerging classes of nano-materials such as Janus monolayers, van-der Waals structures, and group-IV chalcogenides further piques the interest of the reader to learn about the different perspectives of nano-materials and nano-devices. 

Decaying sources of non-renewable energy (fossil fuel) turned the research focus to other natural renewable resources. Among these, solar power is advantageous in terms of area and maintenance cost. However, the high installation cost of conventional solar cells restricts individual uses; alternatively, lightweight and flexible solar cells evolved. Among them, Dye-Sensitized Solar-Cell (DSSC) are inexpensive and considered nanotechnological advancement. Step-by-step improvisation of the photo-conversion efficiency has been discussed in light of nanoengineering on metal oxides. Simultaneously, the dependence of wavelength on the choice of dye has also been focused opting for a particular application field. Energy storage device (solid-state batteries and/or supercapacitors) is an inevitable part of solar-cell for ensured use at required time and space. With the help of nanotechnology, the major problems of storage efficiency are critically pointed out with possible way-out. In this connection, the adopted nanoengineering aspects are extensively discussed considering improvements in the battery capacity, cycle life, and charge and discharge cycles with the highest degree of safety. Linking with the nanostructures, the nanotubular array provides a higher specific surface area maximizing the performance for both the DSSCs and energy-storage devices, as anode material. Again, the unidirectionality of the carrier transport path enhances electron collection. The present endeavor includes such research instances probing towards the amalgamation of these two technologies to indicate the futuristic direction of the self-chargeable storage unit. The present scope is designed broadly in three sections, where the first section deals with the step-by-step improvement of DSSC with a prime focus on the oxide nanotube-based photoanode. The second section deliberates on the research trends for storage devices with the nanotube-based anode. In the last section, the unification of these two technologies within a single chip or area using a common anode is the main emphasis to enhance the utility and green approach for the future world.