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Quantum-dot Cellular Automata (QCA) is an attractive nanoelectronics paradigm which is widely advocated as a possible replacement of conventional CMOS technology. Designing memory cells is a very interesting field of research in QCA domain. In this paper, we are going to propose novel nanotechnology-compatible designs based on the majority gate structures. In the first step, this objective is accomplished by QCA implementation of two well-organized JK flip-flop designs and in the second step; synchronous counters with different sizes are presented as an application. To evaluate functional correctness of the proposed designs and compare with state-of-the-art, QCADesigner tool is employed.

The quantum-dot cellular automata technology has great attention in nanoscale digital circuits design due to its high-speed and high-dense. Shift registers play vital role in digital circuits design. So, efficient implementation of shift register circuits in this technology is in the focal point of researches in digital circuits design. In this study, new structures are proposed for the shift register circuits in single layer, three layers and five layers based on inherent quantum-dot cellular automata clock. The QCADesigner tool version 2.0.3 is employed for simulation and verification of functionality of the proposed structures for the serial-input-serial-output shift register circuits. The results demonstrate that the developed 3-bit, 4-bit and 5-bit coplanar shift register circuits require 32, 44 and 56 cells, respectively. The comparison results demonstrate that the developed circuits provide advantages compared to other circuits in terms of area, cell count, clock cycles and cost.

Quantum-dot Cellular Automata (QCA) as a nanoscale transistor-less device technology offers distinguishing advantages over the limitations of CMOS circuits. This nanoelectronic is based on the mapping of binary logic in the two excess electrons configuration within a four-dot cell. In this paper, we propose a new ultra-low energy and low-complexity two-input XOR gate which can be employed as a basic component in designing a wide range of QCA logical circuits. For performance evaluation of the presented design in a large array of QCA structures, even parity generator circuit with different lengths up to 32 bits as well as LFSR circuit are designed and analyzed as instances of logical circuits. The simulation results reveal that our proposed designs have significant improvements in contrast to counterparts from hardware implementation requirements and energy consumption aspects. QCADesigner tool is utilized to evaluate functional correctness of the proposed circuits and power dissipation is evaluated using QCAPro simulator as an accurate power estimator tool.

Semiconducting, metallic and insulating nanowires are attractive building blocks in nanotechnology due to their small size and anisotropy. Moreover, it is possible to fabricate homogeneous or heterogeneous nanowires with high purity and crystallinity in a parallel and cost effective manner. Strategies have also emerged to position nanowires precisely on substrates to allow integration of nanoelectronic devices. In this chapter, we describe the fabrication and assembly of nanowires to form functional devices. Several fabrication strategies including vapor-liquid-solid (VLS) and electrodeposition in nanoporous templates are discussed. We detail advances made in the bottom-up integration of nanowires using patterned growth and directed assembly. Finally, some functional devices fabricated using nanowires are reviewed, and strategies to reduce errors and improve defect tolerance are discussed.

Electric field-induced magnetization switching in multiferroics is intriguing for both fundamental studies and potential technological applications. Here, we review the recent developments on electric field-induced magnetization switching in multiferroic heterostructures. Particularly, we study the dynamics of magnetization switching between the two stable states in a shape-anisotropic single-domain nanomagnet using stochastic Landau–Lifshitz–Gilbert (LLG) equation in the presence of thermal fluctuations. For magnetostrictive nanomagnets in strain-coupled multiferroic composites, such study of magnetization dynamics, contrary to steady-state scenario, revealed intriguing new phenomena on binary switching mechanism. While the traditional method of binary switching requires to tilt the potential profile to the desired state of switching, we show that no such tilting is necessary to switch successfully since the magnetization’s excursion out of magnet’s plane can generate a built-in asymmetry during switching. We also study the switching dynamics in multiferroic heterostructures having magnetoelectric coupling at the interface and magnetic exchange coupling that can facilitate to maintain the direction of switching with the polarity of the applied electric field. We calculate the performance metrics like switching delay and energy dissipation during switching while simulating LLG dynamics. The performance metrics turn out to be very encouraging for potential technological applications.

A systematic approach for designing Boolean logic gates is presented in this paper. A single array of Carbon nanotube field effect transistor (CNFET) capacitors is utilized as a voltage divider of input signals. Then, a special path, which is consisted of CNFETs with different threshold voltages, connects the proper voltage source to the output node for each voltage level. The main concept is illustrated with the concentration on 3-input functions. However, some other logic gates with higher number of input variables are also proposed within the paper. The sensitivity to diameter variation of CNTs is measured by applying Monte Carlo analysis. It is not needed to use Karnaugh map to simplify expressions and the designs structured with the new method, benefit from low transistor count and a fixed critical path regardless of the number of input variables in comparison with conventional and standard circuitry design methods. Several practical circuits are also deigned, which have the capability of working in low voltages.

The molecular nanoclusters proved to be very promising objects for applications in electronics not only because they have absolutely identical chemical structure and allow for bottom to top approach in constructing new electronic devices, but also for the possibility to design and create great variety of such clusters with specific properties. The formation and deposition of mixed Langmuir monolayers composed of inert amphiphile molecular matrix and guest ligand-stabilized metal-core nanoclusters are described. This approach allowed to obtain the ordered stable reproducible planar monolayer and multilayer nanocluster nanostructures on solid substrates. The use of novel polymeric Langmuir monolayers formed by amphiphilic polyelectrolytes and nanoclusters resulted in fabrication of ultimately thin monomolecular nanoscale-ordered stable planar polymeric nanocomposite films. The morphology and electron transport in fabricated nanostructures were studied experimentally using AFM and STM. The effects of single electron tunneling at room temperature through molecular cluster object containing finite number of localized states were theoretically investigated taking into account electron–electron Coulomb interaction. It is shown that tunnel current-bias voltage characteristic of such tunnel junction is characterized by a number of staircase steps equal to the number of cluster's eigenlevels, however the fronts of each steps are asymptotically linear with finite inclination. The analytically obtained current–voltage characteristics are in agreement with experimental results for electron tunneling through molecular nanoclusters at room temperatures.

Multiplexers are extremely important parts of signal control systems. Some critical circuits of computing systems, like memories, use large multiplexers in order to present the value of a specific memory cell to their output. Several quantum-dot cellular automata (QCA) circuits have been designed and the need for a QCA memory access system becomes prominent. A modular 2ⁿ to 1 QCA multiplexer covering small area could reduce the size of such circuits and conclusively could increase circuit integration. In this paper we present a novel design of a small size, modular quantum-dot cellular automata (QCA) 2ⁿ to 1 multiplexer that can be used for memory addressing. The design objective is to develop a modular design methodology which can be used to implement 2ⁿ to 1 multiplexers using building blocks. For the QCA implementation a careful consideration is taken into account concerning the design in order to increase the circuit stability.

This paper reviews the recent developments on building nanoelectronics for our future information processing paradigm using multiferroic composites. With appropriate choice of materials, when a tiny voltage of few tens of millivolts is applied across a multiferroic composite, i.e., a piezoelectric layer stain-coupled with a magnetostrictive layer, the piezoelectric layer gets strained and the generated stress in the magnetostrictive layer switches the magnetization direction between its two stable states. We particularly review the switching dynamics of magnetization and calculation of associated metrics like switching delay and energy dissipation. Such voltage-induced magnetization switching mechanism dissipates a minuscule amount of energy of only ~ 1 attojoule in sub-nanosecond switching delay at room-temperature. The performance metrics for such nonvolatile straintronic devices make them very attractive for building not only memory devices but also building logic, so that they can be deemed suitable for computational purposes. Hence, multiferroic straintronics has profound promise of contributing to beyond Moore's law technology, i.e., of being possible replacement of conventional charge-based electronics, which is reaching its performance limit specifically due to excessive energy dissipation.