Two new robust quaternary half adder (QHA) circuits (one single source and one multiple sources) are proposed in this work for low power applications. The proposed circuits are designed in hybrid fashion based on three types of quaternary inverter circuits and compared with recently proposed existing models in terms of number of supplies, power dissipation, delay, power-delay product (PDP) and transistor count through extensive simulations in Cadence Virtuoso platform using Stanford's Virtual Source-Carbon Nanotube Field Effect Transistor (VS-CNTFET) model. The sensitivity of the circuits in response to process parameters, voltage and temperature (PVT) variations are also evaluated. The proposed circuit with multiple sources has the lowest values of 4.92 uW for power consumption and 0.124 fJ for PDP compared to all other designs. Simulation results also demonstrate better stability to PVT variation for both the proposed architectures with respect to power and PDP parameters. In order to evaluate the competency of the proposed QHAs, quaternary full adder (QFA) circuits are designed using the proposed QHAs and other relevant models. Extensive simulation data confirm that the proposed circuits outperform others in terms of power penalty.
This work demonstrates a one-dimensional unidirectional terahertz (THz) absorber with thermal switching from broadband to narrowband and tunable multiple narrowband absorption with vanadium dioxide (VO2)-graphene-based defective photonic crystal. The thermal tuning of defect layer switches the phase of VO2 and obtain multiple narrowband optical absorptance with 70-90% peak at 4.12, 4.86 and 5.23THz respectively with a Q factor around 291 for 4.86 THz peak. The thermal dependent Q factor of the stack varies from 19 to 291 with phase transition from metal to the insulating state of the defect. The optical non-magnetic THz unidirectional absorber has switchable propagation functions within the metallic phase from non-absorption to higher peak absorption with forward and backward propagated wave. The asymmetrical dual defect layer with dual absorption peaks can be switched and the wavelength can be changed by changing the distance between the two peaks. Multiple graphene-based VO2 defects have increased peaks of narrowband absorption. This novel phase changing material (PCM) based asymmetric defective photonic layer can tune the defect layer for optimum and adjustable absorption at THz range and non-magnetic reciprocal and unidirectional structure with temperature dependent dual band switchable, which leads to this structure for terahertz wireless communication systems as well as other THz sensing devices.
Abstract-Multivalued logic is an extension of Boolean algebra with high radix approaches and is preferable over conventional binary logic operations for reduction in interconnection cost, chip area both on-chip and between chips and high information handing capability. This paper includes the design of elementary combinational quaternary operators that have sufficient representative capability to efficiently implement in intricate quaternary arithmetic circuits. Design of several combinational logic circuits have been presented which can function individually and in logic blocks for designing further complex circuits resulting in a reduction of circuit complexity and better speed processing in integrated circuit technology.Index Terms-Cycle gate, max and min gate, multivalued logic, quaternary algebra. I. INTRODUCTIONBinary logic has been predominant in embedded system and a fundamental for computer programming and mathematical logic due to its easy accessibility and widespread use in logic circuits. Operating with binary logic implies to controlling the real world with computers and that an alternative improved approach with a better usage of transmission path, storage and processing of large amount of information in digital signal processing even exist seems somewhat impossible. Yet, Moore's law states that, the number of transistors on integrated circuits doubles approximately every two years. As this law has been by far proven accurate, it is high time we considered alternative approaches to reduce this tremendous positive rate of elements used in integrated circuits. It has been suggested that by increasing the processing speed, memory capacity, sensors or memory states, this significant rate can be inhibited to an exponential rate. But, due to the inherent limitation data representation system of only two distinct levels {0, 1}, binary logic impedes the scope for multiple states and lacks high speed and information handling capacity. On the other hand, multivalued number systems, such as ternary and quaternary systems with a radix more than '2' (p>2) emerges with the immediate benefit of larger information handling and storage capacities.Multivalued logic system introduces new operators in addition to binary values {0, 1} and is a proposed extension of the idea that n valued logic can be used instead of two logical values (that is, true or false, logic high or low) where n>2 [1].Perhaps one of the most tangible immediate benefits of Manuscript received September 9, 2014; revised January 5, 2015.The authors were with the Ahsanullah University of Science and Technology, Dhaka, Bangladesh (e-mail: asif.faiyaz@gmail.com).higher-radix approaches like quaternary logic lies in their potential for reduction of the wiring congestion and interconnection cost [2]. Using a single conductor to transmit three or more discrete voltage or current values allows for greater information content per wire and thus results in a circuit with reduced conductors and logic gates than the binary-valued counterpart. Furthermore model...
Solar cells, photovoltaic devices and optoelectronic elements needs enhanced light absorption with a wide range of incident angle for better and efficient design. Two-dimensional (2D) materials have exceled in all areas including electrical applications, optical modulations, mechanical as well as chemical implementations due to their direct bandgap and high optical absorption nature[1]. Photon irradiation allows to generate electron-hole pairs in a direct bandgap material such as TMDCs which makes them potential candidates for large amount of light to be trapped. Different structures have been studied to achieve high optical absorption [2][3]. Although one dimensional photonic crystal(1DPC) and defective PC has good optical absorption with wide range and angle [4],[2] number of layers and complexity in structure has made it difficult to be fabricated. MoS2 monolayer structure based on cover spacer, plasmonic and dual substrate layer (SiO2(50nm)/Si ) has also increased optical absorption range and broad angle [5] but TMDC based heterostructures with spacer has improved absorption comparing to previous structures without metallic layer [6]. In this paper, we proposed a dual TMDC-spacer based plasmonic structure with dual substrate for wide and broad range and angle of near perfect optical absorption. The structure considered here is an air/MoS2/Spacer1/MoS2/Spacer2/plasmonic/dual substrate with 0.665nm, 70nm and 50nm layer of MoS2, Au as plasmonic layer and SiO2 as part of dual layer with Si as lossless substate. (Figure 1) For spacers SiO2 and TiO2 are taken with optimized value (figure 2) of 92 and 68nm for enhanced absorption. The transfer matrix of the constituted layer for either transverse electric (TE) or transverse magnetic (TM) polarization was determined using the transfer matrix method (TMM). Both in TE and TM mode, the ~30 and ~40% of enhanced light absorption are observed in proposed structure compared to hetero and mono layer structure (figure 3) with impact of metallic and spacer layer. In case of incident angle, both at resonance frequency of MoS2 and within visible range, broad angle range (00-400 for TE and 00-800 for TM) is observed with wider wavelength. (Figure 4 and figure 5). Impact of various metallic layer on the proposed structure is also observed (Figure 6). Structure with VO2 as plasmonic layer [7] has around ~95% of peak absorption (400nm-550nm) and wide incident angle (00-850) irrespective of polarizations with lieu of spacer hetero-TMDC-stack (Figure 7). Due to multiple layers of structures, collective surface plasmon polaritons (SPP) has an enhanced light absorption within the heterostructure and enhanced electric field distribution of the structure is observed (Figure 8). Table I lists some comparison among various structures and parameters indicates that proposed dual spacer -TMDC based plasmonic heterostructure has wide visible range of wavelength (400-550 nm) with broad angle (00-850) light absorption with both polarizations compare to other counterparts. In this work an enhanced range in both wavelength and incident angle of visible optical absorption is observed in both polarization with plasmonic dual heterostructure is observed and compared with other structures. Such structures are useful for photodetectors and solar cells for maximum absorptions. [1] Lopez-Sanchez O, Lembke D, Kayci M, Radenovic A and Kis A 2013 Ultrasensitive photodetectors based on monolayer MoS 2 Nat. Nanotechnol. 8 497–501 [2] Ansari N and Mohebbi E 2018 Broadband and high absorption in Fibonacci photonic crystal including MoS2 monolayer in the visible range J. Phys. D. Appl. Phys. 51 149–52 [3] Ansari N and Ghorbani F 2018 Light absorption optimization in two-dimensional transition metal dichalcogenide van der Waals heterostructures J. Opt. Soc. Am. B 35 1179 [4] Ansari N and Mohebbi E 2016 Increasing optical absorption in one-dimensional photonic crystals including MoS2 monolayer for photovoltaics applications Opt. Mater. (Amst). 62 152–8 [5] Ansari N, Mohebbi E and Gholami F 2020 Nearly perfect and broadband optical absorption by TMDCs in cover/TMDC/spacer/Au/substrate multilayers Appl. Phys. B Lasers Opt. 126 1–6 [6] Ansari N, Goudarzi B and Mohebbi E 2021 Design of narrowband or broadband absorber by heterostructures including TMDCs and spacers Opt. Laser Technol. 138 106771 [7] Das H R and Arya S C 2021 Performance improvement of VO2 and ITO based plasmonic electro-absorption modulators at 1550 nm application wavelength Opt. Commun. 479 Figure 1
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