Asir Intisar Khan

Impact of vacancies on the thermal conductivity of graphene nanoribbons: A molecular dynamics simulation study

Equilibrium molecular dynamics simulation using 2nd generation Reactive Bond Order interatomic potential has been performed to model the thermal transport of nanometer sized zigzag defected graphene nanoribbons (GNRs) containing several types of vacancies. We have investigated the thermal conductivity of defected GNRs as a function of vacancy concentration within a range of 0.5% to 5% and temperature ranging from 300K to 600K, along with a comparative analysis of those for pristine GNRs. We find that, a vacancy concentration of 0.5% leads to over 90% reduction in the thermal conductivity of GNRs. At low defect concentration, the decay rate is faster but ceases gradually at higher defect concentration. With the increasing temperature, thermal conductivity of defected GNRs decreases but shows less variation in comparison with that of pristine GNRs at higher temperatures. Such comprehensive study on several vacancy type defects in GNRs can provide further insight to tune up the thermal transport characterist...

Thermal transport in graphene/stanene hetero-bilayer nanostructures with vacancies: an equilibrium molecular dynamics study

In this study, we have performed equilibrium molecular dynamics simulations to model the thermal transport in nanometer sized graphene/stanene hetero-bilayer structures. Our simulations include the computation of thermal conductivity of pristine as well as defected structures containing several types of vacancies namely point vacancy, bi-vacancy and edge-vacancy. The room temperature thermal conductivity of the pristine 10 nm × 3 nm graphene/stanene hetero-bilayer is estimated to be 127.2 ± 13.8 W m−1 K−1. We have studied the impact of temperature and width of the sample on thermal transport in both pristine and defected nanoribbons. Thermal conductivity is found to decrease with the increasing temperature while it tends to increase with the increasing width. Furthermore, we have investigated the thermal conductivity of defected bilayers as a function of vacancy concentration within a range of 0.5% to 2% and compared those for pristine structures. A vacancy concentration of 2% leads to 50–70% reduction in the thermal conductivity of the pristine bilayer nanoribbons. Such a study provides a good insight into the optimization and control of thermal transport characteristics of the low dimensional graphene/stanene nanostructure based thermal and nanoelectronic devices.

Characterization of thermal and mechanical properties of stanene nanoribbons: a molecular dynamics study

Stanene, a buckled honeycomb structure of monolayer tin, has several intriguing electrical and thermoelectrical applications that closely depend on its thermal, mechanical, and electrical properties. However, thermal and mechanical characterizations of stanene nanoribbons (STNRs) have not yet been comprehensively investigated. In this study, we have performed an equilibrium molecular dynamics simulation to characterize the thermal and mechanical properties of STNRs using the modified embedded-atom method potential. The room temperature thermal conductivities of pristine 10 nm × 3 nm zigzag and armchair stanene nanoribbon were estimated to be 0.95 ± 0.024 W m−1 K−1 and 0.89 ± 0.026 W m−1 K−1, respectively. We also studied the thermal conductivity as a function of temperature and width of the ribbon. The thermal conductivity was found to decrease with increasing temperature, whereas it tends to increase with increasing width for both configurations. In all cases, the zigzag STNR exhibited a higher thermal conductivity than its armchair counterpart did. Furthermore, our study includes an investigation of the thermal transport in defected STNRs. For a defect concentration of ∼1.5%, the thermal conductivity of defected stanene nanoribbon experiences a reduction of approximately 30–50%, whereas a ∼70–90% reduction was observed at a vacancy concentration of ∼5% for various types of defects. Finally, the stress–strain behavior of STNRs with varying width was analyzed using uniaxial loading. Zigzag STNRs were found to have higher fracture strength than their armchair counterparts. Moreover, with increasing width, both fracture strain and fracture stress of armchair STNRs were found to show small variations compared with their zigzag counterparts. This study provides insights for tuning the thermo-mechanical characteristics of stanene-based nanostructures for thermal management and possible applications as thermoelectrics.

Thermal transport characterization of hexagonal boron nitride nanoribbons using molecular dynamics simulation

Due to similar atomic bonding and electronic structure to graphene, hexagonal boron nitride (h-BN) has broad application prospects such as the design of next generation energy efficient nano-electronic devices. Practical design and efficient performance of these devices based on h-BN nanostructures would require proper thermal characterization of h-BN nanostructures. Hence, in this study we have performed equilibrium molecular dynamics (EMD) simulation using an optimized Tersoff-type interatomic potential to model the thermal transport of nanometer sized zigzag hexagonal boron nitride nanoribbons (h-BNNRs). We have investigated the thermal conductivity of h-BNNRs as a function of temperature, length and width. Thermal conductivity of h-BNNRs shows strong temperature dependence. With increasing width, thermal conductivity increases while an opposite pattern is observed with the increase in length. Our study on h-BNNRs shows considerably lower thermal conductivity compared to GNRs. To elucidate these aspect...

Bangla voice controlled robot for rescue operation in noisy environment

We present the design and implementation of a prototype of Bangla voice controlled robotic motion based on an efficient and unique algorithm for accurately detecting Bangla voice commands. For the detection of Bangla voice commands to control the movement, our developed speech detection system incorporates Mel-Frequency Cepstrum Coefficients based speech feature extraction mechanism and a feature matching technique using Vector Quantization. Our proposed Bangla voice controlled robotic motion can be very effective in rescue operation and disaster management system where a rescuer can dynamically give the rescue robot voiced instructions instead of being stagnant in a place for its controlling. Additional features including dynamic path generating algorithm for the traversed path, capability to accurately follow a specific map to reach a certain destination, detection of different gases and dynamic obstacle avoidance as well as precise position and movement control system add to the flexibility and dimension of the robotic motion. Apart from its possible application in industrial automation, Bangla voice controlled robotic motion can also encourage the view of a robotic machine as a partner rather than a tool by providing a smooth, easy and flexible mean of self-reliant movement for the physically challenged people speaking Bangla language throughout the world.

A molecular dynamics study on thermal conductivity of armchair graphene nanoribbon

Following the recent studies and progress for proper characterization of thermal transport in low dimensional carbon based materials, in this paper we investigate the thermal conductivity of nanostructured armchair graphene nanoribbon (GNR). Equilibrium molecular dynamics simulations using 2nd generation Reactive Empirical Bond Order (REBO) potential has been performed to explore the dependence of thermal conductivity on temperature, length and width for armchair configured GNRs. Thermal conductivity of armchair GNRs is found to decrease monotonically with the increase of temperature. However, it has been found that, thermal conductivity increases with the increase in both length and width for armchair GNRs. Furthermore, we have analyzed the edge shape dependence of thermal conductivity for GNRs. Thermal conductivity variation for armchair GNRs depicted in this study is qualitatively similar with those of zigzag edged GNRs. But, quantitatively thermal conductivity for GNRs with armchair edges computed in this study is 30–50% smaller than its zigzag counterpart which has been further analyzed.

Novel Realization of Quantum Ternary Mux and Demux

We present novel quantum realization of 3 times 1 ternary multiplexer and 1 times 3 ternary demultiplexer using generalized ternary gates (GTGs)

Novel Realization of Some Ternary Circuits for Quantum Computing

We present novel realization of ternary Toffoli gate and modified Fredkin gate for quantum computing using generalized ternary gate (GTG) which are truly realizable quantum gates. Our realization of ternary Toffoli gate is more efficient than the previous results and we are the first to realize the modified Fredkin gate using GTGs

Stanene-hexagonal boron nitride heterobilayer: Structure and characterization of electronic property

The structural and electronic properties of stanene/hexagonal boron nitride (Sn/h-BN) heterobilayer with different stacking patterns are studied using first principle calculations within the framework of density functional theory. The electronic band structure of different stacking patterns shows a direct band gap of ~30 meV at Dirac point and at the Fermi energy level with a Fermi velocity of ~0.53 × 106 ms−1. Linear Dirac dispersion relation is nearly preserved and the calculated small effective mass in the order of 0.05mo suggests high carrier mobility. Density of states and space charge distribution of the considered heterobilayer structure near the conduction and the valence bands show unsaturated π orbitals of stanene. This indicates that electronic carriers are expected to transport only through the stanene layer, thereby leaving the h-BN layer to be a good choice as a substrate for the heterostructure. We have also explored the modulation of the obtained band gap by changing the interlayer spacing between h-BN and Sn layer and by applying tensile biaxial strain to the heterostructure. A small increase in the band gap is observed with the increasing percentage of strain. Our results suggest that, Sn/h-BN heterostructure can be a potential candidate for Sn-based nanoelectronics and spintronic applications.