First-principles modeling of Pt/LaAlO3/SrTiO3capacitors under an external bias potential

Claudio Cazorla; Massimiliano Stengel

doi:10.1103/physrevb.85.075426

Nanocomposite Graphene based Tunable Absorber for Combating Electromagnetic Pollution

Current Nanoscience ◽

10.2174/1573413715666191204123307 ◽

2019 ◽

Vol 15 ◽

Author(s):

Surekha Rani ◽

Anupma Marwaha ◽

Sanjay Marwaha

Keyword(s):

Reflection Coefficient ◽

Traffic Congestion ◽

Microwave Absorber ◽

Electromagnetic Properties ◽

Electric Conductor ◽

High Frequency Structure Simulator ◽

Bias Potential ◽

External Bias ◽

Tunable Microwave ◽

Tunable Absorber

Background: Advancement in wireless communication technology has raised today’s living standards but consequently leads to the problems of electromagnetic (EM) air pollution as well as spectrum congestion particularly in radio frequency band. To overcome traffic congestion problem in lower bands, terahertz frequency bands are explored but EM pollution still persists as global issue which can be addressed by a tunable microwave absorber. At THz frequencies, 2-D nanostructured graphene has been observed to be less lossy than using other materials and further finds its most interesting applications on account of the plasmonic mode supported by graphene resulting in extreme device miniaturization. At micro and mm-waves graphene is resistive hence can be electronically controlled, ensuring its suitability for the design of tunable microwave absorber. Objective: Designing of a frequency reconfigurable or frequency tunable absorber is the prime objective of current work. Two-dimensional graphene absorber has been proposed here having inherent bandgap tunability property which means the electromagnetic properties of graphene can be controlled via varying external bias potential. Methods: The numerical modelling of graphene microwave absorber utilizing bulk graphene backed by glass and perfect electric conductor layer is reported in this paper. Finite element Method (FEM) based high frequency structure simulator (HFSS) platform is used to simulate the graphene absorber model. The whole structure is placed into a rectangular waveguide with two ports for absorber excitation. Results: The variation of electromagnetic properties of graphene absorber is achieved by changing bias potential and further the absorption tunability for the designed absorber is investigated in the range from 2 GHz to 18 GHz. From reflection coefficient curves, it is authenticated that -72.6 dB reflection coefficient dip has been obtained at 14 GHz for 5 volt bias potential which shifts to higher side of frequency as the potential changes from 5 volts to 25 volts. Conclusion: The results show that by increasing bias potential, absorption coefficient shifts to higher frequency and proves to be a tunable wideband absorber whose resonant frequency can changed from one value to another without changing thickness or material properties of absorber thus can effectively incorporate with antenna substrate or surface of radar.

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Photogeneration of hydrogen by Halobacterium halobium MMT22 coupled with silicon PN junction semiconductor without external bias potential — II

International Journal of Hydrogen Energy ◽

10.1016/0360-3199(92)90196-4 ◽

1992 ◽

Vol 17 (2) ◽

pp. 89-91

Author(s):

M TAQUIKHAN ◽

M ADIGA ◽

J BHATT

Keyword(s):

Halobacterium Halobium ◽

Bias Potential ◽

External Bias ◽

Pn Junction

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First-principles quantum transport in S3 clusters

International Journal of Modern Physics B ◽

10.1142/s0217979214502476 ◽

2014 ◽

Vol 29 (02) ◽

pp. 1450247

Author(s):

Jing-Xin Yu ◽

Xiu-Ying Liu ◽

Li-Ying Zhang ◽

Yan Cheng ◽

Xiang-Rong Chen

Keyword(s):

Bias Voltage ◽

Quantum Transport ◽

First Principles ◽

Electrical Transport ◽

Density Functional ◽

Electrical Transport Properties ◽

Open Chain ◽

Functional Theory ◽

External Bias ◽

The Relationship

The quantum transport in S3 clusters sandwiched between Au electrodes was investigated using density functional theory and nonequilibrium Green's function method. Five different configurations were considered, and the equilibrium conductance and the projected density of states were obtained at optimal positions. Results revealed local minima for two strain chains connected to the pyramidal electrodes at the top site and a triangular S3 open chain linked to the pyramidal electrodes at the top hollow site. The relationship between conductance and external bias voltage was also calculated. Transmission of straight chains was determined by resonance and strongly affected by the bias voltage. Transport of top-hollow configuration was dominated by several closely spaced and broad molecular orbitals; hence, the transmission coefficient was almost flat around the gold Fermi level. The calculations proved that the coupling morphologies of S3 clusters connected with the electrodes significantly affected the electrical transport properties of nanoscale junctions.

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