Engineering Commons^™

Nitrogen Radiofrequency Plasma Treatment Of Graphene, Antoine Bident, Nathalie Caillault, Florence Delange, Christine Labrugere, Guillaume Aubert, Cyril Aymonier, Etienne Durand, Alain Demourgues, Yongfeng Lu, Jean-François Silvain

Department of Electrical and Computer Engineering: Faculty Publications

The incorporation of nitrogen (N) atoms into a graphitic network such as graphene (Gr) remains a major challenge. However, even if the insertion mechanisms are not yet fully understood, it is certain that the modification of the electrical properties of Gr is possible according to the configuration adopted. Several simulations work, notably using DFT, have shown that the incorporation of N in Gr can induce an increase in the electrical conductivity and N acts as an electron donor; this increase is linked to the amount of N, the sp²/sp³ carbon configuration, and the nature of C-N bonding. …

A Molecular Dynamics Study Of Water Confined In Between Two Graphene Sheets Under Compression, Ming-Lang Tseng, Ayomide Adesiyan, Abdelaziz Gassoumi, Nima E. Gorji

Articles

Several studies have demonstrated interest in creating surfaces with improved water interaction and adaptive properties because the behavior of water confined at the nanoscale plays a significant role in the synthesis of materials for technological applications. Remarkably, confinement at the nanoscale significantly modifies the characteristics of water. We determine the phase diagram of water contained by graphene stack sheets in slab form, at T=300 K, and for a constant pressure using molecular dynamics simulations. We discover that, as shown in the simulation, water can exist in both the liquid and vapor phases depending on the confining geometry and compressibility ratio. …

Graphene Based Tunable Terahertz Holographic Antennas, Pengfei Ren, Lijun Jiang, Ping Li

Electrical and Computer Engineering Faculty Research & Creative Works

In this work, several representative terahertz (THz) graphene holographic impedance surface antenna are presented. Different to the conventional impedance surface antenna that manipulates the surface impedance via varying the patch size in each unit cell, the surface impedance of the proposed antenna in this paper is readily controlled by applying a tunable DC biasing to each graphene patch cell, the physics behind which is that the conductivity of the graphene is a function of imposed voltage. Thus, the graphene patches of the proposed antenna have same size as well as equal spacing, which makes the modeling process more convenient and …

Recent Advances In Terahertz Photonic Technologies Based On Graphene And Their Applications, Tianjing Guo, Christos Argyropoulos

Department of Electrical and Computer Engineering: Faculty Publications

Graphene is a unique 2D material that has been extensively investigated due to its extraordinary photonic, electronic, thermal, and mechanical properties. Excited plasmons along its surface and other unique features are expected to play an important role in many emerging photonic technologies with drastically improved and tunable functionalities. This review is focused on presenting several recently introduced photonic phenomena based on graphene, beyond its usual linear response, such as nonlinear, active, topological, and nonreciprocal effects. The physical mechanisms and various envisioned photonic applications corresponding to these novel intriguing functionalities are also reported. The presented graphene-based technologies promise to revolutionize the …

Carbon Nanotube-On-Graphene Heterostructures, Yu Zheng, Dongmeng Li, Zubair Ahmed, Jeongwon Park, Changjian Zhou, Cary Y. Yang

Electrical and Computer Engineering

This paper presents a brief review of experimental and theoretical studies on a three-dimensional heterostructure consisting of vertical carbon nanotubes (CNTs) connected perpendicularly to a graphene layer. This structure can serve as a potential building block for an all-carbon network in energy storage devices and on-chip interconnects. The review highlights reported works on the fabrication and characterization of such a heterostructure, with focus on the effect of the CNT-graphene interface on electrical conduction. While a direct comparison between experiment and theory is not possible at this time, a brief survey of theoretical efforts based on atomic cluster models nonetheless reveals …

Inkjet-Printed Graphene-Based 1 × 2 Phased Array Antenna, Mahmuda Akter Monne, Peter Mack Grubb, Harold Stern, Harish Subbaraman, Ray T. Chen, Maggie Yihong Chen

Electrical and Computer Engineering Faculty Publications and Presentations

Low-cost and conformal phased array antennas (PAAs) on flexible substrates are of particular interest in many applications. The major deterrents to developing flexible PAA systems are the difficulty in integrating antenna and electronics circuits on the flexible surface, as well as the bendability and oxidation rate of radiating elements and electronics circuits. In this research, graphene ink was developed from graphene flakes and used to inkjet print the radiating element and the active channel of field effect transistors (FETs). Bending and oxidation tests were carried out to validate the application of printed flexible graphene thin films in flexible electronics. An …

Free Charge Carrier Properties In Two-Dimensional Materials And Monoclinic Oxides Studied By Optical Hall Effect, Sean Knight

Department of Electrical and Computer Engineering: Dissertations, Theses, and Student Research

In this dissertation, optical Hall effect (OHE) measurements are used to determine the free charge carrier properties of important two-dimensional materials and monoclinic oxides. Two-dimensional material systems have proven useful in high-frequency electronic devices due to their unique properties, such as high mobility, which arise from their two-dimensional nature. Monoclinic oxides exhibit many desirable characteristics, for example low-crystal symmetry which could lead to anisotropic carrier properties. Here, single-crystal monoclinic gallium oxide, an AlInN/GaN-based high-electron-mobility transistor (HEMT) structure, and epitaxial graphene are studied as examples. To characterize these material systems, the OHE measurement technique is employed. The OHE is a physical …

Tunable Compact Thz Devices Based On Graphene And Other 2d Material Metasurfaces, Tianjing Guo

Department of Electrical and Computer Engineering: Dissertations, Theses, and Student Research

Since the isolation of graphene in 2004, a large amount of research has been directed at 2D materials and their applications due to their unique characteristics. Compared with the noble metal plasmons in the visible and near-infrared frequencies, graphene can support surface plasmons in the lower frequencies of terahertz (THz) and midinfrared. Especially, the surface conductivity of graphene can be tuned by either chemical doping or electrostatic gating. As a result, the idea of designing graphene metasurfaces is attractive because of its ultra-broadband response and tunability.

It has been demonstrated theoretically and experimentally that the third-order nonlinearity of graphene at …

Carbon-Based Interlayers In Perovskite Solar Cells, Aleksandr P. Litvin, Xiaoyu Zhang, Kevin Berwick, Anatoly V. Fedorov, Weitao Zheng, Alexander V. Baranov

Articles

Perovskites are solution-processed, high-performance semiconductors of interest in low-cost photovoltaics. The interfaces between the perovskite photoactive layers and the top and bottom contacts are crucial for efficient charge transport and minimizing trapping. Control of the collection of charge carriers at these interfaces is decisive to device performance. Here, we review recent progress in the realization of efficient perovskite solar cells using cheap, easily processed, stable, carbon-based interlayers. Interface materials including graphene, carbon nanotubes, fullerenes, graphene quantum dots and carbon dots are introduced and their influence on device performance is discussed.

A Preliminary Study Of A Graphene Fractal Sierpinski Antenna, Alberto Boretti, Lorenzo Rosa, Jonathan Blackledge, Stefania Castelletto

Conference papers

We provide a preliminary study of a Graphene fractal antenna operating at THz frequencies with the opportunity to modulate the emission. There are a number of advantages of the fractal design, namely multiband/wideband ability, and, a smaller, lighter and simpler configuration for higher gain, that can benefit from the coupling with Graphene, the thinnest and strongest of materials exhibiting very high electrical conductivity and tunability. This paper proposes a conceptual background for the study and presents some preliminary results on the electromagnetic emission simulations undertaken

Numerical Methods For Electromagnetic Modeling Of Graphene: A Review, Kaikun Niu, Ping Li, Zhixiang Huang, Li (Lijun) Jun Jiang, Hakan Bagci

Electrical and Computer Engineering Faculty Research & Creative Works

Graphene's remarkable electrical, mechanical, thermal, and chemical properties have made this the frontier of many other 2-D materials a focus of significant research interest in the last decade. Many theoretical studies of the physical mechanisms behind these properties have been followed by those investing the graphene's practical use in various fields of engineering. Electromagnetics, optics, and photonics are among these fields, where potential benefits of graphene in improving the device/system performance have been studied. These studies are often carried out using simulation tools. To this end, many numerical methods have been developed to characterize electromagnetic field/wave interactions on graphene sheets …

Gamma-Ray Radiation Effects In Graphene-Based Transistors With H-Bn Nanometer Film Substrates, E. J. Cazalas, Michael R. Hogsed, S. R. Vangala, Michael R. Snure, John W. Mcclory

Faculty Publications

Radiation effects on graphene field effect transistors (GFETs) with hexagonal boron nitride (h-BN) thin film substrates are investigated using 60Co gamma-ray radiation. This study examines the radiation response using many samples with varying h-BN film thicknesses (1.6 and 20 nm thickness) and graphene channel lengths (5 and 10 μm). These samples were exposed to a total ionizing dose of approximately 1 Mrad(Si). I-V measurements were taken at fixed time intervals between irradiations and postirradiation. Dirac point voltage and current are extracted from the I-V measurements, as well as mobility, Dirac voltage hysteresis, and the total number of GFETs that remain …

Study Of Charge Carrier Transport In Graphene And Graphite As Two Dimensional And Quasi-Two Dimensional Materials And Their Interfaces, Nalat Sornkhampan

FIU Electronic Theses and Dissertations

Evidence of superconductivity in phosphorous-doped graphite and graphene has been observed at temperatures in the vicinity of 260 K. This evidence includes transport current, magnetic susceptibility, Hall and Nernst measurements. All of these measurements indicate a transition of a type II superconductor without a phase of type I until below the limits of the measurement capabilities.

Vortex states are inferred from periodically repeated steps in the R vs. T characteristics of Highly Oriented Pyrolytic Graphite and exfoliated doped multilayer graphene. The presence of vortices has been confirmed with thermal gradient driven Nernst measurements. Magnetic susceptibility measurements have shown results qualitatively …

Graphene Based Functional Devices: A Short Review, Rong Wang, Xin Gang Ren, Ze Yan, Li (Lijun) Jun Jiang, Wei E.I. Sha, Guang Cun Shan

Electrical and Computer Engineering Faculty Research & Creative Works

Graphene is an ideal 2D material system bridging electronic and photonic devices. It also breaks the fundamental speed and size limits by electronics and photonics, respectively. Graphene offers multiple functions of signal transmission, emission, modulation, and detection in a broad band, high speed, compact size, and low loss. Here, we have a brief view of graphene based functional devices at microwave, terahertz, and optical frequencies. Their fundamental physics and computational models were discussed as well.

Analysis Of Nonlinear Graphene Plasmonics Using Surface Integral Equations, Ling Ling Meng, Tian Xia, Xiaoyan Y.Z. Xiong, Li (Lijun) Jun Jiang, Weng Cho Chew

Electrical and Computer Engineering Faculty Research & Creative Works

Graphene plasmonics have attracted significant attention in the past few years due to the remarkable optical and electrical properties of graphene. A highly effective method based on surface integral equations (SIE) in the frequency domain is proposed to describe both linear and nonlinear effects of graphene efficiently and accurately. Graphene, a centrosymmet-ric material, can possess second harmonic generation (SHG) when the conductivity is nonlocal. In this work, the fundamental harmonic (FH) of a graphene wrapped particle is studied as the first benchmark by introducing a conducting surface in SIE. Then it is modified to analyze a graphene-based patch antenna in …

Effective Room-Temperature Ammonia-Sensitive Composite Sensor Based On Graphene Nanoplates And Pani, Zongbiao Ye, Yan Chen, Bohao Liu, Yuanjie Su, Zhi Chen, Huiling Tai, Yadong Jiang

Electrical and Computer Engineering Faculty Publications

The graphene nanoplate (GN)-polyaniline (PANI) composite was developed via in-situ polymerization method and simultaneously assembled on interdigital electrodes (IDEs) at low temperature for ammonia (NH₃) detection. The assembled composite sensor showed excellent sensing performance toward different concentrations of NH₃, 1.5 of response value and 123 s/204 s for the response/recovery time to 15 ppm NH₃. Meanwhile, an interesting supersaturation phenomenon was observed at high concentration of NH₃. A reasonable speculation was proposed for this special sensing behavior and the mechanism for enhanced sensing properties was also analyzed.

Graphene Field Effect Transistors For Highly Sensitive And Selective Detection Of K+ Ions, Hongmei Li, Yihao Zhu, Md. Sayful Islam, Md. Anisur Rahman, Kenneth B. Walsh, Goutam Koley

Publications

Graphene-based ion sensitive field effect transistors (GISFETs) with high sensitivity and selectivity for K+ ion detection have been demonstrated utilizing valinomycin based ion selective membrane. The performance of the GISFETs for K+ ion detection was studied in various media over a concentration range of 1 μM–2 mM. The sensitivity of the sensor was found to be >60 mV/decade, which is comparable to the best Si-based commercial ISFETs, with negligible interference found from Na+ and Ca2+ ions in high concentration. The sensor performance did not change significantly in Tris–HCl solution or with repeated testing over a period of two months highlighting …

Band Gap Engineering Of 2d Nanomaterials And Graphene Based Heterostructure Devices, Md Monirojjaman Monshi

FIU Electronic Theses and Dissertations

Two-Dimensional (2D) materials often exhibit distinguished properties as compared to their 3D counterparts and offer great potential to advance technology. However, even graphene, the first synthesized 2D material, still faces several challenges, despite its high mobility and high thermal conductivity. Similarly, germanene and silicene face challenges due to readily available semiconducting properties to be used in electronics, photonics or photocatalysis applications. Here, we propose two approaches to tune the band gap: One is by forming nanoribbon and edge functionalization and another by doping using inorganic nanoparticle’s interaction with 2D nanomaterials.

Edge functionalization of armchair germanene nanoribbons (AGeNRs) has the potential …

Electronic And Magnetic Properties Of Two-Dimensional Nanomaterials Beyond Graphene And Their Gas Sensing Applications: Silicene, Germanene, And Boron Carbide, Sadegh Mehdi Aghaei

FIU Electronic Theses and Dissertations

The popularity of graphene owing to its unique properties has triggered huge interest in other two-dimensional (2D) nanomaterials. Among them, silicene shows considerable promise for electronic devices due to the expected compatibility with silicon electronics. However, the high-end potential application of silicene in electronic devices is limited owing to the lack of an energy band gap. Hence, the principal objective of this research is to tune the electronic and magnetic properties of silicene related nanomaterials through first-principles models.

I first explored the impact of edge functionalization and doping on the stabilities, electronic, and magnetic properties of silicene nanoribbons (SiNRs) and …

Flatland Plasmonics And Nanophotonics Based On Graphene And Beyond, Pai-Yen Chen, Christos Argyropoulos, Mohamed Farhat, J. Sebastian Gomez-Diaz

Department of Electrical and Computer Engineering: Faculty Publications

In this paper, we review and discuss how the recently discovered two-dimensional (2D) Dirac materials, particularly graphene, may be utilized as new efficient platforms for excitations of propagating and localized surface plasmon polaritons (SPPs) in the terahertz (THz) and mid-infrared (MIR) regions. The surface plasmon modes supported by the metallic 2D materials exhibit tunable plasmon resonances that are essential, yet missing, ingredients needed for THz and MIR photonic and optoelectronic devices. We describe how the atomically thin graphene monolayer and metamaterial structures based on it may tailor and control the spectral, spatial, and temporal properties of electromagnetic radiation. In the …

Sonochemical Synthesis Of Zinc Oxide Nanostructures For Sensing And Energy Harvesting, Phani Kiran Vabbina

FIU Electronic Theses and Dissertations

Semiconductor nanostructures have attracted considerable research interest due to their unique physical and chemical properties at nanoscale which open new frontiers for applications in electronics and sensing. Zinc oxide nanostructures with a wide range of applications, especially in optoelectronic devices and bio sensing, have been the focus of research over the past few decades. However ZnO nanostructures have failed to penetrate the market as they were expected to, a few years ago. The two main reasons widely recognized as bottleneck for ZnO nanostructures are (1) Synthesis technique which is fast, economical, and environmentally benign which would allow the growth on …

An Equivalent Circuit Model For Graphene-Based Terahertz Antenna Using The Peec Method, Ying S. Cao, Li (Lijun) Jun Jiang, Albert E. Ruehli

Electrical and Computer Engineering Faculty Research & Creative Works

The electromagnetic (EM) characterization of graphene under general EM environments is becoming of interest in the engineering and scientific research fields. However, its numerical modeling process is extremely cost prohibitive due to the huge contrast between its thickness and other dimensions. In this work, for the first time, the EM features of graphene are characterized by a circuit model through the partial element equivalent circuit (PEEC) method. The atomically thick graphene is equivalently replaced by an impedance boundary condition. After incorporating the PEEC method, a novel surface conductivity circuit model is derived for graphene. A physical resistor and inductor are …

Advanced Graphene Microelectronic Devices, Chowdhury G. Al-Amin

FIU Electronic Theses and Dissertations

The outstanding electrical and material properties of Graphene have made it a promising material for several fields of analog applications, though its zero bandgap precludes its application in digital and logic devices. With its remarkably high electron mobility at room temperature, Graphene also has strong potential for terahertz (THz) plasmonic devices. However there still are challenges to be solved to realize Graphene’s full potential for practical applications.

In this dissertation, we investigate solutions for some of these challenges. First, to reduce the access resistances which significantly reduces the radio frequency (RF) performance of Graphene field effect transistors (GFETs), a novel …

Ellipsometric Characterization Of Silicon And Carbon Junctions For Advanced Electronics, Alexander G. Boosalis

Department of Electrical and Computer Engineering: Dissertations, Theses, and Student Research

Ellipsometry has long been a valuable technique for the optical characterization of layered systems and thin films. While simple systems like epitaxial silicon dioxide are easily characterized, complex systems of silicon and carbon junctions have proven difficult to analyze. Traditional model dielectric functions for layered silicon homojunctions, a system with a similar structure to modern transistors, often have correlated parameters during ellipsometric data analysis. Similarly, epitaxial graphene as grown from thermal sublimation of silicon from silicon carbide or through chemical vapor deposition, tend to have model dielectric function parameters that correlate with the optical thickness of the graphene due to …

Dgtd Analysis Of Electromagnetic Scattering From Penetrable Conductive Objects With Ibc, Ping Li, Yifei Shi, Li (Lijun) Jun Jiang, Hakan Bagci

Electrical and Computer Engineering Faculty Research & Creative Works

To avoid straightforward volumetric discretization, a discontinuous Galerkin time-domain (DGTD) method integrated with the impedance boundary condition (IBC) is presented in this paper to analyze the scattering from objects with finite conductivity. Two situations are considered. 1) The skin depth is smaller than the thickness of the conductive volume. 2) The skin depth is larger than the thickness of a thin conductive sheet. For the first situation, a surface impedance boundary condition (SIBC) is employed, wherein the surface impedance usually exhibits a complex relation with the frequency. To incorporate the SIBC into DGTD, the surface impedance is first approximated by …

Tunable Absorption Based On Plasmonic Nanostructures Loaded With Graphene, Christos Argyropoulos

Department of Electrical and Computer Engineering: Faculty Publications

We present simulations of a hybrid graphene-plasmonic device constituted by periodic metallic nanowires placed over a dielectric spacer layer and a metallic film. The spacer layer is composed of a thin silica layer combined with an one-atom-thick graphene sheet. An electrically controlled ultra-compact absorption modulator can be realized based on the proposed theoretical device.

A Sensitive Film Structure Improvement Of Reduced Graphene Oxide Based Resistive Gas Sensors, Yong Zhou, Guangzhong Xie, Tao Xie, Huan Yuan, Huiling Tai, Yadong Jiang, Zhi Chen

Electrical and Computer Engineering Faculty Publications

This study was focused on how to improve the gas sensing properties of resistive gas sensors based on reduced graphene oxide. Sol-airbrush technology was utilized to prepare reduced graphene oxide films using porous zinc oxide films as supporting materials mainly for carbon dioxide sensing applications. The proposed film structure improved the sensitivity and the response/recovery speed of the sensors compared to those of the conventional ones and alleviated the restrictions of sensors' performance to the film thickness. In addition, the fabrication technology is relatively simple and has potential for mass production in industry. The improvement in the sensitivity and the …

Terahertz Antenna Phase Shifters Using Integrally-Gated Graphene Transmission-Lines, Pai-Yen Chen, Christos Argyropoulos, Andrea Alu

Department of Electrical and Computer Engineering: Faculty Publications

We propose the concept and design of terahertz (THz) phase shifters for phased antenna arrays based on integrally- gated graphene parallel-plate waveguides (GPPWGs). We show that an active transmission-line may be realized by combining GPPWGs with double-gate electrodes, in which the applied gate voltage can control the guiding properties of the gated sections. This may enable the realization of THz electronic switches and tunable loaded-lines for sub mm-wave antenna systems. Based on these active components, we theoretically and numerically demonstrate several digital and analog phase shifter designs for THz frequencies, with a wide range of phase shifts and small return …

Transparent Actuator Made With Few Layer Graphene Electrode And Dielectric Elastomer, For Variable Focus Lens, Taeseon Hwang, Hyeok-Yong Kwon, Joon-Suk Oh, Jung-Pyo Hong, Seung-Chul Hong, Youngkwan Lee, Hyouk Ryeo Choi, Kwang J. Kim, Mainul Hossain Bhuiya, Jae Do Nam

Mechanical Engineering Faculty Research

A transparent dielectric elastomer actuator driven by few-layer-graphene (FLG) electrode was experimentally investigated. The electrodes were made of graphene, which was dispersed inN-methyl-pyrrolidone. The transparent actuator was fabricated from developed FLG electrodes.The FLG electrode with its sheet resistance of 0.45 kΩ/sq (80 nm thick) was implemented to mask silicone elastomer. The developed FLG-driven actuator exhibited an optical transparency of over 57% at a wavenumber of 600 nm and produced bending displacement performance ranging from 29 to 946 μm as functions of frequency and voltage. The focus variation was clearly demonstrated under actuation to study its application-feasibility in …

Nanoscale Contacts Between Semiconducting Nanowires And Metallic Graphenes, Seongmin Kim, David B. Janes, Sung-Yool Choi, Sanghyun Ju

Birck and NCN Publications

Metal–semiconductor (M–S) junctions are important components in many semiconductor devices, and there is growing interest in realizing high quality M–S contacts that are optically transparent. In this paper, we present our investigations into the characteristics of M–S junction in a semiconducting ZnO nanowire that was directly grown on a multilayer graphene film (MGF). The synthesized nanowires were fabricated into two-terminal devices with MGF as one contact and Al as the other contact. By comparison with devices employing Al contacts at both ends, the nanowire resistivity and specific contact resistivity of the MGF–nanowire contact can be extracted. The extracted specific contact …