Engineering Commons^™

Creation Of Carbon Nanotube Based Biosensors Through Dielectrophoretic Assembly, Nilan S. Mani, Steve Kim, Kaushik Annam, Danielle Bane, Guru Subramanyam

Guru Subramanyam

Due to their excellent electrical, optical, and mechanical properties, nanosized single wall carbon nanotubes (SWNTs) have attracted significant attention as a transducing element in nano-bio sensor research. Controlled assembly, device fabrication, and bio-functionalization of the SWNTs are crucial in creating the sensors. In this study, working biosensor platforms were created using dielectrophoretic assembly of single wall carbon nanotubes (SWNTs) as a bridge between two gold electrodes. SWNTs in a commercial SDS surfactant solution were dispensed in the gap between the two gold electrodes, followed by applying an ac voltage across the two electrodes. The dielectrophoresis aligns the CNTs and forms …

Dna Based Electrolyte/Separator For Lithium Battery Application, Jitendra Kumar, Fahima Ouchen-Bouchendouka, Devin A. Smarra, Guru Subramanyam, James Grote

Guru Subramanyam

In this study, we demonstrated the use of DNA-CTMA (DC) in combination with PolyVinylidene Fluoride (PVDF) as a host matrix or separator for Lithium based electrolyte to form solid polymer/gel like electrolyte for potential application in Li-ion batteries.

The addition of DC provided a better thermal stability of the composite electrolyte as shown by the thermos-gravimetric analysis (TGA). The AC conductivity measurements suggest that the addition of DC to the gel electrolyte had no effect on the overall ionic conductivity of the composite. The obtained films are flexible with high mechanical stretch-ability as compared to the gel type electrolytes only.

Vanadium Oxide Thin-Film Variable Resistor-Based Rf Switches, Kuanchang Pan, Weisong Wang, Eunsung Shin, Kelvin Freeman, Guru Subramanyam

Guru Subramanyam

Vanadium dioxide (VO2) is a unique phase change material (PCM) that possesses a metal-to-insulator transition property. Pristine VO2 has a negative temperature coefficient of resistance, and it undergoes an insulator-to-metal phase change at a transition temperature of 68°C. Such a property makes the VO2 thin-film-based variable resistor (varistor) a good candidate in reconfigurable electronics to be integrated with different RF devices such as inductors, varactors, and antennas. Series single-pole single-throw (SPST) switches with integrated VO2 thin films were designed, fabricated, and tested. The overall size of the device is 380 μm × 600 μm. The SPST switches were fabricated on …

A High Performance Ceramic-Polymer Separator For Lithium Batteries, Jitendra Kumar, Padmakar Kichambare, Amarendra K. Rai, Rabi Bhattacharya, Stanley J. Rodrigues, Guru Subramanyam

Guru Subramanyam

A three-layered (ceramic-polymer-ceramic) hybrid separator was prepared by coating ceramic electrolyte [lithium aluminum germanium phosphate (LAGP)] over both sides of polyethylene (PE) polymer membrane using electron beam physical vapor deposition (EB-PVD) technique. Ionic conductivities of membranes were evaluated after soaking PE and LAGP/PE/LAGP membranes in a 1 Molar (1M) lithium hexafluroarsenate (LiAsF6) electrolyte in ethylene carbonate (EC), dimethyl carbonate (DMC) and ethylmethyl carbonate (EMC) in volume ratio (1:1:1). Scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques were employed to evaluate morphology and structure of the separators before and after cycling performance tests to better understand structure-property correlation. As compared …

Industry-University Collaboration: A University Of Dayton Model, Guru Subramanyam

Guru Subramanyam

This paper introduces industry-university collaboration activities currently in place at the University of Dayton's School of Engineering. These collaborations are important to prepare industry-ready graduates who excel in technical, entrepreneurial, and leadership skills. One of the key curricular components is the industry-sponsored multidisciplinary projects. Industry involvement in advisory committee, strategic research partnerships, and other forms are discussed.

Tunable Electromagnetic Bandgap Performance Of Coplanar Waveguides Periodically Loaded By Ferroelectric Varactors, D. Kuylenstierna, Guru Subramanyam, A. Vorobiev, S. Gevorgian

Guru Subramanyam

To achieve tunable electromagnetic bandgap (EBG) performance, ferroelectric varactors are considered, in LC circuits, for periodically loading coplanar waveguides (CPWs). Asymmetric or symmetric tuning of the bandgap width may be achieved by changing the capacitance of the varactors in the LC circuits. To validate this concept, tunable EBG arrays based on silicon substrate CPWs, including thin film SrTiO3 (STO) varactors, are fabricated and tested experimentally. The EBGs are designed so that the first band gap starts between 20 and 30 GHz. Up to 10% tuning is achieved, under 20-V DC applied bias, in the EBG structures.

A New Method For Electrical Characterization Of Ferroelectric Thin Films At Microwave Frequencies, Guru Subramanyam

Guru Subramanyam

Read More: http://www.worldscientific.com/doi/abs/10.1142/S179329200900154X

Capacitance Of Thin-Film Ferroelectrics Under Different Drive Signals, Huadong Li, Guru Subramanyam

Guru Subramanyam

Thin-film ferroelectric capacitance can be obtained by 2 different methods. Capacitance obtained using the derivative of its hysteresis loop is related to large applied signals and can be called the large-signal capacitance. Capacitance measured directly with a small, applied ac signal together with a slow changing dc bias is called the small-signal capacitance. This paper investigated the voltage dependence of the large- and small-signal capacitances. Measurements show that the large-signal C-V curve of thin-film ferroelectrics has much sharper peaks and higher peak values than the small-signal C-V curve. Analyses based on the Landau-Khalatnikov model shows that practical small-signal capacitance is …

Effect Of External Electrical Stimuli On Dna-Based Biopolymers, Guru Subramanyam, Carrie Bartsch, James Grote, Rajesh Naik, Lawrence Brott, Morley Stone, Angela Campbell

Guru Subramanyam

Biopolymers, such as deoxyribonucleic acid-hexadecyltrimethyl ammonium chloride (DNA-CTMA) and bovine serum albumin-polyvinyl alcohol (BSA-PVA), were studied using a novel capacitive test structure. A variety of external electrical stimuli were applied, including a low frequency alternating current signal and a rf/microwave frequency signal combined with a DC bias. The dynamic responses of the DNA-based biopolymer to the external stimuli are presented in this paper. The electrical transport measurements support the space-charge-limited conduction and the low frequency capacitance–voltage (CV) measurements showed large depletion layer capacitance at the Au–biopolymer interface, at 20 Hz, and the capacitance approaching bulk values at 1 MHz. Electric …

Thermally Controlled Vanadium Dioxide Thin Film Microwave Devices, Guru Subramanyam, E. Shin, D. Brown, H. Yue

Guru Subramanyam

No abstract provided.

Design Of A Si Mmic Compatible Ferroelectric Varactor Shunt Switch For Microwave Applications, Faruque Ahamed, Guru Subramanyam

Guru Subramanyam

This paper describes a capacitive shunt switch, based on ferroelectric varactors as a potential replacement for RF MEMS switches for microwave applications. Our implementation is based on a coplanar waveguide (CPW) transmission line shunted by a ferroelectric varactor. The novelty in the implementation comes from the elimination of any moving parts (as in MEMS switches) for switching. The concept of switching ON and OFF is based on the dielectric tunability of the ferroelectric material of barium strontium titanium oxide (BST) thin-films. From electromagnetic simulations performed, the isolation of the switch between 20 and 40 GHz (OFF state S21) is better …

Rf Performance Evaluation Of Ferroelectric Varactor Shunt Switches, Guru Subramanyam, Faruque Ahamed, Rand Biggers, Robert Neidhard, Edward Nykiel, John Ebel, Richard Strawser, Keith Stamper, Mark Calcatera

Guru Subramanyam

No abstract provided.

Ferroelectric Batio3/Srtio3 Multilayered Thin Films For Room-Temperature Tunable Microwave Elements, Ming Liu, Chunrui Ma, Gregory Collins, Jian Liu, Chonglin Chen, Andy D. Alemayehu, Guru Subramanyam, Ying Ding, Jianghua Chen, Chao Dai, Yuan Lin, Melanie W. Cole

Guru Subramanyam

Ferroelectric BaTiO3/SrTiO3 with optimized c-axis-oriented multilayered thin films were epitaxially fabricated on (001) MgO substrates. The microstructural studies indicate that the in-plane interface relationships between the films as well as the substrate are determined to be (001)SrTiO3//(001)BaTiO3//(001)MgO and [100]SrTiO3//[100]BaTiO3//[100]MgO. The microwave (5 to 18 GHz) dielectric measurements reveal that the multilayered thin films have excellent dielectric properties with large dielectric constant, low dielectric loss, and high dielectric tunability, which suggests that the as-grown ferroelectric multilayered thin films can be developed for room-temperature tunable microwave elements and related device applications.

A Reconfigurable Cpw Bow-Tie Antenna Using An Integrated Ferroelectric Thin Film Varactor, K. C. Pan, Dustin Brown, Guru Subramanyam, R. Penno, H. Jiang, C. H. Zhang, M. Patterson, David Kuhl, Kevin Leedy, Charles Cerny

Guru Subramanyam

A novel printed antenna with a frequency reconfigurable feed network is presented. The antenna consists of a bowtie structure patch radiating element in the inner space of an annulus that is on a nongrounded substrate with a ferroelectric (FE) Barium Strontium Titanate (BST) thin film. The bowtie patch is fed by a coplanar waveguide (CPW) transmission line that also includes a CPW-based BST shunt varactor. Reconfiguration of the compact 8 mm × 8 mm system has been demonstrated by shifting the antenna system’s operating frequency 500 MHz in the 7–9 GHz band by applying a DC voltage bias.

Large Area Bst Thin Films For Microwave Applications Deposited By Pulsed Laser Ablation, C. Varanasi, K. Leedy, D. Tomich, Guru Subramanyam

Guru Subramanyam

Large area Ba1 − xSrxTiO3 (BST) thin films with x = 0.4 or x = 0.5 were deposited on 75 mm diameter Si wafers in a pulsed laser deposition (PLD) chamber enabling full-wafer device fabrication using standard lithography. The deposition conditions were re-optimized for large PLD chambers to obtain uniform film thickness, grain size, crystal structure, orientation, and dielectric properties of BST films. X-ray diffraction and microstructural analyses on the BST films grown on Pt/Au/Ti electrodes deposited on SiO2/Si wafers revealed films with (110) preferred orientation with a grain size < 100 nm. An area map of the thickness and crystal …

Highly Efficient Quantum-Dot Light Emitting Diodes With Dna-Ctma As Combined Hole Transporting And Electron-Blocking Layer, Q. Sun, Guru Subramanyam, Liming Dai, M. Check, A. Campbell, Rajesh Naik, James Grote, Yongqiang Wang

Guru Subramanyam

Owing to their narrow bright emission band, broad size-tunable emission wavelength, superior photostability, and excellent flexible-substrate compatibility, light-emitting diodes based on quantum dots (QD-LEDs) are currently under intensive research and development for multiple consumer applications including flat-panel displays and flat lighting. However, their commercialization is still precluded by the slow development to date of efficient QD-LEDs as even the highest reported efficiency of 2.0% cannot favorably compete with their organic counterparts. Here, we report QD-LEDs with a record high efficiency (∼4%), high brightness (∼6580 cd/m2), low turn-on voltage (∼2.6 V), and significantly improved color purity by simply using deoxyribonucleic acid …

Enhanced Dielectric Properties Of (Ba,Sr)Tio3//Ba(Zr,Ti)O-3 Heterostructures With Optimized Structure Design, Ming Liu, Jian Liu, Chunrui Ma, Gregory Collins, Chonglin Chen, Andy Alemayehu, Guru Subramanyam, Jie He, Jiechao Jiang, Efstathios Meletis, Amar Bhalla

Guru Subramanyam

Environment-friendly ferroelectric Mn:BST//Mn:BZT heterostructures were epitaxially deposited on (001) MgO substrates by pulsed laser deposition with different combination ratios of Mn:BST over Mn:BZT, 2.5:7.5; 1:1; and 7.5:2.5. The microstructural studies indicate that the in-plane interface relationships between the heterostructures and the substrate are determined to be (001)Mn:BST//(001)Mn:BZT//(001)MgO and [100]Mn:BST//[100]Mn:BZT//[100]MgO. The Ku band microwave (15.5–18 GHz) dielectric property characterizations show that the dielectric constant, dielectric loss, and tunabilities of the heterostructures are highly dependent upon the sequences of Mn:BST to Mn:BZT. The optimized dielectric tunability with a low loss tangent was found to be 58.1%–74.4% under the combination ratio of 1:1 …

A New Ferroelectric Varactor Shunt Switch For Microwave And Millimeterwave Reconfigurable Circuits, Guru Subramanyam, Faruque Ahamed, Rand Biggers, Angela Campbell, Robert Neidhard, Edward Nykiel, Rebecca Cortez, Keith Stamper, Mark Calcatera

Guru Subramanyam

This paper presents a ferroelectric varactor shunt switch which can be useful for microwave/millimeterwave switching as well as for the design of reconfigurable circuits. The device operation is based on nonlinear dielectric tunability of a ferroelectric thin-film sandwiched between two metal layers in the parallel plate configuration. A CPW based design allows for MMIC compatible shunt switches with low insertion loss and high isolation. Experimental performance of the varactor shunt switch indicates good switching performance with ~24 dB isolation @41 GHz, and insertion loss below 7 dB up to 45 GHz.

Ferroelectric Thin-Film Based Two-Dimensional Electromagnetic Structures, U. Khan, Guru Subramanyam, S. Gevorgian, A. Vorobiev

Guru Subramanyam

A two-dimensional electromagnetic bandgap structure has been developed using ferroelectric thin-films. Using lumped inductors and parallel plate capacitors a planar structure is developed which creates a bandgap in the 20–40 GHz range, as demonstrated by experimental results. The ferroelectric material Ba0.6Sr0.4TiO3 (BST) is used in the form of a thin-film between patterned layers of gold to form capacitors on a 500 μm thick high-resistivity Si substrate. A meander line based design is used to form the two-dimensional surface which provides biasing pathways to the varactors. The concept is simulated and experimentally verified using a coplanar waveguide based device in which …

Performance Of Thin-Film Ferroelectric Capacitors For Emc Decoupling, Huadong Li, Guru Subramanyam

Guru Subramanyam

This paper studied the effects of thin-film ferroelectrics as decoupling capacitors for electromagnetic compatibility applications. The impedance and insertion loss of PZT capacitors were measured and compared with the results from commercial off-the-shelf capacitors. An equivalent circuit model was extracted from the experimental results, and a considerable series resistance was found to exist in ferroelectric capacitors. This resistance gives rise to the observed performance difference around series resonance between ferroelectric PZT capacitors and normal capacitors. Measurements on paraelectric (Ba,Sr)TiO₃-based integrated varactors do not show this significant resistance. Some analyses were made to investigate the mechanisms, and it was …

A New Capacitive Test Structure For Microwave Characterization Of Biopolymers, Carrie M. Bartsch, Guru Subramanyam, James Grote, Frank K. Hopkins, Lawrence L. Brott, Rajesh R. Naik

Guru Subramanyam

A new capacitive test structure, containing a parallel plate capacitor with coplanar waveguide feed lines, was used for microwave characterization of biopolymers for the first time. Microwave dielectric properties were obtained for the biopolymers as a function of dc bias and temperature by performing on-wafer microwave measurements. Dielectric tunability was observed with applied dc bias in the biopolymers tested.

A Memristor Device Model, Chris Yakopcic, Tarek Taha, Guru Subramanyam

Guru Subramanyam

This letter proposes a new mathematical model for memristor devices. It builds on existing models and is correlated against several published device characterizations. This letter identifies significant discrepancies between the existing models and published device characterization data. The proposed model addresses these discrepancies. In particular, it allows modeling of memristor-based neuromorphic systems.

Microwave Characterization Of Nanostructured Ferroelectric Ba0.6sr0.4tio3 Thin Films Fabricated By Pulsed Laser Deposition, Angela Campbell, Rand Biggers, Guru Subramanyam, Gregory Kozlowski, Richard Kleismit, Hollie Zate, Simon Hopkins, Bartek Glowacki, Bonnie Riehl, Timothy Peterson

Guru Subramanyam

A series of nanostructured ferroelectric thin films of barium strontium titanate were fabricated using a pulsed laser deposition system with real-time in situ process control. Pulsed laser deposition parameters were controlled during the growth of nanostructured thin films for use in the development of high frequency tunable microwave devices. The thin films were all grown at the same substrate temperature and laser beam energy density, but the chamber oxygen partial pressure (COPP) was varied systematically from 19 mTorr through 1000 Torr. Structural and electromagnetic characterization was performed using atomic force microscopy and evanescent microwave microscopy, respectively. Atomic force microscopy showed …

Microwave Dielectric Properties Of Dna Based Polymers Between 10 And 30 Ghz, Guru Subramanyam, E. Heckman, James Grote, K. Hopkins

Guru Subramanyam

Deoxyribonucleic acid (DNA) based polymer thin-films were characterized at microwave frequencies for the first time. The dielectric properties of the film were extracted from comparison of the propagation constants of the co-planar waveguide (CPW) lines on bare MgO substrates and the DNA based films on MgO substrates. The insertion loss introduced by the DNA film is only 0.1 dB at 10 GHz and 0.5 dB at 30 GHz. The relative dielectric constant of the DNA based film averages to four at microwave frequencies, and the loss-tangent was below 0.1 up to 30 GHz.

Closed-Form Expression For The Net Ground Plane Inductance Of Coplanar Stripline Pcbs, Li Huadong, Guru Subramanyam

Guru Subramanyam

The net ground plane inductance of printed circuit boards is the source of common-mode radiated emissions. Correct determination of the net ground plane inductance provides a quick estimation of the radiated emissions from printed circuit boards. Employing conformal mapping technique, this paper gives a closed-form expression for the per unit length net ground plane inductance of coplanar stripline printed circuit boards with finite ground plane width. Current density distribution on the ground plane is also obtained.

A Low Voltage Tunable Analog Phase Shifter Utilizing Ferroelectric Varactors, Guru Subramanyam, Kevin Leedy, Chakrapani Varanasi, Robert Neidhard, Keith Stamper, Mark Calcatera

Guru Subramanyam

A distributed transmission line phase shifter was implemented by periodically loading a coplanar transmission line using ferroelectric varactors in a shunt configuration. A single dc bias applied to the phase shifter circuit provides a large relative phase shift. A relative phase shift of ∼ 305 degrees was obtained at 20 GHz for a dc bias of only 5 V.

Generalized Memristive Device Spice Model And Its Application In Circuit Design, Chris Yakopcic, Tarek Taha, Guru Subramanyam, R. Pino

Guru Subramanyam

This paper presents a SPICE model for memristive devices. It builds on existing models and is correlated against several published device characterization data with an average error of 6.04%. When compared to existing alternatives, the proposed model can more accurately simulate a wide range of published memristors. The model is also tested in large circuits with up to 256 memristors, and was less likely to cause convergence errors when compared to other models. We show that the model can be used to study the impact of memristive device variation within a circuit. We examine the impact of nonuniformity in device …

Microwave Dielectric Properties Of Epitaxial Mn-Doped Ba(Zr,Ti)O-3 Thin Films On Laalo3 Substrates, Ming Liu, Chunrui Ma, Jian Liu, Gregory Collins, Chonglin Chen, Andy Alemayehu, Guru Subramanyam, Chao Dai, Yuan Lin, Amar Bhalla

Guru Subramanyam

Environmental friendly ferroelectric relaxor Ba(Zr0.2Ti0.8)O3 thin films with an additional 2% Mn dopant were epitaxially fabricated on the (001) LaAlO3 single crystal substrates by pulsed laser deposition. Microstructure characterizations from x-ray diffraction suggest that the films are c-axis oriented with the interface relationship of [101]Mn:BZT//[100]LAO and (001)Mn:BZT //(001)LAO. The microwave dielectric property measurements (13–17.5 GHz) reveal that the films have excellent dielectric properties with large tunability, high dielectric constant, and low dielectric loss, which the average value is 25.9%, 169 and 0.054, respectively. It is indicated that the additional 2% Mn doped Ba(Zr0.2Ti0.8)O3 thin films can be used for the …

Influence Of Space-Charge On Hysteresis Loop Characteristics Of Ferroelectric Thin Films, Huadong Li, Guru Subramanyam, S. Dey

Guru Subramanyam

Hysteresis loops of Pb(Zr, Ti)O3 (PZT) thin films obtained by using a Sawyer-Tower (ST) circuit are affected by many factors. This paper investigated the influence of space charge on the hysteresis loop of thin-film ferroelectrics, based on the model that polarization consists of two parts: linear and switching polarization. It is found that the space charge affects both the shape and offset of the ideal hysteresis loop. Further investigation shows that the practical hysteresis loop has a close relationship with the equivalent ST circuit parameters: the leakage resistance of the FE film, the equivalent input impedance of the measurement equipment, …

Miniaturized And Reconfigurable Cpw Square Ring Slot Antenna Loaded With Bst Thin Film Varactors, Hai Jiang, Mark Patterson, Dustin Brown, Chenhao Zhang, Kuanchang Pan, Guru Subramanyam, David Kuhl, Kevin Leedy, Charles Cerny

Guru Subramanyam

A novel miniaturized and reconfigurable coplanar waveguide (CPW) square-ring slot antenna is presented in this paper. The miniaturization is achieved via a hybrid approach including ferroelectric varactor loadings, high dielectric constant materials, and tuning stub for impedance matching. For the first time, nine shunt ferroelectric (FE) BST (Ba(1-x)SrxTiO3) thin film varactors are integrated with the CPW antenna structure achieving both antenna miniaturization and reconfiguration at the same time. The size of the miniaturized antenna is reduced to 0.067λ0 0.067λ0 without ground, and 0.1λ0 0.1λ0 with ground. The resonant frequency of the miniaturized antenna can be reconfigured from 5.3 GHz to …