Department of Electrical Engineering

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BiFeO3 based resistive random access memory (RRAM) devices are fabricated using a low-cost solution process to study the effect of an Al top electrode on switching behavior and reliability. Fabricated devices demonstrated bipolar switching characteristics with a moderate Ion/Ioff ratio, set and reset voltages of ∼-1.3 V and ∼0.8 V, DC and AC endurance of more than 250 cycles and 7100 cycles, respectively, and a retention time of over 104 s, confirming the non-volatile resistive switching behavior. The ohmic and trap filled space charge limited conduction dominates the conduction mechanism in the devices at lower and higher voltages, respectively. Moreover, impedance spectroscopy measurements substantiate the presence of an AlOx layer at the Al/BiFeO3 interface resulting from the Al-O interaction at the junction, which is the possible rationale of reliable complementary switching in these RRAM devices. The switching mechanism is elucidated using the formation and rupture of the oxygen vacancy mediated filament, assisted by the participation of a thin AlOx layer at the Al/BFO interface. The role of the thin AlOx layer is explained by modeling of impedances. © 2020 Author(s).

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Department of Physics

Fulltext

AIP Advances

Interfacial layer assisted, forming free, and reliable bipolar resistive switching in solution processed BiFeO3 thin films

This study reports for the first time an operation of an outdoor algae assisted Microbial Fuel Cell (MFC). The MFC (10 L) comprised of low-cost materials like rock phosphate blended clayware &amp; low-density polyethylene bags as anodic &amp; cathodic chamber respectively. Algae biomass after lipid extraction at 2 g/l served as electron donor at the anode. Chlorella vulgaris at cathode provided oxygen as electron acceptor and served as lipid source. The MFCs performed well in all aspects namely energy recovery, algae productivity, and cost of operation. The 5% RP-MFCs gave 0.307 kg/m3d algal productivity, 0.09 kg/m3d lipid productivity, and 11.5318 kWh/m3 of net energy recovery (NER). Rock phosphate served as a slow and constant source of phosphorus supporting algae growth. Proteobacteria (45.14%) were the dominant phyla while Alicyliphilus (5.46%) and Dechloromonas (4.74%) were the dominant genera at the anode. The estimated cost of the system was $11.225 only. © 2020 Elsevier Ltd

Department of Bioscience & Bioengineering

Bioresource Technology

Performance evaluation of algae assisted microbial fuel cell under outdoor conditions

High-performance flexible organic field-effect transistors with natural protein gelatin as a dielectric layer and solution-processed TIPS-pentacene as an active layer were fabricated on a flexible poly(ethyleneterephthalate) substrate. The fabricated devices exhibited high performance and electromechanical stability, demonstrating high field-effect mobility with near-zero threshold voltage and the Ion to Ioff ratio approaching 105 with a low operating voltage of -5 V. Devices exhibited highly stable electrical characteristics under multiple transfer scan measurements. The flexible nature of these devices was tested through the tensile strain test by subjecting them to a 5 mm bending radius. High electromechanical stability was observed with minuscule variation in the electrical parameters under strain application. These flexible devices were demonstrated for circuit and sensing applications. Under the humidity exposure test, the devices responded quickly with rapid response and recovery time and acted as a humidity sensor. This property was utilized for real time health monitoring applications by testing these devices as a breath rate analyzer. In addition, to test the credibility of these flexible devices in circuit applications, the external load invertor circuits were demonstrated before and after applying strain to these devices. © 2020 American Chemical Society

ACS Applied Electronic Materials

Solution-processed flexible organic field-effect transistors with biodegradable gelatin as the dielectric layer: An approach toward biodegradable systems

Optical packet switch/optical interconnect will be an integral part of high speed switching and datacenter applications. In recent past Arrayed Waveguide Grating (AWG) based designs have shown promising solutions for contention resolution and packet routing. Most of the designs take the advantage of wavelength parallelism and wavelength-based routing nature of AWG. In general, two classes of design have emerged: buffer-less and with buffer. In recent past the concept of All-Optical Negative Acknowledgement (AO-NACK) is introduced in case of buffer-less design. Here, in case of dropping of packet a negative acknowledgement is sent back to the sender to retransmit the packet. The drawback of the scheme is that the numbers of retransmitted packets are huge in buffer-less design. In this paper, a buffer-based design is presented where both buffer and negative acknowledgement areutilized to reduce the number of transmitted packets to 3000 times compared with buffer-less design, in case of transmission of 10(6) packets Moreover, negative acknowledgement hardware design is simplified significantly.

JOURNAL OF ENGINEERING RESEARCH

Optical Data Centers Router Design with Fiber Delay Lines and Negative Acknowledgement

Performance of symmetric lateral doping-free bipolar junction transistor (BJT) on silicon on insulator (SOI) in universal gates and ring oscillator were investigated. Charge carriers in SOI at emitter and collector regions are induced with two unique approaches, i.e., the charge plasma (CP) and polarity control (PC). Four types of devices (CP-NPN, CP-PNP, PC-NPN, and PC-PNP) was used for bipolar CMOS type NAND and NOR gates. Excellent transient response with rise and fall time less than 5 ns and propagation delay less than 2.4 ns were obtained. © 2020 IEEE.

2020 IEEE Silicon Nanoelectronics Workshop, SNW 2020

Performance Investigation of Universal Gates and Ring Oscillator using Doping-free Bipolar Junction Transistor

This paper describes the design of a new excitation technique known as the Substrate Integrated Coaxial Line (SICL) technology for bow tie antenna operating in Millimeter wave (MM-wave) frequency. Substrate Integrated Coaxial Line provides wide bandwidth for TEM mode of operation. The Bow Tie antenna excited by SICL exhibits a wide 10 dB impedance bandwidth of 8.7 GHz with an average gain of 4.5 dBi in the entire frequency band. One advantage of using this new feeding technique is the elimination of balun as required in the microstrip technology to feed the antenna. Another advantage is the wideband nature of SICL that is difficult to be obtained with its counterpart namely, SIW (Substrate Integrated Waveguide). The end-fire radiation pattern of the proposed antenna shows co-polarization to cross polarization ratio of 13.7 dB at the center frequency. The antenna is suitable for 5G applications at millimeter wave frequencies beyond 24 GHz and applications at LMDS band. © 2020 Indian Radio Science Society.

2020 URSI Regional Conference on Radio Science, URSI-RCRS 2020 - Proceedings

Substrate Integrated Coaxial Line Excited Wideband Millimeter Wave Bow-Tie Antenna

This study presents a wideband crossover developed using substrate integrated coaxial line (SICL) technology. The proposed SICL-based crossover isolates the two physically overlapping channels by routing the signal in a middle conductor of SICL through the transmission line created in the top and bottom ground plane using a metalised blind via. An equivalent model is proposed to study the role of substrate height in the proposed crossover. The design methodology is affirmed by fabricating and testing the experimental prototype. The measured results show isolation between channels are more than 19 dB with better than 18 dB return loss and less than 1.2 dB insertion loss from 0.2 to 20 GHz. Owing to the non-dispersive nature of SICL line and simplistic design technique with minimal discontinuities the designed crossover demonstrates low peak-to-peak group delay variation, less than 0.04 ns over the entire bandwidth. The proposed crossover due to its symmetric design provides low path difference of less than ±2.45° up to 20 GHz (≤ ±1° up to 10 GHz) without any additional phase compensation technique. Utilization of electromagnetically robust self-packaged components designed in SICL technology provides superior front-end communication system within a small footprint. © The Institution of Engineering and Technology 2020

IET Microwaves, Antennas and Propagation

SICL-based wideband crossover with low phase imbalance and group delay

Radiation induced changes in the electrical properties of PbZrTiO3 (PZT) thin films have been studied for dosimetry application. The radiation detection was based on radiation induced changes in the electrical properties under the influence of gamma radiation. Epitaxial heterostructure of ferroelectric PbZr0.52 Ti0.48O3 (001)/SrRuO3 (SRO) were grown on single crystal SrTiO3 (001) substrates by pulsed laser deposition and platinum (Pt) electrode was deposited on top of the PZT film. The maximum capacitance of the heteroepitaxial capacitor devices was \approx ~25 pF with a corresponding small leakage current. The effect of gamma ( \gamma-ray) irradiation on the intrinsic electrical behavior of the Lead Zirconate Titanate (PZT) capacitor devices were explored in form of the current-voltage (I-V) and capacitance-voltage (C-V) properties. The PZT devices were exposed to a 60Co Gamma source with 2.8 kGy/h dose rate from 0 kGy to 400 kGy doses. Gamma radiation induced broadening was observed in full width half maxima (FWHM) of the x-ray diffraction (00l) peak with the increasing gamma doses. All devices showed a consistence changes in conductance and capacitance with increasing gamma doses. The results demonstrated linear relationship in electrical response of PZT thin-film capacitors as a function of gamma doses. The device showed significant changes in the values of current and capacitance with the increase in dose up to 400 kGy and are therefore suitable for high-dose dosimetry applications. © 1980-2012 IEEE.

IEEE Electron Device Letters

Gamma radiation detection response of pt/pzt/sro based capacitor for dosimetry application

Here, an ultrafast direct laser patterning technique to fabricate a low-cost microsensor and its application for formaldehyde detection are reported. The patterns of microheater and interdigitated electrodes (IDEs) were realized using laser micromachining techniques by ablation of gold thin film on alumina substrate. The thin film of gold microheater showed good stability up to 300 °C with a fast response time of 80 s and temperature coefficient of resistance (TCR) was calculated as $1.37\times 10^{-{3}}/^{\circ }\text{C}$. Moreover, gold microheater exhibited long-term reliability under self-heating mode with a negligible resistance drift < 0.5% over a period of 330 h at 250 °C through consuming low power with a heating efficiency of 0.23 °C/mW. Thermal imaging camera revealed the uniform temperature distribution with negligible heat gradient profile over the whole microsensor platform. To state-of-the-art gas sensing application of this coplanar sensing platform, a nanostructured SnO2 was deposited on IDE, which exhibited high sensitivity (13.96% ppm $^{-{1}}$ ) to formaldehyde even to detect sub-ppm concentrations with fast response (32 s) and recovery kinetics (72 s). Moreover, the microsensor was also used on-site rapid screening for the detection and quantification of formaldehyde concentration in formalin-treated fish sample. © 1963-2012 IEEE.

IEEE Transactions on Electron Devices

Fabrication of Microsensor for Detection of Low-Concentration Formaldehyde Gas in Formalin-Treated Fish

Surface micromachined devices are known to have residual stress-induced deformation. This paper presents the effects of residual stress on the flatness of an electrothermally actuated large aperture MEMS bilayer platform. The platform consists of a SiO2–Al composite plate of area 500 × 500 μm2 suspended over a cavity through bimorph actuators. The bilayer platform consists of 0.95 μm thick aluminum film on a thermally grown 0.75 μm thick silicon dioxide on a silicon substrate. Bimorph actuators also consist of laminated layers of silicon dioxide and aluminum of thicknesses the same as on the platform. The ensuing compressive stress in silicon dioxide (240 MPa) &amp; tensile stress in aluminum (35 MPa) manifests itself in significant post-release curling of the bilayer platform. Finite Element Simulation is done in Coventorware® to analyze the room temperature post-release deformation behavior of the platform. In order to correct the platform curvature, two methods of stress counterbalancing i.e. (i) metal reinforcement framing, and (ii) deposition of a stress compensation layer are proposed and their effectiveness is investigated using FEM simulations. The simulation results show that a 1 μm thick gold reinforcement frame results in a 13 μm peak-to-valley height difference between center and corner of the platform, which improves to 6 μm for a gold reinforcement thickness of 3 μm. The maximum height difference reduces to 1 μm for silicon dioxide of thickness 0.75 μm. According to FEM results, the presence of a stress compensation layer at the top is more effective in curvature correction compared to metal reinforcement framing; however, the post-release elevation of the stress-compensated platform is 5 μm below the post-release elevation of the reinforced platform and 25 μm below the zero reference plane. To verify the simulation results, the platform is fabricated with a deposition of 1 μm thick silicon dioxide layer at the top. The fabricated platform exhibit significant improvement in post-release deformation with a stress compensation layer compared to an unbalanced platform. © 2019 Elsevier B.V.