Browsing by Author "Gupta, Navneet"

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Ab Initio Study of Carbon Nanotube Field Effect Transistor Gas Sensor for Detection of Ammonia and Nitrogen Dioxide Gas
(IEEE, 2022-07) Gupta, Navneet; Chaturvedi, Nitin
Lebel-free sensors are capable for sensing low concentration of gas molecules. In this article, the importance of Carbon Nanotube Field Effect Transistor (CNFET) is described for gas sensing application. The first principal study to investigate the CNFET to detection of low concentration of ammonia (NH 3 ) and nitrogen dioxide (NO 2 ) gas molecules. By discussing the electronic and transport properties of CNFET, we find that CNFET can be used for gas sensing applications. Detailed analysis of binding energy, e-k diagram, density of state (DOS), device density of state (DDOS), transmission pathways and current-voltage (I-V) characteristics configuration have been performed using density functional theory (DFT) and non-equilibrium green function (NEGF) method. It has been observed that CNFET can be used for the potential application of gas sensor at room temperature. Out theoretical findings are corroborated with experimental data and this virtual device structure can be converted into physical device to get nano dimensions integrated gas senso
Adaptation of a compact SPICE level 3 model for oxide thin-film transistors
(Springer, 2019-05) Gupta, Navneet; Kandpal, Kavindra
Oxide thin-film transistors (TFTs) and metal–oxide–semiconductor field-effect transistors (MOSFETs) operate via different conduction mechanisms but exhibit similar device characteristics. In this work, a SPICE level 3 model originally defined for MOSFETs is successfully adapted to provide a behavioral model for oxide TFTs. This adapted compact model is applicable to all kinds of oxide TFTs, irrespective of the channel and dielectric material used. To capture the TFT behavior efficiently, the experimental characteristic of an oxide TFT is used to set various SPICE level 3 parameters.
Analysis of Dielectric Properties of Polydimethylsiloxane (PDMS) as a Flexible Substrate for Sensors and Antenna Applications
(IEEE, 2021-06) Gupta, Navneet
In this paper, a complete analysis of the complex dielectric constant of a flexible substrate from the silicon-based polymer- Polydimethylsiloxane (PDMS) is performed, and the obtained results are discussed. Two experimental methods are applied in this research. The first Two-resonator method is based on resonance measurements by excitation of two types of TE- and TM-mode cylinder resonators with PDMS disks, ensure an accurate determination of the dielectric constant and dielectric loss tangent in both parallel and perpendicular directions (e.g., ε par and ε perp ). The second method is based on the tight coverage of planar microstrip ring resonators with non- metalized PDMS samples gives reliable information for the equivalent dielectric parameters (e.g., ε eq , tan δ εeq ). The obtained results show that PDMS substrates have relatively weak but measurable uniaxial anisotropy and well-expressed frequency dependencies of the extracted dielectric parameters in the range 1-40 GHz, namely ε par ~ 2.82-2.7; ε perp ~ 2.73-2.52 and ε eq ~ 2.75-2.64, tan δ εeq ~ 0.017-0.048. The results are confirmed by several other complementary methods. The considered pair of methods are also applied in the temperature interval-40/ + 70 ° C; the measured temperature dependencies on the dielectric parameters turn out to be relatively strong. The possible origin of the measured PDMS uniaxial anisotropy has been discussed; in fact, it appears mainly in the temperature range-30/ + 40 ° C.
Analysis of Graphene/SiO2/p-Si Schottky Diode by Current–Voltage and Impedance Measurements
(Springer, 2018-11) Gupta, Navneet
We explore the electrical properties of graphene–silicon dioxide–p–silicon Schottky junction diode using current–voltage characteristics and impedance analysis. Ideality factor, rectification ratio, and series resistance are extracted from the experimental data. A linear response of series resistance of graphene/SiO2/p-Si Schottky diode is observed with respect to change in forward bias voltage from 0 to 2 V.
Analytical Modeling for Spring Constant of Non-Uniform Serpentine Radio Frequency-Micro Electro Mechanical System Switch
(Ingenta, 2013-12) Gupta, Navneet
This paper presents an improved design of radio frequency (RF) microelectromechanical system (MEMS) switch having non-uniform serpentine flexure structure. An analytical modeling for spring constant of non-uniform serpentine flexure is obtained using small displacement theory. The spring constant computed analytically is compared with Finite Element Method (FEM). It is observed that in comparison to the uniform serpentine flexure reported so far, the proposed design shows a considerable decrease in spring constant
Analytical modeling of carrier transport through transverse and longitudinal grain boundaries in polysilicon thin-film transistors
(The National Institute of Science Communication, 2006) Gupta, Navneet
Carrier transport through transverse and longitudinal grain boundaries (GBs) in polysilicon thin film transistors (poly-Si TFTs) has been studied. The model considers an array of square grains in the channel of poly-Si TFT in which current flows along the longitudinal GBs and through the grains and the transverse GBs. The variation of field-effect mobility (HFE) and drain current (ID) is computed for different values of grain size. This study reveals that at low gate voltage the longitudinal GBs are seen to influence the field-effect mobility and drain current. As gate voltage increases, the effect of transverse GBs is found to account for experimental results. This is attributed to the fact that at low gate voltage, the carriers moving through longitudinal GBs have more opportunities to be trapped at the trapping sites and as gate voltage increases the carriers have sufficient energy to bypass the longitudinal GBs and obstructed by transverse GBs alone. This may be the reason that the calculated effects of longitudinal GBs do not appear in the experimental results at high gate voltage
Bandwidth and Gain Enhancement Technique for Gammadion Cross Dielectric Resonator Antenna
(Springer, 2015-07) Gupta, Navneet
In this paper, a novel slot-technique is presented to enhance the bandwidth and gain of dielectric resonator antenna (DRA) with two different geometries. First geometry of DRA is Gammadion Cross DRA with semi-cylindrical slots (GCDRA-1), and the other is Gammadion Cross DRA with rectangular slots (GCDRA-2). It is found that the cutting slots can be used to widen the DRA bandwidth or to tune the DRA frequency. Iterations of cutting slot in dielectric resonator are embedded on single structure of DRA. The new Gammadion Cross structure of proposed DRA offers a good impedance bandwidth of 31.6 % for |S11| < −10. In addition, the proposed antenna has a quite higher and more stable gain. The peak gain of proposed antennas is ~7 dBi at 5.1 GHZ. The antenna covers most of wireless systems like C-band, 5.2, 5.5 and 5.8 GHz-WLAN and Wi-MAX applications. The simulation process has been done using CST Microwave Studio™. It is observed that the new proposed Gammadion Cross configuration (GCDRA-2) reduces the DRA volume by 50 % and at the same time enhances the bandwidth from 10 to 31.6 % for |S11| < −10 than the reference antenna. The performance parameters of proposed DRA like reflection coefficient, peak gain and impedance bandwidth has been evaluated and verified these finding with two different Gammadion Cross DRA structures.
Carbon Nanotube Field-Effect Transistors (CNFETs): Structure, Fabrication, Modeling, and Performance
(Springer, 2021-05) Gupta, Navneet
The problems associated with attempting to scale down traditional metal oxide field-effect transistors (MOSFET) have led researchers to look into CNT-based field-effect transistors (CNFETs), as an alternative. Though the scaling of MOSFET has been the driving force toward the technological advancement, but due to continuous scaling, various secondary effects which include short channel effects, high leakage current, excessive process variation, and reliability issues degrade the device performance. On the other hand, CNFETs are not subjected to the scaling problems. The operation principle of the CNFET is similar to traditional MOSFET but the conduction phenomena are different. The traditional MOSFETs are based on the drift and diffusion phenomena in which channel length is very large as compared to mean free path of charge carriers whereas the CNFETs are based on ballistic transport conduction mechanism, in which channel length is very small as compared to mean free path of charge carriers. In CNFET, electrons are injected from source to drain and transported through the nanotubes without scattering. Due to ballistic transport the nanotubes act as a perfect conductor for electrons such that the full quantum information of these electrons (momentum, energy, spin) can be transferred without losses. The channel current in CNFETs depends on gate voltage, number of nanotubes in channel, dielectric material and its thickness, and diameter and chirality of carbon nanotubes. So in this chapter we shall discuss different device structures of CNFET, steps involved in the fabrication of CNFETs, advantages and limitations of various methods involved in the synthesis of CNTs, conduction models, and performance parameters.
Characterization of polydimethylsiloxane (PDMS) as a wearable antenna substrate using resonance and planar structure methods
(Elsevier, 2020-12) Gupta, Navneet
In this paper, a flexible silicon-based elastomer Polydimethylsiloxane (PDMS) is characterized experimentally. For the characterization of the dielectric properties of PDMS, two experimental methods are applied. The first method is based on resonance measurements by the two-resonator method. This method allows the determination of the dielectric constant εr and dielectric loss tangent tanδεr of non-metallized samples in both parallel and perpendicular directions. The obtained values for the dielectric constants differ; εr_par ~ 2.71 (12–36 GHz) and εr_perp ~ 2.558 (6–29 GHz). This material has a weak but measurable anisotropy ~5.7%. The second method is based on the application of different planar structures (resonators and transmission lines) by integrating the PDMS samples without metallization. The proposed two methods give the average value of equivalent isotropic dielectric constant εeq, as equals to 2.66 (εr_par > εeq > εr_perp) and equivalent dielectric loss tangent tanδε_eq, as equals to 0.023 in the frequency interval 2–36 GHz. The results obtained by the analysis of PDMS samples are compared with results for isotropic Polytetrafluoroethylene (PTFE) and Cyclo Olefin Polymer (COP) samples. The analysis performed experimentally proves that PDMS is a good choice as a wearable antenna substrate.
Chemiresistive urea sensor based on a composite film of Activated charcoal and Zinc Oxide
(IEEE, 2024) Mishra, Puneet; Gupta, Navneet; Panwar, Jitendra; Mathur, Hitesh Datt
Detection of nitrogen content in the form of urea is essential as it confirms its fertility for agricultural practices. Herein, a report on a simple microwave decomposition method for the synthesis of hybrid nanomaterial (Zinc Oxide and Activated Charcoal) that shows a maximum sensitivity of ~87% at 100mM urea concentration with response time and recovery time of 6 min and 80 min, respectively. The urea sensing mechanism with pre-adsorbed oxygen ions on the surface of the composite was verified by measuring the change in intensity of CO2 signal upon exposure to urea solution using FTIR. Thus, the composite film acts as a low-cost non-enzymatic chemiresistive urea sensor with good sensitivity and reproducibility.
A Compact Model of Gate Capacitance in Ballistic Gate-All-Around Carbon Nanotube Field Effect Transistors
(MERC, 2021) Gupta, Navneet
This paper presents a one-dimensional analytical model for calculating gate capacitance in Gate-All-Around Carbon Nanotube Field Effect Transistor (GAA-CNFET) using electrostatic approach. The proposed model is inspired by the fact that quantum capacitance appears for the Carbon Nanotube (CNT) which has a low density of states. The gate capacitance is a series combination of dielectric capacitance and quantum capacitance. The model so obtained depends on the density of states (DOS), surface potential of CNT, gate voltage and diameter of CNT. The quantum capacitance obtained using developed analytical model is 2.84 pF/cm for (19, 0) CNT, which is very close to the reported value 2.54 pF/cm. While, the gate capacitance comes out to be 24.3×10-2 pF/cm. Further, the effects of dielectric thickness and diameter of CNT on the gate capacitance are also analysed. It was found that as we reduce the thickness of dielectric layer, the gate capacitance increases very marginally which provides better gate control upon the channel. The close match between the calculated and simulated results confirms the validity of the proposed model.
A Comparative Study of Different Feeding Mechanisms for Rectangular Dielectric Resonator Antenna
(SSRN, 2015-10) Gupta, Navneet
The paper describes the performance analysis of different feeding mechanisms for Rectangular Dielectric Resonator Antenna (RDRA). Due to the variety of feeding mechanisms available to antenna designers such as microstrip line fed, coaxial probe fed, Co-Planar Waveguide (CPW) fed and slot/aperture couple fed, a proper practice to select the best possible feeding mechanism is required. In this paper, an RDRA is used to investigate the performance of different feeding mechanisms-based antenna systems. These feeding techniques give a better understanding of design parameters of an antenna and their effect on return losses, bandwidth, VSWR and resonant frequency.
A Comprehensive Review of Unmanned Aerial Vehicle Attacks and Neutralization Techniques
(Elsevier, 2021-02) Gupta, Navneet; Chamola, Vinay
Unmanned Aerial Vehicles (UAV) have revolutionized the aircraft industry in this decade. UAVs are now capable of carrying out remote sensing, remote monitoring, courier delivery, and a lot more. A lot of research is happening on making UAVs more robust using energy harvesting techniques to have a better battery lifetime, network performance and to secure against attackers. UAV networks are many times used for unmanned missions. There have been many attacks on civilian, military, and industrial targets that were carried out using remotely controlled or automated UAVs. This continued misuse has led to research in preventing unauthorized UAVs from causing damage to life and property. In this paper, we present a literature review of UAVs, UAV attacks, and their prevention using anti-UAV techniques. We first discuss the different types of UAVs, the regulatory laws for UAV activities, their use cases, recreational, and military UAV incidents. After understanding their operation, various techniques for monitoring and preventing UAV attacks are described along with case studies.
Concept of Engineering Physics
(Dhanpat Rai, 2018) Gupta, Navneet
A CPW-Fed Circular SRR-Inspired Flexible Antenna Using Polydimethylsiloxane (PDMS) Substrate for WLAN and WBAN Applications
(IEEE, 2022-01) Gupta, Navneet
This article presents a 50×40 mm 2 coplanar waveguide (CPW)-fed triple-band flexible antenna operating at 5, 5.8, and 6.6 GHz for wireless local area network (WLAN) and wireless body area network (WBAN) applications. In the proposed design, polydimethylsiloxane (PDMS) is used as a substrate with a dielectric constant εr of 2.65 and a loss tangent tan δεr of 0.02. In addition to the rectangular slot on the ground, the presented antenna has a single circular split-ring resonator (SRR) structure on the same side of the patch. This provides the required frequency notched characteristics for the targeted frequency bands, compactness, minimize losses, and backward radiation when used in close proximity to the human body. The proposed flexible antenna provides stable results in terms of performance parameters and specific absorption rate (SAR). We have also investigated the antenna under different operating conditions of moisture and bending. There exists a strong correlation between the simulation and measured findings.
Design and enhancing performance of lead-free flexible perovskite solar cells: a numerical approach
(IEEE, 2025-02) Gupta, Navneet
Lead-free perovskite materials have emerged as the most feasible option for photovoltaics to address the issue of toxicity and better performance. This study aims to design and enhance the performance of lead-free methylammonium (MA) and formamidinium (FA) compound (FAMASnGeI3)-based flexible perovskite solar cell (FPSC) by utilizing the solar cell capacitance simulator 1-D (SCAPS-1D). The optimization of various geometrical parameters and charge densities of the absorber and charge transport layers show the improvement in power conversion efficiency (PCE). We have obtained Voc of 0.87V, Jsc of 45.7 mA/cm2, fill factor (FF) of 75.3%, and PCE of 29.9%. The obtained results were compared with similar existing research based on various absorber layers. It was found that the selected absorber layer improves the performance of FPSCs.
Design and simulation of energy efficient OLEDS for flexible electronics applications
(IEEE, 2025-05) Gupta, Navneet
Organic Light Emitting Diodes (OLEDs) are a promising technology known for their thin, energy-efficient, and high-quality light emission, making them ideal for displays and lighting applications. Flexible OLEDs, an emerging development from conventional rigid OLEDs, can be integrated into curved or bendable surfaces, enabling new design possibilities in wearable electronics, foldable screens, and innovative lighting solutions. In this work, we designed and simulated a multilayer OLED structure using TCAD (Technology Computer-Aided Design) software, focusing on material selection for the emission layer to optimize energy efficiency and performance. Three candidate materials—Alq3, PPV, and PFO—were evaluated, with PFO demonstrating superior luminescent power and energy efficiency. Through geometry optimization of the PFO layer, we achieved an energy efficiency of 14.08%, highlighting its potential as a suitable alternative to Alq3 for flexible OLED applications.
Design, optimization and analysis of reconfigurable antenna using RF MEMS switch
(Springer, 2020-03) Gupta, Navneet
This paper presents the design, optimization and analysis of a novel radio-frequency micro electromechanical system (RF MEMS) switch for reconfigurable antenna. The proposed antenna operates at frequency band from 4.5 to 12.5 GHz. The antenna is created by reconfiguring its size using a rectangular patch and an inverted U shaped patch via RF MEMS switch. A series metal to metal contact RF MEMS switch is designed and optimized for low actuation voltage with adequate switching speed and excellent RF characteristics. The design of RF MEMS switch is simulated using CoventorWare and RF analysis is performed on Ansys HFSS software. Pull in voltage obtained for the switch is 5.7 V with switching time of 38.7 μs. The isolation obtained is better than − 20 dB for DC to 25 GHz. Insertion loss is less than − 0.4 dB for DC to 60 GHz and return loss is also better than − 23 dB for DC to 60 GHz. Further the designed reconfigurable antenna is simulated using Ansys HFSS software. The antenna is reconfigurable at 4.5 GHz, 8.6 GHz, 9 GHz, 12.3 GHz, 12.4 GHz and 12.5 GHz for different switch positions.
Development and Analysis of Graphene Nanoplatelets (GNPs)-Based Flexible Strain Sensor for Health Monitoring Applications
(IEEE, 2020-11) Gupta, Navneet
Recently,flexible electronic devices have gained tremendous research interest owing to their wide range of applicationssuch as humanmotion detection, healthmonitoring and electronic skin (E-Skin). Particularly, the development of skin-like flexible strain sensors is gradually increasing for the realization of multipurpose human-machine interfaces. This paper aims to propose a simplemethod ofmanufacturing flexible graphene-based strain sensors with high sensitivity. Herein, a novel flexible resistive-strain sensor based on graphene nanoplatelets (GNP)/PDMS has been reported that providesgood strain sensitivity,stretchabilityup to 65%with a gauge factor of 62.5, indicating typical piezo-resistive characteristics. The fabricated sensor is attached to the human body, it works as a health-monitoring device by detecting various human motions such as human wrist pulse measurement, the finger bendingmovement and in addition to the flexible pipe bending. This work presents fabrication, characterization and comparative study of four different types of GNP wrist pulse sensors. Therefore, with its simple structure and low cost processing coupledwith reasonably good piezo-resistive behavior, it has great potential in wearable electronics, viz. human motion detection and health monitoring applications.
Dielectric material selection of microstrip patch antenna for wireless communication applications using Ashby's approach
(Cambridge University Press, 2014-07) Gupta, Navneet; Kumar, Rajneesh
In this paper, material selection has been done for dielectric substrate material in microstrip patch antenna (MPA) for three distinct classes of wireless communication applications using Ashby's approach. This material selection procedure is based on the creation and evaluation of Ashby's chart of different material indices. These material indices in turn affect the device performance indices, which decide the best possible dielectric material to be used as substrate for MPAs. In this work, quality factor, relative permittivity, and temperature coefficient of resonant frequency are chosen as material indices of MPA's dielectric substrate to get relevant performances. Ashby's selection chart shows that 0.75MgAl2O4–0.25TiO2 material for millimeter waves applications, Ca[(L1/3Nb2/3)0.85Ti0.15]O3−δ for mobile base station applications, and (Ba0.95Ca0.05)O–Sm2O3–4.5TiO2 ceramic for mobile phone miniaturization applications are the promising materials that allows best overall performance in MPAs for wireless communication.