Faculty Publications
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Item The effect of etching time on structural properties of Porous silicon at the room temperature(Elsevier Ltd, 2016) Ramesh, M.; Nagaraja, H.S.Nano-porous silicon (PS) layers have been prepared by electrochemical etching of (100) silicon wafer in the solution of hydrofluoric acid (HF) and ethanol (C2H5OH). In this paper, XRD and FTIR confirm the formation of PS. The size of crystallites in the porous Si layers was found from XRD, which isaround ~2.4 nm. The evolution of morphology of PS as a function of etching time is imaged using SEM. The average pore-diameter has been calculated from the image j software, which is in the range of 238-1117nm. The Raman spectra reveal that the peak intensities sharply increase with etching time due to presence of nancrystals on the surface of PS. It was observed that the peak of Raman signal was around ~520.5cm-1. Luminescence studies revealedthat the strong photoluminescence emission was observed at about ~660nm. It possesses a broad red emission band on the surface of PS due to the growth of Si=O bonds and the formation of silicon hydrides (SiHx), which is caused to trapped electron states at the interface between the crystalline Si and SiO2. © 2016 Elsevier Ltd.Item Effect of current density on morphological, structural and optical properties of porous silicon(Elsevier Ltd, 2017) Ramesh, R.; Nagaraja, H.S.The morphology of porous silicon (PS) layers produced by electrochemical etching of n-type (100) silicon (Si) at different low current densities was studied using SEM, image J analysis and WSxM software. From FTIR spectroscopy analysis, the Si dangling bonds of the as-prepared PS layer have large amount of Hydrogen to form weak Si–H bonds. From Raman analysis, a full width half maximum (FWHM) of the Raman peak was gradually increased with increased current density, shifted towards lower energies due to reduce of crystallite size, the crystallite size in the PS varied from 63 nm to 20 nm depending on the current density. The optical response of the PS layer has been performed by the absorbance and Photoluminescence was studied experimentally in the visible range. The optical absorption and photo luminescence in PS is due to excitonic recombination between the defect states as well as on the surface of nanocrystals, and this was attributed to the presence of silicon hydride species which are confirmed by FTIR spectra. The red shift was observed in absorbance and Photoluminescence due to decrease in the size of Si crystallites and growth of Si=O bonds. The contact angle varied from 76° to 120.1°. From the wettability studies, the surface nature of the PS was converted from hydrophilic to hydrophobic when the current density increased. © 2017 Elsevier LtdItem Porous-Silicon Assisted Hybrid Plasmonic Slot Waveguide Based On-Chip Ethanol Sensor(Institute of Electrical and Electronics Engineers Inc., 2022) Reddy, S.K.; Singh, M.Refractive index (RI) sensors have an overarching compass jutting into the biological and chemical fields and hence are efficacious. The evinced work appertains with an infra-red (IR)-band ethanol sensor, perceived with a Metal-Insulator-Semiconductor-Insulator-Metal (MISIM) waveguide structure consisting of porous-silicon as the absorbing/sensing medium. It is validated through modeling, and numerical simulations that the enhanced electric field confined into a low index slot undergoes a red-shift in wavelength in the presence of harmful ethanol. The red-shift in wavelength can be controlled by changing the silicon porosity and the physical dimensions of the hybrid waveguide. With finite-element-method based COMSOL Multiphysics simulations, we have obtained the optimized metrics of the sensor namely sensitivity (S TM) = 400.43-612.43 nm/RIU, figure of merit (FoM) = 12.42-19.46/RIU, and quality factor (Q-factor) = 46.8-52.9, for 10% to 25% p-Si porosity. The fabrication stages of the on-chip sensor are also articulated in brief. The detailed assessment shows that this sensor is a feasible choice for ethanol detection in hazardous environments. © 2001-2012 IEEE.Item Sensitivity improvement of photonic crystal refractive index sensor using porous silicon nano rods(Elsevier Ltd, 2023) Mehta, S.; Vankalkunti, S.; Kachhap, P.K.; Gautam, P.R.; Singh, M.This work proposes a photonic crystal refractive-index sensor for detecting volatile organic compounds (VOC). Two sensor designs are analyzed with Y-splitter photonic crystal waveguide using the finite-difference time-domain (FDTD) method. Also, simultaneous monitoring of two different analytes is possible across the arms of the Y-splitter. The porous silicon (p-Si) rods with a porosity of 25% are used to create a variable refractive index sensing region, which induces a relative shift in the resonant wavelength of the traveling mode. The response at the output ports is monitored in terms of transmittance power versus wavelength plot. The numerical simulations confirm ∼195.83 nm/RIU sensitivity and ∼24.482 RIU−1 figure-of-merit in the presence of hazardous alcohols. © 2023 Elsevier LtdItem Plasmonic Biosensor for DNA Hybridization Using Integrated Graphene-Porous Silicon Waveguide(Institute of Electrical and Electronics Engineers Inc., 2023) Vankalkunti, S.; Singh, M.This work uses the full-vectorial finite element method to study a novel 3-D integrated graphene-porous silicon (p-Si) plasmonic waveguide-based nanostructure for deoxyribonucleic acid (DNA) hybridization. In this study, a p-Si waveguide is designed using the Maxwell Garnett model and is sandwiched between two low-indexed silicon dioxide (slot) layers. Next, a single graphene layer is deposited in both slot regions to enhance the sensor's absorption, tuneability, and sensitivity. The extraordinary optical transmission (EOT) through subwavelength nanoaperture reduces the ohmic losses and improves the optical transmission near the infrared region. Moreover, to optimize the sensor's design, a parametric analysis involving variations in the geometric dimensions of the sensor is performed using COMSOL multiphysics software. With 10% porosity of p-Si, the highest sensitivity value of 318.5 nm/RIU, 3.395/RIU figure of merit, 17.36 quality factor, and 0.01/nm detection accuracy with the presence of rectangular nanoaperture is achieved. Due to nanoscale size, the proposed label-free multilayer or hybrid plasmonic slot waveguide (HPSWG) biosensor offers the potential for future lab-on-a-chip (LOC) biological applications. © 2001-2012 IEEE.Item Hybrid Plasmonic Circular Aperture Waveguide for Blood Glucose Sensing(Institute of Electrical and Electronics Engineers Inc., 2024) Vankalkunti, S.; Singh, N.; Singh, M.A novel approach for blood glucose (or blood sugar) sensing utilizing a hybrid plasmonic circular aperture waveguide (HPCAW)-based nanostructure is proposed. The reported sensor combines the unique optical properties of plasmonic waveguides and circular aperture to achieve higher sensitivity and specificity in glucose detection. The HPCAW structure is designed to efficiently confine and propagate surface plasmon polaritons (SPPs) along the circular aperture, enabling enhanced light-matter interaction within the sensing region. Through rigorous numerical simulations and validation, we demonstrate the superior performance of the HPCAW sensor in terms of sensitivity (391.72 nm/RIU), figure of merit (FOM) (7.08 RIU-1), and detection accuracy (DA) (0.018 nm-1) compared to conventional glucose sensing techniques. Moreover, the proposed sensor offers inherent advantages, such as label-free detection, compact footprint, and compatibility with microfluidic systems. HPCAW provides a promising platform for the next-generation blood glucose monitoring applications with potential clinical translation. 1558-1748 © 2024 IEEE.Item Engineering Porous Silicon-Based Plasmonic Microdisk Resonator for Highly Sensitive Methanol Sensing(Institute of Electrical and Electronics Engineers Inc., 2024) Mehta, S.; Nakul Nayak, V.B.; Singh, M.This study introduces a novel application of a plasmonic microdisk resonator as a highly sensitive sensor for detecting methanol vapor. Leveraging the inherent advantages of plasmonic nanostructures, the microdisk resonator demonstrates a remarkable capability to detect minute concentrations of methanol. In this work, we modeled a novel 3-D porous-silicon (p-Si)-based hybrid plasmonic aperture-coupled microdisk resonator (HPACMR) with specific dimensions and porosity to optimize the sensitivity toward methanol vapor detection. The resonator's design incorporates a thin layer of copper on a dielectric microdisk, creating a plasmonic cavity that supports localized surface plasmon resonances. Finite element method-based simulations predict strong interactions between the resonator's plasmonic field and methanol molecules, leading to detectable shifts in the resonant frequency. By tuning the layout dimensions and p-Si properties, we achieved an altitudinous sensitivity of 569.52 nm/RIU and a Q-factor of nearly 370. The sensors' miniature footprint and potential for integration into portable devices make it an attractive candidate for field-deployable applications. © 2001-2012 IEEE.Item High-Q Plasmonic Resonator for Volatile Organic Compound Detection(Institute of Electrical and Electronics Engineers Inc., 2025) Mehta, S.; Shivaputra, S.; Ramesh, S.; Mandi, M.V.; Singh, M.A hybrid plasmonic waveguide (HPWG)-based resonator designs are studied for on-chip detection of volatile organic compounds (VOCs). The HPWG, which combines dielectric and metallic layers, significantly enhances the confinement of electromagnetic field, leading to increased interaction between the guided light and the surrounding analytes. The system achieves high spectral sensitivity and narrow linewidth by integrating multiple microring resonators in a cascaded configuration. This is critical for distinguishing small changes in the refractive index (RI) associated with different VOCs. Finite element method (FEM) simulations demonstrate the superior sensing performance of a proposed device, showing a spectral sensitivity of 469.5 nm/RIU and a quality factor (QF) of 518.75. The compact design and high sensitivity make this sensor an excellent candidate for on-chip VOC monitoring in industrial safety, as well as portable breath sensors to detect VOC biomarkers for early disease diagnosis. © IEEE. 1973-2012 IEEE.