Browsing by Author "Nama Manjunatha, Krishna"
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Item Open Access Advances in Gallium Oxide: Properties, Applications, and Future Prospects(Wiley, 2025-03-20) Ganguly, Swapnodoot; Nama Manjunatha, Krishna; Paul, ShashiThe traditional domination of silicon (Si) in device fabrication is increasingly infiltrated by state‐of‐the‐art wide bandgap semiconductors such as gallium nitride (GaN) and silicon carbide (SiC). However, the performance of these wide bandgap semiconductors has not yet exceeded the optical material limitation, which leaves ample room for further development. Gallium oxide (Ga2O3) has surfaced as the preferred material for next‐generation device fabrication, as it has a wider bandgap (≈4.5–5.7 eV), an estimated twofold greater breakdown field strength of 8 MV cm−1, and a higher Baliga's figure of merit(BFOM) (>3000) than SiC and GaN, therefore pushing the limit. In this review, the properties of gallium oxide, several methods for epitaxial growth, its energy band, and its broad spectrum of applications are discussed. Metals for achieving different types of contact and the influence of interfacial reactions are additionally assessed. Furthermore, defects and challenges such as p‐type doping, integration with heterostructures, the formation of superlattices, and thermal management associated with the use of this material are also reviewed.Item Metadata only Flexible Silicon Photovoltaic Solar Cells(CRC Press, 2022-03-24) Shende, Pratik Deorao; Nama Manjunatha, Krishna; Salaoru, Iulia; Paul, ShashiThis chapter discusses research and development of emerging silicon-based flexible solar cells. More emphasis is shown on the technology, underlying principles, device architecture, fabrication process, strengths, and challenges of the flexible solar cells fabricated using silicon. This chapter considers all the counterparts of silicon, from bulk to nanostructures that are used to fabricate photovoltaic devices. Change in the structure (low-dimensional and bulk materials), morphology (surface texturing and pyramid structures), and crystallinity (amorphous, poly-crystalline, and crystalline) of silicon as an absorber layer has shown enhanced efficiencies and reliabilities in flexible silicon solar cells. Flexibility and stretchability in solar cells are achieved mainly due to the adoption of novel structures, fabrication techniques, and, most importantly, the adoption of various flexible substrates (metal foils, polymers, and thin glass). The advantages and disadvantages of solar cells are discussed in terms of achieved efficiency, fabrication method, flexibility, and chosen substrate.Item Metadata only Influence of Surface Chemical and Topographical Properties on Morphology, Wettability and Surface Coverage of Inkjet-Printed Graphene-Based Materials(MDPI, 2024-05-22) Salaoru, Iulia; Morris, Dave; Ware, Ecaterina; Nama Manjunatha, KrishnaThe inkjet printing of water-based graphene and graphene oxide inks on five substrates, two rigid (silicon and glass) and three flexible (cellulose, indium tin oxide-coated polyethylene terephthalate (ITO-PET) and ceramic coated paper (PEL paper)), is reported in this work. The physical properties of the inks, the chemical/topographical properties of selected substrates, and the inkjet printing (IJP) of the graphene-based materials, including the optimisation of the printing parameters together with the morphological characterisation of the printed layers, are investigated and described in this article. Furthermore, the impact of both the chemical and topographical properties of the substrates and the physical properties of graphene-based inks on the morphology, wettability and surface coverage of the inkjet-printed graphene patterns is studied and discussed in detail.Item Open Access Non‐Zero and Open‐Loop Current–Voltage Characteristics in Electronic Memory Devices(Wiley, 2023-08-09) Paul, Febin; Nama Manjunatha, Krishna; Paul, ShashiThis work focuses on the non-zero-crossing and open-loop current–voltage (I–V) characteristics of electronic memory devices that are studied and focused on primarily for non-volatile memory storage applications. Gold nanoparticles-based devices are fabricated to understand possible non-crossing zero and open-loop current–voltage behavior, where a non-zero current and open loop I–V characteristics are observed at zero voltage. While other studies have attributed this behavior as a “battery effect”, this study presents an alternate perspective for non-redox-based charge storage memory devices. The electrical measurements clearly demonstrate that the non-zero current and open-loop characteristics are due to the charge trapping of the gold nanoparticles. The charge accumulation within the nanoparticle is observed to create a non-zero potential within the device and thereby encouraging such behavior, even though the applied external voltage is zero. The longstanding mystery in deciphering if electrical measurements or the charge storage device contributes toward non-zero property is unfurled in this article. A possible charge storage model is proposed and further verified using liquid crystals-based two terminal devices. The presence of internal potential leads to an offset within the devices, a non-zero current and open-loop I–V even when the external applied voltage is zero.Item Open Access Rational design on materials for developing next generation Lithium-ion secondary battery(Elsevier, 2020-10-29) Mambazhasseri Divakaran, Arun; Minakshi, Manickam; Arabzadeh Bahri, Parisa; Paul, Shashi; Kumari, Pooja; Mambazhasseri Divakaran, Anoop; Nama Manjunatha, KrishnaLithium-ion batteries (LIBs) gained global attention as the most promising energy storing technology for the mobile and stationary applications due to its high energy density, low self-discharge property, long life span, high open-circuit voltage and nearly zero memory effects. However, to meet the growing energy demand, this energy storage technology must be further explored and developed for high power applications. The conventional lithium-ion batteries mainly based on Li-ion intercalation mechanism cannot offer high-charge capacities. To transcend this situation, alloy-type anode and conversion-type anode materials are gaining popularity. This review article focuses on the historical and recent advancements in cathode and anode materials including the future scope of the lithium nickel manganese cobalt oxide (NMC) cathode. Equal emphasis is dedicated in this review to discuss about lithium based and beyond lithium-based anode materials. This review additionally focuses on the role of technological advancements in nanomaterials as a performance improvement technique for new novel anode and cathode materials. Also, this review offers rational cell and material design, perspectives and future challenges to promote the application of these materials in practical lithium-ion batteries.Item Open Access Single step ohmic contact for heavily doped n-type silicon(Elsevier, 2019-11-14) Paul, Febin; Nama Manjunatha, Krishna; Paul, Shashi; Govindarajan, S.This work focusses on the metal-semiconductor contact on n-type c-Si wafers and explore the possibility of using magnesium (Mg) to form electron–selective contacts instead of using the conventional Au-Sb films which requires high temperature annealing between 350 and 500 °C. Aluminium (Al) capping layer was added over the magnesium contacts to prevent oxidation of magnesium. Various electrical measurements were performed over thermally evaporated Mg/Al contacts to investigate the conduction properties on both p-type and n-type silicon, where a Schottky behaviour was observed for the p doped silicon, but an ohmic behaviour (V ∝ I) for the n-type doped c-Si samples. The results were further optimised after investigating various thicknesses of the Mg interlayer, with 10 nm of Mg interlayer found to have the least resistance. The resistivity of the optimised structure (n-Si/Mg-10 nm/Al) was calculated, and measurements according to the Transmission Line Method (TLM) showed a contact resistivity of 462mΩ cm2 ± 20mΩ cm2. Further investigations were also conducted on the effect of high temperature annealing of the magnesium contact, which showed an increase in resistance with increase in annealing temperature, with the lowest resistance obtained without annealing. Additional investigations focussed on the morphological analysis of the deposited magnesium and its impact on the electrical characteristics.Item Open Access Storing Electronic information on Semi-Metal Nanoparticles(Royal Society of Chemistry, 2022-05-11) Paul, Febin; Nama Manjunatha, Krishna; Paul, ShashiThis paper presents the use of selenium nanoparticles for the application of information storage in two terminal electronic memory devices. Selenium is a semi-metal with interesting electronic and optical properties that have seldom been studied in terms of electronic memory. In this study selenium nanoparticles have been demonstrated as an embedded charge storage layer between silicon oxide tunnel layer and silicon nitride blocking layer. The electrical characterisation demonstrates clear evidence that charge storage is taking place, and that it is indispensable without the presence of nanoparticles. AFM images show that selenium nanoparticles are almost uniformly distributed on Silicon substrate having a thin silicon dioxide tunnelling layer, and the electrical retention measurement shows potential for long term data storageItem Open Access Wire-bar coating of doped Nickle oxide thin films from metal organic compounds(Elsevier, 2019-05-23) Nama Manjunatha, Krishna; Paul, ShashiThis study discusses the significance of aliovalent cations, especially monovalent compared to trivalent, which provide controlled doping and increase in the conductivity of nickel oxide (NiO) thin films. This report is a first proof of concept involving simple and economical K-bar, wire-wound deposition of doped and undoped NiO films. As deposited films have similar optical and electrical properties compared to the most commonly used deposition techniques for the deposition of NiO thin films. Doping of NiO from three different metal salts that have a different valencies (Cu1+, Zn2+, and Ga3+) as dopants for NiO thin films is investigated. This will help us understand the effect of monovalent, bivalent and trivalent ions towards the doping in NiO. Change in the structural, optical and electrical properties of NiO are investigated and compared amongst different metals (dopants) with different valencies. Furthermore, these properties are investigated in-depth by varying the concentration of the dopants (between 0 at.% and 8 at.%) within the NiO film.