Browsing by Author "Paul, Febin"
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Item Metadata only Electrical Bistability by Creating an Internal Electrical Field and Its Application in Emerging Two-terminal Electronic Memory Devices(Royal Society of Chemistry, 2023-10-09) Paul, Febin; Paul, ShashiThis chapter focusses on the electrical bistability observed in nanocomposite memory devices that have been studied over two decades. Bistability, in the context of memory devices, has been discussed and visual tools have been employed for its examination as a general mathematical function. The bistability observed in memory devices, in terms of electrical hysteresis, has been focussed and typical curves observed in several studies over the last fifty years have been consolidated and systematically examined. The development of the field has led to much confusion in terms of understanding of the device switching mechanism, which has been investigated in detail. The discrepancies in the proposed device behaviour and the observations have over time led to the rise of many opinions/models to explain the physics of the device conduction switching. In this chapter, the charge-trap models have been examined and solutions to some open questions have been proposed in terms of analysing at the system from the perspective of field generation, instead of the material interaction.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 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 A Study on Charge Storage mechanism using gold nanoparticles to understand the Electrical Bistability in two-terminal Organic Memory Devices(De Montfort University, 2021-08) Paul, FebinOrganic electronics has taken leaps and bounds in the past few years. From LED screens to wearable technology, it has enabled the emergence of technologies that would have been unimaginable a few decades earlier. The organic memory devices have emerged to be a perfect alternative in the non-volatile memory sector due to its compatibility in the printed technology, low power application and device performance too. Despite these advantages progress in the field has been slow due to the lack of clarity around the device operation. The field has seen several works that have focussed on the same device or even similar structures, only to arrive in vastly different conclusions. A persistent lack of agreement in this regard, despite some excellent work having been done in the field, point to a gap in knowledge in the physics of the device operation. The focus of this work has been to address this uncertainty of device operation in two terminal memory devices. This work was focussed on two terminal gold nanoparticle devices that have been fabricated by drop casting on gap cells. The problem definition was based on a literature survey of several work that had been conducted in this area for around two decades. Several mechanisms that were proposed as a result of several investigations have been identified and arranged in a manner to obtain a holistic view of the subject. Several studies have been investigated closely to recognise gaps in the experiment design and isolate factors that might have contributed to the final result. As a result, gold nanoparticle devices were carefully designed to avoid any parasitic contribution from these external factors. These devices were investigated under varying electric field to study the behavioural response. The result has shown that the device operation relies heavily on the charge storage to bring about a change in the resistance. The device properties were tested by Impedance Spectroscopy measurement, in order to verify if the change in device conduction was due to resistive switching (like filamentary conduction, valence change switching etc.) or due to charge storage. The results demonstrated that the charge storage in the nanoparticles were responsible for the resistance change of the device. This was further confirmed by conducting the impedance measurement on the device at zero-DC-bias after applying a non-zero bias to measure the remnant charge that are trapped in the devices. These tests revealed the presence of trapped charges in the device. However, a coexisting relationship of resistance and capacitance was observed too, where the ligands and the gold nanoparticle dispersion played an important part in the baseline resistance of the system. This was due to the nanoparticle dispersion and the electrode contact- varying which demonstrated a change in the baseline resistance, while the capacitance remained comparable. The retention and the ON/OFF ratio were also investigated for the devices, demonstrating the need for further isolation of the nanoparticles in the devices.Item Open Access To Be or Not to Be – Review of Electrical Bistability Mechanisms in Polymer Memory Devices(Wiley, 2022-02-08) Paul, Febin; Paul, ShashiOrganic memory devices are a rapidly evolving field with much improvement in device performance, fabrication, and application. But the reports have been disparate in terms of the material behavior and the switching mechanisms in the devices. And, despite the advantages, the lack of agreement in regards to the switching behavior of the memory devices is the biggest challenge that the field must overcome to mature as a commercial competitor. This lack of consensus has been the motivation of this work wherein various works are compiled together to understand influencing factors in the memory devices. Different works are compared together to discover some clues about the nature of the switching occurring in the devices, along with some missing links that would require further investigation. The charge storage mechanism is critically analyzed alongside the various resistive switching mechanisms such as filamentary conduction, redox-based switching, metal oxide switching, and other proposed mechanisms. The factors that affect the switching process are also analyzed including the effect of nanoparticles, the effect of the choice of polymer, or even the effect of electrodes on the switching behavior and the performance parameters of the memory device.