Download or read book The Influence of Vanadium Doping on the Physical and Electrical Properties of Non Volatile Random Access Memory Using the BTV BLTV and BNTV Oxide Thin Films written by Kai-Huang Chen and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The Influence of Vanadium Doping on the Physical and Electrical Properties of Non-Volatile Random Access Memory Using the BTV, BLTV, and BNTV Oxide Thin Films.
Download or read book Advances in Ferroelectrics written by Aimé Peláiz-Barranco and published by BoD – Books on Demand. This book was released on 2012-11-19 with total page 546 pages. Available in PDF, EPUB and Kindle. Book excerpt: Ferroelectricity is one of the most studied phenomena in the scientific community due the importance of ferroelectric materials in a wide range of applications including high dielectric constant capacitors, pyroelectric devices, transducers for medical diagnostic, piezoelectric sonars, electrooptic light valves, electromechanical transducers and ferroelectric random access memories. Actually the ferroelectricity at nanoscale receives a great attention to the development of new technologies. The demand for ferroelectric systems with specific applications enforced the in-depth research in addition to the improvement of processing and characterization techniques. This book contains twenty two chapters and offers an up-to-date view of recent research into ferroelectricity. The chapters cover various formulations, their forms (bulk, thin films, ferroelectric liquid crystals), fabrication, properties, theoretical topics and ferroelectricity at nanoscale.
Download or read book Advances in Ferroelectrics written by Aimé Peláiz-Barranco and published by IntechOpen. This book was released on 2012-11-19 with total page 544 pages. Available in PDF, EPUB and Kindle. Book excerpt: Ferroelectricity is one of the most studied phenomena in the scientific community due the importance of ferroelectric materials in a wide range of applications including high dielectric constant capacitors, pyroelectric devices, transducers for medical diagnostic, piezoelectric sonars, electrooptic light valves, electromechanical transducers and ferroelectric random access memories. Actually the ferroelectricity at nanoscale receives a great attention to the development of new technologies. The demand for ferroelectric systems with specific applications enforced the in-depth research in addition to the improvement of processing and characterization techniques. This book contains twenty two chapters and offers an up-to-date view of recent research into ferroelectricity. The chapters cover various formulations, their forms (bulk, thin films, ferroelectric liquid crystals), fabrication, properties, theoretical topics and ferroelectricity at nanoscale.
Download or read book Resistive Random Access Memory written by Liang Zhao and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Recently, the rapid development of big data and internet-of-things has fueled a surge of demand for semiconductor memories. As the scaling of NAND flash is hitting its physical limits, several emerging non-volatile memory technologies are being studied intensively to enable higher memory density and better performance. Among them, resistive random access memory (RRAM) has attracted tremendous interests due to its ability to overcome the inherent limitations of flash memory, while also delivering cost-effectiveness, robust performance and small footprint. Despite its promising features, several challenges remain to be addressed for the future development and commercialization of RRAM technology. First of all, the physical mechanisms behind resistance-change phenomena have not been fully understood, making it difficult to optimize the device performance. Secondly, the reliability of RRAM should be improved in several aspects, such as the variability of switching parameters, the retention/endurance failures caused by the random nature of filament formation, as well as the requirement for a high-voltage forming process. Moreover, it is also highly desired to stack RRAM devices in a 3D architecture and/or develop multi-level storage capability to reduce the cost-per-bit and compete with NAND flash. This thesis presents an in-depth analysis of some state-of-the-art techniques to tackle these challenges from three aspects: the materials, the device structure, as well as the characterization methods. From the material's perspective, doping technology of RRAM is investigated as an approach to improve RRAM performance. Ab initio modeling and simulations are applied to study the effects of dopant types, dopant concentrations, oxide phases, and oxide stoichiometry on the electronic and thermodynamic properties of oxygen vacancies in HfO2. The physical insights derived from the calculations provide guidelines to achieve desirable RRAM characteristics through doping. In the aspect of electrical characterization, the pulse-train characterization techniques are developed for the multi-level control and in-depth physical understanding of conductive filament evolution. By adopting pulse-train operation for an RRAM device with 3-bit potential, the relative standard deviations of resistance levels are improved up to 80% compared to the single-pulse scheme. The observed exponential relation between the saturated resistance and the pulse amplitude provides supporting evidence for the gap-formation model during the RESET process of RRAM. From the device-structure point of view, the feasibility of ultra-thin HfO2 RRAM is investigated, which helps to achieve the forming-free property and low-power operation. The theoretical scaling limit of HfOx thickness is first estimated using density functional theory within the non-equilibrium Green's function formalism. The feasibility of 2-nm HfOx RRAM is predicted for large-area devices, and verified by fabricating both planar and 3D vertical RRAM devices. The 3D ultra-thin devices demonstrate promising characteristics including ON/OFF ratio (~100), switching speed (~20 ns), endurance (108 cycles) and data retention (> 10 years at room temperature). In contributing to these areas, this thesis aims at advancing both the fundamental understanding and practical implementation of RRAM technology, towards the vision of high-density mass-storage applications.
Download or read book Study of Doping Effects on the Physical Properties of Metal Oxide Thin Films for Resistive Memory Device Applications written by 李思賢 and published by . This book was released on 2019 with total page 123 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Electronic Thermoelectric and Optical Properties of Vanadium Oxides written by Chiranjivi Lamsal and published by . This book was released on 2015 with total page 270 pages. Available in PDF, EPUB and Kindle. Book excerpt: Correlated electrons in vanadium oxides are responsible for their extreme sensitivity to external stimuli such as pressure, temperature or doping. As a result, several vanadium oxides undergo insulator-to-metal phase transition (IMT) accompanied by structural change. Unlike vanadium pentoxide (V3O3), vanadium dioxide (VO3) and vanadium sesquioxide (V3O3) show I MT in their bulk phases. In this study, we have performed one electron Kohn-Sham electronic band-structure calculations of VO3, V3O3 and V2O5 in both metallic and insulating phases, implementing a full ab-initio simulation package based on Density Functional Theory (DFT), Plane Waves and Pseudopotentials (PPs). Electronic band structures are found to be influenced by crystal structure, crystal field splitting and strong hybridization between O2p and V3d bands. "Intermediate bands", with narrow band widths, lying just below the higher conduction bands, are observed in V2O5 which play a critical role in optical and thermoelectric processes. Similar calculations are performed for both metallic and insulating phases of bulk VO2 and V2O3. Unlike in the metallic phase, bands corresponding to "valence electrons" considered in the PPs are found to be fully occupied in the insulating phases. Transport parameters such as Seebeck coefficient, electrical conductivity and thermal (electronic) conductivity are studied as a function of temperature at a fixed value of chemical potential close to the Fermi energy using Kohn-Sham band structure approach coupled with Boltzmann transport equations. Because of the layered structure and stability, only V2O5 shows significant thermoelectric properties. All the transport parameters have correctly depicted the highly anisotropic electrical conduction in V2O5. Maxima and crossovers are also seen in the temperature dependent variation of Seebeck coefficient in V2O5, which can be consequences of "specific details" of the band structure and anisotropic electron-phonon interactions. For understanding the influence of phase transition on transport properties, we have also studied transport parameters of VO2 for both metallic and insulating phases. The Seebeck coefficient, at experimental critical temperature of 340K, is found to change by 18.9 μV/K during IMT, which lies within 10% of the observed discontinuity of 17.3 μV/K. Numerical methods have been used to analyze the optical properties of bulk and thin films of VO2, V2O3, and V2O5, deposited on Al2O3 substrates, from infrared to vacuum ultraviolet range (up to 12 eV). The energies corresponding to the peaks in the reflectivity-energy (R-E) spectra are explained in terms of the Penn gap and the degree of anisotropy is found to be in the order of V2O3
Download or read book Vanadium Dioxide for Memory Oscillators and Optical Beam Manipulation written by Junho Jeong and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Vanadium dioxide (VO2), which exhibits insulator-metal transition, has been utilized to demonstrate a non-volatile memory and a tunable metasurface device. To realize these devices, fabrication techniques were developed. Different dry etching recipes were created for making VO2 micro-wires depending on the material crystallinity. In addition, a post-fabrication technique using current injection was developed to create single-crystal VO2 micro-wires from initially poly-crystalline samples. The electrical properties of VO2 become more favorable after this recrystallization process. First, we present a VO2 memory device that demonstrated optically addressable nonvolatile memory at room temperature. The combination of electrical and optical stimuli was used to write memory, and the device state could be read out as voltage oscillations even after several days. This is the first time, to our knowledge, that non-volatile memory is observed in VO2 at room temperature. This observation suggests the presence of a metastable phase in the VO2. Although probing the physical nature of this phase was outside the scope of the thesis, the non-volatile memory effect was studied phenomenologically using VO2 micro-wire devices. Second, we show highly tunable optical transmission in a VO2 optical metasurface. The device consisted of gold (Au) gratings on a VO2 thin film. The gratings simultaneously served to enhance the optical transmission and as resistive heaters. As current was applied through the Au gratings, the localized area of VO2 became metallic due to Joule heating. By switching between extraordinary optical transmission when the VO2 was an insulator to a high absorptive state when the VO2 was metallic, the transmission was tunable by 33 dB/mm. Furthermore, another metasurface device is proposed with simulations displaying reconfigurable beam steering capabilities while using only digital switching of the VO2 elements. With the development of fabrication processes along with the demonstrations of nonvolatile memory and beam manipulation with VO2, this thesis expands the opportunities for VO2 to be used in new types of computing and flat optics devices.
Download or read book Forming free Nitrogen doped Aluminum Oxide Resistive Random Access Memory written by Wanki Kim and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The persistent request for smaller, faster, cheaper, more capable electronic devices continues to drive the development of technology and to drive the exploration of unique materials to overcome the limits of conventional Si-based technology. Since many modern electronic devices become mobile and multifunctional, they need a new high-density nonvolatile memory overcoming density limitations of currently used flash memory. Bi-stable switching is reported to be observed in a variety of next-generation non-volatile memory technologies such as a resistive random access memory (RRAM), a phase-change random access memory (PRAM), a magnetoresistive random access memory (MRAM) and a ferroelectric random access memory (FeRAM). Among these nonvolatile memories, resistive random access memory (RRAM) is a promising candidate for next-generation nonvolatile memory with higher density than that of flash memory since it is based on a low-temperature grown oxide thin film with bi-stable resistance states and is compatible with three-dimensional stack structure. Among various oxide films exhibiting the resistive switching phenomenon, aluminum oxide (AlOX) is one of the most promising materials because of its simple constituents, clear switching characteristics, and moderate on/off ratio. In addition, since AlOX has a simple binary system, it has an advantage for the industrial fabrication. However, there are some challenges that need to be addressed for the AlOX based RRAM. One of the challenges is that AlOX RRAM cells have been reported to require a high voltage forming process. So, making good quality aluminum oxide film with a moderate amount of defects is a main issue for realizing AlOX RRAM devices. In this dissertation, we present a simple nitrogen-doped AlOX (N-AlOX) RRAM cell that has a moderate amount of defects. The main contribution of this dissertation is a new type of RRAM (N-AlOX RRAM) that does not require a forming process and shows small programming currents. Some switching mechanisms have been proposed to explain the resistance switching phenomenon of AlOX RRAM. However, the underlying mechanism of resistance switching behavior of N-AlOX RRAM has not been understood. So, we perform some material analyses of N-AlOX RRAM in detail to understand the switching mechanism. Next, we discuss various electrical characteristics of N-AlOX RRAM. Based on the electrical characteristics, we present a Frenkel-Poole model for the current conduction mechanism of N-AlOX RRAM. The last topic of this dissertation is titanium oxide (TiOX) based RRAM. We focus on evaluating many electrodes and understanding the impact on the switching characteristics of TiOX RRAM. As a result, we find iridium oxide (IrO2) as a viable electrode for TiOX RRAM. In addition, we successfully improve the uniformity of switching parameters by inserting two hafnium (Hf) interfacial layers. Finally, we conclude this dissertation with a summary of the main points and some suggestions for future work on this topic.
