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Book Development of Indium Gallium Zinc Oxide Thin Film Transistors on a Softening Shape Memory Polymer for Implantable Neural Interfaces Devices

Download or read book Development of Indium Gallium Zinc Oxide Thin Film Transistors on a Softening Shape Memory Polymer for Implantable Neural Interfaces Devices written by Ovidio Rodriguez Lopez and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The continuous improvement in electronic active devices has led to several innovations in semiconductor materials, novel deposition methods, and improved microfabrication techniques. In the same way, the implementation of thin-film technology has revolutionized the semiconductor industry. For instance, the field of flexible electronics has utilized novel thin-film electronics components for the fabrication flexible displays, radio frequency identification (RF-ID) tags, and solar cells. Moreover, flexible electronics have sparked a great interest in the field of bioelectronics, for the fabrication of high-spatial-resolution implantable devices for neural interfaces. This incorporation of thin-film technology can potentially enable stimulation and recording the nervous system activity by utilizing novel, minimally invasive, conformal devices. To achieve this, flexible electronics circuits must possess high performance, reliability, and stability, as well as be resilient to mechanical stress and human body conditions, are some of the requirements that flexible electronics must meet for the realization of these devices. Furthermore, the choice of substrates is also critical since it directly affects final properties of the active devices. Substrates, which are mechanically and biologically compliant, are preferred. For this reason, novel, softening materials like thiol-ene polymers are considered in this research. This work centers on the development of Indium-Gallium-Zinc-Oxide (IGZO) thin-film transistors (TFT) using the thiol-ene softening polymer as substrate. Functional IGZO-TFTs were fabricated on top of 50 μm of a thiol-ene/acrylate shape memory polymer (SMP) and electrically characterized. Hafnium oxide (HfO2) deposited at 100°C by atomic layer deposition was used as gate dielectric, and gold (Au) as contacts. The devices were exposed to oxygen, vacuum and forming gas (FG) environments at 250°C to analyze the effects of these atmospheres on the IGZO-TFTs. Improvement in the electrical performance was noticed after the exposure to FG with a significant change in mobility from 0.01 to 30 cm2 V-1s-1, and a reduction in the threshold voltage shift (∆Vth), which it is translated into an increase on stability. Vacuum and oxygen effects were, also analyzed and compared. Furthermore, a time-dependent dielectric breakdown (TDDB) analysis was performed to define the lifetime of the transistors, where a prediction of 10 years at an operational range below 5 V was obtained. Additionally, the TFTs were encapsulated with 5 μm of SMP and exposed to simulated in vivo conditions. Up to 104 bending cycles were performed to the IGZO-TFTs with a bending radius of 5 mm and then, soaked into PBS solution at 37°C for one week to determine the resilience and reliability of the devices. The encapsulated IGZO-TFTs survived to the PBS environment and demonstrated resilience to mechanical deformation with small changes in the electronic properties. The results provided in this research contribute to the development of complex circuitry based on thin-film devices using mechanically adaptive polymers as a flexible substrate and enable the production of multichannel implantable bioelectronics devices.

Book Amorphous Indium Gallium Zinc Oxide Thin Film Transistors Non volatile Memory and Circuits for Transparent Electronics

Download or read book Amorphous Indium Gallium Zinc Oxide Thin Film Transistors Non volatile Memory and Circuits for Transparent Electronics written by and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The ability to make electronic devices, that are transparent to visible and near infrared wavelength, is a relatively new field of research in the development of the next generation of optoelectronic devices. A new class of inorganic thin-film transistor (TFT) channel material based on amorphous oxide semiconductors, that show high carrier mobility and high visual transparency, is being researched actively. The purpose of this dissertation is to develop amorphous oxide semiconductors by pulsed laser deposition, show their suitability for TFT applications and demonstrate other classes of devices such as non-volatile memory elements and integrated circuits such as ring oscillators and active matrix pixel elements. Indium gallium zinc oxide (IGZO) is discussed extensively in this dissertation. The influence of several deposition parameters is explored and oxygen partial pressure during deposition is found to have a profound effect on the electrical and optical characteristics of the IGZO films. By optimizing the deposition conditions, IGZO TFTs exhibit excellent electrical properties, even without any intentional annealing. This attribute along with the amorphous nature of the material also makes IGZO TFTs compatible with flexible substrates opening up various applications. IGZO TFTs with saturation field effect mobility of 12 â€" 16 cm2 V-1 s-1 and subthreshold voltage swing of 200 mV decade-1 have been fabricated. By varying the oxygen partial pressure during deposition the conductivity of the channel was controlled to give a low off-state current ~ 10 pA and a drain current on/off ratio of 1 x108. Additionally, the effects of the oxygen partial pressure and the thickness of the semiconductor layer, the choice of the gate dielectric material and the device channel length on the electrical characteristics of the TFTs are explored. To evaluate IGZO TFT electrical stability, constant voltage bias stress measurements were carried out. The observed logarithmic depende.

Book Amorphous Indium Gallium Zinc Oxide Based Thin Film Transistors and Circuits

Download or read book Amorphous Indium Gallium Zinc Oxide Based Thin Film Transistors and Circuits written by Haojun Luo and published by . This book was released on 2013 with total page 155 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Stability of Softening Neural Interfaces With A SIC Thin Film Interlayer

Download or read book Stability of Softening Neural Interfaces With A SIC Thin Film Interlayer written by Adriana C. Duran Martinez and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Neural interfaces are implantable devices that enable communication between a computer and nervous tissue to read, write and block neural activity within targeted nerves. To improve the chronic use of neural interfaces, the materials used to develop them have been evolving with time, leading to softer and thinner layers of the involved materials to minimize the foreign body response from the body caused by the implanted device. Recently, researchers have studied many biocompatible polymers that promise to extend the lifetime of neural interfaces. An emerging materials class of interest, softening polymers (SPs), has performance advantages (while stiff and rigid) similar to Parylene-C and Polyimide during fabrication, handling, and insertion, but after softening (e.g. once implanted into the body), this class of polymers demonstrates enhanced conformability. This dissertation work (1) describes the flexibility and performance as an insulator of thiol-ene based softening polymers, (2) details a fabrication process of SP-based devices integrating amorphous silicon carbide (a-SiC) as an encapsulation layer and (3) elucidates structure-property-processing relationships of a-SiC SP neural interfaces via long-term electrical stability after accelerated aging and cyclic bending for future use in chronic animal studies.

Book Composition Engineering for Solution Processed Gallium Rich Indium Gallium Zinc Oxide Thin Film Transistors

Download or read book Composition Engineering for Solution Processed Gallium Rich Indium Gallium Zinc Oxide Thin Film Transistors written by Isaac Caleb Wang and published by . This book was released on 2018 with total page 60 pages. Available in PDF, EPUB and Kindle. Book excerpt: Metal oxides have risen to prominence in recent years as a promising active layer for thin film transistors (TFTs). One of the main reasons for this has been its value in display technology. Conventionally, displays have relied on amorphous hydrogenated silicon (a-Si:H) TFTs but the demand for large area displays with high resolution, fast response time, low power consumption and compatibility with integrated driving circuits have prompted research into other semiconducting materials. As a result, metal oxides have become major prospects to replace a-Si:H with their high-performance electrical characteristics and simplicity of processing, making them valuable switching elements in display technology. Particularly, quaternary metal oxides such as the amorphous Indium-Gallium-Zinc-Oxide (IGZO) have demonstrated extremely high performances as TFTs, prompting extensive research in the field. The conventional method of producing metal oxide thin films has been through vacuum deposition methods such as sputtering. However, for large area applications these vacuum deposition methods face inherent limitations which prevent easy application and device fabrication. Facing these restrictions, solution-processing has become a popularly researched alternative in producing metal oxide thin films due to their simple processing requirements, low cost, and ability to be applied over large areas. In solution-processed IGZO, there have been a couple approaches to improve device performance and stability as well as simplify processing. In this work, we produce a gallium-rich 2:2:1 IGZO TFT using solution processes and study its electrical characteristics and stability. In this paper, we demonstrate a working solution-processed gallium-rich 2:2:1 IGZO TFT and compare it to a solution-processed indium-rich device to quantify its stability and performance. Through this work, we show that solution-processing is a viable fabrication method for gallium-rich IGZO, which can be a high-stability alternative to other compositions of IGZO devices.

Book Indium Gallium Zinc Oxide Thin Film Transistors for Active Matrix Flat Panel Displays

Download or read book Indium Gallium Zinc Oxide Thin Film Transistors for Active Matrix Flat Panel Displays written by Forough Mahmoudabadi and published by . This book was released on 2017 with total page 178 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this work, a robust process for fabrication of bottom-gate and top-gate a-IGZO TFTs is presented. An analytical drain current model for a-IGZO TFTs is proposed and its validation is demonstrated through experimental results. The instability mechanisms in a-IGZO TFTs under high current stress is investigated through low-frequency noise measurements. For the first time, the effect of engineered glass surface on the performance and reliability of bottom-gate a-IGZO TFTs is reported.

Book Hydrolytically Stable Thiol ene Polymer Substrates for Neural Interface Devices

Download or read book Hydrolytically Stable Thiol ene Polymer Substrates for Neural Interface Devices written by Seyedmahmoud Hosseini and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Bioelectronics devices can be described as the combination of materials and electronics to interface with biological systems, and are typically used to detect and modulate biological signals in order to control bodily functions with promise to treat and perhaps cure diseases. Neural interface systems represent a class of bioelectronic devices that facilitate connection between the outside world and the nervous system through conducting electrodes which transduce electric signals to and from the bioelectronic device (and thus to and from the body) to treat or help people with neurological disorders. One type of device used in neural interface systems today is composed of a substrate and one or multiple electrodes whose purpose is to add, remove or block information from various parts of the central or peripheral nervous system. The performance of the so-called electrode-tissue interface (or how the device connects to the nervous system) varies depending upon the nature of the electrode/substrate combination. A driving disadvantage of many typical electrodes fabricated on hard materials is the resulting inflammatory reaction that may lead to electrode failure or adverse signal recording, stimulating or blocking. Using polymers as a substrate, with a Young's modulus in the MPa range after insertion at an initially higher modulus, upon which to fabricate electrodes, has been proposed as a design mechanism to help address many of the mechanical mismatch issues associated with stiff materials. In particular, one class of materials has been explored extensively in this space over the past half-decade: thiol-based shape memory polymers. Thiol-ene/acrylate copolymers were introduced in 2012 to tackle several of the physical mismatch problems resulting in a half decade of efforts to understand effects of these materials on the underlying physiology acutely and sub-chronically in small animal models. Using shape memory polymers has led over the past half-decade to the optimization of devices (cortical probes, cochlear implants, nerve cuffs, spinal cord simulators and others) which are stiff enough to be effectively handled by surgeons, implanted, and subsequently demonstrated reduced stiffness after insertion into neural tissue and a different physiological response than materials which are always stiff. Currently, most of the commercially available monomers used in the design and fabrication of shape memory based neural interfaces contain chemical structures with ester functional groups, which increase the polymers’ susceptibility to hydrolytic degradation under moist conditions. Hydrolysis of polymer substrates can lead to many adverse effects for neural interfaces, producing specific by-products at different points after implantation. Therefore, the degraded polymer often is the culprit for worsening device performance: as a direct result of the ester-mediated degradation of these polymers, leakage channels develop through the device and negatively affect the subchronic and chronic electrical performance of devices. In this research, a series of novel thiol-ene formulations have been designed, formulated, polymerized and tested in actual devices. These new materials demonstrate a glass transition temperature and modulus similar to leading shape memory polymer neural interfaces in the published literature, but these novel formulations do not contain ester groups anywhere in the polymer network, allowing exploration of the hypothesis that this approach minimizes hydrolytic instability under the conditions to which neural interfaces are subjected. The synthesis of several new monomers was optimized and a novel polymer composition was designed and realized through photopolymerization from these new building blocks to have similar in vivo softening capabilities as previously reported polymers. Dynamic mechanical analysis (DMA) of the hydrolytically stable polymer reveals that the polymer has a glass transition temperature above body temperature when dry and below body temperature after being soaked in physiologically representative media such as phosphate buffered saline (PBS). Thus, the novel polymers in and around this resulting design space are able to soften under physiological conditions to a modulus which is much closer to the tissue than the as-inserted devices. To verify the improved stability of the new material against hydrolysis, accelerated aging tests were performed. Weight loss and mechanical properties were determined and compared to ester-containing polymer compositions. Resulting polymers are proposed as a candidate for translation into next-generation bioelectronic devices as substrates that help overcome a major limitation with previous shape memory polymer based neural interfaces.