Recently an effective usage of the chip area plays an essential role for System-on-Chip (SOC) designs. Nowadays on-chip memories take up more than 50%of the total die-area and are responsible for more than 40% of the total energy consumption. Cache memory alone occupies 30% of the on-chip area in the latest microprocessors. This thesis project “System Level Exploration of RRAM for SRAM Replacement” describes a Resistive Random Access Memory (RRAM) based memory organizationfor the Coarse Grained Reconfigurable Array (CGRA) processors. Thebenefit of the RRAM based memory organization, compared to the conventional Static-Random Access Memory (SRAM) based memory organization, is higher interms of energy and area requirement. Due to the ever-growing problems faced by conventional memories with Dynamic Voltage Scaling (DVS), emerging memory technologies gained more importance. RRAM is typically seen as a possible candidate to replace Non-volatilememory (NVM) as Flash approaches its scaling limits. The replacement of SRAMin the lowest layers of the memory hierarchies in embedded systems with RRAMis very attractive research topic; RRAM technology offers reduced energy and arearequirements, but it has limitations with regards to endurance and write latency. By reason of the technological limitations and restrictions to solve RRAM write related issues, it becomes beneficial to explore memory access schemes that tolerate the longer write times. Therefore, since RRAM write time cannot be reduced realistically speaking we have to derive instruction memory and data memory access schemes that tolerate the longer write times. We present an instruction memory access scheme to compromise with these problems. In addition to modified instruction memory architecture, we investigate the effect of the longer write times to the data memory. Experimental results provided show that the proposed architectural modifications can reduce read energy consumption by a significant frame without any performance penalty.

Understanding animal locomotion requires modeling the interaction of the organism with its environment. Locomotion within granular media like sand, soil, and debris that display both solid and fluid-like behavior in response to stress is less studied than locomotion within fluids or on solid ground. To begin to reveal the secrets of movement in sand, I developed models to explain the subsurface locomotion of the sand-swimming sandfish lizard. I developed a resistive force theory (RFT) with empirical force laws to explain the swimming speed observed in animal experiments. By varying the amplitude of the undulation in the RFT, I found that the range of amplitude used by the animal predicted the optimal swimming speed. I developed a numerical model of the sandfish coupled to a discrete element method simulation of the granular medium to test assumptions in the RFT and to study more detailed mechanics of sand-swimming. Inspired by the shovel-shaped head of the sandfish lizard, I used the simulation to study lift forces in granular media: I found that when a submerged intruder moved at a constant speed within a granular medium it experienced a lift force whose sign and magnitude depended on the intruder shape. The principles learned from the models guided the development of a biologically inspired robot that swam within granular media with similar performance to the lizard.

An active optical shutter for infrared light (3-5 μm) has been designed, exploiting the phase transition in thermochromic vanadium dioxide (VO2). A spin coating processing route for VO2 films has been adapted to manufacture reproducible depositions onto sapphire (Al2O3) substrates. The VO2 films have been characterized by X-ray powder diffraction (XRPD) and infrared spectroscopy (FTIR), showing 55 % transmittance in the open mode and 0.1 % in the closed mode. The VO2 film temperature determines the operating mode of the shutter, and a resistive circuit of gold was deposited on top of the film for heating purposes. Switching times from the open to the closed mode down to 15 ms have been measured. This work is a part of a comprehensive project at the Swedish Defence Research Agency (FOI), aiming to improve active components for protection against lasers. The shutter within this work is at this stage an early prototype, and needs further development and complementary systems such as a control unit to be implemented in an optical system.

The objective of this thesis is aimed at the design of low noise amplifier (LNA) for an ultra-wideband (UWB) receiver system using standard 0.18um CMOS process. A two amplified stage topology is proposed in the low noise amplifier. The first stage introduces inductively source degeneration, it can achieve wideband input impedance matching. The second stage introduces traditional CS configuration, it can improve the forward gain (S21). The second stage also used L-C section for output match. In order to improve the gain at high frequency, we introduces the series peaking between the first stage and second stage. We use the resistive-feedback between second stage and output, it can achieve wideband output impedance matching. The total power dissipation of the low noise amplifier is about 16.5mW at power supply 1.5 volt and the chip size is 920*940mm2. The simulated result shows that S11 is under -9dB, S22 is under -10dB, the forward gain S21 is 11.63dB~12.56dB at 3.1-10.6GHz, the reverse isolation S12 is under -32dB, and the noise figure is3.3dB~3.96dB.

In first part, the supercritical CO2 (SCCO2) fluid technology is employed to improve the device properties of ZnO TFT. The SCCO2 fluid exhibits liquid-like property, which has excellent transport ability. Furthermore, the SCCO2 fluid has gas-like and high-pressure properties to diffuse into the nanoscale structures without damage. Hence, the SCCO2 fluid can carry the H2O molecule effectively into the ZnO films at low temperature and passivate traps by H2O molecule at low temperature. The experimental results show that the on current, sub-threshold slope, and threshold voltage of the device were improved significantly. Next, the electrical degradation behaviors and mechanisms under drain bias stress of a-IGZO TFTs were investigated. A current crowding effect and an obvious capacitance-voltage stretch-out were observed after stress. During the drain-bias stress, the oxygen would be absorbed on the back channel near the drain region of IGZO film. Therefore, the carrier transport is impeded by the additional energy barrier near drain region induced by the adsorbed oxygen, which forms a depletion layer to generate the parasitism resistance. We also investigated the RRAM device based on IGZO film, and proposed the related physical mechanism models. The IGZO RRAM will be very promising for integration with IGZO TFTs for advanced system-on-panel display applications to be a transparent embedded system. In this part, the transparent RRAM device with ITO/IGZO/ITO structure was fabricated. The proposed device presents an excellent bipolar resistive switching characteristic and good reliability. The bipolar switching mechanism of our device is dominated by the formation and rupture of the oxygen vacancies in a conduction path. The influence of electrode material on resistance switching characteristic is investigated through Pt/IGZO/TiN and Ti/IGZO/TiN structure. As the bias applied on the Ti or TiN, the Ti or TiN electrode can play the role of oxygen reservoir to absorb/discharge oxygen ions. Therefore, the device presents a bipolar resistive switching characteristic. However, as the bias applied on the Pt electrode, the device presents a unipolar resistive switching characteristic. Because the Pt electrode can¡¦t store the oxygen ion, the device should use the joule heating mode to rupture the conduction path and present the unipolar resistive switching characteristic. Finally, the resistive switching properties of IGZO film deposited at different oxygen content were investigated, since the resistance switching behaviors are related to the formation and rupture of filaments composed of oxygen vacancies in the IGZO matrix. Experiment results show that the HRS current decreases when the oxygen partial pressure gradually increases. Based on the XPS analysis, these phenomena are related to the non-lattice oxygen concentration. With increasing oxygen ratio, the filaments will rupture completely through the abundant non-lattice oxygen inducing oxidation, which leads to HRS current decrease and an increase in the memory window.

This thesis reports the development of high performance readout electronics for resistive microbolometer detector arrays that are used for uncooled infrared imaging. Three different readout chips are designed and fabricated by using a standard 0.6 &micro / m CMOS process. Fabricated chips include a conventional capacitive transimpedance amplifier (CTIA) type readout circuit, a novel readout circuit with dynamic resistance nonuniformity compensation capability, and a new improved version of the CTIA circuit. The fabricated CTIA type readout circuit uses two digital-to-analog converters (DACs) with multiple analog buses which compensate the resistance nonuniformity by adjusting the bias currents of detector and reference resistors. Compensated detector current is integrated by a switched capacitor integrator with offset cancellation capability followed by a sample-and-hold circuit. The measured detector referred current noise is 47.2 pA in an electrical bandwidth of 2.6 KHz, corresponding to an expected SNR of 530. The dynamic nonuniformity compensation circuit uses a feedback structure that dynamically changes the bias currents of the reference and detector resistors. A special feature of the circuit is that it provides continuous compensation for the detector and reference resistances due to temperature changes over time. Test results of the fabricated circuit show that the circuit reduces the offset current due to resistance nonuniformity 42.5 times. However, the calculated detector referred current noise is 360 pA, which limits the circuit SNR to 70. The improved CTIA type readout circuit introduces a new detector biasing method by using an additional auxiliary biasing transistor for better current controllability. The improved readout circuit alleviates the need for high resolution compensation DACs, which drastically decreases the circuit area. The circuit occupies an area of one seventh of the first design. According to test results, the current compensation ratio is 170, and the detector referred current noise is 48.6 pA in a 2.6 KHz bandwidth.

The objective of this thesis is aimed at the design of low noise amplifier (LNA) for an ultra-wideband (UWB) receiver system using standard 0.18um CMOS process. A two amplified stage topology is proposed in the low noise amplifier. The first stage introduces inductively source degeneration and resistive-feedback, it can achieve wideband input impedance matching. The second stage introduces traditional CS configuration, it can improve the forward gain (S21). The second stage also used L-C section for output match. In order to improve the gain at high frequency, we introduces the series peaking between the first stage and second stage. The total power dissipation of the low noise amplifier is about 24.3mW at power supply 1.5 volt and the chip size is 1.283*1.008mm2. The simulated result shows that S11 is under -8dB, S22 is under -10dB, the forward gain S21 is 12.6dB~15.3dB at 3.1-10.6GHz, the reverse isolation S12 is under -30dB, and the noise figure is 3.24dB~4.84dB.

Drift time ion mobility spectrometry (DTIMS) is a rapid post ionization gas-phase separation technique that distinguishes between compounds based on their differences in reduced mass, charge and collisional cross-section while under a weak, time-invariant electric field. Standalone DTIMS is currently employed throughout the world for the detection of explosives, drugs and chemical-warfare agents. The coupling of IMS to MS (IM-MS) has enabled the performance of time-nested multidimensional separations with high sample throughput and enhanced peak capacity, allowing for the separation of ions not only based on their mass/charge (m/z) ratios, but also their shape. This allows for the elucidation of valuable structural information that can be utilized for determining gas phase ion conformation and differentiation between closely related ionic species. Over the past decade, these advances have transformed IM-MS applications and instrumental designs into one of the most rapidly growing areas of mass spectrometry. The work presented in this thesis is aimed at the development and subsequent characterization of a novel high-resolution resistive-glass atmospheric pressure DTIMS, and the application of this prototype DTIMS to the detection of environmentally relevant compounds. A review of the different types of ion mobility spectrometers, their principles of operation, and the advantages and disadvantages of each type are presented in Chapter 1. Chapter 2 describes the design and development of our prototype resistive glass DTIMS. A detailed description of the IMS hardware, including the ion sources, custom-built control computer, pulsing electronics, data acquisition system, and the timing schemes developed to operate the instrument in standalone DTIMS, multiplexed DTIMS, and IM-MS mode, are presented. Chapter 3 presents an initial characterization of the performance of a prototype resistive glass DTIMS under a wide range of instrumental parameters and also characterizes the radial ion distribution of the ions in the drift region of the spectrometer. Chapter 4 addresses the lack of sensitivity in DTIMS and explores ion trapping and multiplexing methods, introduces the principles of multiplexing and describes an extended multiplexing approach that encompasses arbitrary binary ion injection waveforms with variable duty cycles. Chapter 5 presents a detailed theoretical and experimental study of the separation power of our DTIMS and presents an evaluation of the field homogeneity and the performance of the ion gate.

As hydrogen is increasingly used as an energy carrier, gas sensors that can operate at high temperatures and in harsh environments are needed for fuel cell, aerospace, and automotive applications. The high temperature Fischer-Tropsch process also uses mixtures of hydrogen and carbon monoxide to generate synthetic fuels from non-fossil precursors. As the Fischer-Tropsch process depends upon particular gas mixtures to generate various fuels, a sensor which can determine the proper ratio of reactants is needed. To this end, gallium nitride (GaN) has been used to fabricate a resistive gas sensor. GaN is a suitable semiconductor to be used in hydrogen because of a wide, direct bandgap and greater stability than many other semiconductors. Additionally, resistive sensors offer several advantages in design compared to other types of sensors. Response time of resistive sensors is faster than those of other semiconductor sensors because catalytic and diffusion steps are not part of the response mechanism. Instead, a thermal detection mechanism is employed in resistive sensors. In this work, sensor response to changes in hydrogen concentration in nitrogen was measured at 200°C and 300°C. Sensor response was measured as change in current from a reference response to pure nitrogen at each temperature under a constant 2.5 V bias. Isothermal operation was achieved by controlling sensor temperature and pre-heating gas mixtures. Sensitivity to concentration increased upon an increase in temperature. Additionally, sensor response to concentration changes of H2 in CO at 50 °C was demonstrated. Sensors show similar responses to nitrogen and carbon monoxide mixtures, which have similar thermal properties. Using the thermal detection mechanism of the sensors, a correlation was shown between sensor response and a gas mixture thermal conductivity.

Kyoto University (京都大学) / 0048 / 新制・課程博士 / 博士(エネルギー科学) / 甲第19091号 / エネ博第315号 / 新制||エネ||64 / 32042 / 京都大学大学院エネルギー科学研究科エネルギー基礎科学専攻 / (主査)教授 岸本 泰明, 教授 前川 孝, 教授 中村 祐司 / 学位規則第4条第1項該当