Fundamental design principles of novel MEMS based Landau switches, sensors, and actuators : Role of electrode geometry and operation regime

Microelectromechanical systems (MEMS) are considered as potential candidates for More-Moore and More-than-Moore applications due to their versatile use as sensors, switches, and actuators. Examples include accelerometers for sensing, RF-MEMS capacitive switches in communication, suspended-gate (SG) FETs in computation, and deformable mirrors in optics. In spite of the wide range of applications of MEMS in diverse fields, one of the major challenges for MEMS is their instability. Instability divides the operation into stable and unstable regimes and poses fundamental challenges for several applications. For example: Tuning range of deformable mirrors is fundamentally limited by pull-in instability, RF-MEMS capacitive switches suffer from the problem of hard landing, and intrinsic hysteresis of SG-FETs puts a lower bound on the minimum power dissipation. ^ In this thesis, we provide solutions to the application specific problems of MEMS and utilize operation in or close to unstable regime for performance enhancement in several novel applications. Specifically, we propose the following: (i) novel device concepts with nanostructured electrodes to address the aforementioned problems of instability, (ii) a switch with hysteresis-free ideal switching characteristics based on the operation in unstable regime, and (iii) a Flexure biosensor that operates at the boundary of the stable and unstable regimes to achieve improved sensitivity and signal-to-noise ratio. In general, we have advocated electrode geometry as a design variable for MEMS, and used MEMS as an illustrative example of Landau systems to advocate operation regime as a new design variabl

Electrical Characterisation of Ferroelectric Field Effect Transistors based on Ferroelectric HfO2 Thin Films

Ferroelectric field effect transistor (FeFET) memories based on a new type of ferroelectric material (silicon doped hafnium oxide) were studied within the scope of the present work. Utilisation of silicon doped hafnium oxide (Si:HfO2) thin films instead of conventional perovskite ferroelectrics as a functional layer in FeFETs provides compatibility to the CMOS process as well as improved device scalability. The influence of different process parameters on the properties of Si:HfO2 thin films was analysed in order to gain better insight into the occurrence of ferroelectricity in this system. A subsequent examination of the potential of this material as well as its possible limitations with the respect to the application in non-volatile memories followed. The Si:HfO2-based ferroelectric transistors that were fully integrated into the state-of-the-art high-k metal gate CMOS technology were studied in this work for the first time. The memory performance of these devices scaled down to 28 nm gate length was investigated. Special attention was paid to the charge trapping phenomenon shown to significantly affect the device behaviour.:1 Introduction 2 Fundamentals 2.1 Non-volatile semiconductor memories 2.2 Emerging memory concepts 2.3 Ferroelectric memories 3 Characterisation methods 3.1 Memory characterisation tests 3.2 Ferroelectric memory specific characterisation tests 3.3 Trapping characterisation methods 3.4 Microstructural analyses 4 Sample description 4.1 Metal-insulator-metal capacitors 4.2 Ferroelectric field effect transistors 5 Stabilisation of the ferroelectric properties in Si:HfO2 thin films 5.1 Impact of the silicon doping 5.2 Impact of the post-metallisation anneal 5.3 Impact of the film thickness 5.4 Summary 6 Electrical properties of the ferroelectric Si:HfO2 thin films 6.1 Field cycling effect 6.2 Switching kinetics 6.3 Fatigue behaviour 6.4 Summary 7 Ferroelectric field effect transistors based on Si:HfO2 films 7.1 Effect of the silicon doping 7.2 Program and erase operation 7.3 Retention behaviour 7.4 Endurance properties 7.5 Impact of scaling on the device performance 7.6 Summary 8 Trapping effects in Si:HfO2-based FeFETs 8.1 Trapping kinetics of the bulk Si:HfO2 traps 8.2 Detrapping kinetics of the bulk Si:HfO2 traps 8.3 Impact of trapping on the FeFET performance 8.4 Modified approach for erase operation 8.5 Summary 9 Summary and Outloo

Electronic Nanodevices

The start of high-volume production of field-effect transistors with a feature size below 100 nm at the end of the 20th century signaled the transition from microelectronics to nanoelectronics. Since then, downscaling in the semiconductor industry has continued until the recent development of sub-10 nm technologies. The new phenomena and issues as well as the technological challenges of the fabrication and manipulation at the nanoscale have spurred an intense theoretical and experimental research activity. New device structures, operating principles, materials, and measurement techniques have emerged, and new approaches to electronic transport and device modeling have become necessary. Examples are the introduction of vertical MOSFETs in addition to the planar ones to enable the multi-gate approach as well as the development of new tunneling, high-electron mobility, and single-electron devices. The search for new materials such as nanowires, nanotubes, and 2D materials for the transistor channel, dielectrics, and interconnects has been part of the process. New electronic devices, often consisting of nanoscale heterojunctions, have been developed for light emission, transmission, and detection in optoelectronic and photonic systems, as well for new chemical, biological, and environmental sensors. This Special Issue focuses on the design, fabrication, modeling, and demonstration of nanodevices for electronic, optoelectronic, and sensing applications

Magnetic sensors based on topological insulators

The ever-increasing demands for higher computing capabilities and low energy consumption has necessitated the developing of micro or nano electronics and sensors. This results in increasing demand for faster, higher performance, more compact and low energy consumption devices and sensors which pushes microelectronics to its physical limit. Driven by size, cost, sensitivity, reliability and power consumption, the electronic and magnetic related devices are entering a completely new age where innovations on new materials and physics are being explored. Among the most promising materials, magnetoelectric multiferroic (MEMF) and topological insulators (TI) have attracted a great deal of interest, since they are promising for their unique properties and innovative applications. The coupling of electric and magnetic properties of MEMF and the ultrahigh surface carrier mobility of TI enlighten the design of devices with extremely low thermal losses and energy cost. However, most of the device implementations of these material systems are still in status of ideas and laboratory prototypes. The prospects of practical realization of devices based on MEMF and TI encounter several critical challenges: the low ME coupling coefficient and current leakage in magnetoelectric(ME) sensor; fabrication large scale, low roughness and large terrace width of TI thin films for industry utilization; the high bulk conductivity and low sensitivity of TI based magnetic sensors. The present thesis will address some problems and challenges based on the above questions. In this work, several aspects regarding to achieve a high performance and low energy consuming devices were investigated including: systemically studied and manipulated the energy band structure of TI for nanosized electronics and sensors application; developed Hall effect sensor and anomalous Hall effect sensor based on magnetically doped topological insulator; explored a method to increase the ME coupling coefficient of ME sensors; There are nine chapters in this dissertation. Chapter 1 gives general background to readers on magnetic sensors which used widely in daily life. Basic physics of two kinds of important materials: topological insulators and MEMF composites will also be introduced. Besides that, chapter 1 will also introduce a proposed switching device which integrates both two kinds of materials. The last part of chapter 1 will be the motivation and objectives of work in this dissertation. Chapter 2 will review the experiments, techniques and equipment used for research in this dissertation including sample fabrication methods and testing methods. Starting from chapter 3, topological insulators material fabrication and sensor application will be introduced based on different kind of TIs. Study on MEMF sensors will be introduced in chapter 8. Chapter 9 is a summary of all the work and gives some general conclusions of this dissertation

On Demand Nanoscale Phase Manipulation of Vanadium Dioxide by Scanning Probe Lithography

This dissertation focuses on nanoscale phase manipulations of Vanadium Dioxide. Nanoscale control of material properties is a current obstacle for the next generation of optoelectronic and photonic devices. Vanadium Dioxide is a strongly correlated material with an insulator-metal phase transition at approximately 345 K that generates dramatic electronic and optical property changes. However, the development of industry device application based on this phenomenon has been limited thus far due to the macroscopic scale and the volatile nature of the phase transition. In this work these limitations are assessed and circumvented. A home-built, variable temperature, scanning near-field optical microscope was engineered for Vanadium Dioxide manipulations and detections. Using this instrument, various scanning probe lithography based methods are implemented to induce new nanoscale phases. Three new phase transitions are discovered; a monoclinic metallic at the nanoscale, a rutile metallic metastable phase, and a van der Waals layered insulator. These new phases are studied and characterized to further understand phase manipulations in strongly correlated materials. One of the new phase transitions, monoclinic metallic, showcases plasmonic excitations. This phenomenon is used to demonstrate various nanoplasmonic devices such as rewritable waveguides, spatially modulated resonators, and reconfigurable planar optics. Finally, Oxygen Vacancy diffusion of the monoclinic structure is monitored to determine the temporal limitation for device applications. The discovery, demonstration, and study of these phases clearly shows the ability to manipulate Vanadium Dioxide on the nanoscale for the first time. Phase control is accomplished under ambient conditions and is stable over long periods of time. This technology opens the door for multifunctional device application using strongly correlated materials

Annual Report 2009 - Institute of Ion Beam Physics and Materials Research

The Institute of Ion Beam Physics and Materials Research (IIM) is one of the six institutes of the Forschungszentrum Dresden-Rossendorf (FZD), and contributes the largest part to its Research Program \"Advanced Materials\", mainly in the fields of semiconductor physics and materials research using ion beams. The institute operates a national and international Ion Beam Center, which, in addition to its own scientific activities, makes available fast ion technologies to universities, other research institutes, and industry. Parts of its activities are also dedicated to exploit the infrared/THz free-electron laser at the 40 MeV superconducting electron accelerator ELBE for condensed matter research. For both facilities the institute holds EU grants for funding access of external users

Heterogeneous Integration in Switchmode Electronics

This dissertation looks closely at deployment of thin-film integrated inductors within power electronics, including details on the state-of-the-art technology for such inductors and related packaging techniques. Design challenges for systems using these inductors are discussed in detail, including the current outlook on magnetics development and the impact of these non-linearities on system design. In particular, this work looks closely at effects often left behind in modern discrete-component-based power module design, such as soft core saturation and significant high-frequency losses. In conjunction with the magnetics, a well-known non-linear controller for buck converters is analyzed in-depth for the first time, using frameworks from variable structure and sliding-mode control. This allows for development of a more profound rationale for the heuristic design guidelines that have been heretofore provided for this class of controllers. To verify the theoretical development, a testbench integrated CMOS front-end for a switched-inductor step-down, or buck converter is used to investigate departures of system behavior from the general wisdom around buck converter performance. Two packaging methodologies are explored for integration, and their impact on the design cycle and module lifetimes are discussed in some detail

Colossal electroresistance, magnetoimpedance, and magnetocaloric effects in selected manganites

Ph.DDOCTOR OF PHILOSOPH