Silicon Integrated HBV Frequency Multipliers for THz Applications

This thesis deals with integrated varactor diode circuits for terahertz (THz) applications. In particular hybrid, monolithic microwave integrated circuits (MMICs), and heterogeneous integration are explored for frequency multiplier applications. Each of these techniques addresses different requirements for high power and high frequency electronic circuits. Namely: high thermal conductivity (κ) of substrates for enhanced power capabilities, process reproducibility of small diode and circuit component dimensions, and finally machining properties for enhanced robustness and functionality. A fixed tuned 175 GHz frequency quintupler with a flip-chip assembled Heterostructure Barrier Varactor (HBV) diode was demonstrated. The microstrip circuit was fabricated on AlN substrate - a material with high thermal conductivity. The device delivers 60 mW of output power corresponding to 6.3 % conversion efficiency. The heteregeneous integration of In0.53Ga0.47As/Al0.48Ga0.52As HBV material structure onto silicon and silicon-on-insulator (SOI) substrate was done in a process employing low temperature plasma assisted wafer bonding. Using this technology a frequency tripler (×3) for W-band (75-110 GHz) and frequency quintupler (×5) for 474 GHz were fabricated. The performance of the W-band frequency tripler delivering more than 180 mW of output power is comparable to the identical design in InP MMIC technology. The 474 GHz frequency quintupler circuit was fabricated on SOI substrate, hence robust and unform 20 μm thick circuits were achieved. This multiplier delivers 2.8 mW of output power, and it represents the highest frequency of operation for HBV-based frequency multipliers. By enabling the integration of compound semiconductors onto a silicon substrate, an increase in the performance and functionality of the device is achieved. Moreover, due to good thermal and mechanical properties of silicon, as well as established process technology for this material, a new generation of THz monolithic integrated circuits is possible

Solid-Liquid Composites for Soft Multifunctional Materials

Soft materials with a liquid component are an emerging paradigm in materials design. The incorporation of a liquid phase, such as water, liquid metals, or complex fluids, into solid materials imparts unique properties and characteristics that emerge as a result of the dramatically different properties of the liquid and solid. Especially in recent years, this has led to the development and study of a range of novel materials with new functional responses, with applications in topics including soft electronics, soft robotics, 3D printing, wet granular systems and even in cell biology. Here we provide a review of solid-liquid composites, broadly defined as a material system with at least one, phase-separated liquid component, and discuss their morphology and fabrication approaches, their emergent mechanical properties and functional response, and the broad range of their applications

Nanostructured porous materials form Micro- and nano-electronics applications

This thesis work presents new research on porous silicon technologies for the heterogeneous integration on silicon platforms, as a key enabling technology for future 3D integrated systems. Porous silicon can be obtained with CMOS compatible processes on localized area on silicon wafer and, due to its tunable electrical, mechanical and thermal characteristics is an effective buffer material. Moreover, macroporous morphologies of porous silicon can can be exploited for the realization of “bed-of-nails” type through wafer interconnects, paving the way to high density, low-cost, through silicon vias. This work is divided in three parts: the first part introduces porous silicon, summarizes the available literature and presents process characterization for the porous layers obtained in this work and their properties; the second part describes the layer transfer technology and the buried cavities technologies developed in this work using the porous layers presented in the previous part; the last part introduces two applications of the layer transfer technology: compliant contacts and integrated physically small antennas

ReSCon '12, Research Student Conference: Book of Abstracts

The fifth SED Research Student Conference (ReSCon2012) was hosted over three days, 18-20 June 2012, in the Hamilton Centre at Brunel University. The conference consisted of 130 oral and 70 poster presentations, based on the high quality and diverse research being conducted within the School of Engineering and Design by postgraduate research students. The conference is held annually, and ReSCon plays a key role in contributing to research and innovations within the School

Feature Papers in Electronic Materials Section

This book entitled "Feature Papers in Electronic Materials Section" is a collection of selected papers recently published on the journal Materials, focusing on the latest advances in electronic materials and devices in different fields (e.g., power- and high-frequency electronics, optoelectronic devices, detectors, etc.). In the first part of the book, many articles are dedicated to wide band gap semiconductors (e.g., SiC, GaN, Ga2O3, diamond), focusing on the current relevant materials and devices technology issues. The second part of the book is a miscellaneous of other electronics materials for various applications, including two-dimensional materials for optoelectronic and high-frequency devices. Finally, some recent advances in materials and flexible sensors for bioelectronics and medical applications are presented at the end of the book

12th EASN International Conference on "Innovation in Aviation & Space for opening New Horizons"

Epoxy resins show a combination of thermal stability, good mechanical performance, and durability, which make these materials suitable for many applications in the Aerospace industry. Different types of curing agents can be utilized for curing epoxy systems. The use of aliphatic amines as curing agent is preferable over the toxic aromatic ones, though their incorporation increases the flammability of the resin. Recently, we have developed different hybrid strategies, where the sol-gel technique has been exploited in combination with two DOPO-based flame retardants and other synergists or the use of humic acid and ammonium polyphosphate to achieve non-dripping V-0 classification in UL 94 vertical flame spread tests, with low phosphorous loadings (e.g., 1-2 wt%). These strategies improved the flame retardancy of the epoxy matrix, without any detrimental impact on the mechanical and thermal properties of the composites. Finally, the formation of a hybrid silica-epoxy network accounted for the establishment of tailored interphases, due to a better dispersion of more polar additives in the hydrophobic resin

Semiconducting Polymers for Electronic Biosensors and Biological Interfaces

Bioeletronics aims at the direct coupling of biomolecular function units with standard electronic devices. The main limitations of this field are the material needed to interface soft living entities with hard inorganic devices. Conducting polymers enabled the bridging between these two separate worlds, owing to their biocompatibility, soft nature and the ability to be tailored according to the required application. In particular, the intrinsically conductive poly(3,4-ethylenedioxythiophene):poly(styrenesulfonic acid) (PEDOT:PSS) is one of the most promising polymers, having an excellent chemical and thermal stability, reversible doping state and high conductivity. This thesis relies on the use of PEDOT:PSS as semiconducting material for biological interfaces and biosensors. In detail, OECTs were demonstrated to be able to real-time monitor growth and detachment of both strong-barrier and no-barrier cells, according to the patterning of the device active area and the selected geometry. Thus, these devices were employed to assess silver nanoparticles (AgNPs) toxicity effects on cell lines, allowing further insights on citrate-coated AgNPs uptake by the cells and their toxic action, while demonstrating no cytotoxic activity of EG6OH-coated AgNPs. Moreover, PEDOT:PSS OECTs were proved to be capable of detecting oxygen dissolved in KCl or even cell culture medium, in the oxygen partial pressure range of 0-5%. Furthermore, PEDOT:PSS OECTs were biofunctionalized to impart specificity on the device sensing capabilities, through a biochemical functionalization strategy, electrically characterized. The resulting devices showed a proof of concept detection of a fundamental cytokine for cells undergoing osteogenic differentiation. Finally, PEDOT:PSS thickness-controlled films were employed as biocompatible, low-impedance and soft interfaces between the animal nerve and a gold electrode. The introduction of the plasticizer polyethylene glycol (PEG) enhanced the elasticity of the polymer, while keeping good conductivity and low-impedance properties. An in-vivo, chronic recording of the renal sympathetic nerve activity in rats demonstrated the efficiency of the device

Safety and Reliability - Safe Societies in a Changing World

The contributions cover a wide range of methodologies and application areas for safety and reliability that contribute to safe societies in a changing world. These methodologies and applications include: - foundations of risk and reliability assessment and management - mathematical methods in reliability and safety - risk assessment - risk management - system reliability - uncertainty analysis - digitalization and big data - prognostics and system health management - occupational safety - accident and incident modeling - maintenance modeling and applications - simulation for safety and reliability analysis - dynamic risk and barrier management - organizational factors and safety culture - human factors and human reliability - resilience engineering - structural reliability - natural hazards - security - economic analysis in risk managemen