Self-supporting graphene films and their applications

The self-supporting monolayer material which is graphene has excited enormous interest over the ten years since its discovery due to its remarkable electrical, mechanical thermal and chemical properties. In this paper we describe our work to develop chemical vapour deposition methods to grow monolayer graphene on copper foil substrates and the subsequent transfer process. Raman microscopy, scanning electron microscopy and atomic force microscopy (AFM) are used to examine the quality of the transferred material. To demonstrate the process we describe transfer onto patterned SiO2/Si substrates which forms freely suspended graphene with focus on circular wells forming graphene drums. These show interesting mechanical properties which are being explored as nanomechanical resonators.UK NMS Programme, the EU EMRP (European Metrology Research Programme) projects MetNEMS and GraphOh

Capteur d’hydrogène mos et méthode d’intégration à une technologie de transistor FDSOI

Abstract: hydrogen can be used as an energy carrier (storage) by the renewable energy industry as well as the automotive industry (fuel cell). Other industries already use hydrogen such, food processing and petroleum refineries. Hydrogen is odorless, transparent, and has a lower explosive limit of 4 %. Reliable, fast sensor are essential tools for a hydrogen safe environment. The work of this thesis provides a semiconductor-based hydrogen sensing solution. A MOS capacitor using a CMOS compatible novel Pt/Ti/ALD-Al2O3/p-Si stack. The Pt/Ti/Al2O3 sensing interface materials thicknesses are 100/5/38 nm respectively. The device can detect very low concentrations < 20 ppm. Furthermore, for a concentration of 500 ppm the response time is 56 s. the impact of testing conditions such temperature, and total gas flow have been studied. Results show that at 60℃ the device does not respond to hydrogen. And at 80℃ or higher the sensing response time is significantly reduced with increasing temperature. Furthermore, the total gas flow has an impact on the device response time and shows that a portion of the time response delay can be attributed to the chamber’s volume. Moreover, a heterogeneous integration method has been designed and presented. The latter represents a great tool for a flexible prototyping of sensors using FDSOI transistor technology. The integration has been simulated and results show promising results. The capacitive coupling feature in the FDSOI between the front and back gate is used to amplify the potential variation at the front gate. For instance, a 0.3 V hydrogen induced dipole potential can be amplified by a factor of 14 x.Le travail de cette thèse comprend la conception et la fabrication d’une technologie de capteur d’hydrogène basée sur une structure MOS. La structure est composée d’un empilement de Pt/Ti/Al2O3/p-Si. Les épaisseurs des matériaux utilisés pour la fabrication sont 100/5/38 nm (Pt/Ti/Al2O3) sur un substrat de silicium. Le capteur est capable de détecter de très faibles concentrations < 20 ppm. De plus, pour une concentration de 500 ppm, le temps de réponse est 56 s. L’impact de plusieurs conditions de test, comprenant la température et le débit total dans la chambre a été évalué. Les résultats montrent qu’à 60℃ le dispositive n’est pas capable de détecter la présence d’hydrogène. Cependant, à partir d’une température de 80℃, la réponse est très importante et le temps diminue pour encore des températures plus élevées. Le débit total dans la chambre a aussi démontré un impact sur le temps de réponse du capteur. Ce qui est aussi relié au volume de la chambre. Une intégration hétérogène ensuite a été conçue et présentée. Cette dernière est un outil flexible pour le prototypage avec des technologies de transistor FDSOI. L’intégration des deux dispositifs a été effectuée et montre de résultats prometteurs. Le couplage capacitif entre la grille avant et la grille arrière du transistor FDSOI permet d’amplifier le signal du capteur. Par exemple, une variation de potentiel de 0.3 V peut être amplifier par un facteur de 14 x, donc 4.19 V

Solid State Circuits Technologies

The evolution of solid-state circuit technology has a long history within a relatively short period of time. This technology has lead to the modern information society that connects us and tools, a large market, and many types of products and applications. The solid-state circuit technology continuously evolves via breakthroughs and improvements every year. This book is devoted to review and present novel approaches for some of the main issues involved in this exciting and vigorous technology. The book is composed of 22 chapters, written by authors coming from 30 different institutions located in 12 different countries throughout the Americas, Asia and Europe. Thus, reflecting the wide international contribution to the book. The broad range of subjects presented in the book offers a general overview of the main issues in modern solid-state circuit technology. Furthermore, the book offers an in depth analysis on specific subjects for specialists. We believe the book is of great scientific and educational value for many readers. I am profoundly indebted to the support provided by all of those involved in the work. First and foremost I would like to acknowledge and thank the authors who worked hard and generously agreed to share their results and knowledge. Second I would like to express my gratitude to the Intech team that invited me to edit the book and give me their full support and a fruitful experience while working together to combine this book

Wearable Nano-Based Gas Sensors for Environmental Monitoring and Encountered Challenges in Optimization

With a rising emphasis on public safety and quality of life, there is an urgent need to ensure optimal air quality, both indoors and outdoors. Detecting toxic gaseous compounds plays a pivotal role in shaping our sustainable future. This review aims to elucidate the advancements in smart wearable (nano)sensors for monitoring harmful gaseous pollutants, such as ammonia (NH3), nitric oxide (NO), nitrous oxide (N2O), nitrogen dioxide (NO2), carbon monoxide (CO), carbon dioxide (CO2), hydrogen sulfide (H2S), sulfur dioxide (SO2), ozone (O3), hydrocarbons (CxHy), and hydrogen fluoride (HF). Differentiating this review from its predecessors, we shed light on the challenges faced in enhancing sensor performance and offer a deep dive into the evolution of sensing materials, wearable substrates, electrodes, and types of sensors. Noteworthy materials for robust detection systems encompass 2D nanostructures, carbon nanomaterials, conducting polymers, nanohybrids, and metal oxide semiconductors. A dedicated section dissects the significance of circuit integration, miniaturization, real-time sensing, repeatability, reusability, power efficiency, gas-sensitive material deposition, selectivity, sensitivity, stability, and response/recovery time, pinpointing gaps in the current knowledge and offering avenues for further research. To conclude, we provide insights and suggestions for the prospective trajectory of smart wearable nanosensors in addressing the extant challenges

Nano-Bio Hybrid Electronic Sensors for Chemical Detection and Disease Diagnostics

The need to detect low concentrations of chemical or biological targets is ubiquitous in environmental monitoring and biomedical applications. The goal of this work was to address challenges in this arena by combining nanomaterials grown via scalable techniques with chemical receptors optimized for the detection problem at hand. Advances were made in the CVD growth of graphene, carbon nanotubes and molybdenum disulfide. Field effect transistors using these materials as the channel were fabricated using methods designed to avoid contamination of the nanomaterial surfaces. These devices were used to read out electronic signatures of binding events of molecular targets in both vapor and solution phases. Single-stranded DNA functionalized graphene and carbon nanotubes were shown to be versatile receptors for a wide variety of volatile molecular targets, with characteristic responses that depended on the DNA sequence and the identity of the target molecule, observable down to part-per-billion concentrations. This technology was applied to increasingly difficult detection challenges, culminating in a study of blood plasma samples from patients with ovarian cancer. By working with large arrays of devices and studying the devices\u27 responses to pooled plasma samples and plasma samples from 24 individuals, sufficient data was collected to identify statistically robust patterns that allow samples to be classified as coming from individuals who are healthy or have either benign or malignant ovarian tumors. Solution-phase detection experiments focused on the design of surface linkers and specific receptors for medically relevant molecular targets. A non-covalent linker was used to attach a known glucose receptor to carbon nanotubes and the resulting hybrid was shown to be sensitive to glucose at the low concentrations found in saliva, opening up a potential pathway to glucose monitoring without the need for drawing blood. In separate experiments, molybdenum disulfide transistors were functionalized with a re-engineered variant of a μ-opiod receptor, a cell membrane protein that binds opiods and regulates pain and reward signaling in the body. The resulting devices were shown to bind opiods with affinities that agree with measurements in the native state. This result could enable not only an advanced opiod sensor but moreover could be generalized into a solid-state drug testing platform, allowing the interactions of novel pharmaceuticals and their target proteins to be read out electronically. Such a system could have high throughput due to the quick measurement, scalable device fabrication and high sensitivity of the molybdenum disulfide transistor

NanoPhotonic structures for biosensing applications

Photonics -“ science of optics“ - has become one of the emerging sciences in many applications nowadays. The study of light interaction with matter has opened a lot of interesting phenomena that differ in their applications including sensing, modulation, demultiplexing, etc. Sensing applications represent a major part in the photonics field owing to their crucial role in the detecting and diagnosis of diseases in many medical applications. On the other hand, gas sensing is considered an important application in many industrial centers. During the manufacturing of several products, toxic gases may be generated and hence the ability to detect such types of gases becomes a necessity. The first part of this thesis is concerned with sensing applications using plasmonic and photonic structures. Several plasmonic and photonic structures are proposed that are characterized by their ultimate sensitivity and high performance. Other parameters are taken into consideration like the CMOS compatibility of our design and the possibility of being integrated with electronic chips. Beside optical sensing and their important role in biomedical and environmental applications, optical demultiplexers are considered from the main blocks in different communication systems that are based on wavelength division multiplexing (WDM). The need to highly select certain wavelength to carry the data during transmission is increasing. In the second part of the thesis, the design methodology of an optical filter is discussed. The optical filter can fit into many applications including demultiplexing and sensing. An optical demultiplexer is proposed and characterized by its high selectivity of wavelength in the near-infrared range to fit with the telecommunication systems. In addition, the transmission levels are of an acceptable range to ensure high signal to noise ratio. 9 The third and the last part of the thesis is concerned with optical coupling from free-space to guided structures. In the last part, an optical grating coupler is proposed that is characterized by its high transmission levels. The grating coupler couples the light from free-space to a shallow waveguide with a narrow lateral dimension. Such system can fit in many applications including sensing and modulation applications

Nano/biosensors Based On Large-Area Graphene

Two dimensional materials have properties that make them ideal for applications in chemical and biomolecular sensing. Their high surface/volume ratio implies that all atoms are exposed to the environment, in contrast to three dimensional materials with most atoms shielded from interactions inside the bulk. Graphene additionally has an extremely high carrier mobility, even at ambient temperature and pressure, which makes it ideal as a transduction device. The work presented in this thesis describes large-scale fabrication of Graphene Field Effect Transistors (GFETs), their physical and chemical characterization, and their application as biomolecular sensors. Initially, work was focused on developing an easily scalable fabrication process. A large-area graphene growth, transfer and photolithography process was developed that allowed the scaling of production of devices from a few devices per single transfer in a chip, to over a thousand devices per transfer in a full wafer of fabrication. Two approaches to biomolecules sensing were then investigated, through nanoparticles and through chemical linkers. Gold and platinum Nanoparticles were used as intermediary agents to immobilize a biomolecule. First, gold nanoparticles were monodispersed and functionalized with thiolated probe DNA to yield DNA biosensors with a detection limit of 1 nM and high specificity against noncomplementary DNA. Second, devices are modified with platinum nanoparticles and functionalized with thiolated genetically engineered scFv HER3 antibodies to realize a HER3 biosensor. Sensors retain the high affinity from the scFv fragment and show a detection limit of 300 pM. We then show covalent and non-covalent chemical linkers between graphene and antibodies. The chemical linker 1-pyrenebutanoic acid succinimidyl ester (pyrene) stacks to the graphene by Van der Waals interaction, being a completely non-covalent interaction. The linker 4-Azide-2,3,5,6-tetrafluorobenzoic acid, succinimidyl ester (azide) is a photoactivated perfluorophenyl azide that covalently binds to graphene. A comparison is shown for genetically engineered scFv HER3 antibodies and show a low detection limit of 10 nM and 100 pM for the pyrene and azide, respectively. Finally, we use the azide linker to demonstrate a large-scale fabrication of a multiplexed array for Lyme disease. Simultaneous detection of a mixture of two target proteins of the Lyme disease bacterium (Borrelia burgdorferi), this is done by separating the antibodies corresponding to each target in the mixture to different regions of the chip. We show we can differentiate concentrations of the two targets

Doctor of Philosophy

dissertationRealization of next generation spintronic devices will require the use of design and engineering of new materials. In order to reach the performance requirements for spintronic transistor devices to become a reality, spin injection must be extremely efficient at room temperature. Understanding new materials and combinations of materials will enable the injection efficiency required for next-generation devices. Rare earth oxides are explored to determine the feasibility of doping magnetic elements to make new dilute magnetic dielectric materials for spin tunneling injection applications. Samarium Oxide (Sm2O3) doped with a small amount of cobalt (Co) is shown to exhibit a magnetic phenomenon which cannot be accounted for by conventional models. Though the observed magnetic properties appear quite similar to those observed in superparamagnetic systems, the origin of these properties is entirely different. A model, based on the widely accepted bound polaron theory for insulating ferromagnets, is proposed to explain the magnetic behavior of Co doped Sm2O3 films. We have also explored the growth and properties of high quality Tb2O3 thin films with on a variety of substrates in preparation for magnetic doping. We show enhanced dielectric constant related to improved crystal quality compared with previous reports, which makes this material of interest in high-k applications as well. Furthermore, we report room-temperature, all-electrical injection and detection of spin-polarized carriers in silicon using NiFe/MgO tunnel-barrier-contacts. From the magnetic-field dependence of the spin-accumulation voltage, spin-lifetime and diffusion-length of the carriers were determined to be 276 ps and 328 nm, respectively. Attaining spin diffusion lengths of >320 nm in Si channels is a ground breaking step and opens tremendous opportunities for integrating spin functionality into post-Moore-era electronic devices. We have carried out similar research with ZnO channels. We report all-electrical injection and detection of spin-polarized carriers in ZnO using NiFe/MgO tunnel-barrier-contacts. The three-terminal Hanle effect is used to study spin transport in single crystal thin film ZnO grown on sapphire. The results show that spin injection persists up to and above room temperature, with a measured lifetime τs=174 ps at 340K. These results underscore the importance of ZnO as a material for future active spintronics devices