Miniaturized Silicon Photodetectors

Silicon (Si) technologies provide an excellent platform for the design of microsystems where photonic and microelectronic functionalities are monolithically integrated on the same substrate. In recent years, a variety of passive and active Si photonic devices have been developed, and among them, photodetectors have attracted particular interest from the scientific community. Si photodiodes are typically designed to operate at visible wavelengths, but, unfortunately, their employment in the infrared (IR) range is limited due to the neglectable Si absorption over 1100 nm, even though the use of germanium (Ge) grown on Si has historically allowed operations to be extended up to 1550 nm. In recent years, significant progress has been achieved both by improving the performance of Si-based photodetectors in the visible range and by extending their operation to infrared wavelengths. Near-infrared (NIR) SiGe photodetectors have been demonstrated to have a “zero change” CMOS process flow, while the investigation of new effects and structures has shown that an all-Si approach could be a viable option to construct devices comparable with Ge technology. In addition, the capability to integrate new emerging 2D and 3D materials with Si, together with the capability of manufacturing devices at the nanometric scale, has led to the development of new device families with unexpected performance. Accordingly, this Special Issue of Micromachines seeks to showcase research papers, short communications, and review articles that show the most recent advances in the field of silicon photodetectors and their respective applications

Exploration of Miniature Flexible Devices Empowered by Van Der Waals Material

This research mainly focuses on the fabrication of miniature flexible devices empowered by van der Waals materials. Through the extensive experiments contained in this thesis, by exploring the characteristics of van der Waals materials, optimizing the manufacturing process of lithography technology, and characterizing the photoelectric performance of micro devices, this thesis has promoted the development of micro flexible device manufacturing and expanded its applications in the fields of biological detection, medical treatment, and environmental monitoring. We introduced a miniature van der Waals semiconductor empowered vertical color sensor, which saves three times the volume space compared to the traditional planer color sensor and includes multiple optical aberration correction functions as well. Such a small red, green, and blue (RGB) color sensor can be applied in bionic eyes, breaking through the limitations of existing black and white recognition. On this basis, we further explored the stretchability of two-dimensional materials represented by MoS2. We proposed a chemical treatment method combined with gold nanoparticles and (3-mercaptopropyl)trimethoxysilane (MPTMS) to realize the relocation of flexible micro devices. This method improves the adhesion between the material layer and the flexible substrate (PDMS), which significantly increases the flexible device stretchability, and prolongs its service life. Through the above work, this thesis explores the van der Waals materials’ properties, and optimizes the manufacturing process of micro devices, further exerts the advantages of material flexibility, therefore provides more possibilities for the development of smart wearable devices, biomedical detection, and other fields

Modifications of Graphene Prepared by Chemical Vapor Deposition for Diagnostic Applications

xx, 186 p.El grafeno es un alótropo de carbono que ha demostrado tener excelentes propiedades electrónicas, mecánicas y térmicas. Gracias a ello, tiene un gran potencial en campos como biomedicina o electrónica. Entre sus distintos derivados, el grafeno crecido por deposición química de vapor (CVD) y transferido sobre superficie, ha demostrado ser un material idóneo para este tipo de aplicaciones debido a su elevada conductividad, carácter ambipolar de efecto campo, y una relación calidad/coste de producción conveniente. Sin embargo, la investigación del grafeno aún está en sus inicios y es necesaria una alta reproducibilidad de sus resultados para la futura comercialización y estandarización de los dispositivos de grafeno. Para ello, en esta tesis se ha desarrollado un protocolo de limpieza posterior al proceso de litografía con el fin de eliminar los residuos poliméricos de dicho proceso y obtener el mejor rendimiento electrónico. Además, la implementación de capacidades sensóricas sobre dispositivos electrónicos como los transistores de grafeno permite el desarrollo de herramientas para diagnóstico y tratamiento de diversas condiciones neurológicas como epilepsia o Parkinson. Con este propósito, el grafeno ha sido modificado covalentemente vía una adición radicalaria siguiendo diferentes estrategias compatibles con el diseño del dispositivo, con el fin de anclar los bio-receptores de interés. Como prueba de concepto, el sistema descrito se usó con un aptámero selectivo para trombina, demostrando resultados prometedores.Así mismo, se demostró por primera vez el uso del grafeno CVD en espectrometría de masas MALDI-TOF gracias a su capacidad de ionización/desorción. En concreto, se ha desarrollado un sistema compuesto por diferentes azucares modificados sobre grafeno como herramienta diagnóstica para la detección de proteínas. En este dispositivo se usó el grafeno como superficie asistente para la ionización/desorción láser en espectrometría de masas que, combinado al carácter conductor del grafeno, ha permitido reemplazar ITO como material de soporte y trabajar en condiciones de ausencia de matriz

Graphene-coated substrates for biochemical and optoelectronic applications

Graphene - monolayer or a few layers of graphite -- has proven to possess remarkable properties: large thermal conductivity, mechanical robustness, two-dimensional ultra large electronic mobility, chemical inertness and biochemical compatibility. Realization of some applications has been impeded by lack of a large area deposition method. By using a novel methodology to deposit graphene on solid and perforated substrates, various optoelectronic and biochemical elements have been demonstrated in this thesis: (1) graphene based transistors were fabricated and their characteristics were assessed. The mobility for such transistors exceeded 5000 cm2/V·s, much larger than their silicon based counterparts. Such attribute opens up new potential application in the field of very large scale integration (VLSI). (2) In parallel to vacuum tubes, where accelerated electrons are retained by a biased screen, a graphene based retaining electrode, placed in a wet-cell battery has stopped the battery’s current. In that respect, graphene proved to be a good ionic screening electrode because it does not oxidize easily. Applications could be in the field of ionic transistors and special electrochemical cells. (3) As surface pl asmon waveguides enter the electronic circuitry, surface plasmon sources are required. Graphene based surface pl asmons lasers were fabricated and characterized. Their attributes, illustrated by operational threshold, gain, spectral line narrowing and feedback at 630 nm all alluded to the action of a laser. Such, local pl asmonic sources may find applications in optoelectronic and sensor systems. (4) Infrared (IR) metal-mesh screens have been investigated as optical filters in the visible through the THz spectral region for astronomy and remote sensing applications. By interfacing these metal mesh screens with graphene, new spectroscopic platforms were fabricated. It has been shown that these platforms enhance I R and Raman signals of molecules and, specifically, signal of bio-species at the screens\u27 surface. Biochemical sensing applications are envisioned. (5) Finally, the Raman spectra of molecules, deposited on graphene-coated nano-hole arrays have been investigated. It has been shown that these platforms were able to intensify such Raman signals, significantly. Potential usage of such platforms as biochemical sensors is envisioned

Applications of MXenes in human-like sensors and actuators

Human beings perceive the world through the senses of sight, hearing, smell, taste, touch, space, and balance. The first five senses are prerequisites for people to live. The sensing organs upload information to the nervous systems, including the brain, for interpreting the surrounding environment. Then, the brain sends commands to muscles reflexively to react to stimuli, including light, gas, chemicals, sound, and pressure. MXene, as an emerging two-dimensional material, has been intensively adopted in the applications of various sensors and actuators. In this review, we update the sensors to mimic five primary senses and actuators for stimulating muscles, which employ MXene-based film, membrane, and composite with other functional materials. First, a brief introduction is delivered for the structure, properties, and synthesis methods of MXenes. Then, we feed the readers the recent reports on the MXene-derived image sensors as artificial retinas, gas sensors, chemical biosensors, acoustic devices, and tactile sensors for electronic skin. Besides, the actuators of MXene-based composite are introduced. Eventually, future opportunities are given to MXene research based on the requirements of artificial intelligence and humanoid robot, which may induce prospects in accompanying healthcare and biomedical engineering applications. [Figure not available: see fulltext.

21st Century Nanostructured Materials

Nanostructured materials (NMs) are attracting interest as low-dimensional materials in the high-tech era of the 21st century. Recently, nanomaterials have experienced breakthroughs in synthesis and industrial and biomedical applications. This book presents recent achievements related to NMs such as graphene, carbon nanotubes, plasmonic materials, metal nanowires, metal oxides, nanoparticles, metamaterials, nanofibers, and nanocomposites, along with their physical and chemical aspects. Additionally, the book discusses the potential uses of these nanomaterials in photodetectors, transistors, quantum technology, chemical sensors, energy storage, silk fibroin, composites, drug delivery, tissue engineering, and sustainable agriculture and environmental applications

Ultra-thin chips for high-performance flexible electronics

Flexible electronics has significantly advanced over the last few years, as devices and circuits from nanoscale structures to printed thin films have started to appear. Simultaneously, the demand for high-performance electronics has also increased because flexible and compact integrated circuits are needed to obtain fully flexible electronic systems. It is challenging to obtain flexible and compact integrated circuits as the silicon based CMOS electronics, which is currently the industry standard for high-performance, is planar and the brittle nature of silicon makes bendability difficult. For this reason, the ultra-thin chips from silicon is gaining interest. This review provides an in-depth analysis of various approaches for obtaining ultra-thin chips from rigid silicon wafer. The comprehensive study presented here includes analysis of ultra-thin chips properties such as the electrical, thermal, optical and mechanical properties, stress modelling, and packaging techniques. The underpinning advances in areas such as sensing, computing, data storage, and energy have been discussed along with several emerging applications (e.g., wearable systems, m-Health, smart cities and Internet of Things etc.) they will enable. This paper is targeted to the readers working in the field of integrated circuits on thin and bendable silicon; but it can be of broad interest to everyone working in the field of flexible electronics

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

Interfacing graphene with peripheral neurons: influence of neurite outgrowth and NGF axonal transport

Graphene displays properties that make it appealing for neuroregenerative medicine, yet the potential of large-scale highly-crystalline graphene as a conductive peripheral neural interface has been scarcely investigated. In particular, pristine graphene offers enhanced electrical properties that can be advantageous for nervous system regeneration applications. In this work, we investigate graphene potential as peripheral nerve interface. First, we perform an unprecedented analysis aimed at revealing how the typical polymeric coatings for neural cultures distribute on graphene at the nanometric scale. Second, we examine the impact of graphene on the culture of two established cellular models for peripheral nervous system: PC12 cell line and primary embryonic rat dorsal root ganglion (DRG) neurons, showing a better and faster axonal elongation using graphene. We then observe that the axon elongation in the first days of culture correlates to an altered nerve growth factor (NGF) axonal transport, with a reduced number of retrogradely moving NGF vesicles in favor of stalled vesicles. We thus hypothesize that the axon elongation observed in the first days of culture could be mediated by this pool of NGF vesicles locally retained in the medial/distal parts of axons. Furthermore, we investigate electrophysiological properties and cytoskeletal structure of peripheral neurons. We observe a reduced neural excitability and altered membrane potential together with a reduced inter-microtubular distance on graphene and correlate these electrophysiological and structural reorganizations of axon physiology to the observed vesicle stalling. Finally, the potential of another 2D material as neural interface, tungsten disulfide, is explored