Inorganic Electronic Materials Research Articles

Biomaterials and Electroactive Bacteria for Biodegradable Electronics.

The global production of unrecycled electronic waste is extensively growing each year, urging the search for alternatives in biodegradable electronic materials. Electroactive bacteria and their nanowires have emerged as a new route toward electronic biological materials (e-biologics). Recent studies on electron transport in cable bacteria—filamentous, multicellular electroactive bacteria—showed centimeter long electron transport in an organized conductive fiber structure with high conductivities and remarkable intrinsic electrical properties. In this work we give a brief overview of the recent advances in biodegradable electronics with a focus on the use of biomaterials and electroactive bacteria, and with special attention for cable bacteria. We investigate the potential of cable bacteria in this field, as we compare the intrinsic electrical properties of cable bacteria to organic and inorganic electronic materials. Based on their intrinsic electrical properties, we show cable bacteria filaments to have great potential as for instance interconnects and transistor channels in a new generation of bioelectronics. Together with other biomaterials and electroactive bacteria they open electrifying routes toward a new generation of biodegradable electronics.

Providing a Window into the Phase Behavior of Semiconducting Polymers

The targeted assembly of a wealth of functional architectures for soft photonics and electronics relies on a rigorous understanding of semiconducting polymer phase behavior. While many useful correlations have been established in the field of commodity plastics, unifying theories for their semiconducting counterparts are, however, more challenging to develop because of the rich phase behavior frequently displayed by these macromolecules, due in part to their complex chemical structures typically based on relatively rigid backbones and elaborate side-chain motifs. Solid-state structure formation and resulting properties are therefore especially sensitive to thermal and temporal parameters during processing, rendering device fabrication a challenging task that too often relies on time-consuming trial-and-error procedures. To understand the thermodynamic and kinetic factors of plastic semiconductor solidification and, for example, thin-film growth relevant for device fabrication, detailed knowledge of the intricacies of macromolecular semiconductors’ phase behavior must be gained and ideally combined with temperature/composition, temperature/confinement, and/or time/temperature/transformation- phase diagrams. This will open pathways toward a knowledge and methodology platform for the controlled materials assembly of soft electronics/photonics systems very much in analogy to the approaches used in metallurgy and the inorganic electronic materials field. In turn, a step change in how we design and process soft electronic products might be achieved, with impact on the broader soft matter area.

Advanced manufacturing for transient electronics

Abstract

(Invited) Large Photoluminescence Enhancement of Monolayer Molybdenum Disulfide Via Molecular Treatment

Molecular interaction is an essential process in various fields such as chemistry, biology and materials science. The interaction of molecules includes: 1) the local electron transfer process, 2) local chemical bonding and 3) assembling to form a structure. All three occur essentially from each molecule’s “recognition” ability. We are trying to extend the molecular interaction system onto inorganic electronic materials to harness the highest-performance of inorganic systems. In this presentation, I will present our recent results of molecular interaction on a semiconducting 2D material, transition metal dichalcogenides (TMDCs).1,2,3 TMDCs are constructed by stacking atomically-thin layers (thickness ~0.7 nm) with van der Waals interaction, and they are expected to generate tiny optoelectronic devices due to their thin nature. Since monolayer TMDC has a direct bandgap, it is a good platform for realizing atomically thin optoelectronic devices. However, an issue is their low luminescence brightness. For example, a representative TMDC, MoS­2, shows photoluminescence (PL) quantum yield of ~1% or less. In this presentation, I will show our recent results of improving the brightness of monolayer MoS2 dramatically (more than 100 times enhancement from the original) via molecular treatments. One method is using a superacid (bis(trifluoromethane)sulfonimide; TFSI) molecule.3 The superacid molecular treatment onto a monolayer MoS2 changes the PL quantum yield of MoS2 from 1% to near-unity. I will discuss the PL enhancement factor in the TFSI treatment on MoS2. The second method is using a redox-active molecule, fluoranil. The fluoranil molecule can reduce the electron concentration of monolayer MoS2, resulting in enhancement of the PL intensity.4 Furthermore, we found that the solvent used for the fluoranil treatment is critical to obtain bright monolayer MoS2. Solvent molecules would screen the charges on fluoranil molecules, as a result, which stabilizes the electron transfer-interaction between fluoranil and MoS2. Keywords: Superacid, redox-active molecules, Transition metal dichalcogenides, Photoluminescence, Transistors

Exceptional Surface Passivation Arising from Bis(trifluoromethanesulfonyl)-Based Solutions

The surface properties of many inorganic electronic materials (e.g., MoS2, WSe2, Si) can be substantially modified by treatment with the superacid bis(trifluoromethane)sulfonimide (TFSI). Here we find more generally that solutions based on molecules with trifluoromethanesulfonyl groups, including TFSI, give rise to excellent room temperature surface passivation, with the common factor being the presence of CF3SO2 groups and not the solution’s acidity. The mechanism of passivation comprises two effects: (i) chemical passivation; and (ii) field effect passivation from a negatively charged thin film likely to be physically adsorbed by the surface. Degradation of surface passivation is caused by de-adsorption of the thin film from the surface, and occurs slowly in air and rapidly upon vacuum exposure. The air stability of the passivation is enhanced by the presence of droplets at the surface which act to protect the properties of the film. The finding that nonacidic solutions can provide excellent electrical passivation at room temperature opens up the possibility of using them on materials more sensitive to an acidic environment.

Semi‐Liquid‐Metal‐(Ni‐EGaIn)‐Based Ultraconformable Electronic Tattoo

AbstractBecause of its seamless skin interface, electronic skin has attracted increasing attention in the field of biomedical sensors and medical devices. Most electronic skins are based on organic or inorganic electronic materials. However, the low flexibility of inorganic materials and the limited conductivity of organic materials restricts their widespread use. A new approach is reported to fabricate electronic tattoos from Ni‐EGaIn, which has high conductivity (1.61 × 106 S m−1) and human‐skin compliance. This time‐effective and low‐cost method is mainly based on the adhesion selectivity of semi‐liquid metal (Ni‐EGaIn) on skin and polymethacrylate glue. Light‐emitting diode arrays, temperature sensors, heaters, and surface electrodes are successfully printed onto skin, and their function in monitoring, diagnosis, and medical treatment is demonstrated. Moreover, a human–machine interface is fabricated using this technique to fully bridge the gap between a human and an electronic circuit. This novel strategy not only provides an ultraconformable interface for use in biomedicine but also represents a path towards personal customization of electronic devices.

Passivation of semipolar (10-1-1) GaN with different organic adsorbates

Expanding the functionality of electronic materials is often reliant on the attachment of organic molecules to the surface. In this study, several methods for passivating the surface of semipolar (10-1-1) GaN with different chemistries were examined; this included simple physisorption, in-situ functionalization using phosphonic acids, and a two-step carboxylic acid attachment with a peroxide pretreatment. The binding of a variety of different organic adsorbates on semipolar substrates was quantified using X-ray photoelectron spectroscopy (XPS). Our results confirm binding at the organic-inorganic interface through the presence of amine/amide species on the surface. The wide variety of organic molecules, and their binding to inorganic electronic materials, can be exploited to impart specific functionalities in technologies spanning fields of energy, biomedical science, and chemical sensing.

Recent advances on mechanics of transfer printing for flexible and stretchable electronics

Flexible and stretchable inorganic electronics, offering the high performance of conventional electronics with the ability to be deformed like a rubber, integrate inorganic electronic materials with flexible substrates and has enabled many novel applications ranging from curvilinear electronics, epidermal electronics to bio-integrated electronics. However, inorganic electronic materials (e.g., silicon) cannot be fabricated directly on a flexible substrate due to the extreme processing conditions (e.g., high temperature). To overcome this challenge, transfer printing techniques have been developed to pick up inorganic thin films from the grown substrate and transfer them onto the receiver substrate for the heterogeneous integration. This approach separates the fabrication substrate with the application substrate and provides a most promising solution for the integration of inorganic electronic materials with flexible substrates to develop flexible and stretchable electronics. This paper provides a brief review of recent advances on mechanics of transfer printing techniques for flexible and stretchable inorganic electronics including kinetically controlled transfer printing technique, shear-enhanced transfer printing technique, gecko inspired transfer printing technique, surface-relief-assisted transfer printing technique, laser-driven transfer printing technique, bending curvature controlled transfer printing technique and tape transfer printing technique. The basic concepts for each transfer printing technique are overviewed to illustrate the key roles of mechanics in the development of transfer printing techniques. Despite the successful developments of various transfer printing techniques, several challenges still exist for future transfer printing techniques with the capabilities of transfer printing of nano-devices and direct three-dimensional transfer printing in a large-scale and high-efficiency manner.

Low-cost, \u03bcm-thick, tape-free electronic tattoo sensors with minimized motion and sweat artifacts

Electronic tattoos (e-tattoos), also known as epidermal electronics, are ultra-thin and ultra-soft noninvasive but skin-conformable devices with capabilities including physiological sensing and transdermal stimulation and therapeutics. The fabrication of e-tattoos out of conventional inorganic electronic materials used to be tedious and expensive. Recently developed cut-and-paste method has significantly simplified the process and lowered the cost. However, existing cut-and-paste method entails a medical tape on which the electronic tattoo sensors should be pasted, which increases tattoo thickness and degrades its breathability. To address this problem, here we report a slightly modified cut-and-paste method to fabricate low-cost, open-mesh e-tattoos with a total thickness of just 1.5 μm. E-tattoos of such thinness can be directly pasted on human skin and conforms to natural skin texture. We demonstrate that this ultra-thin, tape-free e-tattoo can confidently measure electrocardiogram (ECG), skin temperature, and skin hydration. Heart rate and even respiratory rate can be extracted from the ECG signals. A special advantage of such ultra-thin e-tattoo is that it is capable of high-fidelity sensing with minimized motion artifacts under various body movements. Effects of perspiration are found to be insignificant due to the breathability of such e-tattoos.

Printing of microstructure strain sensor for structural health monitoring

Recent advances in microelectronics and materials should allow the development of integrated sensors with transduction properties compatible with being printed directly onto a 3D substrate, especially metallic and polymer substrates. Inorganic and organic electronic materials in microstructured and nanostructured forms, intimately integrated in ink, offer particularly attractive characteristics, with realistic pathways to sophisticated embodiments. Here, we report on these strategies and demonstrate the potential of 3D-printed microelectronics based on a structural health monitoring (SHM) application for the precision weapon systems. We show that our printed sensors can be employed in non-invasive, high-fidelity and continuous strain monitoring of handguns, making it possible to implement printed sensors on a 3D substrate in either SHM or remote diagnostics. We propose routes to commercialization and novel device opportunities and highlight the remaining challenges for research. © 2017, Springer-Verlag Berlin Heidelberg.

Ethylenediamine Grafting on Oxide-Free H-, 1/3 ML F-, and Cl-Terminated Si(111) Surfaces

Amine termination of surfaces constitutes a core platform for fields as diverse as microelectronics and bioengineering, and for nanotechnology in general. Diamines are particularly attractive for surface amination because unlike ammonia or simple amine molecules, they have a metal chelating capability useful in fabricating heterostructures. They can act as a linker molecule between inorganic electronic materials and biomolecules or photoactive quantum dots for applications in microelectronic, photonics, and biosensing. In contrast to ammonia modification of silicon surfaces, the direct grafting of diamine on silicon surfaces has been less explored. In this work, the attachment of liquid and vapor-phase ethylenediamine (EDA) on three types of oxide-free (H-, 1/3 ML F-, and Cl-terminated) Si(111) surfaces is therefore examined by infrared absorption spectroscopy and X-ray photoelectron spectroscopy in conjunction with first-principle calculations. We find that EDA chemisorption is only possible on 1/3 ML F-...

Inorganic Materials and Assembly Techniques for Flexible and Stretchable Electronics

In recent years, important progress has been made in developing design strategies, materials, and associated assembly techniques that provide empowering approaches to electronics with unconventional formats, ones that allow useful but previously hard to realize attributes of function. Notable examples of the progress made include: light weight, large area, high performance electronics, optics, and photonics; electronic and optical systems with curvilinear shapes and capacities for accommodating demanding forms of mechanical flexure; new device form factors for use in sensing and imaging; the integration of high performance electronics in 3-D with demanding nanometer design rules; functional bioresponsive electronics; and advanced hybrid materials systems for lighting, energy storage, and photovoltaic energy conversion. In this report we highlight advances that are enabling such promising capabilities in technology—specifically, the fabrication of device elements using high performance inorganic electronic materials joined with printing and transfer methods to effect their integration within functional modules. We emphasize in this review considerations of the design strategies and assembly techniques that, when taken together, circumvent limitations imposed by approaches that integrate circuit elements within compact, rigid, and essentially planar form factor devices, and provide a transformational set of capabilities for high performance flexible/stretchable electronics.

Stretchability and compliance of freestanding serpentine-shaped ribbons

High-performance stretchable electronics have to utilize high-quality inorganic electronic materials such as silicon, oxide or nitride dielectrics, and metals. These inorganic materials usually crack or yield at very small intrinsic strains, for example, 1%, whereas bio-integrated electronics are expected to at least match the stretchability of bio-tissues (20%) and deployable structure health monitoring networks are expected to expand from wafer scale (several centimeters) to cover macroscopic structures (several meters). To minimize strains in inorganic materials under large deformation, metallic and ceramic films can be patterned into serpentine-shaped ribbons. When the ribbon is stretched, some sections of the ribbon can rotate and/or buckle to accommodate the applied displacement, leaving much smaller intrinsic strain in the materials compared to the applied strain. The choice of the shape of the serpentine depends on systematic studies of the geometric variables. This paper investigates the effect of serpentine shapes on their stretchability and compliance through theoretical, numerical, and experimental means. Our closed-form curved beam solutions, FEM results, and experimental measurements have found good agreement with one another. Our results conclude that in general, the narrower ribbon, the larger arc radius and arc angle, and the longer arm length will yield lower intrinsic strain and effective stiffness. When the arm length approaches infinite, the stretchability can be enhanced by several orders. A few unexpected behaviors are found at arc angles that are close to straight bars. With additional practical constraints such as minimum ribbon width and finite overall breadth, the optimal serpentine shape can be accurately determined using our closed-form analytical solution.

Fluorescence spectroscopy characterization of cadmium sulfide quantum dots on metal, insulator, and semiconductor substrates

Colliodal cadmium sulfide quantum dots (Q-CdS), ranging in size from 1 to 5 nm and capped with dioctyl sulfosuccinate (AOT), were synthesized and deposited upon substrates of gold (Au), mica, and gallium arsenide (GaAs). Fluorescence spectroscopy is used to identify the range and maxima of excitation and emission spectra of each structure. A red shift in emission spectra from the Au to mica to GaAs substrate based samples is observed for the smallest-sized quantum dots. The midrange and largest-sized dots display the longest emission wavelengths when physisorbed to the Au substrates with a shift to shorter and then longer emission wavelengths for the mica and GaAs-based samples, respectively. The display of emission spectra throughout the visible range for the Q-CdS deposited on all three types of substrates bodes well for future optical device applications using hybrid (organic–inorganic) electronic materials. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1018–1021, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25904

Interfacial slippage of inorganic electronic materials on plastic substrates

The stretchable and flexible electronics with the structure of inorganic films on plastic substrate has recently attracted an increasing interest. Interfacial failure inevitably occurs when the structure is subject to repeated bending or stretching in application. An analysis is presented in this letter on the slipping failure mechanism for the interface between inorganic film and plastic substrate. The critical radius of system curvature for the slipping crack propagation on its interface is obtained to analyze the bendability of the structure, which can provide the design guideline and characterization method to determine the interface fracture toughness of slipping failure.

Modification of Electronic Properties of Graphene with Self-Assembled Monolayers

Integration of organic and inorganic electronic materials is one of the emerging approaches to achieve novel material functionalities. Here, we demonstrate a stable self-assembled monolayer of an alkylsilane grown at the surface of graphite and graphene. Detailed characterization of the system using scanning probe microscopy, X-ray photoelectron spectroscopy, and transport measurements reveals the monolayer structure and its effect on the electronic properties of graphene. The monolayer induces a strong surface doping with a high density of mobile holes (n > 10(13) cm(-2)). The ability to tune electronic properties of graphene via stable molecular self-assembly, including selective doping of steps, edges, and other defects, may have important implications in future graphene electronics.

Stretchable, Curvilinear Electronics Based on Inorganic Materials

All commercial forms of electronic/optoelectronic technologies use planar, rigid substrates. Device possibilities that exploit bio-inspired designs or require intimate integration with the human body demand curvilinear shapes and/or elastic responses to large strain deformations. This article reviews progress in research designed to accomplish these outcomes with established, high-performance inorganic electronic materials and modest modifications to conventional, planar processing techniques. We outline the most well developed strategies and illustrate their use in demonstrator devices that exploit unique combinations of shape, mechanical properties and electronic performance. We conclude with an outlook on the challenges and opportunities for this emerging area of materials science and engineering.

Materials and Mechanics for Stretchable Electronics

Recent advances in mechanics and materials provide routes to integrated circuits that can offer the electrical properties of conventional, rigid wafer-based technologies but with the ability to be stretched, compressed, twisted, bent, and deformed into arbitrary shapes. Inorganic and organic electronic materials in microstructured and nanostructured forms, intimately integrated with elastomeric substrates, offer particularly attractive characteristics, with realistic pathways to sophisticated embodiments. Here, we review these strategies and describe applications of them in systems ranging from electronic eyeball cameras to deformable light-emitting displays. We conclude with some perspectives on routes to commercialization, new device opportunities, and remaining challenges for research.

Mechanics of stretchable inorganic electronic materials

Electronic systems that offer elastic mechanical responses to high strain deformation are of growing interest due to their ability to enable new applications whose requirements are impossible to satisfy with conventional wafer-based technologies. This article reviews the mechanics of stretchable inorganic materials on compliant substrates. Specifically, three forms of stretchable structures are reviewed. The first one is stretchable ribbon, which provides one-dimensional stretchability. The second is stretchable nanomembranes, which can be stretched in all directions. The last is a noncoplanar mesh design, which has the advantage of providing large stretchability up to and exceeding 100%. Mechanics models and their comparison to experiment are reviewed for these three cases. Such models provide design guidelines for stretchable electronics.

Theoretical and Experimental Studies of Bending of Inorganic Electronic Materials on Plastic Substrates

AbstractThis paper describes materials and mechanics aspects of bending in systems consisting of ribbons and bars of single crystalline silicon supported by sheets of plastic. The combined experimental and theoretical results provide an understanding for the essential behaviors and for mechanisms associated with layouts that achieve maximum bendability. Examples of highly bendable silicon devices on plastic illustrate some of these concepts. Although the studies presented here focus on ribbons and bars of silicon, the same basic considerations apply to other implementations of inorganic materials on plastic substrates, ranging from amorphous or polycrystalline thin films, to collections of nanowires and nanoparticles. The contents are, as a result, relevant to the growing community of researchers interested in the use of inorganic materials in flexible electronics.