Consumer electronics have caused an unsustainable amount of waste electrical and electronic equipment (WEEE). Organic electronics, by means of eco-design, represent an opportunity to manufacture compostable electronic devices.

Waste electrical and electronic equipment (WEEE), or e-waste, is defined as the waste of any device that uses a power source and that has reached its end of life. Disposing of WEEE at landfill sites has been identified as an inefficient solid waste processing strategy as well as a threat to human health and the environment. In the effort to mitigate the problem, practices such as (i) designing products for durability, reparability, and safe recycling, and (ii) promoting closed-loop systems based on systematic collection and reuse/refurbishment have been identified. In this perspective, we introduce a complementary route to making electronics more sustainable: organic electronics based on biodegradable materials and devices. Biodegradable organic electronics lie at the intersection of research in chemistry, materials science, device engineering, bioelectronics, microbiology, and toxicology. The design of organic electronics for standardized biodegradability will allow composting to be an end-of-life option.

A simple model system towards an impedance-probing strain sensor based on conducting tough hydrogels is demonstrated. A poly(acrylamide) hydrogel, cross-linked with N,N’-methylene-bis(acrylamide) was contacted with carbon fibres for electrical impedance analysis. The conductivity of the salt-containing hydrogel was determined to be 114 ± 10 mS/cm. Upon stretching the hydrogel samples to their fourfold initial length, the impedance response increased according to a power law. This was used to establish a sensing equation for the relation between the resistive component of the impedance signal and the applied mechanical strain under tension. This work contributes to the development of highly stretchable and soft strain sensors for applications in soft robotics.

The emerging breakthroughs in space exploration, smart textiles, and novel automobile designs have increased technological demand for high temperature electronics. In this snapshot review we first discuss the fundamental challenges in achieving electronic operation at elevated temperatures, briefly review current efforts in finding materials that can sustain extreme heat, and then highlight the emergence of organic semiconductors as a new class of materials with potential for high temperature electronics applications. Through an overview of the state-of-the art materials designs and processing methods, we will layout molecular design principles and fabrication strategies towards achieving thermally stable operation in organic electronics.

Betavoltaics (BV) cells (or nuclear batteries) have long-lasting power and high volumetric energy densities that open a broad range of applications that are not currently available, especially in low-power electronics for the internet-of-things, internal medical devices, and harsh environments. The introduction of very low-power electronics has opened up a market for the wide and accepted use of BV cells. As BVs have potentially decades-long useful lifetimes and are anticipated to be used in harsh environments, a method to describe accelerated contact aging has been developed. Monte Carlo radiation simulations show that energy can be deposited in the interface 10-50 times faster than real-world applications. The models can be used to design contact aging experiments for BV cell deployments.

Flexible and stretchable capacitive pressure sensors have been developed in recent years due to their potential applications in health monitoring, robot skins, body activity measurements and so on. In order to enhance sensor sensitivity, researchers have changed structure of the dielectric of parallel plate capacitive sensor . Here we enhance the sensor sensitivities by changing electrode composition and explore the use of a woven electrode structure sensor with silver coated nylon yarn and EcoflexTM. The woven structure enhanced sensitivity 2.3 times relative to a simple cross-grid geometry (sensitivity was 0.003 kPa-1). Furthermore, it is also observed that the sensor with the woven electrode also had better repeatability and showed less creep than a device using carbon black electrodes. The woven structure of the electrodes enabled the device to be compliant, despite the presence of the stiff nylon fibres – thereby enabling good sensitivity without the creep seen in softer electrodes.

Polymeric conjugated materials are very promising for developing future soft material-based semiconductors, conductors, electronic and optoelectronic devices due to their inherent advantages such as lightweight, flexible shape, low-cost, ease of processability, ease of scalability, etc. There are a number of ways to tune material properties via post-processing treatments such as annealing, solvent additives, or doping. One challenge of solution processed organic thin film electronics is the repeatable and well-defined morphological control of the resulting films after deposition. In this study, we observed how the addition of diiodo-alkanes to poly-3-hexyl-thiophene (P3HT) solutions effect the formation of resulting thin films. These additives have various boiling points that will affect the drying properties of cast thin films. We also sought to observe if any halogen bonding interaction between iodine and sulfur occurs and if this interaction can be used to promote polymer morphological self-assembly. Techniques such as UV/Vis spectroscopy, X-ray diffraction, and Atomic Force Microscopy were used to probe the evolution of the film morphology as the additives were added to the solutions. 1,8-diiodooctane doped films showed the best overall device performance. This could be due to its favorable interaction with the side chain of P3HT as seen in it morphological properties. This study may result in a new technique that can be used to enhance the solid-state morphology of thin films for high performance electronic applications.

Formulated, processed, and dried Aloe polysaccharides thin film sandwiched between ITO as bottom electrode and Au as top electrode has been adopted as an artificial synapse to emulate behavior of neuromorphic computing. The synaptic plasticity or weight has been modulated with this simple metal-insulator-metal structure by applying voltage sweep and voltage pulse, with excitatory postsynaptic current being monitored. Synaptic potentiation and depression has been demonstrated by applying 6 consecutive sweeps of voltage in positive and negative polarity, respectively. By varying number (10 – 50) of voltage pulses, variable synaptic weight has been measured with paired pulse facilitation and post-tetanic potentiation indexes of 2.61x10-6and 1.45x10-4, respectively. The short-term plasticity and long-term potentiation can be clearly revealed when applying 40 pulses and beyond, with extracted time constants of approximately 28 s at 40 pulses and 90 s at 50 pulses.

In the search for chemically stable two-dimensional (2D) materials with high in-plane mobility, proper bandgap, and compatibility with vapor-based fabrication, van der Waals semiconductor SiP has become a potential candidate as a robust variation of black phosphorous. While bulk SiP crystals were synthesized in the 1970s, the vapor-based synthesis of SiP nanostructures or thin films is still absent. We here report the first chemical vapor growth of SiP nanostructures on SiO2/Si substrate. SiP islands with lateral size up to 20 μm and showing well-defined Raman signals were grown on SiO2/Si substrate or on SiP-containing concentric rings. The presence of SiP phase is confirmed by XRD. The formation of rings and islands is explained by a multiple coffee ring growth model where a dynamic fluctuation of droplet growth front induces the topography of concentric ring surfaces. This new growth method might shed light on the controlled growth of group IV-III high-mobility 2D semiconductors.

Nickel-rich layered oxide LiNi0.8Co0.1Mn0.1O2 suffers from severe structural instability and irreversible capacity loss during cycling due to cation disorder of Li+ and Ni2+. To solve this problem, the precursor Ni0.8Co0.1Mn0.1(OH)2 and well-ordered LiNi0.8Co0.1Mn0.1O2 cathode materials were successfully synthesized via controlled crystallization and high-temperature solid-state methods. The structure, morphology, and electrochemical performance of the precursor and LiNi0.8Co0.1Mn0.1O2 powders were investigated. The results show that the precursor Ni0.8Co0.1Mn0.1(OH)2 is made of sphere-like particles composed of needle-like primary crystal and LiNi0.8Co0.1Mn0.1O2 possesses a perfect layered structure with low Li/Ni disorder. Electrochemical data demonstrate that the material rate capabilities are 203.3, 187.7, 170.4, and 163 mA h/g from 0.1C to 10C, respectively. The capacity retention is 87.9% after 100 cycles at 1C, even the cut-off voltage was increased to 4.5 V. The high discharge capacity and outstanding cycling life can be attributed to the merits of a perfect crystal lattice with low Li/Ni disorder, fast lithium ion transport, and relatively low charge transfer resistance.

Capacitors represent the largest obstacle to dynamic random-access memory (DRAM) technology evolution because the capacitor properties govern the overall operational characteristics of DRAM devices. Moreover, only the atomic layer deposition (ALD) technique is used for the dielectric and electrode because of its extreme geometry. Various high-k materials deposited by ALD have been investigated for further scaling. Whereas past investigations focused on increasing the physical thickness of the dielectric to suppress leakage current, the physical thickness of the dielectric should also be limited to a few nanometers in design rules less than 1×-nm. Therefore, a new way to overcome the limitations of traditional approaches based on thorough understanding of high-k materials is highly recommended to enhance the properties of conventional materials and provide directions for developing new materials. In this review, previously reported results are discussed, and suggestions are made for further investigations for DRAM capacitor applications.

The effect of length scale on mechanical strength is a significant consideration for semiconductor materials. In III-V semiconductors, such as InSb, a transition from partial to perfect dislocations occurs at the brittle-to-ductile transition temperature (~150 °C for InSb). High temperature micro-compression reveals InSb to show a small size effect below the transition, similar to ceramics, while in the ductile regime it shows a size effect consistent with fcc metals. The source truncation model is found to agree with the observed trends in strength with size once the change in Burgers vector and bulk strength are taken into account.

The rapidly growing demand for data storage and processing, driven by artificial intelligence (AI) and other data-intensive applications, is posing a serious challenge for current computing devices based on the von Neumann architecture. For every calculation, data sets need to be shuffled sequentially between the processor, and multiple memory and storage units through bandwidth-limited and energy-inefficient interconnects, typically causing 40% power wastage. Phase-change materials (PCMs) show great promise to break this bottleneck by enabling nonvolatile memory devices that can optimize the complex memory hierarchy, and neuro-inspired computing devices that can unify computing with storage in memory cells. The articles in this issue of MRS Bulletin highlight recent breakthroughs in the fundamental materials science, as well as electronic and photonic implementations of these novel devices based on PCMs.

In this work, hierarchical mesoporous Zn–Ni–Co–S–rGO/NF microspheres have been prepared by hydrothermal, sulfurization, and subsequent calcination process. The effect of different sulfurization time on the morphology and capacitance of composites was tested. The high electrochemical performance of (Zn–Ni–Co–S–rGO/NF) composite was obtained when the sulfurization time was 3 h (Zn–Ni–Co–S–rGO/NF-3h), where a specific capacitance of 627.7 F/g at 0.25 A/g and excellent rate capability of about 97.8% capacitance retention at 2 A/g after 4000 cycles were achieved. Moreover, an asymmetric supercapacitor fabricated by (Zn–Ni–Co–S–rGO/NF-3h) composite and activated carbon (AC) as the positive and the negative electrodes, respectively, showed a high energy density of 75.96 W h/kg at a power density of 362.49 W/kg with a remarkable cycle stability performance of 91.2% capacitance retention over 5000 cycles. This incredible electrochemical behavior illustrates that the hierarchical mesoporous Zn–Ni–Co–S–rGO/N-3h microsphere electrodes are promising electrode materials for application in high-performance supercapacitors.

Size control of copper fine particles is highly important for their application for conductive materials. In this study, easy size tuning of the copper fine particles coated by n-hexylamine was achieved via controlling the ratio of n-hexylamine and the precursor CuO. The obtained particles were stable and had a hydrophobic surface. TG-DTA measurement revealed the formation of thin layer of n-hexylamine on the particles.

This manuscript describes low-voltage epoxy-carbon nanotube composites with highly nonlinear resistances. Carbon nanotube paste was deposited on interdigitated electrodes and I-V characteristics were obtained over different voltage ranges and at different sweep speeds. In most cases, the injection process into the electrode-composite interface region was dominant, with exponential voltage dependence of the current.

Chemical doping of organic semiconductors is a common technique used to increase the performance numerous organic electronic and optoelectronic devices. Tetrafluoro-tetracyanoquinodimethane (F4-TCNQ) is one of the most widely known p-dopants having the properties necessary to act as a strong electron acceptor. Despite its strong electron accepting abilities, F4-TCNQ is extremely expensive, making it less than ideal for large-area applications. Here, we introduce a small molecule called Tetracyanoindane (TCI) as a potential p-dopant. Widely known for its role in the field of non-linear optics, its high polarizability arises from the addition of four cyano-groups, which are electron withdrawing groups. The four cyano-groups are also seen in the F4-TCNQ molecule and contributes to the withdrawing strength alongside the four fluorine atoms present. We hypothesize that TCI could have similar accepting strength to F4-TCNQ and could potentially replace it as a cheaper alternative. In this study, Cyclic Voltammetry (CV), UV-Visible-Near Infrared Spectroscopy (UV/Vis/NIR), Photoluminescence (PL), Current-Voltage (IV) measurements analysis was conducted to compare the accepting strength of TCI and F4-TCNQ. Then, the two molecules were added to Poly-3-hexy-thiophene (P3HT) to observe how readily they dope the organic semiconductor.

The electrical reliability of multilayer high density interconnection printed circuit boards (HDI-PCBs) is mainly affected by the thermo-mechanical stability of stacked micro via interconnections. Here, a critical failure mode is the stress related crack between the electrolytically filled via and the target pad, commonly known as target pad separation. The junction includes two Cu-Cu-interfaces, one between the target Cu pad and the thin electroless Cu layer and the second between electroless Cu and electrolytic Cu. In this paper we will show that state-of-the-art electroless Cu plating processes are able to provide solid, completely recrystallized and highly reliable stacked via junctions. Defect free interfaces were achieved by using ionic Pd-activators and electroless Cu baths with a cyanide based stabilizer system. Cyanide free electroless Cu baths tend more to the formation of nanometer sized defects, discovered via Transmission Electron Microscopy (TEM). In this case a precise adjustment of single stabilizer components is mandatory to achieve defect free layers. The defects are hollow and were identified as “nano voids”. A critical density of these nano voids weakens the interface, predefines the crack path and reduces the overall reliability of the junction. A precise localization of the nano voids within the junction was enabled by detecting the Ni-containing electroless Cu layer via TEM-Ni mapping. Slower volume exchange of the electroless Cu solution within the blind micro via (BMV) substantially increases the nano void density. The ability of nano voids to migrate and coalesce at elevated temperatures was investigated as well.

The replacement of the strained Si channel in metal-oxide-semiconductor-field-effect-transistors (MOSFETs) with high electron mobility III-V compound semiconductors, particularly InGaAs, is being intensively investigated as an alternative to improve the drive current at low supply voltages in sub-10 nm CMOS applications. As device scaling continues, the reduction of the source and drain contact resistance becomes one of the most difficult challenges to fabricate highly scaled III-V-MOSFETs. In this article, we describe a self-aligned process based on selective molecular beam epitaxial regrowth of InxGa1-xAs (x=0-1) raised source/drain nanowire structures on etched recessed areas of a nanopatterned HfO2 template as a key element to integrate high mobility III-V materials with high-κ dielectrics in three-dimensional device architectures. The interaction of atomic H with the surface of the HfO2 nanopatterns has been investigated by using AFM, ToF-SIMS, and ARXPS. Selective growth has been observed for all values of x between 0 and 1. AFM results show that atomic H lowers the temperature process window for InxGa1-xAs selective growth. HRTEM images have revealed the conformality of the growth and the absence of nanotrench formation near the HfO2 mask edges. InxGa1-xAs alloys grown on H-treated HfO2 patterned substrates exhibit a higher uniformity in chemical composition and full strain relaxation for x≥0.5.

Optimizing interfaces between photosynthetic natural photoconverters, like photosynthetic bacterial Reaction Centers (RCs) and electrode surfaces represents a challenge in the progress of bio-optoelectronic devices. The features of the surfaces may result detrimental for the tertiary and quaternary structures of the RC, even resulting in the denaturation of the enzyme. Functional surfaces possessing both confinement capability and conductive features able to preserve the conformation of the biomolecule and its bioelectronic behaviours are highly needed. In this work, the RC is adsorbed on diatomaceous silica and plasma treated hydrophobic silicon based materials. Both the materials are demonstrated to be able to preserve and enhance the RC photoconverting activity. In particular, we evaluate the functioning of isolated bacterial RC interacting with flat pSi electrode through two nanotextured interfaces designed to address the RC: a thin conductive silicon film nanotextured in pillars via plasma treatment, and a cast film of nanostructured dielectric biosilica obtained from diatomaceous earth. The characterization of these interfaces, together with the RC photocurrent production measurements, pave the way to new generation RC based bio-devices for photocurrent investigation.

Substantial increase of output current, and Ion / Ioff ratio for sub-7nm low power CMOS transistors, can be accomplished using a novel optoelectronic technology, which is 100% compatible with existing CMOS process flow. For RF or mixed signal ASICs, adding photonic components may improve the cut-off frequency, and reduce series resistance. Products that utilize power regulating devices, such as power MOSFETs, will benefit from the optoelectronic configuration to achieve much lower Rdson and high voltage at the same time. For semiconductor memories, such as DRAM or FLASH, the photonic technique may reduce the ERASE / WRITE / access time and improve the reliability.