Browsing by Subject "Flexible electronics"

Now showing 1 - 5 of 5

Open Access
Atomic layer deposition: an enabling technology for the growth of functional nanoscale semiconductors
(Institute of Physics Publishing, 2017) Bıyıklı, Necmi; Haider A.
In this paper, we present the progress in the growth of nanoscale semiconductors grown via atomic layer deposition (ALD). After the adoption by semiconductor chip industry, ALD became a widespread tool to grow functional films and conformal ultra-thin coatings for various applications. Based on self-limiting and ligand-exchange-based surface reactions, ALD enabled the low-temperature growth of nanoscale dielectric, metal, and semiconductor materials. Being able to deposit wafer-scale uniform semiconductor films at relatively low-temperatures, with sub-monolayer thickness control and ultimate conformality, makes ALD attractive for semiconductor device applications. Towards this end, precursors and low-temperature growth recipes are developed to deposit crystalline thin films for compound and elemental semiconductors. Conventional thermal ALD as well as plasma-assisted and radical-enhanced techniques have been exploited to achieve device-compatible film quality. Metal-oxides, III-nitrides, sulfides, and selenides are among the most popular semiconductor material families studied via ALD technology. Besides thin films, ALD can grow nanostructured semiconductors as well using either template-assisted growth methods or bottom-up controlled nucleation mechanisms. Among the demonstrated semiconductor nanostructures are nanoparticles, nano/quantum-dots, nanowires, nanotubes, nanofibers, nanopillars, hollow and core-shell versions of the afore-mentioned nanostructures, and 2D materials including transition metal dichalcogenides and graphene. ALD-grown nanoscale semiconductor materials find applications in a vast amount of applications including functional coatings, catalysis and photocatalysis, renewable energy conversion and storage, chemical sensing, opto-electronics, and flexible electronics. In this review, we give an overview of the current state-of-the-art in ALD-based nanoscale semiconductor research including the already demonstrated and future applications.
Embargo
Flexible printed electronics for touch and strain feedback
(2024-08) Chowdhury, Hussain Kawsar
This era of technological revolution demands more innovation in making the electronics and devices used in everyday human lives more and more personal and interactive. The colossal interest and research in the development of flexible and multi-functional sensors are a result of this demand. However, it is still a significant challenge to fabricate such flexible wearable devices using simple and cost-effective approaches that can be utilized in mass production or directly integrated into textile manufacturing without introducing additional complicated steps that require high-end laboratory-grade technology. This thesis addresses the issue regarding the need for a mass-producible process for developing wearable and flexible sensors by utilizing ancient technology like stencil printing that is fast, simple, and cost-effective. In this work, a graphene/carbon black complex-based conductive ink was developed, which utilizes the filler behavior of carbon black particles among graphene sheets to enhance the electrical performance of the ink. The polymer-assisted binding using polycarbonate enabled the ink to be easily printable with desired patterns with excellent adhesion and stability. First, a functional tattoo capable of sensing different pressure levels was developed, which works by utilizing the change in capacitance of a two-dimensional printed capacitor with the change of pressure. An interdigitated comb geometry was used to fabricate the capacitive sensor that increases the interactive area between the electrodes, resulting in enhanced performance of the two-dimensional capacitor. The capacitive touch sensor could differentiate among multiple pressure levels at different time ranges with fast and consistent performance. Furthermore, a stretchable textile-based strain sensor was developed with the ink on a cotton fabric substrate that can detect human motion and bending by measuring the change in resistance using the same stencil printing methodology. The sensor was capable of detecting different levels of bending and also was able to differentiate between fast and slow bending motion. Furthermore, the textile-based strain sensor could withstand multiple washing cycles and could exhibit similar performance trends for strain sensing.
Open Access
Nanostructured materials and devices for sensing and energy harvesting applications
(2015-08) Kanık, Mehmet
A closer look into the fundamental challenges of the modern world reveals that the increasing demand for energy threatens the evolution of science and technology. Energy-efficiency is thus a fundamental issue in engineering nano-devices. An important path to achieve high efficiency is to convert the mechanical energy into electrical energy using piezoelectric and triboelectric energy harvesting circuitries, hence enabling self-powered systems at nanoscale. The utilization of novel piezoelectric and triboelectric energy harvesting materials introduces the opportunity of manufacturing flexible, wearable and stretchable self-powered devices. In this thesis, we introduced a new fabrication technique, new strategies and practical approaches for developing high performance triboelectric and piezoelectric materials and devices for flexible electronics, artificial skin and energy harvesting applications. The first part of the thesis focuses on the development of piezoelectric nanoribbons. Poly (vinylidene fluoride) and its copolymer Poly (vinylidene fluoride)-co-tri (fluoroethylene) were used to fabricate spontaneously high piezoelectric nanoribbons. We measured the record-high piezoelectric charge coefficient from our ribbons, because the high stress and high temperature used in the fabrication can enhance their properties. In addition, proof of principle devices for energy harvesting and sensing were fabricated using nanoribbons. The achievements in this part of the thesis can be listed as: i) We obtained extraordinary high aspect ratio, globally oriented, polymer encapsulated, and high piezoelectric microribbon and nanoribbon arrays. ii) Due to process conditions (shear stress and temperature) used in thermal fiber drawing, as-produced micro and nanoribbons contain high amount of polar phase without requiring any electrical poling. iii) We developed a new technique for characterizing and analyzing multiferroic characteristics of nano-objects, which consist of parallel evaluation of instrumental, numerical and analytical data. iv) To our knowledge, we achieved the highest piezoelectric charge coefficient from our ribbons in the literature. v) We enhanced stability of the piezoelectric ribbons by increasing the Curie temperature above its melting point due to processing conditions. vi) We observed and explained a new phase transformation mechanism in polymer piezoelectric ribbons. vii) The state-of-the-art ab initio calculations, which explain the phase transformation mechanism of molecules during the fiber drawing with the effect of shear, tensile forces and temperature, were included in detail. The second part is about developing high energy output triboelectric generators. A high performance multi-layered triboelectric generator was developed using chalcogenide nanostructures. This part of the thesis details the following achievements: i) We demonstrated that not only polymer, but also semiconductor chalcogenide materials can be used in triboelectric applications, for the first time. ii) For the first time, we proposed and demonstrated that the fluorination of nanostructured surfaces increases triboelectric performance significantly. iii) We introduced a multi-layered triboelectric generator which is very promising for real applications such as acoustic wave and vibration detection, and energy harvesting with very high power output (0.51 Watt) in comparison with the literature. iv) We used a 3D printing technique to produce our device, which is low-cost and appropriate for rapid prototyping and mass production. v) We explained the device theory for the triboelectric nanogenerator, which aligned well with our experimental results.
Open Access
Synthesis of graphene on ultra-smooth copper foils for large area flexible electronics
(IEEE, 2015) Polat, E. O.; Balcı, Osman; Kakenov, Nurbek; Kocabaş, Coşkun; Dahiya, R.
This work demonstrates the synthesis of high quality, single layer graphene on commercially available ultra-smooth copper foils. The presented method will result in improved scalability of graphene based electronic and optical devices. Our approach is compatible with roll-to-roll printing as well as transfer printing of graphene layers on to a broad range of substrates including flexible and ultra-thin polymers. We propose that using commercially available ultra-smooth coppers provides scalable approach with the reduced variation of transport properties sourced from local graphene quality.
Open Access
Trends in molecular design strategies for ambient stable n-channel organic field effect transistors
(Royal Society of Chemistry, 2017) Dhar, J.; Salzner, U.; Patil, S.
In recent years, organic semiconducting materials have enabled technological innovation in the field of flexible electronics. Substantial optimization and development of new π-conjugated materials has resulted in the demonstration of several practical devices, particularly in displays and photoreceptors. However, applications of organic semiconductors in bipolar junction devices, e.g. rectifiers and inverters, are limited due to an imbalance in charge transport. The performance of p-channel organic semiconducting materials exceeds that of electron transport. In addition, electron transport in π-conjugated materials exhibits poorer atmospheric stability and dispersive transient photocurrents due to extrinsic carrier trapping. Thus development of air stable n-channel conjugated materials is required. New classes of materials with delocalized n-doped states are under development, aiming at improvement of the electron transport properties of organic semiconductors. In this review, we highlight the basic tenets related to the stability of n-channel organic semiconductors, primarily focusing on the thermodynamic stability of anions and summarizing the recent progress in the development of air stable electron transporting organic semiconductors. Molecular design strategies are analysed with theoretical investigations.