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Yonas Tsegaye Megra

Bio: Yonas Tsegaye Megra is an academic researcher from Sungkyunkwan University. The author has contributed to research in topics: Materials science & Oxide. The author has an hindex of 3, co-authored 4 publications receiving 56 citations.

Papers
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Journal ArticleDOI
TL;DR: In this paper, the adhesion properties of two-dimensional (2D) materials such as graphene and MoSalt; subagt;2alt;/subagt, are reviewed.
Abstract: Over the past years, many researchers have been excited with the advent of two-dimensional (2D) materials such as graphene and MoSalt;subagt;2alt;/subagt; because of their intriguing physical and chemical properties. Furthermore, they have great potential in various applications including nanoelectronics, flexible or stretchable devices, energy conversion or storage devices, sensors, nanocomposites, and others. In addition to their electrical, mechanical, optical, and thermal properties, interfacial properties of 2D materials such as adhesion energy have recently attracted attention from researchers since interfacial interactions of 2D materials with others are of great importance in obtaining mechanical integrity of nanomanufacturing processes and related devices. In this respect, this paper reviews the adhesion properties of 2D materials. Measurement methods and characteristics of adhesion behaviors were summarized and discussed mainly for graphene and MoSalt;subagt;2alt;/subagt;.

32 citations

Journal ArticleDOI
07 Jan 2021-ACS Nano
TL;DR: This paper synthesizes wafer-scale MoS2-WS2 vertical heterostructures (MWVHs) using plasma-enhanced chemical vapor deposition (PE-CVD) via penetrative single-step sulfurization discovered by time-dependent analysis, and provides a fundamental understanding of the interfacial properties of TMD-TMD vertical heterOSTructures.
Abstract: Two-dimensional (2D) transition metal dichalcogenides (TMDs) have attracted considerable attention owing to their synergetic effects with other 2D materials, such as graphene and hexagonal boron nitride, in TMD-based heterostructures. Therefore, it is important to understand the physical properties of TMD-TMD vertical heterostructures for their applications in next-generation electronic devices. However, the conventional synthesis process of TMD-TMD heterostructures has some critical limitations, such as nonreproducibility and low yield. In this paper, we synthesize wafer-scale MoS2-WS2 vertical heterostructures (MWVHs) using plasma-enhanced chemical vapor deposition (PE-CVD) via penetrative single-step sulfurization discovered by time-dependent analysis. This method is available for fabricating uniform large-area vertical heterostructures (4 in.) at a low temperature (300 °C). MWVHs were characterized using various spectroscopic and microscopic techniques, which revealed their uniform nanoscale polycrystallinity and the presence of vertical layers of MoS2 and WS2. In addition, wafer-scale MWVHs diodes were fabricated and demonstrated uniform performance by current mapping. Furthermore, mode I fracture tests were performed using large double cantilever beam specimens to confirm the separation of the MWVHs from the SiO2/Si substrate. Therefore, this study proposes a synthesis mechanism for TMD-TMD heterostructures and provides a fundamental understanding of the interfacial properties of TMD-TMD vertical heterostructures.

19 citations

Journal ArticleDOI
TL;DR: In this article , a highly densified Gd0.1Ce0.9O2−δ (gadolinia doped ceria [GDC]) interlayer between the electrolyte and cathode was fabricated by introducing additional precursors into the powder suspension inks during spin coating.
Abstract: The interface between the electrolyte and cathode of solid oxide fuel cells (SOFCs) is essential for determining the electrochemical performance from the sluggish oxygen reduction reaction kinetics and thermal stability from chemical intermixing. In this study, we fabricated a highly densified Gd0.1Ce0.9O2−δ (gadolinia doped ceria [GDC]) interlayer between the electrolyte and cathode by introducing additional precursors into the powder suspension inks during spin coating. We verified that these additional precursors facilitated grain growth during the sintering process at a relatively low temperature, resulting in the densification of the GDC interlayer. A densified GDC interlayer-based anode-supported cell exhibited a maximum power density of approximately 1.11 W/cm2 at 650°C, 1.74-fold greater than that of a conventional GDC interlayer-based cell, with excellent electrochemical stability for 200 h. Our results demonstrated a simple and cost-effective process for fabricating highly densified GDC interlayers to develop SOFC with high performance and stability.

2 citations

Journal ArticleDOI
TL;DR: In this article, the interaction strength of large-area monolayer graphene transferred on SiO2/Si was adjusted by thermal treatments, and its adhesion energy was measured by mode I fracture tests using a double cantilever beam (DCB) configuration with a laminated composite.

2 citations


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Journal Article
TL;DR: This paper discusses how and why wrinkles/buckles form in various materials, and describes several examples from everyday life that demonstrate that wrinkling or buckling is indeed a commonplace phenomenon that spans a multitude of length scales.
Abstract: The English-language dictionary defines wrinkles as "small furrows, ridges, or creases on a normally smooth surface, caused by crumpling, folding, or shrinking". In this paper we review the scientific aspects of wrinkling and the related phenomenon of buckling. Specifically, we discuss how and why wrinkles/buckles form in various materials. We also describe several examples from everyday life, which demonstrate that wrinkling or buckling is indeed a commonplace phenomenon that spans a multitude of length scales. We will emphasize that wrinkling is not always a frustrating feature (e.g., wrinkles in human skin), as it can help to assemble new structures, understand important physical phenomena, and even assist in characterizing chief material properties.

670 citations

Journal Article
TL;DR: In this paper, the authors performed well-controlled experiments at macroscopic scales to study what sets the dimensions of these blisters in terms of the material properties and explain their results by using a combination of scaling and analytical methods.
Abstract: The wrinkling and delamination of stiff thin films adhered to a polymer substrate have important applications in “flexible electronics.” The resulting periodic structures, when used for circuitry, have remarkable mechanical properties because stretching or twisting of the substrate is mostly accommodated through bending of the film, which minimizes fatigue or fracture. To date, applications in this context have used substrate patterning to create an anisotropic substrate-film adhesion energy, thereby producing a controlled array of delamination “blisters.” However, even in the absence of such patterning, blisters appear spontaneously, with a characteristic size. Here, we perform well-controlled experiments at macroscopic scales to study what sets the dimensions of these blisters in terms of the material properties and explain our results by using a combination of scaling and analytical methods. Besides pointing to a method for determining the interfacial toughness, our analysis suggests a number of design guidelines for the thin films used in flexible electronic applications. Crucially, we show that, to avoid the possibility that delamination may cause fatigue damage, the thin film thickness must be greater than a critical value, which we determine.

199 citations

Journal ArticleDOI
16 Jun 2021-Joule
TL;DR: This review will provide a comprehensive review of current research on NGs’ applications in different sectors of a smart city and show how NGs can be a game changer in the development of smart cities under 5G services and how the usage of NG can boost the convenience of city dwellers.

193 citations

Journal ArticleDOI
10 Mar 2020
TL;DR: This review focuses on the applications of self-powered generators as implantable and wearable sensors in health monitoring, biosensor, human-computer interaction, and other fields.
Abstract: Wearable and implantable electronics (WIEs) are more and more important and attractive to the public, and they have had positive influences on all aspects of our lives. As a bridge between wearable electronics and their surrounding environment and users, sensors are core components of WIEs and determine the implementation of their many functions. Although the existing sensor technology has evolved to a very advanced level with the rapid progress of advanced materials and nanotechnology, most of them still need external power supply, like batteries, which could cause problems that are difficult to track, recycle, and miniaturize, as well as possible environmental pollution and health hazards. In the past decades, based upon piezoelectric, pyroelectric, and triboelectric effect, various kinds of nanogenerators (NGs) were proposed which are capable of responding to a variety of mechanical movements, such as breeze, body drive, muscle stretch, sound/ultrasound, noise, mechanical vibration, and blood flow, and they had been widely used as self-powered sensors and micro-nanoenergy and blue energy harvesters. This review focuses on the applications of self-powered generators as implantable and wearable sensors in health monitoring, biosensor, human-computer interaction, and other fields. The existing problems and future prospects are also discussed.

132 citations

Journal ArticleDOI
TL;DR: The demonstrated stretchable and robust energy‐harvesting E‐skin using LM‐NP‐based electrodes is of great significance in sustainable human–machine interactive system, intelligent robotic skin, security tactile switches, etc.

98 citations