Sangyeon Pak

van der Waals heterostructures composed of two different monolayer crystals have recently attracted attention as a powerful and versatile platform for studying fundamental physics, as well as having great potential in future functional devices because of the diversity in the band alignments and the unique interlayer coupling that occurs at the heterojunction interface. However, despite these attractive features, a fundamental understanding of the underlying physics accounting for the effect of i

Abstract Flexible electronics and optoelectronics based on monolayered, semiconducting transition metal dichalcogenides (TMDCs) channel have recently received attention as the 2D structure possess superior mechanical, optical, and electrical properties. However, there is a lack of understanding of strain‐dependent electrical and photoelectrical properties in the electrode‐TMDC channel system. Here, two‐terminal flexible device is fabricated and strain‐engineered contact barrier modulation betwee

Phototransistors that are based on a hybrid vertical heterojunction structure of two-dimensional (2D)/quantum dots (QDs) have recently attracted attention as a promising device architecture for enhancing the quantum efficiency of photodetectors. However, to optimize the device structure to allow for more efficient charge separation and transfer to the electrodes, a better understanding of the photophysical mechanisms that take place in these architectures is required. Here, we employ a novel con

Monolayered, semiconducting molybdenum disulfide (MoS2) is of considerable interest for its potential applications in next-generation flexible, wearable, and transparent photodetectors because it has outstanding physical properties coupled with unique atomically thin dimensions. However, there is still a lack of understanding in terms of the underlying mechanisms responsible for the photoresponse dynamics, which makes it difficult to identify the appropriate device design strategy for achieving

Electronic devices based on two-dimensional (2D) MoS₂ show great promise as future building blocks in electronic circuits due to their outstanding electrical, optical, and mechanical properties. Despite the high importance of doping of these 2D materials for designing field-effect transistors (FETs) and logic circuits, a simple and controllable doping methodology still needs to be developed in order to tailor their device properties. Here, we found a simple and effective chemical dopi

Electronic devices composed of semiconducting two-dimensional (2D) materials and ultrathin 2D metallic electrode materials, accompanying synergistic interactions and extraordinary properties, are becoming highly promising for future flexible and transparent electronic and optoelectronic device applications. Unlike devices with bulk metal electrode and 2D channel materials, devices with ultrathin 2D electrode and 2D channel are susceptible to chemical reactions in both channel and electrode surfa

Engineering energy levels of MoS 2 monolayers via halide atom doping can greatly contribute to the charge kinetics and the catalytic activities.

Chemical vapor deposition (CVD) synthesis for two-dimensional (2D) transition-metal dichalcogenides (TMDCs) is fundamentally important for realizing high-quality single crystals of TMDCs for future electronic and optoelectronic device applications. However, CVD synthesis of TMDCs generally requires a high synthetic temperature (>700 °C), which limits the choice of growth substrates and their broad applications. In this work, we present direct CVD synthesis of 2D MoS2 on glass. The CVD growth tem

Doping of monolayered MoS2 catalysts has drawn attention as the promising strategy that can improve the catalytic performance in hydrogen evolution reaction (HER) through enhancing charge transport properties in MoS2 catalysts. However, relatively little attention has been paid to identifying other parameters that affect the catalytic performance when the surface chemistry is altered. Here, we demonstrated that the doping strategies significantly affect not only the energy level of semiconductin

Monolayered transition metal dichalcogenides (TMDCs) possess a highly sensitive nature to external elements, particularly adsorbed molecules on the surface such as H2O or O2 molecules, due to their atomically thin structure. In this sense, it is important to develop a strategy to obtain a pristine surface of 2D TMDCs for the successful and reliable fabrication of a device with their originally intended functions. Here, we suggest a facile strategy of surface treatment to effectively eliminate th

Innovative laser etching techniques precisely modulate the density of active sites on the basal plane of bilayer MoS 2 and thereby significantly enhance its hydrogen evolution reaction.

Despite the importance of the stability of the 2D catalysts in harsh electrolyte solutions, most studies have focused on improving the catalytic performance of molybdenum disulfide (MoS₂) catalysts rather than the sustainability of hydrogen evolution. In previous studies, the vulnerability of MoS₂ crystals is reported that the moisture and oxygen molecules can cause the oxidation of MoS₂ crystals, accelerating the degradation of crystal structure. Therefore, opti

Abstract The increasing demand for miniature, flexible electronic devices have fueled the need for compact and high‐performing energy storage solutions. Microsupercapacitors (mSCs) with reduced dimension and novel electrode design have gained prominence. This concept paper summarizes and views the recent advancements in mSCs with a focus on 3D graphene electrodes and their novel electrode design to increase energy performance of the devices. Especially, we focus on these 3D graphene structures f