Mun Seok Jeong

• Ph. D.
• Professor (Full) at Hanyang University

Monolayer tungsten disulfide (WS2) has emerged as an active material for optoelectronic devices due to its quantum yield of photoluminescence. Despite the enormous research about physical characteristics of monolayer WS2, the defect-related Raman scattering has been rarely studied. Here, we report the correlation of topography and Raman scattering...

Local deformation is a control knob to dynamically tune the electronic band structure of 2D semiconductors. This study demonstrates the local strain‐dependent phonon properties of monolayer tungsten diselenide, which are investigated by using the scanning tunneling microscopy‐based tip‐enhanced Raman spectroscopy. The anomalous appearance and softe...

Brightening dark excitons in transition metal dichalcogenide monolayers (MLs) can provide large‐area ultrathin devices for applications in quantum information science and optoelectronics. For practical applications of dark excitons, a robust and bright emission over a wide area at room temperature is desirable; however, no reliable approach has bee...

The development of high‐performance p‐channel transistors remains a critical challenge in complementary logic circuits, despite significant advances in n‐channel transistor technologies. While amorphous oxide semiconductors have revolutionized n‐type transistors, achieving comparable performance for p‐type counterparts has proven elusive. Here, thi...

Correction for ‘Mitigating substrate effects of van der Waals semiconductors using perfluoropolyether self-assembled monolayers’ by Dae Young Park et al. , Nanoscale , 2024, 16 , 10779–10788, https://doi.org/10.1039/D4NR00061G.

Two-dimensional (2D) semiconductors have attracted significant scientific interest because of their optical properties. Their applications in optoelectronic devices can be further expanded by combining them to form heterostructures. We characterized...

This study investigates the applicability of the machine learning model in correlative spectroscopy to enhance spatial resolution for probing nanoscale structural perturbations. The developed model demonstrates significant enhancement in spatial resolution, achieving up to 50 nm through the integration of Kelvin probe force microscopy and atomic fo...

We investigated hybrid functional transparent conductive electrodes (HFTCEs) composed of indium-tin-oxide (ITO) and silver nanowires (AgNWs) for the enhancement of output efficiency in GaN-based ultraviolet light-emitting diodes (UVLEDs). The HFTCEs demonstrated an optical transmittance of 69.5% at a wavelength of 380 nm and a sheet resistance of 1...

This study investigated the applicability of the area of spheroids and hypoxic regions for efficient evaluation of drug efficacy using machine learning (ML). We initially developed a high-throughput detection method to obtain the area of spheroids and hypoxic regions that can handle over 10 000 images per hour with an error rate of 2%–3%. The ML mo...

This study investigates the applicability of six transition metal dichalcogenides to efficient therapeutic drug monitoring of ten antiepileptic drugs using laser desorption/ionization-mass spectrometry. We found that molybdenum ditelluride and tungsten ditelluride are suitable for the sensitive quantification of therapeutic drugs. The contribution...

The properties of transition metal dichalcogenides (TMDCs) are critically dependent on the dielectric constant of the substrate, which is a significant obstacle to their application. To address this issue, we...

The FA0.6MA0.4PbI3, FA0.8MA0.2PbI3 and FAPbI3 perovskite single crystals were prepared by the inverse temperature crystallization method. From the deep level transient spectroscopy (DLTS) measurement and optical conduction DLTS, the FA0.6MA0.4PbI3 and FA0.8MA0.2PbI3 samples had the majority carrier defects of E2 and E3 with Ea of 0.52 and 0.59 eV,...

Photoluminescence quantum yield (PL QY) of colloidal quantum dots (QDs) can be improved by growing a shell, but it is rather limited if the shell thickness exceeds a threshold. Lattice mismatch between the core and shell is known to determine this critical shell thickness, securing QDs from defect formation through strain release. However, it canno...

We studied the phase change and resistive switching characteristics of copper oxide (Cu x O) films through post-thermal annealing. This investigation aimed to assess the material’s potential for a variety of electrical devices, exploring its versatility in electronic applications. The Cu x O films deposited by RF magnetron sputtering were annealed...

Transition metal dichalcogenide (TMDs) heterostructure, particularly the lateral heterostructure of two different TMDs, is gaining attention as ultrathin photonic devices based on the charge transfer (CT) excitons generated at the junction. However, the characteristics of the interface of the lateral heterostructure, determining the electronic band...

Multiple‐cation perovskites have been extensively researched for stability enhancement, but limited literature exists on CsFAMA (CFM) solar cell stability under harsh temperature and humidity. This article focuses on the development of damp‐heat‐resistant CFM‐based perovskite solar cells (PSCs) through the implementation of various surface treatmen...

Recently, mixed‐cation halide perovskites have gained significant attention for developing stable, high‐performance solar cells. However, their nonlinear optical (NLO) properties are much less explored. Herein, this study reports on intriguing NLO properties observed from FA0.8MA0.2PbI3 single crystals, having an ideal bandgap of 1.52 eV for photov...

We present an integrating hemisphere-based (i.e., a variant of integrating spheres) implementation of the indirect illumination method for absolute photoluminescence quantum yield measurements, which is a recommended method in the international standard IEC 62607-3-1:2014. We rigorously formulated a mathematical model and a measurement procedure fo...

We demonstrate area-selective doping of MoS2 field-effect transistors using 1,2-dichloroethane (DCE) solution. In the device manufacturing process, area-selective chemical doping was used to implement contact engineering in the source/drain region. X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy measurements were performed to confirm...

The authors investigated the localized surface plasmon (LSP)-enhanced light output efficiency of GaN-based light-emitting diodes (LEDs) fabricated with indium-tin-oxide (ITO)/silver nanowire (AgNWs) transparent conductive electrodes (TCEs). The ITO/AgNWs TCE yielded optical transmittance of 91.7% at a wavelength of 450 nm, a sheet resistance of 16....

The application of explainable artificial intelligence in nanomaterial research has emerged in the past few years, which has facilitated the discovery of novel physical findings. However, a fundamental question arises concerning the physical insights presented by deep neural networks; the model interpretation results have not been carefully evaluat...

A new conceptual logic inverter achieved by combining MoS 2 and WSe 2 junction field-effect transistors can be applied to high-frequency electronics.

The understanding and engineering of the plasmon-exciton coupling are necessary to control the innovative optoelectronic device platform. In this study, we investigated the intertwined mechanism of each plasmon-exciton couplings in monolayer molybdenum disulfide (MoS2) and plasmonic hybrid structure. The results of absorption, simulation, electrost...

Graphene oxide is a promising 2D material for industrial applications. However, understanding its hybrid electrical properties that result from different functional groups remains a fundamentally open question: experimental characterization of the electronic configuration contains convolved information, and identifying func- tional groups by classi...

Band-edge modulation of halide perovskites as photoabsorbers plays significant roles in the application of photovoltaic and photochemical systems. Here, Lewis acidity of dopants (M) as the new descriptor of engineering the band-edge position of the perovskite is investigated in the gradiently doped perovskite along the core-to-surface (CsPbBr3-CsPb...

The understanding and engineering of the plasmon-exciton coupling are necessary to control the innovative optoelectronic device platform. In this study, we investigated the intertwined mechanism of each plasmon-exciton couplings in monolayer molybdenum disulfide (MoS 2 ) and plasmonic hybrid structure. The results of absorption, simulation, electro...

A popular substance in the MXene family, titanium carbide (Ti3C2Tx), has received substantial attention mainly due to its high metallic conductivity, easy solution processability, and environment friendliness. However, the poor oxygen resistance nature of MXene has prevented its practical applications from being realized. Despite significant attemp...

A nonplanar a-plane (11–20) and c-plane (0001) InGaN/GaN multiple quantum wells (MQWs) structures were grown an r-plane (1–102) and a c-plane (0001) sapphire (Al2O3) substrate, respectively. Using two-dimensional confocal photoluminescence spectroscopy, the spatially resolved optical characteristics of two samples are examined. We found that the in...

Nanoscale defects in two-dimensional (2D) transition metal dichalcogenides (TMDs) alter their intrinsic optical and electronic properties, and such defects require investigation. Atomic-resolution techniques such as transmission electron microscopy detect nanoscale defects accurately but are limited in terms of clarifying precise chemical and optic...

Reduced graphene oxide (rGO) is a representative commercialized graphene-related material that can be mass-produced. However, the conventional thermal and chemical reduction methods require high temperatures and toxic reducing agents and consume energy and cause environmental pollution. Therefore, alternative eco-friendly methods that are less ener...

We propose an efficient method for reducing efficiency droop in InGaN QWs by redistributing carrier localization via thermal annealing, which results in increased internal quantum efficiency (IQE) in this study. Entire structures of InGaN-based light-emitting diode (LED) were grown using metal-organic chemical vapor deposition. After thermal anneal...

In this study, we analyzed the photocurrent generation mechanism (PGM) of a heterostructure comprising n-type ReS2 and p-type two-dimensional (2D) Te. The PGM of the integrated structure was not solely driven by the photovoltaic effect, which is attributed to the built-in potential invoked by the bandgap mismatch and Fermi level difference. The PGM...

Perovskite solar cells (PSCs) have been receiving considerable attention as next-generation solar cells. However, their short lifetime is a major obstacle to their commercialization. In addition to the properties of the materials used in PSCs, their interfaces play an important role in device stability by maintaining their initial design. In this s...

Graphene is known as a super‐stiff and extremely strong material. Hence, applying strains greater than 1% to graphene and simultaneously measuring changes in its physical properties has been challenging because of the limited methodologies for measuring both high strain and other physical properties. Here, we report the Raman scattering measurement...

Despite an appropriate energy bandgap and potential to achieve unipolar p-type from initial ambipolar, the oxidative sensitivity nature of monolayer MoTe2 has hindered its further device development for practical electronic and optoelectronic applications. Here, we demonstrate a facile superacid (TFSI) doping approach to construct a highly stable u...

We report a facile and controllable method for fabricating Te nanocrystals (NCs) with tunable photoluminescence from hydrothermally grown Te thin flakes using laser irradiation. The formation of Te NCs is attributed to the vaporization of Te caused by local heat from the laser and rapid recrystallization on the substrate. Moreover, the size of the...

Optoelectronic devices based on two-dimensional (2D) van der Waals (vdWs) materials and their heterostructures are promising owing to their intriguing properties. However, the achievement of high-performance photodetectors over a wide detection range is still limited. In particular, detection in the near-infrared (NIR) region has not been attained...

Surface enhanced Raman spectroscopy (SERS) is an ultrasensitive tool for detecting a wide range of analytes. The signal amplification is generally attributed to two different mechanisms, localized surface plasmonic resonance (LSPR) and short-range charge transfer (CT) effect between the analyte molecule and the surface of the substrate. Therefore,...

Inside Front Cover In article number 2101303, Im and co-workers have demonstrated an electrically and optically controllable p-n junction memtransistor using an Al2O3 encapsulated 2D Te/ReS2 van der Waals heterostructure. The hybrid memtransistor shows a high switching ratio at a low operating voltage, high cycling endurance, and long retention tim...

The exploration of memtransistors as a combination of a memristor and a transistor has recently attracted intensive attention because it offers a promising candidate for next‐generation multilevel nonvolatile memories and synaptic devices. However, the present state‐of‐the‐art memtransistors, which are based on a single material, such as MoS2 or pe...

In this study, we fabricated and characterized uniform multi-cation perovskite FAxMA1−xPbI3 films. We used the dynamic spin-coating method to control the cation ratio of the film by gradually increasing the FA+, which replaced the MA+ in the films. When the FA+ concentration was lower than xFA ~0.415 in the films, the stability of the multi-cation...

Thermal properties, such as thermal conductivity, heat capacity, and melting temperature, influence the efficiency and stability of two-dimensional (2D) material applications. However, existing studies on thermal characteristics—except for thermal conductivity—are insufficient for 2D materials. Here, we investigated the melting temperature of 2D te...

A tunnel field-effect transistor (TFET) activated by a quantum band-to-band tunneling mechanism has encouraged the acceleration of nanodevices owing to its capability to beat the thermionic emission limit of a subthreshold swing (SS) (60 mV dec⁻¹) in conventional metal-oxide-semiconductor FETs. Despite numerous studies, fabricating a TFET based on...

2D transition metal dichalcogenides (TMDs) exhibit intriguing properties for applications in optoelectronics and electronics, among which memtransistors received extensive attention as multifunctional devices. For practical applications of 2D TMDs, large‐area fabrication of the materials via reliable processes, which is in trade‐off with their qual...

Atomically Thin Semiconductors In article number 2102893, Junsuk Rho, Kyoung-Duck Park, and co-workers develop a triple-sharp-tips nano-antenna to facilitate radiative emissions of the localized states in 2D semiconductors. The localized exciton is deterministically induced and probed at room temperature through this novel concept of tip-enhanced c...

Thermal instability of perovskite films is one of the important issues limiting the outdoor application of perovskite solar cells because perovskite films are intrinsically thermally unstable under the normal operation temperature. In this work, we explore the new role of poly (methyl methacrylate) (PMMA) that alters CH3NH3PbI3 (MAPbI3) grain bound...

In semiconductor devices, understanding and controlling the properties of metal–semiconductor and semiconductor–semiconductor junctions is vital. A wide variety of heterojunctions using transition metal dichalcogenides (TMDs) have been fabricated and characterized. Rectification of the drain-source current (Ids) has been observed from p/n-TMD junct...

The remote epitaxy of GaN p–n homojunction microcrystals (μCs) is demonstrated for fabricating transferable, flexible white light-emitting diodes (WLEDs). The GaN p–n junction μCs are randomly grown on graphene-coated Al2O3(0001), which are then delaminated for mass-transfer onto conducting copper tape. The μCs-LED shows electrical rectification an...

We investigate photoluminescence (PL) transitions of MAPbX3 (X=I, Br, and Cl) organic-inorganic hybrid perovskite single crystals under magnetic fields of up to 60 T. In these materials, sharp free-exciton transition peaks emerge at a low temperature (4.2 K). Under strong magnetic fields, the free-exciton PL transitions of three different halogens...

In atomically thin semiconductors, localized exciton (XL) coupled to light provides a new class of optical sources for potential applications in quantum communication. However, in most studies, XL photoluminescence (PL) from crystal defects has mainly been observed in cryogenic conditions because of their sub‐wavelength emission region and low quan...

Tip-enhanced nano-spectroscopy, such as tip-enhanced photoluminescence (TEPL) and tip-enhanced Raman spectroscopy (TERS), generally suffers from inconsistent signal enhancement and difficulty in polarization-resolved measurement. To address this problem, we present adaptive tip-enhanced nano-spectroscopy optimizing the nano-optical vector-field at...

For organ transplantation patients, the therapeutic drug monitoring (TDM) of immunosuppressive drugs is essential to prevent the toxicity or rejection of the organ. Currently, TDM is done by immunoassays or liquid chromatography–tandem mass spectrometry (LC–MS/MS) methods; however, these methods lack specificity or are expensive, require high level...

Photo‐excited graphene has a positive (semiconductor‐like) or negative (metal‐like) response depending on the Fermi level, which is tuned by gate control, doping, and growth. Both negative and positive photoconductive responses have a potential application as an ultrafast optical modulator in the control of light transmission. However, it is challe...

Flexible, transparent, and thermally stable gas barrier films are required to seal organic-based ultra-thin, flexible, and transparent electronic devices against moisture. Thermally stable, two-dimensional hexagonal boron nitride (hBN) is an ideal non-gas-permeable material with high transparency and flexibility. Nevertheless, the polycrystalline m...

A correction to this paper has been published: https://doi.org/10.1007/s40042-021-00156-5

The controllable transformation between the semiconductor and metal plays a key role for the electronic and optoelectronic applications of atomically thin two-dimensional (2D) layered materials. Herein, we report laser-driven synthesis of PtTe2 from Pt-deposited 2D tellurium (Te) for optimized interface of 2D Te optoelectronic device. The size and...