scispace - formally typeset
Search or ask a question
Author

Jong Hyun Ahn

Bio: Jong Hyun Ahn is an academic researcher from Yonsei University. The author has contributed to research in topics: Graphene & Graphene nanoribbons. The author has an hindex of 74, co-authored 287 publications receiving 39786 citations. Previous affiliations of Jong Hyun Ahn include National University of Singapore & University of Illinois at Urbana–Champaign.


Papers
More filters
Journal ArticleDOI
Xiang Chen1, Yong Ju Park1, Tanmoy Das1, Houk Jang1, Jae Bok Lee1, Jong Hyun Ahn1 
TL;DR: This study reveals a novel method to fabricate and use patterned MoS2 and graphene-MoS2 heterojunctions, which could be generalized to the rational design of other 2D materials, heterojunction and devices in the future.
Abstract: Application-oriented patterned growth of transition metal dichalcogenides (TMDCs) and their heterojunctions is of critical importance for sophisticated, customized two-dimensional (2D) electronic and optoelectronic devices; however, it is still difficult to fabricate these patterns in a simple, clean, and high controllability manner without using optical lithography. Here, we report the direct synthesis of patterned MoS2 and graphene–MoS2 heterojunctions via selective plasma treatment of a SiO2/Si substrate and chemical vapor deposition of MoS2. This method has multiple merits, such as simple steps, a short operating time, easily isolated MoS2 layers with clean surfaces and controllable locations, shapes, sizes and thicknesses, which enable their integration into the device structure without using a photoresist. In addition, we demonstrate the direct growth of patterned graphene–MoS2 heterojunctions for the fabrication of transistor. This study reveals a novel method to fabricate and use patterned MoS2 and graphene–MoS2 heterojunctions, which could be generalized to the rational design of other 2D materials, heterojunctions and devices in the future.

68 citations

Journal ArticleDOI
27 Mar 2012-ACS Nano
TL;DR: Friction tests demonstrated that the polymer coating layer can enhance both the friction force and the coefficient of friction of the graphene films and protect the graphene against damage in the repeated sliding processes.
Abstract: A uniform polymer thin layer of controllable thickness was bar-coated onto a chemical vapor deposition (CVD) grown monolayer graphene surface. The effects of this coating layer on the optical, electric, and tribological properties were then investigated. The thin polymer coating layer did not reduce the optical transmittance of the graphene films. The variation in the sheet resistance of the graphene films after the coating depended on the interaction between polymer and graphene. The top coating layer can maintain the high conductivity of chemical doped graphene films under long-term ambient conditions compared with uncovered doped samples. Friction tests demonstrated that the polymer coating layer can enhance both the friction force and the coefficient of friction of the graphene films and protect the graphene against damage in the repeated sliding processes.

67 citations

Journal ArticleDOI
TL;DR: In this article, the authors demonstrate room-temperature operation of a novel mid-IR photodetector based on a graphene-Bi2Se3 heterostructure showing broadband detection and high responsivity.
Abstract: Broadband detection of mid-infrared (IR) photons extends to advanced optoelectronic applications such as imaging, sensing, and telecommunications. While graphene offers an attractive platform for broadband visible/IR photodetection, previous efforts to improve its responsivity, for example, by integrating light-absorbing colloids or waveguide or antenna fabrication, were achieved at the cost of reduced photon detection bandwidth. In this work, we demonstrate room-temperature operation of a novel mid-IR photodetector based on a graphene–Bi2Se3 heterostructure showing broadband detection and high responsivity (1.97 and 8.18 A/W at mid- and near-IR, respectively), in which simultaneous improvement of the spectral range and responsivity is achieved via exploiting broadband absorption of mid-IR and IR photons in a small-band-gap Bi2Se3 topological insulator and efficient hot carrier separation and strong photogating across the Bi2Se3/graphene interface. With sufficient room for further improvement by interface...

67 citations

Journal ArticleDOI
TL;DR: A novel and facile method to control the local water adhesion force of a thin and stretchable superhydrophobic polydimethylsiloxane (PDMS) substrate with micro-pillar arrays that allows the individual manipulation of droplet motions including moving, merging and mixing is developed.
Abstract: Here, we developed a novel and facile method to control the local water adhesion force of a thin and stretchable superhydrophobic polydimethylsiloxane (PDMS) substrate with micro-pillar arrays that allows the individual manipulation of droplet motions including moving, merging and mixing. When a vacuum pressure was applied below the PDMS substrate, a local dimple structure was formed and the water adhesion force of structure was significantly changed owing to the dynamically varied pillar density. With the help of the lowered water adhesion force and the slope angle of the formed dimple structure, the motion of individual water droplets could be precisely controlled, which facilitated the creation of a droplet-based microfluidic platform capable of a programmable manipulation of droplets. We showed that the platform could be used in newer and emerging microfluidic operations such as surface-enhanced Raman spectroscopy with extremely high sensing capability (10−15 M) and in vitro small interfering RNA transfection with enhanced transfection efficiency of ~80%.

67 citations


Cited by
More filters
01 May 1993
TL;DR: Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems.
Abstract: Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

29,323 citations

28 Jul 2005
TL;DR: PfPMP1)与感染红细胞、树突状组胞以及胎盘的单个或多个受体作用,在黏附及免疫逃避中起关键的作�ly.
Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1(PfPMP1)与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用,在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员,通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

18,940 citations

Journal ArticleDOI
TL;DR: This work reviews the historical development of Transition metal dichalcogenides, methods for preparing atomically thin layers, their electronic and optical properties, and prospects for future advances in electronics and optoelectronics.
Abstract: Single-layer metal dichalcogenides are two-dimensional semiconductors that present strong potential for electronic and sensing applications complementary to that of graphene.

13,348 citations