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.

Electrode and electronic device comprising the same

Abstract: A graphene electrode having a surface modified to have a high work function, and an electronic device including the same.

Improvement of work function and hole injection efficiency of graphene anode using CHF3 plasma treatment

Abstract: We report improvement of hole injection efficiency of a graphene anode by tuning its work function (WF) via surface fluorination. We used chemical vapor deposition to synthesize high-quality graphene sheets and then treated them with CHF3 plasma to induce fluorination. We used x-ray photoelectron spectroscopy to examine the fluorine coverage and the kind of chemical bonds in fluorinated graphene (FG). Also, we used ultraviolet photoelectron spectroscopy to systematically study the changes in the WF and sheet resistance of the FG sheets with varying plasma exposure time (0, 10, 30, 60, 90 s) to find an optimum fluorination condition for hole injection. The WF of graphene sheets was increased by up to 0.74 eV, as a result of the formation of carbon-fluorine bonds that function as negative surface dipoles. We fabricated hole-only devices and conducted dark injection space-charge-limited-current transient measurement; the fluorination greatly increased the hole injection efficiency of graphene anodes (from 0.237 to 0.652). The enhanced hole injection efficiency of FG anodes in our study provides wide opportunities for applications in graphene-based flexible/stretchable organic optoelectronics.

Rational design of high-performance wearable tactile sensors utilizing bioinspired structures/functions, natural biopolymers, and biomimetic strategies

Abstract: Nature has created high-performance materials and structures over millions of years of evolution. Inspired by the concepts and design principles evident in natural materials and structures, high-performance tactile sensors, based on bioinspired structures/functions, natural biopolymers, and biomimetic strategies, have been developed. However, the primary challenge is to develop novel sensing mechanisms and device structures that are sufficiently sensitive and stretchable using bioinspired materials. Herein, we review the recent advancements made in this field, focusing on biomimetic approaches to produce tactile sensors with essential sensing capabilities and the development of bioinspired materials with the desired electrical and mechanical properties. In addition, we highlight the potential applications of these devices and discuss the potential directions for future work.

Crypto primitive of MOCVD MoS2 transistors for highly secured physical unclonable functions

Abstract: Physically unclonable crypto primitives have potential applications for anti-counterfeiting, identification, and authentication, which are clone proof and resistant to variously physical attack. Conventional physical unclonable function (PUF) based on Si complementary metal-oxide-semiconductor (CMOS) technologies greatly suffers from entropy loss and bit instability due to noise sensitivity. Here we grow atomically thick MoS2 thin film and fabricate field-effect transistors (FETs). The inherently physical randomness of MoS2 transistors from materials growth and device fabrication process makes it appropriate for the application of PUF device. We perform electrical characterizations of MoS2 FETs, collect the data from 448 devices, and generate PUF keys by splitting drain current at specific levels to evaluate the response performance. Proper selection of splitting threshold enables to generate binary, ternary, and double binary keys. The generated PUF keys exhibit good randomness and uniqueness, providing a possibility for harvesting highly secured PUF devices with two-dimensional materials.

Stretchable Si Logic Devices with Graphene Interconnects.

Abstract: Stretchable integrated circuits consisting of ultrathin Si transistors connected by multilayer graphene are demonstrated. Graphene interconnects act as an effective countervailing component to maintain the electrical performance of Si integrated circuits against external strain. Concentration of the applied strain on the graphene interconnect parts can stably protect the Si active devices against applied strains over 10%.

Fast parallel algorithms for short-range molecular dynamics

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.

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

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。

Electronics and optoelectronics of two-dimensional transition metal dichalcogenides.

Abstract: Single-layer metal dichalcogenides are two-dimensional semiconductors that present strong potential for electronic and sensing applications complementary to that of graphene.