Hyun Ho Kim

Significance Two-dimensional magnetic semiconductors such as CrI 3 are a new class of van der Waals material that may allow for the development of novel 2D spintronic devices. While strong magnetic anisotropy within the CrI 3 layers stabilizes ferromagnetism down to a monolayer, weak antiferromagnetic coupling between the layers gives rise to extremely large tunnel magnetoresistance. We use a combination of tunneling and magneto-optical measurements to investigate the entire 2D chromium trihalid

We report the observation of a very large negative magnetoresistance effect in a van der Waals tunnel junction incorporating a thin magnetic semiconductor, CrI₃, as the active layer. At constant voltage bias, current increases by nearly one million percent upon application of a 2 T field. The effect arises from a change between antiparallel to parallel alignment of spins across the different CrI₃ layers. Our results elucidate the nature of the magnetic state in ultrathin Cr

The polymer‐supported wet transfer of chemical vapor deposition‐grown graphene provides high‐quality large‐area graphene on a target substrate. The transfer‐induced defects that result from these processes, such as micrometer‐scale folds and cracks, have been regarded as an inevitable problem. Here, the transfer processes are thoroughly examined stage‐by‐stage and it is found that lamination wrinkles, which cause defects in the graphene, are generated as a result of the high contact angles of th

Transferring graphene without water enables water-sensitive substrates to be used in graphene electronics. A polymeric bilayer (PMMA/PBU) is coated on graphene as a supporting layer for the water-free transfer process and as an excellent passivation layer that enhances device operation.

Pentacene (C22H14), a polycyclic aromatic hydrocarbon, was used as both supporting and sacrificing layers for the clean and doping-free graphene transfer. After successful transfer of graphene to a target substrate, the pentacene layer was physically removed from the graphene surface by using intercalating organic solvent. This solvent-mediated removal of pentacene from graphene surface was investigated by both theoretical calculation and experimental studies with various solvents. The uses of p

Materials that demonstrate large magnetoresistance have attracted significant interest for many decades. Extremely large tunnel magnetoresistance (TMR) has been reported by several groups across ultrathin CrI₃ by exploiting the weak antiferromagnetic coupling between adjacent layers. Here, we report a comparative study of TMR in all three chromium trihalides (CrX₃, X = Cl, Br, or I) in the two-dimensional limit. As the materials exhibit different transition temperatures and

Here, we report a substrate-induced intercalation phenomenon of an organic solvent at the interface between monolayer graphene and a target substrate. A simple dipping of the transferred chemical vapor deposition (CVD)-grown graphene on the SiO₂ substrate into chloroform (CHCl₃, CF), a common organic solvent, induces a spontaneous formation of CF clusters beneath the basal plane of the graphene as well as inside the wrinkles. The microscopic and spectroscopic observations showed the doping behav

Memristive devices whose resistance can be hysteretically switched by electric field or current are intensely pursued both for fundamental interest as well as potential applications in neuromorphic computing and phase-change memory. When the underlying material exhibits additional charge or spin order, the resistive states can be directly coupled, further allowing electrical control of the collective phases. The observation of abrupt, memristive switching of tunneling current in nanoscale juncti

Although a colonic perforation after colonoscopy is rare, if the morbidity and the mortality associated with the colonic perforation are to be reduced, prompt diagnosis and management are very important.

Solution processing is one of the most important techniques for producing large-area, uniform films for printed electronics via a low-cost process. Herein, we propose a time-controlled spin-coating method to improve the crystallinity of films of the solution-processable organic small-molecule semiconductor 6,13-bis(triisopropylsilylethynyl)pentacene (TIPS-pentacene). A key factor in this process was to halt spinning before drying had begun. We used microscopic and spectroscopic analyses to syste

Mixed layers of octadecyltrichlorosilane (ODTS) and 1H,1H,2H,2H-perfluorooctyltriethoxysilane (FOTS) on an active layer of graphene are used to induce a disordered doping state and form a robust defense system against machine-learning attacks (ML attacks). The resulting security key is formed from a 12 × 12 array of currents produced at a low voltage of 100 mV. The uniformity and inter-Hamming distance (HD) of the security key are 50.0 ± 12.3% and 45.5 ± 16.7%, respectively, indicating higher se