김태환 교수

Abstract Camouflage is an emerging application of metamaterials owing to their exotic electromagnetic radiative properties. Based on the use of a selective emitter and an absorber as the metamaterials, most reported articles have suggested the use of single‐band camouflage, however, multispectral camouflage is a challenging issue owing to a difference of several orders of magnitude in the unit cell structure. Herein, hierarchical metamaterials (HMMs) for multispectral signal control when dissipa

Copper is the current interconnect metal of choice in integrated circuits. As interconnect dimensions decrease, the resistivity of copper increases dramatically because of electron scattering from surfaces, impurities, and grain boundaries (GBs) and threatens to stymie continued device scaling. Lacking direct measurements of individual scattering sources, understanding of the relative importance of these scattering mechanisms has largely relied on semiempirical modeling. Here we present the firs

We describe the development and the capabilities of an advanced system for nanoscale electrical transport studies. This system consists of a low temperature four-probe scanning tunneling microscope (STM) and a high-resolution scanning electron microscope coupled to a molecular-beam epitaxy sample preparation chamber. The four STM probes can be manipulated independently with subnanometer precision, enabling atomic resolution STM imaging and four-point electrical transport study of surface electro

We investigated phase defects in a quasi-one-dimensional commensurate charge-density wave (CDW) system, an In atomic wire array on Si(111), using low temperature scanning tunneling microscopy. The unique fourfold degeneracy of the CDW state leads to various phase defects, among which intrinsic solitons are clearly distinguished. The solitons exhibit a characteristic variation of the CDW amplitude with a coherence length of about 4 nm, as expected from the electronic structure, and a localized el

The complex interplay between the electron and lattice degrees of freedom produces multiple nearly degenerate electronic states in correlated electron materials. The competition between these degenerate electronic states largely determines the functionalities of the system, but the invoked mechanism remains in debate. By imaging phase domains with electron microscopy and interrogating individual domains in situ via electron transport spectroscopy in double-layered Sr(3)(Ru(1-x)Mn(x))(2)O(7) (x =

In this paper, we propose a lying posture discrimination algorithm to monitor the behavior pattern of a person lying in bed. Using FSR (force sensing resistor) sensors arranged in a grid structure, three major body parts such as head , shoulder , and hips are identified, and six lying positions are determined based on these body parts. Head, shoulder, and hips are relatively high in pressure and are easy to distinguish due to low movement. In addition, we have effectively limited the search spac

Although a prototypical Su-Schrieffer-Heeger (SSH) soliton exhibits various important topological concepts including particle-antiparticle (PA) symmetry and fractional fermion charges, there have been only few advances in exploring such properties of topological solitons beyond the SSH model. Here, by considering a chirally extended double-Peierls-chain model, we demonstrate novel PA duality and fractional charge e/2 of topological chiral solitons even under the chiral symmetry breaking. This pr

The electrical transport properties of individual carbon nanotubes (CNTs) and multi-terminal junctions of CNTs are investigated with a quadraprobe scanning tunneling microscope. The CNTs used in this study are made of stacked herringbone-type conical graphite sheets with a cone angle of ∼20° to the tube axis, and the CNT junctions have no catalytic particles in the junction areas. The CNTs have a significantly higher resistivity than conventional CNTs with concentric walls. The straight CNTs dis

In a recent article 1 , Huda et al. demonstrated tuneable topological domain wall states in the c (2 × 2) chlorinated Cu(100) 2 . Their system allows to experimentally tune the domain wall states using atom manipulation by the tip of a scanning tunneling microscope (STM). They have realized topological domain wall states of two prototypical one-dimensional models such as trimer 3 and coupled dimer chains 4 , 5 , 6 , 7 , 8 . However, they did not distinguish trivial domain wall states 9 from topo

We report the direct measurement of individual grain boundary (GB) resistances and the critical role of GB structure in the increased resistivity in copper nanowires. By measuring both intra- and inter-grain resistance with a four-probe scanning tunneling microscope, large resistance jumps are revealed owing to successive scattering across high-angle random GBs, while the resistance changes at twin and other coincidence boundaries are negligibly small. The impurity distributions in the nanowires

Two competing structures, ``ridges'' and ``troughs,'' are observed in the first epitaxial layer of Ag on the W(110) surface with a scanning tunneling microscope. The mixed tensile and compressive strain is locally relieved by ridges and troughs in the epitaxial layer. Ag atoms are mainly commensurate with the body-centered-cubic sites of the W(110) substrate, and are partly incommensurate around misfit dislocations. The energy barrier and kinetics between these two structures are sufficiently lo