김철주 교수

The ability to control the stacking structure in layered materials could provide an exciting approach to tuning their optical and electronic properties. Because of the lower symmetry of each constituent monolayer, hexagonal boron nitride (h-BN) allows more structural variations in multiple layers than graphene; however, the structure-property relationships in this system remain largely unexplored. Here, we report a strong correlation between the interlayer stacking structures and optical and top

We report a diameter-dependent photoconduction gain in intrinsic Ge nanowire (NW) photodetectors. By employing a scanning photocurrent imaging technique, we provide evidence that the photocarrier transport is governed by the hole drift along the Ge NWs, ensuing the higher internal gain up to approximately 10(3) from the thin NWs. It is found that the magnitudes of both gain and photoconductivity are inversely proportional to the NW diameter ranging from 50 to 300 nm. We attribute our observation

A simple and controlled growth of metallic NiSi nanowires at low temperatures (< 400 °C) by a chemical vapor deposition using SiH4 at a low supersaturation limit is reported. It is demonstrated that the simple and low temperature synthesis of metallic nanowires is compatible with conventional Si processing and provide interesting strategies for their possible applications as interconnects in Si microelectronics and as field emitters in field emission displays.

We report a method that uses van der Waals interactions to transfer continuous, high-quality graphene films from Ge(110) to a different substrate held by hexagonal boron nitride carriers in a clean, dry environment. The transferred films are uniform and continuous with low defect density and few charge puddles. The transfer is effective because of the weak interfacial adhesion energy between graphene and Ge. Based on the minimum strain energy required for the isolation of film, the upper limit o

An on-nanowire (on-NW) band-graded photodetector that pertains to the on-nanowire composition gradation from pure Si to pure Ge, Si1–xGex (0 ≤ x ≤ 1), is reported. The spectral onset of interband photocarrier generation and photocurrent amplitude are on-NW de-multiflexed over the continuously varying energy band gap and surface trap state density in an individually addressable manner. Detailed facts of importance to specialist readers are published as ”Supporting Information”. Such documents are

The authors present the demonstration of nanowire field-effect transistors incorporating group IV alloy nanowires, Si1−xGex. Single-crystalline Si1−xGex alloy nanowires were grown by a Au catalyst-assisted chemical vapor synthesis using SiH4 and GeH4 precursors, and the alloy composition was reproducibly controlled in the whole composition range by controlling the kinetics of catalytic decomposition of precursors. Complementary in situ doping of Si1−xGex nanowires was achieved by PH3 and B2H6 in

Abstract Monitoring taste‐inducing ions and molecules continuously in liquids or solutions is of great considerable matter for the realization of the electronic tongue (E‐tongue). Particularly from the five major tastes, the highly selective, sensitive detection of Na + in real‐time is prioritized. Prioritization is due to the saltiness of food is the key ingredient in most meals. Nevertheless, existing Na + detecting devices have relatively low performances of selectivity, sensitivity, and lack

Crystalline films offer various physical properties based on the modulation of their thicknesses and atomic structures. The layer-by-layer assembly of atomically thin crystals provides a powerful means to arbitrarily design films at the atomic level, which are unattainable with existing growth technologies. However, atomically clean assembly of the materials with high scalability and reproducibility remains challenging. We report programmed crystal assembly of graphene and monolayer hexagonal bo

Engineering the boundary structures in 2D materials provides an unprecedented opportunity to program the physical properties of the materials with extensive tunability and realize innovative devices with advanced functionalities. However, structural engineering technology is still in its infancy, and creating artificial boundary structures with high reproducibility remains difficult. In this review, various emergent properties of 2D materials with different grain boundaries, and the current tech

Metal (M) contact with a semiconductor (S) introduces metal-induced gap states (MIGS), which makes it difficult to study the intrinsic electrical properties of S. A bilayer of metal with graphene (Gr), <i>i.e</i>., a M/Gr bilayer, may form a contact with S to minimize MIGS. However, it has been challenging to realize the pristine M/Gr/S junctions without interfacial contaminants, which result in additional interfacial states. Here, we successfully demonstrate the atomically clean M/Gr/<i>n</i>-t

We demonstrate fabrication of vertically aligned, intrananowire p-n diodes by large-area epitaxial growth of Si nanowires (NWs). The axially modulated doping profile of p-n junctions is achieved by in situ doping with alternating addition of dopants in the axial sequence during Au-assisted chemical vapor deposition. We provide direct evidence of the intra-NW p-n junctions using scanning local probes in both individual NWs and vertically aligned NWs at large areas. Our study suggests implication

The role of electronic doping in determining the luminescence efficiency of low-dimensional halide perovskites has been challenging to test due to the structural complexity resulting from conventional dopant use. In this study, we demonstrate that van der Waals contact of aluminum (Al) onto a two-dimensional tin halide perovskite, phenethylammonium tin iodide (PEA2SnI4), enhances photoluminescence (PL) intensity significantly, reaching a record-high PL quantum yield of 10%. The intensity relies

Quasi-one-dimensional (1D) graphene nanoribbons (GNRs) have finite band gaps and active edge states and therefore can be useful for advanced chemical and electronic devices. Here, we present the formation of GNR grids via seed-assisted chemical vapor deposition on Ge(100) substrates. Nucleation seeds, provided by unzipped C₆₀, initiated growth of the GNRs. The GNRs grew toward two orthogonal directions in an anisotropic manner, templated by the single crystalline substrate, thereby fo