A facile method for the selective decoration of graphene defects based on a galvanic displacement reaction

Hong, Juree,Lee, Jae-Bok,Lee, Sanggeun,Seo, Jungmok,Lee, Hyunsoo,Park, Jeong Young,Ahn, Jong-Hyun,Il Seo, Tae,Lee, Taeyoon,Lee, Han-Bo-Ram Springer Science and Business Media LLC 2016 NPG Asia Materials Vol.8 No.-

Capillary Assembly of Silicon Nanowires Using the Removable Topographical Patterns

Hong, Juree,Lee, Seulah,Lee, Sanggeun,Seo, Jungmok,Lee, Taeyoon Materials Research Society of Korea 2014 한국재료학회지 Vol.24 No.10

We demonstrate a simple and effective method to accurately position silicon nanowires (Si NWs) at desirable locations using drop-casting of Si NW inks; this process is suitable for applications in nanoelectronics or nanophotonics. Si NWs were assembled into a lithographically patterned sacrificial photoresist (PR) template by means of capillary interactions at the solution interface. In this process, we varied the type of solvent of the SiNW-containing solution to investigate different assembly behaviors of Si NWs in different solvents. It was found that the assembly of Si NWs was strongly dependent on the surface energy of the solvents, which leads to different evaporation modes of the Si NW solution. After Si NW assembly, the PR template was cleanly removed by thermal decomposition or chemical dissolution and the Si NWs were transferred onto the underlying substrate, preserving its position without any damage. This method enables the precise control necessary to produce highly integrated NW assemblies on all length scales since assembly template is easily fabricated with top-down lithography and removed in a simple process after bottom-up drop-casting of NWs.

Graphene as an atomically thin barrier to Cu diffusion into Si

Hong, Juree,Lee, Sanggeun,Lee, Seulah,Han, Heetak,Mahata, Chandreswar,Yeon, Han-Wool,Koo, Bonwoong,Kim, Seong-Il,Nam, Taewook,Byun, Kisik,Min, Byung-Wook,Kim, Young-Woon,Kim, Hyungjun,Joo, Young-Chang The Royal Society of Chemistry 2014 Nanoscale Vol.6 No.13

<P>The evolution of copper-based interconnects requires the realization of an ultrathin diffusion barrier layer between the Cu interconnect and insulating layers. The present work reports the use of atomically thin layer graphene as a diffusion barrier to Cu metallization. The diffusion barrier performance is investigated by varying the grain size and thickness of the graphene layer; single-layer graphene of average grain size 2 ± 1 μm (denoted small-grain SLG), single-layer graphene of average grain size 10 ± 2 μm (denoted large-grain SLG), and multi-layer graphene (MLG) of thickness 5-10 nm. The thermal stability of these barriers is investigated after annealing Cu/small-grain SLG/Si, Cu/large-grain SLG/Si, and Cu/MLG/Si stacks at different temperatures ranging from 500 to 900 °C. X-ray diffraction, transmission electron microscopy, and time-of-flight secondary ion mass spectroscopy analyses confirm that the small-grain SLG barrier is stable after annealing up to 700 °C and that the large-grain SLG and MLG barriers are stable after annealing at 900 °C for 30 min under a mixed Ar and H2gas atmosphere. The time-dependent dielectric breakdown (TDDB) test is used to evaluate graphene as a Cu diffusion barrier under real device operating conditions, revealing that both large-grain SLG and MLG have excellent barrier performance, while small-grain SLG fails quickly. Notably, the large-grain SLG acts as a better diffusion barrier than the thicker MLG in the TDDB test, indicating that the grain boundary density of a graphene diffusion barrier is more important than its thickness. The near-zero-thickness SLG serves as a promising Cu diffusion barrier for advanced metallization.</P>

Single-Crystalline Silicon-Based Heterojunction Photodiode Arrays on Flexible Plastic Substrates

Sangwook Lee,Juree Hong,Ja Hoon Koo,Seulah Lee,Kwanghyun Lee,Seongil Im,Taeyoon Lee IEEE 2011 IEEE transactions on electron devices Vol.58 No.10

<P>A silicon-based photodiode array was fabricated on a flexible polyethylene terephthalate substrate using a transfer printing technique. A heterojunction structure composed of a 15-nm-thick highly doped hydrogenated amorphous-silicon (n<SUP>+</SUP> a-Si:H) layer and a 3-μm-thick p-type single-crystal silicon (p c-Si) membrane layer was adopted as the active layer of the flexible photodiode. The highly ordered photodiode array formed on the flexible substrate exhibited superior stability in electrical properties under bent conditions with no mechanical deformation. The variation of the spectral quantum efficiency (QE) under short-wavelength light illumination (λ ≤ 580 nm) was in excellent agreement with that of a heterojunction photodiode composed of a-Si:H and a bulk c-Si substrate. Relatively low QE values were observed under longer wavelength (λ ≥ 600 nm) illumination due to the finite thickness of the active layer. The <I>C</I>-<I>V</I> measurement results of the fabricated photodiode array were in accordance with the abrupt junction model. A closer inspection of the junction area of the device using high-resolution cross-sectional transmission micrograph exhibited an interface depth of 2 ± 0.5 nm, which is unavoidable in plasma-enhanced a-Si:H deposition processes.</P>

Gas‐Driven Ultrafast Reversible Switching of Super‐hydrophobic Adhesion on Palladium‐Coated Silicon Nanowires

Seo, Jungmok,Lee, Soonil,Han, Heetak,Jung, Hwae Bong,Hong, Juree,Song, Giyoung,Cho, Suk Man,Park, Cheolmin,Lee, Wooyoung,Lee, Taeyoon WILEY‐VCH Verlag 2013 ADVANCED MATERIALS Vol.25 No.30

<P><B>A gas‐driven ultrafast adhesion switching</B> of water droplets on palladium‐coated Si nanowire arrays is demonstrated. By regulating the gas‐ambient between the atmosphere and H<SUB>2</SUB>, the super‐hydrophobic adhesion is repeatedly switched between water‐repellent and water‐adhesive. The capability of modulating the super‐hydrophobic adhesion on a super‐hydrophobic surface with a non‐contact mode could be applicable to novel functional lab‐on‐a‐chip platforms.</P>

Combined SYBR Green real-time polymerase chain reaction and microarray method for the simultaneous determination of human papillomavirus loads and genotypes

( Hyun Hee Seo ),( Young Jun Kim ),( Mi Seon Jeong ),( Sung Ran Hong ),( In Ho Lee ),( Kyeong A So ),( Mi-kyung Kim ),( Yoo Kyung Lee ),( Ki Heon Lee ),( Juree Kim ),( Sung Jae Kim ),( Tae Jin Kim ) 대한산부인과학회 2016 Obstetrics & Gynecology Science Vol.59 No.6

Objective The aim of this study was to describe the principle of the Cheil HPV DNA Chip assay and evaluate its accuracy. In order to quantify the human papillomavirus (HPV) load and identify HPV genotypes simultaneously, this assay combined the two methods: SYBR Green quantitative real-time polymerase chain reaction (PCR) and DNA microarray. Methods We designed novel consensus primer sets that target the conserved region of the HPV L1 gene for quantifying and detecting a broad range of HPV types by quantitative real-time PCR. Subsequently, using the PCR products, DNA microarray was performed with 36 HPV type-specific probes. To validate this method, direct sequencing and correlation analysis among HPV genotype, viral load, and cytological abnormality was performed by Cohen`s kappa values, two-sided McNemar chi-square test, Kruskal-Wallis test, and odds ratios. Results The kappa value of the Cheil HPV DNA Chip was 0.963 (95% confidence interval, 0.919 to 0.98), which was significantly higher than the value of 0.527 (95% confidence interval, 0.447 to 0.59) obtained using a conventional HPV DNA Chip. HPV16 (χ²=62.28, P<0.01), HPV33 (χ²=7.18, P<0.01), and HPV58 (χ²=9.52, P<0.01), which are classified as high-risk HPVs, were detected at significant levels in samples with high-grade lesions. And viral loads tended to be higher in groups with high odds ratios. Conclusion The Cheil HPV DNA Chip is an effective diagnostic assay for simultaneously detecting HPV genotypes and loads in cervical samples.

Fabrication of Transferable Al₂O₃ Nanosheet by Atomic Layer Deposition for Graphene FET

Jung, Hanearl,Park, Jusang,Oh, Il-Kwon,Choi, Taejin,Lee, Sanggeun,Hong, Juree,Lee, Taeyoon,Kim, Soo-Hyun,Kim, Hyungjun American Chemical Society 2014 ACS APPLIED MATERIALS & INTERFACES Vol.6 No.4

<P>Without introducing defects in the monolayer of carbon lattice, the deposition of high-κ dielectric material is a significant challenge because of the difficulty of high-quality oxide nucleation on graphene. Previous investigations of the deposition of high-κ dielectrics on graphene have often reported significant degradation of the electrical properties of graphene. In this study, we report a new way to integrate high-κ dielectrics with graphene by transferring a high-κ dielectric nanosheet onto graphene. Al<SUB>2</SUB>O<SUB>3</SUB> film was deposited on a sacrificial layer using an atomic layer deposition process and the Al<SUB>2</SUB>O<SUB>3</SUB> nanosheet was fabricated by removing the sacrificial layer. Top-gated graphene field-effect transistors were fabricated and characterized using the Al<SUB>2</SUB>O<SUB>3</SUB> nanosheet as a gate dielectric. The top-gated graphene was demonstrated to have a field-effect mobility up to 2200 cm<SUP>2</SUP>/(V s). This method provides a new method for high-performance graphene devices with broad potential impacts reaching from high-frequency high-speed circuits to flexible electronics.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2014/aamick.2014.6.issue-4/am4052987/production/images/medium/am-2013-052987_0008.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am4052987'>ACS Electronic Supporting Info</A></P>

Induced Transition of CdSe Nanoparticle Superstructures by Controlling the Internal Flow of Colloidal Solution

Kim, Min Su,Lee, Seulah,Koo, Ja Hoon,Hong, Juree,Chung, Yongwon,Son, Kyung Jin,Koh, Won-Gun,Lee, Taeyoon American Chemical Society 2012 ACS APPLIED MATERIALS & INTERFACES Vol.4 No.10

<P>The self-assembly behaviors of flow-enhanced CdSe nanoparticle (NP) colloidal systems were investigated, which were systemically prepared by adding ethylene glycol (EG) or acetic acid (AA) to NP suspensions with deionized water (DI water) base. The additive solvents, which had higher boiling points and lower surface tensions than those of the DI water, modified the internal flow of the NP colloidal system, consequently affecting the morphologies of the generated NP superstructures after the full evaporation of their droplets. In flow-enhanced systems, NPs were formed into highly elongated dendrites that stretched from the center region to the edges along the direction of convective flow inside the droplet, while NPs in random drift system were easily aggregated to form cluster-shaped thick dendritic structures. When the volume fraction of EG was increased, the dominant superstructures were changed from dendrites to clusters, which can be mainly attributed to the changes in the dielectric properties of the NP droplets as evaporation proceeded because of the large discrepancy in the vapor pressures of EG and DI water. The balance between the interparticle potentials of electrostatic repulsion and van der Waals attraction was continuously altered, resulting in the formation of clusters with increasing EG ratio. Contrastively, the transition of superstructures could not be observed in the case of colloidal system prepared by mixing DI water and AA, which can be ascribed to the similar vapor pressures of the two solvents; the dielectric properties of the solution mixture was barely changed throughout the steady evaporation process, which resulted in the formation of uniformly distributed highly elongated dendrites. Polarization-dependent imaging experiments and photoluminescence measurements revealed that the stretched dendrites formed under the flow-enhanced conditions showed higher crystallinity than that of the clusters.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2012/aamick.2012.4.issue-10/am301798r/production/images/medium/am-2012-01798r_0007.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am301798r'>ACS Electronic Supporting Info</A></P>