Publications (16)45.65 Total impact
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Article: Multi-layer nanogap array for high-performance SERS substrate.
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ABSTRACT: A multi-layer nanogap array composed of three linearly aligned gold nanogaps is fabricated for a surface-enhanced Raman spectroscopy (SERS) substrate. The overall process for the proposed structure is simple and reliable with the use of a photolithography-free fabrication process, which includes only deposition and etching. Chemical vapor deposition (CVD) is employed to form a uniform and highly controllable nanogap array. The nanogap width, a crucial parameter in SERS, is determined by the sacrificial film thickness of CVD. Experiments on nanogap width and polarization angle dependence are carried out to characterize the fabricated multi-layer nanogap array as an SERS substrate.Nanotechnology 06/2011; 22(23):235303. · 3.98 Impact Factor -
Article: Nanogap electrode fabrication for a nanoscale device by volume-expanding electrochemical synthesis.
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ABSTRACT: A novel nanogap fabrication method using an electrochemical nanopatterning technique is presented. Electrochemical deposition of platinum ions reduces the microgap size to the sub-50-nm range due to the self-limited volume expansion of the electrodes. Additionally, the low crystallinity of platinum reduces the line edge roughness in the electrodes, whereas the high crystallinity of gold increases it. Current compliance, a buffered resistor, and a symmetric deposition strategy are used to achieve high reliability and practicality of nanogap electrodes. As a possible application, an organic thin-film transistor using the nanogap electrodes is also demonstrated.Small 05/2011; 7(15):2210-6. · 8.35 Impact Factor -
Article: Label-free detection of DNA hybridization using pyrene-functionalized single-walled carbon nanotubes: effect of chemical structures of pyrene molecules on DNA sensing performance.
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ABSTRACT: We investigate the effect of functional groups of pyrene molecules on the electrical sensing performance of single-walled carbon nanotubes (SWNTs) based DNA biosensor, in which pyrenes with three different functional groups of carboxylic acid (Py-COOH), aldehyde (Py-CHO) and amine (Py-NH2) are used as linker molecules to immobilize DNA on the SWNT films. UV/Visible absorption spectra results show that all of the pyrene molecules are successfully immobilized on the SWNT surface via pi-pi stacking interaction. Based on fluorescence analysis, we show that the amide bonding of amine terminated DNA via pyrene containing carboxylic groups is the most efficient to immobilize DNA on the nanotube film. The electrical detection results show that the conductance of Py-COOH modified SWNT film is increased upon DNA immobilization, followed by further increase after hybridization of target DNAs. It indicates that the pyrene molecules with carboxylic acid groups play an important role to achieve highly efficient label-free detection by nondestructive and specific immobilization of DNAs.Journal of Nanoscience and Nanotechnology 05/2011; 11(5):4210-6. · 1.56 Impact Factor -
Article: Surface-modified microelectrode array with flake nanostructure for neural recording and stimulation.
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ABSTRACT: A novel microelectrode modification method is reported for neural electrode engineering with a flake nanostructure (nanoflake). The nanoflake-modified electrodes are fabricated by combining conventional lithography and electrochemical deposition to implement a microelectrode array (MEA) on a glass substrate. The unique geometrical properties of nanoflake sharp tips and valleys are studied by optical, electrochemical and electrical methods in order to verify the advantages of using nanoflakes for neural recording devices. The in vitro recording and stimulation of cultured hippocampal neurons are demonstrated on the nanoflake-modified MEA and the clear action potentials are observed due to the nanoflake impedance reduction effect.Nanotechnology 02/2010; 21(8):85303. · 3.98 Impact Factor -
Article: Pt/Au bimetallic hierarchical structure with micro/nano-array via photolithography and electrochemical synthesis: From design to GOT and GPT biosensors.
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ABSTRACT: A novel matrix for enzyme immobilization was successfully developed by using Pt/Au bimetallic hierarchical structure with micro/nano-array to generate highly sensitive biosensors for glutamic oxaloacetic transaminase (GOT, EC 2.6.1.1) and glutamic pyruvic transaminase (GPT, EC 2.6.1.2) determination. The structures of the Pt/Au particles were confirmed with a dual-beam FIB image, transmission electron microscopy (TEM), selected area electron diffraction (SAED) pattern, and X-ray diffraction (XRD) pattern. The morphologies of the Pt/Au bimetallic hierarchical structure before and after enzyme modification were checked using scanning electron microscopy (SEM). The effects of Nafion membrane and enzyme loading were established. Both GOT and GPT activities have been investigated singly and sequentially. The sensing performances were recorded by employing cyclic voltammetric and chronoamperometry (concentration variations of GOT and GPT) techniques. The interference of ascorbic acid and uric acid was also included. We believe that this study will provide a good inspiration in the development of new generation amperometric biosensors.Talanta 07/2009; 78(4-5):1371-7. · 3.79 Impact Factor -
Article: A well-ordered flower-like gold nanostructure for integrated sensors via surface-enhanced Raman scattering.
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ABSTRACT: A controllable flower-like Au nanostructure array for surface-enhanced Raman scattering (SERS) was fabricated using the combined technique of the top-down approach of conventional photolithography and the bottom-up approach of electrodeposition. Au nanostructures with a mean roughness ranging from 5.1 to 49.6 nm were obtained by adjusting electrodeposition time from 2 to 60 min. The rougher Au nanostructure provides higher SERS enhancement, while the highest SERS intensity obtained with the Au nanostructure is 29 times stronger than the lowest intensity. The SERS spectra of brilliant cresyl blue (BCB), benzenethiol (BT), adenine and DNA were observed from the Au nanostructure.Nanotechnology 07/2009; 20(23):235302. · 3.98 Impact Factor -
Article: The Effect of Network Density on the DNA-Sensing Performance of Single-Walled Carbon Nanotubes
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ABSTRACT: The effect of network density of single-walled carbon nanotubes (SWNTs) on the detection of DNA hybridization was investigated. The results show that, in contrast to those having higher densities, SWNTs with low network densities in the conductance range of 0.74 × 10-7 < Gbare < 2.00 × 10-7 exhibit high sensitivity for detection of immobilized DNAs. The resulting SWNT devices with optimal network densities showed good selectivity in detecting cDNA hybridization. The network density control will provide opportunities to realize practical label free biosensor utilizing commercially available SWNT networks.The Journal of Physical Chemistry C. 01/2009; 113:21556. -
Article: Doping-free nanoscale complementary carbon-nanotube field-effect transistors with DNA-templated molecular lithography.
Small 11/2008; 4(11):1959-63. · 8.35 Impact Factor -
Article: Controlled Molecularly Mediated Assembly of Gold Nanooctahedra for a Glucose Biosensor
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ABSTRACT: This article describes the controllable construction of a layered superstructure of gold nanooctahedra via a molecularly mediated assembly and their electrochemical application as a host matrix toward the oxidation of glucose. The layered superstructures of the Au nanooctahedra were confirmed with atomic force microscopy, X-ray electron spectroscopy, and cyclic voltammograms. The effects of the interface of gold spherical nanoparticles and the different layered interface of gold nanooctahedra on the electrochemical responses to Fe(CN)63- and glucose were investigated in detail. The glucose biosensor, which uses the Au nanooctahedra layer structure as a matrix, shows excellent electrocatalytic activities, such as a high level of sensitivity, a fast response, and a wide response range.02/2008; -
Conference Proceeding: A Nanowire Transistor for High Performance Logic and Terabit Non-Volatile Memory Devices
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ABSTRACT: Silicon nanowire-FET (SiNAWI-FET) for high performance logic device with consideration of current direction effects and terabit non-volatile memory (NVM) device using an 8 nm SiNAWI-NVM with oxide/nitride/oxide (ONO) and omega-gate structure is reported for the first time. N-and P-channel SiNAWI-FET showed the highest driving current on (110)/<110> crystal orientation without device rotation, whereas most 3-dimensional NMOS report higher driving current on 45deg device rotation rather than 0deg. Utilizing an 7 nm spherical nanowire on the 8 nm SiNAWI-NVM with ONO structure, 1.7 V V<sub>T</sub>-window was achieved from 12 V/80 musec program conditions with retention enhancement.VLSI Technology, 2007 IEEE Symposium on; 07/2007 -
Article: Direct electrochemistry of uric acid at chemically assembled carboxylated single-walled carbon nanotubes netlike electrode.
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ABSTRACT: Carboxylated single-walled carbon nanotubes (SWCNT) chemically assembled on gold substrate was employed as netlike electrode to investigate the charge-transfer process and electrode process kinetics using uric acid as an example. The electrochemical behavior of uric acid in carboxylated SWCNT system was investigated using cyclic voltammetry, chronoamperometry, and single potential time-based techniques. The properties of raw SWCNT electrode were also studied for comparison purpose. Uric acid has better electrochemical behavior whereas ascorbic acid has no effective reaction on the carboxylated SWCNT electrode. Cyclic voltammograms indicate that the assembled carboxylated SWCNT increases more active sites on electrode surface and slows down the electron transfer between the gold electrode and uric acid in solution. The charge-transfer coefficient (alpha) for uric acid and the rate constant (k) for the catalytic reaction were calculated as 0.52 and 0.43 s(-1), respectively. The diffusion coefficient of 0.5 mM uric acid was 7.5 x 10(-6) cm2 x s(-1). The results indicate that electrode process in the carboxylated SWCNT electrode system is governed by the surface adsorption-controlled electrochemical process.The Journal of Physical Chemistry B 12/2006; 110(43):21850-6. · 3.70 Impact Factor -
Article: Morphology-controlled SWCNT/polymeric microsphere arrays by a wet chemical self-assembly technique and their application for sensors
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ABSTRACT: Large-scale morphology-controlled SWCNT/polymeric microsphere arrays can be obtained by a wet chemical self-assembly technique. The loading of SWCNTs, the length of SWCNTs, and the size and nature of polymeric microspheres can easily be controlled. Similar results can also be reached using this method for MWCNTs. In both types of CNTs, they form an interesting interactive 'net' structure on spheres and sphere joints. The SWCNT/PS-modified Au electrode was used for detection of uric acid by cyclic voltammetry and single-potential time-based techniques. The preliminary results show that the modified electrode presents good sensitivity and stability to uric acid.Nanotechnology 06/2006; 17(12):2988. · 3.98 Impact Factor -
Article: Morphology-controlled SWCNT/polymeric microsphere arrays by a wet chemical self-assembly technique and their application for sensors
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ABSTRACT: Large-scale morphology-controlled SWCNT/polymeric microsphere arrays can be obtained by a wet chemical self-assembly technique. The loading of SWCNTs, the length of SWCNTs, and the size and nature of polymeric microspheres can easily be controlled. Similar results can also be reached using this method for MWCNTs. In both types of CNTs, they form an interesting interactive 'net' structure on spheres and sphere joints. The SWCNT/PS-modified Au electrode was used for detection of uric acid by cyclic voltammetry and single-potential time-based techniques. The preliminary results show that the modified electrode presents good sensitivity and stability to uric acid.Nanotechnology 01/2006; 17:2988-2993. · 3.98 Impact Factor -
Article: Sub5nm All-Around Gate FinFET for Ultimate Scaling
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ABSTRACT: Sub-5nm all-around gate FinFETs with 3nm fin width were fabricated for the first time. The n-channel FinFET of sub-5nm with 1.4nm HfO2 shows an IDsat of 497muA/mum at VG=V D=1.0V. Characteristics of sub-5nm transistor are verified by using 3-D simulations as well as analytical models. A threshold voltage increases as the fin width reduces by quantum confinement effects. The threshold voltage shift was fitted to a theoretical model with consideration of the first-order perturbation theory. And a channel orientation effect, based on a current-flow direction, is shown01/2006; -
Conference Proceeding: Sub-5nm All-Around Gate FinFET for Ultimate Scaling
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ABSTRACT: Sub-5nm all-around gate FinFETs with 3nm fin width were fabricated for the first time. The n-channel FinFET of sub-5nm with 1.4nm HfO<sub>2 </sub> shows an I<sub>Dsat</sub> of 497muA/mum at V<sub>G</sub>=V <sub>D</sub>=1.0V. Characteristics of sub-5nm transistor are verified by using 3-D simulations as well as analytical models. A threshold voltage increases as the fin width reduces by quantum confinement effects. The threshold voltage shift was fitted to a theoretical model with consideration of the first-order perturbation theory. And a channel orientation effect, based on a current-flow direction, is shownVLSI Technology, 2006. Digest of Technical Papers. 2006 Symposium on; -
Article: Wafer-scale controlled Au/Pt bimetallic flowerlike structure array
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ABSTRACT: The combining of the bottom-up with top-down techniques is essential to construct novel micro-/ nano-materials according to the requirements of its end applications. This paper describes a pattern-directed method that combines the advantages of photolithography and electrochemical synthesis to construct a wafer-scale Au/Pt bimetallic flowerlike structure array. With this technique, Au/Pt bimetallic flowerlike structure arrays are homogeneously and highly-selectively synthesized from Au patterns with different spacing, dimensions and shapes on a 4-inch silicon wafer. The Au/Pt flowers are also well-constructed in the different designed array such as 'KAIST' and 'NOBEL'. The surface morphology of the Au/Pt flower was observed using scanning electron microscope (SEM). The chemical composition of the bimetallic flower was confirmed using energy dispersive spectrometer (EDS) and X-ray electron spectroscopy (XPS). The X-ray diffraction (XRD) patterns of the Au pitch and Si substrate on a wafer were studied to reveal the highly-selective growth from Au pitches. A time-dependent evolution clearly presents the different growth stages of Au/Pt flower. The analysis of Au/Pt flower growth process in an individual Au pitch shows an edge-selective particle development mechanism. The method can be applied to the construction of other interesting nano/microflower arrays of metals or metal oxides. The results would be helpful for the creation of the flower with regular physical attributes (shapes and sizes) and guiding the design of a perfect array for technological innovations. -
Article: Controlled Synthesis of Gold Nanocomplex Arrays by a Combined Top-Down and Bottom-Up Approach and Their Electrochemical Behavior
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ABSTRACT: Patterned arrays of Au nanocomplexes with various features were fabricated over large areas by photolithography with electrochemical synthesis. This combined top-down and bottom-up approach eliminates the significant drawbacks (e.g., small areas, nonhomogeneity, nonuniform distribution) encountered with conventional bottom-up techniques. The effects of the applied voltage, the concentration of the HAuCl 4 solution, and the initial Au pattern size on a Au nanocomplex structure array were investigated. The results show that the Au nanocomplex array can be constructed according to different requirements. Electrochemical experiments clearly imply that the Au nanocomplex array electrode exhibits excellent electrochemical sensitivity and capacitance. A Au nanocomplex array on a large template prepared via the top-down and bottom-up approach can be applied to the areas of chemical sensing and optical signal processing in nanoelectronic devices.
Top co-authors
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Institutions
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2006–2007
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Korea Advanced Institute of Science and Technology
Seoul, Seoul, South Korea
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