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Hyun-Mi Kim

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Papers by Hyun-Mi Kim

Microstructural Evolution of MgB2 Layers Prepared by Post Annealing of Evaporated Boron and Co-Evaporated MgBx (x = 1.1~4.3) Films

Materials Science Forum, 2005

... Prepared by Post Annealing of Evaporated Boron and Co-evaporated MgB (x = 1,1-4.3) Films Ki-... more

RuO2 thin film fabrication with plasma-enhanced chemical vapor deposition

Thin Solid Films, 1999

The deposition of RuO2 thin films by plasma-enhanced chemical vapor deposition (PECVD) with ruthe... more

Identifying the Location of a Single Protein along the DNA Strand Using Solid-State Nanopores

ACS Nano, 2015

Solid-state nanopore has been widely studied as an effective tool to detect and analyze small bio... more Solid-state nanopore has been widely studied as an effective tool to detect and analyze small biomolecules, such as DNA, RNA, and proteins, at a single molecule level. In this study, we demonstrate a rapid identification of the location of zinc finger protein (ZFP), which is bound to a specific locus along the length of a double-stranded DNA (dsDNA) to a single protein resolution using a low noise solid-state nanopore. When ZFP labeled DNAs were driven through a nanopore by an externally applied electric field, characteristic ionic current signals arising from the passage of the DNA/ZFP complex and bare DNA were detected, which enabled us to identify the locations of ZFP binding site. We examined two DNAs with ZFP binding sites at different positions and found that the location of the additional current drop derived from the DNA/ZFP complex is well-matched with a theoretical one along the length of the DNA molecule. These results suggest that the protein binding site on DNA can be mapped or that genetic information can be read at a single molecule level using solid-state nanopores.

Fabrication and verification of DNA functionalized nanopore with gold layer embedded structure for bio-molecular sensing

2011 IEEE Nanotechnology Materials and Devices Conference, 2011

Solid-state nanopore has been attracted by its great potential for bio-molecular analysis. Nanopo... more Solid-state nanopore has been attracted by its great potential for bio-molecular analysis. Nanopore is considered as promising tools for label-free single-molecule detection. As one of the techniques of nanopores, chemically modified or functionalized nanopore is considered to be a great candidate for a bio-molecule sensor. In this work, gold layer embedded nanopore was used for specific functionalization, because Au layer

Multilayer diffusion barrier for copper metallization using a thin interlayer metal (M=Ru, Cr, and Zr) between two TiN films

Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 2003

A multilayer structure ͓TiN͑5 nm͒/interlayer metal͑2 nm͒/TiN͑5 nm͔͒ has been evaluated as a diffu... more A multilayer structure ͓TiN͑5 nm͒/interlayer metal͑2 nm͒/TiN͑5 nm͔͒ has been evaluated as a diffusion barrier between copper and silicon. Three metals (MϭRu, Cr, and Zr͒ were tested as interlayer materials for the multilayer diffusion barrier scheme, expecting that they will stuff the TiN grain boundaries by forming metal oxides therein. The diffusion barrier performance was found to be the best when the Zr was used as an interlayer material. X-ray diffractometry showed that the Zr interlayer diffusion barrier failed only after annealing at 800°C for 30 min due to the formation of copper silicide while the reference sample without a metal interlayer failed when annealed at 600°C. The insertion of Cr also was also found to enhance the diffusion barrier performance, whereas, Ru has little effect on the improvement of the barrier performance. High-resolution transmission electron microscopy and energy dispersive spectroscopy showed that Zr significantly diffused into TiN grain boundaries while Ru did not diffuse during annealing. An explanation of the variation of the diffusion barrier performance with the change of an interlayer metal is given in terms of Gibbs free energy change of the respective metal-oxide formation.

Metal-Induced Nickel Silicide Nanowire Growth Mechanism in the Solid State Reaction

MRS Proceedings, 2006

A unique nanowire growth was accomplished at 575 oC by the metal-induced growth (MIG). That is a ... more A unique nanowire growth was accomplished at 575 oC by the metal-induced growth (MIG). That is a spontaneous reaction between metal and Si. The deposited metal worked as a catalyst layer to grow nanowire in the solid-state. Various metals (Ni, Co, and Pd) were used in MIG nanowire fabrication and Ni-induced case was successful in demonstrating that metal species should be a dominant mover in nanowire growth. Transmission electron microscopy investigation was performed to observe the nanowire growth direction. The Ni to Si composition was studied by energy dispersive spectroscopy showing the Ni diffusion inside the nanowire as well as the Ni silicide layer. The practical application MIG nanowire was proven by fabricating nanoscale contacts.

A Low-Noise Solid-State Nanopore Platform Based on a Highly Insulating Substrate

Scientific Reports, 2014

A solid-state nanopore platform with a low noise level and sufficient sensitivity to discriminate... more A solid-state nanopore platform with a low noise level and sufficient sensitivity to discriminate single-strand DNA (ssDNA) homopolymers of poly-A 40 and poly-T 40 using ionic current blockade sensing is proposed and demonstrated. The key features of this platform are (a) highly insulating dielectric substrates that are used to mitigate the effect of parasitic capacitance elements, which decrease the ionic current RMS noise level to sub-10 pA and (b) ultra-thin silicon nitride membranes with a physical thickness of 5 nm (an effective thickness of 2.4 nm estimated from the ionic current) are used to maximize the signal-to-noise ratio and the spatial depth resolution. The utilization of an ultra-thin membrane and a nanopore diameter as small as 1.5 nm allow the successful discrimination of 40 nucleotide ssDNA poly-A 40 and poly-T 40. Overall, we demonstrate that this platform overcomes several critical limitations of solid-state nanopores and opens the door to a wide range of applications in single-molecule-based detection and analysis. N anopores have attracted considerable attention because of their potential applications in the detection and analysis of single biomolecules, such as DNA, RNA, and proteins 1-6. In particular, DNA sequencing has driven the technology forward due to its inherent sensitivity, high throughput, amplification-free sample preparation, and lack of labels 7-12. The sub-molecular details of an individual molecule can be gathered via recording modulations in the ionic current when a molecule passes through the nanopore under the effect of a voltage applied across the pore. A series of impressive developments has been made in the area of protein nanopores using either a-hemolysin 7-10 or MspA 11-13 as they possess a low noise level and guarantee the reliable formation of a small pore aperture (1.5 nm) and an extremely thin sensing zone of approximately 1 nm. Combining these advantages with a recently developed method for slowing down DNA translocation using phi29 polymerase enzymes 10,13 makes this platform quite promising. In contrast, the development of solid-state nanopores has been much slower and limited to merely detecting the translocation of DNA molecules, although solid-state nanopore platforms have obvious advantages over their biological counterpart such as high stability, an adjustable geometry, controllable surface properties, and the potential for integration into stand-alone devices 14-16. The reliable formation of small nanopores (, 2 nm in diameter), fabrication of an extremely thin sensing zone with a thickness comparable to the spacing of each nucleotide, decrease of the noise level, and control of the translocation speed that would guarantee sufficient time to sense each nucleotide are the few challenges that limit the performance of solid-state nanopores. Among these issues, the excess noise level in solid-state nanopores (a few tens of pA to 100 pA: ,10 times larger than that of protein counterparts 17-20) has been one of the key issues responsible for the degraded signal-to-noise ratio and temporal and spatial resolution. In particular, the elevated parasitic capacitance generates a high level of dielectric noise that prevents sampling at high bandwidths. To effectively reduce the dielectric noise, several methods have been adopted such as thick dielectric layer deposition underneath an active SiN x membrane 21-23 , PDMS sealing 22,24 , the utilization of glass nanopores 25,26 , and machining of solid-state nanopores between dielectric membranes 27. All these platforms have resulted in a significant reduction of the noise level followed by some ramifications such as the need for additional processing to insert a thick SiO 2 layer underneath the SiN x layer and the reduction of the SiN x (,80 nm) thickness to the scale of sub-10 nm. In addition, the manual coating of PDMS sacrifices accuracy and reproducibility; the fabrication of small

The effect of ion beam bombardment on the properties of Ta(C)N films deposited from pentakis-diethylamido-tantalum

Thin Solid Films, 2002

TaN or TaCN films were deposited using a single source, pentakis-diethylamido-tantalum as diffusi... more TaN or TaCN films were deposited using a single source, pentakis-diethylamido-tantalum as diffusion barrier for copper metallization. N-and Ar-ion beams with energy of 120 eV were used for bombarding the film during growth to improve the film quality. The films deposited using N-ion beam showed a resistivity of approximately 950 mV cm and a density of 7.65 gycm. 3 The use of the N-ion beam, however, drastically degraded the step coverage of the film (;5% at the 0.5 mm contact holes with aspect ratio of 3:1). On the other hand, the films deposited using an Ar-ion beam showed a resistivity of approximately 600 mV cm and a density of 8.26 gycm. The step coverage measured at the same contact was approximately 40%. The resistivity 3 and density of the thermally-decomposed film were also measured for comparison and were found to be approximately 10 000 mV cm and 5.85 gycm , respectively. Finally, the diffusion barrier performance of 50 nm thick films against Cu was investigated 3 by X-ray diffractometry. The CuyN-or Ar-ion beam bombarded filmySi structures showed formation of h0-Cu Si after annealing 3 at 650 8C for 1 h, while Cuythermally-decomposed filmySi showed this only after annealing at 600 8C.

Fabrication of Silicon Nanopillar Teradot Arrays by Electron-Beam Patterning for Nanoimprint Molds

Small, 2008

... Jung-Sub Wi 1 ,; Hyo-Sung Lee 1 ,; Kipil Lim 1 ,; Sung-Wook Nam 1 ,; Hyun-Mi Kim 1 ,; Soo-Yeo... more

Study of growth behaviour and microstructure of epitaxially grown self-assembled Ge quantum dots on nanometer-scale patterned SiO2/Si(001) substrates

physica status solidi (b), 2009

Abstract The growth behaviour and microstructure of epitaxially grown self-assembled Ge quantum d... more

Origin of charge generation efficiency of metal oxide p-dopants in organic semiconductors

Organic Electronics, 2011

We report that the low charge generation efficiency of metal oxide dopants in organic semiconduct... more We report that the low charge generation efficiency of metal oxide dopants in organic semiconductor hosts is originated from the formation of dopant nanoclusters. Dopant nanoclusters of rhenium oxide (ReO 3) and molybdenum oxide (MoO 3) exhibit log-normal size distributions with an average radius of 0.7-1.4 nm and standard deviation of 1.5-2.6 nm, depending on the dopant and their concentration in 1,4-bis[N-(1-naphthyl)-N 0-phenylamino]-4,4 0 diamine (NPB). The number ratio of the nanoclusters to dopant molecules (dispersion efficiency) was measured to be 0.62-1.3% for the ReO 3-doped NPB. The low dispersion efficiency is close to the charge generation efficiency of 0.7-1.1%, which is defined as the ratio of generated carriers to dopant molecules, indicating that charge generation efficiency in the dopants is predominantly controlled by the dispersion of dopants in organic semiconductors.

Single-step formation of a graphene–metal hybrid transparent and electrically conductive film

Nanotechnology, 2012

We report here a rapid (10 s of heating) graphene growth method that can be carried out on any de... more We report here a rapid (10 s of heating) graphene growth method that can be carried out on any desired substrate, including an insulator, thus negating the need for the transfer from the metal substrate. This technique is based on metal-induced crystallization of amorphous carbon (a-C) to graphene, and involves an ultra-thin metal layer that is less than 10 nm in thickness. Rapid annealing of a bilayer of a-C and metal deposited on the surface leads to the formation of graphene film, and to subsequent breaking-up of the thin metal layer underneath the film, thus resulting in the formation of a graphene–metal hybrid film which is both transparent and electrically conducting. Based on Raman studies, we have also systematically compared ultra-thin metal-induced crystallization behavior with a case of conventional thick metal. Based on the present investigation, it was observed that the dominant growth mechanism in ultra-thin metal-induced crystallization is nucleation controlled.

Theoretical and experimental study of nanopore drilling by a focused electron beam in transmission electron microscopy

Nanotechnology, 2011

Sub-10 nm nanopores drilled by a focused electron beam in a transmission electron microscope are ... more Sub-10 nm nanopores drilled by a focused electron beam in a transmission electron microscope are widely used in solid-state nanopore devices for DNA translocation. However, there still remains much controversy surrounding the drilling mechanism. In order to explain the drilling of nanopores by electrons, we undertook a theoretical consideration of the energy transfer from the fast electrons to the solid through such mechanisms as elastic and inelastic scattering. According to the calculations based on the scattering cross-section, the direct atomic displacement cross-section induced by elastic scattering increases with increasing incident electron energy, while the ionization cross-section and temperature increment decrease. We performed nanopore drilling in a Si3N4 membrane using two different electron energies, 200 and 300 kV, to identify the drilling mechanism. The dependence of the nanopore drilling on the incident electron energy was well matched with the direct atomic displacement.

Sub-10-nm Nanochannels by Self-Sealing and Self-Limiting Atomic Layer Deposition

Nano Letters, 2010

Contrast enhancement behavior of hydrogen silsesquioxane in a salty developer

Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 2009

The authors investigated a contrast enhancement behavior of hydrogen silsesquioxane ͑HSQ͒ in a sa... more The authors investigated a contrast enhancement behavior of hydrogen silsesquioxane ͑HSQ͒ in a salty development system ͑NaOH / NaCl͒. Time-resolved analysis of contrast curves and line-grating patterns were carried out to investigate the unique properties of a salty development process. In NaOH developer without salt, the development process was saturated beyond a certain development time. On the other hand, the addition of salt enabled a continuous development, which was not observed in the pure NaOH development. The continuous thinning process enhances the contrast of HSQ in the salty developer, which allows a fast collapsing behavior in HSQ line-grating patterns. During development process, salt seems to have the role of modifying HSQ by breaking network bonds preferentially, leading to a continuous development rate.

Method of improving the quality of nanopatterning in atomic image projection electron-beam lithography

Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 2009

... Hyun-Mi Kim, Min Hyun Lee, Hyo-Sung Lee, Jung-Sub Wi, Kipil Lim, Ki-Bum Kim. Abstract. ... Th... more

Two-step resist-development process of hydrogen silsesquioxane for high-density electron-beam nanopatterning

Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 2009

It is identified that the development of hydrogen-silsesquioxane resist after electron-beam expos... more It is identified that the development of hydrogen-silsesquioxane resist after electron-beam exposure, by using a 25% tetramethylammonium-hydroxide ͑TMAH͒ developer, almost stops after 1 min of development time and it severely limits the delineation of high-density nanometer-scale patterns. By using x-ray photoelectron spectroscopy, the authors identified that this development-stopping phenomenon is due to the formation of a siloxane-type bond structure which is insoluble to the TMAH developer. Here, the authors propose a two-step development method that involves the removal process of siloxane layer using a dilute hydrofluoric acid between development processes. This method successfully eliminates the insoluble layer, thus generating isolated high-density dot patterns with 25 nm pitch.

Fabrication of ultra-high-density nanodot array patterns (∼3 Tbits/in.2) using electron-beam lithography

Journal of Vacuum Science & Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phenomena, 2011

ABSTRACT The authors fabricated 15 nm pitch scale high-density dot patterns on a Si substrate usi... more ABSTRACT The authors fabricated 15 nm pitch scale high-density dot patterns on a Si substrate using a hydrogen silsesquioxane electron-beam (e-beam) resist, vacuum treatment as a prebake, and vertical sidewall etching. The e-beam lithography was performed at 100 keV. The dot density fabricated was close to 3 Tbits/in.,2 which is one of the highest density patterns reported thus far. The process window was quite wide and the result can be easily and routinely duplicated.

Resistive switching characteristics of maghemite nanoparticle assembly

Journal of Physics D: Applied Physics, 2011

The resistive switching characteristics of the assembly of maghemite (γ-Fe 2 O 3) nanoparticles h... more The resistive switching characteristics of the assembly of maghemite (γ-Fe 2 O 3) nanoparticles having a diameter of ∼10 nm were investigated in the structure of Al/γ-Fe 2 O 3 nanoparticle multilayer (∼300 nm thick)/Al-plate. The nanoparticle multilayer on Al plate was formed by repeating dip-coating processes. The multilevel (five states) resistive switching was observed with the resistance values ranging from ∼4.8 × 10 5 to 2.7 × 10 3 depending on the externally applied voltage. The multilevel switching is thought to originate from the repetitive and reversible formation and rupture of multiple conducting filaments. It demonstrates the potential application of the γ-Fe 2 O 3 nanoparticle assembly for resistive switching devices.

Self-Assembly of Colloidal <I>γ</I>-Fe<SUB>2</SUB>O<SUB>3</SUB> and FePt Nanoparticles on Carbon Nanotubes by Dip-Coating Process

Journal of Nanoscience and Nanotechnology, 2012

ABSTRACT The chemically synthesized colloidal γ-Fe2O3 and FePt nanoparticles (NPs), with the diam... more ABSTRACT The chemically synthesized colloidal γ-Fe2O3 and FePt nanoparticles (NPs), with the diameter of ∼10 nm and ∼4 nm, respectively, adsorbed and assembled on the surface of carbon nanotubes (CNTs) by dip-coating process, through van der Waals interaction between NP and CNT. Repeating the steps of dip-coating and removing the surfactants from NPs significantly increased the amount of NPs as forming multilayers on the CNT. In addition, the electrochemical activities of FePt/CNTs for methanol oxidation were investigated for the potential application as catalysts of direct methanol fuel cells.

Microstructural Evolution of MgB2 Layers Prepared by Post Annealing of Evaporated Boron and Co-Evaporated MgBx (x = 1.1~4.3) Films

Materials Science Forum, 2005

... Prepared by Post Annealing of Evaporated Boron and Co-evaporated MgB (x = 1,1-4.3) Films Ki-... more

RuO2 thin film fabrication with plasma-enhanced chemical vapor deposition

Thin Solid Films, 1999

The deposition of RuO2 thin films by plasma-enhanced chemical vapor deposition (PECVD) with ruthe... more

Identifying the Location of a Single Protein along the DNA Strand Using Solid-State Nanopores

ACS Nano, 2015

Solid-state nanopore has been widely studied as an effective tool to detect and analyze small bio... more Solid-state nanopore has been widely studied as an effective tool to detect and analyze small biomolecules, such as DNA, RNA, and proteins, at a single molecule level. In this study, we demonstrate a rapid identification of the location of zinc finger protein (ZFP), which is bound to a specific locus along the length of a double-stranded DNA (dsDNA) to a single protein resolution using a low noise solid-state nanopore. When ZFP labeled DNAs were driven through a nanopore by an externally applied electric field, characteristic ionic current signals arising from the passage of the DNA/ZFP complex and bare DNA were detected, which enabled us to identify the locations of ZFP binding site. We examined two DNAs with ZFP binding sites at different positions and found that the location of the additional current drop derived from the DNA/ZFP complex is well-matched with a theoretical one along the length of the DNA molecule. These results suggest that the protein binding site on DNA can be mapped or that genetic information can be read at a single molecule level using solid-state nanopores.

Fabrication and verification of DNA functionalized nanopore with gold layer embedded structure for bio-molecular sensing

2011 IEEE Nanotechnology Materials and Devices Conference, 2011

Solid-state nanopore has been attracted by its great potential for bio-molecular analysis. Nanopo... more Solid-state nanopore has been attracted by its great potential for bio-molecular analysis. Nanopore is considered as promising tools for label-free single-molecule detection. As one of the techniques of nanopores, chemically modified or functionalized nanopore is considered to be a great candidate for a bio-molecule sensor. In this work, gold layer embedded nanopore was used for specific functionalization, because Au layer

Multilayer diffusion barrier for copper metallization using a thin interlayer metal (M=Ru, Cr, and Zr) between two TiN films

Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 2003

A multilayer structure ͓TiN͑5 nm͒/interlayer metal͑2 nm͒/TiN͑5 nm͔͒ has been evaluated as a diffu... more A multilayer structure ͓TiN͑5 nm͒/interlayer metal͑2 nm͒/TiN͑5 nm͔͒ has been evaluated as a diffusion barrier between copper and silicon. Three metals (MϭRu, Cr, and Zr͒ were tested as interlayer materials for the multilayer diffusion barrier scheme, expecting that they will stuff the TiN grain boundaries by forming metal oxides therein. The diffusion barrier performance was found to be the best when the Zr was used as an interlayer material. X-ray diffractometry showed that the Zr interlayer diffusion barrier failed only after annealing at 800°C for 30 min due to the formation of copper silicide while the reference sample without a metal interlayer failed when annealed at 600°C. The insertion of Cr also was also found to enhance the diffusion barrier performance, whereas, Ru has little effect on the improvement of the barrier performance. High-resolution transmission electron microscopy and energy dispersive spectroscopy showed that Zr significantly diffused into TiN grain boundaries while Ru did not diffuse during annealing. An explanation of the variation of the diffusion barrier performance with the change of an interlayer metal is given in terms of Gibbs free energy change of the respective metal-oxide formation.

Metal-Induced Nickel Silicide Nanowire Growth Mechanism in the Solid State Reaction

MRS Proceedings, 2006

A unique nanowire growth was accomplished at 575 oC by the metal-induced growth (MIG). That is a ... more A unique nanowire growth was accomplished at 575 oC by the metal-induced growth (MIG). That is a spontaneous reaction between metal and Si. The deposited metal worked as a catalyst layer to grow nanowire in the solid-state. Various metals (Ni, Co, and Pd) were used in MIG nanowire fabrication and Ni-induced case was successful in demonstrating that metal species should be a dominant mover in nanowire growth. Transmission electron microscopy investigation was performed to observe the nanowire growth direction. The Ni to Si composition was studied by energy dispersive spectroscopy showing the Ni diffusion inside the nanowire as well as the Ni silicide layer. The practical application MIG nanowire was proven by fabricating nanoscale contacts.

A Low-Noise Solid-State Nanopore Platform Based on a Highly Insulating Substrate

Scientific Reports, 2014

A solid-state nanopore platform with a low noise level and sufficient sensitivity to discriminate... more A solid-state nanopore platform with a low noise level and sufficient sensitivity to discriminate single-strand DNA (ssDNA) homopolymers of poly-A 40 and poly-T 40 using ionic current blockade sensing is proposed and demonstrated. The key features of this platform are (a) highly insulating dielectric substrates that are used to mitigate the effect of parasitic capacitance elements, which decrease the ionic current RMS noise level to sub-10 pA and (b) ultra-thin silicon nitride membranes with a physical thickness of 5 nm (an effective thickness of 2.4 nm estimated from the ionic current) are used to maximize the signal-to-noise ratio and the spatial depth resolution. The utilization of an ultra-thin membrane and a nanopore diameter as small as 1.5 nm allow the successful discrimination of 40 nucleotide ssDNA poly-A 40 and poly-T 40. Overall, we demonstrate that this platform overcomes several critical limitations of solid-state nanopores and opens the door to a wide range of applications in single-molecule-based detection and analysis. N anopores have attracted considerable attention because of their potential applications in the detection and analysis of single biomolecules, such as DNA, RNA, and proteins 1-6. In particular, DNA sequencing has driven the technology forward due to its inherent sensitivity, high throughput, amplification-free sample preparation, and lack of labels 7-12. The sub-molecular details of an individual molecule can be gathered via recording modulations in the ionic current when a molecule passes through the nanopore under the effect of a voltage applied across the pore. A series of impressive developments has been made in the area of protein nanopores using either a-hemolysin 7-10 or MspA 11-13 as they possess a low noise level and guarantee the reliable formation of a small pore aperture (1.5 nm) and an extremely thin sensing zone of approximately 1 nm. Combining these advantages with a recently developed method for slowing down DNA translocation using phi29 polymerase enzymes 10,13 makes this platform quite promising. In contrast, the development of solid-state nanopores has been much slower and limited to merely detecting the translocation of DNA molecules, although solid-state nanopore platforms have obvious advantages over their biological counterpart such as high stability, an adjustable geometry, controllable surface properties, and the potential for integration into stand-alone devices 14-16. The reliable formation of small nanopores (, 2 nm in diameter), fabrication of an extremely thin sensing zone with a thickness comparable to the spacing of each nucleotide, decrease of the noise level, and control of the translocation speed that would guarantee sufficient time to sense each nucleotide are the few challenges that limit the performance of solid-state nanopores. Among these issues, the excess noise level in solid-state nanopores (a few tens of pA to 100 pA: ,10 times larger than that of protein counterparts 17-20) has been one of the key issues responsible for the degraded signal-to-noise ratio and temporal and spatial resolution. In particular, the elevated parasitic capacitance generates a high level of dielectric noise that prevents sampling at high bandwidths. To effectively reduce the dielectric noise, several methods have been adopted such as thick dielectric layer deposition underneath an active SiN x membrane 21-23 , PDMS sealing 22,24 , the utilization of glass nanopores 25,26 , and machining of solid-state nanopores between dielectric membranes 27. All these platforms have resulted in a significant reduction of the noise level followed by some ramifications such as the need for additional processing to insert a thick SiO 2 layer underneath the SiN x layer and the reduction of the SiN x (,80 nm) thickness to the scale of sub-10 nm. In addition, the manual coating of PDMS sacrifices accuracy and reproducibility; the fabrication of small

The effect of ion beam bombardment on the properties of Ta(C)N films deposited from pentakis-diethylamido-tantalum

Thin Solid Films, 2002

TaN or TaCN films were deposited using a single source, pentakis-diethylamido-tantalum as diffusi... more TaN or TaCN films were deposited using a single source, pentakis-diethylamido-tantalum as diffusion barrier for copper metallization. N-and Ar-ion beams with energy of 120 eV were used for bombarding the film during growth to improve the film quality. The films deposited using N-ion beam showed a resistivity of approximately 950 mV cm and a density of 7.65 gycm. 3 The use of the N-ion beam, however, drastically degraded the step coverage of the film (;5% at the 0.5 mm contact holes with aspect ratio of 3:1). On the other hand, the films deposited using an Ar-ion beam showed a resistivity of approximately 600 mV cm and a density of 8.26 gycm. The step coverage measured at the same contact was approximately 40%. The resistivity 3 and density of the thermally-decomposed film were also measured for comparison and were found to be approximately 10 000 mV cm and 5.85 gycm , respectively. Finally, the diffusion barrier performance of 50 nm thick films against Cu was investigated 3 by X-ray diffractometry. The CuyN-or Ar-ion beam bombarded filmySi structures showed formation of h0-Cu Si after annealing 3 at 650 8C for 1 h, while Cuythermally-decomposed filmySi showed this only after annealing at 600 8C.

Fabrication of Silicon Nanopillar Teradot Arrays by Electron-Beam Patterning for Nanoimprint Molds

Small, 2008

... Jung-Sub Wi 1 ,; Hyo-Sung Lee 1 ,; Kipil Lim 1 ,; Sung-Wook Nam 1 ,; Hyun-Mi Kim 1 ,; Soo-Yeo... more

Study of growth behaviour and microstructure of epitaxially grown self-assembled Ge quantum dots on nanometer-scale patterned SiO2/Si(001) substrates

physica status solidi (b), 2009

Abstract The growth behaviour and microstructure of epitaxially grown self-assembled Ge quantum d... more

Origin of charge generation efficiency of metal oxide p-dopants in organic semiconductors

Organic Electronics, 2011

We report that the low charge generation efficiency of metal oxide dopants in organic semiconduct... more We report that the low charge generation efficiency of metal oxide dopants in organic semiconductor hosts is originated from the formation of dopant nanoclusters. Dopant nanoclusters of rhenium oxide (ReO 3) and molybdenum oxide (MoO 3) exhibit log-normal size distributions with an average radius of 0.7-1.4 nm and standard deviation of 1.5-2.6 nm, depending on the dopant and their concentration in 1,4-bis[N-(1-naphthyl)-N 0-phenylamino]-4,4 0 diamine (NPB). The number ratio of the nanoclusters to dopant molecules (dispersion efficiency) was measured to be 0.62-1.3% for the ReO 3-doped NPB. The low dispersion efficiency is close to the charge generation efficiency of 0.7-1.1%, which is defined as the ratio of generated carriers to dopant molecules, indicating that charge generation efficiency in the dopants is predominantly controlled by the dispersion of dopants in organic semiconductors.

Single-step formation of a graphene–metal hybrid transparent and electrically conductive film

Nanotechnology, 2012

We report here a rapid (10 s of heating) graphene growth method that can be carried out on any de... more We report here a rapid (10 s of heating) graphene growth method that can be carried out on any desired substrate, including an insulator, thus negating the need for the transfer from the metal substrate. This technique is based on metal-induced crystallization of amorphous carbon (a-C) to graphene, and involves an ultra-thin metal layer that is less than 10 nm in thickness. Rapid annealing of a bilayer of a-C and metal deposited on the surface leads to the formation of graphene film, and to subsequent breaking-up of the thin metal layer underneath the film, thus resulting in the formation of a graphene–metal hybrid film which is both transparent and electrically conducting. Based on Raman studies, we have also systematically compared ultra-thin metal-induced crystallization behavior with a case of conventional thick metal. Based on the present investigation, it was observed that the dominant growth mechanism in ultra-thin metal-induced crystallization is nucleation controlled.

Theoretical and experimental study of nanopore drilling by a focused electron beam in transmission electron microscopy

Nanotechnology, 2011

Sub-10 nm nanopores drilled by a focused electron beam in a transmission electron microscope are ... more Sub-10 nm nanopores drilled by a focused electron beam in a transmission electron microscope are widely used in solid-state nanopore devices for DNA translocation. However, there still remains much controversy surrounding the drilling mechanism. In order to explain the drilling of nanopores by electrons, we undertook a theoretical consideration of the energy transfer from the fast electrons to the solid through such mechanisms as elastic and inelastic scattering. According to the calculations based on the scattering cross-section, the direct atomic displacement cross-section induced by elastic scattering increases with increasing incident electron energy, while the ionization cross-section and temperature increment decrease. We performed nanopore drilling in a Si3N4 membrane using two different electron energies, 200 and 300 kV, to identify the drilling mechanism. The dependence of the nanopore drilling on the incident electron energy was well matched with the direct atomic displacement.

Sub-10-nm Nanochannels by Self-Sealing and Self-Limiting Atomic Layer Deposition

Nano Letters, 2010

Contrast enhancement behavior of hydrogen silsesquioxane in a salty developer

Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 2009

The authors investigated a contrast enhancement behavior of hydrogen silsesquioxane ͑HSQ͒ in a sa... more The authors investigated a contrast enhancement behavior of hydrogen silsesquioxane ͑HSQ͒ in a salty development system ͑NaOH / NaCl͒. Time-resolved analysis of contrast curves and line-grating patterns were carried out to investigate the unique properties of a salty development process. In NaOH developer without salt, the development process was saturated beyond a certain development time. On the other hand, the addition of salt enabled a continuous development, which was not observed in the pure NaOH development. The continuous thinning process enhances the contrast of HSQ in the salty developer, which allows a fast collapsing behavior in HSQ line-grating patterns. During development process, salt seems to have the role of modifying HSQ by breaking network bonds preferentially, leading to a continuous development rate.

Method of improving the quality of nanopatterning in atomic image projection electron-beam lithography

Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 2009

... Hyun-Mi Kim, Min Hyun Lee, Hyo-Sung Lee, Jung-Sub Wi, Kipil Lim, Ki-Bum Kim. Abstract. ... Th... more

Two-step resist-development process of hydrogen silsesquioxane for high-density electron-beam nanopatterning

Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 2009

It is identified that the development of hydrogen-silsesquioxane resist after electron-beam expos... more It is identified that the development of hydrogen-silsesquioxane resist after electron-beam exposure, by using a 25% tetramethylammonium-hydroxide ͑TMAH͒ developer, almost stops after 1 min of development time and it severely limits the delineation of high-density nanometer-scale patterns. By using x-ray photoelectron spectroscopy, the authors identified that this development-stopping phenomenon is due to the formation of a siloxane-type bond structure which is insoluble to the TMAH developer. Here, the authors propose a two-step development method that involves the removal process of siloxane layer using a dilute hydrofluoric acid between development processes. This method successfully eliminates the insoluble layer, thus generating isolated high-density dot patterns with 25 nm pitch.

Fabrication of ultra-high-density nanodot array patterns (∼3 Tbits/in.2) using electron-beam lithography

Journal of Vacuum Science & Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phenomena, 2011

ABSTRACT The authors fabricated 15 nm pitch scale high-density dot patterns on a Si substrate usi... more ABSTRACT The authors fabricated 15 nm pitch scale high-density dot patterns on a Si substrate using a hydrogen silsesquioxane electron-beam (e-beam) resist, vacuum treatment as a prebake, and vertical sidewall etching. The e-beam lithography was performed at 100 keV. The dot density fabricated was close to 3 Tbits/in.,2 which is one of the highest density patterns reported thus far. The process window was quite wide and the result can be easily and routinely duplicated.

Resistive switching characteristics of maghemite nanoparticle assembly

Journal of Physics D: Applied Physics, 2011

The resistive switching characteristics of the assembly of maghemite (γ-Fe 2 O 3) nanoparticles h... more The resistive switching characteristics of the assembly of maghemite (γ-Fe 2 O 3) nanoparticles having a diameter of ∼10 nm were investigated in the structure of Al/γ-Fe 2 O 3 nanoparticle multilayer (∼300 nm thick)/Al-plate. The nanoparticle multilayer on Al plate was formed by repeating dip-coating processes. The multilevel (five states) resistive switching was observed with the resistance values ranging from ∼4.8 × 10 5 to 2.7 × 10 3 depending on the externally applied voltage. The multilevel switching is thought to originate from the repetitive and reversible formation and rupture of multiple conducting filaments. It demonstrates the potential application of the γ-Fe 2 O 3 nanoparticle assembly for resistive switching devices.

Self-Assembly of Colloidal <I>γ</I>-Fe<SUB>2</SUB>O<SUB>3</SUB> and FePt Nanoparticles on Carbon Nanotubes by Dip-Coating Process

Journal of Nanoscience and Nanotechnology, 2012

ABSTRACT The chemically synthesized colloidal γ-Fe2O3 and FePt nanoparticles (NPs), with the diam... more ABSTRACT The chemically synthesized colloidal γ-Fe2O3 and FePt nanoparticles (NPs), with the diameter of ∼10 nm and ∼4 nm, respectively, adsorbed and assembled on the surface of carbon nanotubes (CNTs) by dip-coating process, through van der Waals interaction between NP and CNT. Repeating the steps of dip-coating and removing the surfactants from NPs significantly increased the amount of NPs as forming multilayers on the CNT. In addition, the electrochemical activities of FePt/CNTs for methanol oxidation were investigated for the potential application as catalysts of direct methanol fuel cells.