• Proceedings of the KSME Conference
• /
• 2003.04a
• /
• pp.1052-1058
• /
• 2003

The possibility of micro/nano machining through electro-chemical process is discussed in this research. Electro-chemical dissolution region is localized within 1 ${\mu}m$ by applying ultra short pulses with tens of nanosecond duration. The effects of voltage, pulse duration, and pulse frequency on the localization distance are investigated. Localization distance can be manipulated by controlling the voltage and pulse duration, and various hole shapes are produced including stepped holes and taper free hole. High quality micro-hole with 8 ${\mu}m$ diameter with 20 ${\mu}m$ depth and micro-groove with 9 ${\mu}m$ width with 10 ${\mu}m$ depth are machined on 304 stainless steel.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2010.02a
• /
• pp.321-321
• /
• 2010

The PEDOT:PSS layer is usually used as hole transporting layer for the polymer bulk heterojunction solar cells. However, the interface between ITO and PEDOT:PSS is not stable and the chemical reaction between ITO and PEDOT can result in degraded device performance. We used the tungsten oxides as a hole transport layer by spin-coating. The $WO_3$ nanoparticles were well dispersed in ammonium hydroxide and deionized water and formed thin layer on the ITO anode. We found that $WO_3$ surface is more hydrophobic than the bare ITO or PEDOT:PSS-coated surfaces. The hydrophobic surfaces promote an ordered growth of P3HT films. A higher degree of P3HT ordering is expected to improve the hole mobility and the lifetime of the device using the tungsten oxide showed better stability compared to the device using the PEDOT:PSS.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2011.02a
• /
• pp.472-472
• /
• 2011

The capacitive coupled plasma (CCP) has been extensively used in the semiconductor industry because it has not only good uniformity, but also low electron temperature. But CCP source has some problems, such as difficulty in varying the ion bombardment energy separately, low plasma density, and high processing pressure, etc. In this reason, dual frequency CCP has been investigated with a separate substrate biasing to control the plasma parameters and to obtain high etch rate with high etch selectivity. Especially, in this study, we studied on the etching of $SiO_2$ by using the pulse-time modulation in the dual-frequency CCP source composed of 60 MHz/ 2 MHz rf power. By using the combination of high /low rf powers, the differences in the gas dissociation, plasma density, and etch characteristics were investigated. Also, as the size of the semiconductor device is decreased to nano-scale, the etching of contact hole which has nano-scale higher aspect ratio is required. For the nano-scale contact hole etching by using continuous plasma, several etch problems such as bowing, sidewall taper, twist, mask faceting, erosion, distortions etc. occurs. To resolve these problems, etching in low process pressure, more sidewall passivation by using fluorocarbon-based plasma with high carbon ratio, low temperature processing, charge effect breaking, power modulation are needed. Therefore, in this study, to resolve these problems, we used the pulse-time modulated dual-frequency CCP system. Pulse plasma is generated by periodical turning the RF power On and Off state. We measured the etch rate, etch selectivity and etch profile by using a step profilometer and SEM. Also the X-ray photoelectron spectroscopic analysis on the surfaces etched by different duty ratio conditions correlate with the results above.

• JSTS:Journal of Semiconductor Technology and Science
• /
• v.1 no.1
• /
• pp.40-49
• /
• 2001

We have developed a repeatable process of forming uniform, small-size and high-density self-assembled Si nano-crystals. The Si nano-crystals were fabricated in a conventional LPCVD (low pressure chemical vapor deposition) reactor at $620^{\circ}c$ for 15 sec. The nano-crystals were spherical shaped with about 4.5 nm in diameter and density of $5{\times}l0^{11}/$\textrm{cm}^2$. More uniform dots were fabricated on nitride film than on oxide film. To take advantage of the above-mentioned characteristics of nitride film while keeping the high interface quality between the tunneling dielectrics and the Si substrate, nitride-oxide tunneling dielectrics is proposed in n-channel device. For the first time, the single electron effect at room temperature, which shows a saturation of threshold voltage in a range of gate voltages with a periodicity of ${\Delta}Ｖ_{GS}\;{\approx}\;1.7{\;}V$, corresponding to single and multiple electron storage is reported. The feasibility of p-channel nano-crystal memory with thin oxide in direct tunneling regime is demonstrated. The programming mechanisms of p-channel nano-crystal memory were investigated by charge separation technique. For small gate programming voltage, hole tunneling component from inversion layer is dominant. However, valence band electron tunneling component from the valence band in the nano-crystal becomes dominant for large gate voltage. Finally, the comparison of retention between programmed holes and electrons shows that holes have longer retention time.

• 한국전산유체공학회:학술대회논문집
• /
• 2010.05a
• /
• pp.575-580
• /
• 2010

In this work, the electrophoretic motion of dsDNA molecule represented by a polymer through an artificial nano-pore in a membrane is simulated using the numerical method combining the lattice Boltzmann and Langevin molecular dynamic method. The polymer motion is represented by Langevin molecular dynamics technique while the fluid flow is taken into account by fluctuating lattice-Boltzmann method. The hydrodynamic interactions between the polymer and solvent in a confined space with a membrane having a hole are considered explicitly through the frictional and the random forces. The electric field intensity over the space is obtained from a finite difference method. Initially, the polymer is placed at one side of the space, and an electric field is applied to drive the polymer to the other side of the space through the nano-pore. In future, we plan to study the effect of the polymer size and the electric field on the electrophoretic velocity.

• Journal of the Optical Society of Korea
• /
• v.17 no.4
• /
• pp.300-304
• /
• 2013

Novel breakthrough random-hole optical fibers (RHOFs) are fabricated in a draw tower facility, by tapering an optical fiber preform packed with a silica powder mixture capable of producing air holes in situ at the high temperature of tens of hundreds in degrees Celsius. Structural and propagation characteristics of the porous RHOF are explained briefly. Experimental investigations of the invented RHOF are performed for pressure sensor applications. Remarkable results are obtained for the RHOF with desirable pressure sensitivity independent of temperature, as is required for harsh conditions as in oil reservoirs.

• Transactions of Materials Processing
• /
• v.14 no.5 s.77
• /
• pp.473-476
• /
• 2005

The demand of on-chip total analyzing system with MEMS (micro electro mechanical system) bio/chemical sensor is rapidly increasing. In on-chip total analyzing system, to detect the bio/chemical products with submicron feature size, a filtration system with nano-filter is required. One of the conventional methods to fabricate nano-filter is to use direct patterning or RIE (reactive ion etching). However, those procedures are very costly and are not suitable fur mass production. In this study, we suggested new fabrication method for a nano-filter based on replication process, which is simple and low cost process. After the Si master was fabricated by laser interference lithography and reactive ion etching process, the polymeric mold was replicated by UV-imprint process. Metallic nano-filter was fabricated after removing the polymeric part of metal deposited polymeric mold. Finally, our fabrication method was applied to metallic nano-filter with $1{\mu}m$ pitch size and $0.4{\mu}m$ hole size for bacteria sensor application.

• Journal of the Korean Society for Precision Engineering
• /
• v.22 no.9 s.174
• /
• pp.130-136
• /
• 2005

This paper presents an optimal design and the performance evaluation of two-axis nano positioning stage with round notched flexure hinges. A flexure hinge mechanism with round notched flexure hinges is to guide the linear motions of a moving plate in the nano positioning stage. A Min-Max algorithm is applied to the design of the flexure hinge mechanism for nano positioning stage. In the design process, the structure of the flexure hinge mechanism is fixed, then the radius of a round hole and the width of two round holes are chosen as design variables, and finally the do sign variables are calculated by the Min-Max algorithm. The machined flexure hinge mechanism, stack type PZTs for actuation and capacitance type displacement sensors for position measurement are assembled into the nano positioning stage. The experimental results of the manufactured nano positioning stage show the first modal resonance frequency of 197 Hz, the operating range of 40 um, and the resolution of 3 nm.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2012.02a
• /
• pp.252-252
• /
• 2012

It is widely accepted that short exciton diffusion lengths of organic semiconductors with respect to the film thickness limit the charge (hole and electron) separation before excitons recombination in organic photovoltaic (OPV) cells. Therefore the efficient absorption of incident light within the thin active organic layer is of great importance to improve the power conversion efficiency (PCE) of the cells. In this work, we fabricated 2-dimensionally (2D) nano-patterned poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOST:PSS) layers using capillary phenomenon and nano-imprinting technology at the scale of several hundred nanometers. This 2D nano-patterned PEDOT:PSS layer exerted photonic crystal effect such as redirection of light paths and variation of light intensity at specified wavelengths. It is also expected that the consequently alternated light pass lengths and intensities change the absorption properties of zinc phthalocyanine (ZnPc) thin films grown on top of the nano-patterned PEDOT:PSS layer. The influence of conductivity and thickness of the PEDOT:PSS layer on the absorption properties of ZnPc thin films were also investigated.

• Journal of Magnetics
• /
• v.12 no.4
• /
• pp.144-148
• /
• 2007

We report on the observation of p-type conductivity and ferromagnetism in diluted magnetic semiconductor $(Zn_{0.97}Mg_{0.01}Mn_{0.02})O:P$ films grown on $SiO_2/Si$ substrates by pulsed laser deposition. The p-type conduction with hole concentration over $10^{18}cm^{-3}$ is obtained by codoping of Mg and P followed by rapid thermal annealing in an $O_2$ atmosphere. Structural and compositional analyses for the p-type $(Zn_{0.97}Mg_{0.01}Mn_{0.02})O:P$ films annealed at $800^{\circ}C$ indicates that highly c-axis oriented homogeneous films were grown without any detectable formation of secondary phases. The films were found to be transparent in the visible range. The magnetic measurements clearly revealed an enhancement of room temperature ferromagnetism by p-type doping.