• Applied Microscopy
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• v.45 no.3
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• pp.183-188
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• 2015

Due to the miniaturization of semiconductor devices, their crystal structure on the nanoscale must be analyzed. However, scanning electron microscope-electron backscatter diffraction (EBSD) has a limitation of resolution in nanoscale and high-resolution electron microscopy (HREM) can be used to analyze restrictive local structural information. In this study, three-dimensional (3D) automated crystal orientation and phase mapping using transmission electron microscopy (TEM) (3D TEM-EBSD) was used to identify the crystal structure relationship between an epitaxially grown CdS interfacial layer and a $Cu(In_xGa_{x-1})Se_2$ (CIGS) solar cell layer. The 3D TEM-EBSD technique clearly defined the crystal orientation and phase of the epitaxially grown layers, making it useful for establishing the growth mechanism of functional nano-materials.

• Journal of the Korean Society for Precision Engineering
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• v.33 no.4
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• pp.265-270
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• 2016

Recently, many studies have been conducted on the nano-scale fabrication technology using twophoton- absorbed polymerization induced by a femtosecond laser. The nano-stereolithography process has many advantages as a technique for direct fabrication of true three-dimensional shapes in the range over several microns with sub-100 nm resolution, which might be difficult to obtain by using general nano/microscale fabrication technologies. Therefore, two-photon induced nano-stereolithography has been recently recognized as a promising candidate technology to fabricate arbitrary 3D structures with sub-100 nm resolution. Many research works for fabricating novel 3D nano/micro devices using the two-photon nano-stereolithography process, which can be utilized in the NT/BT/IT fields, are rapidly advancing.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.2
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• pp.194-201
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• 2005

Nanoscale fabrication of silicon substrate in an aqueous solution based on the use of atomic force microscopy was demonstrated. A specially designed cantilever with diamond tip, allowing the formation of damaged layer on silicon substrate easily by a simple scratching process (Tribo-Nanolithography, TNL), has been applied instead of conventional silicon cantilever for scanning. A slant nanostructure can be fabricated by a process in which a thin damaged layer rapidly forms in the substrate at the diamond tip-sample junction along scanning path of the tip and simultaneously the area uncovered with the damaged layer is being etched. This study demonstrates how the TNL parameters can affect the formation of damaged layer and the shape of 3-D structure, hence introducing a new process of AFM-based nanolithography in aqueous solution.

• International Journal of Precision Engineering and Manufacturing
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• v.7 no.4
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• pp.8-13
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• 2006

Nanoscale fabrication of silicon substrate in an aqueous solution based on the use of atomic force microscopy was demonstrated. A specially designed cantilever with a diamond tip, allowing the formation of a mask layer on the silicon substrate by a simple scratching process (Tribo-Nanolithography, TNL), has been applied instead of the conventional silicon cantilever for scanning. A slant nanostructure can be fabricated by a process in which a thin mask layer rapidly forms on the substrate at the diamond tip-sample junction along scanning path of the tip, and simultaneously, the area uncovered with the mask layer is etched. This study demonstrates how the TNL parameters can affect the formation of the mask layer and the shape of 3-D structure, hence introducing a new process of AFM-based nanolithography in aqueous solution.

• Bulletin of the Korean Chemical Society
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• v.32 no.1
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• pp.277-280
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• 2011

We studied the relative stability and atomic structure of five $C_{20}^{2+}$ isomers obtained by two-electron ionization of a $C_{20}$ cage (the smallest fullerene). All the isomers are bond-stretch isomers, i.e., they differ in bond length. In particular, in one of the isomers with Ih symmetry, all the bond lengths are equal. Full geometry optimizations of the dipositive ion $C_{20}^{2+}$ were performed using the hybrid density functional (B3LYP/6-31G(d)) methods. All isomers were found to be true minima by frequency analysis at the level of B3LYP/6-31G(d) under the reinforced tight convergence criterion and a pruned (99,590) grid. The zero-point correction energy for the cage bond-stretch isomers was in the increasing order $D_{2h}<C_{2h}<C_2<T_h<I_h$ of $C_{20}^{2+}$. The energy difference among the isomers of cage dipositive ions was less than that among neutral cage isomers. Our results suggest that these isomers show bond-stretch isomerism and that they have an identical spin state and an identical potential energy curve. Although the predominant electronic configurations of the isomers are similar, the frontier orbital characteristics are different, implying that we could anticipate an entirely different set of characteristic chemical reactions for each type of HOMO and LUMO.

• Bulletin of the Korean Chemical Society
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• v.31 no.2
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• pp.457-460
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• 2010

The geometrical structures and energetics of positively doubly charged fullerene dimer $(C_{60})_2{^{2+}}$ conformers were studied using semiempirical PM3 and MNDO, Hartree-Fock (HF), and Hybrid B3LYP density functional methods. The shape of the HOMO-LUMO for the three conformers was also analyzed. The gauche conformer was the most stable of the three conformers. The anti conformer was more stable than the syn conformer.

• ETRI Journal
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• v.36 no.4
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• pp.643-653
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• 2014

To reduce interconnect delay and power consumption while improving chip performance, a three-dimensional integrated circuit (3D IC) has been developed with die-stacking and through-silicon via (TSV) techniques. The power supply problem is one of the essential challenges in 3D IC design because IR-drop caused by insufficient supply voltage in a 3D chip reduces the chip performance. In particular, power bumps and TSVs are placed to minimize IR-drop in a 3D power delivery network. In this paper, we propose a design methodology for 3D power delivery networks to minimize the number of power bumps and TSVs with optimum mesh structure and distribute voltage variation more uniformly by shifting the locations of power bumps and TSVs while satisfying IR-drop constraint. Simulation results show that our method can reduce the voltage variation by 29.7% on average while reducing the number of power bumps and TSVs by 76.2% and 15.4%, respectively.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.05a
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• pp.128-128
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• 2004

나노 스케일의 구조물 제작에 있어서 기존의 리소그래피 공정들이 가지는 한계점을 극복하기 위해서 다양한 방식의 새로운 공정들이 개발되고 있다. 특히, 기계-화학적 가공공정을 이용한 미세탐침 기반의 나노리소그래피 기술(Mechano-Chemical Scaning Probe based Lithography; MC-SPL)은 기존의 포토리소그래피 공정의 단점을 극복하고, 보다 경제적이며 패턴 디자인 변경이 유연한 미세 패턴 제작 기술임이 확인되었다.(중략)

• Transactions on Electrical and Electronic Materials
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• v.16 no.3
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• pp.156-161
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• 2015

In this paper, we present simulation results obtained using SILVACO TCAD tools for a 3-D silicon on insulator (SOI) n-FinFET structure with a gate length of 8 nm at 300K. The effects of variations of the device’s key electrical parameters, such as threshold voltage, subthreshold slope, transconductance, drain induced barrier lowering, oncurrent, leakage current and on/off current ratio are presented and analyzed. We will also describe some simulation results related to the influence of the gate work function variations on the considered structure. These variations have a direct impact on the electrical device characteristics. The results show that the threshold voltage decreases when we reduce the gate metal work function Φ_m. As a consequence, the behavior of the leakage current improves with increased Φ_m. Therefore, the short channel effects in real 3-D FinFET structures can reasonably be controlled and improved by proper adjustment of the gate metal work function.

• Bulletin of the Korean Chemical Society
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• v.30 no.2
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• pp.445-448
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• 2009

This study examined the effect of the uptake of one and two electrons on the atomic structure of three isomers of $C_{20}$ clusters, namely the ring, bowl (corannulene like), and cage (the smallest fullerene). Geometry optimizations were performed using the hybrid density functional (B3LYP) methods for neutral, singly and doubly charged $C_{20},\;{C_{20}}^-,and\;{C_{20}}^{2-}$. These results show that the symmetry of the lowest energies for ring and bowl isomers were not changed, whereas the increasing order of energy for the cage (the smallest fullerene) isomers was changed from $D_{2h}\;<\;C_{2h}\;{\leq}\;C_2\;of\;C_{20}\;through\;Ci\;<\;C_{2h}\;<\;C_2\;<\;D_{2h}\;of\;{C_{20}}^-\;to\;Ci\;<\;C_2\;<\;D_{2h}\;<\;C_{2h}\;of\;{C_{20}}^{2-}$. The reduced symmetry isomers of the cage have comparative energy and the ground state symmetry of the neutral and single and double charged $C_{20}$ decreased with increasing number of electrons taken up in the point of energetics. Interestingly, the difference in energy between the ground state and the next higher energy state of ${C_{20}}^{2-}$ was 3.5kcal/mol, which is the largest energy gap of the neutral, single anion and double anion of the cage isomers examined.