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Theoretical analysis for quantitative evaluation of in-situ nanoparticle measurement probability.
Mun, Jihun,Kim, Dongbin,Shin, Yong-Hyeon,Kang, Sang-Woo,Kim, Taesung American Scientific Publishers 2014 Journal of nanoscience and nanotechnology Vol.14 No.12
<P>A probability equation based on the proper assumptions of the particle trajectory and fundamental physics has been developed by analyze beam properties such as beam width and intensity distribution for an in situ particle monitor (ISPM). The radius coordinate which has the same intensity and portion of beam area for detection voltage range were analyzed to calculate particle measurement probability. The particle measurement probability is defined at a ratio of entire beam area to specified beam area which decided by detection voltage range. A probability measurement, given as a function of the detection voltage range, was performed 5 times using 200, 300, 500, 700 nm polystyrene latex standard particles at a pressure of 100 Torr with an in-house ISPM. The theoretical calculation results show good agreement with the experimental results and the maximum error is 20% by calculating probability differences between theoretical and experimental values. A calibration method based on the proposed probability equation enables to developed and increase accuracy of ISPM.</P>
진공공정에서의 오염입자 실시간 모니터링을 위한 광학식 센서 개발
문지훈(Jihun Mun),강상우(Sang-Woo Kang) 한국진공학회 2020 진공 이야기 Vol.7 No.1
In the past several decades, production yield and quality of the semiconductor and display process has successfully managed by introducing the advanced process control (APC) system. However, the recent technology evolution which represented as large-scale and high-density integration requires the much complicate and precise analysis of the processes for the breakthrough increasing of production yield. In this reason, the demand of developing novel real-time process monitoring sensor is increasing. We developed novel optical sensor for the real-time monitoring of contamination particles in vacuum environment. The developed sensor showed higher measurement efficiency and the weaknesses of previously developed sensors were overcame by introducing the novel measurement methods.
Hierarchical, Dual-Scale Structures of Atomically Thin MoS<sub>2</sub> for Tunable Wetting
Choi, Jonghyun,Mun, Jihun,Wang, Michael Cai,Ashraf, Ali,Kang, Sang-Woo,Nam, SungWoo American Chemical Society 2017 NANO LETTERS Vol.17 No.3
<P>Molybdenum disulfide (MoS2), a well-known solid lubricant for low friction surface coatings, has recently drawn attention as an analogue two-dimensional (2D) material beyond graphene. When patterned to produce vertically grown, nanoflower-structures, MoS2 shows promise as a functional material for hydrogen evolution catalysis systems, electrodes for alkali metal-ion batteries, and field-emission arrays. Whereas the wettability of graphene has been substantially investigated, that of MoS, structures, especially nanoflowers, has remained relatively unexplored despite MoS2 nanoflower's potential in future applications. Here, we demonstrate that the wettability of MoS2 can be controlled by multiscale modulation of surface roughness through (1) tuning of the nanoflower structures by chemical vapor deposition synthesis and (2) tuning of microscale topography via mechanical strain. This multiscale modulation offers broadened tunability (80-155 degrees) compared to single-scale tuning (90-130 degrees). In addition, surface adhesion, determined from contact angle hysteresis (CAH), can also be tuned by multiscale surface roughness modulation, where the CAH is changed in range of 20-40 degrees Finally, the wettability of crumpled MoS, nanoflowers can be dynamically and reversibly controlled through applied strain (similar to 115-150 with 0-200% strain), and remains robust over 1000 strain cycles. These studies on the tunable wettability of MoS, will contribute to future MoS2-based applications, such as tunable wettability coatings for desalination and hydrogen evolution.</P>
Shahzad, Rauf,Kim, TaeWan,Mun, Jihun,Kang, Sang-Woo IOP Pub 2017 Nanotechnology Vol.28 No.50
<P>Two-dimensional (2D) copper chalcogenides (Cu<SUB>2−<I>x</I> </SUB> <I>X</I> where <I>X</I>?=?S, Se, Te) have had much attention regarding various applications due to their remarkable optical and electrical properties, abundance, and environmentally friendly natures. This work indicates that highly uniform Cu<SUB>2−<I>x</I> </SUB>S (where 0?<U><</U>?<I>x</I>?<U><</U>?1) nanosheets can be obtained by the two-step method of Cu deposition by sputtering with precisely controlled and extremely low growth rate followed by vapor-phase sulfurization. The phase transformations of thin Cu<SUB>2−<I>x</I> </SUB>S films upon the Cu seed layer thickness are investigated. A unique thickness-constrained synthesis process using vapor-phase sulfurization is employed here, which evolves from a vertical to lateral growth mechanism based on the optimization of the Cu seed layer thickness. Atomically thin 2D <I>β</I>-Cu<SUB>2</SUB>S film was successfully synthesized using the thinnest Cu seed film. We have systematically investigated the phase- and thickness-dependent optical properties of Cu<SUB>2−<I>x</I> </SUB>S films at room temperature. Micro-photoluminescence (PL) spectroscopy reveals that the 2D <I>β</I>-Cu<SUB>2</SUB>S film possesses a direct band gap with an energy of 1.1 eV while the PL intensities are greatly suppressed in the multilayer Cu<SUB>2−<I>x</I> </SUB>S (where 0?≤?<I>x</I>?<U><</U>?1).</P>
Joung, DaeHwa,Park, Hyeji,Mun, Jihun,Park, Jonghoo,Kang, Sang-Woo,Kim, TaeWan The Korean Vacuum Society 2017 Applied Science and Convergence Technology Vol.26 No.5
The two-dimensional layered $MoS_2$ has high mobility and excellent optical properties, and there has been much research on the methods for using this for next generation electronics. $MoS_2$ is similar to graphene in that there is comparatively weak bonding through Van der Waals covalent bonding in the substrate-$MoS_2$ and $MoS_2-MoS_2$ heteromaterial as well in the layer-by-layer structure. So, on the monatomic level, $MoS_2$ can easily be exfoliated physically or chemically. During the $MoS_2$ field-effect transistor fabrication process of photolithography, when using water, the water infiltrates into the substrate-$MoS_2$ gap, and leads to the problem of a rapid decline in the material's yield. To solve this problem, an epoxy-based, as opposed to a water-based photoresist, was used in the photolithography process. In this research, a hydrophobic $MoS_2$ field effect transistor (FET) was fabricated on a hydrophilic $SiO_2$ substrate via chemical vapor deposition CVD. To solve the problem of $MoS_2$ exfoliation that occurs in water-based photolithography, a PPMA sacrificial layer and SU-8 2002 were used, and a $MoS_2$ film FET was successfully created. To minimize Ohmic contact resistance, rapid thermal annealing was used, and then electronic properties were measured.