READER’S FORUM

Jungkil Lee,Ken Miyazawa,Masako Tabuchi,Takuma Sato,Misuzu Kawaguchi,Shigemi Goto 대한치과교정학회 2014 대한치과교정학회지 Vol.44 No.4

Effectiveness of en-masse retraction using midpalatal miniscrews and a modified transpalatal arch

Jungkil Lee,Ken Miyazawa,Masako Tabuchi,Takuma Sato,Misuzu Kawaguchi,Shigemi Goto 대한치과교정학회 2014 대한치과교정학회지 Vol.44 No.2

Objective: The purpose of this study was to compare the treatment duration and dentoskeletal changes between two different anchorage systems used to treat maxillary dentoalveolar protrusion and to examine the effectiveness of en-masse retraction using two miniscrews placed in the midpalatal suture. Methods: Fifty-seven patients (9 men, 48 women), who had undergone level anchorage system treatment at Aichi-Gakuin University Dental Hospital (Nagoya, Japan) were divided into two groups according to the method of maxillary posterior anchorage reinforcement: midpalatal miniscrews (25 patients, mean age 22 years) and conventional anchorage (32 patients, mean age 19 years). The en-masse retraction period, overall treatment duration, pre-treatment effective ANB angle, and change in the effective ANB angle were compared with an independent-samples t -test. Results: Compared to the headgear group, the duration of en-masse retraction was longer by approximately 4 months in the miniscrew group (p < 0.001). However, we found no significant difference in the total treatment duration between the groups. Moreover, a greater change in the effective ANB angle was observed in patients treated with miniscrews than in those treated with the conventional method (p < 0.05). Conclusions: The level anchorage system treatment using miniscrews placed in the midpalatal area will allow orthodontists more time to control the anterior teeth during enmasse retraction, without increasing the total treatment duration. Furthermore, it achieves better dentoskeletal control than does the conventional anchorage method, thereby improving the quality of the treatment results.

Photon-Triggered Current Generation in Chemically-Synthesized Silicon Nanowires

Kim, Jungkil,Kim, Ha-Reem,Lee, Hoo-Cheol,Kim, Kyoung-Ho,Hwang, Min-Soo,Lee, Jung Min,Jeong, Kwang-Yong,Park, Hong-Gyu American Chemical Society 2019 NANO LETTERS Vol.19 No.2

<P>A porous Si segment in a Si nanowire (NW), when exposed to light, generates a current with a high on/off ratio. This unique feature has been recently used to demonstrate photon-triggered NW devices including transistors, logic gates, and photodetection systems. Here, we develop a reliable and simple procedure to fabricate porous Si segments in chemically synthesized Si NWs for photon-triggered current generation. To achieve this, we employ 100 nm-diameter chemical-vapor-deposition grown Si NWs that possess an n-type high doping level and extremely smooth surface. The NW regions uncovered by electron-beam resist become selectively porous through metal-assisted chemical etching, using Ag nanoparticles as a catalyst. The contact electrodes are then fabricated on both ends of such NWs, and the generated current is measured when the laser is focused on the porous Si segment. The current level is changed by controlling the power of the incident laser and bias voltage. The on/off ratio is measured up to 1.5 × 10<SUP>4</SUP> at a forward bias of 5 V. In addition, we investigate the porous-length-dependent responsivity of the NW device with the porous Si segment. The responsivity is observed to decrease for porous segment lengths beyond 360 nm. Furthermore, we fabricate nine porous Si segments in a single Si NW and measure the identical photon-triggered current from each porous segment; this single NW device can function as a high-resolution photodetection system. Therefore, our fabrication method to precisely control the position and length of the porous Si segments opens up new possibilities for the practical implementation of programmable logic gates and ultrasensitive photodetectors.</P> [FIG OMISSION]</BR>

Photon-triggered nanowire transistors

Kim, Jungkil,Lee, Hoo-Cheol,Kim, Kyoung-Ho,Hwang, Min-Soo,Park, Jin-Sung,Lee, Jung Min,So, Jae-Pil,Choi, Jae-Hyuck,Kwon, Soon-Hong,Barrelet, Carl J.,Park, Hong-Gyu Nature Publishing Group, a division of Macmillan P 2017 Nature nanotechnology Vol.12 No.10

Photon-triggered electronic circuits have been a long-standing goal of photonics. Recent demonstrations include either all-optical transistors in which photons control other photons or phototransistors with the gate response tuned or enhanced by photons. However, only a few studies report on devices in which electronic currents are optically switched and amplified without an electrical gate. Here we show photon-triggered nanowire (NW) transistors, photon-triggered NW logic gates and a single NW photodetection system. NWs are synthesized with long crystalline silicon (CSi) segments connected by short porous silicon (PSi) segments. In a fabricated device, the electrical contacts on both ends of the NW are connected to a single PSi segment in the middle. Exposing the PSi segment to light triggers a current in the NW with a high on/off ratio of >8 × 10<SUP>6</SUP>. A device that contains two PSi segments along the NW can be triggered using two independent optical input signals. Using localized pump lasers, we demonstrate photon-triggered logic gates including AND, OR and NAND gates. A photon-triggered NW transistor of diameter 25 nm with a single 100 nm PSi segment requires less than 300 pW of power. Furthermore, we take advantage of the high photosensitivity and fabricate a submicrometre-resolution photodetection system. Photon-triggered transistors offer a new venue towards multifunctional device applications such as programmable logic elements and ultrasensitive photodetectors.

Si nanowires with porous segments for photon-triggered transistors

Kim, Jungkil,Lee, Hoo-Cheol,Kim, Ha-Reem,Lee, Hosung,Lee, Jung Min,Jeong, Kwang-Yong,Park, Hong-Gyu IOP 2019 Journal of Physics. D, Applied Physics Vol.52 No.37

<P>Optical triggering for current generation in a single Si nanowire embedded with porous segments is studied to demonstrate photon-triggered transistors with a high on–off ratio. The formation of multiple localized porous Si structures in a nanowire and their uniform and sensitive responses to light enable practical implementation of photonic devices such as photon-triggered logic gates and high-resolution photodetectors. This review introduces the recent progress on the photon-triggered nanowire transistors. First, it describes two methods to synthesize porous Si segments in a nanowire and analysis of their structural properties. Second, the review describes the experimental and theoretical characterizations of photon-triggered nanowire transistors. Third, it introduces the design and implementation of logic gates, including AND, OR, and NAND, and multi-pixel photodetectors using a single Si nanowire with two or more porous Si segments. This review suggests that an effective integration of photon-triggered transistors in a single nanowire can serve as a versatile platform for new multifunctional optoelectronic devices.</P>

Formation of three-dimensional GaAs microstructures by combination of wet and metal-assisted chemical etching : Formation of three-dimensional GaAs microstructures by combination of wet and metal-assisted chemical etching

Lee, A Ri,Kim, Jungkil,Choi, Suk-Ho,Shin, Jae Cheol Wiley (John WileySons) 2014 Physica Status Solidi. Rapid Research Letters Vol.8 No.4

Near-Ultraviolet-Sensitive Graphene/Porous Silicon Photodetectors

Kim, Jungkil,Joo, Soong Sin,Lee, Kyeong Won,Kim, Ju Hwan,Shin, Dong Hee,Kim, Sung,Choi, Suk-Ho American Chemical Society 2014 ACS APPLIED MATERIALS & INTERFACES Vol.6 No.23

<P>Porous silicon (PSi) is recognized as an attractive building block for photonic devices because of its novel properties including high ratio of surface to volume and high light absorption. We first report near-ultraviolet (UV)-sensitive graphene/PSi photodetectors (PDs) fabricated by utilizing graphene and PSi as a carrier collector and a photoexcitation layer, respectively. Thanks to high light absorption and enlarged energy-band gap of PSi, the responsivity (<I>R</I><SUB>i</SUB>) and quantum efficiency (QE) of the PDs are markedly enhanced in the near-UV range. The performances of PDs are systemically studied for various porosities of PSi, controlled by varying the electroless-deposition time (<I>t</I><SUB>d</SUB>) of Ag nanoparticles for the use of Si etching. Largest gain is obtained at <I>t</I><SUB>d</SUB> = 3 s, consistent with the maximal enhancement of <I>R</I><SUB>i</SUB> and QE in the near UV range, which originates from the well-defined interface at the graphene/PSi junction, as proved by atomic- and electrostatic-force microscopies. Optimized response speed is ∼10 times faster compared to graphene/single-crystalline Si PDs. These and other unique PD characteristics prove to be governed by typical Schottky diode-like transport of charge carriers at the graphene/PSi junctions, based on bias-dependent variations of the band profiles, resulting in novel dark- and photocurrent behaviors.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2014/aamick.2014.6.issue-23/am5053812/production/images/medium/am-2014-053812_0008.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am5053812'>ACS Electronic Supporting Info</A></P>

동해 항만에서 방파제 내 · 외측의 해양수질 오염 현황

최정길(Jungkil Choi),박종규(Jungkyu Park),이효진(Hyojin Lee),유현주(Hyunju Yoo) 한국해양환경·에너지학회 2020 한국해양환경·에너지학회 학술대회논문집 Vol.2020 No.11

Graphene-Assisted Chemical Etching of Silicon Using Anodic Aluminum Oxides as Patterning Templates

Kim, Jungkil,Lee, Dae Hun,Kim, Ju Hwan,Choi, Suk-Ho American Chemical Society 2015 ACS APPLIED MATERIALS & INTERFACES Vol.7 No.43

<P>We first report graphene-assisted chemical etching (GaCE) of silicon by using patterned graphene as an etching catalyst. Chemical-vapor-deposition-grown graphene transferred on a silicon substrate is patterned to a mesh with nanohole arrays by oxygen plasma etching using an anodic- aluminum-oxide etching mask. The prepared graphene mesh/silicon is immersed in a mixture solution of hydrofluoric acid and hydro peroxide with various molecular fractions at optimized temperatures. The silicon underneath graphene mesh is then selectively etched to form aligned nanopillar arrays. The morphology of the nanostructured silicon can be controlled to be smooth or porous depending on the etching conditions. The experimental results are systematically discussed based on possible mechanisms for GaCE of Si.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2015/aamick.2015.7.issue-43/acsami.5b07773/production/images/medium/am-2015-077734_0006.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am5b07773'>ACS Electronic Supporting Info</A></P>

Au/Ag Bilayered Metal Mesh as a Si Etching Catalyst for Controlled Fabrication of Si Nanowires

Kim, Jungkil,Han, Hee,Kim, Young Heon,Choi, Suk-Ho,Kim, Jae-Cheon,Lee, Woo American Chemical Society 2011 ACS NANO Vol.5 No.4

<P>Au/Ag bilayered metal mesh with arrays of nanoholes were devised as a catalyst for metal-assisted chemical etching of silicon. The present metal catalyst allows us not only to overcome drawbacks involved in conventional Ag-based etching processes, but also to fabricate extended arrays of silicon nanowires (SiNWs) with controlled dimension and density. We demonstrate that SiNWs with different morphologies and axial orientations can be prepared from silicon wafers of a given orientation by controlling the etching conditions. We explored a phenomenological model that explains the evolution of the morphology and axial crystal orientation of SiNWs within the framework of the reaction kinetics.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2011/ancac3.2011.5.issue-4/nn2003458/production/images/medium/nn-2011-003458_0006.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn2003458'>ACS Electronic Supporting Info</A></P>