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Determination of the Minimum Detectability of Surface Plasmon Resonance Devices by Using the 3σ Rule
Park Woongkyu,남기인,Choi Soobong 한국물리학회 2020 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.76 No.11
Surface plasmon resonance (SPR) devices are known to be able to detect traces of chemicals and can, therefore, be applied to a variety of applications. However, in order to define the sensitivity of such a device, one must obtain its minimum detectability. Nevertheless, the standard way to define the lower limit of detectability of an SPR device has not yet been established. In this paper, we propose a method to define the minimum detectability of SPR devices based on the 3σ rule. We measured the response of an SPR device by varying the concentrations of a single neutral analyte (ethylene glycol in deionized water). Then, we successfully obtained its lower limit of detectability, based on the measured data and the 3σ rule. Our method provides a standardized way to easily evaluate the quality of SPR devices.
Terahertz time domain spectroscopy of GdBCO superconducting thin films
Ji, Gangseon,Park, Woongkyu,Lee, Hyoung-Taek,Song, Chang-Yun,Seo, Choongwon,Park, Minjo,Kang, Byeongwon,Kim, Kyungwan,Kim, Dai-Sik,Park, Hyeong-Ryeol The Korea Institute of Applied Superconductivity a 2019 한국초전도저온공학회논문지 Vol.21 No.1
We present terahertz optical properties of $GdBa_2Cu_3O_{7-x}$ (GdBCO) superconducting thin films. GdBCO films with a thickness of about 105 nm were grown on a $LaAlO_3$ (LAO) single crystal substrate using a conventional pulsed laser deposition (PLD) technique. Using an Ar ion milling system, the thickness of the GdBCO film was reduced to 58 nm, and its surface was also smoothened. Terahertz (THz) transmission spectra through two different GdBCO films are measured over the range between 0.2 and 1.5 THz using THz time domain spectroscopy. Interestingly, the THz transmission of the thinner GdBCO film has been increased to six times larger than that of the thicker one, while the thinner film is still maintaining its superconducting property at below 90 K.
Lee, Woongkyu,Jeon, Woojin,An, Cheol Hyun,Chung, Min Jung,Kim, Han Joon,Eom, Taeyong,George, Sheby Mary,Park, Bo Keun,Han, Jeong Hwan,Kim, Chang Gyoun,Chung, Taek-Mo,Lee, Sang Woon,Hwang, Cheol Seong American Chemical Society 2015 Chemistry of materials Vol.27 No.11
<P>An atomic layer deposition (ALD) process for SrTiO<SUB>3</SUB> (STO) thin film growth was developed using a newly designed and synthesized heteroleptic Sr-precursor, {Sr(demamp)(tmhd)}<SUB>2</SUB> (demampH = 1-{[2-(dimethylamino)ethyl](methyl)amino}-2-methylpropan-2-ol, tmhdH = 2,2,6,6-tetramethyl-3,5-heptanedione), which offered an intermediate reactivity toward oxygen between Sr(tmhd)<SUB>2</SUB> and Sr(<SUP>i</SUP>Pr<SUB>3</SUB>Cp)<SUB>2</SUB>. Because of the appropriate reactivity of {Sr(demamp)(tmhd)}<SUB>2</SUB> toward oxygen, the abnormal initial growth behavior (due to interaction between the Sr-precursor and active oxygen contained in the underlying oxidized Ru layer) became negligible during the growth of the SrO and STO films on the Ru electrode, which allowed the growth of the SrO and STO films to be highly controllable with a moderate growth rate. Using Ti(CpMe<SUB>5</SUB>)(OMe)<SUB>3</SUB> as the Ti-precursor and O<SUB>3</SUB> as the oxygen source in the TiO<SUB>2</SUB> ALD subcycle, the ALD process of the STO film revealed a growth rate of 0.05 nm/cycle and ∼85% of step coverage in terms of the thickness and cation composition on a capacitor hole structure with an aspect ratio of 10 (opening diameter of 100 nm and depth of 1 μm). The minimum achievable equivalent oxide thickness (<I>t</I><SUB>ox</SUB>) with a low leakage current (<10<SUP>–7</SUP> A/cm<SUP>2</SUP> at 0.8 V) was limited to 0.46 nm. The damage effect on the underlying Ru electrode by the prolonged ALD process time appears to affect the limited scalability of <I>t</I><SUB>ox</SUB>.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/cmatex/2015/cmatex.2015.27.issue-11/acs.chemmater.5b00843/production/images/medium/cm-2015-008439_0013.gif'></P>
인터넷 개별구매와 비교한 인터넷 공동구매의 상대적 장점과 단점에 대한 소비자들의 지각
이웅규,박준철 한국경영과학회 2003 韓國經營科學會誌 Vol.28 No.1
Group buying is one of the most popular transaction patterns on the internet at least in Korea. Nevertheless, it is hard to find academic researches for it in view of consumer behavior. In this paper, we analyze factors which determine consumer's attitude toward and intention of participation in internet group buying by comparison of internet individual one. For this purpose, we propose "lowering price", "decreasing risk" and "reducing transaction cost" as relative advantages and "lack of product assortment" and "delay of time" as relative disadvantages over individual buying on the internet. For empirical test, internet users who have some experiences of individual buying but not group ones on the internet are surveyed and analyzed. In result, a satisfying model fitness for structural equation model is derived and most hypotheses except the relationship between "decreasing risk" and "attitude toward internet group buying" are accepted. Our results provide not only academic contribution by suggestion of a research framework but also practical insight by discussion of divers features in internet group buying.
High-precision white light interferometry based on a color CCD and peak matching algorithm
Im Jaeseung,Kim Hyuntae,Park Woongkyu,Ahn Jae Sung,Lee Byeongil,Choi Soobong 한국물리학회 2022 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.80 No.7
White light interferometry (WLI) is a widely used technique in various research fields because it can quickly measure the topography of a sample over a large area. In conventional WLI, the topography of the sample is generally obtained by using the envelope of the interferogram. However, this method cannot determine the precise order of the fringes because it is very sensitive to longitudinal chromatic aberration which may cause several measurement errors. Here, we propose an algorithm for avoiding errors in the measurement of the sample’s topography. The concept of the peak matching algorithm and the development of a new scheme of acquiring the topography of the sample by using a color charge-coupled device (CCD) is proposed. We demonstrate that our method can reject the fringe distortion problem encountered when using a conventional WLI system to measure the discrete sample surface. We expect our method to be applied to a variety of research and in industrial fields that require precise topographic measurements.
Kim Hyuntae,Choi Soobong,Park Woongkyu,Cho Sangjoon,Kim Cheolsu 한국물리학회 2020 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.77 No.10
In this paper, we report that the beam profile of the near-infrared light from superluminescent diodes (SLDs) can be measured with a resolution below the diffraction limit by using the photothermal effect and scanning thermal microscopy (SThM). Due to the sub-diffraction resolution of SThM, the beam profile measured using SThM was much clearer than the beam profile obtained by using the knife-edge method. By stacking cross-sectional images of the optical beam profile obtained by using SThM, we were able to obtain successively the three-dimensional optical beam profile. Our novel method of using small probes to measure optical beam profiles is compatible with conventional microscopy systems and can potentially be used in various applications.
Terahertz time domain spectroscopy of GdBCO superconducting thin films
박형렬,Gangseon Ji,Woongkyu Park,이형택,Chang-Yun Song,서충원,Minjo Park,Byeongwon Kang,Kyungwan Kim,김대식 한국초전도.저온공학회 2019 한국초전도저온공학회논문지 Vol.21 No.1
We present terahertz optical properties of GdBa2Cu3O7-x (GdBCO) superconducting thin films. GdBCO films with a thickness of about 105 nm were grown on a LaAlO3 (LAO) single crystal substrate using a conventional pulsed laser deposition (PLD) technique. Using an Ar ion milling system, the thickness of the GdBCO film was reduced to 58 nm, and its surface was also smoothened. Terahertz (THz) transmission spectra through two different GdBCO films are measured over the range between 0.2 and 1.5 THz using THz time domain spectroscopy. Interestingly, the THz transmission of the thinner GdBCO film has been increased to six times larger than that of the thicker one, while the thinner film is still maintaining its superconducting property at below 90 K.