반도체 박막의 표면조도의 측정

이내응 成均館大學校 科學技術硏究所 1998 論文集 Vol.49 No.2

Measurements of surface roughness become increasingly important as the electronic devices get smaller and require the control of interface structure in the atomic scale frequently. Therefore, the understanding of measurement techniques and roughening phenomena during semiconducting thin film materials processing is important in tailoring the morphologies of thin film interfaces. Quantitative measurements of thin film surface roughness can be achieved by atomic force microscopy (AFM) and/or transmission electron microscopy depending on the scale of roughness. During the deposition of group N and its alloys (Si, Ge, Si_(1-x)Ge_x) while surface roughness evolves kinetically at the low temperature far from the equilibrium, thermodynamic driving forces such as surface or strain energy reduction are dominant determining factors at the elevated growth temperatures.

직장암 수술 후 국소재발과 예후

김태윤,백무준,김성용,신응진,박내경,이문수,김창호,송옥평 순천향의학연구소 2004 Journal of Soonchunhyang Medical Science Vol.10 No.1

Locally recurrent rectal cancer is a difficult clinical problem. Local recurrence following treatment for rectal cancer is a major cause of morbidity and mortality. The reported range of local recurrence rates following surgical treatment for rectal cancer has varied from 4% to 50%. We retrospectively reviewed the charts of 142 rectal cancer patients from January 1991 to December 1999. Analysis of patients factors included age, gender, type of surgery, and adjuvant therapy. Tumors were assessed for level, stage, and grade. Local recurrence and distant metastases were also documented. Variables influencing local recurrence in this group were identified and disease-free survival is determined. Of the 142 patients(74 males, 68 females; mean age 62.6 years), 137 consecutive patients operated on for rectal cancer and followed up to December 2000 (range 23-118months) were analyzed. Local recurrence rate was 18.3%. Age and sex of patients, type of surgery, location of tumor in the rectum, size, morphology and grading of the tumor were all unrelated to the event under investigation. At Cox regression, the Dukes stage and the postoperative radiotherapy were the only independent prognostic factors for local recurrence, and Dukes stage (Hazard ratio=2.89, p<0.001) and local recurrence (Hazard ratio=3.31, p<0.01) were the only independent factors associated with improved survival.

A smartphone fluorescence imaging-based mobile biosensing system integrated with a passive fluidic control cartridge for minimal user intervention and high accuracy

Lee, Won-Il,Park, Younghyeon,Park, Jaemin,Shrivastava, Sajal,Son, Young-Min,Choi, Hak-Jong,Lee, Jaelin,Jeon, Byeungwoo,Lee, Heon,Lee, Nae-Eung The Royal Society of Chemistry 2019 Lab on a chip Vol.19 No.8

<P>A key challenge for realizing mobile device-based on-the-spot environmental biodetection is that a biosensor integrated with a fluid handling sensor cartridge must have acceptable accuracy comparable to that of conventional standard analytical methods. Furthermore, the user interface must be easy to operate, technologically plausible, and concise. Herein, we introduced an advanced smartphone imaging-based fluorescence microscope designed for Hg<SUP>2+</SUP> monitoring by utilizing a biosensor cartridge that reduced user intervention <I>via</I> time-sequenced passive fluid handling. The cartridge also employed a metal-nanostructured plastic substrate for complementing the fluorescence signal output; this helped the realization of high-accuracy detection, in which a ratiometric dual-wavelength detection method was applied. Using 30 samples of Hg<SUP>2+</SUP>-spiked wastewater, we showed that our device, which has a detection limit of ∼1 pM, can perform analytical assays accurately. The detection results from our method were in good linearity and agreement with those of conventional standard methods. We conclude that the integration of a simple-to-use biosensor cartridge, fluorescence signal-enhancing substrate, dual-wavelength detection, and quantitative image data processing on a smartphone has great potential to make any population accessible to small-molecule detection, which has been performed in centralized laboratories for environmental monitoring.</P>

Amine-modified single-walled carbon nanotubes protect neurons from injury in a rat stroke model

Lee, Hyun Jung,Park, Jiae,Yoon, Ok Ja,Kim, Hyun Woo,Lee, Do Yeon,Kim, Do Hee,Lee, Won Bok,Lee, Nae-Eung,Bonventre, Joseph V.,Kim, Sung Su Springer Science and Business Media LLC 2011 Nature nanotechnology Vol.6 No.2

<P>Stroke results in the disruption of tissue architecture and is the third leading cause of death in the United States. Transplanting scaffolds containing stem cells into the injured areas of the brain has been proposed as a treatment strategy, and carbon nanotubes show promise in this regard, with positive outcomes when used as scaffolds in neural cells and brain tissues. Here, we show that pretreating rats with amine-modified single-walled carbon nanotubes can protect neurons and enhance the recovery of behavioural functions in rats with induced stroke. Treated rats showed less tissue damage than controls and took longer to fall from a rotating rod, suggesting better motor functions after injury. Low levels of apoptotic, angiogenic and inflammation markers indicated that amine-modified single-walled carbon nanotubes protected the brains of treated rats from ischaemic injury.</P>

Hydrogen concentration and critical epitaxial thicknesses in low-temperature Si(001) layers grown by UHV ion-beam sputter deposition.

Lee, Nae-Eung The Korean Vacuum Society 1999 Journal of Korean Vacuum Science & Technology Vol.3 No.2

Hydrogen concentration depth profiles in homoepitaxial Si(001) films grown from hyper-thermal Si beams generated by ultrahigh vacuum (UHV) ion-beam sputtering have been measured by nuclear reaction analyses as a function of film growth temperature and deposition rate. Bulk H concentrations CH in the crystalline Si layers were found tio be below detection limits, 1${\times}$1019cm-3, with no indication of significant H surface segregation at the crystalline/amorphous interface region. This is quite different than the case for growth by molecular-beam epitaxy (MBE) where strong surface segregation was observed for similar deposition conditions with average CH values of 1${\times}$1020cm-3 in the amorphous overlayer. The markedly decreased H concentrations in the present experiments are due primarily to hydrogen desorption by incident hyperthermal Si atoms. Reduced H surface coverages during growth combined with collisionally-induced filling of interisland trenches and enhanced interlayer mass transport provide an increase in critical epitaxial thicknesses by up to an order of magnitude over previous MBE results.

Single-Chain Atomic Crystals as Extracellular Matrix-Mimicking Material with Exceptional Biocompatibility and Bioactivity

Lee, Jin Woong,Chae, Sudong,Oh, Seoungbae,Kim, Si Hyun,Choi, Kyung Hwan,Meeseepong, Montri,Chang, Jongwha,Kim, Namsoo,Yong Ho Kim,,Lee, Nae-Eung,Lee, Jung Heon,Choi, Jae-Young American Chemical Society 2018 NANO LETTERS Vol.18 No.12

<P>In this study, Mo<SUB>3</SUB>Se<SUB>3</SUB><SUP>-</SUP> single-chain atomic crystals (SCACs) with atomically small chain diameters of ∼0.6 nm, large surface areas, and mechanical flexibility were synthesized and investigated as an extracellular matrix (ECM)-mimicking scaffold material for tissue engineering applications. The proliferation of L-929 and MC3T3-E1 cell lines increased up to 268.4 ± 24.4% and 396.2 ± 8.1%, respectively, after 48 h of culturing with Mo<SUB>3</SUB>Se<SUB>3</SUB><SUP>-</SUP> SCACs. More importantly, this extremely high proliferation was observed when the cells were treated with 200 μg mL<SUP>-1</SUP> of Mo<SUB>3</SUB>Se<SUB>3</SUB><SUP>-</SUP> SCACs, which is above the cytotoxic concentration of most nanomaterials reported earlier. An ECM-mimicking scaffold film prepared by coating Mo<SUB>3</SUB>Se<SUB>3</SUB><SUP>-</SUP> SCACs on a glass substrate enabled the cells to adhere to the surface in a highly stretched manner at the initial stage of cell adhesion. Most cells cultured on the ECM-mimicking scaffold film remained alive; in contrast, a substantial number of cells cultured on glass substrates without the Mo<SUB>3</SUB>Se<SUB>3</SUB><SUP>-</SUP> SCAC coating did not survive. This work not only proves the exceptional biocompatible and bioactive characteristics of the Mo<SUB>3</SUB>Se<SUB>3</SUB><SUP>-</SUP> SCACs but also suggests that, as an ECM-mimicking scaffold material, Mo<SUB>3</SUB>Se<SUB>3</SUB><SUP>-</SUP> SCACs can overcome several critical limitations of most other nanomaterials.</P> [FIG OMISSION]</BR>

Highly sensitive stretchable transparent piezoelectric nanogenerators

Lee, Ju-Hyuck,Lee, Keun Young,Kumar, Brijesh,Tien, Nguyen Thanh,Lee, Nae-Eung,Kim, Sang-Woo The Royal Society of Chemistry 2013 Energy & environmental science Vol.6 No.1

<P>Here we report a new type of stretchable transparent piezoelectric nanogenerator (NG) using an organic piezoelectric material consisting of poly(vinylidene fluoride trifluoroethylene) [P(VDF-TrFE)] sandwiched with mobility-modified chemical vapor deposition-grown graphene electrodes by ferroelectric polarization into P(VDF-TrFE). This new type of NG has a very high sensitivity and mechanical durability with fully flexible, rollable, stretchable, foldable, and twistable properties. We also investigated the mobility-modified graphene electrodes with ferroelectric P(VDF-TrFE) remnant polarization, and a mechanism is proposed for switching the mobility of the carriers by the ferroelectric remnant polarization. Upon exposure to the same input sound pressure, the measured output performance of the stretchable NG with a thin polydimethylsiloxane stretchable rubber template is up to 30 times that of a normal NG with a plastic substrate. Upon exposure to an air flow at the same speed, the measured output voltage from the stretchable NG is about 8 times larger than that of the normal NG.</P> <P>Graphic Abstract</P><P>Highly sensitive stretchable transparent piezoelectric nanogenerators have been developed using P(VDF-TrFE) sandwiched with mobility-modified graphene electrodes. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c2ee23530g'> </P>

Neurite Outgrowth on Nanocomposite Scaffolds Synthesized from PLGA and Carboxylated Carbon Nanotubes

Lee, Hyun Jung,Yoon, Ok Ja,Kim, Do Hee,Jang, Yeong Mi,Kim, Hyun Woo,Lee, Won Bok,Lee, Nae-Eung,Kim, Sung Su WILEY-VCH Verlag 2009 Advanced engineering materials Vol.11 No.12

<P>Carbon nanotubes (CNTs) have been suggested as suitable materials for biomedical applications, especially in the neural area. It is essential not only to investigate the biocompatibility of CNTs with the neural system but also to determine proper methods for applying CNTs to neuronal growth. This work represents the first application of CNTs by electrospun poly(D,L-lactic-co-glycolic acid) (PLGA) scaffolds for a neural system. We synthesized electrospun nanocomposites of PLGA and single-walled carbon nanotubes functionalized by carboxylic acid groups (c-SWNTs), and investigated neurite outgrowth from SH-SY5Y cells on these nanocomposites as compared to that on fibrous PLGA alone. Cells on our PLGA/c-SWNT nanocomposite showed significantly enhanced mitochondrial function and neurite outgrowth compared to cells on PLGA alone. We concluded that c-SWNTs incorporated into fibrous PLGA scaffolds exerted a positive role on the health of neural cells.</P> <B>Graphic Abstract</B> <P>Carbon nanotubes (CNTs) have distinctive characteristics such as high conductivity which could help the promotion of neuronal function. Electrospun nanocomposites of poly(D,L-lactic-co-glycolic acid) (PLGA) and CNTs were synthesized, and neurite outgrowth and mitochondrial function of human neuroblastoma cells were investigated on these nanocomposites and compared with that on fibrous PLGA alone. The results showed that CNTs incorporated into fibrous PLGA scaffolds exerted a positive role on the health of neural cells. <img src='wiley_img_2010/14381656-2009-11-12-ADEM200900144-content.gif' alt='wiley_img_2010/14381656-2009-11-12-ADEM200900144-content'> </P>

Hydrogen concentration and critical epitaxial thicknesses in low - temperature Si(001) layers grown by UHV ion - beam sputter deposition

Nae-Eung Lee 한국진공학회(ASCT) 1999 Journal of Korean Vacuum Science & Technology Vol.3 No.2

Hydrogen concentration depth profiles in homoepitaxial Si(001) films grown from hyperthermal Si beams generated by ultrahigh vacuum (UHV) ion-beam sputtering have been measured by nuclear reaction analyses as a function of film growth temperature and deposition rate. Bulk H concentrations C_H in the crystalline Si layers were found to be below detection limits, ?l×10^(19) ㎝-³, with no indication of significant H surface segregation at the crystalline/amorphous interface region. This is quite different than the case for growth by molecular-beam epitaxy (MBE) where strong surface segregation was observed for similar deposition conditions with average C_H values of ?5x10^(19) ㎝-³ in the crystalline/amorphous interface region and ?10^(20) ㎝-³ in the amorphous overlayer. The markedly decreased H concentrations in the present experiments are due primarily to hydrogen desorption by incident hyperthermal Si atoms. Reduced H surface coverages during growth combined with collisionally-induced filling of interisland trenches and enhanced interlayer mass transport provide an increase in critical epitaxial thicknesses by up to an order of magnitude over previous MBE results.

Electrical properties of ionic field effect transistors using metal oxide layer as a dielectric material to application in solid-state biosensors

Kwangro Lee,Changho Ra,Sungwon Lee,A Ri Kim,Nae Eung Lee,Kyung Joon Han,Won Jong Yoo 한국진공학회 2019 한국진공학회 학술발표회초록집 Vol.2019 No.2