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강버들,임아영,김영재,황의동,김선욱,김효송 Ewha Womans University School of Medicine 2013 EMJ (Ewha medical journal) Vol.36 No.S
Radiation recall dermatitis refers to an acute inflammatory reaction in a previously irradiated field triggered by the administration of certain drugs days to years after the exposure to radiation. Gefitinib is an epidermal growth factor receptor tyrosine kinase inhibitor and is an effective treatment for patients with advanced stage of non small cell lung cancer (NSCLC). Here, we report a rare case of gefitinib induced radiation recall dermatitis. A 52-year-old woman with a metastatic NSCLC had received a palliative radiation therapy of 20 cGy on spine metastasis area (C6-T6). After 24 days of receiving radiation therapy, she had started to take gefitinib. Eight months after taking drug, pain, swelling and erythema of skin were occurred on previously irradiated field. These symptoms were resolved after the cessation of gefitinib for 6 days and the topical use of steroid.
Reduced thermal resistance of heat sink using graphene oxide decorated with copper nanoparticles
Ryu, Beo Deul,Han, Min,Ko, Kang Bok,Lee, Kyu-Han,Cuong, Tran Viet,Han, Nam,Kim, Kyurin,Ryu, Jae Hyung,Park, Noh-Joon,Lim, Yongsu,Thanh, Do Trong,Jo, Chang Hee,Ju, Kwanseon,Hong, Chang-Hee Elsevier 2019 Materials research bulletin Vol.110 No.-
<P><B>Abstract</B></P> <P>Three–dimensional thermal interface materials made of graphene oxide (GO) and copper nanoparticles (Cu NPs) were applied for enhancing light–emitting diode heat dissipation. The effect of the stacking order of GO and Cu NPs on thermal resistance was explored by creating two types of samples: spray–coated with a mixed GO–Cu NPs and layer–by–layer stacked with GO/Cu NPs/GO. A reduction of thermal resistance for mixed GO–Cu NPs and layer–by–layer stacked structure by 37% and 33%, respectively, compared to that of Al heat sink. The lower thermal resistance of the mixed GO–Cu NPs sample is attributed to the fact that distributed Cu NPs at the step edge of GO sheets enhances the out–of–plane heat transfer at wrinkles/folds of GO interlayers. Therefore, a mixed GO–Cu NPs is considered as a promising composite for effective thermal management of high–performance optoelectronic devices.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Three–dimensional thermal interface materials made of graphene oxide and copper nanoparticles (GO–Cu NPs) have synthesized. </LI> <LI> The effect of the stacking order of GO–Cu NPs on thermal resistance has explored for enhancing LED heat dissipation. </LI> <LI> Analysis by a FLIR camera has showed that the combination of GO and Cu NPs enabled heat dissipation properties. </LI> <LI> The thermal resistance of the mixed GO–Cu NPs structure is less 37 % than that of the Al heat sink. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Ryu, Beo Deul,Han, Min,Han, Nam,Park, Young Jae,Ko, Kang Bok,Lim, Tae Hyun,Chandramohan, S.,Cuong, Tran Viet,Choi, Chel-Jong,Cho, Jaehee,Hong, Chang-Hee American Chemical Society 2014 ACS APPLIED MATERIALS & INTERFACES Vol.6 No.24
<P>A reduced graphene oxide (GO) layer was produced on undoped and n-type GaN, and its effect on the current- and heat-spreading properties of GaN-based light-emitting diodes (LEDs) was studied. The reduced GO inserted between metal electrode and GaN semiconductor acted as a conducting layer and enhanced lateral current flow in the device. Especially, introduction of the reduced GO layer on the n-type GaN improved the electrical performance of the device, relative to that of conventional LEDs, due to a decrease in the series resistance of the device. The enhanced current-spreading was further of benefit, giving the device a higher light output power and a lower junction temperature at high injection currents. These results therefore indicate that reduced GO can be a suitable current and heat-spreading layer for GaN-based LEDs.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2014/aamick.2014.6.issue-24/am506308t/production/images/medium/am-2014-06308t_0008.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am506308t'>ACS Electronic Supporting Info</A></P>
Chandramohan, S.,Kang, Ji Hye,Ryu, Beo Deul,Yang, Jong Han,Kim, Seongjun,Kim, Hynsoo,Park, Jong Bae,Kim, Taek Yong,Cho, Byung Jin,Suh, Eun-Kyung,Hong, Chang-Hee American Chemical Society 2013 ACS APPLIED MATERIALS & INTERFACES Vol.5 No.3
<P>This paper reports on the evaluation of the impact of introducing interlayers and postmetallization annealing on the graphene/p-GaN ohmic contact formation and performance of associated devices. Current–voltage characteristics of the graphene/p-GaN contacts with ultrathin Au, Ni, and NiO<SUB><I>x</I></SUB> interlayers were studied using transmission line model with circular contact geometry. Direct graphene/p-GaN interface was identified to be highly rectifying and postmetallization annealing improved the contact characteristics as a result of improved adhesion between the graphene and the p-GaN. Ohmic contact formation was realized when interlayer is introduced between the graphene and p-GaN followed by postmetallization annealing. Temperature-dependent <I>I</I>–<I>V</I> measurements revealed that the current transport was modified from thermionic field emission for the direct graphene/p-GaN contact to tunneling for the graphene/metal/p-GaN contacts. The tunneling mechanism results from the interfacial reactions that occur between the metal and p-GaN during the postmetallization annealing. InGaN/GaN light-emitting diodes with NiO<SUB><I>x</I></SUB>/graphene current spreading electrode offered a forward voltage of 3.16 V comparable to that of its Ni/Au counterpart, but ended up with relatively low light output power. X-ray photoelectron spectroscopy provided evidence for the occurrence of phase transformation in the graphene-encased NiO<SUB><I>x</I></SUB> during the postmetallization annealing. The observed low light output is therefore correlated to the phase change induced transmittance loss in the NiO<SUB><I>x</I></SUB>/graphene electrode. These findings provide new insights into the behavior of different interlayers under processing conditions that will be useful for the future development of opto-electronic devices with graphene-based electrodes.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2013/aamick.2013.5.issue-3/am3026079/production/images/medium/am-2012-026079_0006.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am3026079'>ACS Electronic Supporting Info</A></P>
Chandramohan, S.,Bok Ko, Kang,Han Yang, Jong,Deul Ryu, Beo,Katharria, Y. S.,Yong Kim, Taek,Jin Cho, Byung,Hong, Chang-Hee American Institute of Physics 2014 Journal of Applied Physics Vol.115 No.5
This study elucidates the correlation among conductivity of graphene and interface aspects in GaN light-emitting diodes (LEDs). Using a multilayer graphene of low sheet resistance, it is demonstrated that graphene alone can make ohmic contact with p-GaN without necessitating additional interlayer. Large-area blue LED with relatively low contact resistance in the order of 10(-2) ohm-cm(2) and improved forward voltage of 3.2 +/- 0.1 V was realized irrespective of the use of the interlayer. The results from parallel evaluation experiments performed by varying the layer numbers of graphene with ultrathin NiOx interlayer revealed that the poor lateral conductivity of monolayer or few layer graphene can be well compensated by the interlayer. A combination of three layer graphene and NiOx offered device with enhanced electro-optical performance. But the Schottky barrier associated with the inadequate adhesion of transferred graphene dominates all the benefits and becomes a major bottleneck preventing the formation of low resistance stable ohmic contact. (c) 2014 AIP Publishing LLC.
Han, Min,Ryu, Beo Deul,Ko, Kang Bok,Jo, Chang Hee,Lim, Chang-hyun,Cuong, Tran Viet,Han, Nam,Hong, Chang-Hee Elsevier 2019 Journal of crystal growth Vol.507 No.-
<P><B>Abstract</B></P> <P>Hexagonal boron nitride (hBN) combined with III-nitride materials is attracting increasing attention for widening the applications of III-nitride materials. Three methods were used to grow the hBN buffer layer: (i) 2-step (low and high temperature), (ii) 1-step (high temperature), and (iii) pre-TEB surface treatment method. The optical properties of the hBN buffer layers were determined through Raman spectroscopy and absorbance measurements to characterize the combination between the III-nitride material (AlN) and hBN. The crystal quality of the AlN film grown under the same conditions on three hBN buffer layers has investigated by X-ray diffraction (XRD). XRD data established that the surface roughness of the hBN layer and density of the AlN nuclei are important factors for crystal quality of III-nitride material. The surface roughness of the hBN layers varied for the different growth methods, while the V/III ratio for each method remained unchanged. This difference in the surface roughness was confirmed to be related to the bonding configuration within the hBN layer, and was further confirmed by X-ray photoelectron spectroscopy to be due to the strong interactions between BN with the substrate (B<SUB>1</SUB>). In addition, the strongly interacting BN bond, which is dependent on the method used for the growth of the buffer layer, resulted in a peel-off of the AlN layer. This phenomenon did not occur at the hBN/sapphire interface, but occurred at the AlN/hBN interface, confirming that the strong interaction bonding between BN and the substrate weakens adhesion at the AlN/hBN interface.</P> <P><B>Highlights</B></P> <P> <UL> <LI> AlN films grown on various hexagonal boron nitride buffer layer by MOCVD. </LI> <LI> The XPS results of BN impacts adhesion to the AlN template. </LI> <LI> Surface roughness of hexagonal boron nitride buffer significantly impacts the density of AlN nuclei. </LI> </UL> </P>