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Laser-Induced Solid-Phase Doped Graphene
Choi, Insung,Jeong, Hu Young,Jung, Dae Yool,Byun, Myunghwan,Choi, Choon-Gi,Hong, Byung Hee,Choi, Sung-Yool,Lee, Keon Jae American Chemical Society 2014 ACS NANO Vol.8 No.8
<P>There have been numerous efforts to improve the performance of graphene-based electronic devices by chemical doping. Most studies have focused on gas-phase doping with chemical vapor deposition. However, that requires a complicated transfer process that causes undesired doping and defects by residual polymers. Here, we report a solid-phase synthesis of doped graphene by means of silicon carbide (SiC) substrate including a dopant source driven by pulsed laser irradiation. This method provides <I>in situ</I> direct growth of doped graphene on an insulating SiC substrate without a transfer step. A numerical simulation on the temperature history of the SiC surface during laser irradiation reveals that the surface temperature of SiC can be accurately controlled to grow nitrogen-doped graphene from the thermal decomposition of nitrogen-doped SiC. Laser-induced solid-phase doped graphene is highly promising for the realization of graphene-based nanoelectronics with desired functionalities.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2014/ancac3.2014.8.issue-8/nn5032214/production/images/medium/nn-2014-032214_0005.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn5032214'>ACS Electronic Supporting Info</A></P>
( Sang Yool Park ),( Jung Sik Choi ),( Sang Young Seol ),( Youn Jae Lee ),( Sam Ryong Jee ),( Sung Jae Park ),( Ji Hyun Kim ),( Sang Heon Lee ),( Eun Uk Jung ) 대한내과학회 2014 대한내과학회 추계학술대회 Vol.2014 No.1
Background: Pancreatic fi uid collections(PFC) may occur as a result of acute or chronic pancreatitis and can develop secondary to fi uid leakage or liquefaction of pancreatic necrosis. Methods: We collected data from 116 consecutive patients with PFC in acute severe pancreatitis and chronic pancreatitis, from January 2009 to June 2014, treated at a single center. Collection characteristics, drainage technique, and outcomes were obtained through chart review. Conservative treatments comprised of prophylactic antibiotics coverage, fi uid resuscitation, nutritional support including nasojejunal tube feeding. Results: A total of 116 patients presented with fi uid collections classifi ed as acute peripancreatic fiuid collection(n=20), acute necrotic collection(n=15), pseudocyst(n=56), and walled-off necrosis(n=25). The etiology of PFC was alcoholic in 86(74. 1%), biliary in 9(7. 8%), post-ERCP in 5(4. 3%), other in 5(4. 3%), and idiopathic in 11 patients(9. 5%). Primary catheter drainage intervention for PFC was performed in 30 patients(25. 9%); The drainage technique was percutaneous drainage in 15 patients, transmural in 12, both in 2, and transpapillary in 1. Transpapillary pancreatic duct stents bridging the leak was successfully deployed in 24 patients(20. 7%). 75 patients(64. 6%) were successfully managed without any intervention or drainage procedure. Surgical management was necessary in 6 patients(5. 1%). Reasons for surgical management in 6 patients were transverse colon fistula in 2, persistence of PFC with suspicion of pancreatic malignancy in 4 patients. The success rate of conservative treatment and Minimally Invasive treatment group was 85. 3%(64/75) and 70. 7%(29/41). Overall mortality was 2%(n=3). Conclusions: Approximately 65% of patients with PFC can be treated without an intervention and with low mortality. The study indicates that conservative approach can be preferred in terms of treating patients with PFC to the direct catheter drainage or surgical intervention due to the existence of highly responding patients to the elective procedures.
Two-dimensional sheet resistance model for polycrystalline graphene with overlapped grain boundaries
Min, Sung Yoon,Cho, Changsoon,Shim, Gi Woong,Park, Ick-Joon,Jung, Dae Yool,Woo, Youngjun,Lee, Jung-Yong,Choi, Sung-Yool Elsevier 2018 Flatchem Vol.7 No.-
<P><B>Abstract</B></P> <P>Overlapped grain boundaries (OGBs) are an important feature of two-dimensional (2D) materials that are electrically, mechanically, and thermally different from conventional grain boundaries (CGBs). The properties of an individual OGB have been explored in some microscopic studies, but the effects of OGBs on the macroscopic properties of 2D materials such as sheet resistance and mobility have rarely been investigated. Therefore, it is necessary to identify and formulate the influence of the OGBs on the macroscopic properties of 2D materials.</P> <P>In this study, we propose a 2D sheet resistance and mobility model for polycrystalline graphene that considers the effects of OGBs and intra-grain defects. The proposed model is supported by a simulation of the growth and sheet resistance of graphene grown by chemical vapor deposition (CVD). The electrical properties were investigated with respect to the average grain size, and a threshold grain size for mobility saturation was introduced, which can provide directions for the growth of high-quality 2D materials for commercial use. Moreover, the 2D characteristics reflected in the model can explain the variation in the sheet resistance and mobility of graphene grown under the same conditions. Since this model is applicable to general 2D materials, it will provide guidelines for the growth of various 2D materials.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Two-dimensional sheet resistance and mobility equations for graphene are proposed. </LI> <LI> Overlapped grain boundaries prevent the increase of sheet resistance. </LI> <LI> Grain size distribution and grain arrangement can change the electrical properties. </LI> <LI> 2D materials exhibit a wider variation in sheet resistance than thin films. </LI> <LI> Threshold grain size at which mobility is saturated in 2D materials is suggested. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>