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RISS 인기검색어
- 검색키워드
- 저자 : Brian L. Wardle (검색결과 4 건)
- 무료
- 기관 내 무료
- 유료
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Catalytic synthesis of few-layer graphene on titania nanowires
Kudo, Akira,Jung, Sung Mi,Strano, Michael S.,Kong, Jing,Wardle, Brian L. Royal Society of Chemistry 2018 Nanoscale Vol.10 No.3
<P>Growth mechanisms of graphitic nanostructures on metal oxides by chemical vapor deposition (CVD) are observed at 750 °C, using titania nanowire aerogel (NWAG) as a three-dimensional substrate and without metal catalysts. We temporally observed catalytic transformation of amorphous carbon into few-layer graphene on the surface of 5-10 nm diameter titania nanowires. The graphitization spontaneously terminates when the titania nanowires are encapsulated by a shell of approximately three graphene layers. Extended CVD time beyond the termination point (>1125 seconds) yields only additional amorphous carbon deposits on top of the few-layer graphene. Furthermore, it was discovered that the islands of amorphous carbon do not graphitize unless they catalytically grow beyond a threshold size of 5-7 nm along the nanowire length, even after an extended thermal treatment. The electrical conductivity of the NWAG increased by four orders of magnitude, indicating that the graphene shell mediated by titania nanowires yielded a network of graphene throughout the three-dimensional nanostructure of the aerogel. Our results help us understand the growth mechanisms of few-layer graphene on nanostructured metal oxides, and inspire facile and controllable processing of metal oxide-nanocarbon fiber-shell composites.</P>
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High Dielectric PLZT Thin Films for Embedded Capacitors
김승현,C. Y. Koo,J.-H. Cheon,J. Ha,J.-W. Lee,I.-H. Lee,W. S. Kim,Brian L. Wardle 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.54 No.2
For realization of next-generation embedded capacitors in high-density printed circuit boards, a high capacitance density and a low loss of capacitor films are needed. To make reliable capaci- tors, we performed a systematic investigation of the dielectric and the ferroelectric properties of (Pb,La)(Zr,Ti)O3 (PLZT) lms with a LaNiO3 (LNO) buffer layer deposited by a chemical solu- tion deposition method for the rhombohedral (La/Zr/Ti = 7/62/38) composition. The films with a LNO buffer layer on Ni-plated Cu foils showed a very dense and uniform microstructure. The PLZT films were found to a reduced hysteretic behavior, unlike general ferroelectric PZT films. The addition of a high concentration of a La dopant, such as 7 mol%, led to almost no or negligible hysteresis and a low coercive voltage, implying that PLZT with a high concentration of La dopant is a good candidate material for embedded capacitor applications. The capacitance values measured in this experiment were approximately 8 times higher than those of undoped PZT on conventional Ni-plated Cu foils. The capacitance density of the films was approximately 2.4 uF/cm2 and the loss tangent was below 1 %. The results show that PLZT films with an appropriate buffer layer, such as LNO, are strong candidates for high-performance embedded capacitors, providing a possibility of realizing next-generation embedded capacitors with ultra-high capacitance in printed circuit boards. For realization of next-generation embedded capacitors in high-density printed circuit boards, a high capacitance density and a low loss of capacitor films are needed. To make reliable capaci- tors, we performed a systematic investigation of the dielectric and the ferroelectric properties of (Pb,La)(Zr,Ti)O3 (PLZT) lms with a LaNiO3 (LNO) buffer layer deposited by a chemical solu- tion deposition method for the rhombohedral (La/Zr/Ti = 7/62/38) composition. The films with a LNO buffer layer on Ni-plated Cu foils showed a very dense and uniform microstructure. The PLZT films were found to a reduced hysteretic behavior, unlike general ferroelectric PZT films. The addition of a high concentration of a La dopant, such as 7 mol%, led to almost no or negligible hysteresis and a low coercive voltage, implying that PLZT with a high concentration of La dopant is a good candidate material for embedded capacitor applications. The capacitance values measured in this experiment were approximately 8 times higher than those of undoped PZT on conventional Ni-plated Cu foils. The capacitance density of the films was approximately 2.4 uF/cm2 and the loss tangent was below 1 %. The results show that PLZT films with an appropriate buffer layer, such as LNO, are strong candidates for high-performance embedded capacitors, providing a possibility of realizing next-generation embedded capacitors with ultra-high capacitance in printed circuit boards.
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