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Low specific contact resistance on epitaxial p-type 4H-SiC with a step-bunching surface

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Chinese Physics B 2015年第11期24卷 452-459页

作者：韩超张玉明宋庆文汤晓燕张义门郭辉王悦湖 School of Microelectronics Xidian University Key Laboratory of Wide Band Gap Semiconductor Materials and Devices School of Advanced Materials and Nanotechnology Xidian University

This paper reports the performances of Ti/Al based ohmic contacts fabricated on highly doped p-type 4H-SiC epitaxial layer which has a severe step-bunching surface. Different contact schemes are investigated based on the AI：Ti composition with no more than 50 at.% Al. The specific contact resistance （SCR） is obtained to be as low as 2.6 × 10-6Ωcm2 for the bilayered Ti（100 nm）/Al（100 nm） contact treated with 3 rain rapid thermal annealing （RTA） at 1000 ℃. The microstructure analyses examined by physical and chemical characterization techniques reveal an alloy-assisted ohmic contact formation mechanism, i.e., a high degree of alloying plays a decisive role in forming the interfacial ternary Ti3SiC2 dominating the ohmic behavior of the Ti/Al based contact. Furthermore, a globally covered Ti3 SiC2 layer with （0001）-oriented texture can be formed, regardless of the surface step bunching as well as its structural evolution during the metallization annealing.

关键词： 4H-SiC p-type ohmic contact alloying step bunching

Investigation of the 6H-SiC (0001) surface by AFM

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Journal of University of Science and Technology Beijing 2008年第5期15卷 654-658页

作者： Shouzhen Jiang Guangwei Yu Yingmin Wang Xiaobo Hu Xiangang Xu Minhua Jiang State Key Laboratory of Crystal Materials Shandong University Jinan 250100 China College of Physics and Electronics Shandong Normal University Jinan 250014 China

Micropipe and step structures on 6H-SiC （0001） surface were investigated by an atomic force microscopy （AFM）. On the facet,all micropipes examined are the origins of spiral steps,indicating that dislocations intersect the surface at these points. Micropipes are empty-core super-dislocations as originally described by Frank. The micropipe radius increases with the square of the dislocation Burgers vector. From the center to the periphery,step structures change with different surface inclinations. Regular step is observed within the central faceted area. step bunching and atomically rough surfaces are observed within the peripheral convex area. If the inclination with respect to the （0001） plane is large enough,step bunching of 15R-SiC can be observed.

关键词： atomic force microscopy micropipes step bunching polytypes

Direct observation of bunching of elementary steps on protein crystals under forced flow conditions

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Theoretical & Applied Mechanics Letters 2015年第4期5卷 173-176页

作者： Gen Sazaki Guoliang Dai Institute of Low Temperature Science Hokkaido University Key Laboratory of Microgravity Institute of Mechanics Chinese Academy of Sciences

bunching of elementary steps by solution flow is still not yet clarified for protein crystals. Hence, in this study, we observed elementary steps on crystal surfaces of model protein hen egg-white lysozyme （HEWL） under forced flow conditions, by our advanced optical microscopy. We found that in the case of a HEWL solution of 99.99% purity, forced flow changed bunched steps into elementary ones （debunching） on tetragonal HEWL crystals. In contrast, in the case of a HEWL solution of 98.5% purity, forced flow significantly induced bunching of elementary steps. These results indicate that in the case of HEWL crystals, the mass transfer of impurities is more significantly enhanced by forced solution flow than that of solute HEWL molecules. We also showed that forced flow induced the incorporation of microcrystals into a mother crystal and the subsequent formation of screw dislocations and spiral growth hillocks.

关键词： In situ observation step bunching step debunching Elementary steps Forced flow Protein crystal