Papers by Author: Dong Nyung Lee

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Authors: Kyung Keun Um, Hyo Tae Jeong, Sung Bo Lee, Dong Nyung Lee
Authors: Hyung Joon Shin, Seung Hyun Hong, Dong Nyung Lee
Authors: Dong Nyung Lee
Abstract: Vapor-, electro-, and electroless-deposits have usually strong fiber textures. When annealed, the deposits undergo recrystallization or abnormal grain growth to reduce their energy stored during deposition. The driving force for recrystallization is mainly caused by dislocations, whereas that for abnormal grain growth is due to the grain boundary, surface, interface, and strain energies. During recrystallization and abnormal grain growth, the texture change can take place. The recrystallization and abnormal grain growth textures are in general of fiber type. However, copper interconnects are subjected to non-planar stress state due to geometric constraints during room temperature and/or elevated temperature annealing. The annealing textures of the thin films and copper interconnects are discussed in terms of the minimization of the surface, interface, and strain energies, the grain boundary energy and mobility, and the strain-energy-release maximization.
Authors: Dong Nyung Lee
Abstract: Asymmetric rolling, in which the circumferential velocities of the upper and lower rolls are different, can give rise to intense plastic shear strains and in turn shear deformation textures through the sheet thickness. The ideal shear deformation texture of fcc metals can be approximated by the <111> // ND and {001}<110> orientations, among which the former improves the deep drawability. The ideal shear deformation texture for bcc metals can be approximated by the Goss {110}<001> and {112}<111> orientations, among which the former improves the magnetic permeability along the <100> directions and is the prime orientation in grain oriented silicon steels. The intense shear strains can result in the grain refinement and hence improve mechanical properties. Steel sheets, especially ferritic stainless steel sheets, and aluminum alloy sheets may exhibit an undesirable surface roughening known as ridging or roping, when elongated along RD and TD, respectively. The ridging or roping is caused by differently oriented colonies, which are resulted from the <100> oriented columnar structure in ingots or billets, especially for ferritic stainless steels, that is not easily destroyed by the conventional rolling. The breakdown of columnar structure and the grain refinement can be achieved by asymmetric rolling, resulting in a decrease in the ridging problem.
Authors: Dong Nyung Lee
Abstract: Park et al. measured the deposition and annealing textures of nanocrystalline Ni and Ni- 20 % Fe electrodeposits. They found that the deposition texture of major <100> + minor <111> changed to the texture characterized by major <111> + minor <100> after annealing. They also found that the lattice constants of the <100> oriented grains in the as-deposited state were larger than those of <111> oriented grains. In this paper, a model has been advanced to explain the unusual results of lattice constants, and the texture transition has been discussed.
Authors: Kyung Keun Um, Hyo Tae Jeong, Dong Nyung Lee
Authors: Sang Yum Kim, Chang Hee Choi, Dong Nyung Lee
Authors: Hyo Tae Jeong, Dong Nyung Lee, Kyu Hwan Oh
Authors: Dong Nyung Lee
Abstract: Amorphous Si films are generally deposited on glass by physical or chemical vapor deposition. When annealed, they undergo crystallization through nucleation and grain growth. At low annealing temperatures, crystallization starts near the glass substrates for pure Si films and near metals for metal-induced crystallization. In this case, crystallites grow along the <111> directions of c-Si nearly parallel to the film plane, that is, the directed crystallization. The directed crystallization is likely to develop the <110> or <111> orientation, which means the <110> or <111> directions are along the film thickness direction. As the annealing temperature increases, equiaxed crystallization tends to increase, which in turn increases random orientation. When the annealing temperature is further increased, the <111> orientation may be obtained.
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