= 아 래 =
1. 일 시 : 2013. 12. 10 (화), 16:00 ~
2. 장 소 : 응용공학동 1층 영상강의실
3. 연 사 : Prof. Nong-moon Hwang (Dept. of MSE, Seoul National University)
4. 제 목 : Growth of Thin Films and Nanostructures by Charged Nanoparticles: Non-Classical Crystallization
The theory of charged nanoparticles (TCN) suggests that many CVD and some PVD films and nanowires, which have been believed to grow by individual atoms or molecules, actually grow by the build block of charged nanoparticles generated in the gas phase during the process [1,2]. Based on the prediction by the TCN, the generation of charged nanoparticles was checked in many CVD systems and was confirmed without exception. The generation of charged nanoparticles was confirmed in the growth of diamond, Si, ZrO2, Si3N4, GaN films, ZnO, Si, GaN nanowires and carbon nanotubes. According to the TCN, the charged nanoparticles undergo epitaxial coalescence without leaving any void, indicating that the charge carried by nanoparticles should enhance the atomic diffusion. These unbelievable suggestions were experimentally confirmed recently by other groups through in-situ transmission electron microscopy (TEM) observation. Zheng et al.  and Yuk et al.  made in-situ TEM observation in the liquid cell showing that platinum crystals grow by the fusion or coalescence of platinum nanoparticles. Using a similar technique, Liao et al.  made in-situ TEM observation that Pt3Fe nanorods grow by the self-assembly and fusion of Pt3Fe nanoparticles. On the other hand, Zheng et al.  made in-situ TEM observation that the nanopore of 3.3 nm made in the magnesium sheet shrinks and disappears in less than 1 minute while observing by TEM with a defocused beam, indicating that the charges from the electron beam enhance atomic diffusion. The maximum temperature increase due to the electron beam was estimated to be less than 1 K. Although the non-classical crystallization has become a hot issue recently in the solution growth, not much attention is being paid to the growth of films and nanostructures in the vapor phase.