Dong-Kwon Lee

Charged nanoparticles in thin film and nanostructure growth by chemical vapour deposition

The critical role of charged nanoclusters and nanoparticles in the growth of thin films and nanostructures by chemical vapour deposition (CVD) is reviewed. Advanced nanoparticle detection techniques have shown that charged gas-phase nuclei tend to be formed under conventional processing conditions of thin films and nanostructures by thermal, hot-wire and plasma CVD. The relation between gas-phase nuclei and thin film and nanostructure growth has not been clearly understood. In this review it will be shown that many films and nanostructures, which have been believed to grow by individual atoms or molecules, actually grow by the building blocks of such charged nuclei. This new growth mechanism was revealed in an attempt to explain many puzzling phenomena involved in the gas-activated diamond CVD process. Therefore, detailed thermodynamic and kinetic analyses will be made to draw the conclusion that the well-known phenomenon of deposition of less stable diamond with simultaneous etching of stable graphite should be an indication of diamond growth exclusively by charged nuclei formed in the gas phase. A similar logic was applied to the phenomenon of simultaneous deposition and etching of silicon, which also leads to the conclusion that silicon films by CVD should grow mainly by the building blocks of charged nuclei. This new mechanism of crystal growth appears to be general in many CVD and some physical vapour deposition (PVD) processes. In plasma CVD, this new mechanism has already been utilized to open a new field of plasma-aided nanofabrication.

Suppressed magnetoelectric effect in epitaxially grown multiferroic Pb(Zr0.57Ti0.43)O3–Pb(Fe2/3W1/3)O3 solid-solution thin films

We report on the epitaxial growth of single-phase [Pb(Zr0.57Ti0.43)O3]0.8[Pb(Fe2/3W1/3)O3]0.2 (PZT–PFW) solid-solution thin films using pulsed laser deposition. X-ray diffraction measurements reveal that the films have a tetragonal structure. The films exhibit ferroelectric properties and weak ferromagnetic responses at room temperature. The magnetoelectric effects were investigated; the nonlinear magnetocapacitance coefficient, β33, was measured and found to be comparable to those of multiferroic hexagonal manganites, but at least two orders of magnitude smaller than that for polycrystalline PZT–PFW films.

Thermodynamics and Kinetics in the Synthesis of Monodisperse Nanoparticles

The preparation of monodisperse nanoparticles with uniform size, shape and composition has been intensively pursed because of their scientific and technological interests [1-4]. The major advantage of monodisperse particles may be attributed to the uniform properties of individual particles, which makes the property of whole particles strictly controllable. They have been widely used in industries such as pharmacy, catalysts, sensors, film precursors, and information storage. The property of nanoparticles is much more sensitive to their size than that of micro-particles. For example, the florescence of monodisperse CdSe/ZnS core/shell nanoparticles depends strongly on their size [5]. The superparamagnetism also depends strongly on the size of nanoparticles [6]. The properties of these particular size nanoparticles show great potentials in the field of bio-medicals and electronics.