Papers by Author: C.K. Ong

Abstract: Mn-doped multiferroic BiFeO3 (BFMO) thin films were deposited on LaNiO3(LNO)/SrTiO3(STO)/Si(100) substrates by pulsed laser deposition (PLD) technique. X-ray diffraction (XRD) showed that films were bicrystalline single phase with (110) preferential orientation. Multiferroic top layer and oxide bottom electrode (LNO) epitaxially followed the buffer layer (STO). Oxygen partial pressure during deposition proved to be critical for phase formation, crystallinity and resistivity of the films. Atomic force microscopic (AFM) studies revealed the smooth, dense and crack free surfaces of the films. Cross-section view of the multilayers by field emission scanning electron microscope (FE-SEM) gave their thickness. Mn substitution resulted in the increase of magnetization saturation, coercive field and clarity of hysteresis loop. The magneto-electric (ME) effect was demonstrated by measuring the dielectric response in a varying magnetic field. Optimally deposited BFMO films show saturated P-E loop.

Abstract: The effects of oxygen (O2) reactive ion etching (RIE) on the field emission (FE) properties of aligned CuO nanowire films are investigated systematically. It is found that the FE performance of the films is largely enhanced after initial exposure to reactive oxygen ions but degrades after extended treatment. As comparison, Ar RIE is also used to treat CuO nanowires, which, however, results in the deterioration of FE properties. The enhanced FE after O2 RIE is attributed to the shaper morphology, cleaner surface and better conductivity. On the other hand, increased work function and non-crystallized surface structure cause the deterioration of FE of CuO nanowires after Ar RIE treatments.