Si Nae Heo

Effect of solution concentration on the functional properties of ZnO nanostructures: Role of Hexamethylenetetramine

In this research, ZnO nanorods have been successfully synthesized via wet chemical method. XRD results revealed the single phase nature with the wurtzite structure of the as prepared ZnO nanorods. By only varying the concentration of Hexamethylenetetramine (HMT) in the solution, morphology of ZnO changed from hexagonal facet nanorods to pencil like nanorods and size of nanorods also changed. The band gap of as-synthesized ZnO nanorods was found to increase with increasing the concentration of HMT in the solution. The narrow full-width at half-maximum (FWHM) of the UV emission of PL spectra indicated that the grown ZnO nanorods have high crystal quality and is well matched with the obtained XRD results. These results revealed that the concentration of Hexamethylenetetramine plays a vital role to control the properties of ZnO nanorods.

Ta Doped SnO 2 Transparent Conducting Films Prepared by PLD

Transparent and conducting thin films of Ta-doped were fabricated on a glass substrate by a pulse laser deposition(PLD) method. The structural, optical, and electrical properties of these films were investigated as a function of doping level, oxygen partial pressure, substrate temperature, and film thickness. XRD results revealed that all the deposited films were polycrystalline and the intensity of the (211) plane of decreased with an increase of Ta content. However, the orientation of the films changed from (211) to (110) with an increase in oxygen partial pressure (40 to 100 mTorr) and substrate temperature. The crystallinity of the films also increased with the substrate temperature. The electrical resistivity measurements showed that the resistivity of the films decreased with an increase in Ta doping, which exhibited the lowest resistivity () for 10 wt% Ta-doped film, and then increased further. However, the resistivity continuously decreased with the oxygen partial pressure and substrate temperature. The optical bandgap of the 10 wt% Ta-doped film increased (3.67 to 3.78 eV) with an increase in film thickness from 100-700 nm, and the figure of merit revealed an increasing trend with the film thickness.

ZnO Nanorods on Polymer Substrate by Solution Method

In this research, ZnO nanorods were fabricated on the polymer substrate using a hydrothermal process. The grown nanorods were characterized by x-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and Raman measurements. ZnO nanorod arrays have been fabricated with diameter of 30-50 nm, and highly c-axis oriented with hexagonal wurtzite structure and perpendicular to the substrate with high crystalline quality. Room temperature Raman measurements exhibit high intensity E2 high mode and low intensity defect related mode.

Electrical and Optical Properties of Ga-doped SnO 2 Thin Films Via Pulsed Laser Deposition

Ga₂O₃-doped SnO₂ thin films were grown by using pulsed laser deposition (PLD) technique on glass substrate. The optical and electrical properties of these films were investigated for different doping concentrations, oxygen partial pressures, substrate temperatures, and film thickness. The films were deposited at different substrate temperatures (room temperature to 600℃). The best opto-electrical properties is shown by the film deposited at substrate temperature of 300℃ with oxygen partial pressure of 80 m Torr and the gallium concentration of 2 wt%. The as obtained lowest resistivity is 9.57 × 10?³ Ω ㎝ with the average transmission of 80% in the visible region and an optical band gap (indirect allowed) of 4.26 eV.