Yu Sup Jung

Properties of AZO/Ag/AZO Multilayer Thin Film Deposited on Polyethersulfone Substrate

The AZO/Ag/AZO multilayer films were deposited on polyethersulfone (PES) substrate by using facing target sputtering methods at room temperature. The AZO/Ag/AZO multilayer films with polymer substrate had advantages, such as low sheet resistance, high optical transmittance in visible range and stable mechanical properties. From the results, the AZO/Ag/AZO multilayer films (50/12/50 nm) demonstrated a sheet resistance of 11 Ω/□ and average transmittance of 87% in visible range (wavelength of 380-770 nm). Moreover, the multilayer showed stable mechanical properties compared to the single-layered AZO sample during the bending test due to the existence of the ductile Ag metal layer.

Properties of p-type N-doped Cu2O thin films prepared by reactive sputtering

We have investigated the electrical, optical, and structural properties of p-type nitrogen (N)-doped Cu2O thin films prepared at various nitrogen gas flow rates for application in heterojunction solar cells. The N-doped Cu2O thin films were fabricated by facing-target reactive sputtering. The hole concentration of the N-doped Cu2O thin films was affected by N2 gas flow rate. With increasing N2 gas flow rate from 0 to 0.5 sccm, the hole concentration and mobility of N-doped Cu2O films increased sharply. The resistivity, hole concentration, and mobility of the N-doped Cu2O films prepared at a N2 gas flow rate of 4 sccm were 1.9 Ωcm, 2.0 × 1018 cm−3, and 3.4 cm2V−1s−1, respectively. The N-doped Cu2O films showed Cu2O(111) and Cu2O(200) diffraction peaks. Cu2O(200) diffraction peak intensity increased slightly with N2 gas flow rate. The Cu2O(200) peaks were stronger at a N2 gas flow rate of 4 sccm than at other gas flow rates.

Electrochromic Properties of Tungsten Oxide Films Prepared by Reactive Sputtering

WO3-x thin films were deposited on induim tin oxide (ITO) glass substrates with various oxygen flow ratios from 0.55 to 0.7 by the reactive facing-target sputtering method, at a power density of 4 W/cm2 and room temperature. The structural properties of the WO3-x thin films were measured by X-ray diffractometry and Raman spectral analysis. As-deposited WO3-x thin films had an amorphous structure. In the Raman spectra, WO3-x thin films exhibited two strong peaks at 770 and 950 cm-1 attributed to the vibrations of W6+–O and W6+=O bonds, respectively. The electrochemical and optical properties of WO3-x thin films were measured by cyclic voltammetry and UV/vis spectrometry. The results showed the highest charge density at an oxygen flow ratio of 0.7 and the highest transmittance in the visible range. The maximum coloration efficiency was 30.82 cm2/C at an oxygen flow ratio of 0.7.

Characteristics of AZO/Cu/AZO Multilayer Thin Films Prepared on Polyethersulfone Substrate at Room Temperature

Highly conducting Al doped ZnO(AZO)/Cu/AZO triple multilayer thin films were deposited on polyethersulfonesusbtrate at room temperature. We investigated the structural, electrical, optical, and mechanical properties of triple multilayers as a function thickness of Cu layers. The triple multilayer with flexible substrate had advantages such as low sheet resistance and stable mechanical properties as compared with single oxide layer. From the results, sheet resistance value of AZO(50 nm)/Cu(9 nm)/AZO(50 nm) multilayer was 12 Ω/□, and average optical transmittance(380–770 nm) value of multilayer was 80%. Moreover the triple multilayer showed mechanical flexural strength properties than single-layered AZO thin films during bending test due to the existence of ductile Cu metal layer.

Properties of Ga-Al Doped ZnO with Various Thicknesses Prepared by Facing Targets Sputtering Method

Gallium-Aluminum doped Zinc Oxide (Ga-Al doped ZnO) thin films prepared on glass substrates by using facing targets sputtering methods. Electrical, structural and optical properties of Ga-Al doped ZnO thin film with various thicknesses were studied in detail. Crystal structure of the Ga-Al doped films was hexagonal wurtzite. Increased thickness of Ga-Al doped ZnO thin film, the resistivity decreased and crystallity improved. As the results, The resistivity of Ga-Al doped ZnO thin films with thickness of 500 nm exhibited 4.17×10–4 Ω.cm and average optical transmittance of all thin films showed above 85% in the visible range.

Characteristics of Ga-Al Doped Zinc Oxide Thin Films Deposited by Facing Targets Sputtering

Gallium-aluminum doped zinc oxide (GAZO) thin film is evaluated as an alternative to ITO for use as transparent electrodes for display devices. GAZO transparent conducting thin films were deposited using a facing targets sputtering (FTS) system with a hetero-targets. The FTS system can generate high plasma density, suppress the bombardment of high-energy particles to the substrate, and reduce the working pressure and substrate temperature. The average transmittance achieved with these films was as high as 80% in the visible range. Using a working pressure of 0.4 Pa, the lowest resistivity achieved with the deposited film was 5.342 × 10−4 Ω·cm.

Properties of ITO/Ga-Al Doped ZnO Bilayer Thin Film for Saving ITO Material

The indium tin oxide (ITO) thin films have advantages such as low resistivity (≒ 10−4Ω·cm) and high transmittance (>85%) in visible range. However, Indium in ITO is rare metal, a high cost and toxicity. Therefore, ITO substitute material is necessary. In this study, we fabricated the ITO/Ga-Al doped ZnO (GAZO) bilayer for saving ITO material by using facing targets sputtering methods. The ITO/Ga-Al doped ZnO bilayer thin films were deposited various thicknesses and substrate temperature. As a results, resistivity, mobility and carrier concentration of the ITO(80 nm)/GAZO(100 nm) bilayer thin film at 250°C exhibited 3.79 × 10−4Ω·cm, 31.13cm2/V·s and 5.21×1020cm−3. Average optical transmittances of all ITO/GAZO bilayer thin film exhibited above 90% in visible range.

Properties of Cu2O Thin Films for All-Oxide Solar Cells

In this work, p-type Cu2O thin films deposited by RF magnetron sputtering for Cu2O based all metal oxide solar cells were studied as a function of oxygen partial pressure ratio at room temperature. The Cu2O (111) x-ray diffraction peaks were indicated as a function of oxygen partial pressure ratio. Optical band gap energies of as-deposited Cu2O thin films ranged from 1.88 to 1.96 eV as a function of oxygen partial pressure ratio. The resistivity and mobility of the p-type Cu2O thin film with an oxygen partial pressure ratio of 2.4% was 2 ×104 Ω·cm and 15.1 cm2/V·s, respectively.