Young-Guk Son

Violet Photoluminescence Emitted from Al-doped ZnO Thin Films

We report on a strong violet luminescence emitted from the ZnO:Al films grown on glass substrate by radio-frequency magnetron sputtering. The growth of high-quality thin films and their optical properties are controlled by adjusting the mixture ratio of Ar and , which is used as the sputtering gas. The crystallinity of the films is improved as the oxygen flow ratio is decreased, as evidenced in both x-ray diffractometer and atomic force microscope measurements. As for the violet luminescence measured by photoluminescence (PL) spectroscopy, the peak energy and intensity of the PL signal are decreased with increasing the oxygen flow ratio. The peak energy of the violet PL spectrum for the thin film with an oxygen flow ratio of 50 % is almost constant, regardless of the increase of laser Power and temperature. These results indicate that the violet PL signal is probably due to defects related to interstitial Zn atoms.

Structural and Electrical Properties of Cu(In,Ga)Se 2 Thin Films Prepared by RF Magnetron Sputtering without Selenization

A one-step route was developed to fabricate (CIGS) thin films by radio frequency (RF) magnetron sputtering from a single quaternary target. The effects of the substrate temperatures on the structural and electrical properties of the CIGS layers were investigated by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDS) and Hall effect measurements. All the deposited films showed a preferential orientation along the (112) direction. The films deposited at and revealed that chalcopyrite main (112) peak and weak prominent peaks of (220)/(204) and (312)/(116), indicating polycrystalline structures. The element ratio of the deposited film at were almost the same as the near-optimum value. The carrier concentration of the films decreased with increasing substrate temperatures.

The Influence of Substrate Temperature on the Structural and Optical Properties of ZnS Thin Films

Znic sulfide (ZnS) thin films were deposited on glass substrates by radio frequency magnetron sputtering. The substrate temperature varied from room temperature (RT) to . The structural and optical properties of ZnS films were studied by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive analysis of X-ray (EDAX) and UV-visible transmission spectra. The XRD analyses reveal that ZnS films have cubic structures with (111) preferential orientation, whereas the diffraction patterns sharpen with the increase in substrate temperatures. The FESEM images indicate that ZnS films deposited at have nano-sized grains with a grain size of ~ 67 nm. Then films exhibit relatively high transmittance of 80% in the visible region, with an energy band gap of 3.71 eV. One obvious result is that the energy band gap of the film increases with increasing the substrate temperatures.

The Effect of Ar/O 2 Partial Pressure Ratio on the Ferroelectric Properties of (Pb 0.92 La 0.08 )(Zr 0.65 Ti 0.35 )O 3 Thin Films Deposited by RF Magnetron Sputtering Method

PLZT ferroelectric thin films were deposited on Pt/Ti//Si substrate with buffer layer in between by rf magnetron sputtering method. In order to investigate the effect of Ar/ partial pressure ratio on the ferroelectric properties of PLZT thin films, PLZT thin films were deposited at various Ar/ partial pressure ratio ; 27/1.5 seem, 23/5.5 seem, 21/7.5 seem and 19/9.5 seem. The crystallinities of PLZT thin films were analyzed by XRD. The surface morphology was observed using FE-SEM. The P-E hysteresis loops, the remanent polarization characteristics and the leakage current characteristics were obtained using a Precision LC. The crystallinity and elaborateness of PLZT thin films were decreased as increasing the oxygen partial pressure ratio. And preferred orientation of PLZT thin films changed from (110) plane to (111) plane. The oxygen partial pressure ratio affects the thin film surface morphology and the ferroelectric properties.

Effects of Substrate Temperatures on the Crystallinity and Electrical Properties of PLZT Thin Films

PLZT thin films were deposited on platinized silicon (Pt//Si) substrate by RF magnetron sputtering. A buffer layer was fabricated, prior to deposition of PLZT films. the layer was strongly affected the crystallographic orientation of the PLZT films. X-ray diffraction was performed on the films to study the crystallization of the films as various substrate temperatures (Ts). According to increasing Ts, preferred orientation of films was changed (110) plane to (111) plane. The ferroelectric, dielectric and electrical properties of the films were also investigated in detail as increased substrate temperatures. The PLZT films deposited at showed good ferroelectric properties with the remnant polarization of and leakage current of .

The Dielectric Properties of PLZT Thin Films as Post Annealing Temperatures of TiO 2 Buffer Layer

(PLZT) thin films with buffer layers were deposited on Pt/Ti//Si substrates by an R.F. magnetron sputtering method in order to improve the ferroelectric characteristics of the films. And the ferroelectric properties and crystallinities of the PLZT thin films were investigated in terms of the effects of the post annealing temperatures of buffer layers between a platinum bottom electrode and PLZT thin film. The ferroelectric properties of the PLZT thin films improved as increasing of the post annealing temperatures of layers, thereby reaching their maximum at .