Silicon nitride thin films are deposited by RF (13.57 MHz) magnetron sputtering process using a Si (99.999 %) target and with different ratios of Ar/N2 sputtering gas mixture. Corning G type glass is used as substrate. The vacuum atmosphere, RF source power, deposit time and temperature of substrate of the sputtering process are maintained consistently at 2 ~ 3 × 10−3 torr, 30 sccm, 100 watt, 20 min. and room temperature, respectively. Cross sectional views and surface morphology of the deposited thin films are observed by field emission scanning electron microscope, atomic force microscope and X-ray photoelectron spectroscopy. The hardness values are determined by nano-indentation measurement. The thickness of the deposited films is approximately within the range of 88 nm ~ 200 nm. As the amount of N2 gas in the Ar:N2 gas mixture increases, the thickness of the films decreases. AFM observation reveals that film deposited at high Ar:N2 gas ratio and large amount of N2 gas has a very irregular surface morphology, even though it has a low RMS value. The hardness value of the deposited films made with ratio of Ar:N2=9:1 display the highest value. The XPS spectrum indicates that the deposited film is assigned to non-stoichiometric silicon nitride and the transmittance of the glass with deposited SiO2-SixNy thin film is satisfactory at 97 %.

Insoluble catalytic electrodes were fabricated by RF magnetron sputtering of Pt on Ti substrates and the performance of seawater electrolysis was compared in these electrodes to that is DSA electrodes. The Pt-sputtered insoluble catalytic electrodes were nearly 150 nm-thick with a roughness of 0.18μm, which is 1/660 and 1/12 of these values for the DSA (dimensionally stable anodes) electrodes. The seawater electrolysis performance levels were determined through measurements of the NaOCl concentration, which was the main reaction product after electrolysis using artificial seawater. The NaOCl concentration after 2 h of electrolysis with artificial seawater, which has 3.5% NaCl normally, at current densities of 50, 80 and 140 mA/cm2 were 0.76%, 1.06%, and 2.03%, respectively. A higher current density applied through the electrodes led to higher electrolysis efficiency. The efficiency reached nearly 58% in the Pt-sputtered samples after 2 h of electrolysis. The reaction efficiency of DSA showed higher values than that of the Pt-sputtered insoluble catalytic electrodes. One plausible reason for this is the higher specific surface area of the DSA electrodes; the surface cracks of the DSAs resulted in a higher specific surface area and higher reaction sites. Upon the electrolysis process, some Mg- and Ca-hydroxides, which were minor components in the artificial seawater, were deposited onto the surface of the electrodes, resulting in an increase in the electrical resistances of the electrodes. However, the extent of the increase ranged from 4% to 7% within an electrolysis time of 720 h.

In2O3 films were deposited by RF magnetron sputtering on a glass substrate and then the effect of post depositionannealing in nitrogen atmosphere on the structural, optical and electrical properties of the films was investigated. Afterdeposition, the annealing process was conducted for 30 minutes at 200 and 400oC. XRD pattern analysis showed that the asdeposited films were amorphous. When the annealing temperature reached 200-400oC, the intensities of the In2O3 (222) majorpeak increased and the full width at half maximum (FWHM) of the In2O3 (222) peak decreased due to the crystallization. Thefilms annealed at 400oC showed a grain size of 28nm, which was larger than that of the as deposited amorphous films. Theoptical transmittance in the visible wavelength region also increased, while the electrical sheet resistance decreased. In this study,the films annealed at 400oC showed the highest optical transmittance of 76% and also showed the lowest sheet resistance of89Ω/□. The figure of merit reached a maximum of 7.2×10−4Ω−1 for the films annealed at 400oC. The effect of the annealingon the work-function of In2O3 films was considered. The work-function obtained from annealed films at 400oC was 7.0eV. Thus,the annealed In2O3 films are an alternative to ITO films for use as transparent anodes in OLEDs.

The CdS thin film used as a window layer in the CdTe thin film solar cell transports photo-generated electrons to the front contact and forms a p-n junction with the CdTe layer. This is why the electrical, optical, and surface properties of the CdS thin film influence the efficiency of the CdTe thin film solar cell. When CdTe thin film solar cells are fabricated, a heat treatment is done to improve the qualities of the CdS thin films. Of the many types of heat treatments, the CdCl2 heat treatment is most widely used because the grain size in CdS thin films increases and interdiffusion between the CdS and the CdTe layer is prevented by the heat treatment. To investigate the changes in the electrical, optical, and surface properties and the crystallinity of the CdS thin films due to heat treatment, CdS thin films were deposited on FTO/glass substrates by the rf magnetron sputtering technique, and then a CdCl2 heat treatment was carried out. After the CdCl2 heat treatment, the clustershaped grains in the CdS thin film increased in size and their boundaries became faint. XRD results show that the crystallinity improved and the crystalline size increased from 15 to 42 nm. The resistivity of the CdS single layer decreased from 3.87 to 0.26 Ωcm, and the transmittance in the visible region increased from 64% to 74%.

Most TCOs such as ITO, AZO(Al-doped ZnO), FTO(F-doped SnO2) etc., which have been widely used in LCD,touch panel, solar cell, and organic LEDs etc. as transparent electrode material reveal n-type conductivity. But in order to realizetransparent circuit, transparent p-n junction, and introduction of transparent p-type materials are prerequisite. Additionalprerequisite condition is optical transparency in visible spectral region. Oxide based materials usually have a wide optical band-gap more than ~3.0eV. In this study, single-phase transparent semiconductor of SrCu2O2, which shows p-type conductivity, havebeen synthesized by 2-step solid state reaction at 950oC under N2 atmosphere, and single-phase SrCu2O2 thin films of p-typeTCOs have been deposited by RF magnetron sputtering on alkali-free glass substrate from single-phase target at 500oC, 1%H2/(Ar+H2) atmosphere. 3% H2/(Ar+H2) resulted in formation of second phases. Hall measurements confirmed the p-typenature of the fabricated SrCu2O2 thin films. The electrical conductivity, mobility of carrier and carrier density 5.27×10−2S/cm,2.2cm2/Vs, 1.53×1017/cm3 a room temperature, respectively. Transmittance and optical band-gap of the SrCu2O2 thin filmsrevealed 62% at 550nm and 3.28eV. The electrical and optical properties of the obtained SrCu2O2 thin films deposited by RFmagnetron sputtering were compared with those deposited by PLD and e-beam.

Films consisting of a silicon quantum dot superlattice were fabricated by alternating deposition of silicon rich silicon nitride and Si3N4 layers using an rf magnetron co-sputtering system. In order to use the silicon quantum dot super lattice structure for third generation multi junction solar cell applications, it is important to control the dot size. Moreover, silicon quantum dots have to be in a regularly spaced array in the dielectric matrix material for in order to allow for effective carrier transport. In this study, therefore, we fabricated silicon quantum dot superlattice films under various conditions and investigated crystallization behavior of the silicon quantum dot super lattice structure. Fourier transform infrared spectroscopy (FTIR) spectra showed an increased intensity of the 840 cm-1 peak with increasing annealing temperature due to the increase in the number of Si-N bonds. A more conspicuous characteristic of this process is the increased intensity of the 1100 cm-1 peak. This peak was attributed to annealing induced reordering in the films that led to increased Si-N4 bonding. X-ray photoelectron spectroscopy (XPS) analysis showed that peak position was shifted to higher bonding energy as silicon 2p bonding energy changed. This transition is related to the formation of silicon quantum dots. Transmission electron microscopy (TEM) and electron spin resonance (ESR) analysis also confirmed the formation of silicon quantum dots. This study revealed that post annealing at 1100˚C for at least one hour is necessary to precipitate the silicon quantum dots in the SiNx matrix.

Mn-substituted BiFeO3(BFO) thin films were prepared by r.f. magnetron sputtering under an Ar/O2mixture of various deposition pressures at room temperature. The effects of the deposition pressure andannealing temperature on the crystallization and electrical properties of BFO films were investigated. X-raydiffraction patterns revealed that BFO films were crystallized for films annealed above 500oC. BFO filmsannealed at 550oC for 5 min in N2 atmosphere exhibited the crystallized perovskite phase. The (Fe+Mn)/Biratio decreased with an increase in the deposition pressure due to the difference of sputtering yield. The grainsize and surface roughness of films increased with an increase in the deposition pressure. The dielectricconstant of BFO films prepared at various conditions shows 127~187at 1kHz. The leakage current densityof BFO films annealed at 500oC was approximately two orders of magnitude lower than that of 550oC. Theleakage current density of the BFO films deposited at 10~30m Torr was about 5×10-6~3×10-2A/cm2 at 100kV/cm. Due to the high leakage current, saturated P-E curves were not obtained in BFO films. BFO film annealedat 500oC exhibited remnant polarization(2Pr) of 26.4µC/cm2 at 470kV/cm.

SnxSe100-X (15|X|30) alloys have been studied to explore their suitability as phase change materials for nonvolatile memory applications. The phase change characteristics of thin films prepared by a Radio Frequency (RF) magnetron co-sputtering system were analyzed by an X-ray diffractometer and 4-point probe measurement. A phase change static tester was also used to determine their crystallization under the pulsed laser irradiation. X-ray diffraction measurements show that the transition in sheet resistance is accompanied by crystallization. The amorphous state showed sheet resistances five orders of magnitude higher than that of the crystalline state in SnxSe100-X (x = 15, 20, 25, 30) films. In the optimum composition, the minimum time of SnxSe100-X alloys for crystallization was 160, 140, 150, and 30ns at 15mW, respectively. The crystallization temperature and the minimum time for crystallization of thin films were increased by increasing the amount of Sn, which is correlated with the activation energy for crystallization.

The effect of annealing under argon atmosphere on hydrogenated amorphous silicon (a-Si:H) thin films deposited at room temperature and 300˚C using Radio Frequency (RF) magnetron sputtering has been investigated. For the films deposited at room temperature, there was not any increase in hydrogen content and optical band gap of the films, and as a result, quality of the films was not improved under any annealing conditions. For the films deposited at 300˚C, on the other hand, significant increases in hydrogen content and optical band gap were observed, whereas values of microstructure parameter and dark conductivity were decreased upon annealing below 300˚C. In this study, it was proposed that the Si-HX bonding strength is closely related to deposition temperature. Also, the improvement in optical, electrical and structural properties of the films deposited at 300˚C was originated from thermally activated hydrogen bubbles, which were initially trapped at microvoids in the films.

세라믹 타겟인 Sr2Nb2O7 (SNO)과 Bi2O3을 장착한 RF-마그네트론 스퍼터링을 이용하여 SrBi2Nb2O9 (SBN) 박막을 p-type Si(100) 기판 위에 증착하였다. 증착시 두 타겟의 파워비를 조절하여 조성의 변화에 따른 SBN 박막의 구조적 및 전기적 특성을 조사하였다. 증착된 SBN 박막은 700˚C의 산소분위기에서 1시간 동안 열처리를 하였으며 상부전극으로 Pt를 증착한 후 산소분위기에서 30분 동안 700˚C에서 전극 후열처리를 실시하였다. 증착된 SBN 박막은 700˚C 열터리 후에 페로브스카이트 상을 나타냈으며 SNO 타겟과 Bi2O3타겟의 파워가 120 W/100 W 일 때 가장 좋은 전기적 특성을 나타내었다. 이때의 조성은 EPMA(Electron Probe X-ray Micro Analyzer) 분석을 통하여 확인하였으며 Sr:Bi:Nb의 비가 약 1:3:2임을 나타내었다. 이러한 과잉의 Bi조성을 가진 SBN 박막은 3-9 V의 인가전압에서 1.8 V-6.3 V의 우수한 메모리 윈도우 값을 나타내었으며 누설전류 값은 인가전압 5 V에서 1.54×10-7 A/cm2였다.