Myoung-Hwa Kim

High-rate deposition of plasma polymerized thin films using PECVD method and characterization of their optical properties

Abstract Plasma polymerized organic thin films were deposited at temperature in the range of room temperature to 693 K by plasma enhanced chemical vapor deposition method using the thiophene (C4H4S) precursor. Radio frequency (RF) with 13.56 MHz was applied and the RF power was changed in the range from 30 to 100 W with a gas ratio of Ar:H2=1:1. The as-grown organic thin films were basically characterized with ellipsometry, UV–Vis spectroscopy, and photoluminescence (PL) measurements. In order to compare the difference of optical properties of the plasma polymerized organic thin films, the effects of the RF power and deposition temperature on their structural properties were mainly studied in this work. UV–Vis spectra showed an energy band gap shift from 3.78 to 4.02 eV with increasing RF power and quite high optical transmittance up to 95%. During CVD, moreover, the plasma diagnostics were in situ carried out by using optical emission spectroscopy that showed a strong dependency of intensity on RF powers. To check a possibility of optical device application, PL measurements were also carried out. From the PL data, we could obtain the maximum PL emission intensity at approximately 550 nm wavelength from a plasma polymerized organic thin film grown at room temperature and RF power of 70 W with gas ratio of Ar:H2=1:1. The maximum growth rate is obtained to be 115 nm/min.

Chemical interaction, adhesion and diffusion properties at the interface of Cu and plasma-treated thiophene-based plasma polymer (ThioPP) films

Abstract Chemical interaction, adhesion and diffusion properties at the interface of Cu and plasma-treated thiophene-based plasma polymer (ThioPP) films deposited by plasma-enhanced chemical vapor deposition (PECVD) were studied. Surface characterization of ThioPP films treated by Ar and O 2 plasma using X-ray photoelectron spectroscopy (XPS), contact angle measurements, and atomic force microscopy (AFM) showed the formation of CO chemical bonds by O 2 plasma treatment and increase in surface roughness resulting in the decrease of contact angle. The chemical interaction between Cu and plasma-treated ThioPP films investigated by XPS showed the formation of CuS chemical bonding resulting in the strong adhesion of Cu on ThioPP films. Diffusion properties of Cu/ThioPP films annealed at 450°C for 1 h were surveyed by current–voltage ( I – V ) measurement. The slight reduction of Cu diffusion into ThioPP films treated by O 2 plasma compared to that of the samples untreated or treated by Ar plasma is attributed to the formation of new chemical bonding states on the surface of O 2 plasma-treated ThioPP films.

METAL-DOPED ZnO THIN FILMS: SYNTHESIS, ETCHING CHARACTERISTIC, AND APPLICATION TEST FOR ORGANIC LIGHT EMITTING DIODE (OLED) DEVICES

Metal-doped ZnO films with various metal contents (Al, Ag and Li of 0–10 wt.%) were prepared by RF magnetron sputtering system with specially designed ZnO targets. The structural, optical and electrical properties of MZO films depended on the type and content of doping in target. Electrical resistivity of LZO thin films increased with increasing Li doping amounts between 0 and 4 wt.%, suggesting that an epitaxial LZO film has high resistivity. We observed morphology in pure ZnO films by using different etchant. In addition, etching rate were contrasted with the etchant concentration and pH. The etching rate is proportional exponentially to pH value. These data will be the technical basis for TCO application. Also, the dry etching rate decreased with increasing the Cl2 concentration in CH4/H2/Ar + additive Cl2 gas mixture but metal dopants were etched effectively.

Synthesis of ZnO nanoparticles by spray-pyrolysis method and their photocatalytic effect

ZnO nanoparticles were synthesized by spray pyrolysis method using the zinc acetate dihydrate as starting material at various synthesis temperatures. The structures of the synthesized ZnO were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transformation infrared (FT-IR), and UV-vis spectroscopy. With increasing synthesis temperature, the mean diameter of ZnO nanoparticles increased, and their crystallinity was improved. The photocatalytic activity of ZnO was studied by the photocatalytic degradation of methyleneblue (MB) under UV irradiation (365nm) at room temperature. The results show that the photocatalytic efficiency of ZnO nanoparticles was enhanced by increasing synthesis temperature.

Study on Wet chemical Etching Characterization of Zinc Oxide Film for Transparency Conductive Oxide Application

투명 전도성 산화물 전극(transparent conductive oxide electrodes)에 적용하기 위하여 RF 마그네트론 스퍼터링 방법에 의해 유리 기판 위에 산화아연 박막을 증착하였다. 투명 전극으로써 응용되기 위한 최적의 조건으로 기판온도를 상온으로 유지하고 RF power 200 W, 타겟과 기판사이의 거리(Dts)가 30 ㎜일 때 증착된 산화아연 박막으로부터 가장 낮은 비 저항값(7.4×10?³ Ω㎝)을 얻어 낼 수 있었으며, 85% 이상의 높은 투과율을 만족하는 박막을 얻을 수 있었다. 실질적인 소자로써의 응용을 위해 photo lithography를 통한 pattern을 형성, 습식 식각을 통하여 그 특성을 알아보고자 하였다. 습식 식각에서 사용된 식각용액(etchant)으로는 다양한 산 용액(황산, 옥살산, 인산)을 사용하였으며, 산의 농도 변화에 따른 식각특성과 식각시간 및 식각 이미지(표면형상)의 변화를 알아보았다. 결과적으로 산화아연의 습식식각은 산의 종류와 무관하게 산 용액의 농도(즉, pH)에 크게 의존하며, pH가 증가함에 따라 식각율이 지수함수적으로 감소하고 아울러 다양한 식각 이미지가 나타남을 최초로 고찰할 수 있었다.In order to apply for transparent conductive oxide(TCO), we deposited ZnO thin films on the glass at room temperature by RF magnetron sputtering method. Deposition conditions for high transmittance and low resistivity were optimized in our previous studies. Under the deposition condition with the RF power of 200 W, target to substrate distance of 30 mm and working pressure of 5 mTorr, highly conductive() and transparent(over 85%) ZnO films were prepared. Highly oriented ZnO film in the [002] direction were obtained with specifically designed ZnO targets. Systematic study on dependence of deposition parameters on electrical and optical properties of the as-grown ZnO films were mainly investigated in this work. And for application tests using these films as transparent conductive oxide anodes, wet chemical etching behaviors of ZnO films were also investigated using various chemicals. Wet-chemical etching behavior of ZnO films were investigated using various acid solutions. The concentrations of these different acid solutions were controlled to study the etching shapes and etching rate. ZnO films were anisotropically etched at various concentrations and wet etching led to crater-like surface structure. Also we firstly found that the etching rate and etching shapes of ZnO films strongly depended on the etchant concentrations (i.e. pH) and the etching rate is exponentially decreased with increasing pH values regardless of the acid etchants.

SPRAY PYROLYSIS OF MANGANESE DOPED ZINC SILICATE PHOSPHOR PARTICLES

Spherical-shape Zn2SiO4:Mn phosphor particles with the mean particle size from submicron to micron sizes were prepared by ultrasonic spray pyrolysis method. A droplet separator was introduced to control the size distribution of the phosphor particles with spherical shape. The Zn2SiO4:Mn phosphor particles with 2 mol% doping concentration of manganese have decay time and have photoluminescence intensities comparable with those of the latest commercial product prepared by the solid state reaction method. The size of the phosphor particles was decreased from 1000 to 200 nm as the inorganic salt solution concentration was changed from 0 to 5 M. The phosphor particles prepared from the solutions above 0.5 M have photoluminescence intensities comparable with that of the latest commercial product.

Synthesis and characterization of BON thin films using low frequency RF plasma enhanced MOCVD: effect of deposition parameters on film hardness

With the expectation of getting hard material, we have firstly grown the BON thin film by radio frequency plasma enhanced metal-organic chemical vapor deposition with 100 kHz frequency and trimethyl borate precursor. The plasma source gases used in this study were Ar and H , and two kinds of nitrogen source gases, N and NH , were also employed. The as-grown films 22 3 were characterized with XPS, IR, SEM and Knoop microhardness tester. The film growth rate was influenced both by substrate temperature and by nitrogen source gas. It decreased with increasing the substrate temperature, and was higher by using NH 3 rather than by N . The hardness of the film was dependent on several factors such as nitrogen source gas, substrate temperature 2 and film thickness due to the variation of the composition and the structure of the film. Both nitrogen and carbon-content could raise the film hardness, on which nitrogen content had stronger effect than carbon. The smooth morphology and continuous structure yielded high hardness. The maximum hardness of BON film was approximately 10 GPa. 2003 Elsevier Science B.V. All rights reserved.

Personal Cognitive Characteristics in Affordance Perception: Case Study in a Lobby

User activities in performing tasks are influenced by the way the user perceives the related context and environment, and determined by the user making a judgment on their preferences. Structures in the physical environment afford user activities when they are properly perceived. This chapter addresses how user activities and perceived affordances are different and reflect personal creativity modes, which are determined by factual–intuitive perception inclination and subjective– objective decision preferences as well as the introverted–extroverted nature of the user. To enable the designing-in of various affordance features for diverse users in varying contexts, an understanding of the relationship between the personal characteristics of the user and affordance perception would be helpful. We conducted a case study in a public space used by many ordinary people. User activities and behaviors were analyzed in specific tasks given to 20 students in a building lobby they had never previously visited. The tasks were devised so that various affordance features would be relevant, while eliminating factors affecting the affordance perception (culture, intelligence, etc.) other than those due to the personal characteristics of the user. User activities can be classified into several different groups for each task based on the affordance features involved in their activities. These differences are then compared with their personal creativity modes. For users of less common activities for some tasks, relevant personal cognitive characteristics have been identified.

PACVD of plasma polymerized organic thin films and comparison of their electrochemical properties

Summary form only given, as follows. Summary form only given. Plasma polymerized organic thin films were deposited on Si(100), glass and metal substrates using thiophene and ethylcyclohexane precursors by PECVD method. In order to compare electrochemical properties of the as-grown thin films, the effects of the RF plasma power in the range of 30-100 W AFM showed that the polymer films with smooth surface and sharp interface could be grown under various deposition conditions. Impedance analyzer was utilized for the determination of I-V curve for leakage current density and C-V for dielectric constants, respectively. To obtain C-V curve, we used a MIM structure of metal(Al)-insulator(plasma polymerized thin film)-metal(Pt) structure. Al as the electrode was evaporated on the thiophene films that grew on Pt coated silicon substrates, and the dielectric constants of the as-grown films were then calculated from C-V data measured at 1MHz. From the electrical property measurements such as I-V and C-V characteristics, the minimum dielectric constant and the best leakage current of thiophene thin films were obtained to be about 3.22 and 1 x 10/sup -11/ A/cm/sup 2/. However, in the case of ethylcyclohexane thin films, the minimum dielectric constant and the best leakage current were obtained to be about 3.11 and 5 x 10/sup -12/ A/cm/sup 2/.