ICMCTF2003 Session CP-2: Symposium C Poster Session

Thursday, May 1, 2003 5:00 PM in Room Town & Country

Thursday Afternoon

Time Period ThP Sessions | Topic C Sessions | Time Periods | Topics | ICMCTF2003 Schedule

CP-2-1 Optimization of MgF2/ SiOxNy /Si for Antireflective Coatings on Solar Cells
K. C. Mohite (University of Pune, India); C. Nouveau (ENSAM, France); S.T. Pawar (University of Pune, India); A.B. Mandale (National Chemical Laboratory, India); M.G. Takwale (University of Pune, India)

The antireflection ( AR) coating is one of the key technologies for making the high efficient solar cells. We have studied the silicon oxynitride (SiOxNy) and magnesium fluoride (MgF2) double layer antireflective (DLAR) coatings for Solar Cells. A theoretical optimization process and an experimental verification were carried out to achieve minimum reflectance using DLAR coating of MgF2 /SiOxNy on a mirror polished crystalline silicon wafer. The films were prepared by an electron beam physical vapor deposition ( EB-PVD) technique with plasma pre-treatment. The refractive indices and thicknesses of these films were controlled by process parameters. Films of appropriate refractive indices with near quarter wavelength thickness were obtained by optimizing the substrate temperature and deposition time. The substrate temperature and deposition time were varied in the range of 100°C - 400°C and 0.5 min to 3 min respectively.

These films were characterized by X-Ray Photoelectron Spectroscopy(XPS), Energy Dispersive Spectroscopy (EDS), Spectroellipsometry and UV-Visible spectroscopy. An ellipsometer Gaertner having a He-Ne laser at wavelength of 632.8 nm as a light source was employed to measure the refractive index of the films. Thickness of the films was measured by Talystep profilometer. The refractive index of around 1.89 and thickness of about 125 nm for the SiOxNy film was obtained at 350°C substrate temperature and 1.5 min deposition time. And for the MgF2 film the refractive index of around 1.37 was achieved at 250°C substrate temperature and of 2 min deposition time. We experimentally confirmed the minimum reflectivity of 7.4 X 10-5 and bandwidth of 132 nm for R~10-3 and 26 nm for R~10-4 for DLAR coating.

CP-2-2 Characterization of Sputtered ITO and WO3 Films used in Electrochromic Devices
H.-N. Cui, V. Teixeira (University of Minho, Portugal); E. Fortunato (Universidade Nova de Lisboa, Portugal); E. Bertran (Universitat de Barcelona, Spain)
ITO (Indium-tin-oxide) thin film has been found extensive applications in photoelectronics, especially in electrochromic (EC) devices where ITO film are used as transparent electrodes. Since tungsten oxide (WO3) film is one of the most studied EC materials and presents coloration in both amorphous and crystalline phase after supplying a low voltage, both amorphous and crystalline ITO films are needed depending on different applications. Amorphous Indium-tin-oxide (ITO) and crystalline WO3 thin films were obtained using DC-magnetron reactive sputtering in different oxygen partial pressure (PO2) at room temperature (RT). The films prepared were characterized by SEM, XRD, XPS and UV-Vis-NIR spectroscopy. The energy gap of ITO between the valence band and the conduction band varies within 3.26 eV and 3.66 eV and decreases as the PO2 during the sputtering process. For all ITO films the Figure of Merit was calculated. The films exhibited high maximum optical transmittance of above 94 % for ITO and 90% for WO3 to visible range. The interpretation about variation of the transmission, electron amount, electron density and effective Eg was given. The results on the tungsten oxide films show that for low PO2 they present an amorphous WO3 phase, while for high PO2 they present a mixture of a more crystalline WO3 phase and an oxygen deficient phase.
CP-2-3 The Fabrication of Photo-patternable Inorganic-Organic Hybrid Film for the Ridge Waveguide
S.H. Jeong (Yonsei University, South Korea); W.H. Jang (OLANTECH, South Korea); J.H. Moon (Yonsei Unversity, South Korea)
Organically Modified silicates (ORMOSLs) for the ridge waveguide are synthesized by sol-gel process. Proper waveguiding film requires its refractive index ratio between the core and cladding materials is greater than 0.35%. Control of the refractive index is achieved by varying the content of the refractive index modifier in the cladding layer. Incorporation of the alkoxide with a UV-sensitive functional group allows a high-resolution pattern of the core layer with 8µmm linewidth using a conventional photo-lithography. Relatively thick core and cladding layers of 8µmm and 10µmm thickness, respectively were obtained by a single spin-coating without the production of any crack. Heat-treatment at temperatures lower than 150°C is sufficient to make inorganic-organic hybrid thin film with dense microstructure. And the resulting waveguide have low optical loss at the wavelength of 633nm, 1320nm and 1550nm.
CP-2-4 Photocatalytic and Hydrophilic Properties of Titanium Oxide Films Prepared by Physical Vapor Deposition
C.B. Shu, H.C. Chen, T.S. Yang, M.S. Wong (National Dong Hwa University, Taiwan, ROC)
Titanium oxide films were prepared by reactive magnetron-sputtering and electron-beam evaporation processes on silicon and quartz wafers. The photocatalytic properties were characterized by the degradation of acetone on quartz crystal microbalance (QCM). The photo-induced hydrophilic properties were tested by the variation of water contact angle on the films after UV-light (370 nm) illumination. The microstructure and optical properties of the films were characterized by XRD, Raman and UV-VIS absorption spectra. The relation between microstructure and the photocatalytic and hydrophilic properties were explored. It is found that reactive magnetron-sputtering is a better process to deposit anatase phase of titanium oxide film at low substrate temperature (150°C).
CP-2-5 Optical Thin Films for the Passivation and Antireflection of n-ZnO UV Photodetectors
I.S. Jeong (Institute of Physics and Applied Physics, South Korea); S. Im (Yonsei University, South Korea); C.H. Park, H.S. Bae (Institute of Physics and Applied Physics, South Korea); H.H. Park (Yonsei University, South Korea); J.H. Kim (Institute of Physics and Applied Physics, South Korea)
N-ZnO UV photodetectors with a transparent insulating overlayer have been fabricated on p-Si. N-ZnO was deposited on p-Si at 480 °C by RF sputtering for an n/p heterojunction structure and then an electrically resistive passivation layer was deposited on the n-ZnO surface at room temperature by the same deposition method. When an amorphous aluminum oxide was used for the overlayer, most of the UV photons (with ~3 eV) were absorbed by the n-ZnO film, so that the n/p heterojunction photodiode exhibited a high level of photocurrent. On the other hand, with an insulating ZnO overlayer only a small amount of photocurrent was obtained from the n/p photodiode. Transmittance through adequate transparent overlayers on the n-ZnO was also simulated to confirm the photo-I-V results. More details on electrical and optical characterizations on our n/p photodiodes are to be discussed.
CP-2-6 Characteristics of Indium-thin-oxide Film Deposited by an Oxygen ion Beam Assisted Deposition Technique on Organic Electroluminescent Device (OLED)
N.G Cho, D.W. Kim (Sungkyunkwan University, South Korea); Y.W Ko, J.H. Lee (Electronics and Telecommunications Research Institute, South Korea); G.Y. Yeom (Sungkyunkwan University, South Korea)
To fabricate active matrix organic electroluminescent devices (OLED), a transparent conducting material such as indium tin oxide (ITO) has to be deposited on the organic material of the devices and the organic materials are easily damaged by the oxygen atom, ion bombardment, heating, etc. during the deposition processing of ITO. Therefore, it is very difficult to deposit ITO on the OLED to form a transparent electrode. Also, it is difficult to maintain both electrical conductivity and transparency of ITO without generating damages to OLED when a conventional ITO deposition technique such as sputter deposition is used. Therefore, in this study, a dual oxygen ion beam assisted evaporator system has been used to deposit ITO films on the OLED to investigate as a possible transparent and conductive ITO deposition technique without generating damage to OLED. The characteristics of the deposited ITO on OLED was investigated using a four-point probe and a UV-spectrosmeter to measure the resistivity and transmittance of ITO films, respectively. The change of surface roughness after ITO deposition was investigated using an atomic force microscopy. Also, current-voltage (I-V) characteristics of the fabricated OLED with the ITO electrode were measured by HP-4145A semiconductor parameter analyzer.
CP-2-7 The Effect of Chlorine-based Additive Gas on SiC Etch Rates in NF3 Inductively Coupled Plasma
H.Y. (Ms.) Lee, D.W. Kim, C.H. Jeong (Sungkyunkwan University, South Korea); Y.J. Sung (Samsung Advanced Institute of Technology, South Korea); H.S. Kim, G.Y. Yeom (Sungkyunkwan University, South Korea)
Silicon carbide is a wide bandgap semiconductor that has an excellent potential for electronic devices operating at high power, high frequency, and high temperature. However, SiC shows problems in the etching due to its large binding energy. In addition, new technologies including microelectromechanical systems demand a deep etching, therefore, SiC etching with high etch rates and high etch selectivity over mask material is required for the development of SiC-based devices. In this study, NF3 inductively coupled plasmas were used to etch SiC. The etch rates were investigated as a function of pressure, source power, and dc bias voltage. Especially, to obtain high SiC etch rates and high etch selectivities over mask materials, chlorine-based additive gases such as Cl2, HCl, and BCl3 were used. Their etch profiles were examined using a scanning electron microscope (SEM).
CP-2-8 Characteristics of Indium Tin Oxide Thin Films Prepared Using Electron Beam Evaporation
A. Ide-Ektessabi, M. Yamaguchi, H. Nomura (Kyoto University, Japan)
Tin-doped Indium oxide (ITO) has been widely utilized in numerous industrial applications because of its combination of visible light transparency and conductivity. The optical and electrical properties of the ITO films are highly dependent on their composition ratio. In this article ITO films were fabricated using electron beam evaporation with elevating substrate temperature and varying oxygen flow rate. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Rutherford backscattering spectroscopy (RBS) were conducted in order to measure the composition and chemical state of these thin films. Electrical and optical measurements were also carried out.
CP-2-9 The Preparing of Ultralow Losses Mirrors with Reflectivity of over 99.9968%
Y.J. Wang, F. ZhengXiu, Z. Yuan (Chinese Academy of Sciences, PR China)

High reflection mirrors with small scatter and absorption losses are important for a wide range of applicants in optical science, such as in Ring Laser Gyroscope (RLG) and Laser Interferometer Gravitational Wave Observatory (LIGO), their requirements are unique: (1) the mirrors should be backscatter-free and (2) each mirror should have a total optical loss of 10 ppm or less.

The ideal thin films for applications should be optically stable, free of scattering and absorption, mechanically strong, and chemically inert. In fact, the prepared optical thin films have losses, more or less. In this paper, the ultralow loss mirrors (?1315nm) have been prepared by RF ion beam sputtering with the materials of tantalum oxide and silicon oxide. The mirror's loss, including transmission, scattering and absorption are measured and analyzed, is less than 32ppm, which is corresponds to reflectivity of over 99.9968%. This is the highest reflectivity achieved at this wavelength in public reports.

CP-2-10 Influence of the Film Structure on the Electrochromic Properties of CeO2 Thin Films Deposited by eBeam PVD.
I. Porqueras, C. Person, E. Bertran (Universitat de Barcelona, Spain)
Cerium Oxide (CeO2) thin films were deposited by e-beam PVD on different substrates, such as glass, ITO coated glass, Si wafers and fused silica. Ion bombardment assistance during the deposition process is recognised as a useful tool to enhance the opto-mechanical properties of evaporated films. The ion bombarded films show a denser structure and a different layer growth that may alter the electrochromic properties (both optical modulation and charge storage capacity). The structural characterisation was carried out by means of TEM and XRD analysis, which revealed that ion bombardment induces structure in the originally amorphous films. Electrical properties (resistivity and impedance response) were carefully evaluated in order to find correlation between the induced structure and the electrochromic properties of the CeO2 films.
Time Period ThP Sessions | Topic C Sessions | Time Periods | Topics | ICMCTF2003 Schedule