Papers

ICMCTF2002 Session CP-1: Symposium C Poster Session

Monday, April 22, 2002 5:00 PM in Room Town & Country

Monday Afternoon

Time Period MoP Sessions | Topic C Sessions | Time Periods | Topics | ICMCTF2002 Schedule

CP-1-1 Influence of Process Parameters on the Structural and Optical Properties of ZnO Thin Films Prepared by RF Magnetron Sputtering Y.-M. Lu (Kung Shan University of Technology, Taiwan, ROC) The influence of process parameters on the structural and optical properties of ZnO films prepared by RF magnetron sputtering method using zinc target in the O₂/Ar gas mixture has been investigated.The films are polycrystalline with grain size in the range of several tenths nanometers. The X-ray diffraction measurements showed that all of the films are pure ZnO with hexagonal wurtzite type structure and have ab strong (002) preferred orientation.Optical absorption spectra show high transparency through the visible region with average transmission above 80%.A sharp absorption edge around 380nm wavelength corresponds to the intrinsic band gap of ZnO(3.2eV).The energy gap of ZnO varied from 3.21eV to 3.26eV after annealing at 600C in argon atmosphere.The index of refraction increases slightly with increasing substrate temperature from 250^opC to 480°C.The PL intensity of ZnO have strong dependence on the O₂/Ar ratio in the sputtering gas.The can be attributed to interstitial zinc atoms acting as luminescence centers.
CP-1-2 Improvement of Adhesion and Conductivity of Indium-tin-oxide (ITO) Thin Films Deposited on Polymeric Substrates by Corona Discharge Treatment of the Substrates R.A.G. Almeida (Michigan Technological University); K.H. Schulz (Mississippi State University); A.K. Kulkarni (Michgan Technological University) Transparent plastic substrates are currently used in opto-electronic devices such as displays and solar cells. Because of the low melting points of these materials, annealing at high temperatures (400°C) to improve the grain structure and hence the conductivity has not been possible. It is well known that corona discharge treatment of polymeric materials introduces polar groups into the surface, resulting in increased surface energy and thus improved wettability and adhesion. We report here significant improvements in the conductivity and the adhesion of ITO thin films deposited on corona treated polymeric substrates. From contact angle measurements, the adhesion energy of the ITO film to the polymeric substrate is shown to increase from 100 ergs/ cm² without corona treatment to 140 ergs / cm² with corona treatment. ( 9.0kV, 4.8 mA, 1 to 10 min.) The conductivity is shown to increase by a factor of 2-3 after corona treatment. There is a slight decrease of transmission in films deposited on corona treated substrates vs. films deposited on non-treated substrates. These changes in the electrical and optical properties of ITO thin films deposited on the corona treated substrates are attributed to less porous films resulting from the higher surface energies associated with the corona treated substrates.
CP-1-3 Investigation into the Production of TIO_x via the Dual Bipolar Magnetron Sputtering Technique. J. O'Brien, P.J. Kelly (University of Salford, United Kingdom) The use of pulsing to promote arc-free, stable deposition is well known and a number of studies have been, and are presently being carried out relating the pulsing parameters to plasma and film properties for the single magnetron case. For long-term deposition of dielectrics this process has the inherent problem of anode loss due to the build up of insulating layers. Dual bipolar deposition overcomes this problem by maintaining a clean anode surface in the form of alternative target faces. In this system the two magnetrons used are powered by the same power supply and pulsing unit and, as such, each target can be controlled to act alternatively as an anode and a cathode. This technique has already been applied in industry. However, the interrelation of pulsing parameters, plasma and most importantly film properties is less well documented for this process. In this study we consider the effect of pulsing parameters of the dual bipolar system on TiO_x films deposited from both coplanar and vertically opposed targets in a small production-scale system. In addition, Vtech magnetrons have been utilised which allow variations in field strength and level of unbalance to be studied. Film properties investigated include structural, optical, photocatalytic and mechanical characteristics. Moreover, variations in these properties are discussed in terms of the variation in current-voltage waveforms, power supplied, magnetron configuration and plasma characteristics with varying pulse parameters and deposition conditions.
CP-1-4 PACVD of Plasma Polymerized Organic Thin Films and Comparison on their Physical and Electrochemical Properties S.-H. Cho, Y.-J. You, M.-C. Kim, S.-B. Lee, J.-G. Kim, J.-H. Boo (SungKyunKwan University, Korea) Plasma polymerized organic thin films have been deposited on Si(100) and copper metal substrates at 25400°C using thiophene and toluene precursors by PACVD method for corrosion protection in the interlayer dielectrics of microelectronic devices. In order to compare physical and electrical properties of the as-grown thin films, the effect of the plasma power, gas flow ratio and deposition temperature on the contact angle, FT-IR, and corrosion protection efficiency were mainly studied. The result of contact angle measurement showed that the plasma polymerized toluene films have more hydrophobicity than the plasma polymerized thiophene films. FT-IR data showed that IR absorption peak intensities were increased whenever the polymerization was carried out at high RF power. Corrosion protection effiency(P_k) examined by AC impendence measurement in 3.5 wt.% NaCl solution provided an increasing tendency with increasing RF power. The highest P_k value of p! lasma polymerized toluene film (85.27% at 70W) was higher than that of the plasma polymerized thiophene film (65.17% at 100W), indicating inhibition of oxygen reduction because the densely packed and tightly interconnected toluene film acted as an efficient barrier layer to the diffusion of molecular oxygen.
CP-1-5 TiO₂ Based Photocatalytic Films H. Navasardyan (Yerevan, Physics Institute, Armenia); H. Balayan, L. Tkachenko, R. Hovsepyan (Yerevan, Institute of Chemical Technology "CHEMTECH", Armenia); V. Baghdasaryan (Yerevan, Physics Institute, Armenia) Water-alcoholic TiO₂ sols having mono-dispersed spherical particles sized 10 nm were used as initial substances for film formation. Sedimentation of colloidal particles was realized on borosilicate glass substrates. As a result, micro-heterogeneous film structures were obtained. The films were made by centrifugation method at 2000 - 4000 ppm. The films after thermal treatment in air have rutile structure with grains sized several nanometers. The work discusses the process of formation of TiO₂ based film structure. The obtained materials were tested as photo catalysts in the processes of destruction of harmful substances.
CP-1-6 Ion Beam Deposition of Optical Interference Coatings R.S. Blacker (Veeco Ion Tech Inc.); S.M. Lee (Veeco Ion Tech. Inc.); A. Dummer, K. Coates, I. Kameyama, D. Deakins, D. Siegfried, C. Montcalm (Veeco Ion Tech Inc.) Ion beam deposition of optical interference coatings has particular advantages over other techniques such as magnetron sputtering, e-beam or ion assisted e-beam. Environmentally stable, dense, low absorption, low stress films can be deposited under the appropriate system conditions. This paper relates both material and optical filter properties to the ion beam deposition conditions. The derived information has been used to understand and improve deposition processes, leading to advances in materials selection, layer properties and system utilization. Examples of narrow band pass and other telecommunication related optical interference filters are presented to illustrate the advantages of this process.
CP-1-7 DC Reactive Sputter Deposition of ZnO:Al Thin Film on Glass J.M. Ting, B.S. Tsai (National Cheng Kung University, Taiwan, ROC) As an optical thin film, aluminum Zinc Oxide (AZO) offers not only great optical characteristics but also controllable low resistivity. AZO thin film exhibits a sharp UV cut-off and a high refractive index in the IR range, and is transparent in the visible light. In this paper, we report the preparation and characterization of thin film AZO deposited on glass substrates. The objective of was to study the characteristics and properties of the resulting AZO thin films as a function of various growth parameters, including target composition, O₂/Ar ratio, deposition rate, and applied power. AZO thin films were deposited using a dc reactive sputter deposition technique. The characteristics and properties examined include crystallinity, grain size, surface morphology, resistivity, optical transmittance, and band gap Analytical tools including x-ray diffractometry (XRD), scanningelectron microscopy (SEM), atomic force microscopy (AFM), four-point probe, and photoluminescence (PL). Correlation between thin film characteristics/properties and growth parameters is presented and discussed.
CP-1-8 Preparation of Mn-Activated Yttrium Germanate Phosphor Thin Films for Electroluminescent Devices T. Minami, Y. Kobayashi, T. Miyata, M. Yamazaki (Kanazawa Institute of Technology, Japan) Recently, we proposed using a new multicomponent oxide phosphor composed of Y₂O₃ and GeO₂, i.e., a Mn-activated Y₂O₃-GeO₂ system ((Y₂O₃-GeO₂):Mn) phosphor, as the emitting layer for thin-film electroluminescent (TFEL) devices. This paper describes newly developed high-luminance TFEL devices using Mn-activated yttrium germanate phosphors: Y₄GeO₈:Mn, Y₂GeO₅:Mn and Y₂Ge₂O₇:Mn phosphors. The Mn-activated yttrium germanate phosphor thin films were prepared with a GeO₂ content of approximately 33, 50 or 67 molar% by conventional r.f. magnetron sputtering using a powder target. The TFEL devices were fabricated by combining a thick BaTiO₃ ceramic sheet insulating layer with a phosphor thin-film emitting layer. In order to obtain a high luminance emission, both the deposition conditions and the postannealing conditions of the phosphor thin films were optimized. The obtainable EL characteristics were considerably affected by the postannealing temperature of the thin-film emitting layers used. From X-ray diffraction analyses, all as-deposited Mn-activated yttrium germanate thin films were found to be amorphous. In contrast, phosphor thin films prepared with a GeO₂ content of approximately 33, 50 or 67 mol.% and postannealed above about 900°C were crystallized and identified as Y₄GeO₈, Y₂GeO₅ or Y₂Ge₂O₇, respectively. High luminances and luminous efficiencies for yellow emissions were obtained in TFEL devices using these postannealed ternary compound phosphors activated with Mn: 2500, 3020 or 2590 cd/m² was obtained in 1-kHz-driven TFEL devices with a Y₄GeO₈:Mn, Y₂GeO₅:Mn or Y₂Ge₂O₇:Mn thin-film emitting layer, respectively, postannealed at 1020-1045°C.
CP-1-9 Transparent Conducting V-co-doped AZO Thin Films Prepared by Magnetron Sputtering T. Minami, S. Suzuki, T. Miyata, M. Ishii (Kanazawa Institute of Technology, Japan) Recently, we reported that a V atom doped into ZnO acts as an effective donor; consequently, highly transparent and conductive V-doped ZnO (ZnO:V) thin films could be prepared by magnetron sputtering. This paper describes the effects of V-co-doping on transparent conducting Al-doped ZnO (ZnO:Al, or AZO) films prepared by magnetron sputtering. AZO thin films co-doped with V were prepared on glass substrates by conventional d.c. magnetron sputtering using a powder target. A mixture of ZnO powder and dopant powders, Al₂O₃ and V₂O₅, calcined in an Ar gas atmosphere was used as the target. The sputter deposition was carried out at a pressure of 0.2 Pa in a pure Ar gas atmosphere. The resistivity of V-co-doped AZO (ZnO:Al,V, or AZO:V) films was found to be relatively independent of V₂O₅ content up to 2 wt.%; it increased gradually with further increases of V content. However, the etching rate of AZO:V films in a HCl solution decreased markedly as the V content was increased. The etching rate in a KOH solution was also found to decrease as the V content was increased. It can be concluded that a chemical property, etching rate, of transparent conducting AZO films could be improved by co-doping V without significantly altering the original electrical or optical properties. In addition, AZO:V thin films were prepared with various Zn/O ratios in the sputter deposition. As a result, a low resistivity of 2.4X10^?4Ωcm was obtained in transparent conducting AZO:V films prepared with an Al₂O₃ content of 1 wt.% and a V₂O₅ content of 1 wt.% at a substrate temperature of 250°C by d.c. magnetron sputtering under optimized target preparation and sputter deposition conditions.
CP-1-10 Spectroellipsometry Studies the Heteroepitaxial Structure of 0.65PbMg₁3Nb₂3O₃-0.35PbTiO₃ Thin Films on Silicon Substrates by Pulsed Laser Deposition W.S Tsang (The Hong Kong Polytechnic University, China); F.F. Hau, C.L. Mak, K.H. Wong (The Hong Kong Polytechnic University, Hong Kong) 0.65PbMg₁3Nb₂3O₃-0.35PbTiO₃ (PMN-PT) thin films have been fabricated on (100)Si by pulsed laser depositon with deposition temperatures ranging from 525°C to 625°C. The structural properties of the films were characterized by X-ray diffraction (XRD). θ-2θ scans indicated that all the films were perovskite phase containing no impurity. ω-scans and φ-scans showed that all the films possessed the heteroepitaxial relation of (100)_PMN-PT\|\|(100)_MgO\|\|(100)_TiN\|\|(100)_Si structure. The surface morphology and the cross section of the film were examined by scanning electron microscopy (SEM). Spectroellipsometry (SE) was use to characterize the depth-profile and refractive index of these films. The ellipsometric spectra of the films were measured in the wavelength range of 400 nm - 830 nm. The depth-profile of the films, which were obtained by SE, were matched with the cross section of the films observed by SEM. The deposition-temperature dependent structural and optical properties of PMN-PT thin films were studied.
CP-1-11 The Effect of Excess Bi Content on the Crystallization and Ferroelectric Properties Bi_3.25La_0.75Ti₃O₁₂ Thin Films on Pt/Ti/SiO₂/Si substrates C.I. Kim, K.T. Kim, J.W. Kwon, I.W. Shim (Chung-Ang University, Korea) Ferroelectric materials, such as Pb(Zr,Ti)O₃ (PZT), and SrBi₂Ta₂O₉ (SBT), have attracted considerable attention due to their possible application in ferroelectric nonvolatile random access memory. PZT has low crystallization temperature 650°C and a large polarization value, but lead (Pb) is one of its primary contents, there is an environmental concern and the fatigue problem with a conventional electrode of Pt. On the other hand, SBT has good fatigue endurance but a small polarization by low temperature 650°C crystallization. La-substituted bismuth titanate(BLT) has emerged as a new promising ferroelectric due to its combined properties of low crystallization temperature below 650°C , good fatigue endurance and a medium polarization. The dependence of crystallization and electrical properties are related to the excess Bi content in Bi_3.25La_0.75Ti₃O₁₂ (BLT) thin films. In this study, the effect of excess Bi content on the crystallization and ferroelectric properties was investigated by x-ray diffraction(XRD) experiments during the metalorganic decomposition method for BLT thin films. The compositional depth profile of the interfaces between the BLT thin films and electrode materials using Auger Electron Spectroscopy (AES) revealed that Bi was enriched toward the surface of films, especially the higher excess Bi contents thin films, because excess Bi could not participate in the formation of the bi-layer perovskite phase. Increasing excess Bi contents BLT thin films, the films showed good permittivity, leakage current density and fatigue endurance.
CP-1-12 High Rate Deposition of MgO Films by Reactive Magnetron Sputtering with Additional Electron Emission K.H. Nam, J.G. Han (Sung Kyun Kwan University, Korea) MgO films are well known to exhibit high secondary electron emission, excellent high temperature chemical stability, high thermal conductance and electrical insulating properties. For these reason MgO films have been widely used for a buffer layer of high Tc superconducting and a protective layer for AC-plasma display panels to improve discharge characteristics and panel lifetime. Up to now MgO films have been synthesized by E-beam evaporation, Molecular Beam Epitaxy (MBE) and Metalorganic Chemical Vapor Deposition (MOCVD), however there have been some limitations such as low film density and a difficulty of large area coatings. Recently, therefore, reactive magnetron sputtering with Mg target was emerged as predominant method to synthesis high density and large area MgO films. However extremely low deposition rate of about 10nm/min is one of the major weak point to deposit MgO films by reactive magnetron sputtering due to severe poisoning ratio. In previous works, MgO films were synthesized by cross-field unbalanced magnetron sputtering with additional electron emission to increase deposition rate by reducing poisoning ratio. As cross field and electron emission were employed to magnetron discharge, poisoning ratio was dramatically reduced and deposition rate of MgO films was increased at 2.5 times (22nm/min) compared to that deposited by general magnetron sputtering. Furthermore, an attachment of cross field and electron emission lead to the decrease of surface roughness and the increase of average grain size and transmission coefficient. In this study, plasma states were investigated by langmuir probe and Optical Emission Spectroscopy(OES) in order to identity the mechanism for the effect of cross field and electron emission. Microstructure and secondary electron emission coefficient were analyzed by X-Ray Photoelectron Spectroscopy(XPS), Transmission Electron Microscopy(TEM) and γ-Focused Ion Beam (γ-FIB).
CP-1-13 Effects of Drying Temperature on the Crystallization of YMnO₃ Thin Films Prepared by Sol-Gel Method Using Alkoxides C.I. Kim, J.H. Park, K.T. Kim (Chung-Ang University, Korea) YMnO₃ thin films are excellent dielectric materials for high integrated FRAM because YMnO₃ have a relatively low permittivity (εr=20) and do not include volatile materials such as Pb and Bi which easy diffuse into the Si substrate and lead to point defects. In this study, we deposited YMnO₃ thin films on the Pt/Ti/SiO₂/Si substrates by sol-gel process using alkoxides. The YMnO₃ thin films spun-coated and then dried on hot plates from 250 °C to 450 °C. These coating and heat treatment were repeated 10 times to obtain film thickness of 3000Å. The prepared YMnO₃ thin films are annealed in O₂ atmosphere at 850 °C for 1 h. The crystal structure of YMnO₃ dried at different temperature was investigated using glancing angle XRD (θ = 0.1 ~ 2°). From the result XRD analysis, the crystallization of YMnO₃ thin films depend on dry temperature. The surface and cross-sectional morphologies of YMnO₃ were investigated using atomic force microscopy (AFM) and scanning electron microscopy (SEM). The changes of chemical states of YMnO₃ were investigated by x-ray photoelectron spectrometry (XPS).
CP-1-14 Preparation and Properties of Monolithic, Multi-Component and Nanolaminate Oxide Films of Ti, V and W M.S. Wong, H.M. Yang, H.C. Chen (National Dong Hwa University, Taiwan, ROC) This paper studies the structure and properties of monolithic layer, multi-component and nanolaminate oxide films of Ti, V and W prepared by reactive vapor deposition methods. It also determines the relationships among processing methods and the film microstructure and properties and facilitates the understanding of property enhancement observed in these films. The photo-catalysis, gas-sensing and electrochromic properties of these films are exploited. Ion-assisted, high-rate, reactive dc magnetron sputtering and e-beam evaporation techniques combined with innovative methods and processing strategies are used to deposit and to engineer the oxides for the intended applications.
CP-1-15 Silicon Rich Silicon Oxynitride Films for Photoluminescence Applications. M. Ribeiro, I. Pereyra (Escola Politécnica da USP, Brazil); M.I. Alayo (Laboratório de Microeletrónica, Brazil) The great advance in integrated optoelectronics has originated increasing interest in the search for photoluminescent materials compatible with silicon processing technology. Research dealing with porous silicon and silicon nanoparticles embedded in silicon dioxide for device applications as photodiodes and semiconductor lasers^1,2,3,4 follows this trend. In previous works we studied the production and characterization of silicon oxynitride films deposited by the PECVD technique from N₂O and SiH₄ gaseous precursors. The results showed that by the appropriate choice of the deposition conditions it is possible to transit from stoichiometric silicon dioxide to silicon rich silicon oxide⁵. In this work we study the effect of vacuum thermal annealing of these PECVD films for different temperatures and annealing times. The results show that the annealed films present photoluminescence attributed to the segregation, during the annealing process, of silicon clusters of nanometric size¹. These clusters are embedded within a wide gap dielectric matrix of silicon oxynitride. The formation of the silicon clusters and the crystallization with further heat treatments was monitored by Raman spectroscopy. Photoluminescence studies were performed from 7K up to 300K utilizing a 325 nm He-Cd laser as excitation source. It was verified that the samples exhibit luminescence bands in the 650 nm to 800 nm wavelength range with characteristics varying according with the deposition conditions and annealing processing. ¹ L. Pavesi, L. Dal Negro, C. Mazzoleni, G. Franzo and F. Priolo. Nature 408 (2000) 440. ² M.A. Green, J. Zhao, A. Wang, P.J. Reece, and M. Gal. Nature 412 (2001) 805. ³ M.J. Caldas, Phys. Stat. Sol. (b) 217 (2000) 641. ⁴ T.S. Iwayama, D.E. Hole, I.W. Boyd, Microelectronics Reliability 40 (2000) 849. ⁵ M.I. Alayo, I. Pereyra, W.L. Scopel, M.C.A. Fantini, Thin Solid Films, in the press.
CP-1-16 Thin Metal Film Simulation for Advanced Devices L. He (San Jose State University) Low temperature (LT) process on metal thin film has been proven effective to increase device Schottky barrier height and reduce contact resistance, both significantly. To further study the potential application of LT thin metal film in semiconductor devices, a computer simulation program is developed. Computer simulation for semiconductor devices and process is becoming more and more important due to the high cost of device fabrication and processing. In recent years, semiconductor device and circuit has undergone explosive growth. This growth has fueled a vast expansion of device modeling and simulation. Metal-semiconductor-metal photodetectors are widely used in the optoelectronic integrated circuit receivers because of their compatibility with the preamplifier for their planar integration scheme, the minimum number of processing steps, high performance, and low cost. InGaAs/InP is chosen for the long wavelength application. Analysis models based on the results of computer simulation will be presented in this work. It is believed that the LT process could greatly enhance the performance of a semiconductor photodetector.
CP-1-17 Transmission Electron Microscopy and Ion Beam Analysis of DC-Sputtered AlN Films A. Mahmood (CCMC-UNAM, Mexico); S. Muhl (IIM-UNAM, Mexico); R. Machorro, J. Heiras, O. Contrera (CCMC-UNAM, Mexico); E. Andrade, J. Carlos (IF-UNAM, Mexico) Aluminium Nitride, AlN, is an attractive material for various electronic and opto-electronic applications in the semiconductor industry. Good quality AlN films have been prepared using the reactive magnetron sputtering (RMS) technique. The deposition parameters, substrate temperature, plasma current, working gas composition ratio (Ar/N₂), gas pressure in the deposition chamber and the deposition time, have been varied over a wide range. The film structure and morphology has characterized by XRD, transmission electron microscopy (TEM), Rutherford Backscattering (RBS) and complemented by scanning electron microscopy (SEM), atomic force microscopy (AFM), spectral ellipsometry and FTIR spectroscopy. TEM analysis revealed a columnar structure growth when films are deposited at low plasma currents whereas highly crystalline films are obtained at high plasma currents. For ion beam analysis, Rutherford Backscattering (RBS) technique was employed, by bombarding the deposits with a low energy deuterium beam, to determine the atomic density per unit area (atoms/cm₂) and composition of the films. It is observed that high density films with composition close to 1:1 stoichiometry can be produced at low nitrogen concentration and high plasma current..FootnoteText This work was supported partially by DGAPA-UNAM through Proj. IN110800.
CP-1-18 Effects of Tantalum-ruthenium Oxide Passivation Layer in Organic Electroluminescence Display. S.-M. Jeoung, D-W. Han, H.-K. Baik (Yonsei University, Korea) Ta-RuO₂ film was used to protect the Organic Electroluminescence Display(OELD) from the humidity and oxygen. The Composition of Ta-RuO₂ film was changed by the variation of RF power. Film properties were examined by X-ray diffractometer, X-ray photoelectron spectroscopy, and Atomic force microscopy. It was found that the lifetime of the OELD increased and dark spots were not appeared when Tantalum to Ruthenium fraction is unity. It is believed that the strong bonding force of Ta-O and Ta-Ru-O and amorphous film structure restrain the permeation of humidity and oxygen to cathode.
CP-1-19 Characteristics of Indium Tin Oxide Thin Films Deposited by a Large Area Square Oxygen Ion Beam Assisted Evaporation at Room Temperature J.W. Bae, S.D. Park, G.Y. Yeom (Sungkyunkwan University, Korea) Indium oxide (IO) and indium tin oxide (ITO) thin films were deposited on polycarbonate substrates at room temperature by a square oxygen beam assisted evaporator system. Using this system, the effects of operational parameters of the system and the composition of the evaporation source on the composition of the film, electrical and optical properties, and surface morphology of the IO and ITO were investigated. The various tin composition of the source was fabricated by mixing indium oxide and tin oxide(0 wt.% ~ 30wt.%) using a ball-mill for 24 hours in ethanol, drying at 50C for several hours in a dry oven followed by sintering at 1500°C for 10 hours under atmospheric condition. The oxygen ion gun mounted in the chamber consist of two square grids, rf inductively coupled plasma source, and magnets to enhance the plasma density. The flux of the ion beam has made to be square and linear because the square shape is more useful in the roll-to-roll type large area deposition system. Atomic percentages of tin in the deposited IO and ITO thin films were investigated by X-ray photoelectron spectroscopy. Carrier density, resistivity, and Hall mobility changed with the doped tin concentration were measured by Hall effect measurement. Sheet resistance and optical transmittance were observed by a four point probe and an UV-spectrometer, respectively. The optimum deposition conditions of O/In compositions of pure and doped indium oxide films was made by controlling the ratios between oxygen ion bean flux to the substrate and evaporated source flux. At the conditions, all films have resistivity less than 7x10^-4 ohm-cm, Hall mobility of from ~20 cm²/Vs to 40 cm²/Vs, and transmittance more than 90% at 550nm.
CP-1-20 Optical Properties of β-FeSi₂ Films by First Principles Calculations A. Yoshida, A. Wakahara (Toyohashi University of Technology, Japan) Semiconducting β-iron disilicide is one of the most promising candidates in the next semiconductor optoelectronic materials because of the non-toxicity and abundant resources. Also Fe and Si are easily re-used and compatible with the standard Si technology. The bandgap at room temperature is favorable to optoelectronic devices with the minimum-absorption window of silica-based fibers and solar cells. Although a large number of research reports were published, the various properties are still controversial. The quasi-direct bandgap structure has been proposed, but it is believed to be sensitive to the strain inside the samples. In this report, we calculated the band structure and optical constants of strained β-FeSi₂ films deposited on Si substrates on the basis of the density functional theory. The software package of CASTEP was accepted, and we obtained the band structure and the complex refractive index (n,k) and the reflectivity (R). Recently, A.B.Filonov et al. [J.Appl.Phys.,83(1998)4410] published the dielectric functions and other optical properties of single-phase crystalline β-FeSi₂ films grown epitaxially on the Si(100) substrates up to 5eV over the fundamental edge. The stress and strain are easily introduced in this heterostructure. In our calculation the band structure is strongly affected with the applied direction of the strain, and β-FeSi₂(100)/Si(100) pseudomorphic layer is predicted to be of direct transition. The optical behaviors of β-FeSi₂ layer on Si substrate were compared with the calculated results.
CP-1-21 Atmospheric Pressure Chemical Vapor Deposition of Metal Doped Vanadium Oxides. T.D. Manning, I.P. Parkin (University College London, United Kingdom) The reaction between VCl₄ and an oxygen source (water, methanol, ethanol and ethyl ethanoate) was used to prepare thermochromic vanadium(IV) oxide thin films by atmospheric pressure chemical vapour deposition (APCVD). The custom built CVD rig allowed the introduction of a third precursor into the system to enable the doping of the VO₂ films with metal ions. It is known that doping of VO₂ with some metal ions (e.g. W⁶⁺, Nb⁵⁺) reduces the monoclinic to tetragonal phase transition temperature, a desirable effect for their use as solar control coatings. The optical and surface properties of the films were examined in order to assess their usefulness as intelligent thermochromic coatings.
CP-1-22 Characterization on the Luminescence Properties of Nanocrystals and Radiative Defects in SiO_x Films Deposited by rf Sputtering H.S. Bae, S. Im, T.G. Kim, C.N. Whang (Yonsei University, South Korea); J.H. Song, J.S. Yun (Korea Institute of Science and Technology, South Korea) Thin SiO_x layers were fabricated on the p-Si substrates at room temperature by rf magnetron sputtering to obtain Si nanocyrstals and radiative defects. The oxygen composition x and the thickness of the deposited layer were determined to be 1.4 and 180nm by Rutherford backscattering spectrometry (RBS), respectively. After deposition, the samples were annealed in N₂ ambient for 4 hours at 1100°C to obtain Si nanocrystals. The postannealed film shows red photoluminesce (PL) while the as-deposited one does blue PL. Since the red PL is known to signify the presence of Si nanocrystals while the blue PL is due to radiative defects in SiO_x, it is thought that the high temperature annealing leads to the nanocrystal formation of excess Si atoms in SiO_1.4. In the present work, we also fabricated Au/SiO_x/p-Si(MIS) structures for electroluminescence (EL) measurements. The electrical and EL properties of the MIS structures with the SiO_x layers containing Si nanocrystals and radiative defects will also be discussed in detail.
CP-1-23 Red Electroluminescence Emitted from Thin SiO₂ Implanted by Ge Ions H.S. Bae, S. Im, W.S. Lee (Yonsei University, South Korea); J.H. Song (Korea Institute of Science and Technology, South Korea) Ge ions of 80 keV were implanted with doses of 1x10¹⁶ cm^-2 and 5x10¹⁵ cm^-2 into a 120 nm-thick SiO₂ layer on p-Si at room temperature. Postannealing was subsequently performed at 500°C and 1100°C , to obtain radiative defects and Ge nanocrystals from the SiO₂ respectively. Violet photoluminescence (PL) and intense red electroluminescence (EL) were observed in an ambient light condition from the samples annealed at 500°C . The samples annealed at 1100°C do not show any physical sign implying the presence of the Ge nanocrystals in both PL and EL spectra. Even though, Raman spectra exhibit the signals of Ge nanocrystals embedded in SiO₂ matrix. The strong EL is observed only when a reverse bias is applied to a Au/Ge-implanted SiO₂/p-Si. The EL and carrier tranport mechanisms will also be discussed.
CP-1-24 Particle Size Effect on the Nonlinear Optical Characteristics of Polyimide/TiO₂ Nanocomposite Films P.-C. Chiang, W.-T. Whang (National Chiao Tung University, Taiwan, ROC) A method has been developed to prepare polyimide/TiO₂ hybrid films without adding chelating agents. In this study, the acid groups of the poly(amic acid) (PAA) are used as the in-situ catalyst to promote the formation of TiO₂ crystal. The poly(amic acid) are derived from 4,4 ’-oxydiphthalic anhydride (ODPA) and 4,4’-diaminodiphenylether (ODA). The precursors of hybrid films are synthesized by reacting a mixture of PAA with Titanium(IV)oxy acetylacetonate (TiO(acac)₂). The metal-containing precursors are converted to PI/TiO₂ hybrid films by step thermal imidization. The formation of TiO₂ is characterized by X-ray diffraction (XRD) and Fourier transform infrared (FT-IR). The thermal properties of the hybrid films are measured by thermogravimetric analysis (TGA). The morphology of hybrid films is further investigated by TEM and SEM. The conductivity of the hybrid films can be higher than corresponding pure polyimide.

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