ICMCTF1999 Session CP: CP Posters

Tuesday, April 13, 1999 5:00 PM in Room Atlas Foyer
Tuesday Afternoon

Time Period TuP Sessions | Topic C Sessions | Time Periods | Topics | ICMCTF1999 Schedule

CP-1 Substrate-Induced Properties of a Ferroelectric Thin Film
S.B. Rochal (Rostov State University, Russia); L. Lahoche (University of Picardie, France); V.L. Lorman (University of Amiens, France); J.M. Roelandt (University of Compiegne, France)

We propose a phenomenological model which describes the ferroelectric film formation on the oxide substrate and its dielectric, optical and mechanical behavior. The model delineates the stability regions of different ferroelectric domains1 formed during the deposition process and shows their relation with the superstructure imposed to the film by the substrate. The approach contains detailed crystallographic analysis and thermodynamic consideration including thermo-electro-mechanical coupling. It also takes into account the epitaxial relationship between the film and the substrate, the mechanical boundary conditions and the surface morphology. Calculated theoretical phase diagram shows the predominance regions of the structures with different polarization orientation with respect to the substrate surface. The model is applied to the case of the epitaxial PbTiO3 thin films which are grown on the MgO(100) single-crystal substrate. A numerical modeling of the stress level in the film is performed. Its influence on the dielectric and optical properties is discussed.

1B.S. Kwak and al, Physical Review B, 49, 21, (1994) 14865

CP-2 TheOptical and Secondary Electron Emission Properties of Mg-O-Cs Thin Films are Prepared by Ion Beam Assisted Deposition
S.J. Rho, S.M. Jeong, H.K. Baik (Yonsei University, Republic of Korea)
AC- plasma display panel (AC-PDP), novel types of flat panel display, are using dielectrics and dielectric protection layers for the improvement of efficiency unlike DC-plasma display panel (DC-PDP). The dielectric protection layer acts to protect the electrode and the dielectric from bombardments of ions, electrons, photons, and metastable atoms. The requirements for the dielectric protection layer are long time stability in the plasma, high secondary electron emission property, and good transparency. So far, many researches have been made for the development of high efficiency dielectric protection materials including, Al2O3, La2O3 and CeO2, and, it is known that MgO is the best candidate for the dielectric protection material. MgO is a highly ionic crystal with the Mg-O bonds having about 80% ionic character and it's secondary electron emission coefficient is as 17, much higher compared with that of Al2O3, a value of 3.2. But MgO is not fit for commercial products, because of the low efficiency. We investigate on the Mg-O-Cs system to improve the secondary electron emission property. Cs is known as a low electron affinity material that lowers the electron affinity below that of the base material. Mg-O-Cs is deposited on the glass substrate by IBAD (Ion Beam Assisted Deposition). MgO is e-beam evaporated and Cs is thermal evporated under Ar and/or O2 ion beam bombardment. The XRD, AES, XPS and secondary electron emission analysis are used for Mg-O-Cs property characterizing. The transparency of Mg-O-Cs increases above that of MgO and it's crystal structure is the same as MgO.
CP-3 Properties of Indium Tin Oxide Films Fabricated by Ion Beam Assisted Evaporation
J.W. Bae, N.E. Lee, G.Y. Yeom (Sungkyunkwan University, Korea)

Transparent conductive thin films have been studied by many research workers because of their wide industrial applications. In recent years, the application of these thin films can be summarized into optical transparent electrodes in display devices, photovoltaic cells, and other opto-electronic devices. Many new materials and various manufacturing techniques have been developed to satisfy technological requirements.

The most widely used materials for the transparent electrodes are semiconducting oxides such as zinc oxide(ZO), tin oxide(TO), and indium tin oxide(ITO). Among these transparent oxides, ITO has the highest electrical conductivity and optical transparency.

The development trends for ITO coating techniques can be integrated into the decrease of operation temperature to use various materials as the substrates. ITO has been produced by a number of techniques such as DC (or rf)- sputtering, chemical vapor depositionCVD, evaporation, etc. In particular, ion beam assisted electron beam evaporationIBAE technique offer room temperature operation in addition to the flexibility in controlling film properties. In this IBAE technique, the establishment of the deposition parameters such as the flux and energy of oxygen ion beam, incident angle of the ion beam, ITO/O2 flux ratio, etc. is very important to obtain optimal ITO film at the room temperature.

In this study, the effects of the deposition parameters such as the flux and energy of oxygen ion beam, incident angle of the ion beam, and evaporated ITO/O2 ion beam flux ratio on the physical, optical, and electrical properties of ITO films deposited on the plastic substrates at the room temperature were investigated.

CP-4 Protective Coatings for Brewster-angle Windows
G.I. Surdutovich, R.Z. Vitlina, V. Baranauskas (State University of Campinas, Brazil)
Any protective coating worsens to some extent the optical properties of the coated object. This is also related to Brewster-angle windows since the null reflectivity at the Brewster angle is a property of a flat surface between two lossless dielectrics. Therefore, it is impossible to retain the Brewster angle properties of the substrate for any isotropic film-covered substrate. It is possible, however, to design some special anisotropic coatings deposited onto Brewster windows for which both the position of the Brewster angle and the true zero of the reflection factor remain unchanged. This approach is based on using an additional parameter of the film, uniaxial anisotropy, to make both the reflection coefficients (ambient-film and film-substrate interfaces) for the p - polarized light zero. It is sufficient to arrange a certain relationship between the horizontal epsylonxx and perpendicular epsylonzz components of the dielectric permittivity tensor of the film and the dielectric constant epsylon of the substrate to obtain a protective coating which does not deteriorate the quality of the Brewster window. This condition can be satisfied in two regions: under the constraint epsylon < epsylonxx < epsylon + 1 (positive anisotropy) and epsylonxx < epsylon (negative anisotropy) . This formal solution has only a limited value since usually there are no suitable material with the prescribed anisotropy. But one may design a thin layered structure with the required effective dielectric tensor. Such an anisotropic film may be realized in the form of a multilayer two-component structure. The parameters of the structure (the dielectric permittivities of the components and their concentrations) are calculated. Two examples of the anisotropic protective coatings are presented for a ZnSe window (epsylon = 5.76). The optical quality does not depend on the film thickness. This makes the coatings less sensitive to surface damage. These protective multilayered anisotropic coatings may be useful in applications of Brewster angle windows within powerful lasers, where the problem of the resistance of the window to the environment is critical.
CP-5 IR Ellipsometric Studies of the Metallic Surfaces After High-Dose Ion Implantation
L.V. Poperenko (Kyiv Taras Shevchenko University, Ukraine); A. Roeseler (ISAS - LSMU, Berlin,, Germany); M.V. Vinnichenko (Kyiv Taras Shevchenko University, Ukraine)
Modern applied physics as well as industry requires reliable data on optical properties of the metallic coatings produced by ion irradiation with entirely new technical parameters (e.g. corrosion/erosion resistance, surface conductivity etc.). Therefore the main aim of present investigation was to clarify the nature of the metallic surface structure modification by high-dose ion implantation and ion plasma mixing. As ions source, the vacuum-arc large-aperture ion injector was utilized. The acceleration potential was 80 kV, the ion implantation dose 1017-1018 cm2. The samples of Mo, Al, Ta implanted by copper ions as well as of Mo, Ti and Fe50Ni50 implanted by mixed Ti+, C+ beam have been examined by means of the infrared Fourier transform spectroellipsometry realized in the Beattie-Conn fashion (2-25 µmm). The spectral dependencies of the phase shift Δ between the polarization vector orthogonal components and the tanΨ of the restored linear polarization azimuth Ψ were measured. On their basis in the effective medium approximation the spectral dependencies of optical constants (n, k), dielectric function (DF), reflectivity (R) and optical conductivity (OC) were calculated and analyzed. It has been observed essentially different spectral behavior of the optical parameters for metallic surface modified by copper ions in comparison with those modified by mixed Ti+ and C+ beam. The latter showed typical for unmodified metals Drudelike behavior of the OT and DF. Modification of Al, Mo and Ta by copper ions leads to completely different from Drude-like behavior of the optical properties that could be described in terms of the Kaveh-Mott equation. Reflectivity of the metals irradiated by copper ions is also significantly lower than R of the surfaces modified by Ti+, C+ mixed beam. It is evident that after the Cu+ ion implantation the effects of Anderson-like weak localization of electrons with energy in the vicinity of the Fermi level became significant.
CP-6 Polycrystalline Copper Nitride Films Deposited by the Low-Pressure RF Plasma-Chemical Reactor With Hollow-Cathode Supersonic Plasma Jet System
L. Soukup, M. Sicha, F. Fendrych, Z. Hubicka, L. Jastrabik, D. Chvostova, V. Studnicka (Institute of Physics, Academy of Sciences, Czech Republic); T. Wagner (Laser-Optik-Technologie ORIEL, Darmstadt, Germany)

The originally designed low-pressure RF plasma-chemical reactor with hollow-cathode supersonic plasma jet system (RPJ) has been used for deposition of polycrystalline copper nitride thin films.

From comparison of experimental values of chemical composition with the theoretical ones and from XRD analysis of the samples, which have been made at the RF power absorbed inside the RPJ reactor below approx. 75 W follows that the stoichiometric Cu3N films have been achieved. The typical value of the deposition growthrate was found in the order of 16 nm/min for RF power Pw = 40W. The optical energy gap Eg and microhardness H of the deposited Cu3N thin films increase with decrease of RF power. There are Eg=1.24 eV and approx. H=8.8 GPa for the sample deposited by RF power 40 W. For deposition RF power higher than approx. > 75W it appears that a small amount of Cu microparticles is diluted in the Cu3N film.

The relative high stability of Cu3N thin films which has been found for different environmental conditions together with relative high hardness indicate that the Cu3N thin films can be used not only in microelectronics for write-once optical recordingmedia, but for some application in the surfaces treatment technology, too. Especially the modificated RPJ with multi-jets system enables the deposition of Cu3N thin films onto internal walls of cavities, holes and on surface of complex shapes of hollow substrates.

Time Period TuP Sessions | Topic C Sessions | Time Periods | Topics | ICMCTF1999 Schedule