Symposium C Poster Session

Tuesday, May 1, 2001 5:00 PM in Room Atlas Foyer

CP-1-1 Deposition of Lanthanum Selenide Thin Films by Spray Pyrolysis Technique
G.D. Bagde, C.D. Lokhande (Shivaji University, India)
Lanthanum selenide thin films have been deposited onto preheated glass substrates by spray pyrolysis technique. The preparative parameters (conditions) were optimized to get good quality lanthanum selenide thin film. The films are uniform and adherent to the substrates. The films were characterized for structural, surface morphological, optical and electrical properties. The XRD study reveals that the films are polycrystalline. The optical absorption study reveals that the films hav direct band gap of 2.2 eV. SEM pictures showed that the substrate is well covered no cracks or pinholes were observed. The electrical resistivity was found to be of the order of 10@super 4@ @ohm@cm by thermo-emf measurement of lanthanum selenide is of p-type conductivity.
CP-1-2 Characterization of Alq3 fFlms Grown by Ionized-Cluster-Beam-Assisted Deposition, Neutral-Cluster-Beam Deposition and Thermally Evaporated Deposition
S.Y. Kim, S.Y. Ryu, J.M. Choi (Yonsei University, Korea); D.S. Choi ( Kangwon National University, Korea); S. Im, C.N. Whang (Yonsei University, Korea)
The 8-hydroxyquinoline aluminium (Alq3) is one of the high efficient light emitting organic materials by proper stimulations. We have grown Alq3 films on silicon substrates by several methods, i.e. neutral-cluster-beam deposition (NCBD), and thermally evaporated deposition ionized-cluster-beam-assisted deposition (ICBAD) technique with variation of the deposition parameters such as ion current and acceleration voltage. And we measured photo-luminescence (PL) of the films. We found there seemed to be optimum conditions in the film growth for the higher PL intensity. As the acceleration voltage was increased, PL intensity was decreased. But the NCBD films showed highest PL intensity among others. The films were characterized by Low angle X-ray diffraction (LXRD), atomic force microscope (AFM), X-ray photo-emission spectroscopy (XPS), fourier transform infra-red spectroscopy (FT-IR), and packing density measurement of the films. The film thickness and qualitative film roughness were measured by LXRD. AFM was also used to measure surface morphology and root-means-square (RMS) roughness. We confirmed cluster formation in the films obtained from the ICBAD and the NCBD by ex-situ AFM observations of intial film growth. XPS and FT-IR were used to see chemical binding of Alq3 molecules in the films. In the present work, he measured PL data as a function of the deposition parameter will be interpreted in detail based on the results of film characterizations.
CP-1-3 Improvement of Optoelectronic and Thermal Properties of Multi-Layered VO@sub x@ Thin Films as an IR Active Layer for Microbolometer
H.K. Kang (Korea Institute of Science and Technology); C.W. Park, S. Moon (Korea Institute of Science and Technology, Korea); T.H. Kim (Yonsei University, Korea)
Multi-layered VO@sub x@ films were fabricated on insulating SiN@sub x@ layer by r.f. sputtering at room temperature and its TCR (temperature coefficient of resistance) and thermal conductance were measured as an IR active layer for microbolometer. Metal vanadium and vanadium oxide were alternatively deposited and annealed under 300@super o@ Celsius to control phases and compositions of mixed VO@sub x@ films by different oxygen diffusion condition due to changing deposited film thickness variation. Phases and composition were easily controlled by multi-layer deposition technique without any extra ion-beam apparatus. Optoelectrical property and thermal property were directly affected by changing phase and composition of mixed VO@sub x@ film and they were easily controlled by this method to improve IR sensitivity of microbolometer. Electrical measurement was performed by using Van der Pauw 4-poing resistivity technique. Resistivity of samples was measured as a function of temperature from 20 to 80 @super o's@ Celsius. TCR value was obtained from slope of Temperature vs. reistivity plot. Higher TCR value and lower resistivity of VO@sub x@ film can improve microbolometer characteristics. Compared to single layer deposition, We obtained over 2% TCR value with a few ohm resistivity by multi-layer deposition. Also, we obtained wider range of TCR value at same resistivity and steeper slope of TCR vs. resistivity plots. Thermal conductance of VO@sub x@ films was measured to evaluate the total thermal conductance(G) and time constant (@tau@) of microbolometer by the 3-@omega@ method. The 3-@omega@ method is to attain thermal properties from frequency component related to the temperature change of thermal resistor line on the thin film surface when current flows through thermal resistor line by variable frequency-current source. Measurement of thermal properties of VO@sub x@ film makes it possible to achieve more exact thermal design and good thermal isolation of microbolometer.
CP-1-4 Preferential Orientation Control of Crystallites in DC Reactive Sputtered AlN Films
A. Mahmood (Universidad Nacional Autonoma de Mexico); S. Muhl (Instituto de Investigaciones en Materiales, UNAM, Mexico); J. Heiras, R. Machorro (CCMC-UNAM, Mexico); E. Andrade (Instituto de Fisica-UNAM, Mexico)
AlN films have been prepared by DC reactive magnetron sputtering technique and characterized by structural, compositional and optical techniques. To optimize the quality of the films the following deposition parameters were varied: substrate temperature from 200 to 700°C, working gas composition ratio of Ar/N2 from 80/20 to 20/80, and plasma current from 0.2 to 0.50 Amp. After optimizing the deposition parameters it was observed, by X-ray analysis, that the preferred orientation of the AlN crystallites could be controlled by the deposition parameters. Similarly, by changing the plasma current it was possible to modify the grain size and texture of the AlN films. The microstructure of the films was determined by TEM and SEM. Rutherford backscattering analysis showed that stoichiometric films can be produced with nitrogen gas concentrations of less than 50%. The dielectric function in the visible range, the absorption spectra and the band gap were determined by Ellipsometry. Finally, surface analysis was carried out using X-ray Photoelectron Spectroscopy (XPS) to study the bonding nature and chemical states in the film.
CP-1-5 Effect of Plasma Treatment with Different Gases on the Mechanical Properties of Plasma-Polymerized Thin Films and Bulk Polymers
F. Benitez (Universitat de Barcelona, Spain); M. Galan, J. Serrat (TELSTAR SA, Terrassa, Spain); E. Martinez, J. Esteve (Universitat de Barcelona, Catalunya, Spain)
Plasma-polymerized hexamethyldisiloxane thin films (PPHMDSO) and bulk polycarbonate samples have been modified by immersion in different plasmas. The mechanical performance of polymeric materials may be significantly improved by ion implantation, but also by bombardment with low energy ions. It is the aim of this paper to analyze the effect of treatment with different gases on the chemical, structural, optical and mechanical properties of both PPHMDSO thin films and commercial polycarbonate samples. Experiments were carried out using oxygen, nitrogen, air and argon. The samples were characterized by atomic force microscopy (AFM), near-grazing-angle reflective Fourier transform infrared spectroscopy (FTIR), UV-vis and IR ellipsometry, X-ray photoelectron spectroscopy (XPS), drop shape analyser (DSA), nanoindentation and microscratch techniques. In general, plasma modifications lead to further cross-linking within a surface region, which results in harder, wear resistant, hydrophilic surfaces. It is found that the mechanical properties of the modified zones are better tested with sharp indenters (corner cube) than with blunt ones (spherical) and that excessive modification of the samples renders highly stressed surface layers, which may be detrimental to their use in industrial applications.
CP-1-6 Investigation into the Properties of Titania Deposited Using Pulsed, Dual Bipolar, Reactive, Unbalanced Magnetron Sputtering: Variation with Magnetic Field Arrangement
J. O'Brien, P.J. Kelly (University of Salford, United Kingdom)
Investigations have been made into the effect of variation in the degree of balance and field strength of magnetron magnetic field on the properties of titania deposited using vertically opposed unbalanced magnetrons operated in the pulsed dual cathode mode. Magnetic field configuration was varied with the aid of Gencoa Vtech variable magnetrons. These magnetrons allow in situ variation of magnetic field via the independent linear positioning of the inner and outer array of magnets. This allows field variations from nearly balanced to highly unbalanced, which may be set prior to or during the deposition process. The deposition process is operated in the dual bipolar pulsing (DBP) mode as this is well proven for its ability to enable arc-free, stable, long-term deposition, and DBP itself is also being characterised in the broader aims of this study. Other parameters such as pulse frequency (200 kHz), coating pressure (1.25 mTorr) and nominal target current (4A) were not varied. Average ion currents have been measured under each condition. In addition, current and voltage waveforms at the target and substrate were obtained and analysed. Titania films were deposited and investigated in terms of structure, defect density, composition, argon content, crystal structure and optical and tribological properties.
CP-1-7 The Surface Properties of Non-Polar Materials are Changed Permanently by Hydrophilic Plasma Thin Films
E.M. Moser (EMPA, Switzerland); G. Henrion (CNRS UPRESA, France)
The hydrophobic properties of polyolefins often prevent a good adhesion to more polar materials. Hitherto, plasma pre-treatments have been widely used to obtain a polar surface right before processing the printing, laminating or metallization. However, the long term stability of the surface properties can be obtained by fixation of the functional polar groups onto the surfaces due to tailored plasma processes.@paragraph@We have, therefore, developed ultrathin hydrophilic plasma layers@footnote *@ - with a surface tension of up to 63 mN/m - which can be deposited onto non-polar surfaces of materials or onto the hydrophobic plasma diffusion barrier layer@footnote *@. The processes have been studied by optical emission spectroscopy in order to correlate their characteristic mechanisms with contact angle measurements. Furthermore, the functional testing has been combined by investigating the chemical composition of the thin films using x-ray photoelectron spectroscopy and FT-infrared spectroscopy. As a result, the polar surfaces adhere well to a variety of materials: it can be printed with aqueous inks or paints and vacuum metallized. The hydrophilic coatings are also transparent, colourless, taste neutral, chemically resistant, and show non-fogging properties. Long term behaviour tests have shown that the functional properties of the plasma polymerised thin films are permanent for years.@footnote@ *patent applied for.
CP-1-8 Deposition of Gradient Mo-Al@sub 2@O@sub 3@ Spectrally Selective Sputtered Coatings
V. Teixeira (University of Minho, Portugal); C. Nunes (Insituto Nacional de Engenharia e Tecnologia Industrial, Portugal); M.F. Costa (University of Minho, Portugal)
Efficient solar photothermal benefits from spectrally selective absorber surfaces. Most solar selective coatings use metal-dielectric composites, known as cermets, as the absorber of solar energy. In this contribution we study the microstructure, the crystalline structure and the optical properties of composite ceramic-metal thin coatings deposited on glass and copper substrates. The selective gradient coatings were produced by reactive DC magnetron sputtering of aluminium and molybdenum targets in a plasma of argon-oxygen at different sputtering pressures and substrate temperatures for a constant target current, substrate bias and substrate-target distance. The graded coatings consist in a series of layers, each having different thickness and metal content in the dielectric matrix. The coating thickness and microstrucuture were studied by scanning electron microscopy (SEM). The surface roughness was analysed by atomic force microscopy (AFM) and by a non-contact laser triangulation system. The chemical composition of the sputtered cermet coatings was analyzed by X-ray photoelectron spectroscopy (XPS) and energy dispersive x-ray microanalysis (EDX). X-ray diffraction analysis was carried out to determine the degree of crystallinity and crystalline structure of the produced thin coatings. Spectral reflectance in the visible and near infra-red of the deposited cermet Mo-Al2O3 films was measured using a double-beam spectrophotometer. From the optical data we extracted a solar absorptance of 0.90-0.96 and a corresponding thermal emittance of 0.10-0.04, depending on the sputtering deposition conditions and thicknesses and composition of each layer in the multilayer absorber structure.
CP-1-9 Characterization of Thermally Evaporated 1,8-diacetoxy-9,10-Anthraquinone Films
A. Mahajan, R.K. Bedi, Unknown Pramila, S. Kumar (Guru Nanak Dev University, India)
1,8-Diacetoxy-9,10-anthraquinone compound have been synthesised and its films are prepared by thermal evaporation technique onto the glass substrate kept at different temperatures in a vacuum of 10@super -5@ torr. The experimental conditions are optimised to obtain better crystallinity of the films. The films so prepared have been studied for their structural, electrical and optical properties. @paragraph@ The comparison of infrared (IR) spectra of 1,8-diacetoxy-9,10-anthraquinone and its films show that the compound remains unaffected during vacuum deposition and annealing processes. Observations reveal that the crystallinity of the film increases with increase in substrate temperature. Crystallites as large as 1.8µm are observed in the case of films deposited at 333K. The current-voltage (I-V) characteristics of films show ohmic behaviour of conduction within the investigated field and temperature range (10-60V, 300-400 K ). The conduction appears to take place by thermally activated hopping above intermolecular barriers. The electrical conductivity and carrier concentration of film increases with the increase in temperature , while the drift mobility decreases. Analysis of optical absorption measurements on the films indicate that the interband transition energies lie in the range 2.5-3.5 eV.