ICMCTF2002 Session C2-2: Film Properties/Structure/Deposition Process Relationships

Wednesday, April 24, 2002 1:30 PM in Room Sunset

Wednesday Afternoon

Start	Invited?	Item
1:30 PM		C2-2-1 Gas Barrier Properties of Ceramic/Polymer Nanocomposite Films. B.M. Henry, A.G. Erlat, C.R.M. Grovenor, G.A.D. Briggs (University of Oxford, United Kingdom); Y. Tsukahara (Toppan Printing Company, Japan) The resistance of transparent metal oxide layers deposited on flexible plastic substrates to oxygen and water vapour transmission is of immense importance to the food packaging and the flat panel display industries. Typically the thickness of the deposited ceramic is several orders of magnitude thinner that that of the polymer. It is apparent, nevertheless, that the gas barrier properties of these composite films are strongly dependent upon various aspects of the deposited metal oxide layer and have not been fully optimised. Factors such as defect type and density, the compaction of the oxide layer and the oxide chemistry dictate the rate at which gas permeates through these films. In this study a range of oxide coatings on PET has been microstructurally characterized using a variety of analytical techniques, including Rutherford backscattering, scanning electron microscopy and atomic force microscopy. The microstructure of the barrier layers has been correlated with measurements of the oxygen and water permeation of the composites.
1:50 PM		C2-2-2 Microstructure, Mechanical Properties and Tribological Behavior of Multilayered Nanocomposite Cr/C Thin Films X. Nie, Z.Q. Qi, E.I. Meletis (Louisiana State University) Pure chromium, carbon and Cr/C multilayer thin films were deposited on Si (100) wafers using an electron-beam physical vapor deposition (EB-PVD) method. The influence of the thickness of the laminated Cr and C layers on the microstructure and the properties of the thin films were studied by transmission electron microscopy (TEM), atomic force microscopy, nanoindentation, and pin-on-disc wear testing. It was found that carbon layer has a graphite-like structure where Cr layer has a nanocrystalline structure. Hardness and tribological behavior were found to be a function of C single layer thickness and volume fraction. The effect of layer thickness on the properties of these films is discussed in light of present evidence and previous results on multilayered nanocomposite films. Key Words: EB-PVD, Multilayer thin films, Nanoindentation, Tribology, TEM.
2:10 PM		C2-2-3 The Properties of Nanocomposite Aluminium Silicon Oxynitride Thin Films Deposited by Filtered Arc Process A. Bendavid, P.J. Martin (CSIRO, Australia); H. Takikawa (Toyohashi University of Technology, Japan) Thin films of aluminum silicon oxynitride have been deposited on conducting (100) silicon wafers by filtered arc deposition (FAD) under nitrogen and oxygen gas flow. The influence of the oxygen flow ratio, substrate types on the structure, mechanical and optical properties have been investigated. The results of X-ray diffraction showed that the film structure comprise of AlN crystallite with amorphous Si3N4 and SiOx . The optical properties over the range of 300 nm to 800 nm were measured using spectroscopic ellipsometry and found to be strongly dependent on oxygen flow ratio. The refractive index values of the films were found to be in the range of 2.2 to 1.63 at a wavelength of 670 nm for oxygen flow range of 0-100%. The hardness of the films was found to be strongly dependent on the oxygen content in the film. The hardness of the films ranged between 10-24 GPa. The refractive index of the films was to found vary linearly with the residual stress.
2:30 PM		C2-2-4 Stresses in Thin Metal and Oxide Films Deposited by the Metal-mode Reactive Sputtering Process G.J. Keller, F. Chauvet (Essilor International, France) Thin Zirconium, Niobium, Titanium and Silicon films as well as their corresponding oxides have been deposited in a commercially available sputter coating equipment. Circular planar DC magnetrons with 14 cm diameter targets have been used. The substrates were placed on a turning table of 50 cm diameter, rotating at 46 rpm. During every cycle half of a metallic mono layer was deposited; the total thickness was about 100 nm. The oxide films were obtained by oxidizing these metallic semi-layers separately in an oxygen plasma. Film stresses were measured as a function of the Argon pressure ranging between 0.2 and 0.9 Pa. At low deposition pressure all the evaluated materials are in a compressive stress state. At high pressure, almost all layers, except Silicon and its oxide and Niobium oxide, present tensile stress. The transition pressure depends on the atomic mass ratio of the target material and the working gas and for the pure metals it correspond to values reported in the literature. The compressive stress for the oxides deposited at low pressure is reduced compared to the non oxidized materials. This is due to the increased thickness from the oxidation. At high pressure the opposite effect is seen. As the layers are more porous, or less packed, oxygen is incorporated in the film and creates more compressive stress which reduces the tensile stress. More details concerning the correlation between intrinsic material parameters and the measured film stresses will be given.
2:50 PM		C2-2-5 Optimisation of Hard AR Coatings with Statistical Methods H. Zimmermann (Bl@aa O@sch Corp. Inc., switzerland) Antireflection coatings are preferably produced with high vacuum evaporation technology. However this technology is limited in certain film properties, like micro hardness, abrasion resistance and chemical stability. For applications with higher requirements of film hardness and abrasion resistance the sputtering technology is a good choice. The optimisation of sputtered films with regard to certain properties were mostly carried out with inefficient methods like variation of some parameters in a certain range. With the statistical expert system STAVEX the way to optimise certain film properties is much shorter. As an example the author shows how one can improve the quality of reactive sputtered silicon dioxide and nitride films with a limited number of experiments. With sixteen experiments and the variation of 6 process parameters (gas pressure, partial pressure of the reactive gas, power, frequency, distance target-substrate and substrate temperature)an optimum of abrasion resistance of the thin films on sapphire and glass substrate was found. With the mathematical model of STAVEX it is possible to calculate in advance certain properties of the films for a limited range of the parameters. The main parameters which influence the abrasion resistance are the distance target substrate, the power and the gas pressure. Minor influence has the pulse frequency and the substrate temperature.
3:10 PM		C2-2-6 Single Crystal Films of In₂O₃(ZnO)_m (m=integer) Natural Super Lattice Grown by Novel Solid-State Diffusion Technique H. Ohta (Hosono Transparent ElectroActive Materials, Japan); K. Nomura, K. Ueda (Tokyo Institute of Technology, Japan); M. Orita, M. Hirano (Hosono Transparent ElectroActive Materials, Japan); H. Hosono (Tokyo Institute of Technology, Japan) Single crystalline thin films of In₂O₃(ZnO)_m (m=integer) natural super lattice were grown by novel solid-state diffusion technique using epi-ZnO film as a solid template. A multilayered film composed of amorphous In₂O₃(ZnO)₄ and epi-ZnO was grown by a PLD technique at respective temperature of 25 and 800°C on YSZ (111) wafer. The multilayered film was annealed at 1450°C in air to grow super lattice film of In₂O₃(ZnO)₅ automatically. Sharp diffraction peaks due to satellites of super lattice were observed in high resolution XRD pattern of the resultant film. Super lattice structure was clearly observed by HREM, indicating that the film was a single crystal of In₂O₃(ZnO)₅.
3:30 PM		C2-2-7 Amorphous ITO Thin Films by DC Sputtering for Electrochromic Application V. Teixeira, H.N. Cui (Universidade do Minho, Portugal); L.-J. Meng (Instituto Superior de Eingenharia do Porto, Portugal); E.M. Fortunato (Universidade Nova de Lisboa, Portugal) Crystalline indium-tin-oxide (ITO) thin film has been found extensive applications in photoelectronics, but for an electrochromic device, amorphous ITO film is a good candidate too. It is because tungsten oxide (WO₃) film, one of the most studied electrochromic (EC) materials, is in amorphous phase with a better coloration efficiency and both the amorphous WO₃ and ITO films are more easy to be obtained in deposition. Though many deposition technologies have been used to fabricate ITO films, among the techniques available for ITO thin film production, sputtering is the most widely investigated and large-scale deposition set is available. In our previous and other author studies it has reported the preparation of high conductive ITO films using radio frequency (RF) sputtering. Here the ITO thin films were deposited on glass using DC-magnetron reactive sputtering at varied bias voltages and low substrate temperatures. Amorphous films were obtained. The comparing of ITO films has been done through adjusting the bias and temperature. There are some improvement about the film properties, microstructure and other characterisations in varied condition. The transmissions, absorption, spectral and diffuse reflection of ITO films were measured in some ranges of UV-vis-NIR. The sheet resistance, resistivity, carrier concentration and Hall mobility were compared and investigated by measurement and calculation. The thickness, refractive index (n) and the surface roughing of the film were derived from the measured spectra data. From atomic force microscopy and spectra calculation, surface roughness was analysed and in the coverage from 12.1 to 13.8 nm. The films exhibited high optical transmittance and conductivity.
3:50 PM		C2-2-8 Investigation of Annealing Effects on Sol-gel Deposited Indium Tin Oxide Thin Films in Different Atmospheres M.J. Alam, D.C. Cameron (Dublin City University, Ireland) Indium tin oxide (ITO) thin films have been deposited onto silicon and quartz glass substrates and also on titanium dioxide and tantalum oxide coated substrates by a sol-gel process, followed by annealing in air, oxygen and nitrogen. Effect of annealing in the temperature range of 400-700⁰C on the electrical, optical and structural properties of ITO thin films was studied. The starting solution was prepared by mixing indium chloride dissolved in acetylacetone and tin chloride dissolved in ethanol. 0-20 % by weight Sn-doped indium oxide (ITO) films were prepared by heat-treatment at above 400⁰C. The thickness of ITO film was measured by ellipsometer. The electrical resistivity was measured by using four-point probe method. The ITO thin films containing 10 wt.% Sn showed the minimum resistivity of 8.0x10^-4 Ω-cm annealed at 500⁰C in nitrogen. X-ray diffraction measurements employing CuKa radiation were performed to determine the crystallinity of the ITO films which showed that the ITO films were polycrystalline with a cubic bixbyite structure. The resistivity of ITO films deposited on titanium dioxide and tantalum oxide film has a minimum value of 9.5x10^-4 Ω-cm and 9.0x10^-4 Ω-cm respectively annealed at 500⁰C which have higher resistivity than that deposited on glass. The conductance versus thickness relationship for ITO shows that, when it is deposited on top of titanium or tantalum oxide, there is an interdiffusion layer of approximately 40 nm thickness. There is an affect of titanium and tantalum into the ITO layer up to approximately 40 nm and after that there is no interdiffusion between the conducting and insulating layer. So this combination of transparent conductive ITO thin films and titanium dioxide or tantalum oxide insulating layer can be used for thin film electroluminescent devices. The conductance versus thickness relationship for ITO shows that, when it is deposited on top of titanium or tantalum oxide, there is an interdiffusion layer of approximately 40 nm thickness. This combination of transparent conductive ITO thin films and titanium dioxide or tantalum oxide insulating layer may be used as part of thin film electroluminescent devices.
4:10 PM		C2-2-9 Manipulating Plasma Chemistry in Reactive Sputtering Processes with Helium Gas C. Muratore, J.J. Moore (Colorado School of Mines); J.A. Rees (Hiden Analytical Limited, United Kingdom) System power and process gas partial pressure are typically employed as extrinsic parameters to control plasma chemistry in reactive sputtering processes. We have observed through the use of a Hiden electrostatic quadrupole plasma (EQP) mass spectrometer coupled with an energy filter that the relative abundances and, in some cases, the energies, of the species arriving at growing titanium nitride and titanium oxide films can be manipulated by admitting small amounts (less than 20% of total gas flow) of helium to the processing chamber during sputtering. Additional reaction mechanisms resulting from helium metastable collisions with diatomic molecules and atoms are presumed to give rise to marked changes in the concentrations of various nitrogen or oxygen species. The changes in plasma chemistry have been found to have remarkable effects on the structure and/or properties of resultant thin film compounds which have been characterized by cross sectional transmission electron microscopy, atomic force microscopy, nanohardness indentation, X-ray photoelectron spectroscopy and other techniques.
4:30 PM		C2-2-10 Transparent and/or Conductive Thin Films of Ta-Doped SnO₂ and Sc₂O₃ by MOCVD Techniques Haydn Chen (City University of Hong Kong, China) MOCVD method has been used to grow functional optical thin films. Ta-doped SnO₂ is a transparent conductive oxide while Sc₂O₃ is a high index optical film. Both films are about 200 nm in thickness and show dense packing and superior properties. The influence of deposition temperature on the microstructure evolution and optical properties of Sc₂O₃ films was investigated by x-ray diffraction, scanning electron microscopy and spectrophotometry. Nanocrystalline films were obtained with low transmittance but high refractive index and hardness. Ta-doped SnO₂ films show sharp change of conductivity with Ta doping, which is attributed to the increase in carrier concentration. Improved crystallinity contributes to the improvement in the mobility among doped samples. Microstructural evaluation and property relationship will be discussed.