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  • Interdiffusion at ▫$TiO_2$▫/Ti, ▫$TiO_2$▫/▫$Ti_3$▫Al and ▫$TiO_2$▫/TiAl interfaces studied in bilayer structures
    Zalar, Anton ...
    Understanding of oxide/metal structure is of increasing importance for different areas of material science, e.g. for the adhesion of oxide scales on metal substrates, for metallic interconnects in ... semi conductors and for the joining and coating technology. During oxidation of Ti-Al alloys a mixture of Al[sub]2O[sub]3 and TiO[sub]2 forms the surface. Recently it was observed that prolonged oxidation led to decomposition of initially formed TiO[sub]2. To obtain knowledge of the occuring interdiffusion processes, the early interfacial reaction stages were studied in three different types of oxide/metal bilayers composed of oxide=amorphous a-TiO[sub]2 and metal=crystalline c-Ti, c-Ti[sub]3Al or amorphous a-TiAl. The oxide/metal bilayers were sputter deposited on smooth silicon substrates, covered with a TiN thin-film diffusion barrier. The reactions at the oxide/metal interfaces were induced by heating the samples in an argon atmosphere at a linear heating rate of 40°C min[sup]-1, between room temperature and different final temperatures (350°C to 700°C). The elemental composition profiles were determined by means of Auger electron spectroscopy (AES) depth profiling. The microstructures of the selected samples before and after heat treatment were investigated by means of cross-sectional transmission electron microscopy (TEM) and X-ray diffraction (XRD). The heating of the a-TiO[sub]2/c-Ti, a-TiO[sub]2/Ti[sub]3Al and a-TiO[sub]2/a-TiAl bilayers induced decomposition of TiO[sub]2 layers, in association with oxygen diffusion into the metal layers. This decomposition of TiO[sub]2 is much more pronounced than for Al[sub]2O[sub]3 in analogues bilayers. The beginning of the interdiffusion in a-TiO[sub]2/c-Ti bilayer was observed at about 400°C and in the other two bilayers at a little higher temperature. In the heat treated bilayers a solid solution of oxygen in the corresponding metallic layers was fomed. The presence of Al in a metallic layers results in a lower solubility for oxygen as compared to a pure Ti layer. By applying target-factor analysis it was possible to distinguish between different states of chemical bonding of the elements analysed in the heated a-TiO[sub]2/c-Ti[sub]3Al and a-TiO[sub]2/a-TiAl bilayers. The temeprature-dependet effective diffusion coefficient were determined from the rate of increase of the interface width, as determined in the oxygen-depth profiles. The activation energies for the oxygen diffusion from the amorphous TiO[sub]2 into the c-Ti, c-Ti[sub]3Al and a-TiAl thin films were obtained from Arrhenius plots and were found to be between 1,5 eV and 1,8 eV.
    Vir: Book of abstracts (Str. 124)
    Vrsta gradiva - prispevek na konferenci ; neleposlovje za odrasle
    Leto - 2001
    Jezik - angleški
    COBISS.SI-ID - 59874

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