AVS 47th International Symposium
    Thin Films Tuesday Sessions
       Session TF-TuA

Paper TF-TuA5
Structural and Mechanical Properties of TiC/Ti and TiC/B@sub 4@C Multilayers Deposited by Pulsed Laser Deposition

Tuesday, October 3, 2000, 3:20 pm, Room 203

Session: Mechanical Properties of Thin Films
Presenter: A.R. Phani, University of New Hampshire
Authors: A.R. Phani, University of New Hampshire
J.E. Krzanowski, University of New Hampshire
J.J. Nainaparampil, Systran, Inc.
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Multilayer thin films have been shown to enhance the hardness as well as toughness of hard ceramic coatings, and the results often depend on the type of interlayer used. In the present study, we have investigated multilayers of TiC/Ti (for toughness enhancement) and TiC/B@sub 4@C (for hardness enhancement). Films were deposited on 440C steel and silicon substrates by pulsed laser deposition (PLD). Ti, B@sub 4@C and TiC targets were ablated in a background gas of 1mTorr Ar at substrate temperatures of 200, 400 and 600C. Samples were deposited having modulation periods ranging from 2.5 to 50 nm. Films were analyzed using nano-indentation hardness, x-ray diffraction, XPS and electron microscopy. Surface morphology and roughness of the samples were measured by scanning electron microscopy and atomic force microscopy, respectively. Tribological studies have also been conducted to evaluate the friction and wear properties of these films. Films with low modulation periods showed lower residual stresses as measured by x-ray diffraction methods. The nano-indentation hardness of compositionally modulated Ti/TiC and TiC/B@sub 4@C multilayer films were found to be dependent on composition modulation frequency. TiC/Ti films showed reasonably high hardness values (37GPa) for the lower period samples despite the incorporation of the metal layer, and TiC/B@sub 4@C films showed hardness levels up to 42GPa. Film composition depth profiles performed by using XPS showed 1-2 at % oxygen in the deposited films, as well confirming the presence of composition modulations. The mechanisms of hardness enhancement and its relation to tribological properties will also be discussed.