AVS 51st International Symposium
    Thin Films Monday Sessions
       Session TF-MoA

Paper TF-MoA7
Development of Zrb@sub 2@ and Hfb@sub 2@ Hard Coatings by CVD from Single Source Precursors

Monday, November 15, 2004, 4:00 pm, Room 303C

Session: Mechanical Properties of Thin Films
Presenter: S. Jayaraman, University of Illinois at Urbana-Champaign
Authors: S. Jayaraman, University of Illinois at Urbana-Champaign
E.J. Klein, University of Illinois at Urbana-Champaign
Y. Yang, University of Illinois at Urbana-Champaign
L. Nittala, University of Illinois at Urbana-Champaign
J.R. Abelson, University of Illinois at Urbana-Champaign
D.Y. Kim, University of Illinois at Urbana-Champaign
G.S. Girolami, University of Illinois at Urbana-Champaign
Correspondent: Click to Email
The transition metal diborides ZrB@sub 2@ and HfB@sub 2@ are "metallic ceramic" materials with excellent properties, including high melting temperature (> 3000 °C), low electrical resistivity (9 µm@ohm@cm for ZrB@sub 2@), high thermal conductivity (23 Wm@super -1@K@super -1@ for ZrB@sub 2@), high hardness (20 and 29 GPa for ZrB@sub 2@ and HfB@sub 2@, respectively), and great corrosion resistance. This makes them attractive candidates for monolithic or nanocomposite based hard coatings. However, there have been relatively few attempts to deposit transition metal diboride coatings by chemical vapor deposition (CVD). Here, we investigate ZrB@sub 2@ and HfB@sub 2@ growth by CVD using the single-source precursors Zr[BH@sub 4@]@sub 4@ and Hf[BH@sub 4@]@sub 4@ over the substrate temperature range 200-1000 °C. At temperatures < 500 °C, we direct a flux of atomic hydrogen, generated by a remote plasma source, onto the growth surface in order to promote the removal of excess boron and improve stoichiometry. For deposition temperatures < 500 °C the films appear to be amorphous in X-ray diffraction; for higher temperatures crystalline peaks are detected. The crystalline films are strongly textured with either (0001) or (10@super-@10) planes normal to the growth direction and display characteristic microstructures. Initial experiments on trench coverage at low temperatures show that film growth is conformal. We will report the hardness of ZrB@sub 2@ and HfB@sub 2@ films determined by nanoindentation and the relationship between the hardness, crystallinity, and microstructure. We will also outline the prospects for the growth of nanocomposite hard coatings in this materials system.