MICROSTRUCTURAL AND SURFACE MORPHOLOGICAL EVOLUTION AT THE ATOMIC SCALE DURING THE GROWTH OF POLYCRYSTALLINE TiN: A HR-TEM, XRD, STM, AND MODELING STUDY

Joe Greene, S. Kodambaka, P. Desjardins, A. Vailionis, V. Petrova, I. Petrov,and D. Cahill

Dept. Materials Science, Univ. Illinois, Urbana, IL 61801, USA

XRD, TEM, and HR-XTEM analyses show that TiN grown by reactive evaporation or sputter deposition at low temperatures (Ts < 450 C) exhibits competitive texture evolution with a columnar 111 "kinetically-limited" texture eventually becoming dominant. The columns are narrow and facetted with inter-and intracolumn porosity. Higher Ts or the use of high incident N2+/Ti flux ratios (> 5) with low N2+ energies (20 eV) result in non-competitive growth with a fully dense complete 002 orientation from the initial monolayer. The columns are broad-based with flat surfaces. Kinetic Monte Carlo modeling, assuming that the activation energy Es for surface diffusion and the Ehrlich barrier Eb at descending step edges are larger on 111 than on 002, provide a qualitative understanding. Quantitative modeling requires transport activation energies (Es, Eedge, and Eb) and island line tensions vs orientation. Partial TiN monolayers (0.1-0.4 ML) were deposited on epitaxial TiN(001) with large (> 1500 A) atomically-flat terraces and in-situ high-TSTM used to follow coarsening and decay kinetics of single and multiple islands (Ostwald ripening). From the results, combined with solutions of the Gibbs-Thompson and diffusion equations, we obtain the parameters listed above. The STM observations provide important atomic-scale insights into the growth of TiN and related transition-metal nitrides.