IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Thin Films Wednesday Sessions
       Session TF-WeM

Paper TF-WeM5
Atomic-Scale Processes in the Growth of Transition-Metal Nitrides

Wednesday, October 31, 2001, 9:40 am, Room 123

Session: Fundamentals of Deposition
Presenter: D. Gall, University of Illinois, Urbana
Authors: D. Gall, University of Illinois, Urbana
C.-S. Shin, University of Illinois, Urbana
M.A. Wall, University of Illinois, Urbana
I. Petrov, University of Illinois, Urbana
J.E. Greene, University of Illinois, Urbana
Correspondent: Click to Email
Polycrystalline and epitaxial layers of NaCl-structure transition-metal (TM) nitrides -- TiN, ScN, CrN, and TaN -- were grown on oxidized Si and MgO(001) at 450-1000 °C by ultra-high-vacuum magnetically-unbalanced magnetron sputter deposition in pure N@sub 2@ and N@sub 2@+Ar discharges at 3-20 mTorr. Polycrystalline layers grown under low ion-irradiation conditions exhibit a columnar microstructure with strong 111 preferred orientation which evolves in a kinetically-limited competitive growth mode due to a large anisotropy in adatom mobilities and binding energies. Surface diffusion energies E@sub s@ were obtained from T-dependent nucleation length measurements using STM and by ab-inito density functional calculations. E@sub s@ for (001) and (111) TiN surfaces are 0.8 and 1.7 eV. The much smaller 111 adatom mobility results in preferential 3D growth and, ultimately, in the observed 111-preferred orientation. However, increasing the energy of incident N@sub 2@@super +@ ions during deposition to 20 eV results in layers with purely 001-texture. The high anisotropy in adatom mobilities gives rise to another unique microstructural feature: epitaxial 001-oriented layers exhibit self-organized arrays of 1-nm-wide nanopipes which are formed as a result of periodic kinetic surface roughening and subsequent atomic self-shadowing. While the microstructures of different NaCl-structure TM-nitrides are similar, their electronic and optical properties vary widely. TiN has metallic conductivity, ScN is semiconducting, and CrN is an antiferromagnetic insulator. The color of Ti@sub 1-x@Sc@sub x@N varies continuously with x from golden yellow to orange to burgundy to blue-green to transparent. Measured hardness of single crystal 001-oriented layers are 20, 21, 28, and 31 GPa for TiN, ScN, CrN, and TaN, respectively.