Nucleation kinetics versus nitrogen partial pressure during homoepitaxial growth of stoichiometric TiN(001): A scanning tunneling microscopy study

We grow homoepitaxial stoichiometric TiN(001) layers by ultra-high vacuum reactive magnetron sputtering in Ar/N-2 mixtures and use scanning tunneling microscopy to study nucleation as a function of the N-2 gas fraction f(N2) and growth temperature T, The characteristic island size R-c necessary to nucleate a new layer decreases continuously with f(N2) varying from 18.0 nm at T-s = 740 degrees C with f(N2) = 0.10 to 11.2 nm with f(N2) = 1.00. Over the temperature range 600 <= T-s <= 860 degrees C, nucleation is diffusion limited with an activation energy E-s of 1.1 +/- 0.1 eV for TiN(001) growth with f(N2) = 0.10 and 1.4 +/- 0.1 eV in pure N-2. We attribute the increase in E-s to a higher steady-state N coverage resulting in an increase in the average x-value of the primary surface-diffusing species, TiNx admolecules. (c) 2005 Elsevier B.V. All rights reserved.