Pathways of atomistic processes on TiN(001) and (111) surfaces during film growth: an ab initio study

Abstract

Density functional methods were used to calculate binding and diffusion energies of adatoms, molecules, and small clusters on TiN͑001͒ and TiN͑111͒ surfaces in order to isolate the key atomistic processes which determine texture evolution during growth of polycrystalline TiN layers. The surface energy for nonpolar TiN͑001͒, 81 meV/Å 2 , was found to be lower than that of both Nand Ti-terminated TiN͑111͒ polar surfaces, 85 and 346 meV/Å 2. While N 2 molecules are only weakly physisorbed, Ti adatoms form strong bonds with both TiN͑001͒, 3.30 eV, and TiN͑111͒, 10.09 eV. Ti adatom diffusion is fast on ͑001͒, but slow on ͑111͒ surfaces, with calculated energy barriers of 0.35 and 1.74 eV, respectively. The overall results show that growth of 111-oriented grains is favored under conditions typical for reactive sputter deposition. However, the presence of excess atomic N ͑due, for example, to collisionally induced dissociation of energetic N 2 ϩ ions͒ leads to a reduced Ti diffusion length, an enhanced surface island nucleation rate, and a lower chemical potential on the ͑001͒ surface. The combination of these effects results in preferential growth of 001 grains. Thus our results provide an atomistic explanation for the previously reported transition from 111 to 001 texture observed for sputter deposition of TiN in Ar/N 2 mixtures with increasing N 2 partial pressure P N 2 and at constant P N 2 with increasing N 2 ϩ /Ti flux ratios incident at the growing film.

Formation and morphological evolution of self-similar 3D nanostructures on weakly interacting substrates

“…However, vapor condensation and film growth proceed far from thermodynamic equilibrium and thus morphological evolution is primarily determined by the relative rates of competing atomistic structure-forming processes (i.e., by kinetics) [1][2][3]. Currently, the most detailed atomistic * kostas.sarakinos@liu.se description of far-from-equilibrium 3D island formation is based on homoepitaxial systems in which 3D islands (mounds) form by deposition onto existing small islands, followed by atomic-step descent limited by the Ehlrich-Schwöbel barrier [15][16][17][18][19]. However, for weakly interacting film/substrate systems-including Ag/SiO 2 [20][21][22][23][24], Pd/TiO 2 [25], Cu/ZnO [26,27], and Dy/graphene [4,28]-3D islands develop before the initially formed one-atom-high islands are large enough to efficiently capture vapor-phase deposition flux.…”

Effect of Al substitution on Ti, Al, and N adatom dynamics on TiN(001), (011), and (111) surfaces

“…Knowledge of adatom dynamics is difficult to obtain experimentally due to the short time scales involved. Instead, first-principles calculations, often within transition state theory (TST), [20,21] have been extensively used to provide valuable insight into the surface kinetics of elemental metals, [22][23][24] binary compounds such as TiC, [25,26] and the parent compounds of Ti 1−x Al x N, TiN [26][27][28][29][30] and AlN. [31] Going beyond static approximations, ab initio and classical molecular dynamics have proven valuable to elucidate mechanisms of adspecies migration [32,33] and to model thin-film growth.…”

Ab initio molecular dynamics of Al irradiation-induced processes during Al2O3 growth

“…For instance, 20 eV N 2 + ions have been argued to alter the preferred orientation of TiN from ͑111͒ to ͑001͒. 25 Furthermore, in diamondlike carbon subplantation has been shown to promote sp 3 bonding. 19 In this work, ␣-Al 2 O 3 ͑0001͒ and ␥-Al 2 O 3 ͑001͒ are bombarded with Al at 330 K using ab initio MD simulations and structural changes are observed.…”