Physico-chemical nanomaterials science
Effect of the adsorption of 3d transition metals on the oxidation of the Si (001) surface
T.V. Afanasieva
Physical Electronics Department, Institute of Physics of the NAS of Ukraine. Prospect Nauki, 46, Kyiv-03039, Ukraine. 
E-mail: tetiana.v.afanasieva@gmail.com

We report the results of a comparative theoretical study of the interaction of molecular oxygen with the silicon surface coated by submonolayer 3d transition metal (TM - Ti, Cr, Mn) films. Investigating the effect of transition metal adsorption on surface oxidation is important for technological applications because such systems can be used in conventional silicon technologies. Recently, the promoting effect of adsorbed metals on the silicon surface oxidation was found [1].
The simulations were carried out using a hybrid quantum mechanical-molecular mechanical (QM/MM) method and embedded clusters - SIMOMM (Surface Integrated Molecular Orbital Molecular Mechanics) with GAMESS/TINKER software. 
Oxygen atoms tend to bind with 3d transition metal atoms (Ti, Cr, Mn) adsorbed on the Si(001) surface. Therefore, the transition metal atoms are active centres for the TM/Si(001) surface oxidation. The formation of the metal-O-Si bridge structures is more energetically favourable for Cr/Si(001) and Mn/Si(001) systems. The adsorption of neighbouring O atoms is energetically preferable to non-interacting inserts of single O atoms. Consequently, at the initial stage of oxidation of the TM/Si(001) surfaces, island growth of oxides is energetically preferable to uniform growth. 
Dissociation of O2 molecule on the TM/Si(001) surface involves the transition between different spin states. The stationary states in the Ti/Si(001)+O system are singlet in contrast to the stationary states in the Cr/Si(001)+O and Mn/Si(001)+O systems. Both atomic and molecular oxygen bind more tightly with Ti atoms adsorbed on the Si(001) surface than with Cr or Mn atoms. The dissociation of molecular oxygen on the metal active centres on the TM/Si(001) surface is exothermic. 

1.	Koval’ I. P., Len’ Yu. A., Nakhodkin M. G., Svishevs’kyi M. O., Yakovenko M. Yu. Interaction of Molecular Oxygen with Si(001) Surface Covered with a Chromium or Titanium Monolayer // Ukr. J. Phys.-2015.-60, N 1.-P. 46-51.