Initial reaction mechanism of nitrogen-doped zinc oxide with atomic layer deposition

Atomistic mechanism for the nitrogen-doped ZnO Atomic Layer Deposition (ALD) on Si(100)-2 x 1 surface is investigated within the framework of density functional theory. We have examined three possible reaction pathways involving the metal precursors diethyl Zinc and ammonia hydride (NH4OH), which serves as oxidizer and nitrogen doping source. The dissociation of NH4OH leads to NH3 and H2O for latter parallel half reactions occurring simultaneously following the diethyl Zinc half reaction. Our results show overall three reactions are exothermic and energetically favorable, however, the adsorption energy in diethyl Zinc half reaction is only -6.53 kJ/mol, which is much lower compared to NH3 and H2O half reactions, indicating longer zinc precursor pulsing time is indeed needed in order to attain better -ZnCH2CH3* group coverage. The energy barrier in NH3 and H2O half reactions are 142.00 and 94.16 kJ/mol respectively, combining with the calculation results that the exothermic energy of the H2O half reaction is 39.04 kJ/mol higher than the NH3 half reaction, we concluded that in the initial ALD zinc oxide procedure the ZnO deposition rate is much faster than the incorporation of nitrogen, which is in accordance with the function of nitrogen as p-type impurities in ZnO semiconductor. (C) 2009 Elsevier B.V. All rights reserved.