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Standing and sitting adlayers in atomic layer deposition of ZnO

2015; American Institute of Physics; Volume: 34; Issue: 1 Linguagem: Inglês

10.1116/1.4938080

1520-8559

Zhengning Gao, Fei Wu, Yoon Myung, Ruixiang Fei, Ravindra K. Kanjolia, Li Yang, Parag Banerjee,

Electronic and Structural Properties of Oxides

The extent of reactivity of diethyl zinc (DEZ) with a hydroxylated surface during atomic layer deposition (ALD) of ZnO using DEZ and water is measured. Two adlayer configurations of DEZ are possible. The “standing” adlayer releases one ethyl group from DEZ. The “sitting” adlayer releases both ethyl groups, thus forming a Zn bridge between two O anions. Density functional theory calculations suggest the sitting configuration is more stable than the standing configuration by 790 meV. In situ quadrupole mass spectroscopy of by-product ethane generated in ALD half cycles indicate that ∼1.56 OH sites react with a DEZ molecule resulting in 71.6% of sitting sites. A simple simulation of a “ball-and-stick” DEZ molecule randomly collapsing on a neighboring site remarkably captures this adlayer behavior. It is concluded that DEZ fraction sitting is a competitive process of a standing DEZ molecule collapsing onto an available neighboring hydroxyl site, as sites vie for occupancy via adsorption and surface diffusion.