Ab initiostudies of Al, O, andO2adsorption onα−Al2O3

Abstract

The interactions of Al, O, and O 2 with different ␣-Al 2 O 3 ͑0001͒ surfaces have been studied using ab initio density functional theory methods. All three surface terminations obtainable by cleaving the bulk structure ͓single Al-layer ͑AlO͒, double Al-layer ͑AlAl͒, and O terminations͔ have been considered, as well as a completely hydrogenated O-terminated surface. Adsorbed Al shows strong ioniclike interaction with the AlOand O-terminated surfaces, and several metastable adsorption sites are identified on the O-terminated surface. On the completely hydrogenated surface, however, Al adsorption in the bulk position is found to be unstable or very weak for the studied configurations of surface H atoms. Atomic O is found to interact strongly with the AlAl-terminated surface, where also O 2 dissociative adsorption without any appreciable barrier is observed. In contrast, O adsorption on the AlO-terminated surface is metastable relative to molecular O 2 . On the O-terminated surface, we find the creation of O surface vacancies to be plausible, especially upon exposure to atomic O at elevated temperatures. The results are mainly discussed in the context of alumina thin film growth and provide insight into phenomena related to, e.g., preferred adsorption sites and effects of hydrogen on the growth.

Synthesis of α-Al 2 O 3 thin films using reactive high-power impulse magnetron sputtering

“…For example, it has been shown that adsorbed H, which in the present case could originate from the residual gas in the deposition chamber, strongly inhibits continued α-Al 2 O 3 growth on (0001)-surfaces [23]. A similar plate-like microstructure of α-alumina was observed by Kohara et al [9] for sputter deposited films grown onto oxidized CrN layers (forming a Cr 2 O 3 nucleation layer) at a temperature of 750 °C.…”

First-principles investigations of the dielectric properties of polypropylene/metal-oxide interfaces

“…34 The relaxed surface structures in our calculations agree very well with other ab initio calculations. 35 For both kinds of slabs, our calculated 's ͓5.9 a.u. for ͑110͒ slabs and 8.9 a.u.…”

Influence of residual water on magnetron sputter deposited crystalline Al2O3 thin films

“…surfaces clearly showing that Al adsorption corresponding to the bulk crystal stacking sequence becomes unstable, or considerably weaker, on a completely hydrogenated surface [23]. Hence, this effect could give rise to renucleation, prohibit epitaxial effects between underlying and newly forming grains, and result in a consequent transition to γ-alumina growth and a small-grained microstructure.…”