Analysis of surface, subsurface, and bulk hydrogen in ZnO using nuclear reaction analysis

Abstract

Hydrogen concentrations in ZnO single crystals exposing different surfaces have been determined to be in the range of (0.02-0.04) at.% with an error of ±0.01 at.% using nuclear reaction analysis. In the subsurface region, the hydrogen concentration has been determined to be higher by up to a factor of 10. In contrast to the hydrogen in the bulk, part of the subsurface hydrogen is less strongly bound, can be removed by heating to 550 • C, and reaccommodated by loading with atomic hydrogen. By exposing the ZnO(1010) surface to water above room temperature and to atomic hydrogen, respectively, hydroxylation with the same coverage of hydrogen is observed.

Tuning the Work Function of Polar Zinc Oxide Surfaces using Modified Phosphonic Acid Self‐Assembled Monolayers

“…ZnO is known to adsorb residual contaminations such as H 2 , H 2 O, or CO 2 even under ultra‐high vacuum conditions, which alters the surface. Additionally, it has been shown that even brief exposure of high‐purity ZnO substrates to water already leads to H‐atom concentrations >0.1% in the bulk close to the surface . These H‐atoms lead to an effective n‐doping of this material, which will also affect the WF.…”

Optoelectronic properties and color chemistry of native point defects in Al:ZnO transparent conductive oxide

“…Experimental results 42,43 indicate that the hydrogen penetrates in ZnO in the dissociated (atomic) form and adsorbs to oxygen in an interstitial position, we therefore considered two possible hydrogen adsorption sites, one far and close Al, as for the Experimental results 42,43 indicate that the hydrogen penetrates in ZnO in the dissociated (atomic) form and adsorbs to oxygen in an interstitial position, we therefore considered two possible hydrogen adsorption sites, one far and close Al, as for the…”

Influence of polarity and hydroxyl termination on the band bending at ZnO surfaces

“…Traeger et al 52 quantified the hydrogen concentration profile in hydrothermal ZnO single crystals using 15 N nuclear reaction analysis and reported significantly higher hydrogen concentrations in the subsurface region compared to the bulk. In addition, part of this subsurface hydrogen was found to be less strongly bound and could be removed by heating to 550°C and then subsequently reloaded on exposure to atomic hydrogen.…”