Regensburg 2010 – scientific programme
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MM: Fachverband Metall- und Materialphysik
MM 26: Poster Session
MM 26.66: Poster
Tuesday, March 23, 2010, 14:45–16:30, Poster C
The Influence of wet-chemical smoothing on electronic properties of Si/SiO2 interfaces prepared by UHV plasma oxidation — •Orman Gref, Bert Stegemann, Enno Malguth, Maurizio Roczen, Heike Angermann, and Manfred Schmidt — Silicon Photovoltaics, Helmholtz-Zentrum Berlin für Materialien und Energie, Berlin, Germany
The successful application Si/SiO2 interfaces for ultrathin oxides or nanostructures in third generation photovoltaics requires a minimum density of Si gap states. In order to achieve this goal, the influence of various wet-chemical pre-treatment procedures on the electronic properties of Si/SiO2 interface was investigated. Structurally abrupt Si/SiO2 interfaces were prepared under ultrahigh vacuum conditions by RF plasma oxidation of n-type Si(111) substrates with thermalized neutral oxygen atoms. A decrease the interface states was achieved by saturating dangling bonds through in situ RF hydrogen plasma passivation . The density of gap states at the Si surface and Si/SiO2 interface was investigated by non-destructive and surface-sensitive surface photovoltage (SPV) experiments. Various sequences of wet-chemical oxidation and oxide removal steps in HF- or NH4F solutions were successfully applied to reduce the substrate surface micro-roughness and surface state density. These optimised wet-chemical smoothing procedures yield a significant decrease in interface state densities of the subsequently prepared Si/SiO2 interfaces Dit=1*1012cm−2eV−1, compared to Dit=3.5*1012cm−2eV−1, obtained after applying solely the standard RCA cleaning process and HF solution.