Berlin 2012 – scientific programme
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MM: Fachverband Metall- und Materialphysik
MM 46: Nanomaterials I
MM 46.4: Talk
Thursday, March 29, 2012, 11:00–11:15, H 1029
Si/SiO2 nanostructures grown by dewetting of ultrathin amorphous Si-layers for photovoltaic applications — •Jan Amaru Töfflinger1, Maurizio Roczen1, Martin Schade2, Orman Gref1, Andreas Schöpke1, Enno Malguth1, Lars Korte1, Hartmut Leipner2, and Bernd Rech1 — 1HZB, Inst. Si-Photovoltaik, Berlin, Deutschland — 2MLU, IZM, Halle, Deutschland
Si nanodots embedded in a SiO2 matrix hold the potential for an enhancement of the efficiency of silicon based solar cells. The application of such Si/SiO2 nanostructures as hetero-emitter on top of an oxidized wafer is investigated. For Si-wafer passivation tunneling oxides with thicknesses down to 1 nm are developed by means of UHV-oxidation using neutral, thermalized oxygen atoms. The density of states at the Si/SiO2 interface as well as its chemical composition is examined via in-situ photoelectron spectroscopy. The UHV-synthesis of Si nanodots is performed by deposition of a thin (1-10 nm) undoped amorphous Si film on top of the oxidized wafer and a subsequent 600°C annealing step. This leads to the self-organized formation of highly crystalline Si nanodots. Nanodot diameters <10 nm are achieved which in principle allows to exploit quantum size effects. The influence of Sb-doping of the initial a-Si film on nanodot formation is investigated. Stacked Si/SiO2 nanodot systems via layer by layer repetition of oxidation and nanodot formation are manufactured and investigated via HRTEM and electrical measurements. Cross sectional images indicate high density of nanodots separated by tunneling oxides allowing an electrical current through the nanodot system by tunneling processes.