Ge-Si-O phase separation and Ge nanocrystals growth in Ge:SiO2/SiO2 multilayers – A new dc magnetron approach


Ge-Si-O phase separation and Ge nanocrystals growth in Ge:SiO2/SiO2 multilayers – A new dc magnetron approach

Zschintzsch, M.; Sahle, C. J.; von Borany, J.; Sternemann, C.; Mücklich, A.; Nyrow, A.; Schwamberger, A.; Tolan, M.

Ge:SiOx /SiO2 multilayers are fabricated using a new reactive dc magnetron sputtering approach. The influence of the multilayer stoichiometry on the ternary Ge–Si–O phase separation and the subsequent size-controlled Ge nanocrystal formation is explored by means of x-ray absorption spectroscopy, x-ray diffraction, electron microscopy and Raman spectroscopy. The ternary system Ge–Si–O reveals complete Ge–O phase separation at 400°C which does not differ significantly to the binary Ge–O system. Ge nanocrystals of < 5 nm size are generated after subsequent annealing below 700°C. It is shown that Ge oxides contained in the as-deposited multilayers are reduced by a surrounding unsaturated silica matrix. A stoichiometric regime was found where almost no GeO2 is present after annealing. Thus, the Ge nanocrystals become completely embedded in a stoichiometric silica matrix favouring the use for photovoltaic applications.

Keywords: annealing; elemental semiconductors; germanium; germanium nanocrystals; nanofabrication; nanoparticles; growth; quantum confinement; quantum dots; multilayer; phase separation; sub-oxides; Raman; phonon confinement, semiconductor growth; semiconductor thin films; silicon nanocrystals; sputter deposition; superlattices; transmission electron microscopy; tunnelling; X-ray scattering

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Publ.-Id: 15708