Dresden 2009 – wissenschaftliches Programm

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DS: Fachverband Dünne Schichten

DS 28: Nanoengineered Thin Films I

DS 28.4: Vortrag

Donnerstag, 26. März 2009, 10:15–10:30, GER 37

Reactive Magnetron Sputtering of (GeO_x-SiO₂) Superlattices for Nanocrystal Synthesis — •Manuel Zschintzsch, Nicole M. Jeutter, Johannes von Borany, and Arndt Mücklich — Institute of Ion Beam Physics and Materials Research, Forschungszentrum Dresden Rossendorf, 01328 Dresden, Germany

The underlying motivation of this research is the tailored growth of Ge nanocrystals (NC) for photovoltaic applications [1,2]. Of special interest is the study of confinement effects to design bandgap engineered materials enabling light absorption within a wide range of the solar spectrum. In this contribution, we enlighten the deposition process of (GeO_x-SiO₂) superlattice structures (SL) via reactive DC magnetron sputtering and the self-ordered Ge-nanocrystal formation during subsequent annealing. SL structure delivers a reliable method to control the NC size after phase separation. Main attention is directed to define proper deposition conditions for tuning the GeO_x composition between elemental Ge (x=0) and GeO₂ (x=2) by the variation of the deposition temperature and the oxygen partial pressure. A process window has been found which allows GeO_x / SiO₂ deposition without changing the oxygen flow during the deposition. The phase separation and Ge NCs formation after subsequent anneling was investigated with in−situ X-ray diffraction, Raman spectroscopy and electron microscopy, confirming the existence of 2-5 nm Ge NCs. As the used technique allows to produce SL stacks with very smooth interfaces (roughness <1 nm), the Ge NC layers could be separated by very thin SiO₂ films (d >3 nm) which offers interesting possibilities for charge transport via tunneling.