Berlin 2008 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 54: Si/Ge
HL 54.14: Vortrag
Freitag, 29. Februar 2008, 14:00–14:15, EW 202
Phosphorus doping of Si nanocrystals — •Andre R. Stegner1, Rui N. Pereira1, E. Ulrich Stützel1, Hartmut Wiggers2, Martin S. Brandt1, and Martin Stutzmann1 — 1Walter Schottky Inst., Technische Universität München, Garching — 2Universität Duisburg-Essen, Inst. for Combustion and Gas Dynamics, Duisburg
Si nanocrystals (Si-ncs), in particular in the form of deposited or self-organized thin films are an interesting option for printed electronics and solar cells. However, the doping of individual Si-ncs, as well as its influence on the electronic properties of Si-ncs films is essentially unexplored. Here, we have used electron paramagnetic resonance (EPR) to study the P doping of Si-ncs grown by microwave-induced decomposition of silane and phosphine. EPR spectra of the as-grown Si-ncs show characteristic resonances from isolated as well as exchange-coupled P donors and an intense line originating from Si dangling bonds (Si-dbs) at the Si/SiO2 interface. While the P concentration determined with secondary ion mass spectroscopy is in good agreement with the doping level calculated from the phosphine concentration during synthesis, a quantitative analysis of the EPR data reveals that only a small fraction of the donors contributes to the characteristic EPR signal. This discrepancy increases strongly for Si-ncs smaller than 15 nm and is discussed taking into account effects like self purification and charge compensation by Si-dbs. Using electrically detected magnetic resonance to study the spin-dependent transport in thin films of Si-ncs, we show that P donor states in the core of the Si-ncs and Si-dbs at the nanocrystal surface are actively involved in the current transport.