Dresden 2014 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 34: Poster Session

MM 34.17: Poster

Dienstag, 1. April 2014, 18:00–20:00, P4

Band gap measurement of SiC nanowires by Valence EELS — •Anja Bonatto Minella^1,2, Darius Pohl¹, Christine Täschner¹, Rolf Erni³, Ludwig Schultz^1,2, and Bernd Rellinghaus¹ — ¹IFW Dresden, Dresden, Germany — ²TU Dresden, Dresden, Germany — ³Electron Microscopy Center, Empa, Dübendorf, Switzerland

Silicon carbide (SiC) nanowires (NW) of different polytypes have been prepared by Plasma-Enhanced Chemical Vapour Deposition. Their formation proceeds simultaneously with the growth of carbon nanofibres (CNF) leading to a heterostructure of SiC-filled CNF. In order to study the band gap of the SiC the graphitic layers of the CNF have to be removed by a heat treatment in oxygen atmosphere.

The (direct) band gap measurement is carried out using Valence Electron Energy Loss Spectroscopy (VEELS). SiC NW are found to exhibit a large direct band gap of 5.5 eV irrespectively of their polytype. Simulations using the optical properties of cubic SiC and DFT calculations show a similarly large value.

Another feature of the deconvoluted spectrum (after the removal of the zero loss peak) is the occurrance of energy losses that precede the onset of the band gap. This is probably caused by retardation losses or surface states. Possible ways of describing these residual features will be discussed, and the value of the band gap will be compared to reference data.