Bandgap Engineering of Amorphous Hydrogenated Silicon Carbide

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Abanto E.
Bejar V.
García R.
Gonzales S.
Guevara J.M.
Gutierrez E.L.
Hagen F.
Ortega-Loayza A.G.
Tello M.
Valencia E.
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Materials Research Society
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A simple model to describe the fundamental absorption of amorphous hydrogenated silicon carbide thin films based on band fluctuations is presented. It provides a general equation describing both the Urbach and Tauc regions in the absorption spectrum. In principle, our model is applicable to any amorphous material and it allows the determination of the bandgap. Here we focus on the bandgap engineering of amorphous hydrogenated silicon carbide layers. Emphasis is given on the role of hydrogen dilution during the deposition process and post deposition annealing treatments. Using the conventional Urbach and Tauc equations, it was found that an increase/decrease of the Urbach energy produces a shrink/enhancement of the Tauc-gap. On the contrary, the here proposed model provides a bandgap energy which behaves independently of the Urbach energy.
This research was funded by the Research Management Office (DGI) of the Pontificia Universidad Católica del Perú (PUCP). The authors have been supported by the PUCP under the PhD scholarship program Huiracocha (J A Guerra) and by the National Council of Science and Technology (CONCYTEC) under the scholarships granted to the PUCP (J R Angulo and J Llamoza). The author would like to thank Prof Dr H P Strunk, F Benz and Dr Y Weng of the University of Stuttgart for the TEM measurements.
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Thin films