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Prof. Sebastian Fiechter Seminar @ 10 AM, 109 Jorgensen, Caltech

Prof. Sebastian Fiechter
Deputy Director of the Institute for Solar Fuels at Helmholtz-Zentrum

"Thermodynamics and Kinetics of Semiconductor Preparation" (Part I)
The lecture will address growth of bulk material and thin films of compound semiconductors which are of interest as absorbers for water splitting electrodes. The focus of the presentation is transition metal chalcogenides of different structure types and different thermal behavior and its implications for the growth of highly textured films. In the examples discussed metal induced crystallization as known from WS2 and MoS2 plays an important role. In a second example it will be shown that composition gradients can be obtained by sulfurization of metal films deposited by thermal evaporation.

"Case study: Thermal behaviour and homogeneity ranges of CuInS2 (roquésite) and BiVO4 (clinobisvanite)" (PartII)
In the second part of the presentation phase relations and physical properties of ternary chalco-genides will be discussed. Using thermogravimetric (TG) and differential thermal analysis (DTA) coupled with mass spectrometry (MS) the thermal stability and the defect chemistry in compound semiconductors such as roquésite and clinobisvanite can be determined. For example, deviations from stoichiometry become visible in the melting behaviour of these compound semiconductors. In the case of clinobisvanite the orientation of crystal grains in photoelectrodes presumably play an important role owing to the ferroelectric properties of the oxide.