Berlin 2018 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 56: New materials and concepts
HL 56.1: Talk
Friday, March 16, 2018, 11:15–11:30, EW 202
Characterization of dip coated tungsten sulfide flakes — •Talha Nisar, Torsten Balster, and Veit Wagner — Jacobs University Bremen gGmbH, Campus Ring 1, 28759 Bremen, Germany
WS2 is a promising material for future electronics due to its 2 dimensional nature. In our approach we use growth on liquid surface as an alternative deposition method to atomic layer deposition and chemical vapor deposition to grow tungsten sulfide flakes. For this purpose, ammonium tetrathiotungstate (ATTW) is used as precursor material in a 5 mM aqueous solution. No flakes are formed while at room temperature, formation of flakes at the liquid-air interface is observed after heating the solution at 80∘C for an hour. Flakes with sizes up to 50 µm are transferred onto a silicon substrate by dip-coating. A post annealing step is done at 800∘C in a quartz tube applying a constant flow of forming gas (95% Ar/5% H2) with additional sulfur source. Chemical characterization of the flakes by mean of x-ray photoelectron spectroscopy (XPS) reveal that the flakes initially consist out of WO2 and ATTW. Post growth annealing converted this layer to WS2. High crystallinity of the flakes is proved by Raman measurements.