Funnel Devices Based on Asymmetrically Strained Transition Metal Dichalcogenides.

The strain applied to transition metal dichalcogenides (TMDs) reduces their energy bandgap, and local strains results in a funnel-like band structure, in which funneled excitons move toward the most strained region. Herein, we report a funnel device based on asymmetrically strained WS 2 and MoS 2 . Asymmetric strains were induced by transferring the TMD flakes onto a fork-shaped SU-8 microstructure. Raman and photoluminescence spectra peaks were shifted according to the morphology of the SU-8 microstructure, indicating application of asymmetric strains to the TMDs. To investigate whether funneled excitons can be converted to electrical currents, various devices were constructed by depositing symmetric and asymmetric electrodes onto the strained TMDs. The scanning photocurrent mapping (SPCM) images followed a fork-shaped pattern, indicating probable conversion of the funneled excitons into electrical currents. In the case of the funnel devices with asymmetric Au and Al electrodes, short-circuit current (I SC ) of WS 2 was enhanced by the strains, whereas I SC of MoS 2 was suppressed because the Schottky barrier lowered with increasing strain for the MoS 2 , but not for the WS 2 . These results demonstrate that the funnel devices can be implemented using asymmetrically strained TMDs and the effect of strains on the Schottky barrier is dependent on the TMD used. This article is protected by copyright. All rights reserved.