Strain-dependent interface barriers and photoresponse characteristics of MoSe2 monolayer flexible devices based on piezotronic and piezophototronic effects

Abstract

Investigating the interface barrier and photoresponse behavior by piezotronic and piezophototronic effects in semiconductor devices is essential for their application to flexible electronics and optoelectronics. Semiconductor-based monolayered two-dimensional transition-metal dichalcogenides exhibit superior mechanical, electrical, and optical characteristics than other materials. We used triangular MoSe₂ monolayers to fabricate two-terminal flexible devices and studied strain-dependent behaviors such as the interface barrier between the metal electrode and semiconductor by piezotronic phenomena. Our electrical and topography results showed that the interface barrier between a Pt electrode and MoSe₂ monolayer increases with increasing tensile strength and decreases with increasing compressive strain due to the strain-modulated increase and decrease of the energy barrier in the fabricated semiconductor. The flexible device was operated at a low voltage of 1 V as the ON condition in the tensile mode and OFF condition in the compressive mode. Furthermore, the strain-dependent interface barrier impacted the photoresponse characteristics in the MoSe₂ monolayer through energy bending bands, which influenced the electron–hole recombination by photogenerated carrier transport. These findings provide insights into the design of monolayered transition-metal dichalcogenides for applications in flexible electronics such as transducers, human–complementary metal–oxide–semiconductor interfaces, logical memory devices, and optoelectronics (e.g., flexible transparent devices).