Browsing by Author "Wu, Chun-Chia"

Now showing 1 - 3 of 3

Enhanced wavelength-selective photoresponsivity with a MoS2 bilayer grown conformally on a patterned sapphire substrate
(2019-02-14)
Chen, Sung-Wen Huang
;
Wang, Sheng-Wen
;
Hong, Kuo-Bin
;
Medin, Henry
;
Chung, Chieh-Han
In the present study, novel MoS2 bilayers with 3D structures were considered for their application as wavelength-sensitive photodetectors. Using e-gun deposition and a CVD process, MoS2 bilayers can be grown conformally on a patterned (cones or pyramids) sapphire substrate without any wrinkles on the 2D film. After the sulfurization process, the MoS2 bilayer is subjected to a local strain in the patterns and its band gap gets enlarged due to the strain. This phenomenon is beneficial for photo-devices to enable the collection of the photocurrent. Measurements revealed a broadband enhancement of the MoS2-based photodetector with a patterned array in terms of both absorption and photocurrent. It is noteworthy that a cone-patterned sapphire substrate (CPSS) is able to generate more photocurrent when illuminated under blue light illumination, whereas the pyramid-patterned sapphire substrate (PPSS) performs best under green and red light illumination. Simulations of the electric field distributions for MoS2 coatings on different substrates, based on 3D models, revealed that the sensitivity of the MoS2-based photodetector can be greatly enhanced by the light-scattering effect.
Realizing thermal strain of patterned sapphire substrates dominate the bandgap-shifted of bilayer MoS2
(2017-01-01)
Wang, Sheng-Wen
;
Medina, Henry
;
Hong, Kuo-Bin
;
Wu, Chun-Chia
;
Arumugam, Manikandan
Using thermal strain concept, we can tune the bandgap of bilayer MoS2 through the two different thermal expansion coefficients of sapphire. Also, we propose a simple model to explain and precisely predict the bandgap-shifted behavior.
Thermally Strained Band Gap Engineering of Transition-Metal Dichalcogenide Bilayers with Enhanced Light Matter Interaction toward Excellent Photodetectors
(2017-09-01)
Wang, Sheng-Wen
;
Medina, Henry
;
Hong, Kuo-Bin
;
Wu, Chun-Chia
;
Qu, Yindong
Integration of strain engineering of two-dimensional (2D) materials in order to enhance device performance is still a challenge. Here, we successfully demonstrated the thermally strained band gap engineering of transition-metal dichalcogenide bilayers by different thermal expansion coefficients between 2D materials and patterned sapphire structures, where MoS2 bilayers were chosen as the demonstrated materials. In particular, a blue shift in the band gap of the MoS2 bilayers can be tunable, displaying an extraordinary capability to drive electrons toward the electrode under the smaller driven bias, and the results were confirmed by simulation. A model to explain the thermal strain in the MoS2 bilayers during the synthesis was proposed, which enables us to precisely predict the band gap-shifted behaviors on patterned sapphire structures with different angles. Furthermore, photodetectors with enhancement of 286% and 897% based on the strained MoS2 on cone and pyramid-patterned sapphire substrates were demonstrated, respectively.