| Summary: | 碩士 === 國立交通大學 === 光電工程研究所 === 105 === Two-dimensional (2D) materials have attracted a great attention due to their high performance for several applications. Molybdenum disulfide (MoS2), as a transition metal dichalcogenides (TMDCs) material, has shown extraordinary properties in photoelectric and photovoltaic devices in recent years due to the direct band gap of monolayer and strong light-matter interaction with light. However, owing to the innate thinness of monolayer MoS2, such a strong interaction must be further enhanced before it can be used in practical devices. Therefore, we develop a new approach to enhance the absorption by directly grow MoS2 on patterned sapphire substrate (PSS). The integration of PSS and MoS2 can enhance the light-matter interaction by the scattering of incident light.
In this thesis, we directly synthesize the bilayer MoS2 on photonic crystal structures by using chemical vapor deposition (CVD)-growth method, and we have an amazing discovery after sulfurization process. Through thermal stress concept, we utilize the natural properties of sapphire (it has two different thermal expansion coefficients) and successfully tuned the band gap of bilayer MoS2. Our approach has an extraordinary capability to drive electrons toward flat region of the substrate by the shift of the band gap, allowing the electrode collects electrons more easily. Eventually, the bilayer MoS2 photodetectors with patterned and flat sapphire substrate are produced and demonstrated the performance of each sample. Those photodetectors with patterned substrates have outstanding broadband enhancement of photocurrent since the enhancement of light-matter interaction by the integration of patterned substrates and MoS2. Interestingly, different shape of patterned substrates will have the best enhancement of photocurrent at different region of incident light. It is believed that in the future, we can design or choose different patterned substrate to strongly enhance the absorption at specific region of incident light for different applications.
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