Browsing by Author "Tsai, Meng-Lin"

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A Nanostructuring Method to Decouple Electrical and Thermal Transport through the Formation of Electrically Triggered Conductive Nanofilaments
(2018-07-12)
Retamal, Jose Ramon Duran
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Kang, Chen-Fang
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Lien, Der-Hsien
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Kuo, Wei-Cheng
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Juang, Zhen-Yu
Transforming thermal energy into electric energy and vice versa needs the decoupling of electrical transport from thermal transport. An innovative strategy is proposed by forming/disrupting electrically triggered conductive nanofilaments within semiconducting thin films to switch thermoelectric properties between two states without further material modification and manufacturing processes. It can also controllably adjust the degree of decoupling, providing a potential resolution and performance adjustability for heat/coldness control or power consumption reduction on demand.
Epitaxial growth of a monolayer WSe2-MoS2 lateral p-n junction with an atomically sharp interface
(2015-07-31)
Li, Ming-Yang
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Shi, Yumeng
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Cheng, Chia-Chin
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Lu, Li-Syuan
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Lin, Yung-Chang
Two-dimensional transition metal dichalcogenides (TMDCs) such as molybdenum sulfide MoS2 and tungsten sulfide WSe2 have potential applications in electronics because they exhibit high on-off current ratios and distinctive electro-optical properties. Spatially connected TMDC lateral heterojunctions are key components for constructing monolayer p-n rectifying diodes, light-emitting diodes, photovoltaic devices, and bipolar junction transistors. However, such structures are not readily prepared via the layer-stacking techniques, and direct growth favors the thermodynamically preferred TMDC alloys. We report the two-step epitaxial growth of lateral WSe2-MoS2 heterojunction, where the edge of WSe2 induces the epitaxial MoS2 growth despite a large lattice mismatch. The epitaxial growth process offers a controllable method to obtain lateral heterojunction with an atomically sharp interface.
Few-Layer MoS2 with High Broadband Photogain and Fast Optical Switching for Use in Harsh Environments
(2013-05-01)
Tsai, Dung-Sheng
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Liu, Keng-Ku
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Lien, Der-Hsien
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Tsai, Meng-Lin
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Kang, Chen-Fang
Few-layered MoS2 as Schottky metal-semiconductor-metal photodetectors (MSM PDs) for use In harsh environments makes its debut as two-dimensional (2D) optoelectronics with high broadband gain (up to 13.3), high detectivity (up to similar to 10(10) cm Hz(1/2)/W), fast photoresponse (rise time of similar to 70 mu s and fall time of similar to 110 mu s), and high thermal stability (at a working temperature of up to 200 degrees C). Ultrahigh responsivity (0.57 A/W) of few-layer MoS2 at 532 nm is due to the high optical absorption (similar to 10% despite being less than 2 nm in thickness) and a high photogain, which sets up a new record that was not achievable in 2D nanomaterials previously. This study opens avenues to develop 2D nanomaterial-based optoelectronics for harsh environments in imaging techniques and light-wave communications as well as in future memory storage and optoelectronic circuits.
Ultrahigh-Gain Photodetectors Based on Atomically Thin Graphene-MoS2 Heterostructures
(2014-01-23)
Zhang, Wenjing
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Chuu, Chih-Piao
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Huang, Jing-Kai
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Chen, Chang-Hsiao
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Tsai, Meng-Lin
Due to its high carrier mobility, broadband absorption, and fast response time, the semi-metallic graphene is attractive for optoelectronics. Another two-dimensional semiconducting material molybdenum disulfide (MoS2) is also known as light-sensitive. Here we show that a large-area and continuous MoS2 monolayer is achievable using a CVD method and graphene is transferable onto MoS2. We demonstrate that a photodetector based on the graphene/MoS2 heterostructure is able to provide a high photogain greater than 108. Our experiments show that the electron-hole pairs are produced in the MoS2 layer after light absorption and subsequently separated across the layers. Contradictory to the expectation based on the conventional built-in electric field model for metal-semiconductor contacts, photoelectrons are injected into the graphene layer rather than trapped in MoS2 due to the presence of a perpendicular effective electric field caused by the combination of the built-in electric field, the applied electrostatic field, and charged impurities or adsorbates, resulting in a tuneable photoresponsivity.