Browsing by Author "Su, Chen-Fung"

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Fermi-level shifts in graphene transistors with dual-cut channels scraped by atomic force microscope tips
(2014-01-13)
Lin, Meng-Yu
;
Chen, Yen-Hao
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Su, Chen-Fung
;
Chang, Shu-Wei
;
Lee, Si-Chen
We investigate the electronic properties of p-type graphene transistors on silicon dioxide with dual-cut channels that were scraped using atomic force microscope tips. In these devices, the current is forced to squeeze into the path between the two cuts rather than flow directly through the graphene sheet. We observe that the gate voltages with minimum current shift toward zero bias as the sizes of the dual-cut regions increase. These phenomena suggest that the Fermi levels in the dual-cut regions are shifted toward the Dirac points after the mechanical scraping process. (C) 2014 AIP Publishing LLC.
Field effect of in-plane gates with different gap sizes on the Fermi level tuning of graphene channels
(2014-05-05)
Lin, Meng-Yu
;
Chen, Yen-Hao
;
Wang, Cheng-Hung
;
Su, Chen-Fung
;
Chang, Shu-Wei
Tuning of the Fermi level is investigated in graphene channels using two in-plane gates with significantly different-sized isolating gaps. While the n-type tuning was achievable in both schemes, the wide-gap device had an enhanced minimum drain current and less prominent current modulation than the narrow-gap device. In addition, further p-type tuning was not observed in the wide-gap device at negative gate biases. These phenomena indicated that both devices had distinct field-strength dependences and Fermi level tuning effects, which may be critical for the practical design of devices. (C) 2014 AIP Publishing LLC.
Optical Properties of InN-Based Photo detection Devices
(2015)
Hsu, Lung-Hsing
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Lin, Chien-Chung
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Hwang, Yi-Chia
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Su, Chen-Fung
;
Lin, Shih-Yen
The InN capped with GaN structures is promising for extended visible and infrared absorption. The low growth temperature of GaN/InN epitaxy was fabricated by a low-pressure metal organic chemical vapor deposition system. The strain effect and mixed InxGa1-xN complex of the GaN/InN layer were investigated via Raman and photoluminescence (PL) measurements. The capping GaN with similar growth temperature of previous InN growth induces the gallium diffusion mechanism to form InxGa1-xN complex. The blue-shift phenomenon of multiple GaN/InN peaks with increasing growth temperature was attributed to residual strain and higher Ga content of InGaN. A ZnO/GaN/InN photodetection device is demonstrated with extended IR response, and the quantum efficiency is 2.28%.
The growth mechanisms of graphene directly on sapphire substrates by using the chemical vapor deposition
(2014-06-14)
Lin, Meng-Yu
;
Su, Chen-Fung
;
Lee, Si-Chen
;
Lin, Shih-Yen
;
光電工程學系
Uniform and large-area graphene films grown directly on sapphire substrates by using a low-pressure chemical vapor deposition system are demonstrated in this paper. The evolution process and the similar Raman spectra of the samples with different growth durations have confirmed that the continuous graphene film is formed by graphene flakes with similar sizes. The layer-by-layer growth mechanism of this approach is attributed to the preferential graphene deposition on sapphire surfaces. The etching effect of H-2 gas is demonstrated to be advantageous for the larger graphene grain formation. The smooth surface of substrates is also proved to be a key parameter for continuous graphene film formation with better crystalline quality. (C) 2014 AIP Publishing LLC.
Toward epitaxially grown two-dimensional crystal hetero-structures: Single and double MoS2/graphene hetero-structures by chemical vapor depositions
(2014-08-18)
Lin, Meng-Yu
;
Chang, Chung-En
;
Wang, Cheng-Hung
;
Su, Chen-Fung
;
Chen, Chi
Uniform large-size MoS2/graphene hetero-structures fabricated directly on sapphire substrates are demonstrated with layer-number controllability by chemical vapor deposition (CVD). The cross-sectional high-resolution transmission electron microscopy (HRTEM) images provide the direct evidences of layer numbers of MoS2/graphene hetero-structures. Photo-excited electron induced Fermi level shift of the graphene channel are observed on the single MoS2/graphene hetero-structure transistors. Furthermore, double hetero-structures of graphene/MoS2/graphene are achieved by CVD fabrication of graphene layers on top of the MoS2, as confirmed by the cross-sectional HRTEM. These results have paved the possibility of epitaxially grown multi-hetero-structures for practical applications. (C) 2014 AIP Publishing LLC.