Browsing by Author "Yu, Tung-Yuan"

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Carbon-Coated Porous Aluminum Oxides Used as Spacer Overlayers to Reduce Secondary Electron Emission for Field Emission Display Applications
(2013-07-01)
Yu, Tung-Yuan
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Pan, Fu-Ming
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Chen, Cheng-Li
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Chen, Te-Ming
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Chen, Tsung-Han
Porous surface structures can mitigate the charging effect of vacuum spacers of field-emission flat panel display due to the abundance of secondary electrons (SEs) emitted from the spacers during field emission display (FED) operation. In this study, we fabricated porous anodic aluminum oxide (AAO) overlayers on glass substrates to examine the effect of carbon deposition on the reduction of SE emissions. This paper reports that uniform AAO overlayers can be simultaneously prepared on both sides of a glass plate 2 x 10 cm(2) in size. The SE emission of the AAO overlayer was examined by using an Auger electron microscope. When a small amount of carbon is evaporation-deposited on the as-prepared AAO overlayer, the SE emission efficiency is significantly decreased and the reduction in the SE emission is ascribed to the low SE yield of the carbon deposit and the suppression of SE escape from the narrowed pore channels. However, a heavy deposition of carbon results in a smaller surface roughness of the AAO overlayer, thereby increasing SE emission. The carbon-coated AAO overlayer demonstrates favorable electrical and mechanical properties, making it suitable for use in FED vacuum spacers. (C) 2013 The Japan Society of Applied Physics
Dark current suppression of amorphous selenium based photosensors by the ZnO hole blocking layer
(2014-05-01)
Yu, Tung-Yuan
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Pan, Fu-Ming
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Chang, Cheng-Yi
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Hu, Tien
;
Chen, Jenn-Fang
To study the influence of defects in the hole blocking layer (HBL) on the dark current of amorphous selenium (a-Se) based photosensors, we prepared ZnO thin films by reactive sputter deposition (RSD) for the use as the HBL of the photosensors. The ZnO HBL layers prepared with different oxygen flow rates were characterized by X-ray photoelectron spectroscopy, Raman scattering analysis and photoluminescence, indicating that the density of oxygen vacancies in the ZnO thin films is significantly affected by the oxygen flow rate. The deep level transient spectroscopy measurement reveals two hole trap levels present in the RSD deposited ZnO thin films; one is at 0.94 eV and the other at 0.24 eV above the valence band edge. The electrical performance of the a-Se photosensor is largely influenced by the amount of oxygen vacancies in the ZnO thin film. The a-Se photosensor with the ZnO HBL of the most oxygen vacancies has the lowest dark current and demonstrates the highest breakdown field. (C) 2014 Elsevier B.V. All rights reserved.
Effective N-methyl-2-pyrrolidone wet cleaning for fabricating high-performance monolayer MoS2 transistors
(2019-02-01)
Chen, Po-Chun
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Lin, Chih-Pin
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Hong, Chuan-Jie
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Yang, Chih-Hao
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Lin, Yun-Yan
Two-dimensional semiconductors, such as MoS2 are known to be highly susceptible to diverse molecular adsorbates on the surface during fabrication, which could adversely affect device performance. To ensure high device yield, uniformity and performance, the semiconductor industry has long employed wet chemical cleaning strategies to remove undesirable surface contaminations, adsorbates, and native oxides from the surface of Si wafers. A similarly effective surface cleaning technique for two-dimensional materials has not yet been fully developed. In this study, we propose a wet chemical cleaning strategy for MoS2 by using N-methyl-2-pyrrolidone. The cleaning process not only preserves the intrinsic properties of monolayer MoS2, but also significantly improves the performance of monolayer MoS2 field-effect-transistors. Superior device on current of 12 Am-1 for a channel length of 400 nm, contact resistance of 15 km, field-effect mobility of 15.5 cm(2)V(-1)s(-1), and the average on-off current ratio of 10(8) were successfully demonstrated
Lateral amorphous selenium metal-insulator-semiconductor-insulator-metal photodetectors using ultrathin dielectric blocking layers for dark current suppression
(2016-12-21)
Chang, Cheng-Yi
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Pan, Fu-Ming
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Lin, Jian-Siang
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Yu, Tung-Yuan
;
Li, Yi-Ming
We fabricated amorphous selenium (a-Se) photodetectors with a lateral metal-insulator-semiconductor-insulator-metal (MISIM) device structure. Thermal aluminum oxide, plasma-enhanced chemical vapor deposited silicon nitride, and thermal atomic layer deposited (ALD) aluminum oxide and hafnium oxide (ALD-HfO2) were used as the electron and hole blocking layers of the MISIM photodetectors for dark current suppression. A reduction in the dark current by three orders of magnitude can be achieved at electric fields between 10 and 30 V/mu m. The effective dark current suppression is primarily ascribed to electric field lowering in the dielectric layers as a result of charge trapping in deep levels. Photogenerated carriers in the a-Se layer can be transported across the blocking layers to the Al electrodes via Fowler-Nordheim tunneling because a high electric field develops in the ultrathin dielectric layers under illumination. Since the a-Se MISIM photodetectors have a very low dark current without significant degradation in the photoresponse, the signal contrast is greatly improved. The MISIM photodetector with the ALD-HfO2 blocking layer has an optimal signal contrast more than 500 times the contrast of the photodetector without a blocking layer at 15 V/mu m. Published by AIP Publishing.
Thermal stability and photoconductive properties of photosensors with an alternating multilayer structure of amorphous Se and AsxSe1-x
(2015-07-28)
Yu, Tung-Yuan
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Pan, Fu-Ming
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Chang, Cheng-Yi
;
Lin, Jian-Siang
;
Huang, Wen-Hsien
In this study, we fabricated a-Se based photosensors with an alternating multilayer structure of a-Se and AsxSe1-x by rotational thermal evaporation deposition. During the deposition of the amorphous AsxSe1-x layers, As diffuses into the underlying a-Se component layers, thereby improving the thermal stability of the multilayer photosensor and thus increasing the breakdown electric field. Although the As doping introduces carrier traps in the a-Se layers, the multilayer photosensors demonstrate an effective quantum efficiency comparable to the single-layered a-Se sensor under the blue light illumination but are with a lower dark current density by two orders of magnitude. In addition to the top AsxSe1-x layer being functioning as an electron blocking layer, carrier traps present in the multilayer structure may decrease the drift mobility of charge carriers and disturb electric field distribution in the photosensors, thereby suppressing the dark current. (C) 2015 AIP Publishing LLC.