Browsing by Author "Chu, Yung-Ching"

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Contact resistance reduction on layered MoS2 by Ar plasma pre-treatment
(2016)
Ho, Yen-Teng
;
Chu, Yung-Ching
;
Jong, Chao An
;
Chen, Hung-Yi
;
Lin, Meng-Wei
The effect of resistance (Rc) reduction of Ti/Au contact on MoS2 by ICP Ar plasma pretreatment is presented. The lowest Rc of 1.72 ohm-cm was achieved with the ICP treatment condition of 50W (ICP) /2W (chuck) for 10 sec. Compared with the contact without treatment (19.6 ohm-cm), the Rc improves over 10 times, demonstrating the advantage of Ar plasma pre-treatment on MoS2 contact.
Electrical Properties of Compound 2D Semiconductor Mo1-xNbxS2
(2018-01-01)
Lu, Peng
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Ho, Yen Teng
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Chu, Yung-Ching
;
Zhang, Ming
;
Chien, Po-Yen
In order for TMD such as molybdenum disulfide (MoS2) to be useful for semiconductor industry, a controllable doping process is required. MoS2 with substitutional Nb shows a p-type behavior compared to the n-type characteristics of nominal films. In this work, the role of Nb in MoS2 will be examined, and a precise hole concentration control technique is demonstrated. Multi-layered Mo1-xNbxS2 samples with accurately controlled Nb mole fraction are synthesized. Electrical characterization and material analysis are performed to quantify the impact of Nb with mole fraction from 3.5% to 11%. The effective carrier concentration (p) and the ective hole mobility (mu(eff)) are found to be highly non-linear with respect to Nb mole fraction. Scanning Tunneling Microscope (STM) shows that the bandgap of the 2D transition metal dichalcogenide (TMD) is reduced by high mole fraction Nb. Therefore, Mo1-xNbxS2 can be considered as a compound TMD semiconductor.
Layered MoS2 grown on c-sapphire by pulsed laser deposition
(2015-03-01)
Ho, Yen-Teng
;
Ma, Chun-Hao
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Luong, Tien-Tung
;
Wei, Lin-Lung
;
Yen, Tzu-Chun
Layered growth of molybdenum disulphide (MoS2) was successfully achieved by pulsed laser deposition (PLD) method on c-plane sapphire substrate. Growth of monolayer to a few monolayer MoS2, dependent on the pulsed number of excimer laser in PLD is demonstrated, indicating the promising controllability of layer growth. Among the samples with various pulse number deposition, the frequency difference (A1gE12g) in Raman analysis of the 70 pulse sample is estimated as 20.11 cm(1), suggesting a monolayer MoS2 was obtained. Two-dimensional (2D) layer growth of MoS2 is confirmed by the streaky reflection high energy electron diffraction (RHEED) patterns during growth and the cross-sectional view of transmission electron microscopy (TEM). The in-plane relationship, (0006) sapphire//(0002) MoS2 and inline image sapphire//inline imageMoS(2) is determined. The results imply that PLD is suitable for layered MoS2 growth. Additionally, the oxide states of Mo 3d core level spectra of PLD grown MoS2, analysed by X-ray photoelectron spectroscopy (XPS), can be effectively reduced by adopting a post sulfurization process. (C) 2015 WILEY-VCH Verlag GmbH &Co. KGaA, Weinheim
POST SULFURIZATION EFFECT ON THE MOS2 GROWN BY PULSED LASER DEPOSITION
(2016)
Ho, Yen-Teng
;
Yen, Tzu-Chun
;
Luong, Tien-Tung
;
Wei, Lin-Lung
;
Tu, Yung-Yi
Two inches size with high quality layered growth of MoS2 was achieved by PLD on c-plane sapphire substrate. 2-3 monolayer MoS2 was obtained within 2 inches wafer estimated from Raman analysis and confirmed by cross-sectional view of TEM. Additionally, the oxide states of Mo 3d core level spectra of MoS2, analyzed by XPS, can be effectively reduced by adopting a post sulfurization process in H2S. The post process also improve the photoluminescence (PL) of MoS2 as well as the electrical characteristic of MoS2 FET due to elimination the Mo oxide in the grown film.
Reliable Doping Technique for WSe2 by W: Ta Co-Sputtering Process
(2016)
Chien, Po-Yen
;
Zhang, Ming
;
Huang, Shao-Chia
;
Lee, Min-Hung
;
Hsu, Hung-Ru
The electrical and material properties of WSe2 doped by W:Ta co-sputtering process were examined. High acceptor doping concentration (6x10(13)cm(-2)) and good effective hole mobility (16.5cm(2)/Vs) were realized. As a result, low sheet resistance (17k Omega/sq) and contact resistance with Pd metal (11.4k Omega-mu m) were measured using TLM structures.
Synthesis of Wafer-Scale WSe2 by WOx Selenization on SiO2 / Si Substrates
(2016)
Chu, Yung-Ching
;
Jong, Chao-An
;
Ho, Yen-Teng
;
Zhang, Ming
;
Chien, Po-Yen
Scalable synthesis of thin tungsten diselenide (WSe2) films on 4-inch silicon substrate with 80 nm silicon dioxide (SiO2) is demonstrated. Cross-sectional transmission electron microscopy (TEM) reveals good control of WSe2 layers. Raman spectroscopy confirms high quality crystal of WSe2 is achieved. Back-gated field-effect transistors (FETs) fabricated on these thin films exhibit p-channel characteristics with a good on/off current ratio larger than 1.2 x 10(2).
WAFER SIZE MOS2 WITH FEW MONOLAYER SYNTHESIZED BY H2S SULFURIZATION
(2017-01-01)
Ho, Yen-Teng
;
Chu, Yung-Ching
;
Wei, Lin-Lung
;
Luong, Tien-Tung
;
Lin, Chih-Chien
Wafer sized, high quality continuous fihns would be a key demand for MoS2 implemented in circuit application. In this study, the growth of few monolayer Mo-S2 on 4 inches SiO2/Si substrate were demonstrated. The MoS2 thin films were synthesized by sulfurized in a furnace from the ultra-thin MoO3 starting materials by using H2S. The obtained MoS2 thin film examined by Raman analysis and Photoluminescence (PL), shows the semiconductor nature with direct transition peaks of 1.86 eV and 1.99 eV. The 4 5 monolayer of MoS2 with thickness around 2.6 nm is confirmed by cross-sectional view of transmission electron microscopy (TEM). Additionally, the DC characteristics of MoS2 MOSFETs exhibit at least 2 order in on/off current ratio, demonstrating the feasibility for circuit application.