Browsing by Author "Woo, Jason C. S."

Now showing 1 - 2 of 2

Electrical Properties of Compound 2D Semiconductor Mo1-xNbxS2
(2018-01-01)
Lu, Peng
;
Ho, Yen Teng
;
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.
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).