Browsing by Author "Chen, Jun"

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Atomic-Scale Fabrication of In-Plane Heterojunctions of Few-Layer MoS2 via In Situ Scanning Transmission Electron Microscopy
(1970-01-01)
Tai, Kuo-Lun
;
Huang, Chun-Wei
;
Cai, Ren-Fong
;
Huang, Guan-Min
;
Tseng, Yi-Tang
Layered MoS2 is a prospective candidate for use in energy harvesting, valleytronics, and nanoelectronics. Its properties strongly related to its stacking configuration and the number of layers. Due to its atomically thin nature, understanding the atomic-level and structural modifications of 2D transition metal dichalcogenides is still underdeveloped, particularly the spatial control and selective precision. Therefore, the development of nanofabrication techniques is essential. Here, an atomic-scale approach used to sculpt 2D few-layer MoS2 into lateral heterojunctions via in situ scanning/transmission electron microscopy (STEM/TEM) is developed. The dynamic evolution is tracked using ultrafast and high-resolution filming equipment. The assembly behaviors inherent to few-layer 2D-materials are observed during the process and included the following: scrolling, folding, etching, and restructuring. Atomic resolution STEM is employed to identify the layer variation and stacking sequence for this new 2D-architecture. Subsequent energy-dispersive X-ray spectroscopy and electron energy loss spectroscopy analyses are performed to corroborate the elemental distribution. This sculpting technique that is established allows for the formation of sub-10 nm features, produces diverse nanostructures, and preserves the crystallinity of the material. The lateral heterointerfaces created in this study also pave the way for the design of quantum-relevant geometries, flexible optoelectronics, and energy storage devices.
Electrical and Photosensitive Characteristics of a-IGZO TFTs Related to Oxygen Vacancy
(2011-04-01)
Yao, Jianke
;
Xu, Ningsheng
;
Deng, Shaozhi
;
Chen, Jun
;
She, Juncong
The electrical and photosensitive characteristics of amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistors (TFTs) related to the oxygen vacancies V(O) are discussed. With the filling of V(O) of ratio from 14 to 8, the electron density of the a-IGZO channel decreases from 7.5 to 3.8 (x10(16) cm(-3)); the saturation mobility of the TFT decreases from 3.1 to 1.4 cm(2)/(V . s); the threshold voltage increases from 7 to 11 V for the TFT with a lower on-current; and the subthreshold slope increases from 2.4 to 4.4 V/dec for the TFT with a higher interface defect density of 4.9 x 10(11) cm(-2), the worst electrical stability of Delta V(th) similar to 10 V, and a hysteresis-voltage decrease from 3.5 to 2 V. The photoreaction properties of a-IGZO TFTs are also sensitive to the oxygen-content-related absorption of the a-IGZO channel. With the lowest content of oxygen in the channel, the TFT has the largest photocurrent gain of 50 mu A (V(g) = 30 V; V(d) = 10 V) and decrease in V(th) (|Delta V(th)| similar to 5 V) at a high light intensity. The light-induced change of TFT characteristics is totally reversible with the time constant for recovery of about 2.5 h.