Browsing by Author "Zhang, Qun"

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Enhanced stability of thin film transistors with double-stacked amorphous IWO/IWO:N channel layer
(2018-06-01)
Lin, Dong
;
Pi, Shubin
;
Yang, Jianwen
;
Tiwari, Nidhi
;
Ren, Jinhua
In this work, bottom-gate top-contact thin film transistors with double stacked amorphous IWO/ IWO:N channel layer were fabricated. Herein, amorphous IWO and N-doped IWO were deposited as front and back channel layers, respectively, by radio-frequency magnetron sputtering. The electrical characteristics of the bi-layer-channel thin film transistors (TFTs) were examined and compared with those of single-layer-channel (i.e., amorphous IWO or IWO:N) TFTs. It was demonstrated to exhibit a high mobility of 27.2 cm(2)V(-1 )s(-1) and an on/off current ratio of 10(7).Compared to the single peers, bi-layer a-IWO/IWO:N TFTs showed smaller hysteresis and higher stability under negative bias stress and negative bias temperature stress. The enhanced performance could be attributed to its unique double-stacked channel configuration, which successfully combined the merits of the TFTs with IWO and IWO:N channels. The underlying IWO thin film provided percolation paths for electron transport, meanwhile, the top IWO:N layer reduced the bulk trap densities. In addition, the IWO channel/gate insulator interface had reduced defects, and IWO:N back channel surface was insensitive to the ambient atmosphere. Overall, the proposed bi-layer a-IWO/IWO:N TFTs show potential for practical applications due to its possibly long-term serviceability.
Influences of Nitrogen Doping on the Electrical Characteristics of Indium-Zinc-Oxide Thin Film Transistors
(2016-12)
Han, Yanbing
;
Yan, Hai
;
Tsai, Yun-Chu
;
Li, Yan
;
Zhang, Qun
Thin film transistors (TFTs) with nitrogen doped amorphous indium-zinc-oxide (a-IZO:N) as the channel layer were prepared by rf magnetron sputtering with an argon, oxygen, and nitrogen gas mixture at room temperature. XRD measurements confirm the amorphous structure of a-IZO:N thin film and AFM verifies its uniformity. Transmittance curves show that nitrogen doping in a-IZO films can narrow the optical band gap and suppress oxygen vacancies, which is also proved by XPS. When the nitrogen flow rate is 4 SCCM, a-IZO TFTs possess optimized the characteristics, with saturation mobility 24.67 cm(2)V(-1)s(-1), subthreshold swing 0.41 V/decade, on/off ratio 1.7 x 10(9), and threshold voltage -14.46 V. Threshold voltages shift from -22.76 to -9.59 V as the nitrogen flow rate raises from 0 to 6.5 SCCM. The positive gate bias stability and negative bias illumination stability of a-IZO:N TFT are also improved with the nitrogen flow rate of 4 and 2.5 SCCM, respectively.
Stability of Amorphous Indium-Tungsten Oxide Thin-Film Transistors Under Various Wavelength Light Illumination
(2016-04)
Yang, Zhao
;
Meng, Ting
;
Zhang, Qun
;
Shieh, Han-Ping D.
;
光電工程學系
Amorphous indium-tungsten oxide (a-IWO) thin-film transistors (TFTs) were prepared by the RF-sputtering method, and their electrical stability under various conditions of wavelength light illumination was investigated. It was found that the electrical stability of the devices was dependent on the light wavelength and the illumination time. The analysis reveals that the improvement of the light illumination stability of the a-IWO-TFTs is ascribed to the oxygen vacancies transition between V-O-V-O(+) and V-O-V-O(2+) under different wavelength illuminations.
Stability study of indium tungsten oxide thin-film transistors annealed under various ambient conditions
(2017-02-01)
Qu, Mingyue
;
Chang, Chih-Hsiang
;
Meng, Ting
;
Zhang, Qun
;
Liu, Po-Tsun
Amorphous tungsten-doped indium oxide thin-film transistors (a-IWO-TFTs) are prepared by RF sputtering and annealed in air, O-2, and N-2 ambients. The influence of annealing ambient on the electrical characteristics and stability of the a-IWO-TFTs is investigated. It is found that the characteristics and stability are improved in O-2 and N-2 ambients, which can be explained by the reduction of structural defects and oxygen vacancies. When annealed in O-2, the TFT device with saturation mobility of 27.55cm(2)V(-1)s(-1), threshold voltage of 0.5V and drain current on-off ratio of 10(8) is obtained. After an applied V-GS of 25 and -25V for 2000s in darkness, the values of Delta V-th are 4.5 and -0.92V, respectively.
The Influence of Annealing Temperature on Amorphous Indium-Zinc-Tungsten Oxide Thin-Film Transistors
(2018-03-21)
Fu, Ruofan
;
Yang, Jianwen
;
Chang, Wei-Chiao
;
Chang, Wei-Cheng
;
Chang, Chien-Min
In this paper, the influence of annealing temperature on amorphous indium-zinc-tungsten-oxide (a-IZWO) thin-film transistors (TFTs) is investigated. As the annealing temperature increases, the IZWO films maintain an amorphous state, which is conducive to the uniformity of the TFT. The field effect mobility of the device increases as a function of annealing temperature and reaches 16.2cm(2)V(-1)s(-1) at 300 degrees C, along with an on/off current ratio of 1.6x10(8). Meanwhile, the corresponding positive bias stability is improved, as confirmed by the fact that the threshold voltage shift value reduces to 0.4V after being stressed for 1500s. This result can be ascribed to the decrease in electrons captured by the deep defects in a-IZWO TFTs.