Monthly Archives: November 2014

Effect of annealing temperature on structural and electrical properties of high- ? YbTi x O y gate dielectrics for InGaZnO thin film transistors

This paper describes the effect of annealing temperature on the structural properties and electrical characteristics of high? ? YbTi x O y gate dielectrics for indium?gallium?zinc?oxide (IGZO) thin-film transistors (TFTs). X-ray diffraction, x-ray photoelectron spectroscopy and atomic force microscopy were used to study the structural, chemical and morphological features, respectively, of these dielectric films annealed at 200, 300 and 400 ?C. The YbTi x O y IGZO TFT that had been annealed at 400 ?C exhibited better electrical characteristics, such as a small threshold voltage of 0.53 V, a large field-effect mobility of 19.1 cm 2 V ?1 s ?1 , a high I on / I off ratio of 2.8???10 7 , and a low subthreshold swing of 176 mV dec. ?1 , relative to those of the systems that had been subjected to other annealing conditions. This result su...

Effect of annealing temperature on structural and electrical properties of high- κ YbTi x O y gate dielectrics for InGaZnO thin film transistors

This paper describes the effect of annealing temperature on the structural properties and electrical characteristics of high– κ YbTi x O y gate dielectrics for indium–gallium–zinc–oxide (IGZO) thin-film transistors (TFTs). X-ray diffraction, x-ray photoelectron spectroscopy and atomic force microscopy were used to study the structural, chemical and morphological features, respectively, of these dielectric films annealed at 200, 300 and 400 °C. The YbTi x O y IGZO TFT that had been annealed at 400 °C exhibited better electrical characteristics, such as a small threshold voltage of 0.53 V, a large field-effect mobility of 19.1 cm 2 V −1 s −1 , a high I on / I off ratio of 2.8 × 10 7 , and a low subthreshold swing of 176 mV dec. −1 , relative to those of the systems that had been subjected to other annealing conditions. This result su...

Comparison of structural and electrical properties of Lu2O3 and Lu2TiO5 gate dielectrics for α-InGaZnO thin-film transistors

We compared the structural properties and electrical characteristics of high-κ Lu2O3 and Lu2TiO5 gate dielectrics for amorphous indium-gallium-zinc oxide (α-InGaZnO) thin-film transistor (TFT) applications. The Lu2O3 film has a strong Lu2O3 (400) peak in the X-ray diffraction pattern, while the Lu2TiO5 sample shows a relatively weak Lu2TiO5 (102) peak. Atomic force microscopy reveals that the Lu2O3 dielectric exhibits a rougher surface (about three times) than Lu2TiO5 one. In X-ray photoelectron spectroscopy analysis, we found that the intensity of the O 1s peak corresponding to Lu(OH)x for Lu2O3 film was higher than that of Lu2TiO5 film. Furthermore, compared with the Lu2O3 dielectric, the α-InGaZnO TFT using the Lu2TiO5 gate dielectric exhibited a lower threshold voltage (from 0.43 to 0.25 V), a higher Ion/Ioff current ratio (from 3.5 × 106 to 1.3 × 108), a smaller subthreshold swing (from 276 to 130 mV/decade), and a larger field-effect mobility (from 14.5 to 24.4 cm2/V s). These results are probably due to the incorporation of TiOx into the Lu2O3 film to form a Lu2TiO5 structure featuring a smooth surface, a low moisture absorption, a high dielectric constant, and a low interface state density at the oxide/channel interface. Furthermore, the stability of Lu2O3 and Lu2TiO5 α-InGaZnO TFTs was investigated under positive gate-bias stress (PGBS) and negative gate-bias stress (NGBS). The threshold voltage of the TFT performed under NGBS is more degradation than that under PGBS. This behavior may be attributed to the electron charge trapping at the dielectric–channel interface under PGBS, whereas the oxygen vacancies occurred in the InGaZnO under NGBS.

Flexible electrophoretic display driven by solution-processed organic TFT with highly stable bending feature

Publication date: December 2014 Source:Organic Electronics, Volume 15, Issue 12 Author(s): Chang Bum Park , Kyung Min Kim , Jung Eun Lee , HyungIl Na , Soon Sung Yoo , Myoung Su Yang A highly reliable solution-processed organic thin film transistor (OTFT) and its backplane are fabricated for a flexible electrophoretic display (EPD) on a plastic substrate. The all-solution-processed OTFT with an anthradithiophene derivative exhibits excellent bendability for an extreme cyclic bending stress of 100,000 cycles with a radius of 4mm without a significant change in its electrical properties. Process technology using an industrially suitable Cu electrode has also been developed to replace the high work-function material as well as to obtain a low-resistance signal line in the OTFT array. The present TFT exhibits a highly stable threshold-voltage shift (ΔVT ) of less than 2V under long-span bias stress exposure with competitive performance to serve as a switching device in an EPD, even if it was fabricated at a low temperature of less than 140°C. An ultra-thin flexible OTFT backplane with Cu electrodes has been successfully achieved via plastic processing technology by releasing a polyimide (PI) substrate from glass without degradation in device performance, which demonstrates a commercially suitable handling process of the thin plastic for flexible device applications. Finally, we demonstrate a 3.5-inch flexible EPD with good bendability, which indicates the great potential of solution-processed organic TFTs as a promising element of flexible electronics as well as a backplane unit from the viewpoint of commercialization. Graphical abstract

Flexible nonvolatile organic ferroelectric memory transistors fabricated on polydimethylsiloxane elastomer

Publication date: January 2015 Source:Organic Electronics, Volume 16 Author(s): Soon-Won Jung , Jeong-Seon Choi , Jae Bon Koo , Chan Woo Park , Bock Soon Na , Ji-Young Oh , Sang Chul Lim , Sang Seok Lee , Hye Yong Chu , Sung-Min Yoon The flexible organic ferroelectric nonvolatile memory thin film transistors (OFMTs) were fabricated on polydimethylsiloxane (PDMS) elastomer substrates, in which an organic ferroelectric poly(vinylidene-trifluoroethylene) and an organic semiconducting poly(9,9-dioctylfluorene-co-bithiophene) layers were used as gate insulator and active channel, respectively. The carrier mobility, on/off ratio, and subthreshold swing of the OFMTs fabricated on PDMS showed 5×10−2 cm2 V−1 s−1, 7.5×103, and 2.5V/decade, respectively. These obtained values did not markedly change when the substrate was bent with a radius of curvature of 0.6cm. The memory on/off ratio was initially obtained to be 1.5×103 and maintained to be 20 even after a lapse of 2000s. The fabricated OFMTs exhibited sufficiently encouraging device characteristics even on the PDMS elastomer to realize mechanically stretchable nonvolatile memory devices. Graphical abstract

High-Performance, Low-Temperature Solution Processed Amorphous Indium Oxide Thin-Film Transistors Using a Volatile Nitrate Precursor

J. Mater. Chem. C, 2014, Accepted ManuscriptDOI: 10.1039/C4TC01568A, PaperChih-hung Chang, Changho Choi, Seungyeol Han, Liang-Yu Lin, Chun-Cheng Cheng, Zhen Fang, Yu-Wei SuIn this study, we fabricated amorphous indium oxide thin film transistors (TFTs) on the display glass at various annealing temperature from 200 [degree]C to 300 [degree]C. Using a volatile nitrate...The content of this RSS Feed (c) The Royal Society of Chemistry

Sol-gel titanium-silicon oxide/organic hybrid dielectric for low-voltage organic thin film transistors

J. Mater. Chem. C, 2014, Accepted ManuscriptDOI: 10.1039/C4TC02564D, CommunicationBo-Xuan Yang, Chih-Yao Tseng, Anthony S. T. Chiang, Cheng-Liang LiuWe report on the fabrication of low-voltage operating pentacene-based organic thin film transistors (OTFTs), composted of a high k gate dielectric made from titanium-silicon oxide/organic hybrid materials covered with a...The content of this RSS Feed (c) The Royal Society of Chemistry

Physical origin of gate voltage-dependent drain–source capacitance in short-channel MOSFETs

For the first time, it is revealed that the physical origin of the gate-source voltage (Vgs)-dependent drain-source capacitance in short-channel metal-oxide semiconductor field-effect transistors (MOSFETs) comes from the depletion capacitance components between the drain and channel end in the saturation region. On the basis of this origin, it is newly found that the Vgs-dependent channel resistance should be connected in series with the drain-source capacitance to model the high-frequency (HF) response of the intrinsic output capacitance. The accuracy of an improved MOSFET model, including the channel resistance, is validated by observing the excellent agreement with the measured S-parameters in the wide range of Vgs up to 40 GHz.

High power factor LED power supply based on SEPIC converter

A single-ended primary inductor converter (SEPIC)-based light-emitting diode (LED) power supply, which can achieve power factor correction (PFC) and constant-current drive for LED in the critical conduction mode (CRM), is presented. The circuit principle is described in detail. Meanwhile the formulas for metal-oxide semiconductor field-effect transistor switch-on time, switching frequency and the main influences of power factor are given. Experimental results show that the power can drive the LED with high efficiency by virtue of its high power factor, low power loss and stable output. Furthermore, it can be applied to low-power lighting occasions with simple structure and high reliability.

Effects of thermal annealing on the electrical characteristics of In-Ga-Zn-O thin-film transistors with Al 2 O 3 gate dielectric

We studied how the performance of In–Ga–Zn–O (IGZO) thin film transistors (TFTs) with Al 2 O 3 gate insulator was affected by post-fabrication annealing temperature and annealing time. At a fixed annealing time of 2 min, the IGZO TFT exhibited the best transfer and output characteristics in the case of 300 °C in N 2 atmosphere, which is attributed to the achievement of appropriate carrier concentration and Hall mobility in the IGZO film. Further, it was found that both of the carrier concentration and Hall mobility in the IGZO film increased with the increment of annealing temperature. For the annealing temperature of 300 °C, the performance of the IGZO TFT was further improved by extending annealing time to 5 min, i.e., the field effect mobility, sub-threshold swing and on/off current ratio were 11.6 cm 2 /(V · s), 0.42 V dec −1 and 10 6 , respectively. The underlying mechanism was discussed.