Browsing by Author "Chiu, Yu-Chuan"

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Annealing effects on resistive switching of IGZO-based CBRAM devices
(2020-10-01)
Gan, Kai-Jhih
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Liu, Po-Tsun
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Ruan, Dun-Bao
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Chiu, Yu-Chuan
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Sze, Simon M.
In this study, the impact of post-oxide deposition annealing on performance of IGZO-based conductive-bridging random access memory (CBRAM) is reported. It is found that besides the distinct reduction in resistive switching parameters of SET/RESET voltages, their dispersions, and the resistance ratio of high-resistance state to low-resistance state can be improved after N-2 annealing. The annealing effects on enhancing of the resistive switching properties are investigated by x-ray photoelectron spectra. It can be considered that the formation of the filament is better controlled by the increase of oxygen vacancies in the switching layer, which is the main reason for the improvement of resistive switching characteristics.
Bipolar resistive switching characteristics of tungsten-doped indium-zinc oxide conductive-bridging random access memory
(2019-08-01)
Gan, Kai-Jhih
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Liu, Po-Tsun
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Lin, Sheng-Jie
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Ruan, Dun-Bao
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Chien, Ta-Chun
The purpose of this work is to develop a reliable amorphous tungsten-doped indium-zinc oxide based conductive-bridging random access memory (CBRAM). The device with Cu/TiW/InWZnO/Pt structure exhibits stable bipolar resistive switching behavior. The device also shows good non-volatile memory characteristics, such as low operation voltage, on/off resistance ratio (similar to 10(2)), high switching endurance (more than 5 x 10(2) cycles). The temperature coefficient of resistance in the conductive filament confirms that an electro-chemical metallization (ECM) based conduction is observed in the InWZnO device. Furthermore, the temperature retention characteristics and the current transport mechanisms are also investigated. According to our experiments, we propose a model to explain the resistive switching phenomenon observed in our devices. These results have given a great potential for the transparent amorphous oxide semiconductor (TAOS)-based material utilizing in CBRAM stacks and integrating into the display circuits for future memory-in-pixel applications.
Development of a mobile application (App) to delineate "digital chronotype" and the effects of delayed chronotype by bedtime smartphone use
(2019-03-01)
Lin, Yu-Hsuan
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Wong, Bo-Yu
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Lin, Sheng-Hsuan
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Chiu, Yu-Chuan
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Pan, Yuan-Chien
The widespread use and deep reach of smartphones motivate the use of mobile applications to continuously monitor the relationship between circadian system, individual sleep patterns, and environmental effects. We selected 61 adults with 14-day data from the "Know Addiction" database. We developed an algorithm to identify the "sleep time" based on the smartphone behaviors. The total daily smartphone use duration and smartphone use duration prior to sleep onset were identified respectively. We applied mediation analysis to investigate the effects of total daily smartphone use on sleep through pre-sleep use (PS). The results showed participants' averaged pre-sleep episodes within 1 h prior to sleep are 2.58. The duration of three pre-sleep uses (PS1-3) maybe a more representative index for smartphone use before sleep. Both total daily duration and the duration of the last three uses prior to sleep of smartphone use significantly delayed sleep onset, midpoint of sleep and reduced total sleep time. One hour of increased smartphone use daily, delays the circadian rhythm by 3.5 min, and reduced 5.5 min of total sleep time (TST). One hour of increased pre-sleep smartphone use delayed circadian rhythm by 1.7 min, and reduced 39 s of TST. The mediation effects of PSI 3 significantly impacted on these three sleep indicators. PS1-3 accounted for 14.3% of total daily duration, but the proportion mediated of delayed circadian rhythm was 44.0%. We presented "digital chronotype" with an automatic system that can collect high temporal resolution data from naturalistic settings with high ecological validity. Smartphone screen time, mainly mediated by pre-sleep use, delayed the circadian rhythm and reduced the total sleep time.
Effect of Annealing Treatment on Performance of Ga2O3 Conductive-Bridging Random-Access Memory
(1970-01-01)
Gan, Kai-Jhih
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Liu, Po-Tsun
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Ruan, Dun-Bao
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Hsu, Chih-Chieh
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Chiu, Yu-Chuan
The effect of annealing on the performance of conductive-bridging random-access memory (CBRAM) with an amorphous gallium oxide (a-Ga2O3) switching layer has been studied. After annealing at 200 degrees C in N-2, a significant improvement of the bipolar resistive switching characteristics was observed. The a-Ga2O3 CBRAM showed good memory performance, with high switching endurance (up to 7.5 x 10(2) cycles) and high thermal stability. The resistive switching stability and electrical uniformity were also obviously improved. The memory window remained above 10(5) over 7.5 x 10(2) endurance cycles at 85 degrees C. Material characterization by x-ray photoelectron spectroscopy suggested that the improved uniformity of the resistive switching in the N-2-annealed Ga2O3 films may result from a higher density of oxygen vacancies. These results indicate great potential for such devices in future high-density nonvolatile memory applications.
Effect of interfacial layer on device performance of metal oxide thin-film transistor with a multilayer high-k gate stack
(2018-08-30)
Ruan, Dun-Bao
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Liu, Po-Tsun
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Chiu, Yu-Chuan
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Kuo, Po-Yi
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Yu, Min-Chin
The amorphous indium gallium zinc oxide thin-film transistors (TFTs) with a multilayer high-k gate stack are investigated in this research. In order to achieve a high quality gate insulator for plastic flexible display application, the multilayer high-k gate stacks (SiO2/TiO2/HfO2) are deposited by a low-temperature physical vapor deposition (PVD) process. On the other hands, an interfacial layer between the high-k stack and metal oxide channel is important for the device performance. The effects of interfacial layer material (SiO2 or Ga2O3) are also discussed in this report. The devices with SiO2 interfacial layer show a high on/off current ratio of similar to 7x10(7) for its low gate leakage current, a small sub-threshold swing of 0.093 V/decade and a high field-effect mobility of similar to 37.8 cm(2)/Vs for its good interface condition and low interface defeats. This research shows that the interface engineering of multilayer PVD gate stacks is necessary for oxide TFT fabrication.
High Mobility Tungsten-Doped Thin-Film Transistor on Polyimide Substrate with Low Temperature Process
(2018-01-01)
Ruan, Dun-Bao
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Liu, Po-Tsun
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Chiu, Yu-Chuan
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Yu, Min-Chin
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Gan, Kai-jhih
A novel high mobility channel material, amorphous tungsten doped indium-oxide, is used as the active layer of flexible TFT, which is fabricated on a transparent polyimide under a low temperature process. The effects of channel thickness are investigated as well in this work. The flexible TFT with a suitable thickness of IWO film shows a high carrier mobility and low sub-threshold swing. The improvement can be attributed to increased donor-like oxygen vacancy with the thickness of channel layer increased.
High Performance Transparent a-IGZO Thin Film Transistors With ALD-HfO2 Gate Insulator on Colorless Polyimide Substrate
(2020-01-01)
Yu, Min-Chin
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Ruan, Dun-Bao
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Liu, Po-Tsun
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Chien, Ta-Chun
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Chiu, Yu-Chuan
High performance and transparent amorphous indium gallium zinc oxide thin-film transistors (a-IGZO TFT) have been successfully fabricated on the colorless polyimide plastic substrate using a high quality HfO2 dielectric film formed by the low temperature atomic layer deposition process as the gate insulator. Besides, the effects of source/drain material, ITO film and Mo metal, are also studied and compared in this work. With the optimized process condition, the devices with ITO source/drain exhibit a high I-ON/I-OFF current ratio of similar to 4.25 x 10(11), a lower sub-threshold swing value of 0.087 V/decade, a desirable positive threshold voltage value of 0.1379 V and an acceptable field effect mobility of 19.69 cm(2)/Vs. while it also shows excellent reliability characteristic and low hysteresis. These results may appear highly promising potentials for the next generation fully transparent flexible display application.
Impact of Post Deposition Annealing on Resistive Switching in Ga2O3-Based Conductive-Bridge RAM Devices
(2018-01-01)
Gan, Kai-jhih
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Liu, Po-Tsun
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Chien, Ta-Chun
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Ruan, Dun-Bao
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Chiu, Yu-Chuan
We study the influence of post-deposition annealing on the electrical properties of performance of Ga2O3-based Cu-ion-based conductive-bridge RAM (CBRAM) devices. Amorphous gallium oxide (Ga2O3) thin films were fabricated by RF sputtering at room temperature. The deposited films were annealed from the different temperatures and gas ambient. Their resistive switching characteristics are compared to determine the role of temperature and atmosphere in the annealing process on performance of these memory devices. The substantial improvement in device performance, such as stable switching, high switching cycles, and increased memory window, were obtained in the CBRAM devices during the post-Ga2O3 deposition annealing in pure nitrogen (N-2) ambient.
Investigation of low operation voltage InZnSnO thin-film transistors with different high-k gate dielectric by physical vapor deposition
(2018-08-30)
Ruan, Dun-Bao
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Liu, Po-Tsun
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Chiu, Yu-Chuan
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Kan, Kai-Zhi
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Yu, Min-Chin
Amorphous Indium-Zinc-Tin-Oxide thin-film transistors (a-IZTO TFT) using different types of high-k materials (like HfO2, ZrO2 and Al2O3) as gate dielectric are studied in this work. All gate dielectric films were deposited by physical vapor deposition (PVD) process for better composition control. Compared with the traditional SiO2 gate insulator, a high-k gate dielectric can reduce the operation voltage of TFT device significantly. The TFT device with ZrO2 gate insulator exhibits a small subthreshold swing of 0.126 V/decade, high field-effect mobility of similar to 40.7 cm(2)/Vs, low threshold voltage of -0.05 V, and large On/Off current ratio of similar to 1.01 x 10(7). The mechanisms for electrical improvements are also investigated. These results demonstrate the potential application of PVD-deposited ZrO2 thin film as a promising gate dielectric in oxide-based thin-film transistors.
Mobility enhancement for high stability tungsten-doped indium-zinc oxide thin film transistors with a channel passivation layer
(2018-01-01)
Ruan, Dun-Bao
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Liu, Po-Tsun
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Chiu, Yu-Chuan
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Kuo, Po-Yi
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Yu, Min-Chin
This study investigates the electrical characteristics and physical analysis for an amorphous tungsten-doped indium-zinc oxide thin film transistor with different backchannel passivation layers (BPLs), which were deposited by an ion bombardment-free process. A 10 times increase in mobility was observed and attributed to the generation of donor-like oxygen vacancies at the backchannel, which is induced by the oxygen desorption and Gibbs free energy of the BPL material. The mechanism was well studied by XPS analysis. On the other hand, a HfO2 gate insulator was applied for the InWZnO TFT device to control the extremely conductive channel and adjust the negative threshold voltage. With both a HfO2 gate insulator and a suitable BPL, the InWZnO TFT device exhibits good electrical characteristics and a remarkable lifetime when exposed to the ambient air.
Performance Enhancement for Tungsten-Doped Indium Oxide Thin Film Transistor by Hydrogen Peroxide as Cosolvent in Room-Temperature Supercritical Fluid Systems
(2019-06-26)
Ruan, Dun-Bao
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Liu, Po-Tsun
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Yu, Min-Chin
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Chien, Ta-Chun
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Chiu, Yu-Chuan
In this study, hydrogen peroxide (H2O2) cosolvent, which was dissolved into supercritical-phase carbon dioxide fluid (SCCO2), is employed to passivate excessive oxygen vacancies of the high-mobility tungsten-doped indium oxide without any essential thermal process. With the detailed material analysis, the internal physical mechanism of the cosolvent effect or the interaction between the cosolvent solution and supercritical-phase fluid is well discussed. In addition, the optimized result has been applied for the thin film transistor device fabrication. As a result, the device with SCCO2 + H2O2 treatment exhibits the lowest subthreshold swing of 82 mV/dec, the lowest interface trap density of 8.76 x 10(11) eV(-1) cm(-2), the lowest hysteresis of 47 mV, and an excellent reliability and uniformity characteristic compared with any other control groups. Besides, an extremely high field-effect mobility of 98.91 cm(2)/V s can also be observed, while there is even a desirable positive shift for the threshold voltage. Notably, compared with the untreated sample, the highest on/off current ratio of 5.11 x 10(7) can be achieved with at least four orders of magnitude enhancement by this unique treatment.
Performance improvements of tungsten and zinc doped indium oxide thin film transistor by fluorine based double plasma treatment with a high-K gate dielectric
(2018-11-01)
Ruan, Dun-Bao
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Liu, Po-Tsun
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Chiu, Yu-Chuan
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Yu, Min-Chin
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Gan, Kai-Jhih
The electrical characteristics and XPS analysis for the amorphous tungsten and zinc doped indium oxide thin film transistor, which was performed with single or double different fluorine based remote plasma treatment, were investigated in this study. A high mobility TFT device with the tungsten doped channel was fabricated in the previous study, but there was an inevitable negative shift for the threshold voltage, which will be a limit for the application of systemic circuit design. Therefore, a double fluorine based remote plasma treatment process is proposed for the high electronegativity of fluorine element and its similar radius as oxygen, which can be used to terminate the donor-like oxygen vacancy. It may induce a positive shift of threshold voltage, while carrier concentration and field effect mobility might be maintained. As a result, the sample with CF4/N-2+O-2 plasma treatment exhibits a higher on/off current ratio of similar to 4.73 x 10(6), a lower sub-threshold swing value of 0.070 V/decade, and a lower interfacial trap density value of 5.21 x 10(11) eV(-1) cm(-2) than other samples, while there is even a desirable positive shift of threshold voltage and acceptable field effect mobility of 31.2 cm(2)/Vs. This research proposes an effective approach to improve the reliability characteristic and adjust the inevitable negative shift of threshold voltage without sacrificing the carrier mobility of device.
Photoresponsivity Enhancement and Extension of the Detection Spectrum for Amorphous Oxide Semiconductor Based Sensors
(2019-03-01)
Ruan, Dun-Boo
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Liu, Po-Tsun
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Chen, Yi-Heng
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Chiu, Yu-Chuan
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Chien, To-Chun
In this study, indium gallium zinc oxide (InGaZnO [IGZO]) active layer capped with an ultrathin p-type stannous oxide (SnO) is demonstrated to be a thin film transistor (TFT) for color scanning and photosensing device applications. Typically, the sole IGZO-based TFT is blind to visible light and hard to be developed for visible light sensing. The combination of IGZO and SnO layers can extend the light detection spectrum into visible light wavelengths and ameliorate the photosensing characteristics. The optical responsivity and signal to noise ratio can even be enhanced from 1.05 x 10(-2) to 398.02 A W-1 and from 2.1 x 10(1) to 6.8 x 10(5) with at least four orders of magnitude, respectively. With the detailed material analysis and physical model discussed, it suggests that the large amount of additional light-excited carrier generated in the capping layer is the key factor for the significant improvement. Furthermore, the phenomenon of persistent photoconductivity can be effectively suppressed by its natural recombination under the heterojunction structure without applying charge-pumping method. The electrical uniformity of the sensor device is also highly potential for the next-generation displays integrating the photosensing functions.
Role of tungsten dopants in indium oxide thin-film transistor on radiation hardness technology
(2020-05-04)
Ruan, Dun-Bao
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Liu, Po-Tsun
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Gan, Kai-Jhih
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Chiu, Yu-Chuan
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Hsu, Chih-Chieh
The effects of radiation on tungsten doped indium oxide (IWO) thin-film transistors (TFTs) have been well investigated in this Letter. In order to achieve high stability and excellent electrical performance simultaneously even in high ionizing radiation damage ambient, different concentrations of tungsten dopant have been introduced for the TFT device fabrication. It is interesting that the high energy ionizing radiation may significantly increase the conductivity and influence the total concentration of oxygen vacancy in the transparent amorphous oxide semiconductor material, which may be completely different from the traditional radiation damage effect for silicon based CMOS devices. However, that abnormal phenomenon will be effectively suppressed by the powerful carrier suppressor, tungsten, which may have a high oxygen bond dissociation energy. Therefore, IWO devices with a 4% tungsten oxide dopant might be the optimized result even after high dosage ionizing radiation exposure. Hence, it may provide a promising radiation hardness approach to improve both the electrical characteristics and reliability for next generation displays, which can be used in the control system of nuclear power generation or space technology.
TAOS based Cu/TiW/IGZO/Ga2O3/Pt bilayer CBRAM for low-power display technology
(2018-11-25)
Gan, Kai-Jhih
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Liu, Po-Tsun
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Chiu, Yu-Chuan
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Ruan, Dun-Bao
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Chien, Ta-Chun
We demonstrate the characteristics of a conductive-bridging random access memory (CBRAM) with Cu/TiW/InGaZnO/Ga2O3/Pt stack structure. The addition of a thin metal-oxide layer (4.5 nm-thick Ga2O3) in the bottom of the CBRAM device significantly increases the off-state resistance (Rom') and the memory window. The IGZO bi-layer CBRAM shows the excellent memory performances, such as low operation current (down to 50 A), high on/off resistance ratio (> 10(3)), high switching endurance (up to 10(3) cycles) and the capability of multi-level tuning. Meanwhile, high thermal stability was also achieved. Three decades of resistance window is constantly maintained beyond 10(4)s at 85 degrees C. The resistive switching stability and electrical uniformity of bi-layer IGZO/Ga2O3 CBRAM device are obviously enhanced as compared with the one only with a single layer of IGZO film. These results have given a great potential for the transparent amorphous oxide semiconductor (TAOS)-based material utilizing in CBRAM stacks and integrating into the display circuits for future memory-in-pixel applications.
Temporal Stability of Smartphone Use Data: Determining Fundamental Time Unit and Independent Cycle
(2019-03-26)
Pan, Yuan-Chien
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Lin, Hsiao-Han
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Chiu, Yu-Chuan
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Lin, Sheng-Hsuan
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Lin, Yu-Hsuan
Background: Assessing human behaviors via smartphone for monitoring the pattern of daily behaviors has become a crucial issue in this century. Thus, a more accurate and structured methodology is needed for smartphone use research. Objective: The study aimed to investigate the duration of data collection needed to establish a reliable pattern of use, how long a smartphone use cycle could perpetuate by assessing maximum time intervals between 2 smartphone periods, and to validate smartphone use and use/nonuse reciprocity parameters. Methods: Using the Know Addiction database, we selected 33 participants and passively recorded their smartphone usage patterns for at least 8 weeks. We generated 4 parameters on the basis of smartphone use episodes, including total use frequency, total use duration, proactive use frequency, and proactive use duration. A total of 3 additional parameters (root mean square of successive differences, Control Index, and Similarity Index) were calculated to reflect impaired control and compulsive use. Results: Our findings included (1) proactive use duration correlated with subjective smartphone addiction scores, (2) a 2-week period of data collection is required to infer a 2-month period of smartphone use, and (3) smartphone use cycles with a time gap of 4 weeks between them are highly likely independent cycles. Conclusions: This study validated temporal stability for smartphone use patterns recorded by a mobile app. The results may provide researchers an opportunity to investigate human behaviors with more structured methods.
The influence on electrical characteristics of amorphous indium tungsten oxide thin film transistors with multi-stacked active layer structure
(2018-11-30)
Ruan, Dun-Bao
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Liu, Po-Tsun
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Gan, Kai-Jhih
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Chiu, Yu-Chuan
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Yu, Min-Chin
In order to effectively enhance the carrier mobility and device stability, simultaneously, a multi-stacked active layer of thin film transistor with a novel type of channel material, amorphous indium-tungsten-oxide, is proposed in this work. Atop-cappingoxygen-rich indium-tungsten-zinc-oxide thin film is used for suppressing the influence of the molecular adsorption or desorption from the ambient at the back channel in the gate bias stress test. In addition, a bottom-bufferingoxygen-rich indium-tungsten-zinc-oxide thin film is deposited to avoid the oxygen vacancy generation during the following thermal process. On the other hand, a 1-nm thick WO3 film is inserted between the high-k gate insulator and active layer, which play important roles as interfacial layer for improving the interface quality and keeping the stability of front channel film. Besides, an HfO2 dielectric film is chosen as gate insulator for realizing the low-voltage operation. As a result, the novel tungsten doped channel material with both-sideoxygen-rich active layer exhibits a high I-ON/I-OFF current ratio of similar to 6x10(7) for low gate leakage current, attributing to the Atop-cappingoxygen-rich thin film. Then, a high field-effect mobility of similar to 27.9cm(2)/V.s and a low sub-threshold swing of 0.079 V/decade are achieved by the good interface quality. This structure with both-sideoxygen-rich active layer exhibits its potential application for the future high-resolution and large-size display manufacture.