Browsing by Author "Meena, Jagan Singh"

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Control of active semiconducting layer packing in organic thin film transistors through synthetic tailoring of dielectric materials
(2014-01-01)
Singh, Ranjodh
;
Meena, Jagan Singh
;
Chang, Yu-Cheng
;
Wua, Chung-Shu
;
Ko, Fu-Hsiang
Apart from the development of new dielectric and semiconductor materials, the semiconductor-dielectric interface study is also very important for the optimum performance of organic thin film transistors (OTFTs). Herein, we have reported the detailed synthesis of a whole new family of dielectric materials which are 1,3,5,7-tetrabromoadamantane; 1,3,5,7-tetrachloroadamanatane; 1,3,5,7-tetraiodoadamantane and 1,3,5,7-tetrauraciladamantane (AdUr(4)). The unique ability of these molecules to undergo supramolecular thin film formation at low temperature, was analysed for their potential use as an insulator in organic electronic devices. Owing to the good leakage current density property shown by AdUr4 dielectric material it was further employed as a gate dielectric in regioregular poly(3-hexylthiophene), (P3HT) based OTFT. This OTFT device which was fabricated on a flexible PI plastic substrate has shown a good on/off current ratio (e.g., 2.18 x 10(4)) and high mobility (e.g., 0.15 cm(2) V-1 s(-1)). The semiconductor-dielectric interface study, has revealed that the AdUr(4) gate dielectric layer has guided the P3HT molecular chain domains to undergo edge-on orientation, which is the charge transport direction in OTFTs. In this process, the grazing incidence X-ray diffraction (GI-XRD) analysis and AFM study was also employed.
Control of active semiconducting layer packing in organic thin film transistors through synthetic tailoring of dielectric materials
(2014-01-01)
Singh, Ranjodh
;
Meena, Jagan Singh
;
Chang, Yu-Cheng
;
Wua, Chung-Shu
;
Ko, Fu-Hsiang
Apart from the development of new dielectric and semiconductor materials, the semiconductor-dielectric interface study is also very important for the optimum performance of organic thin film transistors (OTFTs). Herein, we have reported the detailed synthesis of a whole new family of dielectric materials which are 1,3,5,7-tetrabromoadamantane; 1,3,5,7-tetrachloroadamanatane; 1,3,5,7-tetraiodoadamantane and 1,3,5,7-tetrauraciladamantane (AdUr(4)). The unique ability of these molecules to undergo supramolecular thin film formation at low temperature, was analysed for their potential use as an insulator in organic electronic devices. Owing to the good leakage current density property shown by AdUr4 dielectric material it was further employed as a gate dielectric in regioregular poly(3-hexylthiophene), (P3HT) based OTFT. This OTFT device which was fabricated on a flexible PI plastic substrate has shown a good on/off current ratio (e.g., 2.18 x 10(4)) and high mobility (e.g., 0.15 cm(2) V-1 s(-1)). The semiconductor-dielectric interface study, has revealed that the AdUr(4) gate dielectric layer has guided the P3HT molecular chain domains to undergo edge-on orientation, which is the charge transport direction in OTFTs. In this process, the grazing incidence X-ray diffraction (GI-XRD) analysis and AFM study was also employed.
Controlled deposition of new organic ultrathin film as a gate dielectric layer for advanced flexible capacitor devices
(2013-06-01)
Meena, Jagan Singh
;
Chu, Min-Ching
;
Singh, Ranjodh
;
Shieh, Han-Ping D.
;
Liu, Po-Tsun
This letter describes a new organic (1-bromoadamantane) ultrathin film as gate dielectric, which was successfully deposited by sol-gel spin-coating process on a flexible polyimide substrate at room temperature. The metal-insulator-metal (MIM) device with organic (1-bromoadamantane) ultrathin (10 nm) film as gate dielectric layer operated at gate voltage of 5.0 V, showing a low leakage current density (5.63 x 10(-10) A cm(-2) at 5 V) and good capacitance (2.01 fF mu m(-2) at 1 MHz). The chemical structure of the 1-bromoadamantane layer was investigated by Fourier transform infrared spectrometer. The excellent leakage current density and better capacitance, probably due to the presence of polar, non-polar, low-polar groups, and bromine atoms in ultrathin film. Practical properties of the film in MIM capacitor such as dielectric constant as well as bending result of leakage current density and breakdown voltage have been better related to such fundamental adhesion nature over flexible substrate. This permits estimation of the properties of new dielectric in thin film form and short lists of the best materials for low loss and good capacitance flexible capacitors could be drawn up in future.
Effect of oxygen plasma on the surface states of ZnO films used to produce thin-film transistors on soft plastic sheets
(2013)
Meena, Jagan Singh
;
Chu, Min-Ching
;
Chang, Yu-Cheng
;
You, Hsin-Chiang
;
Singh, Ranjodh
Electronic displays and flexible electronics are poised to significantly impact emerging industries, including displays, energy products, sensors and medical devices, building a market that will significantly grow in the future. The implementation of transparent electronic devices requires the use of material components that could be formed using controlled deposition in the appropriate orientation onto a transparent flexible substrate. Here, we report a simple and efficient means of depositing onto a flexible polyimide (PI) substrate a highly ordered and highly aligned zinc oxide (ZnO) film for use as a carrier transporting and semiconducting layer with controlled surface charge density for thin-film transistor (TFT) applications. The deposition approach is based on the solution-coating of a zinc-acetate suspension under controlled conditions of the spread flow rate, droplet size of the drops, speed limit, and the oxygen (ca. O-2) plasma treatment of the coated film surface on the PI substrate. The plasma surface interactions on the surface states of the ZnO films for various times (ca. 1-5 min) were studied using X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. Moreover, the effects of O-2 plasma and the subsequent thermal annealing in an O-2 atmosphere at 250 degrees C on the properties of ZnO films were studied for its efficacy in TFT applications in terms of the charge carrier density and the change in the mobility. ZnO thin-film-based TFTs on PI exhibited a very high electron mobility of 22.8 cm(2) V-1 s(-1) at a drain bias of 5 V after treatment with O-2 plasma for 2 min. Furthermore, the plasma treatment for long durations of time caused a reduction in the charge carrier density from 1.58 x 10(19) cm(-3) for the 2 min treatment to 1.13 x 10(17) cm(-3) for the 5 min treatment, and the corresponding electron mobility was changed from 22.8 and 3.1 cm(2) V-1 s(-1) for the treatment times of 2 min and 5 min, respectively. The spin-coating technique used to deposit very thin ZnO films is currently used in microelectronics technology, which helps to ensure that the described ZnO thin-film deposition approach can be implemented in production lines with minimal changes in the fabrication design and in the auxiliary tools used in flexible electronics production.
Environmentally Stable Flexible Metal-Insulator-Metal Capacitors Using Zirconium-Silicate and Hafnium-Silicate Thin Film Composite Materials as Gate Dielectrics
(2011-08-01)
Meena, Jagan Singh
;
Chu, Min-Ching
;
Wu, Chung-Shu
;
Ravipati, Srikanth
;
Ko, Fu-Hsiang
Fully flexible metal-insulator-metal (MIM) capacitors fabricated on 25 mu m thin polyimide (PI) substrates via the surface sol gel process using 10-nm-thick zirconium-silicate (ZrSi(x)O(y)) and hafnium-silicate (HfSi(m)O(n)) films as gate dielectrics. The surface morphology of the ZrSi(x)O(y) and HfSi(m)O(n) films were investigated using atomic force microscopy and scanning electron microscopy, which confirmed that continuous and crack-free surface growth had occurred on the PI. Both the films treated with oxygen (O(2)) plasma and annealing (ca. 250 degrees C) consisted of amorphous phase; confirmed by X-ray diffraction. We employed X-ray photoelectron spectroscopy (XPS) at high resolution to examine the chemical composition of the films subjected to various treatment conditions. The shift of the XPS peaks towards higher binding energy revealed the O(2) plasma-pretreatment followed by annealing was the most effective process to the surface oxidation at relatively low-temperature, for further passivate the grease traps and making dielectric films thermally stable. The ZrSi(x)O(y) and HfSi(m)O(n) films in sandwich-like MIM configuration on the PI substrates exhibited the low leakage current densities of 7.1 x 10(-9) and 8.4 x 10(-9) A/cm(2) at applied electric field of 10 MV/cm and maximum capacitance densities of 7.5 and 5.3 fF/mu m(2) at 1 MHz, respectively. In addition, the ZrSi(x)O(y) and HfSi(m)O(n), films in MIM capacitors showed the estimated dielectric constants of 8.2 and 6.0, respectively. Prior to use of flexible MIM capacitors in advanced flexible electronic devices; the reliability test was studied by applying day-dependent leakage current density measurements up to 30 days. These films of silicate-surfactant mesostructured materials have special interest to be used as gate dielectrics in future for flexible metal-oxide-semiconductor devices.
Facile Electroless Deposition of Zinc Oxide Ultrathin Film for Zinc Acetate Solution-processed Transistors
(2012-07-01)
Chu, Min-Ching
;
You, Hsin-Chiang
;
Meena, Jagan Singh
;
Shieh, Shao-Hui
;
Shao, Chyi-Yau
"A low-cost, ultra-thin, transparency and high-quality zinc oxide (ZnO) film was successfully demonstrated as the carrier transporting and semiconducting layer for thin-film transistor (TFT) devices. The ZnO ultra-thin film with 3.7 nm in thickness was spin-coated from zinc acetate sol-gel solution under electroless condition. The film structure was characterized by atomic force microscopy and x-ray diffraction spectroscopy, respectively. Among various processing temperatures, the electrical property of the fabricated TFT verified the devices could be successfully achieved from suitable annealing temperature of 300 to 700 degrees C. However, the higher treatment temperature of 800 to 900 degrees C deteriorated the transistor property due to the loss of oxygen vacancy. The electrical properties of these ZnO-based n-type TFTswere obtained as follows: the mobility (mu(sat))ranged from 0.47 to 1.78 cm(2) V-1 s(-1), the on/off current ratio ranged from 5.7 x 10(5) to 1.6 x 10(6), and the threshold voltage ranged from 9.7 to 17.3 V. The long-term (100 days) characterization for the evaluation of the ultra-thin ZnO TFT reliability on the mobility and on/off current ratio strongly suggested the effectiveness of solution-processed ultra-thin film transistors. This proposed efficient sol-gel solution method to fabricate transparent ZnO ultra-thin film was relatively simple and cost-effective technique, and could be used as a new candidate of material for next-generation electronic devices to meet the growing demand of small feature bioelectronic sensor, light emitting diode and flexible panel."
Facile synthetic route to implement a fully bendable organic metal-insulator-semiconductor device on polyimide sheet
(2012-05-01)
Meena, Jagan Singh
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Chu, Min-Ching
;
Wu, Chung-Shu
;
Liang, Jie-Chian
;
Chang, Yu-Cheng
Triblock copolymer surfactant, HO(CH2CH2O)(20)(CH2CH(CH3)O)(70)(CH2CH2O)(20)H (i.e. P123)-based nanocrystalline (nc)-TiO2 thin film had been synthesized on organic flexible polyimide (PI) sheet for their application in organic metal-insulator-semiconductor (MIS) device. The nc-TiO2 film over PI was successfully deposited for the first time by a systematic solution proceeds dip-coating method and by the assistance of triblock copolymer surfactant. The effect of annealing temperature (270 degrees C, 5 h) on the texture, morphology and time-induced hydrophilicity was studied by X-ray diffraction (XRD), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and contact angle system, respectively, to examine the chemical composition of the film and the contact angle. The surface morphology of the semiconducting layer of organic pentacene was also investigated by using AFM and XRD, and confirmed that continuous crystalline film growth had occurred on the nc-TiO2 surface over flexible PI sheet. The semiconductor-dielectric interface of pentacene and nc-TiO2 films was characterized by current-voltage and capacitance-voltage measurements. This interface measurement in cross-link MIS structured device yielded a low leakage current density of 8.7 x 10(-12) A cm(-2) at 0 to -5V, maximum capacitance of 102.3 pF at 1 MHz and estimated dielectric constant value of 28.8. Furthermore, assessment of quality study of nc-TiO2 film in real-life flexibility tests for different types of bending settings with high durability (c. a. 30 days) demonstrated a better comprehension of dielectric properties over flexible PI sheet. We expected them to have a keen interest in the scientific study, which could be an alternate opportunity to the excellent dielectric-semiconductor interface at economic and low temperature processing for large-area flexible field-effect transistors and sensors. (C) 2012 Elsevier B. V. All rights reserved.
Flexible metal-insulator-metal capacitor using plasma enhanced binary hafnium-zirconium-oxide as gate dielectric layer
(2010-05-01)
Meena, Jagan Singh
;
Chu, Min-Ching
;
Tiwari, Jitendra N.
;
You, Hsin-Chiang
;
Wu, Chung-Hsin
We have used a sol-gel spin-coating process to fabricate a new metal-insulator-metal capacitor comprising 10-nm thick binary hafnium-zirconium-oxide (Hf(x)Zr(1-x)O(2)) film on a flexible polyimide (PI) substrate. The surface morphology of this Hf(x)Zr(1-x)O(2) film was investigated using atomic force microscopy and scanning electron microscopy, which confirmed that continuous and crack-free film growth had occurred on the PI. After oxygen plasma pre-treatment and subsequent annealing at 250 degrees C, the film on the PI substrate exhibited a low leakage current density of 3.22 x 10(-8) A/cm(2) at -10 V and maximum capacitance densities of 10.36 fF/mu m(2) at 10 kHz and 9.42 fF/mu m(2) at 1 MHz. The as-deposited sol-gel film was oxidized when employing oxygen plasma at a relatively low temperature (similar to 250 degrees C), thereby enhancing the electrical performance. (C) 2010 Elsevier Ltd. All rights reserved.
Flexible MIM Capacitors Using Zirconium-Silicate and Hafnium-Silicate as Gate-Dielectric Films
(2010)
Meena, Jagan Singh
;
Chu, Min-Ching
;
Ko, Fu-Hsiang
;
材料科學與工程學系奈米科技碩博班
;
Graduate Program of Nanotechnology , Department of Materials Science and Engineering
To the first time, we have fabricated metal-insulator-metal (MIM) capacitors using 10-nm-thick zirconium-silicate (ZrSi(x)O(y)) and hafnium-silicate (HfSi(m)O(n)) thin dielectric films on the flexible polyimide substrate by sol-gel process. The sol-gel films were oxidized by employing oxygen plasma to enhance the electrical performance at low temperature (similar to 250 degrees C). The oxygen plasma may accept as most effective process at low temperature to surface oxidation of a dielectric film for flexible organic device. The results showed the satisfactory electrical characteristics for the corresponding films with low leakage current densities similar to 10(-9) Acm(-2) at 5V and maximum- capacitance densities 12.10 (ZrSi(x)O(y)) and 14.32 fF/mu m(2) (HfSi(m)O(n)), at 1MHz. These entire make the combinatorial thin oxide films based MIM capacitors to he very suitable for future flexible devices.
Highly reliable Si(3)N(4)-HfO(2) stacked heterostructure to fully flexible poly-(3-hexylthiophene) thin-film transistor
(2011-08-01)
Meena, Jagan Singh
;
Chu, Min-Ching
;
Wu, Chung-Shu
;
Chang, Feng-Chih
;
Ko, Fu-Hsiang
A new and fully flexible Si(3)N(4)-HfO(2) stacked poly-(3-hexylthiophene) p-type thin film transistor (P3HT-TFT) was successfully fabricated on thin semi-transparent polyimide (PI) substrate. The success of the TFT manufacturing adopts: (a) very simple and cost-effective sol-gel spin-coating technique to obtain 10-nm high-k HfO(2) as dielectric layer over fully flexible PI substrate; (b) 50-nm silicon nitride (Si(3)N(4)) as the most efficient passivation layer on top of HfO(2) film; (c) bendable 30-nm P3HT channel film by spin-coating method. Current-electric field characteristics of HfO(2) layer in metal-insulator-metal (MIM) and TFT configurations, with or without Si(3)N(4) passivation layer, were carefully evaluated. The origin of unsatisfactory leakage current in MIM and TFT structures could be effectively suppressed by means of Si(3)N(4) film as the efficient passivation layer. The bottom-gate TFT demonstrated the on-to-off ratio 2 x 10(4) for drain current, -1.9 V threshold voltage and good saturation mobility (0.041 cm(2) V (1) s (1)). The proposed devices were examined in convex and concave types of various radii of curvature (R(C)) in order to explore the manufacturing feasibility and electrical reliability of the fully flexible TFT for practical applications. In addition, various folding times and environmental stability on aforementioned devices with respective to electrical performances were also evaluated. (C) 2011 Elsevier B.V. All rights reserved.
Highly reliable Si3N4-HfO2 stacked heterostructure to fully flexible poly-(3-hexylthiophene) thin-film transistor
(2011-08-01)
Meena, Jagan Singh
;
Chu, Min-Ching
;
Wu, Chung-Shu
;
Chang, Feng-Chih
;
Ko, Fu-Hsiang
A new and fully flexible Si3N4-HfO2 stacked poly-(3-hexylthiophene) p-type thin film transistor (P3HT-TFT) was successfully fabricated on thin semi-transparent polyimide (PI) substrate. The success of the TFT manufacturing adopts: (a) very simple and cost-effective sol-gel spin-coating technique to obtain 10-nm high-k HfO2 as dielectric layer over fully flexible PI substrate; (b) 50-nm silicon nitride (Si3N4) as the most efficient passivation layer on top of HfO2 film; (c) bendable 30-nm P3HT channel film by spin-coating method. Current-electric field characteristics of HfO2 layer in metal-insulator-metal (MIM) and TFT configurations, with or without Si3N4 passivation layer, were carefully evaluated. The origin of unsatisfactory leakage current in MIM and TFT structures could be effectively suppressed by means of Si3N4 film as the efficient passivation layer. The bottom-gate TFT demonstrated the on-to-off ratio 2 x 10(4) for drain current, -1.9 V threshold voltage and good saturation mobility (0.041 cm(2) V (1) s (1)). The proposed devices were examined in convex and concave types of various radii of curvature (R-C) in order to explore the manufacturing feasibility and electrical reliability of the fully flexible TFT for practical applications. In addition, various folding times and environmental stability on aforementioned devices with respective to electrical performances were also evaluated. (C) 2011 Elsevier B.V. All rights reserved.
Knitting up 2,7-disubstituted carbazole based oligomers through supramolecular interactions for their application in organic thin film transistors
(2015-01-01)
Singh, Ranjodh
;
Meena, Jagan Singh
;
Wu, Chung-Shu
;
Ko, Fu-Hsiang
;
材料科學與工程學系
For the design and development of organic electronic devices, the main focus is particularly on the synthesis of new organic semiconductors and dielectric materials. Molecular engineering is another effective strategy, in this direction which has been explored successfully in this study through synthesis of a p-conjugated oligomer CbzTPAU2, with M-w = 2169. This bow shaped oligomer has its core unit made of 2,7-disubstituted carbazole which further has been connected to its end-terminal unit TPAU2 by 1,4-bis(decyloxy)-2,5-diethynylbenzene. The presence of a uracil moiety on end terminals of CbzTPAU2 has triggered the self-assembly of CbzTPAU2 molecules through knitting up of each of these single units through four Uracil-Uracil intermolecular hydrogen bonds (U center dot center dot center dot U) per CbzTPAU2 unit. An Atomic Force Microscope (AFM) study was employed to explore the directionality of hydrogen bonding. Further, the effect of solvent polarity on the stability of U center dot center dot center dot U bonding in CbzTPAU2 oligomers has also been reported here in this study. The potential of these self-assembled CbzTPAU2 oligomers when explored as charge transporting layers in OTFTs has shown p-type behaviour. The OTFT device bottom-gate, top-contact when fabricated on the heavily doped n-type Si wafer with SiO2 as a gate dielectric (200 nm) has shown a good on/off ratio 3.43 x 10(3) and with an average hole mobility of 0.167 cm(2) V-1 s(-1).
Novel Chemical Route to Prepare a New Polymer Blend Gate Dielectric for Flexible Low-Voltage Organic Thin-Film Transistor
(2012-06-01)
Meena, Jagan Singh
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Chu, Min-Ching
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Chang, Yu-Cheng
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Wu, Chung-Shu
;
Cheng, Chih-Chia
An organic-organic blend thin film has been synthesized through the solution deposition of a triblock copolymer (Pluronic P123, EO20-PO70-EO20) and polystyrene (PS), which is called P123-PS for the blend film whose precursor solution was obtained with organic additives. In addition to having excellent insulating properties, these materials have satisfied other stringent requirements for an optimal flexible device: low-temperature fabrication, nontoxic, surface free of pinhole defect, compatibility with organic semiconductors, and mechanical flexibility. Atomic force microscope measurements revealed that the optimized P123-PS blend film was uniform, crack-free, and highly resistant to moisture absorption on polyimide (PI) substrate. The film was well-adhered to the flexible Au/Cr/PI substrate for device application as a stable insulator, which was likely due to the strong molecular assembly that includes both hydrophilic and hydrophobic effects from the high molecular weights. The contact angle measurements for the P123-PS surface indicated that the system had a good hydrophobic surface with a total surface free energy of approximately 19.6 mJ m(-2). The dielectric properties of P123-PS were characterized in a cross-linked meta-insulator-metal structured device on the PI substrate by leakage current, capacitance, and dielectric constant measurements. The P123-PS film showed an average low leakage current density value of approximately 10(-10) A cm(-2) at 5-10 MV cm(-1) and large capacitance of 88.2 nF cm(-2) at 1 MHz, and the calculated dielectric constant was 2.7. In addition, we demonstrated an organic thin-film transistor (OTFT) device on a flexible PI substrate using the P123-PS as the gate dielectric layer and pentacene as the channel layer. The OTFT showed good saturation mobility (0.16 cm(2) V-1 s(-1)) and an on-to-off current ratio of 5 x 10(5). The OTFT should operate under bending conditions; therefore flexibility tests for two types of bending modes (tensile and compressive) were also performed successfully.
Overview of emerging nonvolatile memory technologies
(2014-09-25)
Meena, Jagan Singh
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Sze, Simon Min
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Chand, Umesh
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Tseng, Tseung-Yuen
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電子工程學系及電子研究所
Nonvolatile memory technologies in Si-based electronics date back to the 1990s. Ferroelectric field-effect transistor (FeFET) was one of the most promising devices replacing the conventional Flash memory facing physical scaling limitations at those times. A variant of charge storage memory referred to as Flash memory is widely used in consumer electronic products such as cell phones and music players while NAND Flash-based solid-state disks (SSDs) are increasingly displacing hard disk drives as the primary storage device in laptops, desktops, and even data centers. The integration limit of Flash memories is approaching, and many new types of memory to replace conventional Flash memories have been proposed. Emerging memory technologies promise new memories to store more data at less cost than the expensive-to-build silicon chips used by popular consumer gadgets including digital cameras, cell phones and portable music players. They are being investigated and lead to the future as potential alternatives to existing memories in future computing systems. Emerging nonvolatile memory technologies such as magnetic random-access memory (MRAM), spin-transfer torque random-access memory (STT-RAM), ferroelectric random-access memory (FeRAM), phase-change memory (PCM), and resistive random-access memory (RRAM) combine the speed of static random-access memory (SRAM), the density of dynamic random-access memory (DRAM), and the nonvolatility of Flash memory and so become very attractive as another possibility for future memory hierarchies. Many other new classes of emerging memory technologies such as transparent and plastic, three-dimensional (3-D), and quantum dot memory technologies have also gained tremendous popularity in recent years. Subsequently, not an exaggeration to say that computer memory could soon earn the ultimate commercial validation for commercial scale-up and production the cheap plastic knockoff. Therefore, this review is devoted to the rapidly developing new class of memory technologies and scaling of scientific procedures based on an investigation of recent progress in advanced Flash memory devices.
Oxygen Plasma Functioning of Charge Carrier Density in Zinc Oxide Thin-Film Transistors
(2013-07-01)
Chu, Min-Ching
;
Meena, Jagan Singh
;
Liu, Po-Tsun
;
Shieh, Han-Ping D.
;
You, Hsin-Chiang
A change in the charge carrier density of zinc oxide (ZnO) films for control the functioning of thin-film transistors (TFTs) has been studied by oxygen (O-2) plasma techniques. This effect was interpreted in terms of a threshold voltage shift and the variation in carrier mobility. The plasma-surface interaction on the molecular level and the behavioral characterization of ZnO films were investigated by X-ray photospectroscopy of the O 1s region. This process was highly sensitive at low level variations in defect and doping density. O-2 plasma treatment leads to a shift of turn-on voltage and a reduction of the off-current by more than two orders of magnitude in ZnO-TFTs. (C) 2013 The Japan Society of Applied Physics
Plasma-enhanced flexible metal-insulator-metal capacitor using high-k ZrO(2) film as gate dielectric with improved reliability
(2010-08-01)
Chu, Min-Ching
;
Meena, Jagan Singh
;
Cheng, Chih-Chia
;
You, Hsin-Chiang
;
Chang, Feng-Chih
We demonstrate a new flexible metal-insulator-metal capacitor using 9.5-nm-thick ZrO(2) film on a plastic polyimide substrate based on a simple and low-cost sal-gel precursor spin-coating process. The surface morphology of the ZrO(2) film was investigated using scan electron microscope and atomic force microscope. The as-deposited ZrO(2) film under suitable treatment of oxygen (O(2)) plasma and then subsequent annealing at 250 degrees C exhibits superior low leakage current density of 9.0 x 10(-9) A/cm(2) at applied voltage of 5 V and maximum capacitance density of 13.3 fF/mu m(2) at 1 MHz. The as-deposited sol-gel film was completely oxidized when we employed O(2) plasma at relatively low temperature and power (30 W), hence enhancing the electrical performance of the capacitor. The shift (Zr 3d from 184.1 eV to 184.64 eV) in X-ray photoelectron spectroscopy of the binding energy of the electrons towards higher binding energy; clearly indicates that the O(2) plasma reaction was most effective process for the complete oxidation of the sol-gel precursor at relatively low processing temperature. (C) 2010 Elsevier Ltd. All rights reserved.
Plasma-enhanced flexible metal-insulator-metal capacitor using high-k ZrO2 film as gate dielectric with improved reliability
(2010-08-01)
Chu, Min-Ching
;
Meena, Jagan Singh
;
Cheng, Chih-Chia
;
You, Hsin-Chiang
;
Chang, Feng-Chih
We demonstrate a new flexible metal-insulator-metal capacitor using 9.5-nm-thick ZrO2 film on a plastic polyimide substrate based on a simple and low-cost sal-gel precursor spin-coating process. The surface morphology of the ZrO2 film was investigated using scan electron microscope and atomic force microscope. The as-deposited ZrO2 film under suitable treatment of oxygen (O-2) plasma and then subsequent annealing at 250 degrees C exhibits superior low leakage current density of 9.0 x 10(-9) A/cm(2) at applied voltage of 5 V and maximum capacitance density of 13.3 fF/mu m(2) at 1 MHz. The as-deposited sol-gel film was completely oxidized when we employed O-2 plasma at relatively low temperature and power (30 W), hence enhancing the electrical performance of the capacitor. The shift (Zr 3d from 184.1 eV to 184.64 eV) in X-ray photoelectron spectroscopy of the binding energy of the electrons towards higher binding energy; clearly indicates that the O-2 plasma reaction was most effective process for the complete oxidation of the sol-gel precursor at relatively low processing temperature. (C) 2010 Elsevier Ltd. All rights reserved.
Polystyrene-block-poly(methylmethacrylate) composite material film as a gate dielectric for plastic thin-film transistor applications
(2014)
Meena, Jagan Singh
;
Chu, Min-Ching
;
Singh, Ranjodh
;
Wu, Chung-Shu
;
Chand, Umesh
We report a simple approach to fabricate an organic-inorganic hybrid gate insulator based n-type thin-film transistor (TFT) on a plastic polyimide (PI) sheet at room temperature using an appropriate composition of commercially available polymers and block copolymer surfactant. The composite material film namely; polystyrene-block-poly(methylmethacrylate) (PS-b-PMMA) is readily deposited as a gate dielectric with zinc oxide (ZnO) as a semiconductor layer. This new dielectric material film exhibits high surface energy, high air stability, very low leakage current density and better dielectric constant as compared to the conventional polymer dielectrics. This plastic ZnO-TFT combines the advantages of a high-mobility transparent inorganic semiconductor with an ultrathin high-capacitance and low-leakage PS-b-PMMA composite gate dielectric. Fourier transform infrared (FT-IR) spectrum analysis is used for the PS-b-PMMA film to confirm the presence of functional components in this composite material film. The contact angle measurements for three test liquids (e.g., distilled water, ethylene glycol and diiodomethane) reveal that the composite dielectric materials film is nearly hydrophobic and the calculated surface energy is 35.05 mJ m(-2). The resulting TFT exhibits excellent operating characteristics at V-DS=10 V with a drain-source current on/off modulation ratio (I-on/I-off) of 3.12 x 10(6) and a carrier mobility of 2.48 cm(2) V-1 s(-1). Moreover in the bending mode and in a normal environment, the device remained undistorted and shows better reliability and performance, while the thickness of PS-b-PMMA is about 28 nm. The results have suggested a new and easy approach for achieving transparent and functionally bendable optoelectronics devices.
Solution processable bilayered gate dielectric towards flexible organic thin film transistors
(2015-04-01)
Singh, Ranjodh
;
Meena, Jagan Singh
;
Tsai, I-Hsin
;
Lin, Yen-Ting
;
Wang, Cheng-Jyun
In this study, we have successfully explored the potential of a new bilayer gate dielectric material, composed of Polystyrene (PS), Pluronic P123 Block Copolymer Surfactant (P123) composite thin film and Polyacrylonitrile (PAN) through fabrication of metal insulator metal (MIM) capacitor devices and organic thin film transistors (OTFTs). The conditions for fabrication of PAN and PS-P123 as a bilayer dielectric material are optimized before employing it further as a gate dielectric in OTFTs. Simple solution processable techniques are applied to deposit PAN and PS-P123 as a bilayer dielectric layer on Polyimide (PI) substrates. Contact angle study is further performed to explore the surface property of this bilayer polymer gate dielectric material. This new bilayer dielectric having a k value of 3.7 intermediate to that of PS-P123 composite thin film dielectric (k similar to 2.8) and PAN dielectric (k similar to 5.5) has successfully acted as a buffer layer by preventing the direct contact between the organic semiconducting layer and high k PAN dielectric. The OTFT devices based on alpha,omega-dihexylquaterthiophene (DH4T) incorporated with this bilayer dielectric, has demonstrated a hole mobility of 1.37 x 10(-2) and on/off current ratio of 10(3) which is one of the good values as reported before. Several bending conditions are applied, to explore the charge carrier hopping mechanism involved in deterioration of electrical properties of these OTFTs. Additionally, the electrical performance of OTFTs, which are exposed to open atmosphere for five days, can be interestingly recovered by means of re-baking them respectively at 90 degrees C. (C) 2015 Elsevier B.V. All rights reserved.
Thin-Film Composite Materials as a Dielectric Layer for Flexible Metal-Insulator-Metal Capacitors
(2010)
Tiwari, Jitendra N.
;
Meena, Jagan Singh
;
Wu, Chung-Shu
;
Tiwari, Rajanish N.
;
Chu, Min-Ching
A new organic-organic nanoscale composite thin-film (NCTF) dielectric has been synthesized by solution deposition of 1-bromoadamantane and triblock copolymer (Pluronic P123, BASF, EO(20)-PO(70)-EO(20)), in which the precursor solution has been achieved with organic additives. We have used a sol-gel process to make a metal-insulator-metal capacitor (MIM) comprising a nanoscale (10 nm-thick) thin-film on a flexible polyimide (PI) substrate at room temperature. Scanning electron microscope and atomic force microscope revealed that the deposited NCTFs were crack-free, uniform, highly resistant to moisture absorption, and well adhered on the Au-Cr/PI. The electrical properties of 1-bromoadamantane-P123 NCTF were characterized by dielectric constant, capacitance, and leakage current measurements. The 1-bromoadamantane-P123 NCTF on the PI substrate showed a low leakage current density of 5.5 x 10(-11) A cm(-2) and good capacitance of 2.4 fF at 1 MHz. In addition, the calculated dielectric constant of 1-bromoadamantane-P123 NCTF was 1.9, making them suitable candidates for use in future flexible electronic devices as a stable intermetal dielectric. The electrical insulating properties of 1-bromoadamantane-P123 NCTF have been improved due to the optimized dipole moments of the van der Waals interactions.