Science.gov

Sample records for oxide thin-film transistors

  1. Review of solution-processed oxide thin-film transistors

    NASA Astrophysics Data System (ADS)

    Kim, Si Joon; Yoon, Seokhyun; Kim, Hyun Jae

    2014-02-01

    In this review, we summarize solution-processed oxide thin-film transistors (TFTs) researches based on our fulfillments. We describe the fundamental studies of precursor composition effects at the beginning in order to figure out the role of each component in oxide semiconductors, and then present low temperature process for the adoption of flexible devices. Moreover, channel engineering for high performance and reliability of solution-processed oxide TFTs and various coating methods: spin-coating, inkjet printing, and gravure printing are also presented. The last topic of this review is an overview of multi-functional solution-processed oxide TFTs for various applications such as photodetector, biosensor, and memory.

  2. Investigation of tungsten doped tin oxide thin film transistors

    NASA Astrophysics Data System (ADS)

    Yang, Jianwen; Meng, Ting; Yang, Zhao; Cui, Can; Zhang, Qun

    2015-11-01

    Tungsten doped tin oxide thin film transistors (TWO-TFTs) were fabricated by radio frequency magnetron sputtering. With TWO thin films as the channel layers, the TFTs show lower off-current and positive shift turn-on voltage than the intrinsic tin oxide TFTs, which can be explained by the reason that W doping is conducive to suppress the carrier concentration of the TWO channel layer. It is important to elect an appropriate channel thickness for improving the TFT performance. The optimum TFT performance in enhancement mode is achieved at W doping content of 2.7 at% and channel thickness of 12 nm, with the saturation mobility, turn-on voltage, subthreshold swing value and on-off current ratio of 5 cm2 V-1 s-1, 0.4 V, 0.4 V/decade and 2.4  ×  106, respectively.

  3. Combinatorial study of zinc tin oxide thin-film transistors

    SciTech Connect

    McDowell, M. G.; Sanderson, R. J.; Hill, I. G.

    2008-01-07

    Groups of thin-film transistors using a zinc tin oxide semiconductor layer have been fabricated via a combinatorial rf sputtering technique. The ZnO:SnO{sub 2} ratio of the film varies as a function of position on the sample, from pure ZnO to SnO{sub 2}, allowing for a study of zinc tin oxide transistor performance as a function of channel stoichiometry. The devices were found to have mobilities ranging from 2 to 12 cm{sup 2}/V s, with two peaks in mobility in devices at ZnO fractions of 0.80{+-}0.03 and 0.25{+-}0.05, and on/off ratios as high as 10{sup 7}. Transistors composed predominantly of SnO{sub 2} were found to exhibit light sensitivity which affected both the on/off ratios and threshold voltages of these devices.

  4. Solution-Processed Indium Oxide Based Thin-Film Transistors

    NASA Astrophysics Data System (ADS)

    Xu, Wangying

    Oxide thin-film transistors (TFTs) have attracted considerable attention over the past decade due to their high carrier mobility and excellent uniformity. However, most of these oxide TFTs are usually fabricated using costly vacuum-based techniques. Recently, the solution processes have been developed due to the possibility of low-cost and large-area fabrication. In this thesis, we have carried out a detailed and systematic study of solution-processed oxide thin films and TFTs. At first, we demonstrated a passivation method to overcome the water susceptibility of solution-processed InZnO TFTs by utilizing octadecylphosphonic acid (ODPA) self-assembled monolayers (SAMs). The unpassivated InZnO TFTs exhibited large hysteresis in their electrical characteristics due to the adsorbed water at the semiconductor surface. Formation of a SAM of ODPA on the top of InZnO removed water molecules weakly absorbed at the back channel and prevented water diffusion from the surroundings. Therefore the passivated devices exhibited significantly reduced hysteretic characteristics. Secondly, we developed a simple spin-coating approach for high- k dielectrics (Al2O3, ZrO2, Y 2O3 and TiO2). These materials were used as gate dielectrics for solution-processed In2O3 or InZnO TFTs. Among the high-k dielectrics, the Al2O3-based devices showed the best performance, which is attributed to the smooth dielectric/semiconductor interface and the low interface trap density besides its good insulating property. Thirdly, the formation and properties of Al2O3 thin films under various annealing temperatures were intensively studied, revealing that the sol-gel-derived Al2O3 thin film undergoes the decomposition of organic residuals and nitrate groups, as well as conversion of aluminum hydroxides to form aluminum oxide. Besides, the Al2O 3 film was used as gate dielectric for solution-processed oxide TFTs, resulting in high mobility and low operating voltage. Finally, we proposed a green route for

  5. Room Temperature Oxide Deposition Approach to Fully Transparent, All-Oxide Thin-Film Transistors.

    PubMed

    Rembert, Thomas; Battaglia, Corsin; Anders, André; Javey, Ali

    2015-10-28

    A room temperature cathodic arc deposition technique is used to produce high-mobility ZnO thin films for low voltage thin-film transistors (TFTs) and digital logic inverters. All-oxide, fully transparent devices are fabricated on alkali-free glass and flexible polyimide foil, exhibiting high performance. This provides a practical materials platform for the low-temperature fabrication of all-oxide TFTs on virtually any substrate. PMID:26455916

  6. Novel Low Temperature Processing for Enhanced Properties of Ion Implanted Thin Films and Amorphous Mixed Oxide Thin Film Transistors

    NASA Astrophysics Data System (ADS)

    Vemuri, Rajitha

    This research emphasizes the use of low energy and low temperature post processing to improve the performance and lifetime of thin films and thin film transistors, by applying the fundamentals of interaction of materials with conductive heating and electromagnetic radiation. Single frequency microwave anneal is used to rapidly recrystallize the damage induced during ion implantation in Si substrates. Volumetric heating of the sample in the presence of the microwave field facilitates quick absorption of radiation to promote recrystallization at the amorphous-crystalline interface, apart from electrical activation of the dopants due to relocation to the substitutional sites. Structural and electrical characterization confirm recrystallization of heavily implanted Si within 40 seconds anneal time with minimum dopant diffusion compared to rapid thermal annealed samples. The use of microwave anneal to improve performance of multilayer thin film devices, e.g. thin film transistors (TFTs) requires extensive study of interaction of individual layers with electromagnetic radiation. This issue has been addressed by developing detail understanding of thin films and interfaces in TFTs by studying reliability and failure mechanisms upon extensive stress test. Electrical and ambient stresses such as illumination, thermal, and mechanical stresses are inflicted on the mixed oxide based thin film transistors, which are explored due to high mobilities of the mixed oxide (indium zinc oxide, indium gallium zinc oxide) channel layer material. Semiconductor parameter analyzer is employed to extract transfer characteristics, useful to derive mobility, subthreshold, and threshold voltage parameters of the transistors. Low temperature post processing anneals compatible with polymer substrates are performed in several ambients (oxygen, forming gas and vacuum) at 150 °C as a preliminary step. The analysis of the results pre and post low temperature anneals using device physics fundamentals

  7. Flexible Electronics Powered by Mixed Metal Oxide Thin Film Transistors

    NASA Astrophysics Data System (ADS)

    Marrs, Michael

    A low temperature amorphous oxide thin film transistor (TFT) and amorphous silicon PIN diode backplane technology for large area flexible digital x-ray detectors has been developed to create 7.9-in. diagonal backplanes. The critical steps in the evolution of the backplane process include the qualification and optimization of the low temperature (200 °C) metal oxide TFT and a-Si PIN photodiode process, the stability of the devices under forward and reverse bias stress, the transfer of the process to flexible plastic substrates, and the fabrication and assembly of the flexible detectors. Mixed oxide semiconductor TFTs on flexible plastic substrates suffer from performance and stability issues related to the maximum processing temperature limitation of the polymer. A novel device architecture based upon a dual active layer improves both the performance and stability. Devices are directly fabricated below 200 ºC on a polyethylene naphthalate (PEN) substrate using mixed metal oxides of either zinc indium oxide (ZIO) or indium gallium zinc oxide (IGZO) as the active semiconductor. The dual active layer architecture allows for adjustment to the saturation mobility and threshold voltage stability without the requirement of high temperature annealing, which is not compatible with flexible plastic substrates like PEN. The device performance and stability is strongly dependent upon the composition of the mixed metal oxide; this dependency provides a simple route to improving the threshold voltage stability and drive performance. By switching from a single to a dual active layer, the saturation mobility increases from 1.2 cm2/V-s to 18.0 cm2/V-s, while the rate of the threshold voltage shift decreases by an order of magnitude. This approach could assist in enabling the production of devices on flexible substrates using amorphous oxide semiconductors. Low temperature (200°C) processed amorphous silicon photodiodes were developed successfully by balancing the tradeoffs

  8. Metal oxide semiconductor thin-film transistors for flexible electronics

    NASA Astrophysics Data System (ADS)

    Petti, Luisa; Münzenrieder, Niko; Vogt, Christian; Faber, Hendrik; Büthe, Lars; Cantarella, Giuseppe; Bottacchi, Francesca; Anthopoulos, Thomas D.; Tröster, Gerhard

    2016-06-01

    The field of flexible electronics has rapidly expanded over the last decades, pioneering novel applications, such as wearable and textile integrated devices, seamless and embedded patch-like systems, soft electronic skins, as well as imperceptible and transient implants. The possibility to revolutionize our daily life with such disruptive appliances has fueled the quest for electronic devices which yield good electrical and mechanical performance and are at the same time light-weight, transparent, conformable, stretchable, and even biodegradable. Flexible metal oxide semiconductor thin-film transistors (TFTs) can fulfill all these requirements and are therefore considered the most promising technology for tomorrow's electronics. This review reflects the establishment of flexible metal oxide semiconductor TFTs, from the development of single devices, large-area circuits, up to entirely integrated systems. First, an introduction on metal oxide semiconductor TFTs is given, where the history of the field is revisited, the TFT configurations and operating principles are presented, and the main issues and technological challenges faced in the area are analyzed. Then, the recent advances achieved for flexible n-type metal oxide semiconductor TFTs manufactured by physical vapor deposition methods and solution-processing techniques are summarized. In particular, the ability of flexible metal oxide semiconductor TFTs to combine low temperature fabrication, high carrier mobility, large frequency operation, extreme mechanical bendability, together with transparency, conformability, stretchability, and water dissolubility is shown. Afterward, a detailed analysis of the most promising metal oxide semiconducting materials developed to realize the state-of-the-art flexible p-type TFTs is given. Next, the recent progresses obtained for flexible metal oxide semiconductor-based electronic circuits, realized with both unipolar and complementary technology, are reported. In particular

  9. Nontraditional Amorphous Oxide Semiconductor Thin-Film Transistor Fabrication

    NASA Astrophysics Data System (ADS)

    Sundholm, Eric Steven

    Fabrication techniques and process integration considerations for amorphous oxide semiconductor (AOS) thin-film transistors (TFTs) constitute the central theme of this dissertation. Within this theme three primary areas of focus are pursued. The first focus involves formulating a general framework for assessing passivation. Avoiding formation of an undesirable backside accumulation layer in an AOS bottom-gate TFT is accomplished by (i) choosing a passivation layer in which the charge neutrality level is aligned with (ideal case) or higher in energy than that of the semiconductor channel layer charge neutrality level, and (ii) depositing the passivation layer in such a manner that a negligible density of oxygen vacancies are present at the channel-passivation layer interface. Two AOS TFT passivation schemes are explored. Sputter-deposited zinc tin silicon oxide (ZTSO) appears promising for suppressing the effects of negative bias illumination stress (NBIS) with respect to ZTO and IGZO TFTs. Solution-deposited silicon dioxide is used as a barrier layer to subsequent PECVD silicon dioxide deposition, yielding ZTO TFT transfer curves showing that the dual-layer passivation process does not significantly alter ZTO TFT electrical characteristics. The second focus involves creating an adaptable back-end process compatible with flexible substrates. A detailed list of possible via formation techniques is presented with particular focus on non-traditional and adaptable techniques. Two of the discussed methods, “hydrophobic surface treatment”and “printed local insulator,” are demonstrated and proven effective. The third focus is printing AOS TFT channel layers in order to create an adaptable and additive front-end integrated circuit fabrication scheme. Printed zinc indium aluminum oxide (ZIAO) and indium gallium zinc oxide (IGZO) channel layers are demonstrated using a SonoPlot piezoelectric printing system. Finally, challenges associated with printing electronic

  10. Self-formed copper oxide contact interlayer for high-performance oxide thin film transistors

    SciTech Connect

    Gao, Xu E-mail: TSUKAGOSHI.Kazuhito@nims.go.jp; Aikawa, Shinya; Mitoma, Nobuhiko; Lin, Meng-Fang; Kizu, Takio; Tsukagoshi, Kazuhito E-mail: TSUKAGOSHI.Kazuhito@nims.go.jp; Nabatame, Toshihide

    2014-07-14

    Oxide thin film transistor employing copper source/drain electrodes shows a small turn on voltage and reduced hysteresis. Cross-sectional high-resolution transmission electron microscopy image confirmed the formation of ∼4 nm CuO{sub x} related interlayer. The lower bond-dissociation energy of Cu-O compared to Si-O and In-O suggests that the interlayer was formed by adsorbing oxygen molecules from surrounding environment instead of getting oxygen atoms from the semiconductor film. The formation of CuO{sub x} interlayer acting as an acceptor could suppress the carrier concentration in the transistor channel, which would be utilized to control the turn on voltage shifts in oxide thin film transistors.

  11. Molybdenum as a contact material in zinc tin oxide thin film transistors

    SciTech Connect

    Hu, W.; Peterson, R. L.

    2014-05-12

    Amorphous oxide semiconductors are of increasing interest for a variety of thin film electronics applications. Here, the contact properties of different source/drain electrode materials to solution-processed amorphous zinc tin oxide (ZTO) thin-film transistors are studied using the transmission line method. The width-normalized contact resistance between ZTO and sputtered molybdenum is measured to be 8.7 Ω-cm, which is 10, 20, and 600 times smaller than that of gold/titanium, indium tin oxide, and evaporated molybdenum electrodes, respectively. The superior contact formed using sputtered molybdenum is due to a favorable work function lineup, an insulator-free interface, bombardment of ZTO during molybdenum sputtering, and trap-assisted tunneling. The transfer length of the sputtered molybdenum/ZTO contact is 0.34 μm, opening the door to future radio-frequency sub-micron molybdenum/ZTO thin film transistors.

  12. Morphological impact of zinc oxide layers on the device performance in thin-film transistors.

    PubMed

    Faber, Hendrik; Klaumünzer, Martin; Voigt, Michael; Galli, Diana; Vieweg, Benito F; Peukert, Wolfgang; Spiecker, Erdmann; Halik, Marcus

    2011-03-01

    Zinc oxide thin-films are prepared either by spin coating of an ethanolic dispersion of nanoparticles (NP, diameter 5 nm) or by spray pyrolysis of a zinc acetate dihydrate precursor. High-resolution electron microscopy studies reveal a monolayer of particles for the low temperature spin coating approach and larger crystalline domains of more than 30 nm for the spray pyrolysis technique. Thin-film transistor devices (TFTs) based on spray pyrolysis films exhibit higher electron mobilities of up to 24 cm2 V(-1) s(-1) compared to 0.6 cm2 V(-1) s(-1) for NP based TFTs. These observations were dedicated to a reduced number of grain boundaries within the transistor channel. PMID:21116548

  13. Zinc oxide integrated area efficient high output low power wavy channel thin film transistor

    SciTech Connect

    Hanna, A. N.; Ghoneim, M. T.; Bahabry, R. R.; Hussain, A. M.; Hussain, M. M.

    2013-11-25

    We report an atomic layer deposition based zinc oxide channel material integrated thin film transistor using wavy channel architecture allowing expansion of the transistor width in the vertical direction using the fin type features. The experimental devices show area efficiency, higher normalized output current, and relatively lower power consumption compared to the planar architecture. This performance gain is attributed to the increased device width and an enhanced applied electric field due to the architecture when compared to a back gated planar device with the same process conditions.

  14. Fully transparent thin film transistors based on zinc oxide channel layer and molybdenum doped indium oxide electrodes

    NASA Astrophysics Data System (ADS)

    MÄ dzik, Mateusz; Elamurugu, Elangovan; Viegas, Jaime

    2016-03-01

    In this work we report the fabrication of thin film transistors (TFT) with zinc oxide channel and molybdenum doped indium oxide (IMO) electrodes, achieved by room temperature sputtering. A set of devices was fabricated, with varying channel width and length from 5μm to 300μm. Output and transfer characteristics were then extracted to study the performance of thin film transistors, namely threshold voltage and saturation current, enabling to determine optimal fabrication process parameters. Optical transmission in the UV-VIS-IR are also reported.

  15. Thin-film transistor fabricated in single-crystalline transparent oxide semiconductor.

    PubMed

    Nomura, Kenji; Ohta, Hiromichi; Ueda, Kazushige; Kamiya, Toshio; Hirano, Masahiro; Hosono, Hideo

    2003-05-23

    We report the fabrication of transparent field-effect transistors using a single-crystalline thin-film transparent oxide semiconductor, InGaO3(ZnO)5, as an electron channel and amorphous hafnium oxide as a gate insulator. The device exhibits an on-to-off current ratio of approximately 106 and a field-effect mobility of approximately 80 square centimeters per volt per second at room temperature, with operation insensitive to visible light irradiation. The result provides a step toward the realization of transparent electronics for next-generation optoelectronics. PMID:12764192

  16. Significant electrical control of amorphous oxide thin film transistors by an ultrathin Ti surface polarity modifier

    SciTech Connect

    Cho, Byungsu; Choi, Yonghyuk; Shin, Seokyoon; Jeon, Heeyoung; Seo, Hyungtak; Jeon, Hyeongtag

    2014-01-27

    We demonstrate an enhanced electrical stability through a Ti oxide (TiO{sub x}) layer on the amorphous InGaZnO (a-IGZO) back-channel; this layer acts as a surface polarity modifier. Ultrathin Ti deposited on the a-IGZO existed as a TiO{sub x} thin film, resulting in oxygen cross-binding with a-IGZO surface. The electrical properties of a-IGZO thin film transistors (TFTs) with TiO{sub x} depend on the surface polarity change and electronic band structure evolution. This result indicates that TiO{sub x} on the back-channel serves as not only a passivation layer protecting the channel from ambient molecules or process variables but also a control layer of TFT device parameters.

  17. Dual Gate Thin Film Transistors Based on Indium Oxide Active Layers

    SciTech Connect

    Kekuda, Dhananjaya; Rao, K. Mohan; Tolpadi, Amita; Chu, C. W.

    2011-07-15

    Polycrystalline Indium Oxide (In{sub 2}O{sub 3}) thin films were employed as an active channel layer for the fabrication of bottom and top gate thin film transistors. While conventional SiO{sub 2} served as a bottom gate dielectric, cross-linked poly-4-vinylphenol (PVP) was used a top gate dielectric. These nano-crystalline TFTs exhibited n-channel behavior with their transport behavior highly dependent on the thickness of the channel. The correlation between the thickness of the active layer and TFT parameters such as on/off ratio, field-effect mobility, threshold voltage were carried out. The optical spectra revealed a high transmittance in the entire visible region, thus making them promising candidates for the display technology.

  18. Dual operation characteristics of resistance random access memory in indium-gallium-zinc-oxide thin film transistors

    SciTech Connect

    Yang, Jyun-Bao; Chen, Yu-Ting; Chu, Ann-Kuo; Chang, Ting-Chang; Huang, Jheng-Jie; Chen, Yu-Chun; Tseng, Hsueh-Chih; Sze, Simon M.

    2014-04-14

    In this study, indium-gallium-zinc-oxide thin film transistors can be operated either as transistors or resistance random access memory devices. Before the forming process, current-voltage curve transfer characteristics are observed, and resistance switching characteristics are measured after a forming process. These resistance switching characteristics exhibit two behaviors, and are dominated by different mechanisms. The mode 1 resistance switching behavior is due to oxygen vacancies, while mode 2 is dominated by the formation of an oxygen-rich layer. Furthermore, an easy approach is proposed to reduce power consumption when using these resistance random access memory devices with the amorphous indium-gallium-zinc-oxide thin film transistor.

  19. Electric field modulation of thermopower for transparent amorphous oxide thin film transistors

    NASA Astrophysics Data System (ADS)

    Koide, Hirotaka; Nagao, Yuki; Koumoto, Kunihito; Takasaki, Yuka; Umemura, Tomonari; Kato, Takeharu; Ikuhara, Yuichi; Ohta, Hiromichi

    2010-11-01

    To clarify the electronic density of states (DOS) around the conduction band bottom for state of the art transparent amorphous oxide semiconductors (TAOSs), InGaZnO4 and In2MgO4, we fabricated TAOS-based transparent thin film transistors (TTFTs) and measured their gate voltage dependence of thermopower (S). TAOS-based TTFTs exhibit an unusual S behavior. The |S|-value abruptly increases but then gradually decreases as Vg increases, clearly suggesting the antiparabolic shaped DOS is hybridized with the original parabolic shaped DOS around the conduction band bottom.

  20. Performance of Indium Gallium Zinc Oxide Thin-Film Transistors in Saline Solution

    NASA Astrophysics Data System (ADS)

    Gupta, S.; Lacour, S. P.

    2016-06-01

    Transistors are often envisioned as alternative transducing devices to microelectrodes to communicate with the nervous system. Independently of the selected technology, the transistors should have reliable performance when exposed to physiological conditions (37°C, 5% CO2). Here, we report on the reliable performance of parylene encapsulated indium gallium zinc oxide (IGZO) based thin-film transistors (TFTs) after prolonged exposure to phosphate buffer saline solution in an incubator. The encapsulated IGZO TFTs (W/L = 500 μm/20 μm) have an ON/OFF current ratio of 107 and field effect mobility of 8.05 ± 0.78 cm2/Vs. The transistors operate within 4 V; their threshold voltages and subthreshold slope are ~1.9 V and 200 mV/decade, respectively. After weeks immersed in saline solution and at 37°C, we did not observe any significant deterioration in the transistors' performance. The long-term stability of IGZO transistors at physiological conditions is a promising result in the direction of metal oxide bioelectronics.

  1. Performance of Indium Gallium Zinc Oxide Thin-Film Transistors in Saline Solution

    NASA Astrophysics Data System (ADS)

    Gupta, S.; Lacour, S. P.

    2016-03-01

    Transistors are often envisioned as alternative transducing devices to microelectrodes to communicate with the nervous system. Independently of the selected technology, the transistors should have reliable performance when exposed to physiological conditions (37°C, 5% CO2). Here, we report on the reliable performance of parylene encapsulated indium gallium zinc oxide (IGZO) based thin-film transistors (TFTs) after prolonged exposure to phosphate buffer saline solution in an incubator. The encapsulated IGZO TFTs (W/L = 500 μm/20 μm) have an ON/OFF current ratio of 107 and field effect mobility of 8.05 ± 0.78 cm2/Vs. The transistors operate within 4 V; their threshold voltages and subthreshold slope are ~1.9 V and 200 mV/decade, respectively. After weeks immersed in saline solution and at 37°C, we did not observe any significant deterioration in the transistors' performance. The long-term stability of IGZO transistors at physiological conditions is a promising result in the direction of metal oxide bioelectronics.

  2. Codoping of zinc and tungsten for practical high-performance amorphous indium-based oxide thin film transistors

    NASA Astrophysics Data System (ADS)

    Kizu, Takio; Mitoma, Nobuhiko; Miyanaga, Miki; Awata, Hideaki; Nabatame, Toshihide; Tsukagoshi, Kazuhito

    2015-09-01

    Using practical high-density sputtering targets, we investigated the effect of Zn and W codoping on the thermal stability of the amorphous film and the electrical characteristics in thin film transistors. zinc oxide is a potentially conductive component while W oxide is an oxygen vacancy suppressor in oxide films. The oxygen vacancy from In-O and Zn-O was suppressed by the W additive because of the high oxygen bond dissociation energy. With controlled codoping of W and Zn, we demonstrated a high mobility with a maximum mobility of 40 cm2/V s with good stability under a negative bias stress in InWZnO thin film transistors.

  3. Stretchable metal oxide thin film transistors on engineered substrate for electronic skin applications.

    PubMed

    Romeo, Alessia; Lacour, Stphanie P

    2015-08-01

    Electronic skins aim at providing distributed sensing and computation in a large-area and elastic membrane. Control and addressing of high-density soft sensors will be achieved when thin film transistor matrices are also integrated in the soft carrier substrate. Here, we report on the design, manufacturing and characterization of metal oxide thin film transistors on these stretchable substrates. The TFTs are integrated onto an engineered silicone substrate with embedded strain relief to protect the devices from catastrophic cracking. The TFT stack is composed of an amorphous In-Ga-Zn-O active layer, a hybrid AlxOy/Parylene dielectric film, gold electrodes and interconnects. All layers are prepared and patterned with planar, low temperature and dry processing. We demonstrate the interconnected IGZO TFTs sustain applied tensile strain up to 20% without electrical degradation and mechanical fracture. Active devices are critical for distributed sensing. The compatibility of IGZO TFTs with soft and biocompatible substrates is an encouraging step towards wearable electronic skins. PMID:26738152

  4. Controllable film densification and interface flatness for high-performance amorphous indium oxide based thin film transistors

    SciTech Connect

    Ou-Yang, Wei E-mail: TSUKAGOSHI.Kazuhito@nims.go.jp; Mitoma, Nobuhiko; Kizu, Takio; Gao, Xu; Lin, Meng-Fang; Tsukagoshi, Kazuhito E-mail: TSUKAGOSHI.Kazuhito@nims.go.jp; Nabatame, Toshihide

    2014-10-20

    To avoid the problem of air sensitive and wet-etched Zn and/or Ga contained amorphous oxide transistors, we propose an alternative amorphous semiconductor of indium silicon tungsten oxide as the channel material for thin film transistors. In this study, we employ the material to reveal the relation between the active thin film and the transistor performance with aid of x-ray reflectivity study. By adjusting the pre-annealing temperature, we find that the film densification and interface flatness between the film and gate insulator are crucial for achieving controllable high-performance transistors. The material and findings in the study are believed helpful for realizing controllable high-performance stable transistors.

  5. Thin Film Transistors On Plastic Substrates

    DOEpatents

    Carey, Paul G.; Smith, Patrick M.; Sigmon, Thomas W.; Aceves, Randy C.

    2004-01-20

    A process for formation of thin film transistors (TFTs) on plastic substrates replaces standard thin film transistor fabrication techniques, and uses sufficiently lower processing temperatures so that inexpensive plastic substrates may be used in place of standard glass, quartz, and silicon wafer-based substrates. The silicon based thin film transistor produced by the process includes a low temperature substrate incapable of withstanding sustained processing temperatures greater than about 250.degree. C., an insulating layer on the substrate, a layer of silicon on the insulating layer having sections of doped silicon, undoped silicon, and poly-silicon, a gate dielectric layer on the layer of silicon, a layer of gate metal on the dielectric layer, a layer of oxide on sections of the layer of silicon and the layer of gate metal, and metal contacts on sections of the layer of silicon and layer of gate metal defining source, gate, and drain contacts, and interconnects.

  6. Self-heating induced instability of oxide thin film transistors under dynamic stress

    NASA Astrophysics Data System (ADS)

    Kise, Kahori; Fujii, Mami N.; Urakawa, Satoshi; Yamazaki, Haruka; Kawashima, Emi; Tomai, Shigekazu; Yano, Koki; Wang, Dapeng; Furuta, Mamoru; Ishikawa, Yasuaki; Uraoka, Yukiharu

    2016-01-01

    Degradation caused by Joule heating of transparent amorphous oxide semiconductor thin-film transistors (TFTs) is an important issue for display technology. Deep understanding of the mechanism of self-heating degradation generated by driving pulse voltage will pave the way for the development of highly reliable flexible displays. In this work, by using a pseudo interval measurement method, we examined the relationship of the highest and the lowest heating temperature in pulse 1 cycle and frequency. These self-heating converged to a constant temperature under pulse voltage applied at 1 kHz. Moreover, the long-term reliability under positive-bias stress voltage at 1 kHz of low converged temperature condition was improved relative to that of the stress voltage at 10 Hz of dynamic temperature change condition. We discussed the degradation mechanism of oxide TFTs generated by pulse voltage, and clarified that the degradation was accelerated by thermionic emission which occurred at low frequency.

  7. Performance enhancement of amorphous indium-zinc-oxide thin film transistors by microwave annealing

    NASA Astrophysics Data System (ADS)

    Xu, Rui; He, Jian; Li, Wei; Paine, David C.

    2015-12-01

    The effect of microwave annealing on the field effect mobility and threshold voltage of amorphous indium zinc oxide (a-IZO) thin film transistors (TFTs) is reported. A control device with traditional hotplate annealing at 200 °C for 1 h was applied for comparison. The results show that both microwave annealing and low-temperature hotplate annealing increase the field effect mobility from 12.3 cm2/V s in as-deposited state to ∼19 cm2/V s in annealed state. However, the negative shift in threshold voltage with microwave annealing (from 0.23 V to -2.86 V) is smaller than that with low-temperature hotplate annealing (to -9 V). A mechanism related with the electrical properties of a-IZO material is proposed. This rapid low-temperature annealing technology makes a-IZO TFTs promising for use in flexible, transparent electronics.

  8. Interface location-controlled indium gallium zinc oxide thin-film transistors using a solution process

    NASA Astrophysics Data System (ADS)

    Na, Jae Won; Kim, Yeong-gyu; Jung, Tae Soo; Tak, Young Jun; Park, Sung Pyo; Park, Jeong Woo; Kim, Si Joon; Kim, Hyun Jae

    2016-03-01

    The role of an interface as an electron-trapping layer in double-stacked indium gallium zinc oxide (IGZO) thin-film transistors (TFTs) was investigated and interface location-controlled (ILC) IGZO TFTs were introduced. In the ILC TFTs, the thickness of the top and bottom IGZO layers is controlled to change the location of the interface layer. The system exhibited improved electrical characteristics as the location of the interface layer moved further from the gate insulator: field-effect mobility increased from 0.36 to 2.17 cm2 V-1 s-1, and the on-current increased from 2.43  ×  10-5 to 1.33  ×  10-4 A. The enhanced electrical characteristics are attributed to the absence of an electron-trapping interface layer in the effective channel layer where electrons are accumulated under positive gate bias voltage.

  9. Contact resistance improvement using interfacial silver nanoparticles in amorphous indium-zinc-oxide thin film transistors

    SciTech Connect

    Xu, Rui; He, Jian; Song, Yang; Li, Wei; Zaslavsky, A.; Paine, D. C.

    2014-09-01

    We describe an approach to reduce the contact resistance at compositional conducting/semiconducting indium-zinc-oxide (IZO) homojunctions used for contacts in thin film transistors (TFTs). By introducing silver nanoparticles (Ag NPs) at the homojunction interface between the conducting IZO electrodes and the amorphous IZO channel, we reduce the specific contact resistance, obtained by transmission line model measurements, down to ∼10{sup −2 }Ω cm{sup 2}, ∼3 orders of magnitude lower than either NP-free homojunction contacts or solid Ag metal contacts. The resulting back-gated TFTs with Ag NP contacts exhibit good field effect mobility of ∼27 cm{sup 2}/V s and an on/off ratio >10{sup 7}. We attribute the improved contact resistance to electric field concentration by the Ag NPs.

  10. Remarkably high mobility ultra-thin-film metal-oxide transistor with strongly overlapped orbitals

    PubMed Central

    Wei Shih, Chen; Chin, Albert; Fu Lu, Chun; Fang Su, Wei

    2016-01-01

    High mobility channel thin-film-transistor (TFT) is crucial for both display and future generation integrated circuit. We report a new metal-oxide TFT that has an ultra-thin 4.5 nm SnO2 thickness for both active channel and source-drain regions, very high 147 cm2/Vs field-effect mobility, high ION/IOFF of 2.3 × 107, small 110 mV/dec sub-threshold slope, and a low VD of 2.5 V for low power operation. This mobility is already better than chemical-vapor-deposition grown multi-layers MoS2 TFT. From first principle quantum-mechanical calculation, the high mobility TFT is due to strongly overlapped orbitals. PMID:26744240

  11. Contact resistance improvement using interfacial silver nanoparticles in amorphous indium-zinc-oxide thin film transistors

    NASA Astrophysics Data System (ADS)

    Xu, Rui; He, Jian; Song, Yang; Li, Wei; Zaslavsky, A.; Paine, D. C.

    2014-09-01

    We describe an approach to reduce the contact resistance at compositional conducting/semiconducting indium-zinc-oxide (IZO) homojunctions used for contacts in thin film transistors (TFTs). By introducing silver nanoparticles (Ag NPs) at the homojunction interface between the conducting IZO electrodes and the amorphous IZO channel, we reduce the specific contact resistance, obtained by transmission line model measurements, down to ˜10-2 Ω cm2, ˜3 orders of magnitude lower than either NP-free homojunction contacts or solid Ag metal contacts. The resulting back-gated TFTs with Ag NP contacts exhibit good field effect mobility of ˜27 cm2/V s and an on/off ratio >107. We attribute the improved contact resistance to electric field concentration by the Ag NPs.

  12. Remarkably high mobility ultra-thin-film metal-oxide transistor with strongly overlapped orbitals

    NASA Astrophysics Data System (ADS)

    Wei Shih, Chen; Chin, Albert; Fu Lu, Chun; Fang Su, Wei

    2016-01-01

    High mobility channel thin-film-transistor (TFT) is crucial for both display and future generation integrated circuit. We report a new metal-oxide TFT that has an ultra-thin 4.5 nm SnO2 thickness for both active channel and source-drain regions, very high 147 cm2/Vs field-effect mobility, high ION/IOFF of 2.3 × 107, small 110 mV/dec sub-threshold slope, and a low VD of 2.5 V for low power operation. This mobility is already better than chemical-vapor-deposition grown multi-layers MoS2 TFT. From first principle quantum-mechanical calculation, the high mobility TFT is due to strongly overlapped orbitals.

  13. Improved Stability Of Amorphous Zinc Tin Oxide Thin Film Transistors Using Molecular Passivation

    SciTech Connect

    Rajachidambaram, Meena Suhanya; Pandey, Archana; Vilayur Ganapathy, Subramanian; Nachimuthu, Ponnusamy; Thevuthasan, Suntharampillai; Herman, Gregory S.

    2013-10-21

    The role of back channel surface chemistry on amorphous zinc tin oxide (ZTO) bottom gate thin film transistors (TFT) have been characterized by positive bias-stress measurements and x-ray photoelectron spectroscopy. Positive bias-stress turn-on voltage shifts for ZTO-TFTs were significantly reduced by passivation of back channel surfaces with self-assembled monolayers of n-hexylphosphonic acid (n-HPA) when compared to ZTO-TFTs with no passivation. These results indicate that adsorption of molecular species on exposed back channel of ZTO-TFTs strongly influence observed turn-on voltage shifts, as opposed to charge injection into the dielectric or trapping due to oxygen vacancies.

  14. Remarkably high mobility ultra-thin-film metal-oxide transistor with strongly overlapped orbitals.

    PubMed

    Shih, Chen Wei; Chin, Albert; Lu, Chun Fu; Su, Wei Fang

    2016-01-01

    High mobility channel thin-film-transistor (TFT) is crucial for both display and future generation integrated circuit. We report a new metal-oxide TFT that has an ultra-thin 4.5 nm SnO2 thickness for both active channel and source-drain regions, very high 147 cm(2)/Vs field-effect mobility, high ION/IOFF of 2.3 × 10(7), small 110 mV/dec sub-threshold slope, and a low VD of 2.5 V for low power operation. This mobility is already better than chemical-vapor-deposition grown multi-layers MoS2 TFT. From first principle quantum-mechanical calculation, the high mobility TFT is due to strongly overlapped orbitals. PMID:26744240

  15. A numerical study on the mechanical characteristics of zinc oxide-based transparent thin film transistors.

    PubMed

    Lee, D-K; Park, K; Ahn, J-H; Lee, N-E; Kim, Y-J

    2011-07-01

    Zinc Oxide (ZnO) based Thin Film Transistors (TFTs) have been fabricated and analyzed to investigate mechanical characteristics regarding the stress, strain and deformation of electro circuits using the Finite Element Method (FEM). As the best compromise between the stretching and bending abilities, the coating thickness of SU-8 can be as important for bendability as a neutral mechanical plane. The neutral mechanical plane in electro circuits was designed for obtaining flexibility, e.g., bendability, in a previous numerical study. After that, through experimental validation, we observed what degree of SU-8 thickness was attributable for improved mechanical stability. The results suggest that not only numerical but also experimental measurements of the deformation and SU-8 coating thickness in electro circuits are useful for enhancing structural stability. PMID:22121623

  16. High-mobility thin film transistors with neodymium-substituted indium oxide active layer

    SciTech Connect

    Lin, Zhenguo; Lan, Linfeng Xiao, Peng; Sun, Sheng; Li, Yuzhi; Song, Wei; Gao, Peixiong; Wang, Lei; Ning, Honglong; Peng, Junbiao

    2015-09-14

    Thin-film transistors (TFTs) with neodymium-substituted indium oxide (InNdO) channel layer were demonstrated. The structural properties of the InNdO films as a function of annealing temperature have been analyzed using X-ray diffraction and transmission electron microscopy. The InNdO thin films showed polycrystalline nature when annealed at 450 °C with a lattice parameter (cubic cell) of 10.255 Å, which is larger than the cubic In{sub 2}O{sub 3} film (10.117 Å). The high-resolution transmission electron microscopy and energy dispersive X-ray spectroscopy showed that no Nd{sub 2}O{sub 3} clusters were found in the InNdO film, implying that Nd was incorporated into the In{sub 2}O{sub 3} lattice. The InNdO TFTs annealed at 450 °C exhibited more excellent electrical properties with a high mobility of 20.4 cm{sup 2} V{sup −1} s{sup −1} and better electric bias stability compared to those annealed at 300 °C, which was attributed to the reduction of the scattering centers and/or charge traps due to the decrease of the |Nd3d{sub 5/2}{sup 5}4f{sup 4}O2p{sup −1}〉 electron configuration.

  17. Impact of glycerol on zinc-oxide-based thin film transistors with indium molybdenum oxide transparent electrodes

    NASA Astrophysics Data System (ADS)

    MÄ dzik, Mateusz; Elamurugu, Elangovan; Flores, Raquel; Viegas, Jaime

    2016-02-01

    We report the fabrication of thin film transistors with ZnO channel and indium molybdenum oxide electrodes by sputtering. The fabricated transistors were then exposed to glycerol. We observe a temporary change in device performance after immersion of the FET in glycerol. Control structures without channel material are also used for demonstrating that the effect of saturation current increase is not due to glycerol alone as sugar alcohol is a low conductive medium. Various electrical and optical parameters are extracted. The presented results are useful for further integration of photonics and electronics in sensing applications

  18. Green processing of metal oxide core-shell nanoparticles as low-temperature dielectrics in organic thin-film transistors.

    PubMed

    Portilla, Luis; Etschel, Sebastian H; Tykwinski, Rik R; Halik, Marcus

    2015-10-21

    TiO2 , Fe3 O4, AlOx , ITO (indium tin oxide), and CeO2 nanoparticles are tailored to exhibit excellent dispersability in deionized water and alcohols. The latter provides an ecofriendly solution for processing metal oxide nanoparticles at a neutral pH. Water-processed dielectrics from the metal oxide nanoparticles are incorporated into organic thin-film transistors fabricated on rigid and flexible substrates. PMID:26308740

  19. Impact of oxygen plasma treatment on the device performance of zinc oxide nanoparticle-based thin-film transistors.

    PubMed

    Faber, Hendrik; Hirschmann, Johannes; Klaumünzer, Martin; Braunschweig, Björn; Peukert, Wolfgang; Halik, Marcus

    2012-03-01

    Thin-films of zinc oxide nanoparticles were investigated by photoluminescence spectroscopy and a broad defect-related yellow-green emission was observed. Oxygen plasma treatment was applied in order to reduce the number of defects, and the emission intensity was quenched to 4% of the initial value. Thin-film transistors that incorporate the nanoparticles as active semiconducting layers show an improved device performance after oxygen plasma treatment. The maximum drain current and the charge carrier mobility increased more than 1 order of magnitude up to a nominal value of 23 cm(2) V(-1) s(-1) and the threshold voltage was lowered. PMID:22391057

  20. Synergistic approach to high-performance oxide thin film transistors using a bilayer channel architecture.

    PubMed

    Yu, Xinge; Zhou, Nanjia; Smith, Jeremy; Lin, Hui; Stallings, Katie; Yu, Junsheng; Marks, Tobin J; Facchetti, Antonio

    2013-08-28

    We report here a bilayer metal oxide thin film transistor concept (bMO TFT) where the channel has the structure: dielectric/semiconducting indium oxide (In2O3) layer/semiconducting indium gallium oxide (IGO) layer. Both semiconducting layers are grown from solution via a low-temperature combustion process. The TFT mobilities of bottom-gate/top-contact bMO TFTs processed at T = 250 °C are ~5tmex larger (~2.6 cm(2)/(V s)) than those of single-layer IGO TFTs (~0.5 cm(2)/(V s)), reaching values comparable to single-layer combustion-processed In2O3 TFTs (~3.2 cm(2)/(V s)). More importantly, and unlike single-layer In2O3 TFTs, the threshold voltage of the bMO TFTs is ~0.0 V, and the current on/off ratio is significantly enhanced to ~1 × 10(8) (vs ~1 × 10(4) for In2O3). The microstructure and morphology of the In2O3/IGO bilayers are analyzed by X-ray diffraction, atomic force microscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy, revealing the polycrystalline nature of the In2O3 layer and the amorphous nature of the IGO layer. This work demonstrates that solution-processed metal oxides can be implemented in bilayer TFT architectures with significantly enhanced performance. PMID:23876148

  1. Effect of hydrogen on dynamic charge transport in amorphous oxide thin film transistors.

    PubMed

    Kim, Taeho; Nam, Yunyong; Hur, Ji-Hyun; Park, Sang-Hee Ko; Jeon, Sanghun

    2016-08-12

    Hydrogen in zinc oxide based semiconductors functions as a donor or a defect de-activator depending on its concentration, greatly affecting the device characteristics of oxide thin-film transistors (TFTs). Thus, controlling the hydrogen concentration in oxide semiconductors is very important for achieving high mobility and minimizing device instability. In this study, we investigated the charge transport dynamics of the amorphous semiconductor InGaZnO at various hydrogen concentrations as a function of the deposition temperature of the gate insulator. To examine the nature of dynamic charge trapping, we employed short-pulse current-voltage and transient current-time measurements. Among various examined oxide devices, that with a high hydrogen concentration exhibits the best performance characteristics, such as high saturation mobility (10.9 cm(2) v(-1) s(-1)), low subthreshold slope (0.12 V/dec), and negligible hysteresis, which stem from low defect densities and negligible transient charge trapping. Our finding indicates that hydrogen atoms effectively passivate the defects in subgap states of the bulk semiconductor, minimizing the mobility degradation and threshold voltage instability. This study indicates that hydrogen plays a useful role in TFTs by improving the device performance and stability. PMID:27363543

  2. Effect of hydrogen on dynamic charge transport in amorphous oxide thin film transistors

    NASA Astrophysics Data System (ADS)

    Kim, Taeho; Nam, Yunyong; Hur, Ji-Hyun; Park, Sang-Hee Ko; Jeon, Sanghun

    2016-08-01

    Hydrogen in zinc oxide based semiconductors functions as a donor or a defect de-activator depending on its concentration, greatly affecting the device characteristics of oxide thin-film transistors (TFTs). Thus, controlling the hydrogen concentration in oxide semiconductors is very important for achieving high mobility and minimizing device instability. In this study, we investigated the charge transport dynamics of the amorphous semiconductor InGaZnO at various hydrogen concentrations as a function of the deposition temperature of the gate insulator. To examine the nature of dynamic charge trapping, we employed short-pulse current‑voltage and transient current‑time measurements. Among various examined oxide devices, that with a high hydrogen concentration exhibits the best performance characteristics, such as high saturation mobility (10.9 cm2 v‑1 s‑1), low subthreshold slope (0.12 V/dec), and negligible hysteresis, which stem from low defect densities and negligible transient charge trapping. Our finding indicates that hydrogen atoms effectively passivate the defects in subgap states of the bulk semiconductor, minimizing the mobility degradation and threshold voltage instability. This study indicates that hydrogen plays a useful role in TFTs by improving the device performance and stability.

  3. Codoping of zinc and tungsten for practical high-performance amorphous indium-based oxide thin film transistors

    SciTech Connect

    Kizu, Takio E-mail: TSUKAGOSHI.Kazuhito@nims.go.jp; Mitoma, Nobuhiko; Tsukagoshi, Kazuhito E-mail: TSUKAGOSHI.Kazuhito@nims.go.jp; Miyanaga, Miki; Awata, Hideaki; Nabatame, Toshihide

    2015-09-28

    Using practical high-density sputtering targets, we investigated the effect of Zn and W codoping on the thermal stability of the amorphous film and the electrical characteristics in thin film transistors. zinc oxide is a potentially conductive component while W oxide is an oxygen vacancy suppressor in oxide films. The oxygen vacancy from In-O and Zn-O was suppressed by the W additive because of the high oxygen bond dissociation energy. With controlled codoping of W and Zn, we demonstrated a high mobility with a maximum mobility of 40 cm{sup 2}/V s with good stability under a negative bias stress in InWZnO thin film transistors.

  4. High Performance, Low Temperature Solution-Processed Barium and Strontium Doped Oxide Thin Film Transistors

    PubMed Central

    2013-01-01

    Amorphous mixed metal oxides are emerging as high performance semiconductors for thin film transistor (TFT) applications, with indium gallium zinc oxide, InGaZnO (IGZO), being one of the most widely studied and best performing systems. Here, we investigate alkaline earth (barium or strontium) doped InBa(Sr)ZnO as alternative, semiconducting channel layers and compare their performance of the electrical stress stability with IGZO. In films fabricated by solution-processing from metal alkoxide precursors and annealed to 450 °C we achieve high field-effect electron mobility up to 26 cm2 V–1 s–1. We show that it is possible to solution-process these materials at low process temperature (225–200 °C yielding mobilities up to 4.4 cm2 V–1 s–1) and demonstrate a facile “ink-on-demand” process for these materials which utilizes the alcoholysis reaction of alkyl metal precursors to negate the need for complex synthesis and purification protocols. Electrical bias stress measurements which can serve as a figure of merit for performance stability for a TFT device reveal Sr- and Ba-doped semiconductors to exhibit enhanced electrical stability and reduced threshold voltage shift compared to IGZO irrespective of the process temperature and preparation method. This enhancement in stability can be attributed to the higher Gibbs energy of oxidation of barium and strontium compared to gallium. PMID:24511184

  5. High Performance, Low Temperature Solution-Processed Barium and Strontium Doped Oxide Thin Film Transistors.

    PubMed

    Banger, Kulbinder K; Peterson, Rebecca L; Mori, Kiyotaka; Yamashita, Yoshihisa; Leedham, Timothy; Sirringhaus, Henning

    2014-01-28

    Amorphous mixed metal oxides are emerging as high performance semiconductors for thin film transistor (TFT) applications, with indium gallium zinc oxide, InGaZnO (IGZO), being one of the most widely studied and best performing systems. Here, we investigate alkaline earth (barium or strontium) doped InBa(Sr)ZnO as alternative, semiconducting channel layers and compare their performance of the electrical stress stability with IGZO. In films fabricated by solution-processing from metal alkoxide precursors and annealed to 450 °C we achieve high field-effect electron mobility up to 26 cm(2) V(-1) s(-1). We show that it is possible to solution-process these materials at low process temperature (225-200 °C yielding mobilities up to 4.4 cm(2) V(-1) s(-1)) and demonstrate a facile "ink-on-demand" process for these materials which utilizes the alcoholysis reaction of alkyl metal precursors to negate the need for complex synthesis and purification protocols. Electrical bias stress measurements which can serve as a figure of merit for performance stability for a TFT device reveal Sr- and Ba-doped semiconductors to exhibit enhanced electrical stability and reduced threshold voltage shift compared to IGZO irrespective of the process temperature and preparation method. This enhancement in stability can be attributed to the higher Gibbs energy of oxidation of barium and strontium compared to gallium. PMID:24511184

  6. Effective contact resistance of zinc-tin oxide-based thin film transistors.

    PubMed

    Kang, Youjin; Han, Dongsuk; Park, Jaehyung; Shin, Sora; Choi, Duckkyun; Park, Jongwan

    2014-11-01

    We investigated different source/drain (S/D) electrode materials in thin-film transistors (TFTs) based on amorphous zinc-tin oxide (ZTO) semiconductors. The transfer length, channel conductance, and effective contact resistance between the S/D electrodes and the a-ZTO channel layer were examined. Total ON resistance (R(T)), transfer length (L(T)) and effective contact resistance (R(c-eff)) were extracted by the well-known transmission-line method (TLM) using a series of TFTs with different channel lengths. When the width of ZTO channel layer was fixed as 50 μm, the lengths were varying from 10 to 50 μm. The channel layer and S/D electrode were defined by lift-off process and for the S/D electrodes, indium-tin oxide (ITO), Cu, and Mo were used. The resistivity and work function values of electrode materials were considered when selected as candidates for S/D electrodes of ZTO-TFTs. The results showed that the ZTO-TFTs with Mo S/D electrodes had the lowest effective contact resistance indicating that ZTO-TFTs with Mo electrodes have better electrical performance compared to others. PMID:25958489

  7. Field-induced macroscopic barrier model for persistent photoconductivity in nanocrystalline oxide thin-film transistors

    NASA Astrophysics Data System (ADS)

    Choi, Hyun-Sik; Jeon, Sanghun

    2014-03-01

    Persistent photoconductivity (PPC) in nanocrystalline InZnO thin-film transistors (TFTs) was studied using carrier fluctuation measurements and transient analysis. Low-frequency noise measurements and decay kinetics indicate that the band bending by the external field together with the ionized oxygen vacancy (Vo++) generated during the light exposure is the main cause of the PPC phenomenon. Based on these observations, a field-induced macroscopic barrier model is proposed as the origin of PPC for InZnO TFTs. In particular, this model explains that the carrier separation between e and Vo++ is induced by the external field applied to the three electrodes inside the transistor.

  8. Oxide semiconductor thin-film transistors: a review of recent advances.

    PubMed

    Fortunato, E; Barquinha, P; Martins, R

    2012-06-12

    Transparent electronics is today one of the most advanced topics for a wide range of device applications. The key components are wide bandgap semiconductors, where oxides of different origins play an important role, not only as passive component but also as active component, similar to what is observed in conventional semiconductors like silicon. Transparent electronics has gained special attention during the last few years and is today established as one of the most promising technologies for leading the next generation of flat panel display due to its excellent electronic performance. In this paper the recent progress in n- and p-type oxide based thin-film transistors (TFT) is reviewed, with special emphasis on solution-processed and p-type, and the major milestones already achieved with this emerging and very promising technology are summarizeed. After a short introduction where the main advantages of these semiconductors are presented, as well as the industry expectations, the beautiful history of TFTs is revisited, including the main landmarks in the last 80 years, finishing by referring to some papers that have played an important role in shaping transparent electronics. Then, an overview is presented of state of the art n-type TFTs processed by physical vapour deposition methods, and finally one of the most exciting, promising, and low cost but powerful technologies is discussed: solution-processed oxide TFTs. Moreover, a more detailed focus analysis will be given concerning p-type oxide TFTs, mainly centred on two of the most promising semiconductor candidates: copper oxide and tin oxide. The most recent data related to the production of complementary metal oxide semiconductor (CMOS) devices based on n- and p-type oxide TFT is also be presented. The last topic of this review is devoted to some emerging applications, finalizing with the main conclusions. Related work that originated at CENIMAT|I3N during the last six years is included in more detail, which

  9. Mechanical Flexibility of Zinc Oxide Thin-Film Transistors Prepared by Transfer Printing Method

    NASA Astrophysics Data System (ADS)

    Eun, K. T.; Hwang, W. J.; Sharma, B. K.; Ahn, J. H.; Lee, Y. K.; Choa, S. H.

    In the present study, we demonstrate the performance of Zinc oxide thin film transistors (ZnO TFTs) array subjected to the strain under high bending test and the reliability of TFTs was confirmed for the bending fatigue test of 2000 cycles. Initially, ZnO TFTs were fabricated on Si substrate and subsequently transferred on flexible PET substrate using transfer printing process. It was observed that when the bending radius reached ≥ 11 mm then cracks start to initiate first at SiO2 bridges, acting as interconnecting layers among individual TFT. Whatever the strain is applied to the devices, it is almost equivalently adopted by the SiO2 bridges, as they are relatively weak compared to rest of the part. The initial cracking of destructed SiO2 bridge leads to the secondary cracks to the ITO electrodes upon further increment of bending radius. Numerical simulation suggested that the strain of SiO2 layer reached to fracture level of 0.55% which was concentrated at the edge of SiO2 bridge layer. It also suggests that the round shape of SiO2 bridge can be more fruitful to compensate the stress concentration and to prevent failure of device.

  10. Water-soluble thin film transistors and circuits based on amorphous indium-gallium-zinc oxide.

    PubMed

    Jin, Sung Hun; Kang, Seung-Kyun; Cho, In-Tak; Han, Sang Youn; Chung, Ha Uk; Lee, Dong Joon; Shin, Jongmin; Baek, Geun Woo; Kim, Tae-il; Lee, Jong-Ho; Rogers, John A

    2015-04-22

    This paper presents device designs, circuit demonstrations, and dissolution kinetics for amorphous indium-gallium-zinc oxide (a-IGZO) thin film transistors (TFTs) comprised completely of water-soluble materials, including SiNx, SiOx, molybdenum, and poly(vinyl alcohol) (PVA). Collections of these types of physically transient a-IGZO TFTs and 5-stage ring oscillators (ROs), constructed with them, show field effect mobilities (∼10 cm2/Vs), on/off ratios (∼2×10(6)), subthreshold slopes (∼220 mV/dec), Ohmic contact properties, and oscillation frequency of 5.67 kHz at supply voltages of 19 V, all comparable to otherwise similar devices constructed in conventional ways with standard, nontransient materials. Studies of dissolution kinetics for a-IGZO films in deionized water, bovine serum, and phosphate buffer saline solution provide data of relevance for the potential use of these materials and this technology in temporary biomedical implants. PMID:25805699

  11. Coffee-Ring Defined Short Channels for Inkjet-Printed Metal Oxide Thin-Film Transistors.

    PubMed

    Li, Yuzhi; Lan, Linfeng; Xiao, Peng; Sun, Sheng; Lin, Zhenguo; Song, Wei; Song, Erlong; Gao, Peixiong; Wu, Weijing; Peng, Junbiao

    2016-08-01

    Short-channel electronic devices several micrometers in length are difficult to implement by direct inkjet printing due to the limitation of position accuracy of the common inkjet printer system and the spread of functional ink on substrates. In this report, metal oxide thin-film transistors (TFTs) with channel lengths of 3.5 ± 0.7 μm were successfully fabricated with a common inkjet printer without any photolithography steps. Hydrophobic CYTOP coffee stripes, made by inkjet-printing and plasma-treating processes, were utilized to define the channel area of TFTs with channel lengths as short as ∼3.5 μm by dewetting the inks of the source/drain (S/D) precursors. Furthermore, by introduction of an ultrathin layer of PVA to modify the S/D surfaces, the spreading of precursor ink of the InOx semiconductor layer was well-controlled. The inkjet-printed short-channel TFTs exhibited a maximum mobility of 4.9 cm(2) V(-1) s(-1) and an on/off ratio of larger than 10(9). This approach of fabricating short-channel TFTs by inkjet printing will promote the large-area fabrication of short-channel TFTs in a cost-effective manner. PMID:27420373

  12. Low-voltage indium gallium zinc oxide thin film transistors on paper substrates

    NASA Astrophysics Data System (ADS)

    Lim, Wantae; Douglas, E. A.; Norton, D. P.; Pearton, S. J.; Ren, F.; Heo, Young-Woo; Son, S. Y.; Yuh, J. H.

    2010-02-01

    We have fabricated bottom-gate amorphous (α-) indium-gallium-zinc-oxide (InGaZnO4) thin film transistors (TFTs) on both paper and glass substrates at low processing temperature (≤100 °C). As a water and solvent barrier layer, cyclotene (BCB 3022-35 from Dow Chemical) was spin-coated on the entire paper substrate. TFTs on the paper substrates exhibited saturation mobility (μsat) of 1.2 cm2 V-1 s-1, threshold voltage (VTH) of 1.9 V, subthreshold gate-voltage swing (S ) of 0.65 V decade-1, and drain current on-to-off ratio (ION/IOFF) of ˜104. These values were only slightly inferior to those obtained from devices on glass substrates (μsat˜2.1 cm2 V-1 s-1, VTH˜0 V, S ˜0.74 V decade-1, and ION/IOFF=105-106). The uneven surface of the paper sheet led to relatively poor contact resistance between source-drain electrodes and channel layer. The ability to achieve InGaZnO TFTs on cyclotene-coated paper substrates demonstrates the enormous potential for applications such as low-cost and large area electronics.

  13. Characteristics of flexographic printed indium-zinc-oxide thin films as an active semiconductor layer in thin film field-effect transistors

    NASA Astrophysics Data System (ADS)

    Dilfer, Stefan; Hoffmann, Rudolf C.; Dörsam, Edgar

    2014-11-01

    Characteristics of oxide semiconductor thin film transistors prepared by flexographic printing technique have been studied. The device was a field-effect transistor substrate (15 mm × 15 mm, n-doped silicon, 90 nm SiO2 layer) with pre-structured gold electrodes and a printed active layer. The active layer was printed with a indium-zinc-oxide precursor solution and then annealed at 450 °C for 4 min on a hotplate. Influences of typographical parameters, i.e. printing pressure, anilox roller pressure, ink supply rate, printing velocity and printing plate (cliché) properties were studied. Reference active layers were produced by spin coating. The printed IZO ceramic layer with a dry film thickness between 3 and 8 nm, deposited onto the substrate for field-effect transistors provided a good performance with charge carrier mobilities (μ) up to 2.4 cm2 V-1 s-1, on/off current ratios (Ion/off ratio) up to 5.2 × 107 and mean threshold voltages (Vth) of +4 V. The characterization of the printed and annealed IZO layer by AFM revealed the amorphous nature of the printed active layer films with a root-mean square roughness of 0.8 nm.

  14. The effect of annealing temperature on the stability of gallium tin zinc oxide thin film transistors

    NASA Astrophysics Data System (ADS)

    Nguyen, Ngoc; McCall, Briana; Alston, Robert; Collis, Ward; Iyer, Shanthi

    2015-10-01

    With the growing need for large area display technology and the push for a faster and cheaper alternative to the current amorphous indium gallium zinc oxide (a-IGZO) as the active channel layer for pixel-driven thin film transistors (TFTs) display applications, gallium tin zinc oxide (GSZO) has shown to be a promising candidate due to the similar electronic configuration of Sn4+ and In3+. In this work TFTs of GSZO sputtered films with only a few atomic % of Ga and Sn have been fabricated. A systematic and detailed comparison has been made of the properties of the GSZO films annealed at two temperatures: 140 °C and 450 °C. The electrical and optical stabilities of the respective devices have been studied to gain more insight into the degradation mechanism and are correlated with the initial TFT performance prior to the application of stress. Post deposition annealing at 450 °C of the films in air was found to lead to a higher atomic concentration of Sn4+ in these films and a superior quality of the film, as attested by the higher film density and less surface and interface roughness in comparison to the lower annealed temperature device. These result in significantly reduced shallow and deep interface traps with improved performance of the device exhibiting VON of -3.5 V, ION/IOFF of 108, field-effect mobility (μFE) of 4.46 cm2 V-1s-1, and sub-threshold swing of 0.38 V dec-1. The device is stable under both electrical and optical bias for wavelengths of 550 nm and above. Thus, this work demonstrates GSZO-based TFTs as a promising viable option to the IGZO TFTs by further tailoring the film composition and relevant processing temperatures.

  15. Tungsten oxide proton conducting films for low-voltage transparent oxide-based thin-film transistors

    SciTech Connect

    Zhang, Hongliang; Wan, Qing; Wan, Changjin; Wu, Guodong; Zhu, Liqiang

    2013-02-04

    Tungsten oxide (WO{sub x}) electrolyte films deposited by reactive magnetron sputtering showed a high room temperature proton conductivity of 1.38 Multiplication-Sign 10{sup -4} S/cm with a relative humidity of 60%. Low-voltage transparent W-doped indium-zinc-oxide thin-film transistors gated by WO{sub x}-based electrolytes were self-assembled on glass substrates by one mask diffraction method. Enhancement mode operation with a large current on/off ratio of 4.7 Multiplication-Sign 10{sup 6}, a low subthreshold swing of 108 mV/decade, and a high field-effect mobility 42.6 cm{sup 2}/V s was realized. Our results demonstrated that WO{sub x}-based proton conducting films were promising gate dielectric candidates for portable low-voltage oxide-based devices.

  16. Tungsten oxide proton conducting films for low-voltage transparent oxide-based thin-film transistors

    NASA Astrophysics Data System (ADS)

    Zhang, Hongliang; Wan, Qing; Wan, Changjin; Wu, Guodong; Zhu, Liqiang

    2013-02-01

    Tungsten oxide (WOx) electrolyte films deposited by reactive magnetron sputtering showed a high room temperature proton conductivity of 1.38 × 10-4 S/cm with a relative humidity of 60%. Low-voltage transparent W-doped indium-zinc-oxide thin-film transistors gated by WOx-based electrolytes were self-assembled on glass substrates by one mask diffraction method. Enhancement mode operation with a large current on/off ratio of 4.7 × 106, a low subthreshold swing of 108 mV/decade, and a high field-effect mobility 42.6 cm2/V s was realized. Our results demonstrated that WOx-based proton conducting films were promising gate dielectric candidates for portable low-voltage oxide-based devices.

  17. Hole mobility modulation of solution-processed nickel oxide thin-film transistor based on high-k dielectric

    NASA Astrophysics Data System (ADS)

    Liu, Ao; Liu, Guoxia; Zhu, Huihui; Shin, Byoungchul; Fortunato, Elvira; Martins, Rodrigo; Shan, Fukai

    2016-06-01

    Solution-processed p-type oxide semiconductors have recently attracted increasing interests for the applications in low-cost optoelectronic devices and low-power consumption complementary metal-oxide-semiconductor circuits. In this work, p-type nickel oxide (NiOx) thin films were prepared using low-temperature solution process and integrated as the channel layer in thin-film transistors (TFTs). The electrical properties of NiOx TFTs, together with the characteristics of NiOx thin films, were systematically investigated as a function of annealing temperature. By introducing aqueous high-k aluminum oxide (Al2O3) gate dielectric, the electrical performance of NiOx TFT was improved significantly compared with those based on SiO2 dielectric. Particularly, the hole mobility was found to be 60 times enhancement, quantitatively from 0.07 to 4.4 cm2/V s, which is mainly beneficial from the high areal capacitance of the Al2O3 dielectric and high-quality NiOx/Al2O3 interface. This simple solution-based method for producing p-type oxide TFTs is promising for next-generation oxide-based electronic applications.

  18. Proton induced multilevel storage capability in self-assembled indium-zinc-oxide thin-film transistors

    NASA Astrophysics Data System (ADS)

    Guo, Li Qiang; Jin Wan, Chang; Qiang Zhu, Li; Wan, Qing

    2013-09-01

    Multilevel memory capability of self-assembled indium-zinc-oxide (IZO) electric-double-layer (EDL) thin-film transistors gated by nanogranular SiO2 proton conducting electrolytes is investigated. More than four distinct memory states are obtained by programming gate voltage. The observed multilevel storage behavior is mainly due to the controlled interfacial electrochemical doping of IZO channel by penetrated protons under programmed gate voltages. In addition, such IZO-based EDL transistor multilevel memory exhibits good characteristics of programming/erasing endurance and data retention. Such oxide-based EDL transistors with proton-induced multilevel memory behavior are interesting for low-cost memory and neuromorphic system applications after further properties and size optimization.

  19. Suppression of photo-bias induced instability for amorphous indium tungsten oxide thin film transistors with bi-layer structure

    NASA Astrophysics Data System (ADS)

    Liu, Po-Tsun; Chang, Chih-Hsiang; Chang, Chih-Jui

    2016-06-01

    This study investigates the instability induced by bias temperature illumination stress (NBTIS) for an amorphous indium-tungsten-oxide thin film transistor (a-IWO TFT) with SiO2 backchannel passivation layer (BPL). It is found that this electrical degradation phenomenon can be attributed to the generation of defect states during the BPL process, which deteriorates the photo-bias stability of a-IWO TFTs. A method proposed by adding an oxygen-rich a-IWO thin film upon the a-IWO active channel layer could effectively suppress the plasma damage to channel layer during BPL deposition process. The bi-layer a-IWO TFT structure with an oxygen-rich back channel exhibits superior electrical reliability of device under NBTIS.

  20. Combustion synthesized indium-tin-oxide (ITO) thin film for source/drain electrodes in all solution-processed oxide thin-film transistors

    NASA Astrophysics Data System (ADS)

    Tue, Phan Trong; Inoue, Satoshi; Takamura, Yuzuru; Shimoda, Tatsuya

    2016-06-01

    We report combustion solution synthesized (SCS) indium-tin-oxide (ITO) thin film, which is a well-known transparent conductive oxide, for source/drain (S/D) electrodes in solution-processed amorphous zirconium-indium-zinc-oxide TFT. A redox-based combustion synthetic approach is applied to ITO thin film using acetylacetone as a fuel and metal nitrate as oxidizer. The structural and electrical properties of SCS-ITO precursor solution and thin films were systematically investigated with changes in tin concentration, indium metal precursors, and annealing conditions such as temperature, time, and ambient. It was found that at optimal conditions the SCS-ITO thin film exhibited high crystalline quality, atomically smooth surface (RMS ~ 4.1 Å), and low electrical resistivity (4.2 × 10-4 Ω cm). The TFT using SCS-ITO film as the S/D electrodes showed excellent electrical properties with negligible hysteresis. The obtained "on/off" current ratio, subthreshold swing factor, subthreshold voltage, and field-effect mobility were 5 × 107, 0.43 V/decade, 0.7 V, and 2.1 cm2/V s, respectively. The performance and stability of the SCS-ITO TFT are comparable to those of the sputtered-ITO TFT, emphasizing that the SCS-ITO film is a promising candidate for totally solution-processed oxide TFTs.

  1. The influence of the SiO{sub 2} interlayer on transfer characteristic in tin oxide thin film transistor

    SciTech Connect

    Kim, Woong-Sun; Moon, Yeon-Keon; Kim, Kyung-Taek; Park, Jong-Wan

    2011-12-23

    In this article, we report the fabrication on SnO{sub 2} thin film transistors (TFTs) fabricated by DC sputtering system. SnO{sub 2} based TFTs have been reported previously, and all the TFTs operate depletion-mode, requiring the application of a gate voltage to turn it off. In contrast to previously reports, the SnO{sub 2} TFT reported herein operates as an enhancement-mode device, requiring the application of a gate voltage to turn the device on. Furthermore, we introduce an hafnium-tin oxide (HfSnO) semiconductor materials that have been developed for use as p-channel TFTs.

  2. High-Quality Solution-Processed Silicon Oxide Gate Dielectric Applied on Indium Oxide Based Thin-Film Transistors.

    PubMed

    Jaehnike, Felix; Pham, Duy Vu; Anselmann, Ralf; Bock, Claudia; Kunze, Ulrich

    2015-07-01

    A silicon oxide gate dielectric was synthesized by a facile sol-gel reaction and applied to solution-processed indium oxide based thin-film transistors (TFTs). The SiOx sol-gel was spin-coated on highly doped silicon substrates and converted to a dense dielectric film with a smooth surface at a maximum processing temperature of T = 350 °C. The synthesis was systematically improved, so that the solution-processed silicon oxide finally achieved comparable break downfield strength (7 MV/cm) and leakage current densities (<10 nA/cm(2) at 1 MV/cm) to thermally grown silicon dioxide (SiO2). The good quality of the dielectric layer was successfully proven in bottom-gate, bottom-contact metal oxide TFTs and compared to reference TFTs with thermally grown SiO2. Both transistor types have field-effect mobility values as high as 28 cm(2)/(Vs) with an on/off current ratio of 10(8), subthreshold swings of 0.30 and 0.37 V/dec, respectively, and a threshold voltage close to zero. The good device performance could be attributed to the smooth dielectric/semiconductor interface and low interface trap density. Thus, the sol-gel-derived SiO2 is a promising candidate for a high-quality dielectric layer on many substrates and high-performance large-area applications. PMID:26039187

  3. Fabrication of Amorphous Indium Gallium Zinc Oxide Thin Film Transistor by using Focused Ion Beam

    NASA Astrophysics Data System (ADS)

    Zhu, Wencong

    Compared with other transparent semiconductors, amorphous indium gallium zinc oxide (a-IGZO) has both good uniformity and high electron mobility, which make it as a good candidate for displays or large-scale transparent circuit. The goal of this research is to fabricate alpha-IGZO thin film transistor (TFT) with channel milled by focused ion beam (FIB). TFTs with different channel geometries can be achieved by applying different milling strategies, which facilitate modifying complex circuit. Technology Computer-Aided Design (TCAD) was also introduced to understand the effect of trapped charges on the device performance. The investigation of the trapped charge at IGZO/SiO2 interface was performed on the IGZO TFT on p-Silicon substrate with thermally grown SiO2 as dielectric. The subgap density-of-state model was used for the simulation, which includes conduction band-tail trap states and donor-like state in the subgap. The result shows that the de-trapping and donor-state ionization determine the interface trapped charge density at various gate biases. Simulation of IGZO TFT with FIB defined channel on the same substrate was also applied. The drain and source were connected intentionally during metal deposition and separated by FIB milling. Based on the simulation, the Ga ions in SiO2 introduced by the ion beam was drifted by gate bias and affects the saturation drain current. Both side channel and direct channel transparent IGZO TFTs were fabricated on the glass substrate with coated ITO. Higher ion energy (30 keV) was used to etch through the substrate between drain and source and form side channels at the corner of milled trench. Lower ion energy (16 keV) was applied to stop the milling inside IGZO thin film and direct channel between drain and source was created. Annealing after FIB milling removed the residual Ga ions and the devices show switch feature. Direct channel shows higher saturation drain current (~10-6 A) compared with side channel (~10-7 A) because

  4. Transparent Flexible Zinc-Indium-Tin Oxide Thin-Film Transistors Fabricated on Polyarylate Films

    NASA Astrophysics Data System (ADS)

    Cheong, Woo-Seok; Bak, Jun-Yong; Kim, Hong Seung

    2010-05-01

    Transparent flexible displays can be realized using active matrix organic light emitting device (AMOLED) with transparent electrodes on transparent plastic substrates. In this study, we developed low-temperature, high-performance [ZITO, ZnO:In2O3:SnO2=3:1:1 molar ratio] thin-film transistors (TFTs) on polyarylate films. After optimizing the sputtering condition, the ZITO TFT with an ITO electrode had a high mobility of 16.93 cm2 V-1 s-1, and an SS of 0.39, while the ZITO TFT with a ZTO:B electrode showed no hysteresis on sweeping, a mobility of 2.29 cm2 V-1 s-1 and an SS of 0.18.

  5. High-performance calcium-doped zinc oxide thin-film transistors fabricated on glass at low temperature

    NASA Astrophysics Data System (ADS)

    Yu, Wen; Han, Dedong; Cui, Guodong; Cong, Yingying; Dong, Junchen; Zhang, Xiaomi; Zhang, Xing; Wang, Yi; Zhang, Shengdong

    2016-04-01

    High-performance calcium-doped zinc oxide thin-film transistors (Ca-ZnO TFTs) have been successfully fabricated on transparent glass at low temperature by RF magnetron sputtering. To study the effects of calcium doping on zinc oxide thin-film transistors, the characteristics of Ca-ZnO TFTs and ZnO TFTs are compared and analyzed in detail from different perspectives, including electrical performance, surface morphology, and crystal structure of the material. The results suggest that the incorporation of calcium element can decrease the root-mean-square roughness of the material, suppress growth of a columnar structure, and improve device performance. The TFTs with Ca-ZnO active layer exhibit excellent electrical properties with the saturation mobility (μsat) of 147.1 cm2 V-1 s-1, threshold voltage (V t) of 2.91 V, subthreshold slope (SS) of 0.271 V/dec, and I on/I off ratio of 2.34 × 108. In addition, we also study the uniformity of the devices. The experimental results show that the Ca-ZnO TFTs possess good uniformity, which is important for large-area application.

  6. Metal-oxide thin-film transistor-based pH sensor with a silver nanowire top gate electrode

    NASA Astrophysics Data System (ADS)

    Yoo, Tae-Hee; Sang, Byoung-In; Wang, Byung-Yong; Lim, Dae-Soon; Kang, Hyun Wook; Choi, Won Kook; Lee, Young Tack; Oh, Young-Jei; Hwang, Do Kyung

    2016-04-01

    Amorphous InGaZnO (IGZO) metal-oxide-semiconductor thin-film transistors (TFTs) are one of the most promising technologies to replace amorphous and polycrystalline Si TFTs. Recently, TFT-based sensing platforms have been gaining significant interests. Here, we report on IGZO transistor-based pH sensors in aqueous medium. In order to achieve stable operation in aqueous environment and enhance sensitivity, we used Al2O3 grown by using atomic layer deposition (ALD) and a porous Ag nanowire (NW) mesh as the top gate dielectric and electrode layers, respectively. Such devices with a Ag NW mesh at the top gate electrode rapidly respond to the pH of solutions by shifting the turn-on voltage. Furthermore, the output voltage signals induced by the voltage shifts can be directly extracted by implantation of a resistive load inverter.

  7. Transparent Thin Film Transistors based on Pristine and Doped Indium Oxide Nanowires

    NASA Astrophysics Data System (ADS)

    Chen, Po-Chiang; Shen, Guozhen; Sukcharoenchoke, Saowalak; Zhou, Chongwu

    2009-03-01

    The key to the realization of transparent electronics is the development of transparent thin film transistors (TTFT) with good device performance, in terms of high device mobility, low temperature fabrication, and optical transparency. We present our work on the fabrication of high performance TTFTs using both pristine In2O3 nanowires and doped In2O3 nanowires. In2O3 nanowire TTFTs were made on glass and PET substrates with Al2O3 as gate insulator and ITO source/drain electrodes. These devices showed a transparency of about 80% and n-type transistor performance. The device characteristics exhibit a subthreshold slope of 0.2 V/dec, a current on/off ratio of 10^6, and a field-effect mobility of 514 cm^2V-1S-1. We also fabricated TTFTs wbuilt on Arsenic-doped In2O3 nanowires with a field-effect mobility of 1,183.8 cm^2V-1S-1 without any post-treatments. In addition, we integrated TTFTs with organic light emitting diode (OLED) to make an active matrix organic light emitting diode (AMOLED) display, and thus made an animation by controlling the OLED light output.

  8. Artificial semiconductor/insulator superlattice channel structure for high-performance oxide thin-film transistors

    PubMed Central

    Ahn, Cheol Hyoun; Senthil, Karuppanan; Cho, Hyung Koun; Lee, Sang Yeol

    2013-01-01

    High-performance thin-film transistors (TFTs) are the fundamental building blocks in realizing the potential applications of the next-generation displays. Atomically controlled superlattice structures are expected to induce advanced electric and optical performance due to two-dimensional electron gas system, resulting in high-electron mobility transistors. Here, we have utilized a semiconductor/insulator superlattice channel structure comprising of ZnO/Al2O3 layers to realize high-performance TFTs. The TFT with ZnO (5 nm)/Al2O3 (3.6 nm) superlattice channel structure exhibited high field effect mobility of 27.8 cm2/Vs, and threshold voltage shift of only < 0.5 V under positive/negative gate bias stress test during 2 hours. These properties showed extremely improved TFT performance, compared to ZnO TFTs. The enhanced field effect mobility and stability obtained for the superlattice TFT devices were explained on the basis of layer-by-layer growth mode, improved crystalline nature of the channel layers, and passivation effect of Al2O3 layers. PMID:24061388

  9. Physical/chemical properties of tin oxide thin film transistors prepared using plasma-enhanced atomic layer deposition

    SciTech Connect

    Lee, Byung Kook; Jung, Eunae; Kim, Seok Hwan; Moon, Dae Chul; Lee, Sun Sook; Park, Bo Keun; Hwang, Jin Ha; Chung, Taek-Mo; Kim, Chang Gyoun; An, Ki-Seok

    2012-10-15

    Thin film transistors (TFTs) with tin oxide films as the channel layer were fabricated by means of plasma enhanced atomic layer deposition (PE-ALD). The as-deposited tin oxide films show n-type conductivity and a nano-crystalline structure of SnO{sub 2}. Notwithstanding the relatively low deposition temperatures of 70, 100, and 130 °C, the bottom gate tin oxide TFTs show an on/off drain current ratio of 10{sup 6} while the device mobility values were increased from 2.31 cm{sup 2}/V s to 6.24 cm{sup 2}/V s upon increasing the deposition temperature of the tin oxide films.

  10. Transient laser annealing of zinc oxide nanoparticle inks to fabricate zinc oxide thin film transistors

    NASA Astrophysics Data System (ADS)

    Willemann, Michael

    Display technology, which relies exclusively on amorphous silicon as the active material for driver electronics, has reached multiple impasses that limit future progress. In order to deliver higher resolutions, higher refresh rates, new display technologies, and innovative form factors, driver electronics must transition to higher performance materials like amorphous oxide semiconductors (AOSs). Transient laser annealing offers an attractive means to maximize performance while minimizing thermal budget, making it compatible with flexible back plane materials and roll-to-roll processing. This research investigates the deposition and annealing of zinc oxide nanoparticle inks to form fully densified crystalline and amorphous zinc oxide films. Processing routes for nanoparticle annealing, including ligand removal, calcining, and excimer pulse laser sintering on the nanosecond time scale, will be introduced that minimize defect formation and suppress the anomalous n-conductivity which is a major challenge to zinc oxide processing. Resistivities as high as 6 x 107 O-cm have been demonstrated. Laser processing on longer millisecond time scales can control defect formation to produce ZnO films without extrinsic doping which have low resistivity for intrinsic oxides, in the range of 10-1 - 10-2 O-cm. Finally, a viable process for the production of backgated ZnO transistors with promising characteristics is presented and the future implications for AOSs and transient thermal processing will be discussed.

  11. High stability mechanisms of quinary indium gallium zinc aluminum oxide multicomponent oxide films and thin film transistors

    SciTech Connect

    Lee, Ching-Ting Lin, Yung-Hao; Lin, Jhong-Ham

    2015-01-28

    Quinary indium gallium zinc aluminum oxide (IGZAO) multicomponent oxide films were deposited using indium gallium zinc oxide (IGZO) target and Al target by radio frequency magnetron cosputtering system. An extra carrier transport pathway could be provided by the 3 s orbitals of Al cations to improve the electrical properties of the IGZO films, and the oxygen instability could be stabilized by the strong Al-O bonds in the IGZAO films. The electron concentration change and the electron mobility change of the IGZAO films for aging time of 10 days under an air environment at 40 °C and 75% humidity were 20.1% and 2.4%, respectively. The experimental results verified the performance stability of the IGZAO films. Compared with the thin film transistors (TFTs) using conventional IGZO channel layer, in conducting the stability of TFTs with IGZAO channel layer, the transconductance g{sub m} change, threshold voltage V{sub T} change, and the subthreshold swing S value change under the same aging condition were improved to 7.9%, 10.5%, and 14.8%, respectively. Furthermore, the stable performances of the IGZAO TFTs were also verified by the positive gate bias stress. In this research, the quinary IGZAO multicomponent oxide films and that applied in TFTs were the first studied in the literature.

  12. High stability mechanisms of quinary indium gallium zinc aluminum oxide multicomponent oxide films and thin film transistors

    NASA Astrophysics Data System (ADS)

    Lee, Ching-Ting; Lin, Yung-Hao; Lin, Jhong-Ham

    2015-01-01

    Quinary indium gallium zinc aluminum oxide (IGZAO) multicomponent oxide films were deposited using indium gallium zinc oxide (IGZO) target and Al target by radio frequency magnetron cosputtering system. An extra carrier transport pathway could be provided by the 3 s orbitals of Al cations to improve the electrical properties of the IGZO films, and the oxygen instability could be stabilized by the strong Al-O bonds in the IGZAO films. The electron concentration change and the electron mobility change of the IGZAO films for aging time of 10 days under an air environment at 40 °C and 75% humidity were 20.1% and 2.4%, respectively. The experimental results verified the performance stability of the IGZAO films. Compared with the thin film transistors (TFTs) using conventional IGZO channel layer, in conducting the stability of TFTs with IGZAO channel layer, the transconductance gm change, threshold voltage VT change, and the subthreshold swing S value change under the same aging condition were improved to 7.9%, 10.5%, and 14.8%, respectively. Furthermore, the stable performances of the IGZAO TFTs were also verified by the positive gate bias stress. In this research, the quinary IGZAO multicomponent oxide films and that applied in TFTs were the first studied in the literature.

  13. Toward Active-Matrix Lab-On-A-Chip: Programmable Electrofluidic control Enaled by Arrayed Oxide Thin Film Transistors

    SciTech Connect

    Noh, Joo Hyon; Noh, Jiyong; Kreit, Eric; Heikenfeld, Jason; Rack, Philip D

    2012-01-01

    Agile micro- and nano-fluidic control is critical to numerous life science and chemical science synthesis as well as kinetic and thermodynamic studies. To this end, we have demonstrated the use of thin film transistor arrays as an active matrix addressing method to control an electrofluidic array. Because the active matrix method minimizes the number of control lines necessary (m + n lines for the m x n element array), the active matrix addressing method integrated with an electrofluidic platform can be a significant breakthrough for complex electrofluidic arrays (increased size or resolution) with enhanced function, agility and programmability. An amorphous indium gallium zinc oxide (a-IGZO) semiconductor active layer is used because of its high mobility of 1-15 cm{sup 2} V{sup -1} s{sup -1}, low-temperature processing and transparency for potential spectroscopy and imaging. Several electrofluidic functionalities are demonstrated using a simple 2 x 5 electrode array connected to a 2 x 5 IGZO thin film transistor array with the semiconductor channel width of 50 {mu}m and mobility of 6.3 cm{sup 2} V{sup -1} s{sup -1}. Additionally, using the TFT device characteristics, active matrix addressing schemes are discussed as the geometry of the electrode array can be tailored to act as a storage capacitor element. Finally, requisite material and device parameters are discussed in context with a VGA scale active matrix addressed electrofluidic platform.

  14. Effect of Ta addition of co-sputtered amorphous tantalum indium zinc oxide thin film transistors with bias stability.

    PubMed

    Son, Dae-Ho; Kim, Dae-Hwan; Park, Si-Nae; Sung, Shi-Joon; Kang, Jin-Kyu

    2014-11-01

    In this work, we have fabricated thin film transistors (TFTs) using amorphous tantalum indium zinc oxide (a-TaInZnO) channels by the co-sputtering process. The effects of incorporating tantalum on the InZnO material were investigated using Hall-effect measurement results, and electrical characteristics. We also found that the carrier densities of thin films and the transistor on-off currents were greatly influenced by the composition of tantalum addition. Ta ions have strong affinity to oxygen and so suppress the formation of free electron carriers inthin films; they play an important role in enhancing the electrical characteristic due to their high oxygen bonding ability. The electrical characteristics of the optimized TFTs shows a field effect mobility of 3.67 cm2 V(-1) s(-1), a threshold voltage of 1.28 V, an on/off ratio of 1.1 x 10(8), and a subthreshold swing of 480 mV/dec. Under gate bias stress conditions, the TaInZnO TFTs showed lower shift in threshold voltage shifts. PMID:25958492

  15. Electronic Structure of Low-Temperature Solution-Processed Amorphous Metal Oxide Semiconductors for Thin-Film Transistor Applications

    PubMed Central

    Socratous, Josephine; Banger, Kulbinder K; Vaynzof, Yana; Sadhanala, Aditya; Brown, Adam D; Sepe, Alessandro; Steiner, Ullrich; Sirringhaus, Henning

    2015-01-01

    The electronic structure of low temperature, solution-processed indium–zinc oxide thin-film transistors is complex and remains insufficiently understood. As commonly observed, high device performance with mobility >1 cm2 V−1 s−1 is achievable after annealing in air above typically 250 °C but performance decreases rapidly when annealing temperatures ≤200 °C are used. Here, the electronic structure of low temperature, solution-processed oxide thin films as a function of annealing temperature and environment using a combination of X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, and photothermal deflection spectroscopy is investigated. The drop-off in performance at temperatures ≤200 °C to incomplete conversion of metal hydroxide species into the fully coordinated oxide is attributed. The effect of an additional vacuum annealing step, which is beneficial if performed for short times at low temperatures, but leads to catastrophic device failure if performed at too high temperatures or for too long is also investigated. Evidence is found that during vacuum annealing, the workfunction increases and a large concentration of sub-bandgap defect states (re)appears. These results demonstrate that good devices can only be achieved in low temperature, solution-processed oxides if a significant concentration of acceptor states below the conduction band minimum is compensated or passivated by shallow hydrogen and oxygen vacancy-induced donor levels. PMID:26190964

  16. Water-Mediated Photochemical Treatments for Low-Temperature Passivation of Metal-Oxide Thin-Film Transistors.

    PubMed

    Heo, Jae Sang; Jo, Jeong-Wan; Kang, Jingu; Jeong, Chan-Yong; Jeong, Hu Young; Kim, Sung Kyu; Kim, Kwanpyo; Kwon, Hyuck-In; Kim, Jaekyun; Kim, Yong-Hoon; Kim, Myung-Gil; Park, Sung Kyu

    2016-04-27

    The low-temperature electrical passivation of an amorphous oxide semiconductor (AOS) thin-film transistor (TFT) is achieved by a deep ultraviolet (DUV) light irradiation-water treatment-DUV irradiation (DWD) method. The water treatment of the first DUV-annealed amorphous indium-gallium-zinc-oxide (a-IGZO) thin film is likely to induce the preferred adsorption of water molecules at the oxygen vacancies and leads to subsequent hydroxide formation in the bulk a-IGZO films. Although the water treatment initially degraded the electrical performance of the a-IGZO TFTs, the second DUV irradiation on the water-treated devices may enable a more complete metal-oxygen-metal lattice formation while maintaining low oxygen vacancies in the oxide films. Overall, the stable and dense metal-oxygen-metal (M-O-M) network formation could be easily achieved at low temperatures (below 150 °C). The successful passivation of structural imperfections in the a-IGZO TFTs, such as hydroxyl group (OH-) and oxygen vacancies, mainly results in the enhanced electrical performances of the DWD-processed a-IGZO TFTs (on/off current ratio of 8.65 × 10(9), subthreshold slope of 0.16 V/decade, an average mobility of >6.94 cm(2) V(-1) s(-1), and a bias stability of ΔVTH < 2.5 V), which show more than a 30% improvement over the simple DUV-treated a-IGZO TFTs. PMID:27035796

  17. Effects of Ta Addition Through Co-Sputtering on the Electrical Characteristics of Indium Tin Oxide Thin Film Transistors.

    PubMed

    Park, Si-Nae; Son, Dae-Ho; Sung, Shi-Joon; Kang, Jin-Kyu; Kim, Dae-Hwan

    2015-01-01

    We have investigated the effects of adding (Ta) ions to InSnO thin films by co-sputtering on the performance of InSnO thin film transistors (TFTs). TaInSnO TFTs exhibited significantly lower off currents and higher on/off current ratios. Ta ions, owing to their strong affinity to oxygen suppress the formation of free electron carriers in thin films; and hence, play an important role in enhancing the electrical characteristics of the TFTs. The optimized TaInSnO TFTs showed high on/off ratios and low subthreshold swings. PMID:26328366

  18. Photoresist-Free Fully Self-Patterned Transparent Amorphous Oxide Thin-Film Transistors Obtained by Sol-Gel Process

    PubMed Central

    Lim, Hyun Soo; Rim, You Seung; Kim, Hyun Jae

    2014-01-01

    We demonstrated self-patterned solution-processed amorphous oxide semiconductor thin-film transistors (TFTs) using photosensitive sol-gels. The photosensitive sol-gels were synthesized by adding β-diketone compounds, i.e., benzoylacetone and acetylacetone, to sol-gels. The chemically modified photosensitive sol-gels showed a high optical absorption at specific wavelengths due to the formation of metal chelate bonds. Photoreactions of the modified solutions enabled a photoresist-free process. Moreover, Zn–Sn–O with a high Sn ratio, which is hard to wet-etch using conventional photolithography due to its chemical durability, was easily patterned via the self-patterning process. Finally, we fabricated a solution-processed oxide TFT that included fully self-patterned electrodes and an active layer. PMID:24686314

  19. High-density carrier-accumulated and electrically stable oxide thin-film transistors from ion-gel gate dielectric.

    PubMed

    Fujii, Mami N; Ishikawa, Yasuaki; Miwa, Kazumoto; Okada, Hiromi; Uraoka, Yukiharu; Ono, Shimpei

    2015-01-01

    The use of indium-gallium-zinc oxide (IGZO) has paved the way for high-resolution uniform displays or integrated circuits with transparent and flexible devices. However, achieving highly reliable devices that use IGZO for low-temperature processes remains a technological challenge. We propose the use of IGZO thin-film transistors (TFTs) with an ionic-liquid gate dielectric in order to achieve high-density carrier-accumulated IGZO TFTs with high reliability, and we discuss a distinctive mechanism for the degradation of this organic-inorganic hybrid device under long-term electrical stress. Our results demonstrated that an ionic liquid or gel gate dielectric provides highly reliable and low-voltage operation with IGZO TFTs. Furthermore, high-density carrier accumulation helps improve the TFT characteristics and reliability, and it is highly relevant to the electronic phase control of oxide materials and the degradation mechanism for organic-inorganic hybrid devices. PMID:26677773

  20. High-density carrier-accumulated and electrically stable oxide thin-film transistors from ion-gel gate dielectric

    NASA Astrophysics Data System (ADS)

    Fujii, Mami N.; Ishikawa, Yasuaki; Miwa, Kazumoto; Okada, Hiromi; Uraoka, Yukiharu; Ono, Shimpei

    2015-12-01

    The use of indium-gallium-zinc oxide (IGZO) has paved the way for high-resolution uniform displays or integrated circuits with transparent and flexible devices. However, achieving highly reliable devices that use IGZO for low-temperature processes remains a technological challenge. We propose the use of IGZO thin-film transistors (TFTs) with an ionic-liquid gate dielectric in order to achieve high-density carrier-accumulated IGZO TFTs with high reliability, and we discuss a distinctive mechanism for the degradation of this organic-inorganic hybrid device under long-term electrical stress. Our results demonstrated that an ionic liquid or gel gate dielectric provides highly reliable and low-voltage operation with IGZO TFTs. Furthermore, high-density carrier accumulation helps improve the TFT characteristics and reliability, and it is highly relevant to the electronic phase control of oxide materials and the degradation mechanism for organic-inorganic hybrid devices.

  1. High-density carrier-accumulated and electrically stable oxide thin-film transistors from ion-gel gate dielectric

    PubMed Central

    Fujii, Mami N.; Ishikawa, Yasuaki; Miwa, Kazumoto; Okada, Hiromi; Uraoka, Yukiharu; Ono, Shimpei

    2015-01-01

    The use of indium–gallium–zinc oxide (IGZO) has paved the way for high-resolution uniform displays or integrated circuits with transparent and flexible devices. However, achieving highly reliable devices that use IGZO for low-temperature processes remains a technological challenge. We propose the use of IGZO thin-film transistors (TFTs) with an ionic-liquid gate dielectric in order to achieve high-density carrier-accumulated IGZO TFTs with high reliability, and we discuss a distinctive mechanism for the degradation of this organic–inorganic hybrid device under long-term electrical stress. Our results demonstrated that an ionic liquid or gel gate dielectric provides highly reliable and low-voltage operation with IGZO TFTs. Furthermore, high-density carrier accumulation helps improve the TFT characteristics and reliability, and it is highly relevant to the electronic phase control of oxide materials and the degradation mechanism for organic–inorganic hybrid devices. PMID:26677773

  2. Solution processed lanthanum aluminate gate dielectrics for use in metal oxide-based thin film transistors

    SciTech Connect

    Esro, M.; Adamopoulos, G.; Mazzocco, R.; Kolosov, O.; Krier, A.; Vourlias, G.; Milne, W. I.

    2015-05-18

    We report on ZnO-based thin-film transistors (TFTs) employing lanthanum aluminate gate dielectrics (La{sub x}Al{sub 1−x}O{sub y}) grown by spray pyrolysis in ambient atmosphere at 440 °C. The structural, electronic, optical, morphological, and electrical properties of the La{sub x}Al{sub 1−x}O{sub y} films and devices as a function of the lanthanum to aluminium atomic ratio were investigated using a wide range of characterization techniques such as UV-visible absorption spectroscopy, impedance spectroscopy, spectroscopic ellipsometry, atomic force microscopy, x-ray diffraction, and field-effect measurements. As-deposited LaAlO{sub y} dielectrics exhibit a wide band gap (∼6.18 eV), high dielectric constant (k ∼ 16), low roughness (∼1.9 nm), and very low leakage currents (<3 nA/cm{sup 2}). TFTs employing solution processed LaAlO{sub y} gate dielectrics and ZnO semiconducting channels exhibit excellent electron transport characteristics with hysteresis-free operation, low operation voltages (∼10 V), high on/off current modulation ratio of >10{sup 6}, subthreshold swing of ∼650 mV dec{sup −1}, and electron mobility of ∼12 cm{sup 2} V{sup −1} s{sup −1}.

  3. Fully Solution-Processed and Foldable Metal-Oxide Thin-Film Transistor.

    PubMed

    Lee, Su Jeong; Ko, Jieun; Nam, Ki-Ho; Kim, Taehee; Lee, Sang Hoon; Kim, Jung Han; Chae, Gee Sung; Han, Hs; Kim, Youn Sang; Myoung, Jae-Min

    2016-05-25

    Flexible and foldable thin-film transistors (TFTs) have been widely studied with the objective of achieving high-performance and low-cost flexible TFTs for next-generation displays. In this study, we introduced the fabrication of foldable TFT devices with excellent mechanical stability, high transparency, and high performance by a fully solution process including PI, YOx, In2O3, SWCNTs, IL-PVP, and Ag NWs. The fabricated fully solution-processed TFTs showed a higher transmittance above 86% in the visible range. Additionally, the charge-carrier mobility and Ion/Ioff ratio of them were 7.12 ± 0.43 cm(2)/V·s and 5.53 ± 0.82 × 10(5) at a 3 V low voltage operating, respectively. In particular, the fully solution-processed TFTs showed good electrical characteristics under tensile strain with 1 mm bending and even extreme folding up to a strain of 26.79%. Due to the good compatibility of each component layer, it maintained the charge-carrier mobility over 79% of initial devices after 5,000 cycles of folding test in both the parallel and perpendicular direction with a bending radius of 1 mm. These results show the potential of the fully solution-processed TFTs as flexible TFTs for a next generation devices because of the robust mechanical flexibility, transparency, and high electrical performance of it. PMID:27120010

  4. Solution processed lanthanum aluminate gate dielectrics for use in metal oxide-based thin film transistors

    NASA Astrophysics Data System (ADS)

    Esro, M.; Mazzocco, R.; Vourlias, G.; Kolosov, O.; Krier, A.; Milne, W. I.; Adamopoulos, G.

    2015-05-01

    We report on ZnO-based thin-film transistors (TFTs) employing lanthanum aluminate gate dielectrics (LaxAl1-xOy) grown by spray pyrolysis in ambient atmosphere at 440 °C. The structural, electronic, optical, morphological, and electrical properties of the LaxAl1-xOy films and devices as a function of the lanthanum to aluminium atomic ratio were investigated using a wide range of characterization techniques such as UV-visible absorption spectroscopy, impedance spectroscopy, spectroscopic ellipsometry, atomic force microscopy, x-ray diffraction, and field-effect measurements. As-deposited LaAlOy dielectrics exhibit a wide band gap (˜6.18 eV), high dielectric constant (k ˜ 16), low roughness (˜1.9 nm), and very low leakage currents (<3 nA/cm2). TFTs employing solution processed LaAlOy gate dielectrics and ZnO semiconducting channels exhibit excellent electron transport characteristics with hysteresis-free operation, low operation voltages (˜10 V), high on/off current modulation ratio of >106, subthreshold swing of ˜650 mV dec-1, and electron mobility of ˜12 cm2 V-1 s-1.

  5. Low-temperature spray-deposited indium oxide for flexible thin-film transistors and integrated circuits

    SciTech Connect

    Petti, Luisa; Faber, Hendrik; Anthopoulos, Thomas D.; Münzenrieder, Niko; Cantarella, Giuseppe; Tröster, Gerhard; Patsalas, Panos A.

    2015-03-02

    Indium oxide (In{sub 2}O{sub 3}) films were deposited by ultrasonic spray pyrolysis in ambient air and incorporated into bottom-gate coplanar and staggered thin-film transistors. As-fabricated devices exhibited electron-transporting characteristics with mobility values of 1 cm{sup 2}V{sup −1}s{sup −1} and 16 cm{sup 2}V{sup −1}s{sup −1} for coplanar and staggered architectures, respectively. Integration of In{sub 2}O{sub 3} transistors enabled realization of unipolar inverters with high gain (5.3 V/V) and low-voltage operation. The low temperature deposition (≤250 °C) of In{sub 2}O{sub 3} also allowed transistor fabrication on free-standing 50 μm-thick polyimide foils. The resulting flexible In{sub 2}O{sub 3} transistors exhibit good characteristics and remain fully functional even when bent to tensile radii of 4 mm.

  6. The influence of interfacial defects on fast charge trapping in nanocrystalline oxide-semiconductor thin film transistors

    NASA Astrophysics Data System (ADS)

    Kim, Taeho; Hur, Jihyun; Jeon, Sanghun

    2016-05-01

    Defects in oxide semiconductors not only influence the initial device performance but also affect device reliability. The front channel is the major carrier transport region during the transistor turn-on stage, therefore an understanding of defects located in the vicinity of the interface is very important. In this study, we investigated the dynamics of charge transport in a nanocrystalline hafnium-indium-zinc-oxide thin-film transistor (TFT) by short pulse I-V, transient current and 1/f noise measurement methods. We found that the fast charging behavior of the tested device stems from defects located in both the front channel and the interface, following a multi-trapping mechanism. We found that a silicon-nitride stacked hafnium-indium-zinc-oxide TFT is vulnerable to interfacial charge trapping compared with silicon-oxide counterpart, causing significant mobility degradation and threshold voltage instability. The 1/f noise measurement data indicate that the carrier transport in a silicon-nitride stacked TFT device is governed by trapping/de-trapping processes via defects in the interface, while the silicon-oxide device follows the mobility fluctuation model.

  7. Electrothermal Annealing (ETA) Method to Enhance the Electrical Performance of Amorphous-Oxide-Semiconductor (AOS) Thin-Film Transistors (TFTs).

    PubMed

    Kim, Choong-Ki; Kim, Eungtaek; Lee, Myung Keun; Park, Jun-Young; Seol, Myeong-Lok; Bae, Hagyoul; Bang, Tewook; Jeon, Seung-Bae; Jun, Sungwoo; Park, Sang-Hee K; Choi, Kyung Cheol; Choi, Yang-Kyu

    2016-09-14

    An electro-thermal annealing (ETA) method, which uses an electrical pulse of less than 100 ns, was developed to improve the electrical performance of array-level amorphous-oxide-semiconductor (AOS) thin-film transistors (TFTs). The practicality of the ETA method was experimentally demonstrated with transparent amorphous In-Ga-Zn-O (a-IGZO) TFTs. The overall electrical performance metrics were boosted by the proposed method: up to 205% for the trans-conductance (gm), 158% for the linear current (Ilinear), and 206% for the subthreshold swing (SS). The performance enhancement were interpreted by X-ray photoelectron microscopy (XPS), showing a reduction of oxygen vacancies in a-IGZO after the ETA. Furthermore, by virtue of the extremely short operation time (80 ns) of ETA, which neither provokes a delay of the mandatory TFTs operation such as addressing operation for the display refresh nor demands extra physical treatment, the semipermanent use of displays can be realized. PMID:27552134

  8. Recovery from ultraviolet-induced threshold voltage shift in indium gallium zinc oxide thin film transistors by positive gate bias

    SciTech Connect

    Liu, P.; Chen, T. P.; Li, X. D.; Wong, J. I.; Liu, Z.; Liu, Y.; Leong, K. C.

    2013-11-11

    The effect of short-duration ultraviolet (UV) exposure on the threshold voltage (V{sub th}) of amorphous indium gallium zinc oxide thin film transistors (TFTs) and its recovery characteristics were investigated. The V{sub th} exhibited a significant negative shift after UV exposure. The V{sub th} instability caused by UV illumination is attributed to the positive charge trapping in the dielectric layer and/or at the channel/dielectric interface. The illuminated devices showed a slow recovery in threshold voltage without external bias. However, an instant recovery can be achieved by the application of positive gate pulses, which is due to the elimination of the positive trapped charges as a result of the presence of a large amount of field-induced electrons in the interface region.

  9. Defect generation in amorphous-indium-gallium-zinc-oxide thin-film transistors by positive bias stress at elevated temperature

    SciTech Connect

    Um, Jae Gwang; Mativenga, Mallory; Jang, Jin; Migliorato, Piero

    2014-04-07

    We report on the generation and characterization of a hump in the transfer characteristics of amorphous indium gallium zinc-oxide thin-film transistors by positive bias temperature stress. The hump depends strongly on the gate bias stress at 100 °C. Due to the hump, the positive shift of the transfer characteristic in deep depletion is always smaller that in accumulation. Since, the latter shift is twice the former, with very good correlation, we conclude that the effect is due to creation of a double acceptor, likely to be a cation vacancy. Our results indicate that these defects are located near the gate insulator/active layer interface, rather than in the bulk. Migration of donor defects from the interface towards the bulk may also occur under PBST at 100 °C.

  10. Electrical stress-induced instability of amorphous indium-gallium-zinc oxide thin-film transistors under bipolar ac stress

    SciTech Connect

    Lee, Sangwon; Jeon, Kichan; Park, Jun-Hyun; Kim, Sungchul; Kong, Dongsik; Kim, Dong Myong; Kim, Dae Hwan; Kim, Sangwook; Kim, Sunil; Hur, Jihyun; Park, Jae Chul; Song, Ihun; Kim, Chang Jung; Park, Youngsoo; Jung, U-In

    2009-09-28

    Bipolar ac stress-induced instability of amorphous indium-gallium-zinc oxide (a-IGZO) thin-film transistors is comparatively investigated with that under a positive dc gate bias stress. While the positive dc gate bias stress-induced threshold voltage shift ({delta}V{sub T}) is caused by the charge trapping into the interface/gate dielectric as reported in previous works, the dominant mechanism of the ac stress-induced {delta}V{sub T} is observed to be due to the increase in the acceptorlike deep states of the density of states (DOS) in the a-IGZO active layer. Furthermore, it is found that the variation of deep states in the DOS makes a parallel shift in the I{sub DS}-V{sub GS} curve with an insignificant change in the subthreshold slope, as well as the deformation of the C{sub G}-V{sub G} curves.

  11. Enhanced stability against bias-stress of metal-oxide thin film transistors deposited at elevated temperatures

    NASA Astrophysics Data System (ADS)

    Fakhri, M.; Görrn, P.; Weimann, T.; Hinze, P.; Riedl, T.

    2011-09-01

    Transparent zinc-tin-oxide (ZTO) thin film transistors (TFTs) have been prepared by DC magnetron sputtering. Compared to reference devices with a channel deposited at room temperature and subsequently annealing at 400 °C, a substantially enhanced stability against bias stress is evidenced for devices with in-situ substrate heating during deposition (400 °C). A reduced density of sub-gap defect states in TFT channels prepared with in-situ substrate heating is found. Concomitantly, a reduced sensitivity to the adsorption of ambient gases is evidenced for the in-situ heated devices. This finding is of particular importance for an application as driver electronics for organic light emitting diode displays.

  12. Top-gate zinc tin oxide thin-film transistors with high bias and environmental stress stability

    NASA Astrophysics Data System (ADS)

    Fakhri, M.; Theisen, M.; Behrendt, A.; Görrn, P.; Riedl, T.

    2014-06-01

    Top gated metal-oxide thin-film transistors (TFTs) provide two benefits compared to their conventional bottom-gate counterparts: (i) The gate dielectric may concomitantly serve as encapsulation layer for the TFT channel. (ii) Damage of the dielectric due to high-energetic particles during channel deposition can be avoided. In our work, the top-gate dielectric is prepared by ozone based atomic layer deposition at low temperatures. For ultra-low gas permeation rates, we introduce nano-laminates of Al2O3/ZrO2 as dielectrics. The resulting TFTs show a superior environmental stability even at elevated temperatures. Their outstanding stability vs. bias stress is benchmarked against bottom-gate devices with encapsulation.

  13. Flexible nickel-doped zinc oxide thin-film transistors fabricated on plastic substrates at low temperature

    NASA Astrophysics Data System (ADS)

    Huang, Lingling; Han, Dedong; Chen, Zhuofa; Cong, Yingying; Wu, Jing; Zhao, Nannan; Dong, Junchen; Zhao, Feilong; Liu, Lifeng; Zhang, Shengdong; Zhang, Xing; Wang, Yi

    2015-04-01

    High-performance nickel (Ni)-doped zinc oxide thin-film transistors (NZO TFTs) have been successfully fabricated on transparent flexible plastic substrates at a low temperature. The effect of different oxygen partial pressures during channel deposition on the electrical properties of NZO TFTs was studied to improve the device performance. We found that the oxygen partial pressure during channel deposition has a significant influence on the performance of NZO TFTs. Finally, it was demonstrated that a NZO film with 100% Ar sputtering gas during channel deposition exhibited the best electrical properties, with a drain current on/off ratio of 108, a positive threshold voltage of 2.59 V, a subthreshold swing of 233 mV/decade, and a saturation mobility of 118.9 cm2·V-1·s-1. The results show that Ni-doped ZnO is a promising candidate for flexible fully transparent displays.

  14. Top-gate zinc tin oxide thin-film transistors with high bias and environmental stress stability

    SciTech Connect

    Fakhri, M.; Theisen, M.; Behrendt, A.; Görrn, P.; Riedl, T.

    2014-06-23

    Top gated metal-oxide thin-film transistors (TFTs) provide two benefits compared to their conventional bottom-gate counterparts: (i) The gate dielectric may concomitantly serve as encapsulation layer for the TFT channel. (ii) Damage of the dielectric due to high-energetic particles during channel deposition can be avoided. In our work, the top-gate dielectric is prepared by ozone based atomic layer deposition at low temperatures. For ultra-low gas permeation rates, we introduce nano-laminates of Al{sub 2}O{sub 3}/ZrO{sub 2} as dielectrics. The resulting TFTs show a superior environmental stability even at elevated temperatures. Their outstanding stability vs. bias stress is benchmarked against bottom-gate devices with encapsulation.

  15. Light-induced hysteresis and recovery behaviors in photochemically activated solution-processed metal-oxide thin-film transistors

    SciTech Connect

    Jo, Jeong-Wan; Park, Sung Kyu E-mail: skpark@cau.ac.kr; Kim, Yong-Hoon E-mail: skpark@cau.ac.kr

    2014-07-28

    In this report, photo-induced hysteresis, threshold voltage (V{sub T}) shift, and recovery behaviors in photochemically activated solution-processed indium-gallium-zinc oxide (IGZO) thin-film transistors (TFTs) are investigated. It was observed that a white light illumination caused negative V{sub T} shift along with creation of clockwise hysteresis in electrical characteristics which can be attributed to photo-generated doubly ionized oxygen vacancies at the semiconductor/gate dielectric interface. More importantly, the photochemically activated IGZO TFTs showed much reduced overall V{sub T} shift compared to thermally annealed TFTs. Reduced number of donor-like interface states creation under light illumination and more facile neutralization of ionized oxygen vacancies by electron capture under positive gate potential are claimed to be the origin of the less V{sub T} shift in photochemically activated TFTs.

  16. Metal-induced crystallization of amorphous zinc tin oxide semiconductors for high mobility thin-film transistors

    NASA Astrophysics Data System (ADS)

    Hwang, Ah Young; Kim, Sang Tae; Ji, Hyuk; Shin, Yeonwoo; Jeong, Jae Kyeong

    2016-04-01

    Transition tantalum induced crystallization of amorphous zinc tin oxide (a-ZTO) was observed at low temperature annealing of 300 °C. Thin-film transistors (TFTs) with an a-ZTO channel layer exhibited a reasonable field-effect mobility of 12.4 cm2/V s, subthreshold swing (SS) of 0.39 V/decade, threshold voltage (VTH) of 1.5 V, and ION/OFF ratio of ˜107. A significant improvement in the field-effect mobility (up to ˜33.5 cm2/V s) was achieved for crystallized ZTO TFTs: this improvement was accomplished without compromising the SS, VTH, or ION/OFF ratio due to the presence of a highly ordered microstructure.

  17. Facile Routes To Improve Performance of Solution-Processed Amorphous Metal Oxide Thin Film Transistors by Water Vapor Annealing.

    PubMed

    Park, Won-Tae; Son, Inyoung; Park, Hyun-Woo; Chung, Kwun-Bum; Xu, Yong; Lee, Taegweon; Noh, Yong-Young

    2015-06-24

    Here, we report on a simple and high-rate oxidization method for producing solution-based compound mixtures of indium zinc oxide (IZO) and indium gallium zinc oxide (IGZO) metal-oxide semiconductors (MOS) for thin-film transistor (TFT) applications. One of the issues for solution-based MOS fabrication is how to sufficiently oxidize the precursor in order to achieve high performance. As the oxidation rate of solution processing is lower than vacuum-based deposition such as sputtering, devices using solution-processed MOS exhibit relatively poorer performance. Therefore, we propose a method to prepare the metal-oxide precursor upon exposure to saturated water vapor in a closed volume for increasing the oxidization efficiency without requiring additional oxidizing agent. We found that the hydroxide rate of the MOS film exposed to water vapor is lower than when unexposed (≤18%). Hence, we successfully fabricated oxide TFTs with high electron mobility (27.9 cm(2)/V·s) and established a rapid process (annealing at 400 °C for 5 min) that is much shorter than the conventional as-deposited long-duration annealing (at 400 °C for 1 h) whose corresponding mobility is even lower (19.2 cm(2)/V·s). PMID:26043206

  18. Thin film three-dimensional topological insulator metal-oxide-semiconductor field-effect-transistors: A candidate for sub-10 nm devices

    SciTech Connect

    Akhavan, N. D. Jolley, G.; Umana-Membreno, G. A.; Antoszewski, J.; Faraone, L.

    2014-08-28

    Three-dimensional (3D) topological insulators (TI) are a new state of quantum matter in which surface states reside in the bulk insulating energy bandgap and are protected by time-reversal symmetry. It is possible to create an energy bandgap as a consequence of the interaction between the conduction band and valence band surface states from the opposite surfaces of a TI thin film, and the width of the bandgap can be controlled by the thin film thickness. The formation of an energy bandgap raises the possibility of thin-film TI-based metal-oxide-semiconductor field-effect-transistors (MOSFETs). In this paper, we explore the performance of MOSFETs based on thin film 3D-TI structures by employing quantum ballistic transport simulations using the effective continuous Hamiltonian with fitting parameters extracted from ab-initio calculations. We demonstrate that thin film transistors based on a 3D-TI structure provide similar electrical characteristics compared to a Si-MOSFET for gate lengths down to 10 nm. Thus, such a device can be a potential candidate to replace Si-based MOSFETs in the sub-10 nm regime.

  19. Temperature-dependent bias-stress-induced electrical instability of amorphous indium-gallium-zinc-oxide thin-film transistors

    NASA Astrophysics Data System (ADS)

    Qian, Hui-Min; Yu, Guang; Lu, Hai; Wu, Chen-Fei; Tang, Lan-Feng; Zhou, Dong; Ren, Fang-Fang; Zhang, Rong; Zheng, You-Liao; Huang, Xiao-Ming

    2015-07-01

    The time and temperature dependence of threshold voltage shift under positive-bias stress (PBS) and the following recovery process are investigated in amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistors. It is found that the time dependence of threshold voltage shift can be well described by a stretched exponential equation in which the time constant τ is found to be temperature dependent. Based on Arrhenius plots, an average effective energy barrier Eτstress = 0.72 eV for the PBS process and an average effective energy barrier Eτrecovery = 0.58 eV for the recovery process are extracted respectively. A charge trapping/detrapping model is used to explain the threshold voltage shift in both the PBS and the recovery process. The influence of gate bias stress on transistor performance is one of the most critical issues for practical device development. Project supported by the National Basic Research Program of China (Grant Nos. 2011CB301900 and 2011CB922100) and the Priority Academic Program Development of Jiangsu Higher Education Institutions, China

  20. 3.4-Inch Quarter High Definition Flexible Active Matrix Organic Light Emitting Display with Oxide Thin Film Transistor

    NASA Astrophysics Data System (ADS)

    Hatano, Kaoru; Chida, Akihiro; Okano, Tatsuya; Sugisawa, Nozomu; Inoue, Tatsunori; Seo, Satoshi; Suzuki, Kunihiko; Oikawa, Yoshiaki; Miyake, Hiroyuki; Koyama, Jun; Yamazaki, Shunpei; Eguchi, Shingo; Katayama, Masahiro; Sakakura, Masayuki

    2011-03-01

    In this paper, we report a 3.4-in. flexible active matrix organic light emitting display (AMOLED) display with remarkably high definition (quarter high definition: QHD) in which oxide thin film transistors (TFTs) are used. We have developed a transfer technology in which a TFT array formed on a glass substrate is separated from the substrate by physical force and then attached to a flexible plastic substrate. Unlike a normal process in which a TFT array is directly fabricated on a thin plastic substrate, our transfer technology permits a high integration of high performance TFTs, such as low-temperature polycrystalline silicon TFTs (LTPS TFTs) and oxide TFTs, on a plastic substrate, because a flat, rigid, and thermally-stable glass substrate can be used in the TFT fabrication process in our transfer technology. As a result, this technology realized an oxide TFT array for an AMOLED on a plastic substrate. Furthermore, in order to achieve a high-definition AMOLED, color filters were incorporated in the TFT array and a white organic light-emitting diode (OLED) was combined. One of the features of this device is that the whole body of the device can be bent freely because a source driver and a gate driver can be integrated on the substrate due to the high mobility of an oxide TFT. This feature means “true” flexibility.

  1. AFM, ellipsometry, XPS and TEM on ultra-thin oxide/polymer nanocomposite layers in organic thin film transistors.

    PubMed

    Fian, A; Haase, A; Stadlober, B; Jakopic, G; Matsko, N B; Grogger, W; Leising, G

    2008-03-01

    Here we report on the fabrication and characterization of ultra-thin nanocomposite layers used as gate dielectric in low-voltage and high-performance flexible organic thin film transistors (oTFTs). Reactive sputtered zirconia layers were deposited with low thermal exposure of the substrate and the resulting porous oxide films with high leakage currents were spin-coated with an additional layer of poly-alpha-methylstyrene (P alphaMS). After this treatment a strong improvement of the oTFT performance could be observed; leakage currents could be eliminated almost completely. In ellipsometric studies a higher refractive index of the ZrO(2)/P alphaMS layers compared to the "as sputtered" zirconia films could be detected without a significant enhancement of the film thickness. Atomic force microscopy (AFM) measurements of the surface topography clearly showed a surface smoothing after the P alphaMS coating. Further studies with X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) also indicated that the polymer definitely did not form an extra layer. The polymer chains rather (self-)assemble in the nano-scaled interspaces of the porous oxide film giving an oxide-polymer "nanocomposite" with a high oxide filling grade resulting in high dielectric constants larger than 15. The dielectric strength of more than 1 MV cm(-1) is in good accordance with the polymer-filled interspaces. PMID:17952415

  2. Recent progress in high performance and reliable n-type transition metal oxide-based thin film transistors

    NASA Astrophysics Data System (ADS)

    Kwon, Jang Yeon; Kyeong Jeong, Jae

    2015-02-01

    This review gives an overview of the recent progress in vacuum-based n-type transition metal oxide (TMO) thin film transistors (TFTs). Several excellent review papers regarding metal oxide TFTs in terms of fundamental electron structure, device process and reliability have been published. In particular, the required field-effect mobility of TMO TFTs has been increasing rapidly to meet the demands of the ultra-high-resolution, large panel size and three dimensional visual effects as a megatrend of flat panel displays, such as liquid crystal displays, organic light emitting diodes and flexible displays. In this regard, the effects of the TMO composition on the performance of the resulting oxide TFTs has been reviewed, and classified into binary, ternary and quaternary composition systems. In addition, the new strategic approaches including zinc oxynitride materials, double channel structures, and composite structures have been proposed recently, and were not covered in detail in previous review papers. Special attention is given to the advanced device architecture of TMO TFTs, such as back-channel-etch and self-aligned coplanar structure, which is a key technology because of their advantages including low cost fabrication, high driving speed and unwanted visual artifact-free high quality imaging. The integration process and related issues, such as etching, post treatment, low ohmic contact and Cu interconnection, required for realizing these advanced architectures are also discussed.

  3. Small-dose-sensitive X-ray image pixel with HgI2 photoconductor and amorphous oxide thin-film transistor.

    PubMed

    Park, Jae Chul; Jeon, Pyo Jin; Kim, Jin Sung; Im, Seongil

    2015-01-01

    A new X-ray image sensor is demonstrated with an oxide thin-film transistor backplane and HgI2 sensing material. It displays outstanding image quality under a low X-ray exposure and a low electric field. It is promising as a state-of-the-art device to realize highly resolved images at a low X-ray dose for a variety of medical X-ray imaging applications. PMID:24753443

  4. Indium oxide thin-film transistors processed at low temperature via ultrasonic spray pyrolysis.

    PubMed

    Faber, Hendrik; Lin, Yen-Hung; Thomas, Stuart R; Zhao, Kui; Pliatsikas, Nikos; McLachlan, Martyn A; Amassian, Aram; Patsalas, Panos A; Anthopoulos, Thomas D

    2015-01-14

    The use of ultrasonic spray pyrolysis is demonstrated for the growth of polycrystalline, highly uniform indium oxide films at temperatures in the range of 200-300 °C in air using an aqueous In(NO3)3 precursor solution. Electrical characterization of as-deposited films by field-effect measurements reveals a strong dependence of the electron mobility on deposition temperature. Transistors fabricated at ∼250 °C exhibit optimum performance with maximum electron mobility values in the range of 15-20 cm(2) V (-1) s(-1) and current on/off ratio in excess of 10(6). Structural and compositional analysis of as-grown films by means of X-ray diffraction, diffuse scattering, and X-ray photoelectron spectroscopy reveal that layers deposited at 250 °C are denser and contain a reduced amount of hydroxyl groups as compared to films grown at either lower or higher temperatures. Microstructural analysis of semiconducting films deposited at 250 °C by high resolution cross-sectional transmission electron microscopy reveals that as-grown layers are extremely thin (∼7 nm) and composed of laterally large (30-60 nm) highly crystalline In2O3 domains. These unique characteristics of the In2O3 films are believed to be responsible for the high electron mobilities obtained from transistors fabricated at 250 °C. Our work demonstrates the ability to grow high quality low-dimensional In2O3 films and devices via ultrasonic spray pyrolysis over large area substrates while at the same time it provides guidelines for further material and device improvements. PMID:25490965

  5. Thermally deposited Ag-doped CdS thin film transistors with high-k rare-earth oxide Nd{sub 2}O{sub 3} as gate dielectric

    SciTech Connect

    Gogoi, P.

    2013-03-15

    The performance of thermally deposited CdS thin film transistors doped with Ag has been reported. Ag-doped CdS thin films have been prepared using chemical method. High dielectric constant rare earth oxide Nd{sub 2}O{sub 3} has been used as gate insulator. The thin film trasistors are fabricated in coplanar electrode structure on ultrasonically cleaned glass substrates with a channel length of 50 {mu}m. The thin film transistors exhibit a high mobility of 4.3 cm{sup 2} V{sup -1} s{sup -1} and low threshold voltage of 1 V. The ON-OFF ratio of the thin film transistors is found as 10{sup 5}. The TFTs also exhibit good transconductance and gain band-width product of 1.15 Multiplication-Sign 10{sup -3} mho and 71 kHz respectively.

  6. Semiconductor to metallic transition in bulk accumulated amorphous indium-gallium-zinc-oxide dual gate thin-film transistor

    SciTech Connect

    Chun, Minkyu; Chowdhury, Md Delwar Hossain; Jang, Jin

    2015-05-15

    We investigated the effects of top gate voltage (V{sub TG}) and temperature (in the range of 25 to 70 {sup o}C) on dual-gate (DG) back-channel-etched (BCE) amorphous-indium-gallium-zinc-oxide (a-IGZO) thin film transistors (TFTs) characteristics. The increment of V{sub TG} from -20V to +20V, decreases the threshold voltage (V{sub TH}) from 19.6V to 3.8V and increases the electron density to 8.8 x 10{sup 18}cm{sup −3}. Temperature dependent field-effect mobility in saturation regime, extracted from bottom gate sweep, show a critical dependency on V{sub TG}. At V{sub TG} of 20V, the mobility decreases from 19.1 to 15.4 cm{sup 2}/V ⋅ s with increasing temperature, showing a metallic conduction. On the other hand, at V{sub TG} of - 20V, the mobility increases from 6.4 to 7.5cm{sup 2}/V ⋅ s with increasing temperature. Since the top gate bias controls the position of Fermi level, the temperature dependent mobility shows metallic conduction when the Fermi level is above the conduction band edge, by applying high positive bias to the top gate.

  7. Improvement in gate bias stress instability of amorphous indium-gallium-zinc oxide thin-film transistors using microwave irradiation

    SciTech Connect

    Jo, Kwang-Won; Cho, Won-Ju

    2014-11-24

    In this study, we evaluated the effects of microwave irradiation (MWI) post-deposition-annealing (PDA) treatment on the gate bias stress instability of amorphous indium-gallium-zinc oxide thin-film transistors (a-IGZO TFTs) and compared the results with a conventional thermal annealing PDA treatment. The MWI-PDA-treated a-IGZO TFTs exhibited enhanced electrical performance as well as improved long-term stability with increasing microwave power. The positive turn-on voltage shift (ΔV{sub ON}) as a function of stress time with positive bias and varying temperature was precisely modeled on a stretched-exponential equation, suggesting that charge trapping is a dominant mechanism in the instability of MWI-PDA-treated a-IGZO TFTs. The characteristic trapping time and average effective barrier height for electron transport indicate that the MWI-PDA treatment effectively reduces the defects in a-IGZO TFTs, resulting in a superior resistance against gate bias stress.

  8. Crystallization behavior of amorphous indium-gallium-zinc-oxide films and its effects on thin-film transistor performance

    NASA Astrophysics Data System (ADS)

    Suko, Ayaka; Jia, JunJun; Nakamura, Shin-ichi; Kawashima, Emi; Utsuno, Futoshi; Yano, Koki; Shigesato, Yuzo

    2016-03-01

    Amorphous indium-gallium-zinc oxide (a-IGZO) films were deposited by DC magnetron sputtering and post-annealed in air at 300-1000 °C for 1 h to investigate the crystallization behavior in detail. X-ray diffraction, electron beam diffraction, and high-resolution electron microscopy revealed that the IGZO films showed an amorphous structure after post-annealing at 300 °C. At 600 °C, the films started to crystallize from the surface with c-axis preferred orientation. At 700-1000 °C, the films totally crystallized into polycrystalline structures, wherein the grains showed c-axis preferred orientation close to the surface and random orientation inside the films. The current-gate voltage (Id-Vg) characteristics of the IGZO thin-film transistor (TFT) showed that the threshold voltage (Vth) and subthreshold swing decreased markedly after the post-annealing at 300 °C. The TFT using the totally crystallized films also showed the decrease in Vth, whereas the field-effect mobility decreased considerably.

  9. Contact resistance asymmetry of amorphous indium–gallium–zinc–oxide thin-film transistors by scanning Kelvin probe microscopy

    NASA Astrophysics Data System (ADS)

    Chen-Fei, Wu; Yun-Feng, Chen; Hai, Lu; Xiao-Ming, Huang; Fang-Fang, Ren; Dun-Jun, Chen; Rong, Zhang; You-Dou, Zheng

    2016-05-01

    In this work, a method based on scanning Kelvin probe microscopy is proposed to separately extract source/drain (S/D) series resistance in operating amorphous indium–gallium–zinc–oxide (a-IGZO) thin-film transistors. The asymmetry behavior of S/D contact resistance is deduced and the underlying physics is discussed. The present results suggest that the asymmetry of S/D contact resistance is caused by the difference in bias conditions of the Schottky-like junction at the contact interface induced by the parasitic reaction between contact metal and a-IGZO. The overall contact resistance should be determined by both the bulk channel resistance of the contact region and the interface properties of the metal-semiconductor junction. Project supported by the Key Industrial R&D Program of Jiangsu Province, China (Grant No. BE2015155), the Priority Academic Program Development of Higher Education Institutions of Jiangsu Province, China, and the Fundamental Research Funds for the Central Universities, China (Grant No. 021014380033).

  10. Channel length dependence of negative-bias-illumination-stress in amorphous-indium-gallium-zinc-oxide thin-film transistors

    SciTech Connect

    Um, Jae Gwang; Mativenga, Mallory; Jang, Jin; Migliorato, Piero

    2015-06-21

    We have investigated the dependence of Negative-Bias-illumination-Stress (NBIS) upon channel length, in amorphous-indium-gallium-zinc-oxide (a-IGZO) thin-film transistors (TFTs). The negative shift of the transfer characteristic associated with NBIS decreases for increasing channel length and is practically suppressed in devices with L = 100-μm. The effect is consistent with creation of donor defects, mainly in the channel regions adjacent to source and drain contacts. Excellent agreement with experiment has been obtained by an analytical treatment, approximating the distribution of donors in the active layer by a double exponential with characteristic length L{sub D} ∼ L{sub n} ∼ 10-μm, the latter being the electron diffusion length. The model also shows that a device with a non-uniform doping distribution along the active layer is in all equivalent, at low drain voltages, to a device with the same doping averaged over the active layer length. These results highlight a new aspect of the NBIS mechanism, that is, the dependence of the effect upon the relative magnitude of photogenerated holes and electrons, which is controlled by the device potential/band profile. They may also provide the basis for device design solutions to minimize NBIS.

  11. Coplanar amorphous-indium-gallium-zinc-oxide thin film transistor with He plasma treated heavily doped layer

    SciTech Connect

    Jeong, Ho-young; Lee, Bok-young; Lee, Young-jang; Lee, Jung-il; Yang, Myoung-su; Kang, In-byeong; Mativenga, Mallory; Jang, Jin

    2014-01-13

    We report thermally stable coplanar amorphous-indium-gallium-zinc-oxide (a-IGZO) thin-film transistors (TFTs) with heavily doped n{sup +} a-IGZO source/drain regions. Doping is through He plasma treatment in which the resistivity of the a-IGZO decreases from 2.98 Ω cm to 2.79 × 10{sup −3} Ω cm after treatment, and then it increases to 7.92 × 10{sup −2} Ω cm after annealing at 300 °C. From the analysis of X-ray photoelectron spectroscopy, the concentration of oxygen vacancies in He plasma treated n{sup +}a-IGZO does not change much after thermal annealing at 300 °C, indicating thermally stable n{sup +} a-IGZO, even for TFTs with channel length L = 4 μm. Field-effect mobility of the coplanar a-IGZO TFTs with He plasma treatment changes from 10.7 to 9.2 cm{sup 2}/V s after annealing at 300 °C, but the performance of the a-IGZO TFT with Ar or H{sub 2} plasma treatment degrades significantly after 300 °C annealing.

  12. Anion control as a strategy to achieve high-mobility and high-stability oxide thin-film transistors

    PubMed Central

    Kim, Hyun-Suk; Jeon, Sang Ho; Park, Joon Seok; Kim, Tae Sang; Son, Kyoung Seok; Seon, Jong-Baek; Seo, Seok-Jun; Kim, Sun-Jae; Lee, Eunha; Chung, Jae Gwan; Lee, Hyungik; Han, Seungwu; Ryu, Myungkwan; Lee, Sang Yoon; Kim, Kinam

    2013-01-01

    Ultra-definition, large-area displays with three-dimensional visual effects represent megatrend in the current/future display industry. On the hardware level, such a “dream” display requires faster pixel switching and higher driving current, which in turn necessitate thin-film transistors (TFTs) with high mobility. Amorphous oxide semiconductors (AOS) such as In-Ga-Zn-O are poised to enable such TFTs, but the trade-off between device performance and stability under illumination critically limits their usability, which is related to the hampered electron-hole recombination caused by the oxygen vacancies. Here we have improved the illumination stability by substituting oxygen with nitrogen in ZnO, which may deactivate oxygen vacancies by raising valence bands above the defect levels. Indeed, the stability under illumination and electrical bias is superior to that of previous AOS-based TFTs. By achieving both mobility and stability, it is highly expected that the present ZnON TFTs will be extensively deployed in next-generation flat-panel displays. PMID:23492854

  13. Lateral-coupling coplanar-gate oxide-based thin-film transistors on bare paper substrates

    NASA Astrophysics Data System (ADS)

    Wu, Guodong; Wan, Xiang; Yang, Yi; Jiang, Shuanghe

    2014-11-01

    For conventional thin-film transistors (TFTs), bottom-gate or top-gate configuration is always adopted because the channel current is generally controlled by vertical capacitive coupling. In this article, depending on huge lateral electric-double-layer (EDL) capacitor induced by spatial movement of protons in phosphosilicate glass (PSG) solid electrolyte dielectrics, coplanar-gate indium-zinc-oxide (IZO)-TFTs based on the lateral capacitive coupling were fabricated on bare paper substrates. The PSG solid electrolyte films here were used at the same time as gate dielectrics and smooth buffer layers. These TFTs showed a low-voltage operation of only 1 V with a large field-effect mobility of 13.4 cm2 V-1·s, a high current on/off ratio of 6  ×  106 and a small subthreshold swing of 75 mV/decade. Furthermore, with introducing another coplanar gate, AND logic operation was also demonstrated on the coplanar dual-gate TFTs. These simple lateral-coupling coplanar-gate IZO-TFTs on bare paper substrates are very promising for low-cost portable sensors and bio-electronics.

  14. Anion control as a strategy to achieve high-mobility and high-stability oxide thin-film transistors.

    PubMed

    Kim, Hyun-Suk; Jeon, Sang Ho; Park, Joon Seok; Kim, Tae Sang; Son, Kyoung Seok; Seon, Jong-Baek; Seo, Seok-Jun; Kim, Sun-Jae; Lee, Eunha; Chung, Jae Gwan; Lee, Hyungik; Han, Seungwu; Ryu, Myungkwan; Lee, Sang Yoon; Kim, Kinam

    2013-01-01

    Ultra-definition, large-area displays with three-dimensional visual effects represent megatrend in the current/future display industry. On the hardware level, such a "dream" display requires faster pixel switching and higher driving current, which in turn necessitate thin-film transistors (TFTs) with high mobility. Amorphous oxide semiconductors (AOS) such as In-Ga-Zn-O are poised to enable such TFTs, but the trade-off between device performance and stability under illumination critically limits their usability, which is related to the hampered electron-hole recombination caused by the oxygen vacancies. Here we have improved the illumination stability by substituting oxygen with nitrogen in ZnO, which may deactivate oxygen vacancies by raising valence bands above the defect levels. Indeed, the stability under illumination and electrical bias is superior to that of previous AOS-based TFTs. By achieving both mobility and stability, it is highly expected that the present ZnON TFTs will be extensively deployed in next-generation flat-panel displays. PMID:23492854

  15. Oxide Semiconductor-Based Flexible Organic/Inorganic Hybrid Thin-Film Transistors Fabricated on Polydimethylsiloxane Elastomer.

    PubMed

    Jung, Soon-Won; Choi, Jeong-Seon; Park, Jung Ho; Koo, Jae Bon; Park, Chan Woo; Na, Bock Soon; Oh, Ji-Young; Lim, Sang Chul; Lee, Sang Seok; Chu, Hye Yong

    2016-03-01

    We demonstrate flexible organic/inorganic hybrid thin-film transistors (TFTs) on a polydimethysilox- ane (PDMS) elastomer substrate. The active channel and gate insulator of the hybrid TFT are composed of In-Ga-Zn-O (IGZO) and blends of poly(vinylidene fluoride-trifluoroethylene) [P(VDF- TrFE)] with poly(methyl methacrylate) (PMMA), respectively. It has been confirmed that the fabri- cated TFT display excellent characteristics: the recorded field-effect mobility, sub-threshold voltage swing, and I(on)/I(off) ratio were approximately 0.35 cm2 V(-1) s(-1), 1.5 V/decade, and 10(4), respectively. These characteristics did not experience any degradation at a bending radius of 15 mm. These results correspond to the first demonstration of a hybrid-type TFT using an organic gate insulator/oxide semiconducting active channel structure fabricated on PDMS elastomer, and demonstrate the feasibility of a promising device in a flexible electronic system. PMID:27455702

  16. Tailoring indium oxide nanocrystal synthesis conditions for air-stable high-performance solution-processed thin-film transistors.

    PubMed

    Swisher, Sarah L; Volkman, Steven K; Subramanian, Vivek

    2015-05-20

    Semiconducting metal oxides (ZnO, SnO2, In2O3, and combinations thereof) are a uniquely interesting family of materials because of their high carrier mobilities in the amorphous and generally disordered states, and solution-processed routes to these materials are of particular interest to the printed electronics community. Colloidal nanocrystal routes to these materials are particularly interesting, because nanocrystals may be formulated with tunable surface properties into stable inks, and printed to form devices in an additive manner. We report our investigation of an In2O3 nanocrystal synthesis for high-performance solution-deposited semiconductor layers for thin-film transistors (TFTs). We studied the effects of various synthesis parameters on the nanocrystals themselves, and how those changes ultimately impacted the performance of TFTs. Using a sintered film of solution-deposited In2O3 nanocrystals as the TFT channel material, we fabricated devices that exhibit field effect mobility of 10 cm(2)/(V s) and an on/off current ratio greater than 1 × 10(6). These results outperform previous air-stable nanocrystal TFTs, and demonstrate the suitability of colloidal nanocrystal inks for high-performance printed electronics. PMID:25915094

  17. Low-Temperature Solution Processing of Amorphous Metal Oxide Semiconductors for High-Performance Thin-Film Transistors

    NASA Astrophysics Data System (ADS)

    Hennek, Jonathan W.

    The growing field of large-area flexible electronics presents the need for amorphous materials with electrical performances superior to amorphous hydrogenated silicon (a-Si:H). Metal oxide semiconductors show great promise in thin film transistors (TFTs) due to their high electron mobility (micro, 1--100 cm2V-1s-1), mechanical flexibility, and electrical stability. However, most oxide semiconductor fabrication still relies on expensive, inflexible and energy intensive vacuum deposition methods. To overcome these limitations, my thesis work has focused on developing low-temperature solution processing routes to functional metal oxide materials. In Chapter 2, we demonstrate an optimized "ink" and printing process for inkjet patterning of amorphous indium gallium zinc oxide (a-IGZO) and investigate the effects of device structure on derived electron mobility. Bottom-gate top-contact (BGTC) TFTs are fabricated and shown to exhibit electron mobilities comparable to a-Si:H. Furthermore, a record micro of 2.5 cm 2V-1s-1 is demonstrated for bottom-gate bottom-contact (BGBC) TFTs. The mechanism underlying such impressive performance is investigated using transmission line techniques, and it is shown that the semiconductor-source/drain electrode interface contact resistance is nearly an order of magnitude lower for BGBC transistors versus BGTC devices. In Chapter 3, we report the implementation of amorphous indium yttrium oxide (a-IYO) as a TFT semiconductor for the first time. Amorphous and polycrystalline IYO films are grown via a low-temperature solution process utilizing exothermic "combustion" precursors. Precursor transformation and the IYO films are analyzed by DTA, TGA, XRD, AFM, XPS, and optical transmission, revealing efficient conversion to the metal-oxide lattice, and smooth, transparent films. a-IYO TFTs fabricated with a hybrid nanodielectric exhibit impressive electron mobilities of 7.3 cm2V-1s-1 (Tanneal = 300 °C) and 5.0 cm2V-1s -1 (Tanneal = 250 °C) for 2

  18. Rapid low-temperature processing of metal-oxide thin film transistors with combined far ultraviolet and thermal annealing

    SciTech Connect

    Leppäniemi, J. Ojanperä, K.; Kololuoma, T.; Huttunen, O.-H.; Majumdar, H.; Alastalo, A.; Dahl, J.; Tuominen, M.; Laukkanen, P.

    2014-09-15

    We propose a combined far ultraviolet (FUV) and thermal annealing method of metal-nitrate-based precursor solutions that allows efficient conversion of the precursor to metal-oxide semiconductor (indium zinc oxide, IZO, and indium oxide, In{sub 2}O{sub 3}) both at low-temperature and in short processing time. The combined annealing method enables a reduction of more than 100 °C in annealing temperature when compared to thermally annealed reference thin-film transistor (TFT) devices of similar performance. Amorphous IZO films annealed at 250 °C with FUV for 5 min yield enhancement-mode TFTs with saturation mobility of ∼1 cm{sup 2}/(V·s). Amorphous In{sub 2}O{sub 3} films annealed for 15 min with FUV at temperatures of 180 °C and 200 °C yield TFTs with low-hysteresis and saturation mobility of 3.2 cm{sup 2}/(V·s) and 7.5 cm{sup 2}/(V·s), respectively. The precursor condensation process is clarified with x-ray photoelectron spectroscopy measurements. Introducing the FUV irradiation at 160 nm expedites the condensation process via in situ hydroxyl radical generation that results in the rapid formation of a continuous metal-oxygen-metal structure in the film. The results of this paper are relevant in order to upscale printed electronics fabrication to production-scale roll-to-roll environments.

  19. Investigation on the negative bias illumination stress-induced instability of amorphous indium-tin-zinc-oxide thin film transistors

    SciTech Connect

    Jang, Jaeman; Kim, Dae Geun; Kim, Dong Myong; Choi, Sung-Jin; Kim, Dae Hwan E-mail: drlife@kookmin.ac.kr; Lim, Jun-Hyung; Lee, Je-Hun; Ahn, Byung Du E-mail: drlife@kookmin.ac.kr; Kim, Yong-Sung

    2014-10-13

    The quantitative analysis of mechanism on negative bias illumination stress (NBIS)-induced instability of amorphous indium-tin-zinc-oxide thin-film transistor (TFT) was suggested along with the effect of equivalent oxide thickness (EOT) of gate insulator. The analysis was implemented through combining the experimentally extracted density of subgap states and the device simulation. During NBIS, it was observed that the thicker EOT causes increase in both the shift of threshold voltage and the variation of subthreshold swing as well as the hump-like feature in a transfer curve. We found that the EOT-dependence of NBIS instability can be clearly explicated with the donor creation model, in which a larger amount of valence band tail states is transformed into either the ionized oxygen vacancy V{sub O}{sup 2+} or peroxide O{sub 2}{sup 2−} with the increase of EOT. It was also found that the V{sub O}{sup 2+}-related extrinsic factor accounts for 80%–92% of the total donor creation taking place in the valence band tail states while the rest is taken by the O{sub 2}{sup 2–} related intrinsic factor. The ratio of extrinsic factor compared to the total donor creation also increased with the increase of EOT, which could be explained by more prominent oxygen deficiency. The key founding of our work certainly represents that the established model should be considered very effective for analyzing the instability of the post-indium-gallium-zinc-oxide (IGZO) ZnO-based compound semiconductor TFTs with the mobility, which is much higher than those of a-IGZO TFTs.

  20. High Performance Airbrushed Organic Thin Film Transistors

    SciTech Connect

    Chan, C.; Richter, L; Dinardo, B; Jaye, C; Conrad, B; Ro, H; Germack, D; Fischer, D; DeLongchamp, D; Gunlach, D

    2010-01-01

    Spray-deposited poly-3-hexylthiophene (P3HT) transistors were characterized using electrical and structural methods. Thin-film transistors with octyltrichlorosilane treated gate dielectrics and spray-deposited P3HT active layers exhibited a saturation regime mobility as high as 0.1 cm{sup 2} V{sup -1} s{sup -1}, which is comparable to the best mobilities observed in high molecular mass P3HT transistors prepared using other methods. Optical and atomic force microscopy showed the presence of individual droplets with an average diameter of 20 {micro}m and appreciable large-scale film inhomogeneities. Despite these inhomogeneities, near-edge x-ray absorption fine structure spectroscopy of the device-relevant channel interface indicated excellent orientation of the P3HT.

  1. Exploring Two-Dimensional Transport Phenomena in Metal Oxide Heterointerfaces for Next-Generation, High-Performance, Thin-Film Transistor Technologies.

    PubMed

    Labram, John G; Lin, Yen-Hung; Anthopoulos, Thomas D

    2015-11-01

    In the last decade, metal oxides have emerged as a fascinating class of electronic material, exhibiting a wide range of unique and technologically relevant characteristics. For example, thin-film transistors formed from amorphous or polycrystalline metal oxide semiconductors offer the promise of low-cost, large-area, and flexible electronics, exhibiting performances comparable to or in excess of incumbent silicon-based technologies. Atomically flat interfaces between otherwise insulating or semiconducting complex oxides, are also found to be highly conducting, displaying 2-dimensional (2D) charge transport properties, strong correlations, and even superconductivity. Field-effect devices employing such carefully engineered interfaces are hoped to one day compete with traditional group IV or III-V semiconductors for use in the next-generation of high-performance electronics. In this Concept article we provide an overview of the different metal oxide transistor technologies and potential future research directions. In particular, we look at the recent reports of multilayer oxide thin-film transistors and the possibility of 2D electron transport in these disordered/polycrystalline systems and discuss the potential of the technology for applications in large-area electronics. PMID:26349850

  2. Highly flexible electronics from scalable vertical thin film transistors.

    PubMed

    Liu, Yuan; Zhou, Hailong; Cheng, Rui; Yu, Woojong; Huang, Yu; Duan, Xiangfeng

    2014-03-12

    Flexible thin-film transistors (TFTs) are of central importance for diverse electronic and particularly macroelectronic applications. The current TFTs using organic or inorganic thin film semiconductors are usually limited by either poor electrical performance or insufficient mechanical flexibility. Here, we report a new design of highly flexible vertical TFTs (VTFTs) with superior electrical performance and mechanical robustness. By using the graphene as a work-function tunable contact for amorphous indium gallium zinc oxide (IGZO) thin film, the vertical current flow across the graphene-IGZO junction can be effectively modulated by an external gate potential to enable VTFTs with a highest on-off ratio exceeding 10(5). The unique vertical transistor architecture can readily enable ultrashort channel devices with very high delivering current and exceptional mechanical flexibility. With large area graphene and IGZO thin film available, our strategy is intrinsically scalable for large scale integration of VTFT arrays and logic circuits, opening up a new pathway to highly flexible macroelectronics. PMID:24502192

  3. Role of oxygen vacancies on the bias illumination stress stability of solution-processed zinc tin oxide thin film transistors

    SciTech Connect

    Liu, Li-Chih; Chen, Jen-Sue E-mail: jsjeng@mail.nutn.edu.tw; Jeng, Jiann-Shing E-mail: jsjeng@mail.nutn.edu.tw

    2014-07-14

    Solution-processed ultra-thin (∼3 nm) zinc tin oxide (ZTO) thin film transistors (TFTs) with a mobility of 8 cm{sup 2}/Vs are obtained with post spin-coating annealing at only 350 °C. The effect of light illumination (at wavelengths of 405 nm or 532 nm) on the stability of TFT transfer characteristics under various gate bias stress conditions (zero, positive, and negative) is investigated. It is found that the ΔV{sub th} (V{sub th}{sup stress} {sup 3400} {sup s − stress} {sup 0} {sup s}) window is significantly positive when ZTO TFTs are under positive bias stress (PBS, ΔV{sub th} = 9.98 V) and positive bias illumination stress (λ = 405 nm and ΔV{sub th} = 6.96 V), but ΔV{sub th} is slightly negative under only light illumination stress (λ = 405 nm and ΔV{sub th} = −2.02 V) or negative bias stress (ΔV{sub th} = −2.27 V). However, the ΔV{sub th} of ZTO TFT under negative bias illumination stress is substantial, and it will efficiently recover the ΔV{sub th} caused by PBS. The result is attributed to the photo-ionization and subsequent transition of electronic states of oxygen vacancies (i.e., V{sub o}, V{sub o}{sup +}, and V{sub o}{sup ++}) in ZTO. A detailed mechanism is discussed to better understand the bias stress stability of solution processed ZTO TFTs.

  4. The effect of nitrous oxide plasma treatment on the bias temperature stress of metal oxide thin film transistors with high mobility

    NASA Astrophysics Data System (ADS)

    Tseng, Wei-Hao; Fang, Shao-Wei; Lu, Chia-Yang; Chuang, Hung-Yang; Chang, Fan-Wei; Lin, Guan-Yu; Chen, Tsu-Wei; Ma, Kang-Hung; Chen, Hong-Syu; Chen, Teng-Ke; Chen, Yu-Hung; Lee, Jen-Yu; Shih, Tsung-Hsiang; Ting, Hung-Che; Chen, Chia-Yu; Lin, Yu-Hsin; Hong, Hong-Jye

    2015-01-01

    In this work, the effects of nitrous oxide plasma treatment on the negative bias temperature stress of indium tin zinc oxide (ITZO) and indium gallium zinc oxide (IGZO) thin film transistors (TFTs) were reported. ITZO TFTs were more suitable for the back channel etched-type device structure because they could withstand both Al- and Cu-acid damage. The initial threshold voltage range could be controlled to within 1 V. The root cause of poor negative bias temperature stress for ITZO was likely due to a higher mobility (∼3.3 times) and more carbon related contamination bonds (∼5.9 times) relative to IGZO. Finally, 65″ active-matrix organic light-emitting diode televisions using the ITZO and IGZO TFTs were fabricated.

  5. Reduction of the interfacial trap density of indium-oxide thin film transistors by incorporation of hafnium and annealing process

    SciTech Connect

    Lin, Meng-Fang E-mail: TSUKAGOSHI.Kazuhito@nims.go.jp; Gao, Xu; Mitoma, Nobuhiko; Kizu, Takio; Ou-Yang, Wei; Tsukagoshi, Kazuhito E-mail: TSUKAGOSHI.Kazuhito@nims.go.jp; Aikawa, Shinya; Nabatame, Toshihide

    2015-01-15

    The stable operation of transistors under a positive bias stress (PBS) is achieved using Hf incorporated into InO{sub x}-based thin films processed at relatively low temperatures (150 to 250 °C). The mobilities of the Hf-InO{sub x} thin-film transistors (TFTs) are higher than 8 cm{sup 2}/Vs. The TFTs not only have negligible degradation in the mobility and a small shift in the threshold voltage under PBS for 60 h, but they are also thermally stable at 85 °C in air, without the need for a passivation layer. The Hf-InO{sub x} TFT can be stable even annealed at 150 °C for positive bias temperature stability (PBTS). A higher stability is achieved by annealing the TFTs at 250 °C, originating from a reduction in the trap density at the Hf-InO{sub x}/gate insulator interface. The knowledge obtained here will aid in the realization of stable TFTs processed at low temperatures.

  6. Reduction of the interfacial trap density of indium-oxide thin film transistors by incorporation of hafnium and annealing process

    NASA Astrophysics Data System (ADS)

    Lin, Meng-Fang; Gao, Xu; Mitoma, Nobuhiko; Kizu, Takio; Ou-Yang, Wei; Aikawa, Shinya; Nabatame, Toshihide; Tsukagoshi, Kazuhito

    2015-01-01

    The stable operation of transistors under a positive bias stress (PBS) is achieved using Hf incorporated into InOx-based thin films processed at relatively low temperatures (150 to 250 °C). The mobilities of the Hf-InOx thin-film transistors (TFTs) are higher than 8 cm2/Vs. The TFTs not only have negligible degradation in the mobility and a small shift in the threshold voltage under PBS for 60 h, but they are also thermally stable at 85 °C in air, without the need for a passivation layer. The Hf-InOx TFT can be stable even annealed at 150 °C for positive bias temperature stability (PBTS). A higher stability is achieved by annealing the TFTs at 250 °C, originating from a reduction in the trap density at the Hf-InOx/gate insulator interface. The knowledge obtained here will aid in the realization of stable TFTs processed at low temperatures.

  7. Indium-zinc-oxide electric-double-layer thin-film transistors gated by silane coupling agents 3-triethoxysilylpropylamine-graphene oxide solid electrolyte

    NASA Astrophysics Data System (ADS)

    Guo, Liqiang; Huang, Yukai; Shi, Yangyang; Cheng, Guanggui; Ding, Jianning

    2015-07-01

    Silane coupling agents 3-triethoxysilylpropyla-mine-graphene oxide (KH550-GO) solid electrolyte are prepared by spin coating process. A high proton conductivity of ~1.2   ×   10-3 Scm-1 is obtained at room temperature. A strong electric-double-layer (EDL) effect is observed due to the accumulation of protons at KH550-GO/IZO interface. Indium-Zinc-Oxide thin film transistors gated by KH550-GO solid electrolyte are self-assembled on ITO glass substrates. Good electrical performances are obtained, such as a low subthreshold swing of ~140 mV/dec., a high current on/off ratio of ~2.9   ×   107 and a high field-effect mobility of ~13.2 cm2 V-1 S-1, respectively.

  8. Solution-Processed Flexible Fluorine-doped Indium Zinc Oxide Thin-Film Transistors Fabricated on Plastic Film at Low Temperature

    PubMed Central

    Seo, Jin-Suk; Jeon, Jun-Hyuck; Hwang, Young Hwan; Park, Hyungjin; Ryu, Minki; Park, Sang-Hee Ko; Bae, Byeong-Soo

    2013-01-01

    Transparent flexible fluorine-doped indium zinc oxide (IZO:F) thin-film transistors (TFTs) were demonstrated using the spin-coating method of the metal fluoride precursor aqueous solution with annealing at 200°C for 2 hrs on polyethylene naphthalate films. The proposed thermal evolution mechanism of metal fluoride aqueous precursor solution examined by thermogravimetric analysis and Raman spectroscopy can easily explain oxide formation. The chemical composition analysed by XPS confirms that the fluorine was doped in the thin films annealed below 250°C. In the IZO:F thin films, a doped fluorine atom substitutes for an oxygen atom generating a free electron or occupies an oxygen vacancy site eliminating an electron trap site. These dual roles of the doped fluorine can enhance the mobility and improve the gate bias stability of the TFTs. Therefore, the transparent flexible IZO:F TFT shows a high mobility of up to 4.1 cm2/V·s and stable characteristics under the various gate bias and temperature stresses. PMID:23803977

  9. Microscale Soft Patterning for Solution Processable Metal Oxide Thin Film Transistors.

    PubMed

    Jung, Sang Wook; Chae, Soo Sang; Park, Jee Ho; Oh, Jin Young; Bhang, Suk Ho; Baik, Hong Koo; Lee, Tae Il

    2016-03-23

    We introduce a microscale soft pattering (MSP) route utilizing contact printing of chemically inert sub-nanometer thick low molecular weight (LMW) poly(dimethylsiloxane) (PDMS) layers. These PDMS layers serve as a release agent layer between the n-type Ohmic metal and metal oxide semiconductors (MOSs) and provide a layer that protects the MOS from water in the surrounding environment. The feasibility of our MSP route was experimentally demonstrated by fabricating solution processable In2O3, IZO, and IGZO TFTs with aluminum (Al), a typical n-type Ohmic metal. We have demonstrated patterning gaps as small as 13 μm. The TFTs fabricated using MSP showed higher field-effect-mobility and lower hysteresis in comparison with those made using conventional photolithography. PMID:26919321

  10. Self-aligned top-gate amorphous indium zinc oxide thin-film transistors exceeding low-temperature poly-Si transistor performance.

    PubMed

    Park, Jae Chul; Lee, Ho-Nyeon; Im, Seongil

    2013-08-14

    Thin-film transistor (TFT) is a key component of active-matrix flat-panel displays (AMFPDs). These days, the low-temperature poly silicon (LTPS) TFTs are to match with advanced AMFPDs such as the active matrix organic light-emitting diode (AMOLED) display, because of their high mobility for fast pixel switching. However, the manufacturing process of LTPS TFT is quite complicated, costly, and scale-limited. Amorphous oxide semiconductor (AOS) TFT technology is another candidate, which is as simple as that of conventioanl amorphous (a)-Si TFTs in fabrication but provides much superior device performances to those of a-Si TFTs. Hence, various AOSs have been compared with LTPS for active channel layer of the advanced TFTs, but have always been found to be relatively inferior to LTPS. In the present work, we clear the persistent inferiority, innovating the device performaces of a-IZO TFT by adopting a self-aligned coplanar top-gate structure and modifying the surface of a-IZO material. Herein, we demonstrate a high-performance simple-processed a-IZO TFT with mobility of ∼157 cm(2) V(-1) s(-1), SS of ∼190 mV dec(-1), and good bias/photostabilities, which overall surpass the performances of high-cost LTPS TFTs. PMID:23823486

  11. Origin of Degradation Phenomenon under Drain Bias Stress for Oxide Thin Film Transistors using IGZO and IGO Channel Layers

    PubMed Central

    Bak, Jun Yong; Kang, Youngho; Yang, Shinhyuk; Ryu, Ho-Jun; Hwang, Chi-Sun; Han, Seungwu; Yoon, Sung-Min

    2015-01-01

    Top-gate structured thin film transistors (TFTs) using In-Ga-Zn-O (IGZO) and In-Ga-O (IGO) channel compositions were investigated to reveal a feasible origin for degradation phenomenon under drain bias stress (DBS). DBS-driven instability in terms of VTH shift, deviation of the SS value, and increase in the on-state current were detected only for the IGZO-TFT, in contrast to the IGO-TFT, which did not demonstrate VTH shift. These behaviors were visually confirmed via nanoscale transmission electron microscopy and energy-dispersive x-ray spectroscopy observations. To understand the degradation mechanism, we performed ab initio molecular dynamic simulations on the liquid phases of IGZO and IGO. The diffusivities of Ga and In atoms were enhanced in IGZO, confirming the degradation mechanism to be increased atomic diffusion. PMID:25601183

  12. Thermal Characteristics of Amorphous Indium-Gallium-Zinc-Oxide and Graphite in Display Panel Based Thin Film Transistors.

    PubMed

    Kim, Hak-Jun; Kim, Youn-Jea

    2015-11-01

    One of the important design factors in the smart electronic industry is proper heat treatment of the display panel. In order to improve the heat transfer performance of display panels, we analyzed a three-dimensional model of multi-stack layers of the thin film transistors (TFTs). In particular, we numerically investigated the thermal barrier effects of active layers having different material properties of a-IGZO (isotropy) and graphite (anisotropy). We calculated the temperature distribution on the display panel with each active layer, using the commercial code, COMSOL Multiphysics. We graphically depict comparative results of the thermal characteristics between a-IGZO and graphite with the stacked structure of the TFTs. PMID:26726627

  13. Electrical dependence on the chemical composition of the gate dielectric in indium gallium zinc oxide thin-film transistors

    NASA Astrophysics Data System (ADS)

    Tari, Alireza; Lee, Czang-Ho; Wong, William S.

    2015-07-01

    Bottom-gate thin-film transistors were fabricated by depositing a 50 nm InGaZnO (IGZO) channel layer at 150 °C on three separate gate dielectric films: (1) thermal SiO2, (2) plasma-enhanced chemical-vapor deposition (PECVD) SiNx, and (3) a PECVD SiOx/SiNx dual-dielectric. X-ray photoelectron and photoluminescence spectroscopy showed the Vo concentration was dependent on the hydrogen concentration of the underlying dielectric film. IGZO films on SiNx (high Vo) and SiO2 (low Vo) had the highest and lowest conductivity, respectively. A PECVD SiOx/SiNx dual-dielectric layer was effective in suppressing hydrogen diffusion from the nitride layer into the IGZO and resulted in higher resistivity films.

  14. Metal-semiconductor hybrid thin films in field-effect transistors

    SciTech Connect

    Okamura, Koshi Dehm, Simone; Hahn, Horst

    2013-12-16

    Metal-semiconductor hybrid thin films consisting of an amorphous oxide semiconductor and a number of aluminum dots in different diameters and arrangements are formed by electron beam lithography and employed for thin-film transistors (TFTs). Experimental and computational demonstrations systematically reveal that the field-effect mobility of the TFTs enhances but levels off as the dot density increases, which originates from variations of the effective channel length that strongly depends on the electric field distribution in a transistor channel.

  15. Investigation of the effects of deposition parameters on indium-free transparent amorphous oxide semiconductor thin-film transistors fabricated at low temperatures for flexible electronic applications

    NASA Astrophysics Data System (ADS)

    Alston, Robert; Iyer, Shanthi; Bradley, Tanina; Lewis, Jay; Cunningham, Garry; Forsythe, Eric

    2014-02-01

    Low temperature gallium tin zinc oxide (GSZO) based thin film transistors fabricated on silicon has been investigated as a potential indium free transparent amorphous oxide semiconductor thin film transistor (TAOS TFT) with potential device applications on plastic substrates. A comprehensive and detailed study on the performance of GSZO TFTs has been carried out by studying the effects of processing parameters such as deposition temperature and annealing temperature/duration, as well as the channel thickness with all temperatures held below 150 °C. Variety of characterization techniques, namely Rutherford backscattering (RBS), x-ray photoelectron spectroscopy (XPS) and x-ray reflectivity (XRR) in addition to I-V and C-V measurements were employed to determine the effects of the above parameters on the composition and quality of the channel. Optimized TFT characteristics of ID=3×10-7 A, ION/OFF =2×106, VON ~ -2 V, SS ~ 1 V/dec and μFE = 0.14 cm2/V· s with a ΔVON of 3.3 V under 3 hours electrical stress were produced.

  16. Influence of molybdenum source/drain electrode contact resistance in amorphous zinc–tin-oxide (a-ZTO) thin film transistors

    SciTech Connect

    Han, Dong-Suk; Kang, Yu-Jin; Park, Jae-Hyung; Jeon, Hyung-Tag; Park, Jong-Wan

    2014-10-15

    Highlights: • We developed and investigated source/drain electrodes in oxide TFTs. • The Mo S/D electrodes showed good output characteristics. • Intrinsic TFT parameters were calculated by the transmission line method. - Abstract: This paper investigates the feasibility of a low-resistivity electrode material (Mo) for source/drain (S/D) electrodes in thin film transistors (TFTs). The effective resistances between Mo source/drain electrodes and amorphous zinc–tin-oxide (a-ZTO) thin film transistors were studied. Intrinsic TFT parameters were calculated by the transmission line method (TLM) using a series of TFTs with different channel lengths measured at a low source/drain voltage. The TFTs fabricated with Mo source/drain electrodes showed good transfer characteristics with a field-effect mobility of 10.23 cm{sup 2}/V s. In spite of slight current crowding effects, the Mo source/drain electrodes showed good output characteristics with a steep rise in the low drain-to-source voltage (V{sub DS}) region.

  17. Li-Assisted Low-Temperature Phase Transitions in Solution-Processed Indium Oxide Films for High-Performance Thin Film Transistor.

    PubMed

    Nguyen, Manh-Cuong; Jang, Mi; Lee, Dong-Hwi; Bang, Hyun-Jun; Lee, Minjung; Jeong, Jae Kyeong; Yang, Hoichang; Choi, Rino

    2016-01-01

    Lithium (Li)-assisted indium oxide (In2O3) thin films with ordered structures were prepared on solution-processed zirconium oxide (ZrO2) gate dielectrics by spin-casting and thermally annealing hydrated indium nitrate solutions with different Li nitrate loadings. It was found that the Li-assisted In precursor films on ZrO2 dielectrics could form crystalline structures even at processing temperatures (T) below 200 °C. Different In oxidation states were observed in the Li-doped films, and the development of such states was significantly affected by both temperature and the mol% of Li cations, [Li(+)]/([In(3+)] + [Li(+)]), in the precursor solutions. Upon annealing the Li-assisted precursor films below 200 °C, metastable indium hydroxide and/or indium oxyhydroxide phases were formed. These phases were subsequently transformed into crystalline In2O3 nanostructures after thermal dehydration and oxidation. Finally, an In2O3 film doped with 13.5 mol% Li(+) and annealed at 250 °C for 1 h exhibited the highest electron mobility of 60 cm(2) V(-1) s(-1) and an on/off current ratio above 10(8) when utilized in a thin film transistor. PMID:27121951

  18. Li-Assisted Low-Temperature Phase Transitions in Solution-Processed Indium Oxide Films for High-Performance Thin Film Transistor

    PubMed Central

    Nguyen, Manh-Cuong; Jang, Mi; Lee, Dong-Hwi; Bang, Hyun-Jun; Lee, Minjung; Jeong, Jae Kyeong; Yang, Hoichang; Choi, Rino

    2016-01-01

    Lithium (Li)-assisted indium oxide (In2O3) thin films with ordered structures were prepared on solution-processed zirconium oxide (ZrO2) gate dielectrics by spin-casting and thermally annealing hydrated indium nitrate solutions with different Li nitrate loadings. It was found that the Li-assisted In precursor films on ZrO2 dielectrics could form crystalline structures even at processing temperatures (T) below 200 °C. Different In oxidation states were observed in the Li-doped films, and the development of such states was significantly affected by both temperature and the mol% of Li cations, [Li+]/([In3+] + [Li+]), in the precursor solutions. Upon annealing the Li-assisted precursor films below 200 °C, metastable indium hydroxide and/or indium oxyhydroxide phases were formed. These phases were subsequently transformed into crystalline In2O3 nanostructures after thermal dehydration and oxidation. Finally, an In2O3 film doped with 13.5 mol% Li+ and annealed at 250 °C for 1 h exhibited the highest electron mobility of 60 cm2 V−1 s−1 and an on/off current ratio above 108 when utilized in a thin film transistor. PMID:27121951

  19. Enhanced mobility of solution-processed polycrystalline zinc tin oxide thin-film transistors via direct incorporation of water into precursor solution

    NASA Astrophysics Data System (ADS)

    Huang, Genmao; Duan, Lian; Zhao, Yunlong; Dong, Guifang; Zhang, Deqiang; Qiu, Yong

    2014-09-01

    Phase transition and the consequent variation in crystalline orientation of metal oxides have profound impact on their transport properties. In this work, we report a simple method to enhance field-effect mobility of solution-processed zinc tin oxide (ZTO) thin-film transistors (TFTs) via direct incorporation of water into precursor solution. It is confirmed H2O molecules could effectively facilitate the conversion and alloying processes during ZTO film formation, characterized by the enhancement of spinel Zn2SnO4 phase and the reduction of cassiterite SnO2 phase. The preferred orientation of metal oxide crystallites varies according to the amount of water added into precursor solutions. Smooth and densely packed polycrystalline ZTO films with only a few organic residuals and moderate oxygen defects are fabricated from water-containing precursor solutions. With the incorporation of 1.67 M H2O, the extracted field-effect mobility of TFT devices could be improved by a factor of 2.3, from 0.92 to 2.11 cm2 V-1 s-1. This work offers a facile and cost-effective route towards high-mobility TFTs based on solution-processed polycrystalline metal oxide thin films.

  20. Li-Assisted Low-Temperature Phase Transitions in Solution-Processed Indium Oxide Films for High-Performance Thin Film Transistor

    NASA Astrophysics Data System (ADS)

    Nguyen, Manh-Cuong; Jang, Mi; Lee, Dong-Hwi; Bang, Hyun-Jun; Lee, Minjung; Jeong, Jae Kyeong; Yang, Hoichang; Choi, Rino

    2016-04-01

    Lithium (Li)-assisted indium oxide (In2O3) thin films with ordered structures were prepared on solution-processed zirconium oxide (ZrO2) gate dielectrics by spin-casting and thermally annealing hydrated indium nitrate solutions with different Li nitrate loadings. It was found that the Li-assisted In precursor films on ZrO2 dielectrics could form crystalline structures even at processing temperatures (T) below 200 °C. Different In oxidation states were observed in the Li-doped films, and the development of such states was significantly affected by both temperature and the mol% of Li cations, [Li+]/([In3+] + [Li+]), in the precursor solutions. Upon annealing the Li-assisted precursor films below 200 °C, metastable indium hydroxide and/or indium oxyhydroxide phases were formed. These phases were subsequently transformed into crystalline In2O3 nanostructures after thermal dehydration and oxidation. Finally, an In2O3 film doped with 13.5 mol% Li+ and annealed at 250 °C for 1 h exhibited the highest electron mobility of 60 cm2 V‑1 s‑1 and an on/off current ratio above 108 when utilized in a thin film transistor.

  1. Dopant selection for control of charge carrier density and mobility in amorphous indium oxide thin-film transistors: Comparison between Si- and W-dopants

    SciTech Connect

    Mitoma, Nobuhiko E-mail: TSUKAGOSHI.Kazuhito@nims.go.jp; Kizu, Takio; Lin, Meng-Fang; Tsukagoshi, Kazuhito E-mail: TSUKAGOSHI.Kazuhito@nims.go.jp; Aikawa, Shinya; Ou-Yang, Wei; Gao, Xu; Fujiwara, Akihiko

    2015-01-26

    The dependence of oxygen vacancy suppression on dopant species in amorphous indium oxide (a-InO{sub x}) thin film transistors (TFTs) is reported. In a-InO{sub x} TFTs incorporating equivalent atom densities of Si- and W-dopants, absorption of oxygen in the host a-InO{sub x} matrix was found to depend on difference of Gibbs free energy of the dopants for oxidation. For fully oxidized films, the extracted channel conductivity was higher in the a-InO{sub x} TFTs containing dopants of small ionic radius. This can be explained by a reduction in the ionic scattering cross sectional area caused by charge screening effects.

  2. Contact-enhanced transparent silver nanowire network for all solution-based top-contact metal-oxide thin-film transistors.

    PubMed

    Kim, Yong-Hoon; Kim, Tae-Hyoung; Lee, Yeji; Kim, Jong-Woong; Kim, Jaekyun; Park, Sung Kyu

    2014-11-01

    In this paper, we investigate contact-enhanced transparent silver nanowire (Ag NW) network for solution-processed metal-oxide thin-film transistors (TFTs). Mechanical roll pressing was applied to a bar-coated Ag NW film to enhance the inter-nanowire connectivity. As a result, the sheet resistance of the Ag NW film was decreased from 119.5 ψ/square to 92.4 ψ/square, and more stable and enhanced TFT characteristics were achieved when the roll-pressed Ag NW was employed as source/drain electrodes. In addition, a non-acidic wet etching method was developed to pattern the Ag NW electrodes to construct top-contact geometry indium-gallium-zinc oxide TFTs. From the results, it is believed that the mechanical roll pressing and non-acidic wet etching method may be utilized in realizing all solution-based transparent metal-oxide TFTs. PMID:25958491

  3. Effect of Al2O3 insulator thickness on the structural integrity of amorphous indium-gallium-zinc-oxide based thin film transistors.

    PubMed

    Kim, Hak-Jun; Hwang, In-Ju; Kim, Youn-Jea

    2014-12-01

    The current transparent oxide semiconductors (TOSs) technology provides flexibility and high performance. In this study, multi-stack nano-layers of TOSs were designed for three-dimensional analysis of amorphous indium-gallium-zinc-oxide (a-IGZO) based thin film transistors (TFTs). In particular, the effects of torsional and compressive stresses on the nano-sized active layers such as the a-IGZO layer were investigated. Numerical simulations were carried out to investigate the structural integrity of a-IGZO based TFTs with three different thicknesses of the aluminum oxide (Al2O3) insulator (δ = 10, 20, and 30 nm), respectively, using a commercial code, COMSOL Multiphysics. The results are graphically depicted for operating conditions. PMID:25971080

  4. Thin-film transistors based on p-type Cu{sub 2}O thin films produced at room temperature

    SciTech Connect

    Fortunato, Elvira; Figueiredo, Vitor; Barquinha, Pedro; Elamurugu, Elangovan; Goncalves, Goncalo; Martins, Rodrigo; Park, Sang-Hee Ko; Hwang, Chi-Sun

    2010-05-10

    Copper oxide (Cu{sub 2}O) thin films were used to produce bottom gate p-type transparent thin-film transistors (TFTs). Cu{sub 2}O was deposited by reactive rf magnetron sputtering at room temperature and the films exhibit a polycrystalline structure with a strongest orientation along (111) plane. The TFTs exhibit improved electrical performance such as a field-effect mobility of 3.9 cm{sup 2}/V s and an on/off ratio of 2x10{sup 2}.

  5. Chemical Gated Field Effect Transistor by Hybrid Integration of One-Dimensional Silicon Nanowire and Two-Dimensional Tin Oxide Thin Film for Low Power Gas Sensor.

    PubMed

    Han, Jin-Woo; Rim, Taiuk; Baek, Chang-Ki; Meyyappan, M

    2015-09-30

    Gas sensors based on metal-oxide-semiconductor transistor with the polysilicon gate replaced by a gas sensitive thin film have been around for over 50 years. These are not suitable for the emerging mobile and wearable sensor platforms due to operating voltages and powers far exceeding the supply capability of batteries. Here we present a novel approach to decouple the chemically sensitive region from the conducting channel for reducing the drive voltage and increasing reliability. This chemically gated field effect transistor uses silicon nanowire for the current conduction channel with a tin oxide film on top of the nanowire serving as the gas sensitive medium. The potential change induced by the molecular adsorption and desorption allows the electrically floating tin oxide film to gate the silicon channel. As the device is designed to be normally off, the power is consumed only during the gas sensing event. This feature is attractive for the battery operated sensor and wearable electronics. In addition, the decoupling of the chemical reaction and the current conduction regions allows the gas sensitive material to be free from electrical stress, thus increasing reliability. The device shows excellent gas sensitivity to the tested analytes relative to conventional metal oxide transistors and resistive sensors. PMID:26381613

  6. Long-term stabilization of sprayed zinc oxide thin film transistors by hexafluoropropylene oxide self assembled monolayers

    NASA Astrophysics Data System (ADS)

    Ortel, Marlis; Kalinovich, Nataliya; Röschenthaler, Gerd-Volker; Wagner, Veit

    2013-09-01

    Surface functionalization of solution processed zinc oxide layers was studied in transistors with bottom-gate bottom-contact configuration aiming at suppression of trapping processes to increase device stability. Saturation of electrically active surface sites and formation of a moisture barrier to decrease the impact of humid atmosphere was successfully shown by binding hexafluoropropylene oxide (HFPO) on the metal oxide semiconductor. Deep trap level related electrical parameters, i.e., stability, hysteresis, and on-set voltage, improved rapidly within 60 s of exposure which was attributed to occupation of sites characterized by low adsorption energies, e.g., at edges. In contrast, shallow trap level related parameters, i.e., mobility, showed a much slower process of improvement. Identical behavior was determined for the contact angle. A physical model is presented by applying first order reaction kinetics equation to Young's law and multiple trapping and release model which relates the dependence of the contact angle and the mobility to the hexafluoropropylene oxide deposition time. Consistent time constants of τ = ≪1 min, 2 min, and 250 min were extracted for mobility and contact angle which implies a direct dependence on the surface coverage. Mobility decreased at short deposition times, recovered at medium deposition times and improved strongly by 2.4 cm2 V-1 s-1 for long deposition times of 1400 min. A microscopic model of these phenomena is given with interpretation of the different time constants found in the experiment.

  7. Effects of annealing conditions on the dielectric properties of solution-processed Al2O3 layers for indium-zinc-tin-oxide thin-film transistors.

    PubMed

    Kim, Yong-Hoon; Kim, Kwang-Ho; Park, Sung Kyu

    2013-11-01

    In this paper, the effects of annealing conditions on the dielectric properties of solution-processed aluminum oxide (Al2O3) layers for indium-zinc-tin-oxide (IZTO) thin-film transistors (TFTs) have been investigated. The dielectric properties of Al2O3 layers such as leakage current density and dielectric strength were largely affected by their annealing conditions. In particular, oxygen partial pressure in rapid thermal annealing, and the temperature profile of hot plate annealing had profound effects on the dielectric properties. From a refractive index analysis, the enhanced dielectric properties of Al2O3 gate dielectrics can be attributed to higher film density depending on the annealing conditions. With the low-temperature-annealed Al2O3 gate dielectric at 350 degrees C, solution-processed IZTO TFTs with a field-effect mobility of approximately 2.2 cm2/Vs were successfully fabricated. PMID:24245333

  8. Homogeneous double-layer amorphous Si-doped indium oxide thin-film transistors for control of turn-on voltage

    NASA Astrophysics Data System (ADS)

    Kizu, Takio; Aikawa, Shinya; Nabatame, Toshihide; Fujiwara, Akihiko; Ito, Kazuhiro; Takahashi, Makoto; Tsukagoshi, Kazuhito

    2016-07-01

    We fabricated homogeneous double-layer amorphous Si-doped indium oxide (ISO) thin-film transistors (TFTs) with an insulating ISO cap layer on top of a semiconducting ISO bottom channel layer. The homogeneously stacked ISO TFT exhibited high mobility (19.6 cm2/V s) and normally-off characteristics after annealing in air. It exhibited normally-off characteristics because the ISO insulator suppressed oxygen desorption, which suppressed the formation of oxygen vacancies (VO) in the semiconducting ISO. Furthermore, we investigated the recovery of the double-layer ISO TFT, after a large negative shift in turn-on voltage caused by hydrogen annealing, by treating it with annealing in ozone. The recovery in turn-on voltage indicates that the dense VO in the semiconducting ISO can be partially filled through the insulator ISO. Controlling molecule penetration in the homogeneous double layer is useful for adjusting the properties of TFTs in advanced oxide electronics.

  9. Photo stability of solution-processed low-voltage high mobility zinc-tin-oxide/ZrO2 thin-film transistors for transparent display applications

    NASA Astrophysics Data System (ADS)

    Ha, Tae-Jun; Dodabalapur, Ananth

    2013-03-01

    We report solution-processed low-voltage zinc-tin-oxide (ZTO)/zirconium-oxide thin-film transistors (TFTs) possessing a field-effect mobility of ˜10 cm2/Vs, a threshold voltage of 0.1 V, and an on-off current ratio of ˜1 × 109. These TFTs exhibit very small hysteresis windows in both dark and illuminated conditions. We also investigate the photo stability combined with prolong negative bias in these devices. Large threshold voltage shifts and sub-threshold swing degradation typically observed in ZTO TFTs are not present in our devices. We believe that these device characteristics, which stem from the electronically clean semiconductor-dielectric interface, satisfy the requirement for high quality and low power-consuming transparent displays.

  10. Electrical dependence on the chemical composition of the gate dielectric in indium gallium zinc oxide thin-film transistors

    SciTech Connect

    Tari, Alireza Lee, Czang-Ho; Wong, William S.

    2015-07-13

    Bottom-gate thin-film transistors were fabricated by depositing a 50 nm InGaZnO (IGZO) channel layer at 150 °C on three separate gate dielectric films: (1) thermal SiO{sub 2}, (2) plasma-enhanced chemical-vapor deposition (PECVD) SiN{sub x}, and (3) a PECVD SiO{sub x}/SiN{sub x} dual-dielectric. X-ray photoelectron and photoluminescence spectroscopy showed the V{sub o} concentration was dependent on the hydrogen concentration of the underlying dielectric film. IGZO films on SiN{sub x} (high V{sub o}) and SiO{sub 2} (low V{sub o}) had the highest and lowest conductivity, respectively. A PECVD SiO{sub x}/SiN{sub x} dual-dielectric layer was effective in suppressing hydrogen diffusion from the nitride layer into the IGZO and resulted in higher resistivity films.

  11. Transistors: Chemically Functionalized, Well-Dispersed Carbon Nanotubes in Lithium-Doped Zinc Oxide for Low-Cost, High-Performance Thin-Film Transistors (Small 14/2016).

    PubMed

    Son, Gi-Cheol; Chee, Sang-Soo; Jun, Ji-Hyun; Son, Myungwoo; Lee, Sun Sook; Choi, Youngmin; Jeong, Sunho; Ham, Moon-Ho

    2016-04-01

    A simple, wet-chemical method for the surface functionalization of carbon nanotubes with hydrophilic groups is introduced in Li-doped ZnO by S. Jeong, M. H. Ham, and co-workers, on page 1859. This results in the uniform spatial distribution of single-walled carbon nanotubes in ultrathin ZnO-based matrix oxides, and facilitates high-mobility, low-cost metal-oxide-based thin-film transistors. This approach is compatible with various film formation processes, even printing processes, and enables the realization of high-performance, cost-effective, large-area electronics and displays based on metal oxides. PMID:27061455

  12. Improvement in performance of solution-processed indium-zinc-tin oxide thin-film transistors by UV/O3 treatment on zirconium oxide gate insulator

    NASA Astrophysics Data System (ADS)

    Naik, Bukke Ravindra; Avis, Christophe; Delwar Hossain Chowdhury, Md; Kim, Taehun; Lin, Tengda; Jang, Jin

    2016-03-01

    We studied solution-processed amorphous indium-zinc-tin oxide (a-IZTO) thin-film transistors (TFTs) with spin-coated zirconium oxide (ZrOx) as the gate insulator. The ZrOx gate insulator was used without and with UV/O3 treatment. The TFTs with an untreated ZrOx gate dielectric showed a saturation mobility (μsat) of 0.91 ± 0.29 cm2 V-1 s-1, a threshold voltage (Vth) of 0.28 ± 0.36 V, a subthreshold swing (SS) of 199 ± 37.17 mV/dec, and a current ratio (ION/IOFF) of ˜107. The TFTs with a UV/O3-treated ZrOx gate insulator exhibited μsat of 2.65 ± 0.43 cm2 V-1 s-1, Vth of 0.44 ± 0.35 V, SS of 133 ± 24.81 mV/dec, and ION/IOFF of ˜108. Hysteresis was 0.32 V in the untreated TFTs and was eliminated by UV/O3 treatment. Also, the leakage current decreased significantly when the IZTO TFT was coated onto a UV/O3-treated ZrOx gate insulator.

  13. Electrical Characteristics of Low-Temperature Polycrystalline Silicon Complementary Metal-Oxide-Semiconductor Thin-Film Transistors with Six-Step Photomask Structure

    NASA Astrophysics Data System (ADS)

    Lee, Sang-Jin; Park, Jae-Hoon; Oh, Kum-Mi; Lee, Seok-Woo; Lee, Kyung-Eon; Shin, Woo-Sup; Jun, Myung-chul; Yang, Yong-Suk; Hwang, Yong-Kee

    2011-06-01

    We propose two types of six-step photomask, complementary metal-oxide-semiconductor (CMOS), thin-film transistor (TFT) PCT device structures in order to simplify their fabrication process compared with that of conventional, low-temperature, polycrystalline silicon (LTPS) CMOS TFT devices. The initial charge transfer characteristics of both types of six-step PCT are equivalent to those of the conventional nine-step PCT. Both types of six-step PCT are comparable to the conventional nine-step mask lightly doped drain (LDD) device in terms of the dc device lifetime of over 10 years at Vds=5 V for line inversion driving, which is the normally recognized duration time for semiconducting devices.

  14. A thermalization energy analysis of the threshold voltage shift in amorphous indium gallium zinc oxide thin film transistors under positive gate bias stress

    NASA Astrophysics Data System (ADS)

    Niang, K. M.; Barquinha, P. M. C.; Martins, R. F. P.; Cobb, B.; Powell, M. J.; Flewitt, A. J.

    2016-02-01

    Thin film transistors (TFTs) employing an amorphous indium gallium zinc oxide (a-IGZO) channel layer exhibit a positive shift in the threshold voltage under the application of positive gate bias stress (PBS). The time and temperature dependence of the threshold voltage shift was measured and analysed using the thermalization energy concept. The peak energy barrier to defect conversion is extracted to be 0.75 eV and the attempt-to-escape frequency is extracted to be 107 s-1. These values are in remarkable agreement with measurements in a-IGZO TFTs under negative gate bias illumination stress (NBIS) reported recently (Flewitt and Powell, J. Appl. Phys. 115, 134501 (2014)). This suggests that the same physical process is responsible for both PBS and NBIS, and supports the oxygen vacancy defect migration model that the authors have previously proposed.

  15. Alumina nanoparticle/polymer nanocomposite dielectric for flexible amorphous indium-gallium-zinc oxide thin film transistors on plastic substrate with superior stability

    SciTech Connect

    Lai, Hsin-Cheng; Pei, Zingway; Jian, Jyun-Ruri; Tzeng, Bo-Jie

    2014-07-21

    In this study, the Al{sub 2}O{sub 3} nanoparticles were incorporated into polymer as a nono-composite dielectric for used in a flexible amorphous Indium-Gallium-Zinc Oxide (a-IGZO) thin-film transistor (TFT) on a polyethylene naphthalate substrate by solution process. The process temperature was well below 100 °C. The a-IGZO TFT exhibit a mobility of 5.13 cm{sup 2}/V s on the flexible substrate. After bending at a radius of 4 mm (strain = 1.56%) for more than 100 times, the performance of this a-IGZO TFT was nearly unchanged. In addition, the electrical characteristics are less altered after positive gate bias stress at 10 V for 1500 s. Thus, this technology is suitable for use in flexible displays.

  16. Effects of low-temperature (120 °C) annealing on the carrier concentration and trap density in amorphous indium gallium zinc oxide thin film transistors

    SciTech Connect

    Kim, Jae-sung; Piao, Mingxing; Jang, Ho-Kyun; Kim, Gyu-Tae; Oh, Byung Su; Joo, Min-Kyu; Ahn, Seung-Eon

    2014-12-28

    We report an investigation of the effects of low-temperature annealing on the electrical properties of amorphous indium gallium zinc oxide (a-IGZO) thin-film transistors (TFTs). X-ray photoelectron spectroscopy was used to characterize the charge carrier concentration, which is related to the density of oxygen vacancies. The field-effect mobility was found to decrease as a function of the charge carrier concentration, owing to the presence of band-tail states. By employing the transmission line method, we show that the contact resistance did not significantly contribute to the changes in device performance after annealing. In addition, using low-frequency noise analyses, we found that the trap density decreased by a factor of 10 following annealing at 120 °C. The switching operation and on/off ratio of the a-IGZO TFTs improved considerably after low-temperature annealing.

  17. Scaling characteristics of depletion type, fully transparent amorphous indium-gallium-zinc-oxide thin-film transistors and inverters following Ar plasma treatment

    NASA Astrophysics Data System (ADS)

    Kim, Joonwoo; Jeong, Soon Moon; Jeong, Jaewook

    2015-11-01

    We fabricated depletion type, transparent amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistors (TFTs) and inverters with an Ar plasma treatment and analyzed their scaling characteristics with channel lengths ranging from 2 to 100 µm. The improvement of the field-effect mobility of a-IGZO TFTs is apparent only for short channel lengths. There is also an unexpected side effect of the Ar plasma treatment, which introduces back-channel interfacial states and induces a positive shift in the threshold voltage of a-IGZO TFTs. The resulting increase in the field-effect mobility and the positive shift in the threshold voltage of each TFT increase the differential gain up to 3 times and the positive shift in the transient point of the transparent inverters.

  18. Effective enhancement of hydrophilicity of solution indium zinc oxide-based thin-film transistors by oxygen plasma treatment of deposition layer surface

    NASA Astrophysics Data System (ADS)

    You, Hsin-Chiang; Wang, Yu-Chih

    2016-06-01

    In this paper, we describe the use of a simple and efficient sol–gel solution method for synthesizing indium zinc oxide (IZO) films for use as semiconductor channel layers in thin-film transistors (TFTs) on p-type silicon substrates. The performance of IZO-based TFTs was investigated, and the effect of oxygen plasma treatment on the surface of dielectric SiN x was observed. Oxygen plasma treatment effectively enhanced the electron mobility in IZO-based TFT devices from 0.005 to 1.56 cm2 V‑1 s‑1, an increase of more than 312 times, and effectively enhanced device performance. X-ray photoelectron spectroscopy analysis of the IZO film was performed to clarify element bonding.

  19. Boosting the mobility and bias stability of oxide-based thin-film transistors with ultra-thin nanocrystalline InSnO:Zr layer

    NASA Astrophysics Data System (ADS)

    Raja, Jayapal; Jang, Kyungsoo; Hussain, Shahzada Qamar; Balaji, Nagarajan; Chatterjee, Somenath; Velumani, S.; Yi, Junsin

    2015-01-01

    Extensive attention on high-definition flat panel displays is the driving force to fabricate high-performance thin-film transistors (TFTs). A hybrid oxide TFTs fabricated using an interfacial layer of nanocrystalline Zr-doped InSnO (nc-ITO:Zr) and an amorphous InSnZnO films as an active channel is reported here. Due to the presence of nc-ITO:Zr layer, an improvement of the field-effect mobility (86.4 cm2/V.s) and threshold voltage (0.43 V) values for TFTs are observed. Positive gate bias stress study indicates the role of nc-ITO:Zr layer in fabricated TFTs through the suppression of charge trapping capability between the channel and insulating layer.

  20. Amorphous Indium Gallium Zinc Oxide Thin-Film Transistors with a Low-Temperature Polymeric Gate Dielectric on a Flexible Substrate

    NASA Astrophysics Data System (ADS)

    Hyung, Gun Woo; Park, Jaehoon; Wang, Jian-Xun; Lee, Ho Won; Li, Zhao-Hui; Koo, Ja-Ryong; Kwon, Sang Jik; Cho, Eou-Sik; Kim, Woo Young; Kim, Young Kwan

    2013-07-01

    Amorphous indium gallium zinc oxide (a-IGZO) thin-film transistors (TFTs) with a solution-processed polymeric gate dielectric of cross-linked poly(4-vinylphenol) (c-PVP) film were fabricated on a poly(ethylene terephthalate) (PET) substrate on which an a-IGZO film, as the active channel layer, was deposited by radio frequency (RF) sputtering. The entire TFT fabrication process was carried out at a temperature below 110 °C. The device exhibited an on/off ratio of 1.5×106 and a high field-effect mobility of 10.2 cm2 V-1 s-1, which is, to our knowledge, the best result ever achieved among a-IGZO TFTs with polymeric gate dielectrics on a plastic substrate.

  1. Optimization of a Solution-Processed SiO2 Gate Insulator by Plasma Treatment for Zinc Oxide Thin Film Transistors.

    PubMed

    Jeong, Yesul; Pearson, Christopher; Kim, Hyun-Gwan; Park, Man-Young; Kim, Hongdoo; Do, Lee-Mi; Petty, Michael C

    2016-01-27

    We report on the optimization of the plasma treatment conditions for a solution-processed silicon dioxide gate insulator for application in zinc oxide thin film transistors (TFTs). The SiO2 layer was formed by spin coating a perhydropolysilazane (PHPS) precursor. This thin film was subsequently thermally annealed, followed by exposure to an oxygen plasma, to form an insulating (leakage current density of ∼10(-7) A/cm(2)) SiO2 layer. Optimized ZnO TFTs (40 W plasma treatment of the gate insulator for 10 s) possessed a carrier mobility of 3.2 cm(2)/(V s), an on/off ratio of ∼10(7), a threshold voltage of -1.3 V, and a subthreshold swing of 0.2 V/decade. In addition, long-term exposure (150 min) of the pre-annealed PHPS to the oxygen plasma enabled the maximum processing temperature to be reduced from 180 to 150 °C. The resulting ZnO TFT exhibited a carrier mobility of 1.3 cm(2)/(V s) and on/off ratio of ∼10(7). PMID:26704352

  2. Reduction of defect formation in amorphous indium-gallium-zinc-oxide thin film transistors by N{sub 2}O plasma treatment

    SciTech Connect

    Jhu, Jhe-Ciou; Chang, Ting-Chang; Chang, Geng-Wei; Tai, Ya-Hsiang; Tsai, Wu-Wei; Chiang, Wen-Jen; Yan, Jing-Yi

    2013-11-28

    An abnormal sub-threshold leakage current is observed at high temperature in amorphous indium-gallium-zinc-oxide thin film transistors (a-IGZO TFTs). This phenomenon occurs due to a reduced number of defects in the device's a-IGZO active layer after the device has undergone N{sub 2}O plasma treatment. Experimental verification shows that the N{sub 2}O plasma treatment enhances the thin film bonding strength, thereby suppressing the formation of temperature-dependent holes, which are generated above 400 K by oxygen atoms leaving their original sites. The N{sub 2}O plasma treatment devices have better stability performance than as-fabricated devices. The results suggest that the density of defects for a-IGZO TFTs with N{sub 2}O plasma treatment is much lower than that in as-fabricated devices. The N{sub 2}O plasma treatment repairs the defects and suppresses temperature-dependent sub-threshold leakage current.

  3. High-mobility solution-processed tin oxide thin-film transistors with high-κ alumina dielectric working in enhancement mode.

    PubMed

    Huang, Genmao; Duan, Lian; Dong, Guifang; Zhang, Deqiang; Qiu, Yong

    2014-12-10

    Solution-processed metal oxide thin-film transistors (TFTs) operating in enhancement mode are promising for the next-generation flat panel displays. In this work, we report high-mobility TFTs based on SnO2 active layer derived from a soluble tin(II) 2-ethylhexanoate precursor. Densely packed polycrystalline SnO2 thin films with moderate oxygen vacancies and only a few hydroxides are obtained via systemically optimizing precursor concentrations and processing conditions. The utilization of a solution-processed high-κ Al2O3 insulating layer could generate a coherent dielectric/semiconductor interface, hence further improving the device performance. TFT devices with an average field-effect mobility of 96.4 cm(2) V(-1) s(-1), a current on/off ratio of 2.2 × 10(6), a threshold voltage of 1.72 V, and a subthreshold swing of 0.26 V dec(-1) have been achieved, and the driving capability is demonstrated by implementing a single SnO2 TFT device to tune the brightness of an organic light-emitting diode. It is worth noting that these TFTs work in enhancement mode at low voltages less than 4 V, which sheds light on their potential application to the next-generation low-cost active matrix flat panel displays. PMID:25375760

  4. Impact of the cation composition on the electrical performance of solution-processed zinc tin oxide thin-film transistors.

    PubMed

    Kim, Yoon Jang; Oh, Seungha; Yang, Bong Seob; Han, Sang Jin; Lee, Hong Woo; Kim, Hyuk Jin; Jeong, Jae Kyeong; Hwang, Cheol Seong; Kim, Hyeong Joon

    2014-08-27

    This study examined the structural, chemical, and electrical properties of solution-processed (Zn,Sn)O3 (ZTO) films with various Sn/[Zn+Sn] ratios for potential applications to large-area flat panel displays. ZTO films with a Zn-rich composition had a polycrystalline wurtzite structure. On the other hand, the Sn-rich ZTO films exhibited a rutile structure, where the Zn atom was speculated to replace the Sn site, thereby acting as an acceptor. In the intermediate composition regions (Sn/[Zn+Sn] ratio from 0.28 to 0.48), the ZTO films had an amorphous structure, even after annealing at 450 °C. The electrical transport properties and photobias stability of ZTO thin film transistors (TFTs) were also examined according to the Sn/[Zn+Sn] ratio. The optimal transport property of ZTO TFT was observed for the device with an amorphous structure at a Sn/[Zn+Sn] ratio of 0.48. The mobility, threshold voltage, subthreshold swing, and on/off current ratio were 4.3 cm(2)/(V s), 0 V, 0.4 V/decade, and 4.1 × 10(7), respectively. In contrast, the device performance for the ZTO TFTs with either a higher or lower Sn concentration suffered from low mobility and a high off-state current, respectively. The photoelectrical stress measurements showed that the photobias stability of the ZTO TFTs was improved substantially when the ZTO semiconducting films had a lower oxygen vacancy concentration and an amorphous structure. The relevant rationale is discussed based on the phototransition and subsequent migration mechanism from neutral to positively charged oxygen vacancies. PMID:25090286

  5. Method for double-sided processing of thin film transistors

    DOEpatents

    Yuan, Hao-Chih; Wang, Guogong; Eriksson, Mark A.; Evans, Paul G.; Lagally, Max G.; Ma, Zhenqiang

    2008-04-08

    This invention provides methods for fabricating thin film electronic devices with both front- and backside processing capabilities. Using these methods, high temperature processing steps may be carried out during both frontside and backside processing. The methods are well-suited for fabricating back-gate and double-gate field effect transistors, double-sided bipolar transistors and 3D integrated circuits.

  6. Organic thin film transistors: from active materials to novel applications

    NASA Astrophysics Data System (ADS)

    Torsi, L.; Cioffi, N.; Di Franco, C.; Sabbatini, L.; Zambonin, P. G.; Bleve-Zacheo, T.

    2001-08-01

    In this paper, a bird's eye view of most of the organic materials employed as n-channel and p-channel transistor active layers is given along with the relevant device performances; organic thin film transistors (OTFT) operation regimes are discussed and an interesting perspective application of OTFT as multi-parameter gas sensor is proposed.

  7. Highly stable thin film transistors using multilayer channel structure

    SciTech Connect

    Nayak, Pradipta K.; Wang, Zhenwei; Anjum, D. H.; Hedhili, M. N.; Alshareef, H. N.

    2015-03-09

    We report highly stable gate-bias stress performance of thin film transistors (TFTs) using zinc oxide (ZnO)/hafnium oxide (HfO{sub 2}) multilayer structure as the channel layer. Positive and negative gate-bias stress stability of the TFTs was measured at room temperature and at 60 °C. A tremendous improvement in gate-bias stress stability was obtained in case of the TFT with multiple layers of ZnO embedded between HfO{sub 2} layers compared to the TFT with a single layer of ZnO as the semiconductor. The ultra-thin HfO{sub 2} layers act as passivation layers, which prevent the adsorption of oxygen and water molecules in the ZnO layer and hence significantly improve the gate-bias stress stability of ZnO TFTs.

  8. Highly Reliable Liquid-Phase-Deposited SiO2 with Nitrous Oxide Plasma Post-Treatment for Low-Temperature-Processed Polysilicon Thin Film Transistors

    NASA Astrophysics Data System (ADS)

    Yeh, Ching-Fa; Chen, Darren Chi-Hsiang; Lu, Cheng-Yu; Liu, Chung; Lee, Su-Tseng; Liu, Cheng-Hong; Chen, Tai-Ju

    2002-10-01

    Low-temperature (˜300°C) N2O-plasma post-treatment for liquid-phase-deposited (LPD) gate oxide has been proposed for the first time. This treatment successfully takes the place of conventional furnace annealing in O2 ambient. Results of physicochemical and electrical characteristics show that N2O-plasma post-treated LPD-SiO2 has a high electrical breakdown field and low interface state density. In addition, N2O-plasma treatment also improves the Si-rich phenomenon of LPD-SiO2. From the comparison with pure N2O-plasma oxidation film, LPD-SiO2 with its short re-oxidation time in N2O plasma plays an important role in relieving interfacial stress. Finally, the novel technology is applied to the gate oxide of low-temperature-processed (LTP) polysilicon thin film transistors (poly-Si TFTs). The device performance reveals excellent electrical characteristics, and the reliability shows a satisfactory result, as well as the gate oxide reliability. It is believed that the N2O-plasma post-treatment not only improves the oxide quality, but also effectively passivates the trap states of poly-Si TFTs.

  9. Lateral protonic/electronic hybrid oxide thin-film transistor gated by SiO{sub 2} nanogranular films

    SciTech Connect

    Zhu, Li Qiang Chao, Jin Yu; Xiao, Hui

    2014-12-15

    Ionic/electronic interaction offers an additional dimension in the recent advancements of condensed materials. Here, lateral gate control of conductivities of indium-zinc-oxide (IZO) films is reported. An electric-double-layer (EDL) transistor configuration was utilized with a phosphorous-doped SiO{sub 2} nanogranular film to provide a strong lateral electric field. Due to the strong lateral protonic/electronic interfacial coupling effect, the IZO EDL transistor could operate at a low-voltage of 1 V. A resistor-loaded inverter is built, showing a high voltage gain of ∼8 at a low supply voltage of 1 V. The lateral ionic/electronic coupling effects are interesting for bioelectronics and portable electronics.

  10. Lateral protonic/electronic hybrid oxide thin-film transistor gated by SiO2 nanogranular films

    NASA Astrophysics Data System (ADS)

    Zhu, Li Qiang; Chao, Jin Yu; Xiao, Hui

    2014-12-01

    Ionic/electronic interaction offers an additional dimension in the recent advancements of condensed materials. Here, lateral gate control of conductivities of indium-zinc-oxide (IZO) films is reported. An electric-double-layer (EDL) transistor configuration was utilized with a phosphorous-doped SiO2 nanogranular film to provide a strong lateral electric field. Due to the strong lateral protonic/electronic interfacial coupling effect, the IZO EDL transistor could operate at a low-voltage of 1 V. A resistor-loaded inverter is built, showing a high voltage gain of ˜8 at a low supply voltage of 1 V. The lateral ionic/electronic coupling effects are interesting for bioelectronics and portable electronics.

  11. Polysilicon thin film transistors fabricated on low temperature plastic substrates

    SciTech Connect

    Carey, P.G.; Smith, P.M.; Theiss, S.D.; Wickboldt, P.

    1999-07-01

    We present device results from polysilicon thin film transistors (TFTs) fabricated at a maximum temperature of 100&hthinsp;{degree}C on polyester substrates. Critical to our success has been the development of a processing cluster tool containing chambers dedicated to laser crystallization, dopant deposition, and gate oxidation. Our TFT fabrication process integrates multiple steps in this tool, and uses the laser to crystallize deposited amorphous silicon as well as create heavily doped TFT source/drain regions. By combining laser crystallization and doping, a plasma enhanced chemical vapor deposition SiO{sub 2} layer for the gate dielectric, and postfabrication annealing at 150&hthinsp;{degree}C, we have succeeded in fabricating TFTs with I{sub ON}/I{sub OFF} ratios {gt}5{times}10{sup 5} and electron mobilities {gt}40 cm{sup 2}/V&hthinsp;s on polyester substrates. {copyright} {ital 1999 American Vacuum Society.}

  12. Contact resistance and overlapping capacitance in flexible sub-micron long oxide thin-film transistors for above 100 MHz operation

    NASA Astrophysics Data System (ADS)

    Münzenrieder, Niko; Salvatore, Giovanni A.; Petti, Luisa; Zysset, Christoph; Büthe, Lars; Vogt, Christian; Cantarella, Giuseppe; Tröster, Gerhard

    2014-12-01

    In recent years new forms of electronic devices such as electronic papers, flexible displays, epidermal sensors, and smart textiles have become reality. Thin-film transistors (TFTs) are the basic blocks of the circuits used in such devices and need to operate above 100 MHz to efficiently treat signals in RF systems and address pixels in high resolution displays. Beyond the choice of the semiconductor, i.e., silicon, graphene, organics, or amorphous oxides, the junctionless nature of TFTs and its geometry imply some limitations which become evident and important in devices with scaled channel length. Furthermore, the mechanical instability of flexible substrates limits the feature size of flexible TFTs. Contact resistance and overlapping capacitance are two parasitic effects which limit the transit frequency of transistors. They are often considered independent, while a deeper analysis of TFTs geometry imposes to handle them together; in fact, they both depend on the overlapping length (LOV) between source/drain and the gate contacts. Here, we conduct a quantitative analysis based on a large number of flexible ultra-scaled IGZO TFTs. Devices with three different values of overlap length and channel length down to 0.5 μm are fabricated to experimentally investigate the scaling behavior of the transit frequency. Contact resistance and overlapping capacitance depend in opposite ways on LOV. These findings establish routes for the optimization of the dimension of source/drain contact pads and suggest design guidelines to achieve megahertz operation in flexible IGZO TFTs and circuits.

  13. Low-temperature, solution-processed indium-oxide thin-film transistors fabricated by using an ultraviolet-ozone treatment

    NASA Astrophysics Data System (ADS)

    Kim, Hoon; Kang, Chan-mo; Oh, Yeon-Wha; Ryu, Jin Hwa; Baek, Kyu-Ha; Do, Lee-Mi

    2016-04-01

    For the fabrication of low-temperature solution-processed metal-oxide thin-film transistors (TFTs), alternative annealing processes have recently been studied for reduced fabrication cost and applications to flexible devices. Indium nitrate solution has been proposed as a precursor for the low-temperature solution-processed TFTs. However, due to its high decomposition temperature, achieving a high-performance indium-oxide (In2O3) TFT at temperatures below 200°C is still difficult. In this study, for improved metal-oxide formation in low-temperature solution-processed In2O3 TFT, indium nitrate film was exposed to UV-ozone for 30 min before annealing at 200°C. The smooth scanning electron microscopy (SEM) image of the UV-ozone treated film implies that the indium nitrates are condensed after treatment. In addition, X-ray photoemission spectroscopy (XPS) data suggest that UV-ozone decreases the number of oxygen vacancies and increases the number of metal-oxygen-metal bonds in the indium-oxide films. As a result, high electrical device performance was achieved with an improved Ion/off ratio (˜107) and mobility (1.25 cm2V -1s -1).

  14. Zinc oxide thin film acoustic sensor

    SciTech Connect

    Mohammed, Ali Jasim; Salih, Wafaa Mahdi; Hassan, Marwa Abdul Muhsien; Nusseif, Asmaa Deiaa; Kadhum, Haider Abdullah; Mansour, Hazim Louis

    2013-12-16

    This paper reports the implementation of (750 nm) thickness of Zinc Oxide (ZnO) thin film for the piezoelectric pressure sensors. The film was prepared and deposited employing the spray pyrolysis technique. XRD results show that the growth preferred orientation is the (002) plane. A polycrystalline thin film (close to mono crystallite like) was obtained. Depending on the Scanning Electron Microscopy photogram, the film homogeneity and thickness were shown. The resonance frequency measured (about 19 kHz) and the damping coefficient was calculated and its value was found to be about (2.5538), the thin film be haves as homogeneous for under and over damped. The thin film pressure sensing was approximately exponentially related with frequency, the thin film was observed to has a good response for mechanical stresses also it is a good material for the piezoelectric properties.

  15. Zinc oxide thin film acoustic sensor

    NASA Astrophysics Data System (ADS)

    Mohammed, Ali Jasim; Salih, Wafaa Mahdi; Hassan, Marwa Abdul Muhsien; Mansour, Hazim Louis; Nusseif, Asmaa Deiaa; Kadhum, Haider Abdullah

    2013-12-01

    This paper reports the implementation of (750 nm) thickness of Zinc Oxide (ZnO) thin film for the piezoelectric pressure sensors. The film was prepared and deposited employing the spray pyrolysis technique. XRD results show that the growth preferred orientation is the (002) plane. A polycrystalline thin film (close to mono crystallite like) was obtained. Depending on the Scanning Electron Microscopy photogram, the film homogeneity and thickness were shown. The resonance frequency measured (about 19 kHz) and the damping coefficient was calculated and its value was found to be about (2.5538), the thin film be haves as homogeneous for under and over damped. The thin film pressure sensing was approximately exponentially related with frequency, the thin film was observed to has a good response for mechanical stresses also it is a good material for the piezoelectric properties.

  16. Improvement of bias-stability in amorphous-indium-gallium-zinc-oxide thin-film transistors by using solution-processed Y2O3 passivation

    NASA Astrophysics Data System (ADS)

    An, Sungjin; Mativenga, Mallory; Kim, Youngoo; Jang, Jin

    2014-08-01

    We demonstrate back channel improvement of back-channel-etch amorphous-indium-gallium-zinc-oxide (a-IGZO) thin-film transistors by using solution-processed yttrium oxide (Y2O3) passivation. Two different solvents, which are acetonitrile (35%) + ethylene glycol (65%), solvent A and deionized water, solvent B are investigated for the spin-on process of the Y2O3 passivation—performed after patterning source/drain (S/D) Mo electrodes by a conventional HNO3-based wet-etch process. Both solvents yield devices with good performance but those passivated by using solvent B exhibit better light and bias stability. Presence of yttrium at the a-IGZO back interface, where it occupies metal vacancy sites, is confirmed by X-ray photoelectron spectroscopy. The passivation effect of yttrium is more significant when solvent A is used because of the existence of more metal vacancies, given that the alcohol (65% ethylene glycol) in solvent A may dissolve the metal oxide (a-IGZO) through the formation of alkoxides and water.

  17. A review of carbon nanotube- and graphene-based flexible thin-film transistors.

    PubMed

    Sun, Dong-Ming; Liu, Chang; Ren, Wen-Cai; Cheng, Hui-Ming

    2013-04-22

    Carbon nanotubes (CNTs) and graphene have attracted great attention for numerous applications for future flexible electronics, owing to their supreme properties including exceptionally high electronic conductivity and mechanical strength. Here, the progress of CNT- and graphene-based flexible thin-film transistors from material preparation, device fabrication techniques to transistor performance control is reviewed. State-of-the-art fabrication techniques of thin-film transistors are divided into three categories: solid-phase, liquid-phase, and gas-phase techniques, and possible scale-up approaches to achieve realistic production of flexible nanocarbon-based transistors are discussed. In particular, the recent progress in flexible all-carbon nanomaterial transistor research is highlighted, and this all-carbon strategy opens up a perspective to realize extremely flexible, stretchable, and transparent electronics with a relatively low-cost and fast fabrication technique, compared to traditional rigid silicon, metal and metal oxide electronics. PMID:23519953

  18. Polycrystalline organic thin film transistors for advanced chemical sensing

    NASA Astrophysics Data System (ADS)

    Torsi, Luisa; Tanese, Maria C.; Cioffi, Nicola; Sabbatini, Luigia; Zambonin, Pier G.

    2003-11-01

    Organic thin-film transistors have seen a dramatic improvement of their performance in the last decade. They have been also proposed as gas sensors. This paper deals with the interesting new aspects that polycrystalline based conducting polymer transistors present when operated as chemical sensors. Such devices are capable to deliver multi-parameter responses that are also extremely repeatable and fast at room temperature. Interesting are also the perspectives for their use as chemically selective devices in array type sensing systems.

  19. Amorphous indium-tin-zinc oxide films deposited by magnetron sputtering with various reactive gases: Spatial distribution of thin film transistor performance

    SciTech Connect

    Jia, Junjun; Torigoshi, Yoshifumi; Shigesato, Yuzo; Kawashima, Emi; Utsuno, Futoshi; Yano, Koki

    2015-01-12

    This work presents the spatial distribution of electrical characteristics of amorphous indium-tin-zinc oxide film (a-ITZO), and how they depend on the magnetron sputtering conditions using O{sub 2}, H{sub 2}O, and N{sub 2}O as the reactive gases. Experimental results show that the electrical properties of the N{sub 2}O incorporated a-ITZO film has a weak dependence on the deposition location, which cannot be explained by the bombardment effect of high energy particles, and may be attributed to the difference in the spatial distribution of both the amount and the activity of the reactive gas reaching the substrate surface. The measurement for the performance of a-ITZO thin film transistor (TFT) also suggests that the electrical performance and device uniformity of a-ITZO TFTs can be improved significantly by the N{sub 2}O introduction into the deposition process, where the field mobility reach to 30.8 cm{sup 2} V{sup –1} s{sup –1}, which is approximately two times higher than that of the amorphous indium-gallium-zinc oxide TFT.

  20. High-pressure Gas Activation for Amorphous Indium-Gallium-Zinc-Oxide Thin-Film Transistors at 100 °C

    NASA Astrophysics Data System (ADS)

    Kim, Won-Gi; Tak, Young Jun; Du Ahn, Byung; Jung, Tae Soo; Chung, Kwun-Bum; Kim, Hyun Jae

    2016-03-01

    We investigated the use of high-pressure gases as an activation energy source for amorphous indium-gallium-zinc-oxide (a-IGZO) thin film transistors (TFTs). High-pressure annealing (HPA) in nitrogen (N2) and oxygen (O2) gases was applied to activate a-IGZO TFTs at 100 °C at pressures in the range from 0.5 to 4 MPa. Activation of the a-IGZO TFTs during HPA is attributed to the effect of the high-pressure environment, so that the activation energy is supplied from the kinetic energy of the gas molecules. We reduced the activation temperature from 300 °C to 100 °C via the use of HPA. The electrical characteristics of a-IGZO TFTs annealed in O2 at 2 MPa were superior to those annealed in N2 at 4 MPa, despite the lower pressure. For O2 HPA under 2 MPa at 100 °C, the field effect mobility and the threshold voltage shift under positive bias stress were improved by 9.00 to 10.58 cm2/V.s and 3.89 to 2.64 V, respectively. This is attributed to not only the effects of the pressurizing effect but also the metal-oxide construction effect which assists to facilitate the formation of channel layer and reduces oxygen vacancies, served as electron trap sites.

  1. Solution-processed lithium-doped zinc oxide thin-film transistors at low temperatures between 100 and 300 °C

    NASA Astrophysics Data System (ADS)

    Liu, Fangmei; Qian, Chuan; Sun, Jia; Liu, Peng; Huang, Yulan; Gao, Yongli; Yang, Junliang

    2016-04-01

    Lithium-doped zinc oxide (Li-ZnO) thin-film transistors (TFTs) were fabricated by solution process at the low temperatures ranged from 100 to 300 °C. Li-ZnO TFTs fabricated at 300 °C under nitrogen condition showed a mobility of 1.2 cm2/Vs. Most importantly, the mobility of Li-ZnO TFT devices fabricated at 100 °C could be increased significantly from 0.08 to 0.4 cm2/Vs by using double spin-coated and UV irradiation-treated Li-ZnO film, and the on-/off-current ratio is in the order of 106. Notably, the XPS analyses proved that the performance improvement was originated from the chemical composition or stoichiometry evolution, in which the hydroxide was converted into metal oxide and accelerated the formation of the oxygen vacancies. Furthermore, low-voltage operating Li-ZnO TFTs were demonstrated by using a high-capacitance ion gel gate dielectrics. The Li-ZnO TFTs with an operating voltage as low as 2 V exhibited the carrier mobilities of 2.1 and 0.65 cm2/Vs for the devices treated at 300 and 100 °C, respectively. The low-temperature, solution-processed Li-ZnO TFTs showed greatly potential applications in flexible displays, smart label, and sensors.

  2. Polycrystalline silicon thin-film transistor with nickel-titanium oxide by sol-gel spin-coating and nitrogen implantation

    NASA Astrophysics Data System (ADS)

    Wu, Shih-Chieh; Hou, Tuo-Hung; Chuang, Shiow-Huey; Chou, Hsin-Chih; Chao, Tien-Sheng; Lei, Tan-Fu

    2012-12-01

    This study demonstrates polycrystalline silicon thin-film transistors (poly-Si TFTs) integrated with a high-κ nickel-titanium oxide (NiTiO3) gate dielectric using sol-gel spin-coating and nitrogen channel implantation. This novel fabrication method of the high-κ NiTiO3 gate dielectric offers thin equivalent-oxide thickness and high gate capacitance density, favorable for increasing the current driving capability. Introducing nitrogen ions into the poly-Si using implantation effectively passivates the trap states not only in the poly-Si channel but also at the gate dielectric/poly-Si interface. The poly-Si NiTiO3 TFTs with nitrogen implantation exhibit significantly improved electrical characteristics, including lower threshold voltage, a steeper subthreshold swing, higher field-effect mobility, a larger on/off current ratio, and less threshold-voltage roll-off. Furthermore, the nitrogen implantation improves the reliability of poly-Si NiTiO3 TFTs against hot-carrier stress and positive bias temperature instability.

  3. High-performance single-crystalline arsenic-doped indium oxide nanowires for transparent thin-film transistors and active matrix organic light-emitting diode displays.

    PubMed

    Chen, Po-Chiang; Shen, Guozhen; Chen, Haitian; Ha, Young-geun; Wu, Chao; Sukcharoenchoke, Saowalak; Fu, Yue; Liu, Jun; Facchetti, Antonio; Marks, Tobin J; Thompson, Mark E; Zhou, Chongwu

    2009-11-24

    We report high-performance arsenic (As)-doped indium oxide (In(2)O(3)) nanowires for transparent electronics, including their implementation in transparent thin-film transistors (TTFTs) and transparent active-matrix organic light-emitting diode (AMOLED) displays. The As-doped In(2)O(3) nanowires were synthesized using a laser ablation process and then fabricated into TTFTs with indium-tin oxide (ITO) as the source, drain, and gate electrodes. The nanowire TTFTs on glass substrates exhibit very high device mobilities (approximately 1490 cm(2) V(-1) s(-1)), current on/off ratios (5.7 x 10(6)), steep subthreshold slopes (88 mV/dec), and a saturation current of 60 microA for a single nanowire. By using a self-assembled nanodielectric (SAND) as the gate dielectric, the device mobilities and saturation current can be further improved up to 2560 cm(2) V(-1) s(-1) and 160 microA, respectively. All devices exhibit good optical transparency (approximately 81% on average) in the visible spectral range. In addition, the nanowire TTFTs were utilized to control green OLEDs with varied intensities. Furthermore, a fully integrated seven-segment AMOLED display was fabricated with a good transparency of 40% and with each pixel controlled by two nanowire transistors. This work demonstrates that the performance enhancement possible by combining nanowire doping and self-assembled nanodielectrics enables silicon-free electronic circuitry for low power consumption, optically transparent, high-frequency devices assembled near room temperature. PMID:19842677

  4. Hysteresis free carbon nanotube thin film transistors comprising hydrophobic dielectrics

    NASA Astrophysics Data System (ADS)

    Lefebvre, J.; Ding, J.; Li, Z.; Cheng, F.; Du, N.; Malenfant, P. R. L.

    2015-12-01

    We present two examples of carbon nanotube network thin film transistors with strongly hydrophobic dielectrics comprising either Teflon-AF or a poly(vinylphenol)/poly(methyl silsesquioxane) (PVP/pMSSQ) blend. In the absence of encapsulation, bottom gated transistors in air ambient show no hysteresis between forward and reverse gate sweep direction. Device threshold gate voltage and On-current present excellent time dependent stability even under dielectric stress. Furthermore, threshold gate voltage for hole conduction is negative upon device encapsulation with PVP/pMSSQ enabling much improved current On/Off ratio at 0 V. This work addresses two major challenges impeding solution based fabrication of relevant thin film transistors with printable single-walled carbon nanotube channels.

  5. Improving source/drain contact resistance of amorphous indium–gallium–zinc-oxide thin-film transistors using an n+-ZnO buffer layer

    NASA Astrophysics Data System (ADS)

    Hung, Chien-Hsiung; Wang, Shui-Jinn; Lin, Chieh; Wu, Chien-Hung; Chen, Yen-Han; Liu, Pang-Yi; Tu, Yung-Chun; Lin, Tseng-Hsing

    2016-06-01

    To avoid high temperature annealing in improving the source/drain (S/D) resistance (R DS) of amorphous indium–gallium–zinc-oxide (α-IGZO) thin-film transistors (TFTs) for flexible electronics, a simple and efficient technique using a sputtering-deposited n+-ZnO buffer layer (BL) sandwiched between the S/D electrode and the α-IGZO channel is proposed and demonstrated. It shows that the R DS of α-IGZO TFTs with the proposed n+-ZnO BL is reduced to 8.1 × 103 Ω as compared with 6.1 × 104 Ω of the conventional one. The facilitation of carrier tunneling between the S/D electrode and the α-IGZO channel through the use of the n+-ZnO BL to lower the effective barrier height therein is responsible for the R DS reduction. Effects of the chamber pressure on the carrier concentration of the sputtering-deposited n+-ZnO BL and the thickness of the BL on the degree of improvement in the performance of α-IGZO TFTs are analyzed and discussed.

  6. Improvement in reliability of amorphous indium-gallium-zinc oxide thin-film transistors with Teflon/SiO2 bilayer passivation under gate bias stress

    NASA Astrophysics Data System (ADS)

    Fan, Ching-Lin; Tseng, Fan-Ping; Li, Bo-Jyun; Lin, Yu-Zuo; Wang, Shea-Jue; Lee, Win-Der; Huang, Bohr-Ran

    2016-02-01

    The reliability of amorphous indium-gallium-zinc oxide (a-IGZO) thin-film transistors (TFTs) with Teflon/SiO2 bilayer passivation prepared under positive and negative gate bias stresses (PGBS and NGBS, respectively) was investigated. Heavier electrical degradation was observed under PGBS than under NGBS, indicating that the environmental effects under PGBS are more evident than those under NGBS. The device with bilayer passivation under PGBS shows two-step degradation. The positive threshold voltage shifts during the initial stressing period (before 500 s), owing to the charges trapped in the gate insulator or at the gate insulator/a-IGZO active layer interface. The negative threshold voltage shift accompanies the increase in subthreshold swing (SS) for the continuous stressing period (after 500 s) owing to H2O molecules from ambience diffused within the a-IGZO TFTs. It is believed that Teflon/SiO2 bilayer passivation can effectively improve the reliability of the a-IGZO TFTs without passivation even though the devices are stressed under gate bias.

  7. Effect of top gate bias on photocurrent and negative bias illumination stress instability in dual gate amorphous indium-gallium-zinc oxide thin-film transistor

    NASA Astrophysics Data System (ADS)

    Lee, Eunji; Chowdhury, Md Delwar Hossain; Park, Min Sang; Jang, Jin

    2015-12-01

    We have studied the effect of top gate bias (VTG) on the generation of photocurrent and the decay of photocurrent for back channel etched inverted staggered dual gate structure amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film-transistors. Upon 5 min of exposure of 365 nm wavelength and 0.7 mW/cm2 intensity light with negative bottom gate bias, the maximum photocurrent increases from 3.29 to 322 pA with increasing the VTG from -15 to +15 V. By changing VTG from negative to positive, the Fermi level (EF) shifts toward conduction band edge (EC), which substantially controls the conversion of neutral vacancy to charged one (VO → VO+/VO2+ + e-/2e-), peroxide (O22-) formation or conversion of ionized interstitial (Oi2-) to neutral interstitial (Oi), thus electron concentration at conduction band. With increasing the exposure time, more carriers are generated, and thus, maximum photocurrent increases until being saturated. After negative bias illumination stress, the transfer curve shows -2.7 V shift at VTG = -15 V, which gradually decreases to -0.42 V shift at VTG = +15 V. It clearly reveals that the position of electron quasi-Fermi level controls the formation of donor defects (VO+/VO2+/O22-/Oi) and/or hole trapping in the a-IGZO /interfaces.

  8. Effect of top gate potential on bias-stress for dual gate amorphous indium-gallium-zinc-oxide thin film transistor

    NASA Astrophysics Data System (ADS)

    Chun, Minkyu; Um, Jae Gwang; Park, Min Sang; Chowdhury, Md Delwar Hossain; Jang, Jin

    2016-07-01

    We report the abnormal behavior of the threshold voltage (VTH) shift under positive bias Temperature stress (PBTS) and negative bias temperature stress (NBTS) at top/bottom gate in dual gate amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistors (TFTs). It is found that the PBTS at top gate shows negative transfer shift and NBTS shows positive transfer shift for both top and bottom gate sweep. The shift of bottom/top gate sweep is dominated by top gate bias (VTG), while bottom gate bias (VBG) is less effect than VTG. The X-ray photoelectron spectroscopy (XPS) depth profile provides the evidence of In metal diffusion to the top SiO2/a-IGZO and also the existence of large amount of In+ under positive top gate bias around top interfaces, thus negative transfer shift is observed. On the other hand, the formation of OH- at top interfaces under the stress of negative top gate bias shows negative transfer shift. The domination of VTG both on bottom/top gate sweep after PBTS/NBTS is obviously occurred due to thin active layer.

  9. Damage-free back channel wet-etch process in amorphous indium-zinc-oxide thin-film transistors using a carbon-nanofilm barrier layer.

    PubMed

    Luo, Dongxiang; Zhao, Mingjie; Xu, Miao; Li, Min; Chen, Zikai; Wang, Lang; Zou, Jianhua; Tao, Hong; Wang, Lei; Peng, Junbiao

    2014-07-23

    Amorphous indium-zinc-oxide thin film transistors (IZO-TFTs) with damage-free back channel wet-etch (BCE) process were investigated. A carbon (C) nanofilm was inserted into the interface between IZO layer and source/drain (S/D) electrodes as a barrier layer. Transmittance electron microscope images revealed that the 3 nm-thick C nanofilm exhibited a good corrosion resistance to a commonly used H3PO4-based etchant and could be easily eliminated. The TFT device with a 3 nm-thick C barrier layer showed a saturated field effect mobility of 14.4 cm(2) V(-1) s(-1), a subthreshold swing of 0.21 V/decade, an on-to-off current ratio of 8.3 × 10(10), and a threshold voltage of 2.0 V. The favorable electrical performance of this kind of IZO-TFTs was due to the protection of the inserted C to IZO layer in the back-channel-etch process. Moreover, the low contact resistance of the devices was proved to be due to the graphitization of the C nanofilms after annealing. In addition, the hysteresis and thermal stress testing confirmed that the usage of C barrier nanofilms is an effective method to fabricate the damage-free BCE-type devices with high reliability. PMID:24969359

  10. Thin film hydrous metal oxide catalysts

    DOEpatents

    Dosch, Robert G.; Stephens, Howard P.

    1995-01-01

    Thin film (<100 nm) hydrous metal oxide catalysts are prepared by 1) synthesis of a hydrous metal oxide, 2) deposition of the hydrous metal oxide upon an inert support surface, 3) ion exchange with catalytically active metals, and 4) activating the hydrous metal oxide catalysts.

  11. Synthesis of ZnO nanowires for thin film network transistors

    NASA Astrophysics Data System (ADS)

    Dalal, S. H.; Unalan, H. E.; Zhang, Y.; Hiralal, Pritesh; Gangloff, L.; Flewitt, Andrew J.; Amaratunga, Gehan A. J.; Milne, William I.

    2008-08-01

    Zinc oxide nanowire networks are attractive as alternatives to organic and amorphous semiconductors due to their wide bandgap, flexibility and transparency. We demonstrate the fabrication of thin film transistors (TFT)s which utilize ZnO nanowires as the semiconducting channel. These thin film transistors can be transparent and flexible and processed at low temperatures on to a variety of substrates. The nanowire networks are created using a simple contact transfer method that is easily scalable. Apparent nanowire network mobility values can be as high as 3.8 cm2/Vs (effective thin film mobility: 0.03 cm2/Vs) in devices with 20μm channel lengths and ON/OFF ratios of up to 104.

  12. High performance small-molecule organic thin film transistors

    NASA Astrophysics Data System (ADS)

    Kuo, Chung-Chen

    The roadmap of developing microelectronics has a new branch: organic electronics. Organic electronics, which utilizes the electrical properties of organic materials in the active or passive layers, is an emerging technology that has received much attention. In conjunction with today's demands for new materials and devices, many technologies have emerged for developing organic electronics and consolidating applications and markets. An organic thin-film transistor is the essential device in this paradigm in addition to organic photodiodes and organic light emitting diodes. This thesis presents advances made in design and fabrication of organic thin-film transistors (OTFTs) using small-molecule organic semiconductors (pentacene, anthradithiophene, and their derivatives) as the active layer with record device performance. In this work OTFT test structures fabricated on oxidized silicon substrates were utilized to provide a convenient substrate, gate contact, and gate insulator for the processing and characterization of vapor-deposited organic materials and their transistors. By developing a gate dielectric treatment using silane coupling agents the performance and yield of pentacene OTFTs was improved and a field-effect mobility of larger than 2 cm2/V-s was achieved. Such device performance is comparable to a-Si:H TFTs and have the potential for electronic applications. In addition, the first direct photolithographic process for top contacts to pentacene OTFTs on oxidized silicon with an acceptable performance (a field-effect mobility of 0.3 cm2/V-s, an on/off current ratio of 10 7, and a subthreshold slope of 1 V/decade) was developed. The multiple layer photoresist process demonstrated the feasibility of creating source and drain metallic electrodes on vapor-deposited pentacene thin films with a resolution less than 10 mum. Subsequently, solution-processed OTFTs were then investigated and high performance transistors, with field-effect mobilities > 1 cm2/V-s and an

  13. Contact resistance and overlapping capacitance in flexible sub-micron long oxide thin-film transistors for above 100 MHz operation

    SciTech Connect

    Münzenrieder, Niko Salvatore, Giovanni A.; Petti, Luisa; Zysset, Christoph; Büthe, Lars; Vogt, Christian; Cantarella, Giuseppe; Tröster, Gerhard

    2014-12-29

    In recent years new forms of electronic devices such as electronic papers, flexible displays, epidermal sensors, and smart textiles have become reality. Thin-film transistors (TFTs) are the basic blocks of the circuits used in such devices and need to operate above 100 MHz to efficiently treat signals in RF systems and address pixels in high resolution displays. Beyond the choice of the semiconductor, i.e., silicon, graphene, organics, or amorphous oxides, the junctionless nature of TFTs and its geometry imply some limitations which become evident and important in devices with scaled channel length. Furthermore, the mechanical instability of flexible substrates limits the feature size of flexible TFTs. Contact resistance and overlapping capacitance are two parasitic effects which limit the transit frequency of transistors. They are often considered independent, while a deeper analysis of TFTs geometry imposes to handle them together; in fact, they both depend on the overlapping length (L{sub OV}) between source/drain and the gate contacts. Here, we conduct a quantitative analysis based on a large number of flexible ultra-scaled IGZO TFTs. Devices with three different values of overlap length and channel length down to 0.5 μm are fabricated to experimentally investigate the scaling behavior of the transit frequency. Contact resistance and overlapping capacitance depend in opposite ways on L{sub OV}. These findings establish routes for the optimization of the dimension of source/drain contact pads and suggest design guidelines to achieve megahertz operation in flexible IGZO TFTs and circuits.

  14. Indium tin oxide/InGaZnO bilayer stacks for enhanced mobility and optical stability in amorphous oxide thin film transistors

    SciTech Connect

    Chung, Yoon Jang; Kim, Un Ki; Hwang, Eun Suk; Hwang, Cheol Seong

    2014-07-07

    Optically more stable, high mobility InGaZnO thin film transistors were fabricated by implementing ultrathin In{sub 2}O{sub 3}-SnO{sub 2} (ITO) layers at the gate dielectric/semiconductor interface. The optimized device portrayed a high saturation mobility of ∼80 cm{sup 2}/V s with off current values lower than 10{sup −11}A. The ITO layer also acted as a hole filter layer, and hole current and threshold voltage shift values measured under negative bias illumination conditions showed that a significant amount of photo-generated charge carriers were annihilated before reaching the gate insulator. This effect was more evident at larger intensities, showing threshold voltage shift values reduced by more than ∼70% under stress conditions.

  15. Method for formation of thin film transistors on plastic substrates

    DOEpatents

    Carey, Paul G.; Smith, Patrick M.; Sigmon, Thomas W.; Aceves, Randy C.

    1998-10-06

    A process for formation of thin film transistors (TFTs) on plastic substrates replaces standard thin film transistor fabrication techniques, and uses sufficiently lower processing temperatures so that inexpensive plastic substrates may be used in place of standard glass, quartz, and silicon wafer-based substrates. The process relies on techniques for depositing semiconductors, dielectrics, and metals at low temperatures; crystallizing and doping semiconductor layers in the TFT with a pulsed energy source; and creating top-gate self-aligned as well as back-gate TFT structures. The process enables the fabrication of amorphous and polycrystalline channel silicon TFTs at temperatures sufficiently low to prevent damage to plastic substrates. The process has use in large area low cost electronics, such as flat panel displays and portable electronics.

  16. Method for formation of thin film transistors on plastic substrates

    DOEpatents

    Carey, P.G.; Smith, P.M.; Sigmon, T.W.; Aceves, R.C.

    1998-10-06

    A process for formation of thin film transistors (TFTs) on plastic substrates replaces standard thin film transistor fabrication techniques, and uses sufficiently lower processing temperatures so that inexpensive plastic substrates may be used in place of standard glass, quartz, and silicon wafer-based substrates. The process relies on techniques for depositing semiconductors, dielectrics, and metals at low temperatures; crystallizing and doping semiconductor layers in the TFT with a pulsed energy source; and creating top-gate self-aligned as well as back-gate TFT structures. The process enables the fabrication of amorphous and polycrystalline channel silicon TFTs at temperatures sufficiently low to prevent damage to plastic substrates. The process has use in large area low cost electronics, such as flat panel displays and portable electronics. 5 figs.

  17. Sensors employing Functionalized Conducting Polymer Thin Film Transistors

    NASA Astrophysics Data System (ADS)

    Tanese, M. C.; Torsi, L.; Cioffi, N.; Sabbatini, L.; Zambonin, P. G.

    2003-12-01

    Functionalized conducting polymers are employed as active layers in sensors with a thin film transistor (TFT) device structure. Such devices can work as multi-parameter sensors with responses that are fast, repeatable and reversible at room temperature. In this work, a strategy is proposed to enhance the chemical selectivity of organic TFT sensors, by selecting active layers that are made of conducting polymers bearing chemically different substituents. A modulation of the devices sensitivity towards analytes such as alcohols and ketones is demonstrated.

  18. High-pressure Gas Activation for Amorphous Indium-Gallium-Zinc-Oxide Thin-Film Transistors at 100 °C.

    PubMed

    Kim, Won-Gi; Tak, Young Jun; Du Ahn, Byung; Jung, Tae Soo; Chung, Kwun-Bum; Kim, Hyun Jae

    2016-01-01

    We investigated the use of high-pressure gases as an activation energy source for amorphous indium-gallium-zinc-oxide (a-IGZO) thin film transistors (TFTs). High-pressure annealing (HPA) in nitrogen (N2) and oxygen (O2) gases was applied to activate a-IGZO TFTs at 100 °C at pressures in the range from 0.5 to 4 MPa. Activation of the a-IGZO TFTs during HPA is attributed to the effect of the high-pressure environment, so that the activation energy is supplied from the kinetic energy of the gas molecules. We reduced the activation temperature from 300 °C to 100 °C via the use of HPA. The electrical characteristics of a-IGZO TFTs annealed in O2 at 2 MPa were superior to those annealed in N2 at 4 MPa, despite the lower pressure. For O2 HPA under 2 MPa at 100 °C, the field effect mobility and the threshold voltage shift under positive bias stress were improved by 9.00 to 10.58 cm(2)/V.s and 3.89 to 2.64 V, respectively. This is attributed to not only the effects of the pressurizing effect but also the metal-oxide construction effect which assists to facilitate the formation of channel layer and reduces oxygen vacancies, served as electron trap sites. PMID:26972476

  19. High-pressure Gas Activation for Amorphous Indium-Gallium-Zinc-Oxide Thin-Film Transistors at 100 °C

    PubMed Central

    Kim, Won-Gi; Tak, Young Jun; Du Ahn, Byung; Jung, Tae Soo; Chung, Kwun-Bum; Kim, Hyun Jae

    2016-01-01

    We investigated the use of high-pressure gases as an activation energy source for amorphous indium-gallium-zinc-oxide (a-IGZO) thin film transistors (TFTs). High-pressure annealing (HPA) in nitrogen (N2) and oxygen (O2) gases was applied to activate a-IGZO TFTs at 100 °C at pressures in the range from 0.5 to 4 MPa. Activation of the a-IGZO TFTs during HPA is attributed to the effect of the high-pressure environment, so that the activation energy is supplied from the kinetic energy of the gas molecules. We reduced the activation temperature from 300 °C to 100 °C via the use of HPA. The electrical characteristics of a-IGZO TFTs annealed in O2 at 2 MPa were superior to those annealed in N2 at 4 MPa, despite the lower pressure. For O2 HPA under 2 MPa at 100 °C, the field effect mobility and the threshold voltage shift under positive bias stress were improved by 9.00 to 10.58 cm2/V.s and 3.89 to 2.64 V, respectively. This is attributed to not only the effects of the pressurizing effect but also the metal-oxide construction effect which assists to facilitate the formation of channel layer and reduces oxygen vacancies, served as electron trap sites. PMID:26972476

  20. Microstructural evolution of tungsten oxide thin films

    NASA Astrophysics Data System (ADS)

    Hembram, K. P. S. S.; Thomas, Rajesh; Rao, G. Mohan

    2009-10-01

    Tungsten oxide thin films are of great interest due to their promising applications in various optoelectronic thin film devices. We have investigated the microstructural evolution of tungsten oxide thin films grown by DC magnetron sputtering on silicon substrate. The structural characterization and surface morphology were carried out using X-ray diffraction and Scanning Electron Microscopy (SEM). The as deposited films were amorphous, where as, the films annealed above 400 °C were crystalline. In order to explain the microstructural changes due to annealing, we have proposed a "instability wheel" model for the evolution of the microstructure. This model explains the transformation of mater into various geometries within them selves, followed by external perturbation.

  1. Chemically Functionalized, Well-Dispersed Carbon Nanotubes in Lithium-Doped Zinc Oxide for Low-Cost, High-Performance Thin-Film Transistors.

    PubMed

    Son, Gi-Cheol; Chee, Sang-Soo; Jun, Ji-Hyun; Son, Myungwoo; Lee, Sun Sook; Choi, Youngmin; Jeong, Sunho; Ham, Moon-Ho

    2016-04-13

    Surface-functionalized carbon nanotubes (CNTs) are introduced into lithium-doped ZnO thin-film transistors (TFTs) as an alternative to the conventional incorporation of an expensive element, indium. The crucial role of surface functionalization of CNTs is clarified with the demonstration of indium-free ZnO-based TFTs with a field-effect mobility of 28.6 cm(2) V(-1) s(-1) and an on/off current ratio of 9 × 10(6) for low-cost, high-performance electronics. PMID:26856958

  2. Nonvolatile memory thin-film transistors using biodegradable chicken albumen gate insulator and oxide semiconductor channel on eco-friendly paper substrate.

    PubMed

    Kim, So-Jung; Jeon, Da-Bin; Park, Jung-Ho; Ryu, Min-Ki; Yang, Jong-Heon; Hwang, Chi-Sun; Kim, Gi-Heon; Yoon, Sung-Min

    2015-03-01

    Nonvolatile memory thin-film transistors (TFTs) fabricated on paper substrates were proposed as one of the eco-friendly electronic devices. The gate stack was composed of chicken albumen gate insulator and In-Ga-Zn-O semiconducting channel layers. All the fabrication processes were performed below 120 °C. To improve the process compatibility of the synthethic paper substrate, an Al2O3 thin film was introduced as adhesion and barrier layers by atomic layer deposition. The dielectric properties of biomaterial albumen gate insulator were also enhanced by the preparation of Al2O3 capping layer. The nonvolatile bistabilities were realized by the switching phenomena of residual polarization within the albumen thin film. The fabricated device exhibited a counterclockwise hysteresis with a memory window of 11.8 V, high on/off ratio of approximately 1.1 × 10(6), and high saturation mobility (μsat) of 11.5 cm(2)/(V s). Furthermore, these device characteristics were not markedly degraded even after the delamination and under the bending situration. When the curvature radius was set as 5.3 cm, the ION/IOFF ratio and μsat were obtained to be 5.9 × 10(6) and 7.9 cm(2)/(V s), respectively. PMID:25679117

  3. Effect of top gate bias on photocurrent and negative bias illumination stress instability in dual gate amorphous indium-gallium-zinc oxide thin-film transistor

    SciTech Connect

    Lee, Eunji; Chowdhury, Md Delwar Hossain; Park, Min Sang; Jang, Jin

    2015-12-07

    We have studied the effect of top gate bias (V{sub TG}) on the generation of photocurrent and the decay of photocurrent for back channel etched inverted staggered dual gate structure amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film-transistors. Upon 5 min of exposure of 365 nm wavelength and 0.7 mW/cm{sup 2} intensity light with negative bottom gate bias, the maximum photocurrent increases from 3.29 to 322 pA with increasing the V{sub TG} from −15 to +15 V. By changing V{sub TG} from negative to positive, the Fermi level (E{sub F}) shifts toward conduction band edge (E{sub C}), which substantially controls the conversion of neutral vacancy to charged one (V{sub O} → V{sub O}{sup +}/V{sub O}{sup 2+} + e{sup −}/2e{sup −}), peroxide (O{sub 2}{sup 2−}) formation or conversion of ionized interstitial (O{sub i}{sup 2−}) to neutral interstitial (O{sub i}), thus electron concentration at conduction band. With increasing the exposure time, more carriers are generated, and thus, maximum photocurrent increases until being saturated. After negative bias illumination stress, the transfer curve shows −2.7 V shift at V{sub TG} = −15 V, which gradually decreases to −0.42 V shift at V{sub TG} = +15 V. It clearly reveals that the position of electron quasi-Fermi level controls the formation of donor defects (V{sub O}{sup +}/V{sub O}{sup 2+}/O{sub 2}{sup 2−}/O{sub i}) and/or hole trapping in the a-IGZO /interfaces.

  4. Influence of source and drain contacts on the properties of indium-gallium-zinc-oxide thin-film transistors based on amorphous carbon nanofilm as barrier layer.

    PubMed

    Luo, Dongxiang; Xu, Hua; Zhao, Mingjie; Li, Min; Xu, Miao; Zou, Jianhua; Tao, Hong; Wang, Lei; Peng, Junbiao

    2015-02-18

    Amorphous indium-gallium-zinc-oxide thin film transistors (α-IGZO TFTs) with damage-free back channel wet-etch (BCE) process were achieved by introducing a carbon nanofilm as a barrier layer. We investigate the effects of different source-and-drain (S/D) materials on TFT performance. We find the TFT with Ti/C S/D electrodes exhibits a superior performance with higher output current, lower threshold voltage, and higher effective electron mobility compared to that of Mo/C S/D electrodes. Transmittance electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) are employed to analysis the interfacial interaction between S/D metal/C/α-IGZO layers. The results indicate that the better performance of TFTs with Ti/C electrodes should be attributed to the formations of Ti-C and Ti-O at the Ti/C-contact regions, which lead to a lower contact resistance, whereas Mo film is relatively stable and does not react easily with C nanofilm, resulting in a nonohmic contact behavior between Mo/C and α-IGZO layer. However, both kinds of α-IGZO TFTs show good stability under thermal bias stress, indicating that the inserted C nanofilms could avoid the impact on the α-IGZO channel regions during S/D electrodes formation. Finally, we successfully fabricated a high-definition active-matrix organic lighting emitting diode prototype driven by α-IGZO TFTs with Ti/C electrodes in a pilot line. PMID:25619280

  5. Effects of thickness and geometric variations in the oxide gate stack on the nonvolatile memory behaviors of charge-trap memory thin-film transistors

    NASA Astrophysics Data System (ADS)

    Bak, Jun Yong; Kim, So-Jung; Byun, Chun-Won; Pi, Jae-Eun; Ryu, Min-Ki; Hwang, Chi Sun; Yoon, Sung-Min

    2015-09-01

    Device designs of charge-trap oxide memory thin-film transistors (CTM-TFTs) were investigated to enhance their nonvolatile memory performances. The first strategy was to optimize the film thicknesses of the tunneling and charge-trap (CT) layers in order to meet requirements of both higher operation speed and longer retention time. While the program speed and memory window were improved for the device with a thinner tunneling layer, a long retention time was obtained only for the device with a tunneling layer thicker than 5 nm. The carrier concentration and charge-trap densities were optimized in the 30-nm-thick CT layer. It was observed that 10-nm-thick tunneling, 30-nm-thick CT, and 50-nm-thick blocking layers were the best configuration for our proposed CTM-TFTs, where a memory on/off margin higher than 107 was obtained, and a memory margin of 6.6 × 103 was retained even after the lapse of 105 s. The second strategy was to examine the effects of the geometrical relations between the CT and active layers for the applications of memory elements embedded in circuitries. The CTM-TFTs fabricated without an overlap between the CT layer and the drain electrode showed an enhanced program speed by the reduced parasitic capacitance. The drain-bias disturbance for the memory off-state was effectively suppressed even when a higher read-out drain voltage was applied. Appropriate device design parameters, such as the film thicknesses of each component layer and the geometrical relations between them, can improve the memory performances and expand the application fields of the proposed CTM-TFTs.

  6. Effects of Ga:N addition on the electrical performance of zinc tin oxide thin film transistor by solution-processing.

    PubMed

    Ahn, Byung Du; Jeon, Hye Ji; Park, Jin-Seong

    2014-06-25

    This paper addressed the effect of gallium nitrate hydrate addition on thin film transistor (TFT) performance and positive bias stability of amorphous zinc tin oxide (ZTO) TFTs by solution processing, Further, the mechanisms responsible for chemical properties and electronic band structure are explored. A broad exothermic peak accompanied by weight loss appeared in the range from about 350 to 570 °C for the ZTO solution; the thermal reaction of the Ga-ZTO:N solution was completed at 520 °C. This is because the gallium nitrate hydrate precursor promoted the decomposition and dehydroxylation reaction for Zn(CH3COO)2·2H2O and/or SnCl2·2H2O precursors. The concentrations of carbon and chloride in gallium nitrate hydrate added ZTO films annealed at 400 °C have a lower value (C 0.65, Cl 0.65 at. %) compared with those of ZTO films (C 3.15, Cl 0.82 at. %). Absorption bands at 416, 1550, and 1350 cm(-1) for GaZTO:N films indicated the presence of ZnGa2O4, N-H, and N═O groups by Fourier transform infrared spectroscopy measurement, respectively. As a result, an inverted staggered Ga-ZTO:N TFT exhibited a mobility of 4.84 cm(2) V(-1) s(-1) in the saturation region, a subthreshold swing of 0.35 V/decade, and a threshold gate voltage (Vth) of 0.04 V. In addition, the instability of Vth values of the ZTO TFTs under positive bias stress conditions was suppressed by adding Ga and N from 13.6 to 3.17 V, which caused a reduction in the oxygen-related defects located near the conduction band. PMID:24892383

  7. Thin-Film Solid Oxide Fuel Cells

    NASA Technical Reports Server (NTRS)

    Chen, Xin; Wu, Nai-Juan; Ignatiev, Alex

    2009-01-01

    The development of thin-film solid oxide fuel cells (TFSOFCs) and a method of fabricating them have progressed to the prototype stage. This can result in the reduction of mass, volume, and the cost of materials for a given power level.

  8. Thin-film transistors based on organic conjugated semiconductors

    NASA Astrophysics Data System (ADS)

    Garnier, Francis

    1998-02-01

    The use of organic semiconductors as active layers in thin-film transistors has raised in the recent years a large interest, both for the fundamental understanding of the charge transport processes in organic materials, and also for the potential applications of these devices in the new field of flexible electronics. Short conjugated oligomers have been shown to possess much higher field-effect mobilities than their parent conjugated polymers. The origin of such increase in the efficiency of charge transport is mainly attributed to the close-packing and long-range structural organization displayed in thin films of conjugated oligomers. The various routes for controlling this organization are described, which allow to realize liquid crystal-like two-dimensional structures for these semiconductors, whose carrier mobility has now become equivalent to that of amorphous silicon. It is also shown that the effect of conjugation length on carrier mobility is not as critical as previously thought, but the associated increase of the band gap energy effects the efficiency of charge injection at the metal/semiconductor interface. This problem can be answered by realizing a local doping of the semiconductor, which allows the injection of charge to operate through an efficient tunneling mechanism. Organic-based thin-film transistors have now become viable devices.

  9. Molecular orientation dependence of hole-injection barrier in pentacene thin film on the Au surface in organic thin film transistor

    NASA Astrophysics Data System (ADS)

    Ihm, Kyuwook; Kim, Bongsoo; Kang, Tai-Hee; Kim, Ki-Jeong; Joo, Min Ho; Kim, Tae Hyeong; Yoon, Sang Soo; Chung, Sukmin

    2006-07-01

    We have investigated the effects of a buffer layer insertion on the performance of the pentacene based thin film transistor with a bottom contact structure. When the pentacene molecules have a standing up coordination on the Au surface that is modified by the benzenethiol or methanethiol, the transition region in the pentacene thin film is removed along the boundary between the Au and silicon oxide region, and the hole-injection barrier decreases by 0.4eV. Pentacene on various surfaces showed that the highly occupied molecular level is 0.2-0.4eV lower in the standing up coordination than in the lying down coordination.

  10. Organic thin-film transistors for chemical and biological sensing.

    PubMed

    Lin, Peng; Yan, Feng

    2012-01-01

    Organic thin-film transistors (OTFTs) show promising applications in various chemical and biological sensors. The advantages of OTFT-based sensors include high sensitivity, low cost, easy fabrication, flexibility and biocompatibility. In this paper, we review the chemical sensors and biosensors based on two types of OTFTs, including organic field-effect transistors (OFETs) and organic electrochemical transistors (OECTs), mainly focusing on the papers published in the past 10 years. Various types of OTFT-based sensors, including pH, ion, glucose, DNA, enzyme, antibody-antigen, cell-based sensors, dopamine sensor, etc., are classified and described in the paper in sequence. The sensing mechanisms and the detection limits of the devices are described in details. It is expected that OTFTs may have more important applications in chemical and biological sensing with the development of organic electronics. PMID:22102447

  11. Effect of direct current sputtering power on the behavior of amorphous indium-gallium-zinc-oxide thin-film transistors under negative bias illumination stress: A combination of experimental analyses and device simulation

    SciTech Connect

    Jang, Jun Tae; Kim, Dong Myong; Choi, Sung-Jin; Kim, Dae Hwan E-mail: drlife@kookmin.ac.kr; Park, Jozeph; Ahn, Byung Du; Kim, Hyun-Suk E-mail: drlife@kookmin.ac.kr

    2015-03-23

    The effect of direct current sputtering power of indium-gallium-zinc-oxide (IGZO) on the performance and stability of the corresponding thin-film transistor devices was studied. The field effect mobility increases as the IGZO sputter power increases, at the expense of device reliability under negative bias illumination stress (NBIS). Device simulation based on the extracted sub-gap density of states indicates that the field effect mobility is improved as a result of the number of acceptor-like states decreasing. The degradation by NBIS is suggested to be induced by the formation of peroxides in IGZO rather than charge trapping.

  12. Improvement in the electrical performance and bias-stress stability of dual-active-layered silicon zinc oxide/zinc oxide thin-film transistor

    NASA Astrophysics Data System (ADS)

    Liu, Yu-Rong; Zhao, Gao-Wei; Lai, Pai-To; Yao, Ruo-He

    2016-08-01

    Si-doped zinc oxide (SZO) thin films are deposited by using a co-sputtering method, and used as the channel active layers of ZnO-based TFTs with single and dual active layer structures. The effects of silicon content on the optical transmittance of the SZO thin film and electrical properties of the SZO TFT are investigated. Moreover, the electrical performances and bias-stress stabilities of the single- and dual-active-layer TFTs are investigated and compared to reveal the effects of the Si doping and dual-active-layer structure. The average transmittances of all the SZO films are about 90% in the visible light region of 400 nm–800 nm, and the optical band gap of the SZO film gradually increases with increasing Si content. The Si-doping can effectively suppress the grain growth of ZnO, revealed by atomic force microscope analysis. Compared with that of the undoped ZnO TFT, the off-state current of the SZO TFT is reduced by more than two orders of magnitude and it is 1.5 × 10‑12 A, and thus the on/off current ratio is increased by more than two orders of magnitude. In summary, the SZO/ZnO TFT with dual-active-layer structure exhibits a high on/off current ratio of 4.0 × 106 and superior stability under gate-bias and drain-bias stress. Projected supported by the National Natural Science Foundation of China (Grant Nos. 61076113 and 61274085), the Natural Science Foundation of Guangdong Province (Grant No. 2016A030313474), and the University Development Fund (Nanotechnology Research Institute, Grant No. 00600009) of the University of Hong Kong, China.

  13. Thin film transistors and solar cells. (Latest citations from the US Patent bibliographic file with exemplary claims). Published Search

    SciTech Connect

    1995-01-01

    The bibliography contains citations of selected patents concerning the fabrication and application methods of thin film transistors and thin film solar cells. Methods of manufacturing thin film transistors for use in electronic display devices are presented. Techniques for continuously producing durable and reliable thin film solar cells are discussed. (Contains 250 citations and includes a subject term index and title list.)

  14. Technical Obstacles to Thin Film Transistor Circuits on Plastic

    NASA Astrophysics Data System (ADS)

    Miyasaka, Mitsutoshi; Hara, Hiroyuki; Karaki, Nobuo; Inoue, Satoshi; Kawai, Hideyuki; Nebashi, Satoshi

    2008-06-01

    Two main technical obstacles must be overcome to build a fruitful business in the nascent flexible microelectronics industry: the self-heating effect of thin film transistors (TFTs), and the thermal and mechanical durability of flexible devices. The self-heating effect is controlled through TFT shape, TFT electrical performance, dimensional reductions, and energy-efficient circuits. Plastic engineering is one of the keys to solving thermal and mechanical durability problems faced by flexible microelectronics devices. Once these obstacles are cleared, TFT circuits on plastic will spawn a new industry and markets for plastic large-scale integrations.

  15. Liquid crystals for organic thin-film transistors

    NASA Astrophysics Data System (ADS)

    Iino, Hiroaki; Usui, Takayuki; Hanna, Jun-Ichi

    2015-04-01

    Crystalline thin films of organic semiconductors are a good candidate for field effect transistor (FET) materials in printed electronics. However, there are currently two main problems, which are associated with inhomogeneity and poor thermal durability of these films. Here we report that liquid crystalline materials exhibiting a highly ordered liquid crystal phase of smectic E (SmE) can solve both these problems. We design a SmE liquid crystalline material, 2-decyl-7-phenyl-[1]benzothieno[3,2-b][1]benzothiophene (Ph-BTBT-10), for FETs and synthesize it. This material provides uniform and molecularly flat polycrystalline thin films reproducibly when SmE precursor thin films are crystallized, and also exhibits high durability of films up to 200 °C. In addition, the mobility of FETs is dramatically enhanced by about one order of magnitude (over 10 cm2 V-1 s-1) after thermal annealing at 120 °C in bottom-gate-bottom-contact FETs. We anticipate the use of SmE liquid crystals in solution-processed FETs may help overcome upcoming difficulties with novel technologies for printed electronics.

  16. Solution-processed hybrid organic-inorganic complementary thin-film transistor inverter

    NASA Astrophysics Data System (ADS)

    Cheong, Heajeong; Kuribara, Kazunori; Ogura, Shintaro; Fukuda, Nobuko; Yoshida, Manabu; Ushijima, Hirobumi; Uemura, Sei

    2016-04-01

    We investigated hybrid organic-inorganic complementary inverters with a solution-processed indium-gallium-zinc-oxide (IGZO) n-channel thin-film transistor (TFT) and p-channel TFTs using the high-uniformity polymer poly[2,5-bis(alkyl)pyrrolo[3,4-c]pyrrolo-1,4(2H,5H)-dione-alt-5,5-di(thiophene-2-yl)-2,2-(E)-2-(2-(thiophen-2-yl)vinyl)thiophene] (PDVT-10). The IGZO TFT was fabricated at 150 °C for 1 min. It showed a high field-effect mobility of 0.9 cm2·V-1·s-1 and a high on/off current ratio of 107. A hybrid complementary inverter was fabricated by combining IGZO with a PDVT-10 thin-film transistor and its operation was confirmed.

  17. Ferroelectric/Dielectric Double Gate Insulator Spin-Coated Using Barium Titanate Nanocrystals for an Indium Oxide Nanocrystal-Based Thin-Film Transistor.

    PubMed

    Pham, Hien Thu; Yang, Jin Ho; Lee, Don-Sung; Lee, Byoung Hun; Jeong, Hyun-Dam

    2016-03-23

    Barium titanate nanocrystals (BT NCs) were prepared under solvothermal conditions at 200 °C for 24 h. The shape of the BT NCs was tuned from nanodot to nanocube upon changing the polarity of the alcohol solvent, varying the nanosize in the range of 14-22 nm. Oleic acid-passivated NCs showed good solubility in a nonpolar solvent. The effect of size and shape of the BT NCs on the ferroelectric properties was also studied. The maximum polarization value of 7.2 μC/cm(2) was obtained for the BT-5 NC thin film. Dielectric measurements of the films showed comparable dielectric constant values of BT NCs over 1-100 kHz without significant loss. Furthermore, the bottom gate In2O3 NC thin film transistors exhibited outstanding device performance with a field-effect mobility of 11.1 cm(2) V(-1) s(-1) at a low applied gate voltage with BT-5 NC/SiO2 as the gate dielectric. The low-density trapped state was observed at the interface between the In2O3 NC semiconductor and the BT-5 NCs/SiO2 dielectric film. Furthermore, compensation of the applied gate field by an electric dipole-induced dipole field within the BT-5 NC film was also observed. PMID:26927618

  18. Characterization of novel BaZnSnO thin films by solution process and applications in thin film transistors

    SciTech Connect

    Li, Jun; Huang, Chuan-Xin; Zhang, Jian-Hua; Zhu, Wen-Qing; Jiang, Xue-Yin; Zhang, Zhi-Lin

    2015-08-15

    Graphical abstract: This work reports the Ba content on thin film transistor based on a novel BaZnSnO semiconductor using solution process. - Highlights: • No reports about BaZnSnO thin film using solution process. • BaZnSnO thin film transistor (TFT) was firstly fabricated. • BaZnSnO-TFT shows a acceptable performace. • Influence of Ba content on BaZnSnO-TFT. - Abstract: A novel BaZnSnO semiconductor is fabricated using solution process and the influence of Ba addition on the structure, the chemical state of oxygen and electrical performance of BaZnSnO thin films are investigated. A high performance BaZnSnO-based thin film transistor with 15 mol% Ba is obtained, showing a saturation mobility of 1.94 cm{sup 2}/V s, a threshold voltage of 3.6 V, an on/off current ratio of 6.2 × 10{sup 6}, a subthreshold swing of 0.94 V/decade, and a good bias stability. Transistors with solution processed BaZnSnO films are promising candidates for the development of future large-area, low-cost and high-performance electronic devices.

  19. Physically-based simulation of zinc oxide thin-film transistors: Contact resistance contribution on density of states

    NASA Astrophysics Data System (ADS)

    Dominguez, Miguel A.; Alcantara, Salvador; Soto, Susana

    2016-06-01

    In this work, using a physically-based simulator, the density of states DOS is modeled to reproduce the experimental electrical characteristics of ZnO TFTs fabricated by Ultrasonic Spray Pyrolysis at 200 °C. The contact resistance was experimentally extracted from the ZnO TFTs and included into the simulation, in order to separate the metal-semiconductor interface contribution from the DOS. A comparison between the modeled DOS considering the contact resistance and disregarding it is also presented. It is proposed to consider the acceptor-like states and the tail-donor states, where the deep-acceptor states have approximately an exponential form and the distribution of tail-acceptor states are sharper than the distribution of tail-donor states. The simulated electrical characteristics reproduce very well the experimental data at different channel lengths. The use of physically-based simulation can be useful to model the DOS of Oxide semiconductor films in TFTs by reproducing the experimental data.

  20. A thermalization energy analysis of the threshold voltage shift in amorphous indium gallium zinc oxide thin film transistors under simultaneous negative gate bias and illumination

    SciTech Connect

    Flewitt, A. J.; Powell, M. J.

    2014-04-07

    It has been previously observed that thin film transistors (TFTs) utilizing an amorphous indium gallium zinc oxide (a-IGZO) semiconducting channel suffer from a threshold voltage shift when subjected to a negative gate bias and light illumination simultaneously. In this work, a thermalization energy analysis has been applied to previously published data on negative bias under illumination stress (NBIS) in a-IGZO TFTs. A barrier to defect conversion of 0.65–0.75 eV is extracted, which is consistent with reported energies of oxygen vacancy migration. The attempt-to-escape frequency is extracted to be 10{sup 6}−10{sup 7} s{sup −1}, which suggests a weak localization of carriers in band tail states over a 20–40 nm distance. Models for the NBIS mechanism based on charge trapping are reviewed and a defect pool model is proposed in which two distinct distributions of defect states exist in the a-IGZO band gap: these are associated with states that are formed as neutrally charged and 2+ charged oxygen vacancies at the time of film formation. In this model, threshold voltage shift is not due to a defect creation process, but to a change in the energy distribution of states in the band gap upon defect migration as this allows a state formed as a neutrally charged vacancy to be converted into one formed as a 2+ charged vacancy and vice versa. Carrier localization close to the defect migration site is necessary for the conversion process to take place, and such defect migration sites are associated with conduction and valence band tail states. Under negative gate bias stressing, the conduction band tail is depleted of carriers, but the bias is insufficient to accumulate holes in the valence band tail states, and so no threshold voltage shift results. It is only under illumination that the quasi Fermi level for holes is sufficiently lowered to allow occupation of valence band tail states. The resulting charge localization then allows a negative threshold voltage

  1. Oxidation effects of poly(3,4-ethylenedioxythiophene)/poly(styrene sulfonate) electrodes on high-performance organic thin-film transistors

    NASA Astrophysics Data System (ADS)

    Jang, Yunseok; Jo, Jeongdai; Choi, Young-Man; Woo, Kyoohee; Kwon, Sin; Kim, Kwang-Young

    2015-06-01

    We adjusted the conductivity of a poly(3,4-ethylenedioxythiophene)/poly(styrene sulfonate) (PEDOT/PSS) electrode and an injection barrier between the PEDOT/PSS source/drain (S/D) electrode and a pentacene semiconductor by adding HAuCl4 to a PEDOT/PSS solution. Gold in the PEDOT/PSS S/D electrode was synthesized by a redox reaction between PEDOT/PSS and Au ions. This reaction enhances the conductivity of the PEDOT/PSS S/D electrodes and reduces the injection barrier between the PEDOT/PSS S/D electrodes and the pentacene semiconductor, and causes the field-effect mobility to increase by about 230%. As such, it is considered a very useful method of making high-performance organic thin-film transistors (OTFTs).

  2. Electrical stability enhancement of GeInGaO thin-film transistors by solution-processed Li-doped yttrium oxide passivation

    NASA Astrophysics Data System (ADS)

    Choi, U. H.; Yoon, S.; Yoon, D. H.; Tak, Y. J.; Kim, Y.-G.; Ahn, B. D.; Park, J.; Kim, H. J.

    2016-07-01

    In this study, we investigated a method of enhancing the electrical stability of GeInGaO thin-film transistors (TFTs) using a Li-doped Y2O3 (YO) passivation layer (PVL). Li reduced metal hydroxide groups in the PVL, and diffused into the channel layer and reduced the oxygen vacancy at the top surface of the channel layer, which is the origin of the defect state and electrical instability. In addition, the negative-bias temperature stress (NBTS) for 3600 s improved for Li-doped YO (LYO) PVL. The threshold voltage shift decreased from  ‑10.3 V for the YO PVL to  ‑4.8 V for the LYO PVL, a 54% improvement.

  3. Detection of saliva-range glucose concentrations using organic thin-film transistors

    NASA Astrophysics Data System (ADS)

    Elkington, D.; Belcher, W. J.; Dastoor, P. C.; Zhou, X. J.

    2014-07-01

    We describe the development of a glucose sensor through direct incorporation of an enzyme (glucose oxidase) into the gate of an organic thin film transistor (OTFT). We show that glucose diffusion is the key determinant of the device response time and present a mechanism of glucose sensing in these devices that involves protonic doping of the transistor channel via enzymatic oxidation of glucose. The integrated OTFT sensor is sensitive across 4 decades of glucose concentration; a range that encompasses both the blood and salivary glucose concentration levels. As such, this work acts as a proof-of-concept for low-cost printed biosensors for salivary glucose.

  4. Detection of saliva-range glucose concentrations using organic thin-film transistors

    SciTech Connect

    Elkington, D.; Belcher, W. J.; Dastoor, P. C.; Zhou, X. J.

    2014-07-28

    We describe the development of a glucose sensor through direct incorporation of an enzyme (glucose oxidase) into the gate of an organic thin film transistor (OTFT). We show that glucose diffusion is the key determinant of the device response time and present a mechanism of glucose sensing in these devices that involves protonic doping of the transistor channel via enzymatic oxidation of glucose. The integrated OTFT sensor is sensitive across 4 decades of glucose concentration; a range that encompasses both the blood and salivary glucose concentration levels. As such, this work acts as a proof-of-concept for low-cost printed biosensors for salivary glucose.

  5. Thin film transistors using PECVD-grown carbon nanotubes.

    PubMed

    Ono, Yuki; Kishimoto, Shigeru; Ohno, Yutaka; Mizutani, Takashi

    2010-05-21

    Thin film transistors with a carbon nanotube (CNT) network as a channel have been fabricated using grid-inserted plasma-enhanced chemical vapor deposition (PECVD) which has the advantage of preferential growth of the CNTs with semiconducting behavior in the I-V characteristics of CNT field effect transistors (CNT-FETs). Taking advantage of the preferential growth and suppression of bundle formation, a large ON current of 170 microA mm(-1), which is among the largest in these kinds of devices with a large ON/OFF current ratio of about 10(5), has been realized in the relatively short channel length of 10 microm. The field effect mobility of the device was 5.8 cm(2) V(-1) s(-1). PMID:20418603

  6. Thin film transistors using PECVD-grown carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Ono, Yuki; Kishimoto, Shigeru; Ohno, Yutaka; Mizutani, Takashi

    2010-05-01

    Thin film transistors with a carbon nanotube (CNT) network as a channel have been fabricated using grid-inserted plasma-enhanced chemical vapor deposition (PECVD) which has the advantage of preferential growth of the CNTs with semiconducting behavior in the I-V characteristics of CNT field effect transistors (CNT-FETs). Taking advantage of the preferential growth and suppression of bundle formation, a large ON current of 170 µA mm - 1, which is among the largest in these kinds of devices with a large ON/OFF current ratio of about 105, has been realized in the relatively short channel length of 10 µm. The field effect mobility of the device was 5.8 cm2 V - 1 s - 1.

  7. Effect of Annealing Temperature on the Performance of SnO2 Thin Film Transistors Prepared by Spray Pyrolysis.

    PubMed

    Zhang, XinAn; Zhai, JunXia; Yu, XianKun; Zhu, RuiJuan; Zhang, WeiFeng

    2015-08-01

    We fabricated SnO2 thin film transistors on thermally oxidized p-type silicon substrates by low-cost spray pyrolysis. The effect of annealing temperatures on electrical characteristics of SnO2 thin film transistors were investigated. Thermal annealing at higher temperatures induced a negative shift of the threshold voltage (VT) and an increase in the saturation mobility. It was found that the device annealed at 450 °C exhibited a good electrical performance with the field-effect mobility of 0.19 cm2/Vs, the threshold voltage of 2.5 V, and the on/off current ratio of 10(3). PMID:26369222

  8. Room-temperature fabrication of light-emitting thin films based on amorphous oxide semiconductor

    NASA Astrophysics Data System (ADS)

    Kim, Junghwan; Miyokawa, Norihiko; Ide, Keisuke; Toda, Yoshitake; Hiramatsu, Hidenori; Hosono, Hideo; Kamiya, Toshio

    2016-01-01

    We propose a light-emitting thin film using an amorphous oxide semiconductor (AOS) because AOS has low defect density even fabricated at room temperature. Eu-doped amorphous In-Ga-Zn-O thin films fabricated at room temperature emitted intense red emission at 614 nm. It is achieved by precise control of oxygen pressure so as to suppress oxygen-deficiency/excess-related defects and free carriers. An electronic structure model is proposed, suggesting that non-radiative process is enhanced mainly by defects near the excited states. AOS would be a promising host for a thin film phosphor applicable to flexible displays as well as to light-emitting transistors.

  9. Graphene as tunable contact for high performance thin film transistor

    NASA Astrophysics Data System (ADS)

    Liu, Yuan

    performance and mechanical robustness. By using the graphene as a work-function tunable contact for amorphous indium gallium zinc oxide (IGZO) thin film, the vertical current flow across the graphene-IGZO junction can be effectively modulated by an external gate potential to enable VTFTs with a highest on-off ratio exceeding 105. The unique vertical transistor architecture can readily enable ultrashort channel devices with very high delivering current and exceptional mechanical flexibility. Furthermore, I will, demonstrate a new design strategy for vertical OTFT with ultra-short channel length without using conventional high-resolution lithography process. They can deliver a high current density over 1.8 A/ cm2 and thus enable a high cutoff frequency devices (~ 0.4 MHz) comparable with the ultra-short channel organic transistors. Importantly, with unique vertical architecture, the entire organic channel material is sandwiched between the source and drain electrodes and is thus naturally protected to ensure excellent air-stability. Finally I will present a new strategy by using graphene as the back electrodes to achieve Ohmic contact to MoS2. With a finite density of states, the Fermi level of graphene can be readily tuned by a gate potential to enable a nearly perfect band alignment with MoS2. For the first time, a transparent contact to MoS2 is demonstrated with zero contact barrier and linear output behaviour at cryogenic temperatures (down to 1.9 K) for both monolayer and multilayer MoS2. Benefiting from the barrier-free transparent contacts, we show that a metal-insulator-transition (MIT) can be observed in a two-terminal MoS2 device, a phenomenon that could be easily masked by Schottky barriers found in conventional metal-contacted MoS2 devices. With further passivation by boron nitride (BN) encapsulation, we demonstrate a record-high extrinsic (two-terminal) field effect mobility up to 1300 cm2/V s in MoS2 at low temperature. These findings can open up exciting new

  10. Graphene as tunable contact for high performance thin film transistor

    NASA Astrophysics Data System (ADS)

    Liu, Yuan

    performance and mechanical robustness. By using the graphene as a work-function tunable contact for amorphous indium gallium zinc oxide (IGZO) thin film, the vertical current flow across the graphene-IGZO junction can be effectively modulated by an external gate potential to enable VTFTs with a highest on-off ratio exceeding 105. The unique vertical transistor architecture can readily enable ultrashort channel devices with very high delivering current and exceptional mechanical flexibility. Furthermore, I will, demonstrate a new design strategy for vertical OTFT with ultra-short channel length without using conventional high-resolution lithography process. They can deliver a high current density over 1.8 A/ cm2 and thus enable a high cutoff frequency devices (~ 0.4 MHz) comparable with the ultra-short channel organic transistors. Importantly, with unique vertical architecture, the entire organic channel material is sandwiched between the source and drain electrodes and is thus naturally protected to ensure excellent air-stability. Finally I will present a new strategy by using graphene as the back electrodes to achieve Ohmic contact to MoS2. With a finite density of states, the Fermi level of graphene can be readily tuned by a gate potential to enable a nearly perfect band alignment with MoS2. For the first time, a transparent contact to MoS2 is demonstrated with zero contact barrier and linear output behaviour at cryogenic temperatures (down to 1.9 K) for both monolayer and multilayer MoS2. Benefiting from the barrier-free transparent contacts, we show that a metal-insulator-transition (MIT) can be observed in a two-terminal MoS2 device, a phenomenon that could be easily masked by Schottky barriers found in conventional metal-contacted MoS2 devices. With further passivation by boron nitride (BN) encapsulation, we demonstrate a record-high extrinsic (two-terminal) field effect mobility up to 1300 cm2/V s in MoS2 at low temperature. These findings can open up exciting new

  11. Direct growth of oxide nanowires on CuOx thin film.

    PubMed

    Kim, Hwansoo; Lee, Byung Kook; An, Ki-Seok; Ju, Sanghyun

    2012-02-01

    Oxide nanowires were directly grown on a CuO(x) thin film deposited by plasma-enhanced atomic layer deposition without additional metal catalysts. Oxide nanowires would exhibit metal-catalyst-free growth on the CuO(x) thin film with oxide materials diffused on the top. Through a focused ion beam and transmission electron microscopy, we could verify that SnO(2) and ZnO nanowires were grown as single-crystalline structures just above the CuO(x) thin film. Bottom-gate structural SnO(2) and ZnO nanowire transistors exhibited mobilities of 135.2 and 237.6 cm(2) V(-1) s(-1), respectively. We anticipate that a variety of large-area and high-density oxide nanowires can be grown at low cost by using the CuO(x) thin film. PMID:22214566

  12. Highly improved photo-induced bias stability of sandwiched triple layer structure in sol-gel processed fluorine-doped indium zinc oxide thin film transistor

    NASA Astrophysics Data System (ADS)

    Kim, Dongha; Park, Hyungjin; Bae, Byeong-Soo

    2016-03-01

    In order to improve the reliability of TFT, an Al2O3 insulating layer is inserted between active fluorine doped indium zinc oxide (IZO:F) thin films to form a sandwiched triple layer. All the thin films were fabricated via low-cost sol-gel process. Due to its large energy bandgap and high bonding energy with oxygen atoms, the Al2O3 layer acts as a photo-induced positive charge blocking layer that effectively blocks the migration of both holes and V o2+ toward the interface between the gate insulator and the semiconductor. The inserted Al2O3 triple layer exhibits a noticeably low turn on voltage shift of -0.7 V under NBIS as well as the good TFT performance with a mobility of 10.9 cm2/V ṡ s. We anticipate that this approach can be used to solve the stability issues such as NBIS, which is caused by inescapable oxygen vacancies.

  13. Conduction Threshold in Accumulation-Mode InGaZnO Thin Film Transistors

    PubMed Central

    Lee, Sungsik; Nathan, Arokia

    2016-01-01

    The onset of inversion in the metal-oxide-semiconductor field-effect transistor (MOSFET) takes place when the surface potential is approximately twice the bulk potential. In contrast, the conduction threshold in accumulation mode transistors, such as the oxide thin film transistor (TFT), has remained ambiguous in view of the complex density of states distribution in the mobility gap. This paper quantitatively describes the conduction threshold of accumulation-mode InGaZnO TFTs as the transition of the Fermi level from deep to tail states, which can be defined as the juxtaposition of linear and exponential dependencies of the accumulated carrier density on energy. Indeed, this permits direct extraction and visualization of the threshold voltage in terms of the second derivative of the drain current with respect to gate voltage. PMID:26932790

  14. Conduction Threshold in Accumulation-Mode InGaZnO Thin Film Transistors.

    PubMed

    Lee, Sungsik; Nathan, Arokia

    2016-01-01

    The onset of inversion in the metal-oxide-semiconductor field-effect transistor (MOSFET) takes place when the surface potential is approximately twice the bulk potential. In contrast, the conduction threshold in accumulation mode transistors, such as the oxide thin film transistor (TFT), has remained ambiguous in view of the complex density of states distribution in the mobility gap. This paper quantitatively describes the conduction threshold of accumulation-mode InGaZnO TFTs as the transition of the Fermi level from deep to tail states, which can be defined as the juxtaposition of linear and exponential dependencies of the accumulated carrier density on energy. Indeed, this permits direct extraction and visualization of the threshold voltage in terms of the second derivative of the drain current with respect to gate voltage. PMID:26932790

  15. Conduction Threshold in Accumulation-Mode InGaZnO Thin Film Transistors

    NASA Astrophysics Data System (ADS)

    Lee, Sungsik; Nathan, Arokia

    2016-03-01

    The onset of inversion in the metal-oxide-semiconductor field-effect transistor (MOSFET) takes place when the surface potential is approximately twice the bulk potential. In contrast, the conduction threshold in accumulation mode transistors, such as the oxide thin film transistor (TFT), has remained ambiguous in view of the complex density of states distribution in the mobility gap. This paper quantitatively describes the conduction threshold of accumulation-mode InGaZnO TFTs as the transition of the Fermi level from deep to tail states, which can be defined as the juxtaposition of linear and exponential dependencies of the accumulated carrier density on energy. Indeed, this permits direct extraction and visualization of the threshold voltage in terms of the second derivative of the drain current with respect to gate voltage.

  16. Large-scale complementary macroelectronics using hybrid integration of carbon nanotubes and IGZO thin-film transistors.

    PubMed

    Chen, Haitian; Cao, Yu; Zhang, Jialu; Zhou, Chongwu

    2014-01-01

    Carbon nanotubes and metal oxide semiconductors have emerged as important materials for p-type and n-type thin-film transistors, respectively; however, realizing sophisticated macroelectronics operating in complementary mode has been challenging due to the difficulty in making n-type carbon nanotube transistors and p-type metal oxide transistors. Here we report a hybrid integration of p-type carbon nanotube and n-type indium-gallium-zinc-oxide thin-film transistors to achieve large-scale (>1,000 transistors for 501-stage ring oscillators) complementary macroelectronic circuits on both rigid and flexible substrates. This approach of hybrid integration allows us to combine the strength of p-type carbon nanotube and n-type indium-gallium-zinc-oxide thin-film transistors, and offers high device yield and low device variation. Based on this approach, we report the successful demonstration of various logic gates (inverter, NAND and NOR gates), ring oscillators (from 51 stages to 501 stages) and dynamic logic circuits (dynamic inverter, NAND and NOR gates). PMID:24923382

  17. Low-temperature, solution-processed ZrO2:B thin film: a bifunctional inorganic/organic interfacial glue for flexible thin-film transistors.

    PubMed

    Park, Jee Ho; Oh, Jin Young; Han, Sun Woong; Lee, Tae Il; Baik, Hong Koo

    2015-03-01

    A solution-processed boron-doped peroxo-zirconium oxide (ZrO2:B) thin film has been found to have multifunctional characteristics, providing both hydrophobic surface modification and a chemical glue layer. Specifically, a ZrO2:B thin film deposited on a hydrophobic layer becomes superhydrophilic following ultraviolet-ozone (UVO) treatment, whereas the same treatment has no effect on the hydrophobicity of the hydrophobic layer alone. Investigation of the ZrO2:B/hydrophobic interface layer using angle-resolved X-ray photoelectron spectroscopy (AR XPS) confirmed it to be chemically bonded like glue. Using the multifunctional nature of the ZrO2:B thin film, flexible amorphous indium oxide (In2O3) thin-film transistors (TFTs) were subsequently fabricated on a polyimide substrate along with a ZrO2:B/poly-4-vinylphenol (PVP) dielectric. An aqueous In2O3 solution was successfully coated onto the ZrO2:B/PVP dielectric, and the surface and chemical properties of the PVP and ZrO2:B thin films were analyzed by contact angle measurement, atomic force microscopy (AFM), Fourier transform infrared (FT-IR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). The surface-engineered PVP dielectric was found to have a lower leakage current density (Jleak) of 4.38 × 10(-8) A/cm(2) at 1 MV/cm, with no breakdown behavior observed up to a bending radius of 5 mm. In contrast, the electrical characteristics of the flexible amorphous In2O3 TFT such as on/off current ratio (Ion/off) and electron mobility remained similar up to 10 mm of bending without degradation, with the device being nonactivated at a bending radius of 5 mm. These results suggest that ZrO2:B thin films could be used for low-temperature, solution-processed surface-modified flexible devices. PMID:25664940

  18. Chemical and biological sensing with organic thin-film transistors

    NASA Astrophysics Data System (ADS)

    Mabeck, Jeffrey Todd

    Organic thin-film transistors (OTFTs) offer a great deal of promise for applications in chemical and biological sensing where there is a demand for small, portable, and inexpensive sensors. OTFTs have many advantages over other types of sensors, including low-cost fabrication, straightforward miniaturization, simple instrumentation, and inherent signal amplification. This dissertation examines two distinct types of OTFTs: organic field-effect transistors (OFETs) based on pentacene, and organic electrochemical transistors (OECTs) based on poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS). The bulk of the previous work on sensing with OFETs has focused on gas sensing, and this dissertation contributes to this body of work by briefly treating the large, reversible response of pentacene OFETs to humidity. However, there are many applications where the analyte of interest must be detected in an aqueous environment rather than a gaseous environment, and very little work has been done in this area for OFETs. Therefore, the integration of pentacene OFETs with microfluidics is treated in detail. Using poly(dimethylsiloxane) (PDMS) microfluidic channels to confine aqueous solutions over the active region of pentacene transistors, it is demonstrated that the current-voltage characteristics remain stable under aqueous flow with a decrease in mobility of ˜30% compared to its value when dry. The operation of PEDOT:PSS transistors is also treated in detail. It is demonstrated that their transistor behavior cannot be attributed solely to a field effect and that ion motion is key to the switching mechanism. It is also demonstrated that simple glucose sensors based on PEDOT:PSS OECTs are sensitive to low glucose concentrations below 1 mM, therefore showing promise for potential application in the field of noninvasive glucose monitoring for diabetic patients using saliva rather than blood samples. Furthermore, a novel microfluidic gating technique has been

  19. Examination of the ambient effects on the stability of amorphous indium-gallium-zinc oxide thin film transistors using a laser-glass-sealing technology

    SciTech Connect

    Yamada, Kazuo; Takeda, Satoshi; Nomura, Kenji; Abe, Katsumi; Hosono, Hideo

    2014-09-29

    The effect of an ambient atmosphere with a positive bias constant current stress (CCS) and a negative bias illumination stress (NBIS) on the stability of amorphous In-Ga-Zn-O thin film transistors (TFTs) is examined by utilizing a glass-hermetic-sealant with a moisture permeability of less than 10{sup −6} g/m{sup 2} · day. In the CCS test, the threshold voltage shift (ΔV{sub th}) was remarkably suppressed in the glass-sealed TFTs. The unsealed and resin-sealed TFTs exhibited large ΔV{sub th} values. During the NBIS tests, the glass-sealed TFTs had almost the same negative ΔV{sub th} as the unsealed and resin sealed TFTs. Among the different TFTs, no significant differences were observed in the threshold voltage, the subthreshold swing and the saturation mobility as a function of the photon energy. It is concluded that ambient molecules were the primary origin of the instability of the ΔV{sub th}, induced by a CCS, but they were not related to the NBIS instability. The major role of the effective passivation layers in the NBIS test was not to simply block out the ambient effects, but to reduce the extra density of states at/near the surface of the back channel.

  20. Ion beam-based characterization of multicomponent oxide thin films and thin film layered structures

    SciTech Connect

    Krauss, A.R.; Rangaswamy, M.; Lin, Yuping; Gruen, D.M.; Schultz, J.A.; Schmidt, H.K.; Chang, R.P.H.

    1992-11-01

    Fabrication of thin film layered structures of multi-component materials such as high temperature superconductors, ferroelectric and electro-optic materials, and alloy semiconductors, and the development of hybrid materials requires understanding of film growth and interface properties. For High Temperature Superconductors, the superconducting coherence length is extremely short (5--15 {Angstrom}), and fabrication of reliable devices will require control of film properties at extremely sharp interfaces; it will be necessary to verify the integrity of thin layers and layered structure devices over thicknesses comparable to the atomic layer spacing. Analytical techniques which probe the first 1--2 atomic layers are therefore necessary for in-situ characterization of relevant thin film growth processes. However, most surface-analytical techniques are sensitive to a region within 10--40 {Angstrom} of the surface and are physically incompatible with thin film deposition and are typically restricted to ultra high vacuum conditions. A review of ion beam-based analytical methods for the characterization of thin film and multi-layered thin film structures incorporating layers of multicomponent oxides is presented. Particular attention will be paid to the use of time-of-flight techniques based on the use of 1- 15 key ion beams which show potential for use as nondestructive, real-time, in-situ surface diagnostics for the growth of multicomponent metal and metal oxide thin films.

  1. Printed organic thin-film transistor-based integrated circuits

    NASA Astrophysics Data System (ADS)

    Mandal, Saumen; Noh, Yong-Young

    2015-06-01

    Organic electronics is moving ahead on its journey towards reality. However, this technology will only be possible when it is able to meet specific criteria including flexibility, transparency, disposability and low cost. Printing is one of the conventional techniques to deposit thin films from solution-based ink. It is used worldwide for visual modes of information, and it is now poised to enter into the manufacturing processes of various consumer electronics. The continuous progress made in the field of functional organic semiconductors has achieved high solubility in common solvents as well as high charge carrier mobility, which offers ample opportunity for organic-based printed integrated circuits. In this paper, we present a comprehensive review of all-printed organic thin-film transistor-based integrated circuits, mainly ring oscillators. First, the necessity of all-printed organic integrated circuits is discussed; we consider how the gap between printed electronics and real applications can be bridged. Next, various materials for printed organic integrated circuits are discussed. The features of these circuits and their suitability for electronics using different printing and coating techniques follow. Interconnection technology is equally important to make this product industrially viable; much attention in this review is placed here. For high-frequency operation, channel length should be sufficiently small; this could be achievable with a combination of surface treatment-assisted printing or laser writing. Registration is also an important issue related to printing; the printed gate should be perfectly aligned with the source and drain to minimize parasitic capacitances. All-printed organic inverters and ring oscillators are discussed here, along with their importance. Finally, future applications of all-printed organic integrated circuits are highlighted.

  2. Silicon thin-film transistor backplanes on flexible substrates

    NASA Astrophysics Data System (ADS)

    Kattamis, Alexis Z.

    Flexible large area electronics, especially for displays, is a rapidly growing field. Since hydrogenated amorphous silicon thin-film transistors (a-Si:H TFTs) have become the industry standard for liquid crystal displays, it makes sense that they be used in any transition from glass substrates to flexible substrates. The goal of this thesis work was to implement a-Si:H backplane technology on stainless steel and clear plastic substrates, with minimal recipe changes to ensure high device quality. When fabricating TFTs on flexible substrates many new issues arise, from thin-film fracture to overlay alignment errors. Our approach was to maintain elevated deposition temperatures (˜300°C) and engineer methods to minimize these problems, rather than reducing deposition temperatures. The resulting TFTs exhibit more stable operation than their low temperature counterparts and are therefore similar to the TFTs produced on glass. Two display projects using a-Si:H TFTs will be discussed in detail. They are an active-matrix organic light emitting display (AMOLED) on stainless steel and an active-matrix electrophoretic display (AMEPD) on clear plastic, with TFTs deposited at 250°C-280°C. Achieving quality a-Si:H TFTs on these substrates required addressing a host of technical challenges, including surface roughness and feature misalignment. Nanocrystalline silicon (nc-Si) was also implemented on a clear plastic substrate as a possible alternative to a-Si:H. nc-Si:H TFTs can be deposited using the same techniques as a-Si:H but yield carrier mobilities one order of magnitude greater. Their large mobilities could enable high resolution OLED displays and system-on-panel electronics.

  3. Mechanical and Electronic Properties of Thin-Film Transistors on Plastic, and Their Integration in Flexible Electronic Applications.

    PubMed

    Heremans, Paul; Tripathi, Ashutosh K; de Jamblinne de Meux, Albert; Smits, Edsger C P; Hou, Bo; Pourtois, Geoffrey; Gelinck, Gerwin H

    2016-06-01

    The increasing interest in flexible electronics and flexible displays raises questions regarding the inherent mechanical properties of the electronic materials used. Here, the mechanical behavior of thin-film transistors used in active-matrix displays is considered. The change of electrical performance of thin-film semiconductor materials under mechanical stress is studied, including amorphous oxide semiconductors. This study comprises an experimental part, in which transistor structures are characterized under different mechanical loads, as well as a theoretical part, in which the changes in energy band structures in the presence of stress and strain are investigated. The performance of amorphous oxide semiconductors are compared to reported results on organic semiconductors and covalent semiconductors, i.e., amorphous silicon and polysilicon. In order to compare the semiconductor materials, it is required to include the influence of the other transistor layers on the strain profile. The bending limits are investigated, and shown to be due to failures in the gate dielectric and/or the contacts. Design rules are proposed to minimize strain in transistor stacks and in transistor arrays. Finally, an overview of the present and future applications of flexible thin-film transistors is given, and the suitability of the different material classes for those applications is assessed. PMID:26707947

  4. Galvanostatic Ion Detrapping Rejuvenates Oxide Thin Films.

    PubMed

    Arvizu, Miguel A; Wen, Rui-Tao; Primetzhofer, Daniel; Klemberg-Sapieha, Jolanta E; Martinu, Ludvik; Niklasson, Gunnar A; Granqvist, Claes G

    2015-12-01

    Ion trapping under charge insertion-extraction is well-known to degrade the electrochemical performance of oxides. Galvanostatic treatment was recently shown capable to rejuvenate the oxide, but the detailed mechanism remained uncertain. Here we report on amorphous electrochromic (EC) WO3 thin films prepared by sputtering and electrochemically cycled in a lithium-containing electrolyte under conditions leading to severe loss of charge exchange capacity and optical modulation span. Time-of-flight elastic recoil detection analysis (ToF-ERDA) documented pronounced Li(+) trapping associated with the degradation of the EC properties and, importantly, that Li(+) detrapping, caused by a weak constant current drawn through the film for some time, could recover the original EC performance. Thus, ToF-ERDA provided direct and unambiguous evidence for Li(+) detrapping. PMID:26599729

  5. Electrochromism: from oxide thin films to devices

    NASA Astrophysics Data System (ADS)

    Rougier, A.; Danine, A.; Faure, C.; Buffière, S.

    2014-03-01

    In respect of their adaptability and performance, electrochromic devices, ECDs, which are able to change their optical properties under an applied voltage, have received significant attention. Target applications are multifold both in the visible region (automotive sunroofs, smart windows, ophthalmic lenses, and domestic appliances (oven, fridge…)) and in the infrared region (Satellites Thermal Control, IR furtivity). In our group, focusing on oxide thin films grown preferentially at room temperature, optimization of ECDs performances have been achieved by tuning the microstructure, the stoichiometry and the cationic composition of the various layers. Herein, our approach for optimized ECDs is illustrated through the example of WO3 electrochromic layer in the visible and in the IR domain as well as ZnO based transparent conducting oxide layer. Targeting the field of printed electronics, simplification of the device architecture for low power ECDs is also reported.

  6. Transparent Conductive Oxides in Thin Film Photovoltaics

    NASA Astrophysics Data System (ADS)

    Hamelmann, Frank U.

    2014-11-01

    This paper show results from the development of transparent conductive oxides (TCO's) on large areas for the use as front electrode in thin film silicon solar modules. It is focused on two types of zinc oxide, which are cheap to produce and scalable to a substrate size up to 6 m2. Low pressure CVD with temperatures below 200°C can be used for the deposition of boron doped ZnO with a native surface texture for good light scattering, while sputtered aluminum doped ZnO needs a post deposition treatment in an acid bath for a rough surface. The paper presents optical and electrical characterization of large area samples, and also results about long term stability of the ZnO samples with respect to the so called TCO corrosion.

  7. Black Phosphorus Flexible Thin Film Transistors at Gighertz Frequencies.

    PubMed

    Zhu, Weinan; Park, Saungeun; Yogeesh, Maruthi N; McNicholas, Kyle M; Bank, Seth R; Akinwande, Deji

    2016-04-13

    Black phosphorus (BP) has attracted rapidly growing attention for high speed and low power nanoelectronics owing to its compelling combination of tunable bandgap (0.3 to 2 eV) and high carrier mobility (up to ∼1000 cm(2)/V·s) at room temperature. In this work, we report the first radio frequency (RF) flexible top-gated (TG) BP thin-film transistors on highly bendable polyimide substrate for GHz nanoelectronic applications. Enhanced p-type charge transport with low-field mobility ∼233 cm(2)/V·s and current density of ∼100 μA/μm at VDS = -2 V were obtained from flexible BP transistor at a channel length L = 0.5 μm. Importantly, with optimized dielectric coating for air-stability during microfabrication, flexible BP RF transistors afforded intrinsic maximum oscillation frequency fMAX ∼ 14.5 GHz and unity current gain cutoff frequency fT ∼ 17.5 GHz at a channel length of 0.5 μm. Notably, the experimental fT achieved here is at least 45% higher than prior results on rigid substrate, which is attributed to the improved air-stability of fabricated BP devices. In addition, the high-frequency performance was investigated through mechanical bending test up to ∼1.5% tensile strain, which is ultimately limited by the inorganic dielectric film rather than the 2D material. Comparison of BP RF devices to other 2D semiconductors clearly indicates that BP offers the highest saturation velocity, an important metric for high-speed and RF flexible nanosystems. PMID:26977902

  8. Solid-state thin-film supercapacitor with ruthenium oxide and solid electrolyte thin films

    NASA Astrophysics Data System (ADS)

    Yoon, Y. S.; Cho, W. I.; Lim, J. H.; Choi, D. J.

    Direct current reactive sputtering deposition of ruthenium oxide thin films (bottom and top electrodes) at 400°C are performed to produce a solid-state thin-film supercapacitor (TFSC). The supercapacitor has a cell structure of RuO 2/Li 2.94PO 2.37N 0.75 (Lipon)/RuO 2/Pt. Radio frequency, reactive sputtering deposition of an Li 2.94PO 2.37N 0.75 electrolyte film is performed on the bottom RuO 2 film at room temperature to separate the bottom and top RuO 2 electrodes electrically. The stoichiometry of the RuO 2 thin film is investigated by Rutherford back-scattering spectrometry (RBS). X-ray diffraction (XRD) shows that the as-deposited RuO 2 thin film is an amorphous phase. Scanning electron microscopy (SEM) measurements reveal that the RuO 2/Lipon/RuO 2 hetero-interfaces have no inter-diffusion problems. Charge-discharge measurements with constant current at room temperature clearly reveal typical supercapacitor behaviour for a RuO 2/Lipon/RuO 2/Pt cell structure. Since the electrolyte thin film has low ionic mobility, the capacity and cycle performance are inferior to those of a bulk type of supercapacitor. These results indicate that a high performance, TFSC can be fabricated by a solid electrolyte thin film with high ionic conductivity.

  9. Improvement in the Positive Bias Temperature Stability of SnOx-Based Thin Film Transistors by Hf and Zn Doping.

    PubMed

    Han, Dongsuk; Park, Jaehyung; Kang, Minsoo; Jeon, Hyeongtag; Park, Jongwan

    2015-10-01

    We investigated the performance of tin oxide thin film transistors (TFTs) using DC magnetron sputtering. A remarkable improvement in the transfer characteristics was obtained for the Hf-doped tin oxide (HTO) TFT. We also developed amorphous hafnium-zinc-tin oxide (HZTO) thin film transistors and investigated the effects of hafnium doping on the electrical characteristics of the HTO TFTs. Doping with hafnium resulted in a reduced defect density in the tin oxide channel layer related to oxygen vacancies, which may result from increased field effect mobility. Zinc atoms have relatively higher oxidation potential compared to tin atoms, so more oxygen molecules can be absorbed and more electrons are trapped in the HZTO films. The HZTO TFTs exhibited good electrical characteristics with a field effect mobility of 10.98 cm2/Vs, and a high ION/IOFF ratio over 10(8). PMID:26726382

  10. Structural characterization of impurified zinc oxide thin films

    SciTech Connect

    Trinca, L. M.; Galca, A. C. Stancu, V. Chirila, C. Pintilie, L.

    2014-11-05

    Europium doped zinc oxide (Eu:ZnO) thin films have been obtained by pulsed laser deposition (PLD). 002 textured thin films were achieved on glass and silicon substrates, while hetero-epilayers and homo-epilayers have been attained on single crystal SrTiO{sub 3} and ZnO, respectively. X-ray Diffraction (XRD) was employed to characterize the Eu:ZnO thin films. Extended XRD studies confirmed the different thin film structural properties as function of chosen substrates.

  11. Zinc Oxide Thin Films Fabricated with Direct Current Magnetron Sputtering Deposition Technique

    SciTech Connect

    Hoon, Jian-Wei; Chan, Kah-Yoong; Krishnasamy, Jegenathan; Tou, Teck-Yong

    2011-03-30

    Zinc oxide (ZnO) is a very promising material for emerging large area electronic applications including thin-film sensors, transistors and solar cells. We fabricated ZnO thin films by employing direct current (DC) magnetron sputtering deposition technique. ZnO films with different thicknesses ranging from 100 nm to 1020 nm were deposited on silicon (Si) substrate. The deposition pressure was varied from 12 mTorr to 25 mTorr. The influences of the film thickness and the deposition pressure on structural properties of the ZnO films were investigated using Mahr surface profilometer and atomic force microscopy (AFM). The experimental results reveal that the film thickness and the deposition pressure play significant role in the structural formation of the deposited ZnO thin films. ZnO films deposited on Si substrates are promising for variety of thin-film sensor applications.

  12. Temperature Dependence of Field-Effect Mobility in Organic Thin-Film Transistors: Similarity to Inorganic Transistors.

    PubMed

    Okada, Jun; Nagase, Takashi; Kobayashi, Takashi; Naito, Hiroyoshi

    2016-04-01

    Carrier transport in solution-processed organic thin-film transistors (OTFTs) based on dioctylbenzothienobenzothiophene (C8-BTBT) has been investigated in a wide temperature range from 296 to 10 K. The field-effect mobility shows thermally activated behavior whose activation energy becomes smaller with decreasing temperature. The temperature dependence of field-effect mobility found in C8-BTBT is similar to that of others materials: organic semiconducting polymers, amorphous oxide semiconductors and hydrogenated amorphous silicon. These results indicate that hopping transport between isoenergetic localized states becomes dominated in a low temperature regime in these materials. PMID:27451607

  13. Electrochromism in copper oxide thin films

    SciTech Connect

    Richardson, T.J.; Slack, J.L.; Rubin, M.D.

    2000-08-15

    Transparent thin films of copper(I) oxide prepared on conductive SnO2:F glass substrates by anodic oxidation of sputtered copper films or by direct electrodeposition of Cu2O transformed reversibly to opaque metallic copper films when reduced in alkaline electrolyte. In addition, the same Cu2O films transform reversibly to black copper(II) oxide when cycled at more anodic potentials. Copper oxide-to-copper switching covered a large dynamic range, from 85% and 10% photopic transmittance, with a coloration efficiency of about 32 cm2/C. Gradual deterioration of the switching range occurred over 20 to 100 cycles. This is tentatively ascribed to coarsening of the film and contact degradation caused by the 65% volume change on conversion of Cu to Cu2O. Switching between the two copper oxides (which have similar volumes) was more stable and more efficient (CE = 60 cm2/C), but covered a smaller transmittance range (60% to 44% T). Due to their large electrochemical storage capacity and tolerance for alkaline electrolytes, these cathodically coloring films may be useful as counter electrodes for anodically coloring electrode films such as nickel oxide or metal hydrides.

  14. High field breakdown characteristics of carbon nanotube thin film transistors.

    PubMed

    Gupta, Man Prakash; Behnam, Ashkan; Lian, Feifei; Estrada, David; Pop, Eric; Kumar, Satish

    2013-10-11

    The high field properties of carbon nanotube (CNT) network thin film transistors (CN-TFTs) are important for their practical operation, and for understanding their reliability. Using a combination of experimental and computational techniques we show how the channel geometry (length L(C) and width W(C)) and network morphology (average CNT length L(t) and alignment angle distribution θ) affect heat dissipation and high field breakdown in such devices. The results suggest that when WC ≥ L(t), the breakdown voltage remains independent of W(C) but varies linearly with L(C). The breakdown power varies almost linearly with both W(C) and L(C) when WC > L(t). We also find that the breakdown power is more susceptible to the variability in the network morphology compared to the breakdown voltage. The analysis offers new insight into the tunable heat dissipation and thermal reliability of CN-TFTs, which can be significantly improved through optimization of the network morphology and device geometry. PMID:24029606

  15. Thin-films and transistors of p-ZnTe

    NASA Astrophysics Data System (ADS)

    Lastra, G.; Olivas, A.; Mejía, J. I.; Quevedo-López, M. A.

    2016-02-01

    In this article, we report (IDS-VDS) characteristics of (75 and 35 nm) p-type ZnTe thin-film transistors (TFTs) at different active channels by photolithography. In 75 nm p-ZnTe TFTs, the source and drain contacts were doped with Cu in 11, 13 and 15 mg (Cu(NO3)2-3H2O)/150 ml (H2O) for 60 s and heated at 300 °C for 10 min. TFTs immersed in 15 mg solution showed the clearest linear and saturation regions, as well as an approximate mobility from 10-2 to 10-4 cm2/V s. Also, drain- currents (IDS) from 10-8 to ∼10-7 A were shown at VG = 0 V (OFF-state). However, drain-current in the OFF-state decreased in 35 nm p-ZnTe TFTs. The films showed the cubic phase and the Cu1.44Te-like orthorhombic phase.

  16. Hysteresis in pentacene-based organic thin-film transistors

    NASA Astrophysics Data System (ADS)

    Gu, Gong; Kane, Michael G.

    2006-08-01

    Memory effects are commonly seen in organic thin-film transistor (OTFT) characteristics. In the absence of memory effects associated with the gate dielectric, the hysteresis in p-channel pentacene-based OTFTs, as measured in air and under illumination, was found to be dominated by trapped electrons, rather than trapped holes, in the semiconductor. The responsible acceptor type traps have very long lifetime. The immobile, previously stored negative charge requires extra holes to balance it, resulting in early establishment of the channel and extra drain current. This model is unique in that it discusses the majority carrier population influenced by trapped charge opposite in sign to the majority carriers in a simple electrostatic manner, to explain history dependence. The model was supported by drain current transient decay data. This memory effect is ambient and illumination sensitive. We studied the presence or absence of this effect under various ambient and illumination conditions, and found the responsible acceptor type traps mostly extrinsic and their formation reversible. Efforts were taken in the quantitative analysis to exclude the bias stress effect from the memory effect due to the charged acceptors.

  17. Electron and hole transport in ambipolar, thin film pentacene transistors

    SciTech Connect

    Saudari, Sangameshwar R.; Kagan, Cherie R.

    2015-01-21

    Solution-processed, ambipolar, thin-film pentacene field-effect transistors were employed to study both electron and hole transport simultaneously in a single, organic solid-state device. Electron and hole mobilities were extracted from the respective unipolar saturation regimes and show thermally activated behavior and gate voltage dependence. We fit the gate voltage dependent saturation mobility to a power law to extract the characteristic Meyer-Neldel (MN) energy, a measure of the width of the exponential distribution of localized states extending into the energy gap of the organic semiconductor. The MN energy is ∼78 and ∼28 meV for electrons and holes, respectively, which reflects a greater density of localized tail states for electrons than holes. This is consistent with the lower measured electron than hole mobility. For holes, the well-behaved linear regime allows for four-point probe measurement of the contact resistance independent mobility and separate characterization of the width of the localized density of states, yielding a consistent MN energy of 28 meV.

  18. Ambipolar charge transport in microcrystalline silicon thin-film transistors

    SciTech Connect

    Knipp, Dietmar; Marinkovic, M.; Chan, Kah-Yoong; Gordijn, Aad; Stiebig, Helmut

    2011-01-15

    Hydrogenated microcrystalline silicon ({mu}c-Si:H) is a promising candidate for thin-film transistors (TFTs) in large-area electronics due to high electron and hole charge carrier mobilities. We report on ambipolar TFTs based on {mu}c-Si:H prepared by plasma-enhanced chemical vapor deposition at temperatures compatible with flexible substrates. Electrons and holes are directly injected into the {mu}c-Si:H channel via chromium drain and source contacts. The TFTs exhibit electron and hole charge carrier mobilities of 30-50 cm{sup 2}/V s and 10-15 cm{sup 2}/V s, respectively. In this work, the electrical characteristics of the ambipolar {mu}c-Si:H TFTs are described by a simple analytical model that takes the ambipolar charge transport into account. The analytical expressions are used to model the transfer curves, the potential and the net surface charge along the channel of the TFTs. The electrical model provides insights into the electronic transport of ambipolar {mu}c-Si:H TFTs.

  19. Remarkable changes in interface O vacancy and metal-oxide bonds in amorphous indium-gallium-zinc-oxide thin-film transistors by long time annealing at 250 °C

    SciTech Connect

    Chowdhury, Md Delwar Hossain; Um, Jae Gwang; Jang, Jin

    2014-12-08

    We have studied the effect of long time post-fabrication annealing on negative bias illumination stress (NBIS) of amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film-transistors. Annealing for 100 h at 250 °C increased the field effect mobility from 14.7 cm{sup 2}/V s to 17.9 cm{sup 2}/V s and reduced the NBIS instability remarkably. Using X-ray photoelectron spectroscopy, the oxygen vacancy and OH were found to exist at the interfaces of a-IGZO with top and bottom SiO{sub 2}. Long time annealing helps to decrease the vacancy concentration and increase the metal-oxygen bonds at the interfaces; this leads to increase in the free carrier concentrations in a-IGZO and field-effect mobility. X-ray reflectivity measurement indicated the increment of a-IGZO film density of 5.63 g cm{sup −3} to 5.83 g cm{sup −3} (3.4% increase) by 100 h annealing at 250 °C. The increase in film density reveals the decrease of O vacancy concentration and reduction of weak metal-oxygen bonds in a-IGZO, which substantially helps to improve the NBIS stability.

  20. Electrically tunable terahertz metamaterials with embedded large-area transparent thin-film transistor arrays

    PubMed Central

    Xu, Wei-Zong; Ren, Fang-Fang; Ye, Jiandong; Lu, Hai; Liang, Lanju; Huang, Xiaoming; Liu, Mingkai; Shadrivov, Ilya V.; Powell, David A.; Yu, Guang; Jin, Biaobing; Zhang, Rong; Zheng, Youdou; Tan, Hark Hoe; Jagadish, Chennupati

    2016-01-01

    Engineering metamaterials with tunable resonances are of great importance for improving the functionality and flexibility of terahertz (THz) systems. An ongoing challenge in THz science and technology is to create large-area active metamaterials as building blocks to enable efficient and precise control of THz signals. Here, an active metamaterial device based on enhancement-mode transparent amorphous oxide thin-film transistor arrays for THz modulation is demonstrated. Analytical modelling based on full-wave techniques and multipole theory exhibits excellent consistent with the experimental observations and reveals that the intrinsic resonance mode at 0.75 THz is dominated by an electric response. The resonant behavior can be effectively tuned by controlling the channel conductivity through an external bias. Such metal/oxide thin-film transistor based controllable metamaterials are energy saving, low cost, large area and ready for mass-production, which are expected to be widely used in future THz imaging, sensing, communications and other applications. PMID:27000419

  1. Electrically tunable terahertz metamaterials with embedded large-area transparent thin-film transistor arrays

    NASA Astrophysics Data System (ADS)

    Xu, Wei-Zong; Ren, Fang-Fang; Ye, Jiandong; Lu, Hai; Liang, Lanju; Huang, Xiaoming; Liu, Mingkai; Shadrivov, Ilya V.; Powell, David A.; Yu, Guang; Jin, Biaobing; Zhang, Rong; Zheng, Youdou; Tan, Hark Hoe; Jagadish, Chennupati

    2016-03-01

    Engineering metamaterials with tunable resonances are of great importance for improving the functionality and flexibility of terahertz (THz) systems. An ongoing challenge in THz science and technology is to create large-area active metamaterials as building blocks to enable efficient and precise control of THz signals. Here, an active metamaterial device based on enhancement-mode transparent amorphous oxide thin-film transistor arrays for THz modulation is demonstrated. Analytical modelling based on full-wave techniques and multipole theory exhibits excellent consistent with the experimental observations and reveals that the intrinsic resonance mode at 0.75 THz is dominated by an electric response. The resonant behavior can be effectively tuned by controlling the channel conductivity through an external bias. Such metal/oxide thin-film transistor based controllable metamaterials are energy saving, low cost, large area and ready for mass-production, which are expected to be widely used in future THz imaging, sensing, communications and other applications.

  2. Electrically tunable terahertz metamaterials with embedded large-area transparent thin-film transistor arrays.

    PubMed

    Xu, Wei-Zong; Ren, Fang-Fang; Ye, Jiandong; Lu, Hai; Liang, Lanju; Huang, Xiaoming; Liu, Mingkai; Shadrivov, Ilya V; Powell, David A; Yu, Guang; Jin, Biaobing; Zhang, Rong; Zheng, Youdou; Tan, Hark Hoe; Jagadish, Chennupati

    2016-01-01

    Engineering metamaterials with tunable resonances are of great importance for improving the functionality and flexibility of terahertz (THz) systems. An ongoing challenge in THz science and technology is to create large-area active metamaterials as building blocks to enable efficient and precise control of THz signals. Here, an active metamaterial device based on enhancement-mode transparent amorphous oxide thin-film transistor arrays for THz modulation is demonstrated. Analytical modelling based on full-wave techniques and multipole theory exhibits excellent consistent with the experimental observations and reveals that the intrinsic resonance mode at 0.75 THz is dominated by an electric response. The resonant behavior can be effectively tuned by controlling the channel conductivity through an external bias. Such metal/oxide thin-film transistor based controllable metamaterials are energy saving, low cost, large area and ready for mass-production, which are expected to be widely used in future THz imaging, sensing, communications and other applications. PMID:27000419

  3. Highly conductive grain boundaries in copper oxide thin films

    NASA Astrophysics Data System (ADS)

    Deuermeier, Jonas; Wardenga, Hans F.; Morasch, Jan; Siol, Sebastian; Nandy, Suman; Calmeiro, Tomás; Martins, Rodrigo; Klein, Andreas; Fortunato, Elvira

    2016-06-01

    High conductivity in the off-state and low field-effect mobility compared to bulk properties is widely observed in the p-type thin-film transistors of Cu2O, especially when processed at moderate temperature. This work presents results from in situ conductance measurements at thicknesses from sub-nm to around 250 nm with parallel X-ray photoelectron spectroscopy. An enhanced conductivity at low thickness is explained by the occurrence of Cu(II), which is segregated in the grain boundary and locally causes a conductivity similar to CuO, although the surface of the thick film has Cu2O stoichiometry. Since grains grow with an increasing film thickness, the effect of an apparent oxygen excess is most pronounced in vicinity to the substrate interface. Electrical properties of Cu2O grains are at least partially short-circuited by this effect. The study focuses on properties inherent to copper oxide, although interface effects cannot be ruled out. This non-destructive, bottom-up analysis reveals phenomena which are commonly not observable after device fabrication, but clearly dominate electrical properties of polycrystalline thin films.

  4. Conduction mechanism in amorphous InGaZnO thin film transistors

    NASA Astrophysics Data System (ADS)

    Bhoolokam, Ajay; Nag, Manoj; Steudel, Soeren; Genoe, Jan; Gelinck, Gerwin; Kadashchuk, Andrey; Groeseneken, Guido; Heremans, Paul

    2016-01-01

    We validate a model which is a combination of multiple trapping and release and percolation model for describing the conduction mechanism in amorphous indium gallium zinc oxide (a-IGZO) thin film transistors (TFT). We show that using just multiple trapping and release or percolation model is insufficient to explain TFT behavior as a function of temperature. We also show the intrinsic mobility is dependent on temperature due to scattering by ionic impurities or lattice. In solving the Poisson equation to find the surface potential and back potential as a function of gate voltage, we explicitly allow for the back surface to be floating, as is the case for a-IGZO transistors. The parameters for gap states, percolation barriers and intrinsic mobility at room temperature that we extract with this comprehensive model are in good agreement with those extracted in literature with partially-complete models.

  5. Thin-Film Transistor and Ultra-Large Scale Integrated Circuit: Competition or Collaboration

    NASA Astrophysics Data System (ADS)

    Kuo, Yue

    2008-03-01

    Thin-film transistor (TFT) and ultra-large scale integrated circuit (ULSIC) have been compared and discussed with respect to the development history, technology trends, and applications. Detailed issues on materials, processes, and devices in the large-area TFT array fabrication and nano-size metal-oxide-semiconductor field effect transistors (MOSFETs) composed ULSIC on large wafers were also examined. The TFT fabrication processes were originally derived from ULSIC. However, there are many unique large-area processes and theories developed during the study of the TFT array fabrication, which can greatly benefit the future large wafer ULSIC production process. Although their future applications will be in different areas, there are opportunities that TFTs can be integrated into ULSIC products to enhance the functions and performance.

  6. Restorative effect of oxygen annealing on device performance in HfIZO thin-film transistors

    SciTech Connect

    Ha, Tae-Jun

    2015-03-15

    Metal-oxide based thin-film transistors (oxide-TFTs) are very promising for use in next generation electronics such as transparent displays requiring high switching and driving performance. In this study, we demonstrate an optimized process to secure excellent device performance with a favorable shift of the threshold voltage toward 0V in amorphous hafnium-indium-zinc-oxide (a-HfIZO) TFTs by using post-treatment with oxygen annealing. This enhancement results from the improved interfacial characteristics between gate dielectric and semiconductor layers due to the reduction in the density of interfacial states related to oxygen vacancies afforded by oxygen annealing. The device statistics confirm the improvement in the device-to-device and run-to-run uniformity. We also report on the photo-induced stability in such oxide-TFTs against long-term UV irradiation, which is significant for transparent displays.

  7. Restorative effect of oxygen annealing on device performance in HfIZO thin-film transistors

    NASA Astrophysics Data System (ADS)

    Ha, Tae-Jun

    2015-03-01

    Metal-oxide based thin-film transistors (oxide-TFTs) are very promising for use in next generation electronics such as transparent displays requiring high switching and driving performance. In this study, we demonstrate an optimized process to secure excellent device performance with a favorable shift of the threshold voltage toward 0V in amorphous hafnium-indium-zinc-oxide (a-HfIZO) TFTs by using post-treatment with oxygen annealing. This enhancement results from the improved interfacial characteristics between gate dielectric and semiconductor layers due to the reduction in the density of interfacial states related to oxygen vacancies afforded by oxygen annealing. The device statistics confirm the improvement in the device-to-device and run-to-run uniformity. We also report on the photo-induced stability in such oxide-TFTs against long-term UV irradiation, which is significant for transparent displays.

  8. Method of producing solution-derived metal oxide thin films

    DOEpatents

    Boyle, Timothy J.; Ingersoll, David

    2000-01-01

    A method of preparing metal oxide thin films by a solution method. A .beta.-metal .beta.-diketonate or carboxylate compound, where the metal is selected from groups 8, 9, 10, 11, and 12 of the Periodic Table, is solubilized in a strong Lewis base to form a homogeneous solution. This precursor solution forms within minutes and can be deposited on a substrate in a single layer or a multiple layers to form a metal oxide thin film. The substrate with the deposited thin film is heated to change the film from an amorphous phase to a ceramic metal oxide and cooled.

  9. Photo-Patterned Ion Gel Electrolyte-Gated Thin Film Transistors

    NASA Astrophysics Data System (ADS)

    Choi, Jae-Hong; Gu, Yuanyan; Hong, Kihyun; Frisbie, C. Daniel; Lodge, Timothy P.

    2014-03-01

    We have developed a novel fabrication route to pattern electrolyte thin films in electrolyte-gated transistors (EGTs) using a chemically crosslinkable ABA-triblock copolymer ion gel. In the self-assembly of poly[(styrene-r-vinylbenzylazide)-b-ethylene oxide-b-(styrene-r-vinylbenzylazide)] (SOS-N3) triblock copolymer and the ionic liquid, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMI][TFSI]), the azide groups of poly(styrene-r-vinylbenzylazide) (PS-N3) end-blocks in the cores can be chemically cross-linked via UV irradiation (λ = 254 nm). Impedance spectroscopy and small-angle X-ray scattering confirmed that ion transport and microstructure of the ion gel are not affected by UV cross-linking. Using this chemical cross-linking strategy, we demonstrate a photo-patterning of ion gels through a patterned mask and the fabricated electrolyte-gated thin film transistors with photo-patterned ion gels as high-capacitance gate insulators exhibited high device performance (low operation voltages and high on/off current ratios).

  10. In situ preparation, electrical and surface analytical characterization of pentacene thin film transistors

    PubMed Central

    Lassnig, R.; Striedinger, B.; Hollerer, M.; Fian, A.; Stadlober, B.; Winkler, A.

    2015-01-01

    The fabrication of organic thin film transistors with highly reproducible characteristics presents a very challenging task. We have prepared and analyzed model pentacene thin film transistors under ultra-high vacuum conditions, employing surface analytical tools and methods. Intentionally contaminating the gold contacts and SiO2 channel area with carbon through repeated adsorption, dissociation, and desorption of pentacene proved to be very advantageous in the creation of devices with stable and reproducible parameters. We mainly focused on the device properties, such as mobility and threshold voltage, as a function of film morphology and preparation temperature. At 300 K, pentacene displays Stranski-Krastanov growth, whereas at 200 K fine-grained, layer-like film growth takes place, which predominantly influences the threshold voltage. Temperature dependent mobility measurements demonstrate good agreement with the established multiple trapping and release model, which in turn indicates a predominant concentration of shallow traps in the crystal grains and at the oxide-semiconductor interface. Mobility and threshold voltage measurements as a function of coverage reveal that up to four full monolayers contribute to the overall charge transport. A significant influence on the effective mobility also stems from the access resistance at the gold contact-semiconductor interface, which is again strongly influenced by the temperature dependent, characteristic film growth mode. PMID:25814770

  11. Pulsed Laser Deposition of Oxide Thin Films

    NASA Astrophysics Data System (ADS)

    Brodoceanu, D.; Scarisoreanu, N. D.; Filipescu, M. (Morar); Epurescu, G. N.; Matei, D. G.; Verardi, P.; Craciun, F.; Dinescu, M.

    2004-10-01

    Pulsed Laser Deposition (PLD) emerged as an attractive technique for growth of thin films with different properties as metals, semiconductors, ferroelectrics, biocompatibles, polymers, etc., due to its important advantages: (i) the stoichiometric transfer of a complex composition from target to film and film crystallization at lower substrate temperature respect to other techniques (due to the high energy of species in the laser plasma); (ii) single step process, synthesis and deposition; (iii) creation in plasma of species impossible to be obtained by other processes; (iv) possibility of "in situ" heterostructure deposition using a multi-target system, etc. Simple or complex oxides are between the materials widely studied for their applications. PMN is the most known relaxor ferroelectric material: it exhibits a high dielectric constant value around the (diffuse) maximum phase transition temperature, of more than 35 000 in bulk form. Other oxides as lead zirconate titanate, Pb(ZrxTi1-x)O3 simple or La doped exhibit exceptional properties as large remanent polarization, high dielectric permittivity, high piezoelectric coefficient. SrBi2Ta2O9 (SBT) is characterized by a high "fatigue resistance" (constant remanent polarization until 1012 switching cycles), low imprint, and low leakage current. The physical properties of zirconium oxide (or zirconia) -- high strength, stability at high temperatures -- make it useful for applications involving gas sensors, corrosion or heat resistant mechanical parts, high refractive index optical coatings. Of particular interest is its use as an alternative gate dielectric in metal-oxide-semiconductor (MOS) devices or capacitor in dynamic random access memory (DRAM) chips. All these oxides have been deposited by laser ablation in oxygen reactive atmosphere and some of their properties will be presented in this paper.

  12. Molecular doping for control of gate bias stress in organic thin film transistors

    SciTech Connect

    Hein, Moritz P. Lüssem, Björn; Jankowski, Jens; Tietze, Max L.; Riede, Moritz K.; Zakhidov, Alexander A.; Leo, Karl; Fraunhofer COMEDD, Maria-Reiche-Str. 2, 01109 Dresden

    2014-01-06

    The key active devices of future organic electronic circuits are organic thin film transistors (OTFTs). Reliability of OTFTs remains one of the most challenging obstacles to be overcome for broad commercial applications. In particular, bias stress was identified as the key instability under operation for numerous OTFT devices and interfaces. Despite a multitude of experimental observations, a comprehensive mechanism describing this behavior is still missing. Furthermore, controlled methods to overcome these instabilities are so far lacking. Here, we present the approach to control and significantly alleviate the bias stress effect by using molecular doping at low concentrations. For pentacene and silicon oxide as gate oxide, we are able to reduce the time constant of degradation by three orders of magnitude. The effect of molecular doping on the bias stress behavior is explained in terms of the shift of Fermi Level and, thus, exponentially reduced proton generation at the pentacene/oxide interface.

  13. Characterization of reliability of printed indium tin oxide thin films.

    PubMed

    Hong, Sung-Jei; Kim, Jong-Woong; Jung, Seung-Boo

    2013-11-01

    Recently, decreasing the amount of indium (In) element in the indium tin oxide (ITO) used for transparent conductive oxide (TCO) thin film has become necessary for cost reduction. One possible approach to this problem is using printed ITO thin film instead of sputtered. Previous studies showed potential for printed ITO thin films as the TCO layer. However, nothing has been reported on the reliability of printed ITO thin films. Therefore, in this study, the reliability of printed ITO thin films was characterized. ITO nanoparticle ink was fabricated and printed onto a glass substrate followed by heating at 400 degrees C. After measurement of the initial values of sheet resistance and optical transmittance of the printed ITO thin films, their reliabilities were characterized with an isothermal-isohumidity test for 500 hours at 85 degrees C and 85% RH, a thermal shock test for 1,000 cycles between 125 degrees C and -40 degrees C, and a high temperature storage test for 500 hours at 125 degrees C. The same properties were investigated after the tests. Printed ITO thin films showed stable properties despite extremely thermal and humid conditions. Sheet resistances of the printed ITO thin films changed slightly from 435 omega/square to 735 omega/square 507 omega/square and 442 omega/square after the tests, respectively. Optical transmittances of the printed ITO thin films were slightly changed from 84.74% to 81.86%, 88.03% and 88.26% after the tests, respectively. These test results suggest the stability of printed ITO thin film despite extreme environments. PMID:24245331

  14. Charge carrier transport in polycrystalline organic thin film based field effect transistors

    NASA Astrophysics Data System (ADS)

    Rani, Varsha; Sharma, Akanksha; Ghosh, Subhasis

    2016-05-01

    The charge carrier transport mechanism in polycrystalline thin film based organic field effect transistors (OFETs) has been explained using two competing models, multiple trapping and releases (MTR) model and percolation model. It has been shown that MTR model is most suitable for explaining charge carrier transport in grainy polycrystalline organic thin films. The energetic distribution of traps determined independently using Mayer-Neldel rule (MNR) is in excellent agreement with the values obtained by MTR model for copper phthalocyanine and pentacene based OFETs.

  15. Improvement of bias-stability in amorphous-indium-gallium-zinc-oxide thin-film transistors by using solution-processed Y{sub 2}O{sub 3} passivation

    SciTech Connect

    An, Sungjin; Mativenga, Mallory; Kim, Youngoo; Jang, Jin

    2014-08-04

    We demonstrate back channel improvement of back-channel-etch amorphous-indium-gallium-zinc-oxide (a-IGZO) thin-film transistors by using solution-processed yttrium oxide (Y{sub 2}O{sub 3}) passivation. Two different solvents, which are acetonitrile (35%) + ethylene glycol (65%), solvent A and deionized water, solvent B are investigated for the spin-on process of the Y{sub 2}O{sub 3} passivation—performed after patterning source/drain (S/D) Mo electrodes by a conventional HNO{sub 3}-based wet-etch process. Both solvents yield devices with good performance but those passivated by using solvent B exhibit better light and bias stability. Presence of yttrium at the a-IGZO back interface, where it occupies metal vacancy sites, is confirmed by X-ray photoelectron spectroscopy. The passivation effect of yttrium is more significant when solvent A is used because of the existence of more metal vacancies, given that the alcohol (65% ethylene glycol) in solvent A may dissolve the metal oxide (a-IGZO) through the formation of alkoxides and water.

  16. Organic ferroelectric gate field-effect transistor memory using high-mobility rubrene thin film

    NASA Astrophysics Data System (ADS)

    Kanashima, Takeshi; Katsura, Yuu; Okuyama, Masanori

    2014-01-01

    An organic ferroelectric gate field-effect transistor (FET) memory has been fabricated using an organic semiconductor of rubrene thin film with a high mobility and a gate insulating layer of poly(vinylidene fluoride-tetrafluoroethylene) [P(VDF-TeFE)] thin film. A rubrene thin-film sheet was grown by physical vapor transport (PVT), and placed onto a spin-coated P(VDF-TeFE) thin-film layer, and Au source and drain electrodes were formed on this rubrene thin film. A hysteresis loop of the drain current-gate voltage (ID-VG) characteristic has been clearly observed in the ferroelectric gate FET, and is caused by the ferroelectricity. The maximum drain current is 1.5 × 10-6 A, which is about two orders of magnitude larger than that of the P(VDF-TeFE) gate FET using a pentacene thin film. Moreover, the mobility of this organic ferroelectric gate FET using rubrene thin film is 0.71 cm2 V-1 s-1, which is 35 times larger than that of the FET with pentacene thin film.

  17. Suppression of excess oxygen for environmentally stable amorphous In-Si-O thin-film transistors

    SciTech Connect

    Aikawa, Shinya E-mail: TSUKAGOSHI.Kazuhito@nims.go.jp; Mitoma, Nobuhiko; Kizu, Takio; Tsukagoshi, Kazuhito E-mail: TSUKAGOSHI.Kazuhito@nims.go.jp; Nabatame, Toshihide

    2015-05-11

    We discuss the environmental instability of amorphous indium oxide (InO{sub x})-based thin-film transistors (TFTs) in terms of the excess oxygen in the semiconductor films. A comparison between amorphous InO{sub x} doped with low and high concentrations of oxygen binder (SiO{sub 2}) showed that out-diffusion of oxygen molecules causes drastic changes in the film conductivity and TFT turn-on voltages. Incorporation of sufficient SiO{sub 2} could suppress fluctuations in excess oxygen because of the high oxygen bond-dissociation energy and low Gibbs free energy. Consequently, the TFT operation became rather stable. The results would be useful for the design of reliable oxide TFTs with stable electrical properties.

  18. Gate bias stress effects due to polymer gate dielectrics in organic thin-film transistors

    NASA Astrophysics Data System (ADS)

    Ng, Tse Nga; Daniel, Jürgen H.; Sambandan, Sanjiv; Arias, Ana-Claudia; Chabinyc, Michael L.; Street, Robert A.

    2008-02-01

    The operational stability of organic thin-film transistors (OTFTs) comprising bilayer polymer dielectric of poly(methylsilsesquioxane) (pMSSQ) and either the epoxy resin SU-8 or poly(4-vinyl phenol) was examined. Although not in direct contact with the semiconductor materials, the bottom dielectric layer did affect OTFT stability through water ion movement or charge injection inside the bottom dielectrics. In the comparison between our best polymer dielectric pMSSQ/SU-8 to the silicon oxide dielectric, the result emphasized that, at equal initial charge concentration, polymer dielectrics did not alleviate threshold-voltage shift but did maintain more stable current due to the lower gate capacitance than silicon oxide.

  19. CROSS-DISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY: Growth Related Carrier Mobility Enhancement of Pentacene Thin-Film Transistors with High-k Oxide Gate Dielectric

    NASA Astrophysics Data System (ADS)

    Yu, Ai-Fang; Qi, Qiong; Jiang, Peng; Jiang, Chao

    2009-07-01

    Carrier mobility enhancement from 0.09 to 0.59 cm2/Vs is achieved for pentacene-based thin-film transistors (TFTs) by modifying the HfO2 gate dielectric with a polystyrene (PS) thin film. The improvement of the transistor's performance is found to be strongly related to the initial film morphologies of pentacene on the dielectrics. In contrast to the three-dimensional island-like growth mode on the HfO2 surface, the Stranski-Krastanov growth mode on the smooth and nonpolar PS/HfO2 surface is believed to be the origin of the excellent carrier mobility of the TFTs. A large well-connected first monolayer with fewer boundaries is formed via the Stranski-Krastanov growth mode, which facilitates a charge transport parallel to the substrate and promotes higher carrier mobility.

  20. Influence of the charge trap density distribution in a gate insulator on the positive-bias stress instability of amorphous indium-gallium-zinc oxide thin-film transistors

    NASA Astrophysics Data System (ADS)

    Kim, Eungtaek; Kim, Choong-Ki; Lee, Myung Keun; Bang, Tewook; Choi, Yang-Kyu; Park, Sang-Hee Ko; Choi, Kyung Cheol

    2016-05-01

    We investigated the positive-bias stress (PBS) instability of thin film transistors (TFTs) composed of different types of first-gate insulators, which serve as a protection layer of the active surface. Two different deposition methods, i.e., the thermal atomic layer deposition (THALD) and plasma-enhanced ALD (PEALD) of Al2O3, were applied for the deposition of the first GI. When THALD was used to deposit the GI, amorphous indium-gallium-zinc oxide (a-IGZO) TFTs showed superior stability characteristics under PBS. For example, the threshold voltage shift (ΔVth) was 0 V even after a PBS time (tstress) of 3000 s under a gate voltage (VG) condition of 5 V (with an electrical field of 1.25 MV/cm). On the other hand, when the first GI was deposited by PEALD, the ΔVth value of a-IGZO TFTs was 0.82 V after undergoing an identical amount of PBS. In order to interpret the disparate ΔVth values resulting from PBS quantitatively, the average oxide charge trap density (NT) in the GI and its spatial distribution were investigated through low-frequency noise characterizations. A higher NT resulted during in the PEALD type GI than in the THALD case. Specifically, the PEALD process on a-IGZO layer surface led to an increasing trend of NT near the GI/a-IGZO interface compared to bulk GI owing to oxygen plasma damage on the a-IGZO surface.

  1. Multifunctional oxide thin films for magnetoelectric and electromechanical applications

    NASA Astrophysics Data System (ADS)

    Baek, Seung Hyub

    Epitaxial multifunctional oxide thin films have been extensively researched to understand and exploit a variety of their physical properties. In order to integrate such versatile properties into real devices, there are several critical issues: (1) high-quality thin film growth, (2) fundamental understanding on reliable performance, and (3) device fabrication process preserving functionality of oxides. We have investigated all these issues, employing two different materials: multiferroic BiFeO3 and piezoelectric Pb(Mg1/3 Nb2/3)O3-PbTiO3 (PMN-PT) epitaxial thin films. For the high-quality thin film growth, we have chosen both BiFeO 3 and PMN-PT thin films as a model system. Bi2O3and PbO are the volatile species in these oxides, which makes it hard to grow phase-pure stoichiometric thin films. Because the properties of oxides are sensitive to stoichiometry and defects, it is highly required to fix such volatile elements during thin film growth. We have grown high-quality epitaxial thin films using a fast-rate off-axis sputtering method and vicinal substrates. In addition, we were able to control domain structures of BiFeO3 thin films using vicinal substrates. For the study on the reliability issues in oxides, we have used BiFeO 3 thin films within the framework of magnetoelectric device applications. For reliable magnetoelectric performance of BiFeO3, polarization switching path has to be (1) deterministic, and to be retained along with (2) time---retention, and (3) cycles--- fatigue. We have used monodomain BiFeO3 thin films as a model system. Based on theoretical predictions, we have studied polarization switching paths, and achieved both selective polarization switching and retention problems using island BiFeO3 structure. We have also investigated polarization fatigue, dependent on switching path. For the demonstration of working devices preserving the original functionality of oxides, we have fabricated micro-cantilevers using PMN-PT heterostructure on Si. The

  2. Ti-Doped Indium Tin Oxide Thin Films for Transparent Field-Effect Transistors: Control of Charge-Carrier Density and Crystalline Structure

    SciTech Connect

    J Kim; K Ji; M Jang; H Yang; R Choi; J Jeong

    2011-12-31

    Indium tin oxide (ITO) films are representative transparent conducting oxide media for organic light-emitting diodes, liquid crystal displays, and solar cell applications. Extending the utility of ITO films from passive electrodes to active channel layers in transparent field-effect transistors (FETs), however, has been largely limited because of the materials' high carrier density (>1 x 10{sup 20} cm{sup 03}), wide band gap, and polycrystalline structure. Here, we demonstrate that control over the cation composition in ITO-based oxide films via solid doping of titanium (Ti) can optimize the carrier concentration and suppress film crystallization. On 120 nm thick SiO{sub 2}/Mo (200 nm)/glass substrates, transparent n-type FETs prepared with 4 at % Ti-doped ITO films and fabricated via the cosputtering of ITO and TiO{sub 2} exhibited high electron mobilities of 13.4 cm{sup 2} V{sup -1} s{sup -1}, a low subthreshold gate swing of 0.25 V decade{sup -1}, and a high I{sub on}/I{sub off} ratio of >1 x 10{sup 8}.

  3. Hydrogen passivation of electron trap in amorphous In-Ga-Zn-O thin-film transistors

    SciTech Connect

    Hanyu, Yuichiro Domen, Kay; Nomura, Kenji; Hiramatsu, Hidenori; Kamiya, Toshio; Kumomi, Hideya; Hosono, Hideo

    2013-11-11

    We report an experimental evidence that some hydrogens passivate electron traps in an amorphous oxide semiconductor, a-In-Ga-Zn-O (a-IGZO). The a-IGZO thin-film transistors (TFTs) annealed at 300 °C exhibit good operation characteristics; while those annealed at ≥400 °C show deteriorated ones. Thermal desorption spectra (TDS) of H{sub 2}O indicate that this threshold annealing temperature corresponds to depletion of H{sub 2}O desorption from the a-IGZO layer. Hydrogen re-doping by wet oxygen annealing recovers the good TFT characteristic. The hydrogens responsible for this passivation have specific binding energies corresponding to the desorption temperatures of 300–430 °C. A plausible structural model is suggested.

  4. High-performance low-cost back-channel-etch amorphous gallium-indium-zinc oxide thin-film transistors by curing and passivation of the damaged back channel.

    PubMed

    Park, Jae Chul; Ahn, Seung-Eon; Lee, Ho-Nyeon

    2013-12-11

    High-performance, low-cost amorphous gallium-indium-zinc oxide (a-GIZO) thin-film-transistor (TFT) technology is required for the next generation of active-matrix organic light-emitting diodes. A back-channel-etch structure is the most appropriate device structure for high-performance, low-cost a-GIZO TFT technology. However, channel damage due to source/drain etching and passivation-layer deposition has been a critical issue. To solve this problem, the present work focuses on overall back-channel processes, such as back-channel N2O plasma treatment, SiOx passivation deposition, and final thermal annealing. This work has revealed the dependence of a-GIZO TFT characteristics on the N2O plasma radio-frequency (RF) power and frequency, the SiH4 flow rate in the SiOx deposition process, and the final annealing temperature. On the basis of these results, a high-performance a-GIZO TFT with a field-effect mobility of 35.7 cm(2) V(-1) s(-1), a subthreshold swing of 185 mV dec(-1), a switching ratio exceeding 10(7), and a satisfactory reliability was successfully fabricated. The technology developed in this work can be realized using the existing facilities of active-matrix liquid-crystal display industries. PMID:24221957

  5. A study on the high temperature-dependence of the electrical properties in a solution-deposited zinc-tin-oxide thin-film transistor operated in the saturation region

    NASA Astrophysics Data System (ADS)

    Yu, Kyeong Min; Bae, Byung Seong; Jung, Myunghee; Yun, Eui-Jung

    2016-06-01

    We investigate the effects of high temperatures in the range of 292 - 393 K on the electrical properties of solution-processed amorphous zinc-tin-oxide (a-ZTO) thin-film transistors (TFTs) operated in the saturation region. The fabricated a-ZTO TFTs have a non-patterned bottom gate and top contact structure, and they use a heavily-doped Si wafer and SiO2 as a gate electrode and a gate insulator layer, respectively. In a-ZTO TFTs, the trap release energy ( E TR ) was deduced by using Maxwell-Boltzmann statistics. The decreasing E TR toward zero with increasing gate voltage (the density of trap states ( n s )) in the a-ZTO active layer can be attributed to a shift of the Fermi level toward the mobility edge with increasing gate voltage. The TFTs with low gate voltage (low n s ) exhibit multiple trap and release characteristics and show thermally-activated behavior. In TFTs with a high gate voltage (high n s ), however, we observe decreasing mobility and conductivity with increasing temperature at temperatures ranging from 303 to 363 K. This confirms that the E TR can drop to zero, indicating a shift of the Fermi level beyond the mobility edge. Hence, the mobility edge is detected at the cusp between thermally-activated transport and band transport.

  6. Unidirectional oxide hetero-interface thin-film diode

    NASA Astrophysics Data System (ADS)

    Park, Youngmin; Lee, Eungkyu; Lee, Jinwon; Lim, Keon-Hee; Kim, Youn Sang

    2015-10-01

    The unidirectional thin-film diode based on oxide hetero-interface, which is well compatible with conventional thin-film fabrication process, is presented. With the metal anode/electron-transporting oxide (ETO)/electron-injecting oxide (EIO)/metal cathode structure, it exhibits that electrical currents ohmically flow at the ETO/EIO hetero-interfaces for only positive voltages showing current density (J)-rectifying ratio of ˜105 at 5 V. The electrical properties (ex, current levels, and working device yields) of the thin-film diode (TFD) are systematically controlled by changing oxide layer thickness. Moreover, we show that the oxide hetero-interface TFD clearly rectifies an AC input within frequency (f) range of 102 Hz < f < 106 Hz, providing a high feasibility for practical applications.

  7. Unidirectional oxide hetero-interface thin-film diode

    SciTech Connect

    Park, Youngmin; Lee, Eungkyu; Lee, Jinwon; Lim, Keon-Hee; Kim, Youn Sang

    2015-10-05

    The unidirectional thin-film diode based on oxide hetero-interface, which is well compatible with conventional thin-film fabrication process, is presented. With the metal anode/electron-transporting oxide (ETO)/electron-injecting oxide (EIO)/metal cathode structure, it exhibits that electrical currents ohmically flow at the ETO/EIO hetero-interfaces for only positive voltages showing current density (J)-rectifying ratio of ∼10{sup 5} at 5 V. The electrical properties (ex, current levels, and working device yields) of the thin-film diode (TFD) are systematically controlled by changing oxide layer thickness. Moreover, we show that the oxide hetero-interface TFD clearly rectifies an AC input within frequency (f) range of 10{sup 2} Hz < f < 10{sup 6} Hz, providing a high feasibility for practical applications.

  8. Multiferroic oxide thin films and heterostructures

    SciTech Connect

    Lu, Chengliang E-mail: Tao.Wu@kaust.edu.sa; Hu, Weijin; Wu, Tom E-mail: Tao.Wu@kaust.edu.sa; Tian, Yufeng

    2015-06-15

    Multiferroic materials promise a tantalizing perspective of novel applications in next-generation electronic, memory, and energy harvesting technologies, and at the same time they also represent a grand scientific challenge on understanding complex solid state systems with strong correlations between multiple degrees of freedom. In this review, we highlight the opportunities and obstacles in growing multiferroic thin films with chemical and structural integrity and integrating them in functional devices. Besides the magnetoelectric effect, multiferroics exhibit excellent resistant switching and photovoltaic properties, and there are plenty opportunities for them to integrate with other ferromagnetic and superconducting materials. The challenges include, but not limited, defect-related leakage in thin films, weak magnetism, and poor control on interface coupling. Although our focuses are Bi-based perovskites and rare earth manganites, the insights are also applicable to other multiferroic materials. We will also review some examples of multiferroic applications in spintronics, memory, and photovoltaic devices.

  9. Low leakage current gate dielectrics prepared by ion beam assisted deposition for organic thin film transistors

    NASA Astrophysics Data System (ADS)

    Kim, Chang Su; Jo, Sung Jin; Kim, Jong Bok; Ryu, Seung Yoon; Noh, Joo Hyon; Baik, Hong Koo; Lee, Se Jong; Kim, Youn Sang

    2007-12-01

    This communication reports on the fabrication of low operating voltage pentacene thin-film transistors with high-k gate dielectrics by ion beam assisted deposition (IBAD). These densely packed dielectric layers by IBAD show a much lower level of leakage current than those created by e-beam evaporation. These results, from the fact that those thin films deposited with low adatom mobility, have an open structure, consisting of spherical grains with pores in between, that acts as a significant path for leakage current. By contrast, our results demonstrate the potential to limit this leakage. The field effect mobility, on/off current ratio, and subthreshold slope obtained from pentacene thin-film transistors (TFTs) were 1.14 cm2/V s, 105, and 0.41 V/dec, respectively. Thus, the high-k gate dielectrics obtained by IBAD show promise in realizing low leakage current, low voltage, and high mobility pentacene TFTs.

  10. NEXAFS Study of Air Oxidation for Mg Nanoparticle Thin Film

    NASA Astrophysics Data System (ADS)

    Ogawa, S.; Murakami, S.; Shirai, K.; Nakanishi, K.; Ohta, T.; Yagi, S.

    2013-03-01

    The air oxidation reaction of Mg nanoparticle thin film has been investigated by Mg K-edge NEXAFS technique. It is revealed that MgO is formed on the Mg nanoparticle surfaces at the early stage of the air oxidation for Mg nanoparticle thin film. The simulation of NEXAFS spectrum using standard spectra indicates the existence of complex magnesium carbonates (x(MgCO3).yMg(OH2).z(H2O)) in addition to MgO at the early stage of the air oxidation.

  11. High-performance carbon nanotube thin-film transistors on flexible paper substrates

    SciTech Connect

    Liu, Na; Yun, Ki Nam; Yu, Hyun-Yong; Lee, Cheol Jin; Shim, Joon Hyung

    2015-03-09

    Single-walled carbon nanotubes (SWCNTs) are promising materials as active channels for flexible transistors owing to their excellent electrical and mechanical properties. However, flexible SWCNT transistors have never been realized on paper substrates, which are widely used, inexpensive, and recyclable. In this study, we fabricated SWCNT thin-film transistors on photo paper substrates. The devices exhibited a high on/off current ratio of more than 10{sup 6} and a field-effect mobility of approximately 3 cm{sup 2}/V·s. The proof-of-concept demonstration indicates that SWCNT transistors on flexible paper substrates could be applied as low-cost and recyclable flexible electronics.

  12. Characteristics of a Field-Effect Transistor Fabricated with Electropolymerized Thin Film

    NASA Astrophysics Data System (ADS)

    Oyama, Noboru; Yoshimura, Fumihiro; Ohsaka, Takeo; Koezuka, Hiroshi; Ando, Torahiko

    1988-03-01

    The preparation and characteristics of the solid-state field-effect transistor (FET) based on poly(p,p'-biphenol)(PBP) thin film prepared by electropolymerization of p,p'-biphenol are presented. The PBP-based FET displayed excellent drain current (ID)-drain voltage (VD) characteristics for various gate voltages. The ID-VD characteristics were analyzed as in a conventional MOS transistor.

  13. Altering properties of cerium oxide thin films by Rh doping

    SciTech Connect

    Ševčíková, Klára; Nehasil, Václav; Vorokhta, Mykhailo; Haviar, Stanislav; Matolín, Vladimír; and others

    2015-07-15

    Highlights: • Thin films of ceria doped by rhodium deposited by RF magnetron sputtering. • Concentration of rhodium has great impact on properties of Rh–CeO{sub x} thin films. • Intensive oxygen migration in films with low concentration of rhodium. • Oxygen migration suppressed in films with high amount of Rh dopants. - Abstract: Ceria containing highly dispersed ions of rhodium is a promising material for catalytic applications. The Rh–CeO{sub x} thin films with different concentrations of rhodium were deposited by RF magnetron sputtering and were studied by soft and hard X-ray photoelectron spectroscopies, Temperature programmed reaction and X-ray powder diffraction techniques. The sputtered films consist of rhodium–cerium mixed oxide where cerium exhibits a mixed valency of Ce{sup 4+} and Ce{sup 3+} and rhodium occurs in two oxidation states, Rh{sup 3+} and Rh{sup n+}. We show that the concentration of rhodium has a great influence on the chemical composition, structure and reducibility of the Rh–CeO{sub x} thin films. The films with low concentrations of rhodium are polycrystalline, while the films with higher amount of Rh dopants are amorphous. The morphology of the films strongly influences the mobility of oxygen in the material. Therefore, varying the concentration of rhodium in Rh–CeO{sub x} thin films leads to preparing materials with different properties.

  14. Growth of Epitaxial Oxide Thin Films on Graphene.

    PubMed

    Zou, Bin; Walker, Clementine; Wang, Kai; Tileli, Vasiliki; Shaforost, Olena; Harrison, Nicholas M; Klein, Norbert; Alford, Neil M; Petrov, Peter K

    2016-01-01

    The transfer process of graphene onto the surface of oxide substrates is well known. However, for many devices, we require high quality oxide thin films on the surface of graphene. This step is not understood. It is not clear why the oxide should adopt the epitaxy of the underlying oxide layer when it is deposited on graphene where there is no lattice match. To date there has been no explanation or suggestion of mechanisms which clarify this step. Here we show a mechanism, supported by first principles simulation and structural characterisation results, for the growth of oxide thin films on graphene. We describe the growth of epitaxial SrTiO3 (STO) thin films on a graphene and show that local defects in the graphene layer (e.g. grain boundaries) act as bridge-pillar spots that enable the epitaxial growth of STO thin films on the surface of the graphene layer. This study, and in particular the suggestion of a mechanism for epitaxial growth of oxides on graphene, offers new directions to exploit the development of oxide/graphene multilayer structures and devices. PMID:27515496

  15. Growth of Epitaxial Oxide Thin Films on Graphene

    PubMed Central

    Zou, Bin; Walker, Clementine; Wang, Kai; Tileli, Vasiliki; Shaforost, Olena; Harrison, Nicholas M.; Klein, Norbert; Alford, Neil M.; Petrov, Peter K.

    2016-01-01

    The transfer process of graphene onto the surface of oxide substrates is well known. However, for many devices, we require high quality oxide thin films on the surface of graphene. This step is not understood. It is not clear why the oxide should adopt the epitaxy of the underlying oxide layer when it is deposited on graphene where there is no lattice match. To date there has been no explanation or suggestion of mechanisms which clarify this step. Here we show a mechanism, supported by first principles simulation and structural characterisation results, for the growth of oxide thin films on graphene. We describe the growth of epitaxial SrTiO3 (STO) thin films on a graphene and show that local defects in the graphene layer (e.g. grain boundaries) act as bridge-pillar spots that enable the epitaxial growth of STO thin films on the surface of the graphene layer. This study, and in particular the suggestion of a mechanism for epitaxial growth of oxides on graphene, offers new directions to exploit the development of oxide/graphene multilayer structures and devices. PMID:27515496

  16. Channel layer thickness dependence of In-Ti-Zn-O thin-film transistors fabricated using pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Zhang, Q.; Shan, F. K.; Liu, G. X.; Liu, A.; Lee, W. J.; Shin, B. C.

    2014-05-01

    Amorphous indium-titanium-zinc-oxide (ITZO) thin-film transistors (TFTs) with various channel thicknesses were fabricated at room temperature by using pulsed laser deposition. The channel layer thickness (CLT) dependence of the TFTs was investigated. All the ITZO thin films were amorphous, and the surface roughnesses decreased slightly first and then increased with increasing CLT. With increasing CLT from 35 to 140 nm, the on/off current ratio and the field-effect mobility increased, and the subthreshold swing decreased. The TFT with a CLT of 210 nm exhibited the worst performance, while the ITZO TFT with a CLT of 140 nm exhibited the best performance with a subthreshold voltage of 2.86 V, a mobility of 53.9 cm2V-1s-1, a subthreshold swing of 0.29 V/decade and an on/off current ratio of 109.

  17. A new drain current model for amorphous IGZO thin film transistors

    NASA Astrophysics Data System (ADS)

    Qiang, Lei; Yao, Ruo-He

    2015-04-01

    Based on the conduction mechanisms of amorphous InGaZnO (a-IGZO) thin film transistors, generalized equations are derived which permit the determination of drain current characteristics. A geometry-independent definition for field effect mobility considering the ratio of free-to-trapped carriers is introduced, which conveys the properties of the active semiconducting layer. It is suggested that a drain current model that includes different charge transports gives a consistent and accurate description of the electrical behavior. The good agreement between measured and calculated results confirms the efficiency of this model for the design of integrated large-area thin-film circuits.

  18. An asymmetric oligomer based on thienoacene for solution processed crystal organic thin-film transistors.

    PubMed

    Tian, Hongkun; Han, Yang; Bao, Cheng; Yan, Donghang; Geng, Yanhou; Wang, Fosong

    2012-04-11

    A novel thienoacene-based conjugated oligomer, i.e.BTTT-T-C12, was designed and synthesized. Its highly asymmetric structural feature enables the preparation of two-dimensional single-crystalline thin films in millimetre size and ~100 nm thick by a solution processing method directly on the Si/SiO(2) substrate. Single crystal organic thin film transistors exhibit a mobility of 0.70 cm(2) V(-1) s(-1) and an on/off ratio of 5.7 × 10(4). PMID:22389169

  19. Electrical properties of solution-deposited ZnO thin-film transistors by low-temperature annealing.

    PubMed

    Lim, Chul; Oh, Ji Young; Koo, Jae Bon; Park, Chan Woo; Jung, Soon-Won; Na, Bock Soon; Chu, Hye Yong

    2014-11-01

    Flexible oxide thin-film transistors (Oxide-TFTs) have emerged as next generation transistors because of their applicability in electronic device. In particular, the major driving force behind solution-processed zinc oxide film research is its prospective use in printing for electronics. A low-temperature process to improve the performance of solution-processed n-channel ZnO thin-film transistors (TFTs) fabricated via spin-coating and inkjet-printing is introduced here. ZnO nanoparticles were synthesized using a facile sonochemical method that was slightly modified based on a previously reported method. The influence of the annealing atmosphere on both nanoparticle-based TFT devices fabricated via spin-coating and those created via inkjet printing was investigated. For the inkjet-printed TFTs, the characteristics were improved significantly at an annealing temperature of 150 degrees C. The field effect mobility, V(th), and the on/off current ratios were 3.03 cm2/Vs, -3.3 V, and 10(4), respectively. These results indicate that annealing at 150 degrees C 1 h is sufficient to obtain a mobility (μ(sat)) as high as 3.03 cm2/Vs. Also, the active layer of the solution-based ZnO nanoparticles allowed the production of high-performance TFTs for low-cost, large-area electronics and flexible devices. PMID:25958581

  20. Compositional tuning of atomic layer deposited MgZnO for thin film transistors

    SciTech Connect

    Wrench, J. S.; Brunell, I. F.; Chalker, P. R.; Jin, J. D.; Shaw, A.; Mitrovic, I. Z.; Hall, S.

    2014-11-17

    Thin film transistors (TFTs) have been fabricated using magnesium zinc oxide (MgZnO) layers deposited by atomic layer deposition at 200 °C. The composition of the MgZnO is systematically modified by varying the ratio of MgO and ZnO deposition cycles. A blue-shift of the near band-edge photoluminescence after post-deposition annealing at 300 °C indicates significant activation of the Mg dopant. A 7:1 ratio of ZnO:MgO deposition cycles was used to fabricate a device with a TFT channel width of 2000 μm and a channel length of 60 μm. This transistor yielded an effective saturation mobility of 4 cm{sup 2}/V s and a threshold voltage of 7.1 V, respectively. The on/off ratio was 1.6×10{sup 6} and the maximum interface state density at the ZnO/SiO{sub 2} interface is ∼6.5×10{sup 12} cm{sup −2}.

  1. Electrical properties of vanadium tungsten oxide thin films

    SciTech Connect

    Nam, Sung-Pill; Noh, Hyun-Ji; Lee, Sung-Gap; Lee, Young-Hie

    2010-03-15

    The vanadium tungsten oxide thin films deposited on Pt/Ti/SiO{sub 2}/Si substrates by RF sputtering exhibited good TCR and dielectric properties. The dependence of crystallization and electrical properties are related to the grain size of V{sub 1.85}W{sub 0.15}O{sub 5} thin films with different annealing temperatures. It was found that the dielectric properties and TCR properties of V{sub 1.85}W{sub 0.15}O{sub 5} thin films were strongly dependent upon the annealing temperature. The dielectric constants of the V{sub 1.85}W{sub 0.15}O{sub 5} thin films annealed at 400 {sup o}C were 44, with a dielectric loss of 0.83%. The TCR values of the V{sub 1.85}W{sub 0.15}O{sub 5} thin films annealed at 400 {sup o}C were about -3.45%/K.

  2. Highly Conducting Transparent Indium-Doped Zinc Oxide Thin Films

    NASA Astrophysics Data System (ADS)

    Singh, Budhi; Ghosh, Subhasis

    2014-09-01

    Highly conducting transparent indium-doped zinc oxide (IZO) thin films have been achieved by controlling different growth parameters using radio frequency magnetron sputtering. The structural, electrical, and optical properties of the IZO thin films have been investigated for varied indium content and growth temperature ( T G) in order to find out the optimum level of doping to achieve the highest conducting transparent IZO thin films. The highest mobility and carrier concentration of 11.5 cm2/V-s and 3.26 × 1020 cm-3, respectively, have been achieved in IZO doped with 2% indium. It has been shown that as T G of the 2% IZO thin films increase, more and more indium atoms are substituted into Zn sites leading to shift in (002) peaks towards higher angles which correspond to releasing the stress within the IZO thin film. The minimum resistivity of 5.3 × 10-4 Ω-cm has been achieved in 2% indium-doped IZO grown at 700°C.

  3. High mobility amorphous zinc oxynitride semiconductor material for thin film transistors

    SciTech Connect

    Ye Yan; Lim, Rodney; White, John M.

    2009-10-01

    Zinc oxynitride semiconductor material is produced through a reactive sputtering process in which competition between reactions responsible for the growth of hexagonal zinc oxide (ZnO) and for the growth of cubic zinc nitride (Zn{sub 3}N{sub 2}) is promoted. In contrast to processes in which the reaction for either the oxide or the nitride is dominant, the multireaction process yields a substantially amorphous or a highly disordered nanocrystalline film with higher Hall mobility, 47 cm{sup 2} V{sup -1} s{sup -1} for the as-deposited film produced at 50 deg. C and 110 cm{sup 2} V{sup -1} s{sup -1} after annealing at 400 deg. C. In addition, it has been observed that the Hall mobility of the material increases as the carrier concentration decreases in a carrier concentration range where a multicomponent metal oxide semiconductor, indium-gallium-zinc oxide, follows the opposite trend. This indicates that the carrier transports in the single-metal compound and the multimetal compound are probably dominated by different mechanisms. Film stability and thin film transistor performance of the material have also been tested, and results are presented herein.

  4. High-mobility ambipolar ZnO-graphene hybrid thin film transistors

    PubMed Central

    Song, Wooseok; Kwon, Soon Yeol; Myung, Sung; Jung, Min Wook; Kim, Seong Jun; Min, Bok Ki; Kang, Min-A; Kim, Sung Ho; Lim, Jongsun; An, Ki-Seok

    2014-01-01

    In order to combine advantages of ZnO thin film transistors (TFTs) with a high on-off ratio and graphene TFTs with extremely high carrier mobility, we present a facile methodology for fabricating ZnO thin film/graphene hybrid two-dimensional TFTs. Hybrid TFTs exhibited ambipolar behavior, an outstanding electron mobility of 329.7 ± 16.9 cm2/V·s, and a high on-off ratio of 105. The ambipolar behavior of the ZnO/graphene hybrid TFT with high electron mobility could be due to the superimposed density of states involving the donor states in the bandgap of ZnO thin films and the linear dispersion of monolayer graphene. We further established an applicable circuit model for understanding the improvement in carrier mobility of ZnO/graphene hybrid TFTs. PMID:24513629

  5. Electrical Transport in Nanoscale Complex Oxide Thin Films: Strontium titanate and RNiO3

    NASA Astrophysics Data System (ADS)

    Son, Junwoo

    Complex oxide thin films have attracted significant attention due to a wealth of physical phenomena, such as ferroelectricity and Mott transitions arising from strong interactions in d-bands. Moreover, the physical phenomena observed in these materials exhibit sensitivities, which are not found in conventional semiconductors and give rise to abrupt changes in their physical properties. The richness of electronic phases and unique functionalities of complex oxides are attractive for applications in next-generation electronic devices. To realize new electronic devices with complex oxides, it is essential to understand the mechanisms of the electrical transport and to control the transport properties of complex oxide thin films. In this dissertation, electrical transport phenomena and their electrical control are experimentally studied in two different complex oxide thin film systems, exhibiting resistive switching and Mott metal-insulator transitions. The first part will briefly discuss resistive switching in ultrathin SrTiO3 tunnel junctions in metal-insulator-metal (MIM) geometry. The current-voltage characteristics provide hints of the origin of the resistive switching phenomena in SrTiO3 tunnel barriers, which are also relevant for resistive switching in thicker films. The second part focuses on the control of metal-insulator transitions in RNiO3, where R = trivalent rare earth ion, using different strategies: band-width control and band-filling control. The electrical transport in low-dimensional, strongly correlated LaNiO3 is explored in terms of band-width control by strain and dimensionality. A new concept of band-filling control in nanoscale NdNiO3 thin films by modulation doping is discussed, and the experimental charge injection from high-quality La-doped SrTiO3 into NdNiO3 thin films is experimentally studied. The potential and limitations of a Modulation-doped Mott Field Effect Transistor (MM-FET) for future "Mott" electronic devices is discussed.

  6. Low-Voltage InGaZnO Thin Film Transistors with Small Sub-Threshold Swing.

    PubMed

    Cheng, C H; Chou, K I; Hsu, H H

    2015-02-01

    We demonstrate a low-voltage driven, indium-gallium-zinc oxide thin-film transistor using high-κ LaAlO3 gate dielectric. A low VT of 0.42 V, very small sub-threshold swing of 68 mV/dec, field-effect mobility of 4.1 cm2/Ns and low operation voltage of 1.4 V were reached simultaneously in LaAlO3/IGZO TFT device. This low-power and small SS TFT has the potential for fast switching speed and low power applications. PMID:26353677

  7. High performance p-type NiOx thin-film transistor by Sn doping

    NASA Astrophysics Data System (ADS)

    Lin, Tengda; Li, Xiuling; Jang, Jin

    2016-06-01

    Major obstacles towards power efficient complementary electronics employing oxide thin-film transistors (TFTs) lie in the lack of equivalent well performing p-channel devices. Here, we report a significant performance enhancement of solution-processed p-type nickel oxide (NiOx) TFTs by introducing Sn dopant. The Sn-doped NiOx (Sn-NiOx) TFTs annealed at 280 °C demonstrate substantially improved electrical performances with the increase in the on/off current ratio (Ion/Ioff) by ˜100 times, field-effect mobility (μlin) by ˜3 times, and the decrease in subthreshold swing by half, comparing with those of pristine NiOx TFTs. X-ray photoelectron spectroscopy and X-ray diffraction results confirm that Sn atoms tend to substitute Ni sites and induce more amorphous phase. A decrease in density of states in the gap of NiOx by Sn doping and the shift of Fermi level (EF) into the midgap lead to the improvements of TFT performances. As a result, Sn-NiOx can be a promising material for the next-generation, oxide-based electronics.

  8. Conductance simulation in an a-Si:H thin-film transistor with Schottky barriers

    SciTech Connect

    Vishnyakov, A. V. Efremov, M. D.

    2010-09-15

    It is shown by numerical simulation that the drain-source Schottky contacts substantially control the conductance of a thin-film transistor in the above-barrier region. At a barrier height in excess of 0.75 eV, the effect of crowding manifests itself; this effect is caused by an increase in electric field at the edge of the source electrode as the pulling voltage is increased, which brings about a local lowering of the barrier and an increase in the current through the reverse-biased Schottky barrier. The effective mobility in the thin-film transistor is controlled by the film and is independent of the barrier height.

  9. Fabrication and Characteristics of High Mobility InSnZnO Thin Film Transistors.

    PubMed

    Choi, Pyungho; Lee, Junki; Park, Hyoungsun; Baek, Dohyun; Lee, Jaehyeong; Yi, Junsin; Kim, Sangsoo; Choi, Byoungdeog

    2016-05-01

    In this paper, we describe the fabrication of thin film transistors (TFTs) with amorphous indium-tin-zinc-oxide (ITZO) as the active material. A transparent ITZO channel layer was formed under an optimized oxygen partial pressure (OPP (%) = O2/(Ar + O2)) and subsequent annealing process. The electrical properties exhibited by this device include field-effect mobility (μ(eff)), sub-threshold swing (SS), and on/off current ratio (I(ON/OFF)) values of 28.97 cm2/V x s, 0.2 V/decade, and 2.64 x 10(7), respectively. The average transmittance values for each OPP condition in the visible range were greater than 80%. The positive gate bias stress resulted in a positive threshold voltage (V(th)) shift in the transfer curves and degraded the parameters μ(eff) and SS. These phenomena originated from electron trapping from the ITZO channel layer into the oxide/ITZO interface trap sites. PMID:27483823

  10. Photosensor application of amorphous InZnO-based thin film transistor

    NASA Astrophysics Data System (ADS)

    Liu, Po-Tsun; Chou, Yi-Teh; Teng, Li-Feng

    2010-03-01

    Thin film transistor (TFT) device structure with transparent conductive oxide semiconductor is proposed for the photosensor application. The adoption of TFT-based photosensor device also is promising to be integrated with pixel-array circuits in a flat panel display and realize the system-on-panel (SoP) concept. The photosensitive TFT device can be applied to sense the ambient light brightness and then give the feedback to the backlight system adjusting the backlight intensity for the power-saving green displays. In this work, we studied the photosensitivity of amorphous indium zinc oxide (a-IZO) TFT to ultraviolet light. The a-IZO-based semiconductors have been paid much attention due to their uniform amorphous phase and high field-effect carrier mobility characteristics. The obvious threshold voltage shift was observed after light illumination, and exhibited slow recovery while returning to initial status after removing the light source. This mechanism for the photoreaction is well explained by the dynamic equilibrium of charge exchange reaction between O2(g) and O2- in the backchannel region of IZO-based films. An electrical trigger using charge pumping method is used to confirm the proposed mechanism and accelerate photoreaction recoverability for the first time. Using knowledge of photoreaction behavior, an operation scheme of photosensing elements consist of a-IZO TFTs is also demonstrated in this paper.

  11. Enhanced photocurrent of Ge-doped InGaO thin film transistors with quantum dots

    SciTech Connect

    Lee, Sang Moo; Park, Si Jin; Kang, Seong Jun; Lee, Kwang Ho; Park, Jin-Seong; Park, Soohyung; Yi, Yeonjin

    2015-01-19

    The photocurrent of germanium-doped indium-gallium oxide (GIGO) thin film transistors (TFTs) can be observed when the device is exposed to a ultra-violet light because GIGO is a wide band gap semiconducting material. Therefore, we decorated cadmium selenide (CdSe) quantum-dots (QDs) on the surface of GIGO to increase the photocurrent for low-energy light, i.e., visible light. A 10 nm GIGO film was deposited on the SiO{sub 2}/Si substrate by a radio frequency sputter system. Also, we prepared CdSe QDs with sizes of ∼6.3 nm, which can absorb red visible light. QDs were spin-coated onto the GIGO film, and post-annealing was done to provide cross-linking between QDs. The prepared devices showed a 231% increase in photocurrent when exposed to 650 nm light due to the QDs on the GIGO surface. Measurements to construct an energy level diagram were made using ultraviolet photoelectron spectroscopy to determine the origin of the photocurrent, and we found that the small band gap of CdSe QDs enables the increase in photocurrent in the GIGO TFTs. This result is relevant for developing highly transparent photosensors based on oxide semiconductors and QDs.

  12. Design of step composition gradient thin film transistor channel layers grown by atomic layer deposition

    SciTech Connect

    Ahn, Cheol Hyoun; Hee Kim, So; Gu Yun, Myeong; Koun Cho, Hyung

    2014-12-01

    In this study, we proposed the artificially designed channel structure in oxide thin-film transistors (TFTs) called a “step-composition gradient channel.” We demonstrated Al step-composition gradient Al-Zn-O (AZO) channel structures consisting of three AZO layers with different Al contents. The effects of stacking sequence in the step-composition gradient channel on performance and electrical stability of bottom-gate TFT devices were investigated with two channels of inverse stacking order (ascending/descending step-composition). The TFT with ascending step-composition channel structure (5 → 10 → 14 at. % Al composition) showed relatively negative threshold voltage (−3.7 V) and good instability characteristics with a reduced threshold voltage shift (Δ 1.4 V), which was related to the alignment of the conduction band off-set within the channel layer depending on the Al contents. Finally, the reduced Al composition in the initial layer of ascending step-composition channel resulted in the best field effect mobility of 4.5 cm{sup 2}/V s. We presented a unique active layer of the “step-composition gradient channel” in the oxide TFTs and explained the mechanism of adequate channel design.

  13. All diamond self-aligned thin film transistor

    DOEpatents

    Gerbi, Jennifer

    2008-07-01

    A substantially all diamond transistor with an electrically insulating substrate, an electrically conductive diamond layer on the substrate, and a source and a drain contact on the electrically conductive diamond layer. An electrically insulating diamond layer is in contact with the electrically conductive diamond layer, and a gate contact is on the electrically insulating diamond layer. The diamond layers may be homoepitaxial, polycrystalline, nanocrystalline or ultrananocrystalline in various combinations.A method of making a substantially all diamond self-aligned gate transistor is disclosed in which seeding and patterning can be avoided or minimized, if desired.

  14. Nitrogen doped zinc oxide thin film

    SciTech Connect

    Li, Sonny X.

    2003-12-15

    To summarize, polycrystalline ZnO thin films were grown by reactive sputtering. Nitrogen was introduced into the films by reactive sputtering in an NO{sub 2} plasma or by N{sup +} implantation. All ZnO films grown show n-type conductivity. In unintentionally doped ZnO films, the n-type conductivities are attributed to Zn{sub i}, a native shallow donor. In NO{sub 2}-grown ZnO films, the n-type conductivity is attributed to (N{sub 2}){sub O}, a shallow double donor. In NO{sub 2}-grown ZnO films, 0.3 atomic % nitrogen was found to exist in the form of N{sub 2}O and N{sub 2}. Upon annealing, N{sub 2}O decomposes into N{sub 2} and O{sub 2}. In furnace-annealed samples N{sub 2} redistributes diffusively and forms gaseous N{sub 2} bubbles in the films. Unintentionally doped ZnO films were grown at different oxygen partial pressures. Zni was found to form even at oxygen-rich condition and led to n-type conductivity. N{sup +} implantation into unintentionally doped ZnO film deteriorates the crystallinity and optical properties and leads to higher electron concentration. The free electrons in the implanted films are attributed to the defects introduced by implantation and formation of (N{sub 2}){sub O} and Zni. Although today there is still no reliable means to produce good quality, stable p-type ZnO material, ZnO remains an attractive material with potential for high performance short wavelength optoelectronic devices. One may argue that gallium nitride was in a similar situation a decade ago. Although we did not obtain any p-type conductivity, we hope our research will provide a valuable reference to the literature.

  15. Thin film transistors on plastic substrates with reflective coatings for radiation protection

    DOEpatents

    Wolfe, Jesse D.; Theiss, Steven D.; Carey, Paul G.; Smith, Patrick M.; Wickbold, Paul

    2006-09-26

    Fabrication of silicon thin film transistors (TFT) on low-temperature plastic substrates using a reflective coating so that inexpensive plastic substrates may be used in place of standard glass, quartz, and silicon wafer-based substrates. The TFT can be used in large area low cost electronics, such as flat panel displays and portable electronics such as video cameras, personal digital assistants, and cell phones.

  16. Thin film transistors on plastic substrates with reflective coatings for radiation protection

    DOEpatents

    Wolfe, Jesse D.; Theiss, Steven D.; Carey, Paul G.; Smith, Patrick M.; Wickboldt, Paul

    2003-11-04

    Fabrication of silicon thin film transistors (TFT) on low-temperature plastic substrates using a reflective coating so that inexpensive plastic substrates may be used in place of standard glass, quartz, and silicon wafer-based substrates. The TFT can be used in large area low cost electronics, such as flat panel displays and portable electronics such as video cameras, personal digital assistants, and cell phones.

  17. Carbon nanotube network thin-film transistors on flexible/stretchable substrates

    DOEpatents

    Takei, Kuniharu; Takahashi, Toshitake; Javey, Ali

    2016-03-29

    This disclosure provides systems, methods, and apparatus for flexible thin-film transistors. In one aspect, a device includes a polymer substrate, a gate electrode disposed on the polymer substrate, a dielectric layer disposed on the gate electrode and on exposed portions of the polymer substrate, a carbon nanotube network disposed on the dielectric layer, and a source electrode and a drain electrode disposed on the carbon nanotube network.

  18. High temperature coefficient of resistance molybdenum oxide and nickel oxide thin films for microbolometer applications

    NASA Astrophysics Data System (ADS)

    Jin, Yao O.; John, David Saint; Podraza, Nikolas J.; Jackson, Thomas N.; Horn, Mark W.

    2015-03-01

    Molybdenum oxide (MoOx) and nickel oxide (NiOx) thin films were deposited by reactive biased target ion beam deposition. MoOx thin film resistivity varied from 3 to 2000 Ω.cm with a temperature coefficient of resistance (TCR) from -1.7% to -3.2%/K, and NiOx thin film resistivity varied from 1 to 300 Ω.cm with a TCR from -2.2% to -3.3%/K, both easily controlled by varying the oxygen partial pressure. Biased target ion beam deposited high TCR MoOx and NiOx thin films are polycrystalline semiconductors and have good stability in air. Compared with commonly used vanadium oxide thin films, MoOx or NiOx thin films offer improved process control for resistive temperature sensors.

  19. Method of fabrication of display pixels driven by silicon thin film transistors

    DOEpatents

    Carey, Paul G.; Smith, Patrick M.

    1999-01-01

    Display pixels driven by silicon thin film transistors are fabricated on plastic substrates for use in active matrix displays, such as flat panel displays. The process for forming the pixels involves a prior method for forming individual silicon thin film transistors on low-temperature plastic substrates. Low-temperature substrates are generally considered as being incapable of withstanding sustained processing temperatures greater than about 200.degree. C. The pixel formation process results in a complete pixel and active matrix pixel array. A pixel (or picture element) in an active matrix display consists of a silicon thin film transistor (TFT) and a large electrode, which may control a liquid crystal light valve, an emissive material (such as a light emitting diode or LED), or some other light emitting or attenuating material. The pixels can be connected in arrays wherein rows of pixels contain common gate electrodes and columns of pixels contain common drain electrodes. The source electrode of each pixel TFT is connected to its pixel electrode, and is electrically isolated from every other circuit element in the pixel array.

  20. Low reflectance sputtered vanadium oxide thin films on silicon

    NASA Astrophysics Data System (ADS)

    Esther, A. Carmel Mary; Dey, Arjun; Rangappa, Dinesh; Sharma, Anand Kumar

    2016-07-01

    Vanadium oxide thin films on silicon (Si) substrate are grown by pulsed radio frequency (RF) magnetron sputtering technique at RF power in the range of 100-700 W at room temperature. Deposited thin films are characterized by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) techniques to investigate microstructural, phase, electronic structure and oxide state characteristics. The reflectance and transmittance spectra of the films and the Si substrate are recorded at the solar region (200-2300 nm) of the spectral window. Substantial reduction in reflectance and increase in transmittance is observed for the films grown beyond 200 W. Further, optical constants viz. absorption coefficient, refractive index and extinction coefficient of the deposited vanadium oxide films are evaluated.

  1. Effect of the gate metal work function on water-gated ZnO thin-film transistor performance

    NASA Astrophysics Data System (ADS)

    Singh, Mandeep; Yusuf Mulla, Mohammad; Vittoria Santacroce, Maria; Magliulo, Maria; Di Franco, Cinzia; Manoli, Kyriaki; Altamura, Davide; Giannini, Cinzia; Cioffi, Nicola; Palazzo, Gerardo; Scamarcio, Gaetano; Torsi, Luisa

    2016-07-01

    ZnO thin films, prepared using a printing-compatible sol–gel method involving a thermal treatment below 400 °C, are proposed as active layers in water-gated thin-film transistors (WG-TFTs). The thin-film structure and surface morphology reveal the presence of contiguous ZnO crystalline (hexagonal wurtzite) with isotropic nano-grains as large as 10 nm characterized by a preferential orientation along the a-axis. The TFT devices are gated through a droplet of deionized water by means of electrodes characterized by different work functions. The high capacitance of the electrolyte allowed operation below 0.5 V. While the Ni, Pd, Au and Pt gate electrodes are electrochemically stable in the inspected potential range, electrochemical activity is revealed for the W one. Such an occurrence leads to an increase of capacitance (and current), which is ascribed to a high output current from the dissolution of a lower capacitance W-oxide layer. The environmental stability of the ZnO WG-TFTs is quite good over a period of five months.

  2. Study of Ferromagnetic and Field Effect Properties of Zinc Oxide Thin Films

    NASA Astrophysics Data System (ADS)

    Xia, Daxue

    Spintronics (spin transport electronics), in which both spm and charge of carriers are utilized for information processing, is perceived to be a candidate to extend and possibly to become the next-generation electronics. Its advantages include nonvolatility (data retention without electrical power), lower energy consumption, faster processing speed, and higher integration densities in comparison with the current semiconductor devices relying solely on electron charge. To realize a spin-field effect transistor, two respects are prerequisite. On the one hand, the mechanism of ferromagnetism should be addressed before one could prepare magnetic semiconductor films in a controllable way. On the other hand, excellent field effect properties should be sought through a convenient and low-cost strategy for manufacturing future nano-scale spintronic devices. This thesis is comprised of two parts. Firstly, it deals with the synthesis, characterization, and magnetism of transition-metal-doped or un-doped zinc oxide (ZnO) thin films. Secondly, it focuses on the field effect properties of solution processable ZnO thin films, which are not only of great interest for current charge-carrier based thin film transistors, but also of fundamental importance in future spin-based transistors. A facile spin-coating technique has been developed to fabricate ZnO thin films. Even without magnetic element doping, the film is found to show room temperature ferromagnetism. A broad series of advanced microscopic and spectroscopic techniques are utilized to characterize the thin films properties. Oxygen vacancy defects are tentatively attributed to the observed ferromagnetism. Following the similar method, Ga doped or Ga, Co co-doped ZnO thin films are prepared. The ferromagnetism is enhanced with Ga doping, providing more carriers. It is discovered that room temperature ferromagnetism can exist in both highly conductive regime and the less conductive or near insulating regime. Transition metal

  3. Impact of thermal oxygen annealing on the properties of tin oxide films and characteristics of p-type thin-film transistors

    NASA Astrophysics Data System (ADS)

    Zhong, Chia-Wen; Lin, Horng-Chih; Liu, Kou-Chen; Huang, Tiao-Yuan

    2016-01-01

    In this work, we study the properties of tin oxide films, which were annealed in oxygen ambient for various periods. The as-deposited tin oxides are tin-dominant and, from the Hall measurements, they are of the n-type with high electron concentrations (>1019 cm-3) and would change to the p-type when the oxygen annealing is sufficiently long. We have also found that changes in the structure and crystallinity of the channel layer can be clearly observed by X-ray diffraction analysis and optical microscopy. On the basis of the observations, a physical scheme is proposed to describe the evolution of the electrical performance of oxygen-annealed devices. A hole mobility of 3.24 cm2 V-1 s-1, a subthreshold swing of 0.43 V/dec, a threshold voltage of 1.4 V, and an on/off current ratio larger than 103 are obtained as the channel is transformed into SnO.

  4. Pulse Thermal Processing for Low Thermal Budget Integration of IGZO Thin Film Transistors

    DOE PAGESBeta

    Noh, Joo Hyon; Joshi, Pooran C.; Kuruganti, Teja; Rack, Philip D.

    2014-11-26

    Pulse thermal processing (PTP) has been explored for low thermal budget integration of indium gallium zinc oxide (IGZO) thin film transistors (TFTs). The IGZO TFTs are exposed to a broadband (0.2-1.4 m) arc lamp radiation spectrum with 100 pulses of 1 msec pulse width. The impact of radiant exposure power on the TFT performance was analyzed in terms of the switching characteristics and bias stress reliability characteristics, respectively. The PTP treated IGZO TFTs with power density of 3.95 kW/cm2 and 0.1 sec total irradiation time showed comparable switching properties, at significantly lower thermal budget, to furnace annealed IGZO TFT. Themore » typical field effect mobility FE, threshold voltage VT, and sub-threshold gate swing S.S were calculated to be 7.8 cm2/ V s, 8.1 V, and 0.22 V/ decade, respectively. The observed performance shows promise for low thermal budget TFT integration on flexible substrates exploiting the large-area, scalable PTP technology.« less

  5. Wireless thin film transistor based on micro magnetic induction coupling antenna

    NASA Astrophysics Data System (ADS)

    Jun, Byoung Ok; Lee, Gwang Jun; Kang, Jong Gu; Kim, Seunguk; Choi, Ji-Woong; Cha, Seung Nam; Sohn, Jung Inn; Jang, Jae Eun

    2015-12-01

    A wireless thin film transistor (TFT) structure in which a source/drain or a gate is connected directly to a micro antenna to receive or transmit signals or power can be an important building block, acting as an electrical switch, a rectifier or an amplifier, for various electronics as well as microelectronics, since it allows simple connection with other devices, unlike conventional wire connections. An amorphous indium gallium zinc oxide (α-IGZO) TFT with magnetic antenna structure was fabricated and studied for this purpose. To enhance the induction coupling efficiency while maintaining the same small antenna size, a magnetic core structure consisting of Ni and nanowires was formed under the antenna. With the micro-antenna connected to a source/drain or a gate of the TFT, working electrical signals were well controlled. The results demonstrated the device as an alternative solution to existing wire connections which cause a number of problems in various fields such as flexible/wearable devices, body implanted devices, micro/nano robots, and sensors for the ‘internet of things’ (IoT).

  6. Pulse Thermal Processing for Low Thermal Budget Integration of IGZO Thin Film Transistors

    SciTech Connect

    Noh, Joo Hyon; Joshi, Pooran C.; Kuruganti, Teja; Rack, Philip D.

    2014-11-26

    Pulse thermal processing (PTP) has been explored for low thermal budget integration of indium gallium zinc oxide (IGZO) thin film transistors (TFTs). The IGZO TFTs are exposed to a broadband (0.2-1.4 m) arc lamp radiation spectrum with 100 pulses of 1 msec pulse width. The impact of radiant exposure power on the TFT performance was analyzed in terms of the switching characteristics and bias stress reliability characteristics, respectively. The PTP treated IGZO TFTs with power density of 3.95 kW/cm2 and 0.1 sec total irradiation time showed comparable switching properties, at significantly lower thermal budget, to furnace annealed IGZO TFT. The typical field effect mobility FE, threshold voltage VT, and sub-threshold gate swing S.S were calculated to be 7.8 cm2/ V s, 8.1 V, and 0.22 V/ decade, respectively. The observed performance shows promise for low thermal budget TFT integration on flexible substrates exploiting the large-area, scalable PTP technology.

  7. Wireless thin film transistor based on micro magnetic induction coupling antenna

    PubMed Central

    Jun, Byoung Ok; Lee, Gwang Jun; Kang, Jong Gu; Kim, Seunguk; Choi, Ji-Woong; Cha, Seung Nam; Sohn, Jung Inn; Jang, Jae Eun

    2015-01-01

    A wireless thin film transistor (TFT) structure in which a source/drain or a gate is connected directly to a micro antenna to receive or transmit signals or power can be an important building block, acting as an electrical switch, a rectifier or an amplifier, for various electronics as well as microelectronics, since it allows simple connection with other devices, unlike conventional wire connections. An amorphous indium gallium zinc oxide (α-IGZO) TFT with magnetic antenna structure was fabricated and studied for this purpose. To enhance the induction coupling efficiency while maintaining the same small antenna size, a magnetic core structure consisting of Ni and nanowires was formed under the antenna. With the micro-antenna connected to a source/drain or a gate of the TFT, working electrical signals were well controlled. The results demonstrated the device as an alternative solution to existing wire connections which cause a number of problems in various fields such as flexible/wearable devices, body implanted devices, micro/nano robots, and sensors for the ‘internet of things’ (IoT). PMID:26691929

  8. Ar plasma treated ZnON transistor for future thin film electronics

    NASA Astrophysics Data System (ADS)

    Lee, Eunha; Kim, Taeho; Benayad, Anass; Kim, HeeGoo; Jeon, Sanghun; Park, Gyeong-Su

    2015-09-01

    To achieve high-mobility and high-reliability oxide thin film transistors (TFTs), ZnON has been investigated following an anion control strategy based on the substitution of oxygen with nitrogen in ZnO. However, as nitrogen possesses, compared to oxygen, a low reactivity with Zn, the chemical composition of ZnON changes easily, causing in turn a degradation of both the performance and the stability. Here, we have solved the issues of long-time stability and composition non-uniformity while maintaining a high channel mobility by adopting the argon plasma process, which can delay the reaction of oxygen with Zn-O-N; as a result, owing to the formation of very fine nano-crystalline structure in stable glassy phase without changes in the chemical composition, the material properties and stability under e-radiation have significantly improved. In particular, the channel mobility of the ZnON TFTs extracted from the pulsed I-V method was measured to be 138 cm2/V s.

  9. Wireless thin film transistor based on micro magnetic induction coupling antenna.

    PubMed

    Jun, Byoung Ok; Lee, Gwang Jun; Kang, Jong Gu; Kim, Seunguk; Choi, Ji-Woong; Cha, Seung Nam; Sohn, Jung Inn; Jang, Jae Eun

    2015-01-01

    A wireless thin film transistor (TFT) structure in which a source/drain or a gate is connected directly to a micro antenna to receive or transmit signals or power can be an important building block, acting as an electrical switch, a rectifier or an amplifier, for various electronics as well as microelectronics, since it allows simple connection with other devices, unlike conventional wire connections. An amorphous indium gallium zinc oxide (α-IGZO) TFT with magnetic antenna structure was fabricated and studied for this purpose. To enhance the induction coupling efficiency while maintaining the same small antenna size, a magnetic core structure consisting of Ni and nanowires was formed under the antenna. With the micro-antenna connected to a source/drain or a gate of the TFT, working electrical signals were well controlled. The results demonstrated the device as an alternative solution to existing wire connections which cause a number of problems in various fields such as flexible/wearable devices, body implanted devices, micro/nano robots, and sensors for the 'internet of things' (IoT). PMID:26691929

  10. Ar plasma treated ZnON transistor for future thin film electronics

    SciTech Connect

    Lee, Eunha E-mail: jeonsh@korea.ac.kr; Benayad, Anass; Kim, HeeGoo; Park, Gyeong-Su; Kim, Taeho; Jeon, Sanghun E-mail: jeonsh@korea.ac.kr

    2015-09-21

    To achieve high-mobility and high-reliability oxide thin film transistors (TFTs), ZnON has been investigated following an anion control strategy based on the substitution of oxygen with nitrogen in ZnO. However, as nitrogen possesses, compared to oxygen, a low reactivity with Zn, the chemical composition of ZnON changes easily, causing in turn a degradation of both the performance and the stability. Here, we have solved the issues of long-time stability and composition non-uniformity while maintaining a high channel mobility by adopting the argon plasma process, which can delay the reaction of oxygen with Zn–O–N; as a result, owing to the formation of very fine nano-crystalline structure in stable glassy phase without changes in the chemical composition, the material properties and stability under e-radiation have significantly improved. In particular, the channel mobility of the ZnON TFTs extracted from the pulsed I−V method was measured to be 138 cm{sup 2}/V s.

  11. Polycrystalline silicon thin-film transistors fabricated by Joule-heating-induced crystallization

    NASA Astrophysics Data System (ADS)

    Hong, Won-Eui; Ro, Jae-Sang

    2015-01-01

    Joule-heating-induced crystallization (JIC) of amorphous silicon (a-Si) films is carried out by applying an electric pulse to a conductive layer located beneath or above the films. Crystallization occurs across the whole substrate surface within few tens of microseconds. Arc instability, however, is observed during crystallization, and is attributed to dielectric breakdown in the conductor/insulator/transformed polycrystalline silicon (poly-Si) sandwich structures at high temperatures during electrical pulsing for crystallization. In this study, we devised a method for the crystallization of a-Si films while preventing arc generation; this method consisted of pre-patterning an a-Si active layer into islands and then depositing a gate oxide and gate electrode. Electric pulsing was then applied to the gate electrode formed using a Mo layer. The Mo layer was used as a Joule-heat source for the crystallization of pre-patterned active islands of a-Si films. JIC-processed poly-Si thin-film transistors (TFTs) were fabricated successfully, and the proposed method was found to be compatible with the standard processing of coplanar top-gate poly-Si TFTs.

  12. Ultraviolet-Patternable Polymer Insulator for Organic Thin-Film Transistors on Flexible Substrates

    NASA Astrophysics Data System (ADS)

    Wu, Chung-Ming; Su, Shui-Hsiang; Wang, Hong-Tai; Yokoyama, Meiso; Fu, Shen-Li

    2011-04-01

    In this work, we describe the fabrication of pentacene-based organic thin-film transistors (OTFTs) on a flexible substrate using a UV-patternable polymer material, mr-UVCur06, as the gate insulator. The device structure is poly(ethylene terephthalate) (PET)/indium-tin oxide (ITO)/mr-UVCur06/pentacene/Au (source/drain). In addition to its solution-processable capability, mr-UVCur06 is directly patternable by UV light in a low-temperature process. The OTFT has an on-off ratio that approaches 105, and its pattern resolution can reach 5 µm. Additionally, UV/ozone post-treatment of the patterned mr-UVCur06 can illuminate the organic contaminants from its surface and significantly improve the performance of OTFTs. Moreover, the effect of UV/ozone post-treatment on the polymer dielectric is confirmed using a Fourier transform infrared (FT-IR) spectrometer. Owing to its highly desired characteristics such as photopatternability and low-temperature process, mr-UVCur06 is feasible for low-cost, large-area flexible device applications.

  13. Photo-modulated thin film transistor based on dynamic charge transfer within quantum-dots-InGaZnO interface

    SciTech Connect

    Liu, Xiang; Yang, Xiaoxia; Liu, Mingju; Tao, Zhi; Wei, Lei Li, Chi Zhang, Xiaobing; Wang, Baoping; Dai, Qing; Nathan, Arokia

    2014-03-17

    The temporal development of next-generation photo-induced transistor across semiconductor quantum dots and Zn-related oxide thin film is reported in this paper. Through the dynamic charge transfer in the interface between these two key components, the responsibility of photocurrent can be amplified for scales of times (∼10{sup 4} A/W 450 nm) by the electron injection from excited quantum dots to InGaZnO thin film. And this photo-transistor has a broader waveband (from ultraviolet to visible light) optical sensitivity compared with other Zn-related oxide photoelectric device. Moreover, persistent photoconductivity effect can be diminished in visible waveband which lead to a significant improvement in the device's relaxation time from visible illuminated to dark state due to the ultrafast quenching of quantum dots. With other inherent properties such as integrated circuit compatible, low off-state current and high external quantum efficiency resolution, it has a great potential in the photoelectric device application, such as photodetector, phototransistor, and sensor array.

  14. Nanostructured zinc oxide thin film by simple vapor transport deposition

    NASA Astrophysics Data System (ADS)

    Athma, P. V.; Martinez, Arturo I.; Johns, N.; Safeera, T. A.; Reshmi, R.; Anila, E. I.

    2015-09-01

    Zinc oxide (ZnO) nanostructures find applications in optoelectronic devices, photo voltaic displays and sensors. In this work zinc oxide nanostructures in different forms like nanorods, tripods and tetrapods have been synthesized by thermal evaporation of zinc metal and subsequent deposition on a glass substrate by vapor transport in the presence of oxygen. It is a comparatively simpler and environment friendly technique for the preparation of thin films. The structure, morphology and optical properties of the synthesized nanostructured thin film were characterized in detail by using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) and photoluminescence (PL). The film exhibited bluish white emission with Commission International d'Eclairage (CIE) coordinates x = 0.22, y = 0.31.

  15. Electrical Properties and Reliability Analysis of Solution-Processed Indium Tin Zinc Oxide Thin Film Transistors with O2-Plasma Treatment.

    PubMed

    Ko, Sun Wook; Kim, Soon Kon; Kim, Jong Min; Cho, Jae Hee; Park, Hyoung Sun; Choi, Byoung Deog

    2015-10-01

    In this paper, we report the effects of O2-plasma treatment on the reliability and electrical properties of indium tin zinc oxide (ITZO) films. Excellent electrical properties, including a saturation mobility (μsat) of ~20.2 cm2/V · s, a threshold voltage (VTH) of ~-6.8 V, a sub-threshold swing (S.S) of ~0.956 V/decade, and an on/off current ratio (ION/OFF) of ~10(5) can be found with a molarity of 0.4 M and ratio of In:Zn:Sn = 2:1:2. Following O2-plasma treatment, it was confirmed that the electrical properties of the ITZO films are improved when compared to the untreated films. The devices showed a decreased S.S of ~0.51 V/decade, while the VTH and ION/OFF tended to increase. To determine the reliability of a-ITZO TFTs, we analyzed the electrical characteristics according to gate bias stress, VG,stress = 10 V for 4000 s. Improved reliability was confirmed when compared with the variation in threshold voltage prior to O2-plasma treatment, most likely stemming from a smooth surface on the active layer as a result of O2-plasma treatment. We were able to obtain a solution a-ITZO film transmittance of 92% in the visible light region (400~700 nm). These results show that a-ITZO TFTs fabricated via solution process with optimized molar ratio exhibit good electrical properties. a-ITZO films fabricated via spin-coating are a visible alternative to those fabricated via high-cost sputtering methods, and are applicable in flexible and transparent electronics. PMID:26726354

  16. High-performance organic thin-film transistors of J-stacked squaraine dyes.

    PubMed

    Gsänger, Marcel; Kirchner, Eva; Stolte, Matthias; Burschka, Christian; Stepanenko, Vladimir; Pflaum, Jens; Würthner, Frank

    2014-02-12

    We have synthesized a series of dipolar squaraine dyes that contain dicyanovinyl groups as acceptor and benzannulated five-membered ring heterocycles with alkyl chains of varied length as donor moieties. Based on these squaraines, thin-film transistors (TFT) were fabricated by spin coating and solution shearing. Moreover, with one of these squaraine derivatives vacuum-deposited TFTs were prepared as well. Our detailed studies revealed that the transistor performance of the present series of squaraines is strongly dependent on their structural features as well as on the processing method of thin films. Thus, solution-sheared OTFTs of selenium squaraine bearing dodecyl substituents (denoted as Se-SQ-C12) performed best with a maximum hole mobility of 0.45 cm(2) V(-1) s(-1), which is by far the highest value yet reported for OTFTs based on squaraines. This value was even surpassed by vacuum-deposited thin films of n-butyl-substituted selenium squaraine Se-SQ-C4, the only sublimable compound in this series, exhibiting a record hole mobility of 1.3 cm(2) V(-1) s(-1). Furthermore, we have investigated the morphology of the thin films and the molecular packing of these squaraine dyes by optical spectroscopy, atomic force microscopy, and X-ray diffraction. These studies revealed a relationship between the molecular structure, packing motif, thin-film morphology, and transistor performance of the squaraine dyes. From the supramolecular point of view two packing features discovered in the single crystal structure of Se-SQ-C8 are of particular interest with regard to the structure-functionality relationship: The first is the slipped and antiparallel π-stacking motif which ensures cancellation of the molecules' dipole moments and J-type absorption band formation in thin films. The second is the presence of CN···Se noncovalent bonds which show similarities to the more common halogen-bonding interactions and which interconnect the individual one-dimensional slipped

  17. Ferroelectric memory element based on thin film field effect transistor

    NASA Astrophysics Data System (ADS)

    Poghosyan, A. R.; Aghamalyan, N. R.; Elbakyan, E. Y.; Guo, R.; Hovsepyan, R. K.

    2013-09-01

    We report the preparation and investigation of ferroelectric field effect transistors (FET) using ZnO:Li films with high field mobility of the charge carriers as a FET channel and as a ferroelectric active element simultaneously. The possibility for using of ferroelectric FET based on the ZnO:Li films in the ZnO:Li/LaB6 heterostructure as a bi-stable memory element for information recording is shown. The proposed ferroelectric memory structure does not manifest a fatigue after multiple readout of once recorded information.

  18. Air-Flow Navigated Crystal Growth for TIPS Pentacene-Based Organic Thin-Film Transistors

    SciTech Connect

    He, Zhengran; Chen, Jihua; Sun, Zhenzhong; Szulczewski, Greg; Li, Dawen

    2012-01-01

    6,13-bis(triisopropylsilylethynyl)pentacene (TIPS pentacene) is a promising active channel material of organic thin-film transistors (OTFTs) due to its solubility, stability, and high mobility. However, the growth of TIPS pentacene crystals is intrinsically anisotropic and thus leads to significant variation in the performance of OTFTs. In this paper, air flow is utilized to effectively reduce the TIPS pentacene crystal anisotropy and enhance performance consistency in OTFTs, and the resulted films are examined with optical microscopy, grazing-incidence X-ray diffraction, and thin-film transistor measurements. Under air-flow navigation (AFN), TIPS pentacene drop-cast from toluene solution has been observed to form thin films with improved crystal orientation and increased areal coverage on substrates, which subsequently lead to a four-fold increase of average hole mobility and one order of magnitude enhancement in performance consistency defined by the ratio of average mobility to the standard deviation of the field-effect mobilities.

  19. Monolithic metal oxide transistors.

    PubMed

    Choi, Yongsuk; Park, Won-Yeong; Kang, Moon Sung; Yi, Gi-Ra; Lee, Jun-Young; Kim, Yong-Hoon; Cho, Jeong Ho

    2015-04-28

    We devised a simple transparent metal oxide thin film transistor architecture composed of only two component materials, an amorphous metal oxide and ion gel gate dielectric, which could be entirely assembled using room-temperature processes on a plastic substrate. The geometry cleverly takes advantage of the unique characteristics of the two components. An oxide layer is metallized upon exposure to plasma, leading to the formation of a monolithic source-channel-drain oxide layer, and the ion gel gate dielectric is used to gate the transistor channel effectively at low voltages through a coplanar gate. We confirmed that the method is generally applicable to a variety of sol-gel-processed amorphous metal oxides, including indium oxide, indium zinc oxide, and indium gallium zinc oxide. An inverter NOT logic device was assembled using the resulting devices as a proof of concept demonstration of the applicability of the devices to logic circuits. The favorable characteristics of these devices, including (i) the simplicity of the device structure with only two components, (ii) the benign fabrication processes at room temperature, (iii) the low-voltage operation under 2 V, and (iv) the excellent and stable electrical performances, together support the application of these devices to low-cost portable gadgets, i.e., cheap electronics. PMID:25777338

  20. High quality transparent conducting oxide thin films

    DOEpatents

    Gessert, Timothy A.; Duenow, Joel N.; Barnes, Teresa; Coutts, Timothy J.

    2012-08-28

    A transparent conducting oxide (TCO) film comprising: a TCO layer, and dopants selected from the elements consisting of Vanadium, Molybdenum, Tantalum, Niobium, Antimony, Titanium, Zirconium, and Hafnium, wherein the elements are n-type dopants; and wherein the transparent conducting oxide is characterized by an improved electron mobility of about 42 cm.sup.2/V-sec while simultaneously maintaining a high carrier density of .about.4.4e.times.10.sup.20 cm.sup.-3.

  1. Preparation and Evaluation of Nitrogen Doped Tungsten Oxide Thin Films

    NASA Astrophysics Data System (ADS)

    Nakagawa, Koichi; Miura, Noboru; Matsumoto, Setsuko; Nakano, Ryotaro; Matsumoto, Hironaga

    Nitrogen doped tungsten oxide thin films were prepared by RF reactive sputtering in a gas mixture of argon, oxygen and nitrogen at room temperature. As a result of X-ray photoelectron spectroscopy, it was thought that the doped nitrogen in the films is bonding to tungsten of WO3 bonding states as anion and exits in substitution sites in WO3. The optical absorption edge was shifted to lower energy region with nitrogen doping. The nitrogen doped thin films exhibit a coloration to black from transparent yellow by electrochromism. Additionally, a new peak at 2.3 eV related to nitrogen doping is observed in the spectra of color center at bleaching process.

  2. High angular sensitivity thin film tin oxide sensor

    NASA Astrophysics Data System (ADS)

    Kaur, Davinder; Madaan, Divya; Sharma, V. K.; Kapoor, A.

    2016-05-01

    We present theoretical anlaysis of a thin film SnO2 (Tin Oxide) sensor for the measurement of variation in the refractive index of the bulk media. It is based on lossy mode resonance between the absorbing thin film lossy modes and the evanescent wave. Also the addition of low index dielectric matching layer between the prism and the lossy waveguiding layer future increase the angular sensitivity and produce an efficient refractive index sensor. The angular interrogation is done and obtained sensitivity is 110 degree/RIU. Theoretical analysis of the proposed sensor based on Fresnel reflection coefficients is presented. This enhanced sensitivity will further improve the monitoring of biomolecular interactions and the higher sensitivity of the proposed configurations makes it to be a much better option to be employed for biosensing applications.

  3. Changes in the Young Modulus of hafnium oxide thin films

    NASA Astrophysics Data System (ADS)

    Vargas, André Luís Marin; de Araújo Ribeiro, Fabiana; Hübler, Roberto

    2015-12-01

    Hafnium-oxide (HfO2)-based materials have been extensively researched due to their excellent optical and electrical properties. However, the literature data on the mechanical properties of these materials and its preparation for heavy machinery application is very limited. The aim of this work is to deposit hafnium oxide thin films by DC reactive magnetron sputtering with different Young's Modulus from the Ar/O2 concentration variation in the deposition chamber. The thin films were deposited by DC reactive magnetron sputtering with different Ar/O2 gas concentrations in plasma. After deposition, HfOx thin films were characterized through XRD, AFM, RBS and XRF. In this regard, it was observed that the as-deposited HfO2 films were mostly amorphous in the lower Ar/O2 gas ratio and transformed to polycrystalline with monoclinic structure as the Ar/O2 gas ratios grows. RBS technique shows good compromise between the experimental data and the simulated ones. It was possible to tailored the Young Modulus of the films by alter the Ar/O2 content on the deposition chamber without thermal treatment.

  4. Fabrication of amorphous InGaZnO thin-film transistor-driven flexible thermal and pressure sensors

    NASA Astrophysics Data System (ADS)

    Park, Ick-Joon; Jeong, Chan-Yong; Cho, In-Tak; Lee, Jong-Ho; Cho, Eou-Sik; Kwon, Sang Jik; Kim, Bosul; Cheong, Woo-Seok; Song, Sang-Hun; Kwon, Hyuck-In

    2012-10-01

    In this work, we present the results concerning the use of amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistor (TFT) as a driving transistor of the flexible thermal and pressure sensors which are applicable to artificial skin systems. Although the a-IGZO TFT has been attracting much attention as a driving transistor of the next-generation flat panel displays, no study has been performed about the application of this new device to the driving transistor of the flexible sensors yet. The proposed thermal sensor pixel is composed of the series-connected a-IGZO TFT and ZnO-based thermistor fabricated on a polished metal foil, and the ZnO-based thermistor is replaced by the pressure sensitive rubber in the pressure sensor pixel. In both sensor pixels, the a-IGZO TFT acts as the driving transistor and the temperature/pressure-dependent resistance of the ZnO-based thermistor/pressure-sensitive rubber mainly determines the magnitude of the output currents. The fabricated a-IGZO TFT-driven flexible thermal sensor shows around a seven times increase in the output current as the temperature increases from 20 °C to 100 °C, and the a-IGZO TFT-driven flexible pressure sensors also exhibit high sensitivity under various pressure environments.

  5. Determination of oxygen diffusion kinetics during thin film ruthenium oxidation

    SciTech Connect

    Coloma Ribera, R. Kruijs, R. W. E. van de; Yakshin, A. E.; Bijkerk, F.

    2015-08-07

    In situ X-ray reflectivity was used to reveal oxygen diffusion kinetics for thermal oxidation of polycrystalline ruthenium thin films and accurate determination of activation energies for this process. Diffusion rates in nanometer thin RuO{sub 2} films were found to show Arrhenius behaviour. However, a gradual decrease in diffusion rates was observed with oxide growth, with the activation energy increasing from about 2.1 to 2.4 eV. Further exploration of the Arrhenius pre-exponential factor for diffusion process revealed that oxidation of polycrystalline ruthenium joins the class of materials that obey the Meyer-Neldel rule.

  6. Germanium and Silicon Nanocrystal Thin-Film Field-Effect Transistors from Solution

    SciTech Connect

    Holman, Zachary C.; Liu, Chin-Yi; Kortshagen, Uwe R.

    2010-07-09

    Germanium and silicon have lagged behind more popular II-VI and IV-VI semiconductor materials in the emerging field of semiconductor nanocrystal thin film devices. We report germanium and silicon nanocrystal field-effect transistors fabricated by synthesizing nanocrystals in a plasma, transferring them into solution, and casting thin films. Germanium devices show n-type, ambipolar, or p-type behavior depending on annealing temperature with electron and hole mobilities as large as 0.02 and 0.006 cm2 V-1 s-1, respectively. Silicon devices exhibit n-type behavior without any postdeposition treatment, but are plagued by poor film morphology.

  7. The effect of thermal annealing on pentacene thin film transistor with micro contact printing.

    PubMed

    Shin, Hong-Sik; Yun, Ho-Jin; Baek, Kyu-Ha; Ham, Yong-Hyun; Park, Kun-Sik; Kim, Dong-Pyo; Lee, Ga-Won; Lee, Hi-Deok; Lee, Kijun; Do, Lee-Mi

    2012-07-01

    We used micro contact printing (micro-CP) to fabricate inverted coplanar pentacene thin film transistors (TFTs) with 1-microm channels. The patterning of micro-scale source/drain electrodes without etch process was successfully achieved using Polydimethylsiloxane (PDMS) elastomer stamp. We used the Ag nano particle ink as an electrode material, and the sheet resistance and surface roughness of the Ag electrodes were effectively reduced with the 2-step thermal annealing on a hotplate, which improved the mobility, the on-off ratio, and the subthreshold slope (SS) of the pentacene TFTs. In addition, the device annealing on a hotplate in a N2 atmosphere for 30 sec can enhance the off-current and the mobility properties of OTFTs without damaging the pentacene thin films and increase the adhesion between pentacene and dielectric layer (SiO2), which was investigated with the pentacene films phase change of the XRD spectrum after device annealing. PMID:22966565

  8. Ordering of pentacene in organic thin film transistors induced by irradiation of infrared light

    SciTech Connect

    Wang, C. H.; Chen, S. W.; Hwang, J.

    2009-09-07

    The device performances of pentacene-based organic thin film transistors (OTFTs) were greatly improved by irradiation of infrared light. The field effect mobility and maximum drain current increase from 0.20{+-}0.01 to 0.57{+-}0.02 cm{sup 2}/V s and 1.14x10{sup -5} to 4.91x10{sup -5} A, respectively. The (001) peak of the pentacene 'thin film' phase increases in intensity by 4.5 times after infrared irradiation at 50 W for 2 h. Two types of crystal orientations, i.e., 'crystal I' (2{theta}=5.91 deg.) and 'crystal II' (2{theta}=5.84 deg.), coexist in the pentacene. The improvement of the characteristics of OTFTs is attributed to crystallization and crystal reorientation induced by infrared light.

  9. Fabrication of InGaN thin-film transistors using pulsed sputtering deposition

    NASA Astrophysics Data System (ADS)

    Itoh, Takeki; Kobayashi, Atsushi; Ueno, Kohei; Ohta, Jitsuo; Fujioka, Hiroshi

    2016-07-01

    We report the first demonstration of operational InGaN-based thin-film transistors (TFTs) on glass substrates. The key to our success was coating the glass substrate with a thin amorphous layer of HfO2, which enabled a highly c-axis-oriented growth of InGaN films using pulsed sputtering deposition. The electrical characteristics of the thin films were controlled easily by varying their In content. The optimized InGaN-TFTs exhibited a high on/off ratio of ~108, a field-effect mobility of ~22 cm2 V‑1 s‑1, and a maximum current density of ~30 mA/mm. These results lay the foundation for developing high-performance electronic devices on glass substrates using group III nitride semiconductors.

  10. Fabrication of InGaN thin-film transistors using pulsed sputtering deposition.

    PubMed

    Itoh, Takeki; Kobayashi, Atsushi; Ueno, Kohei; Ohta, Jitsuo; Fujioka, Hiroshi

    2016-01-01

    We report the first demonstration of operational InGaN-based thin-film transistors (TFTs) on glass substrates. The key to our success was coating the glass substrate with a thin amorphous layer of HfO2, which enabled a highly c-axis-oriented growth of InGaN films using pulsed sputtering deposition. The electrical characteristics of the thin films were controlled easily by varying their In content. The optimized InGaN-TFTs exhibited a high on/off ratio of ~10(8), a field-effect mobility of ~22 cm(2) V(-1) s(-1), and a maximum current density of ~30 mA/mm. These results lay the foundation for developing high-performance electronic devices on glass substrates using group III nitride semiconductors. PMID:27383148

  11. Fabrication of InGaN thin-film transistors using pulsed sputtering deposition

    PubMed Central

    Itoh, Takeki; Kobayashi, Atsushi; Ueno, Kohei; Ohta, Jitsuo; Fujioka, Hiroshi

    2016-01-01

    We report the first demonstration of operational InGaN-based thin-film transistors (TFTs) on glass substrates. The key to our success was coating the glass substrate with a thin amorphous layer of HfO2, which enabled a highly c-axis-oriented growth of InGaN films using pulsed sputtering deposition. The electrical characteristics of the thin films were controlled easily by varying their In content. The optimized InGaN-TFTs exhibited a high on/off ratio of ~108, a field-effect mobility of ~22 cm2 V−1 s−1, and a maximum current density of ~30 mA/mm. These results lay the foundation for developing high-performance electronic devices on glass substrates using group III nitride semiconductors. PMID:27383148

  12. Electrochemical characterization of thin film electrodes toward developing a DNA transistor.

    PubMed

    Harrer, Stefan; Ahmed, Shafaat; Afzali-Ardakani, Ali; Luan, Binquan; Waggoner, Philip S; Shao, Xiaoyan; Peng, Hongbo; Goldfarb, Dario L; Martyna, Glenn J; Rossnagel, Stephen M; Deligianni, Lili; Stolovitzky, Gustavo A

    2010-12-21

    The DNA-Transistor is a device designed to control the translocation of single-stranded DNA through a solid-state nanopore. Functionality of the device is enabled by three electrodes exposed to the DNA-containing electrolyte solution within the pore and the application of a dynamic electrostatic potential well between the electrodes to temporarily trap a DNA molecule. Optimizing the surface chemistry and electrochemical behavior of the device is a necessary (but by no means sufficient) step toward the development of a functional device. In particular, effects to be eliminated are (i) electrochemically induced surface alteration through corrosion or reduction of the electrode surface and (ii) formation of hydrogen or oxygen bubbles inside the pore through water decomposition. Even though our motivation is to solve problems encountered in DNA transistor technology, in this paper we report on generic surface chemistry results. We investigated a variety of electrode-electrolyte-solvent systems with respect to their capability of suppressing water decomposition and maintaining surface integrity. We employed cyclic voltammetry and long-term amperometry as electrochemical test schemes, X-ray photoelectron spectroscopy, atomic force microscopy, and scanning, as well as transmission electron microscopy as analytical tools. Characterized electrode materials include thin films of Ru, Pt, nonstoichiometric TiN, and nonstoichiometric TiN carrying a custom-developed titanium oxide layer, as well as custom-oxidized nonstoichiometric TiN coated with a monolayer of hexadecylphosphonic acid (HDPA). We used distilled water as well as aqueous solutions of poly(ethylene glycol) (PEG-300) and glycerol as solvents. One millimolar KCl was employed as electrolyte in all solutions. Our results show that the HDPA-coated custom-developed titanium oxide layer effectively passivates the underlying TiN layer, eliminating any surface alterations through corrosion or reduction within a voltage

  13. Fabrication and characterization of thin-film transistor materials and devices

    NASA Astrophysics Data System (ADS)

    Hong, David

    A class of inorganic thin-film transistor (TFT) semiconductor materials has emerged involving oxides composed of post-transitional cations with (n-1)d 10ns0 (n≥4) electronic configurations. This thesis is devoted to the pursuit of topics involving the development of these materials for TFT applications: Deposition of zinc oxide and zinc tin oxide semiconductor layers via reactive sputtering from a metal target, and the characterization of indium gallium zinc oxide (IGZO)-based TFTs utilizing various insulator materials as the gate dielectric. The first topic involves the deposition of oxide semiconductor layers via reactive sputtering from a metal target. Two oxide semiconductors are utilized for fabricating TFTs via reactive sputtering from a metal target: zinc oxide and zinc tin oxide. With optimized processing parameters, zinc oxide and zinc tin oxide via this deposition method exhibit similar characteristics to TFTs fabricated via sputtering from a ceramic target. Additionally the effects of gate capacitance density and gate dielectric material are explored utilizing TFTs with IGZO as the semiconductor layers. IGZO-based TFTs exhibit ideal behavior with improved TFT performance such as higher current drive at a given overvoltage, a decrease in the subthreshold swing, and a decrease in the magnitude of the turn-on voltage. Additionally it is shown that silicon dioxide is the preferred dielectric material, with silicon nitride a poor choice for oxide-based TFTs. Finally a simple method to characterize the band tail state distribution near the conduction band minimum of a semiconductor by analyzing two-terminal current-voltage characteristics of a TFT with a floating gate is presented. The characteristics trap energy (ET) as a function of post-deposition annealing temperature is shown to correlate very well with IGZO TFT performance, with a lower value of E T, corresponding to a more abrupt distribution of band tail states, correlating with improved TFT mobility

  14. Nano-crystallization in ZnO-doped In2O3 thin films via excimer laser annealing for thin-film transistors

    NASA Astrophysics Data System (ADS)

    Fujii, Mami N.; Ishikawa, Yasuaki; Ishihara, Ryoichi; van der Cingel, Johan; Mofrad, Mohammad R. T.; Bermundo, Juan Paolo Soria; Kawashima, Emi; Tomai, Shigekazu; Yano, Koki; Uraoka, Yukiharu

    2016-06-01

    In a previous work, we reported the high field effect mobility of ZnO-doped In2O3 (IZO) thin film transistors (TFTs) irradiated by excimer laser annealing (ELA) [M. Fujii et al., Appl. Phys. Lett. 102, 122107 (2013)]. However, a deeper understanding of the effect of ELA on the IZO film characteristics based on crystallinity, carrier concentrations, and optical properties is needed to control localized carrier concentrations for fabricating self-aligned structures in the same oxide film and to adequately explain the physical characteristics. In the case of as-deposited IZO film used as the channel, a high carrier concentration due to a high density of oxygen vacancies was observed; such a film does not show the required TFT characteristics but can act as a conductive film. We achieved a decrease in the carrier concentration of IZO films by crystallization using ELA. This means that ELA can form localized conductive or semi-conductive areas on the IZO film. We confirmed that the reason for the carrier concentration decrease was the decrease of oxygen-deficient regions and film crystallization. The annealed IZO films showed nano-crystalline phase, and the temperature at the substrate was substantially less than the temperature limit for flexible films such as plastic, which is 50°C. This paves the way for the formation of self-aligned structures and separately formed conductive and semi-conductive regions in the same oxide film.

  15. Testing of flexible InGaZnO-based thin-film transistors under mechanical strain

    NASA Astrophysics Data System (ADS)

    Münzenrieder, N. S.; Cherenack, K. H.; Tröster, G.

    2011-08-01

    Thin-film transistors (TFTs) fabricated on flexible plastic substrates are an integral part of future flexible large-area electronic devices like displays and smart textiles. Devices for such applications require stable electrical performance under electrical stress and also during applied mechanical stress induced by bending of the flexible substrate. Mechanical stress can be tensile or compressive strain depending on whether the TFT is located outside or inside of the bending plane. Especially the impact of compressive bending on TFT performance is hard to measure, because the device is covered with the substrate in this case. We present a method which allows us to continuously measure the electrical performance parameters of amorphous Indium-Gallium-Zinc Oxide (a-IGZO) based TFTs exposed to arbitrary compressive and tensile bending radii. To measure the influence of strain on a TFT it is attached and electrically connected to a flexible carrier foil, which afterwards is fastened to two plates in our bending tester. The bending radius can be adjusted by changing the distance between these plates. Thus it is possible to apply bending radii in the range between a totally flat substrate and ≈1 mm, corresponding to a strain of ≈3.5%. The tested bottom-gate TFTs are especially designed for use with our bending tester and fabricated on 50 μm thick flexible Kapton® E polyimide substrates. To show the different application areas of our bending method we characterized our TFTs while they are bent to different tensile and compressive bending radii. These measurements show that the field effect mobilities and threshold voltages of the tested a-IGZO TFTs are nearly, but not absolutely, stable under applied strain, compared to the initial values the mobilities shift by ≈3.5% in the tensile case and ≈-1.5% in the compressive one, at a bending radius of 8 mm. We also measured the influence of repeated bending (2500 cycles over ≈70 h), where a shift of the

  16. A water-gated organic thin film transistor as a sensor for water-borne amines.

    PubMed

    Algarni, Saud A; Althagafi, Talal M; Naim, Abdullah Al; Grell, Martin

    2016-06-01

    The p-type semiconducting polymer Poly(2,5-bis(3-hexadecylthiophen-2-yl)thieno[3,2-b]thiophene) (PBTTT) displays innate sensitivity to water-borne amines. We demonstrate this with the help of water-gated PBTTT thin film transistors (TFTs). When octylamine is added to the gating water, TFTs respond with a significantly reduced saturated drain current. Underlying TFT drift is minimised by initial conditioning, and remaining drift can be accounted for by normalising current response to the current level under purge immediately before exposure. Normalised current response vs. amine concentration is reproducible between different transistors, and can be modelled by a Langmuir surface adsorption isotherm, which suggests physisorption of analyte at the PBTTT surface, rather than bulk penetration. Same PBTTT transistors do not respond to 1- octanol, confirming the specific affinity between amines and thiophene- based organic semiconductors. PMID:27130096

  17. Vanadium oxide thin film with improved sheet resistance uniformity

    NASA Astrophysics Data System (ADS)

    Généreux, Francis; Provençal, Francis; Tremblay, Bruno; Boucher, Marc-André; Julien, Christian; Alain, Christine

    2014-06-01

    This paper reports on the deposition of vanadium oxide thin films with sheet resistance uniformity better than 2.5% over a 150 mm wafer. The resistance uniformity within the array is estimated to be less than 1%, which is comparable with the value reported for amorphous silicon-based microbolometer arrays. In addition, this paper also shows that the resistivity of vanadium oxide, like amorphous silicon, can be modeled by Arrhenius' equation. This result is expected to significantly ease the computation of the correction table required for TEC-less operation of VOx-based microbolometer arrays.

  18. Copper oxide thin films for ethanol sensing

    NASA Astrophysics Data System (ADS)

    Lamri Zeggar, M.; Bourfaa, F.; Adjimi, A.; Aida, M. S.; Attaf, N.

    2016-03-01

    The present is a study of a new active layer for ethanol (C2H5OH) vapour sensing devices based on copper oxide (CuO). CuO films were prepared by spray ultrasonic pyrolysis at a substrate temperature of 350 °C. Films microstructure was examined by X-ray diffraction and atomic force microscopy. Vapour-sensing testing was conducted using static vapour-sensing system, at different operating temperatures in the range of 100°C to 175°C for the vapour concentration of 300 ppm. The results show a high response of 45% at relatively low operating temperatures of 150°C towards ethanol vapour.

  19. Geometric Effect of Channel on Device Performance in Pentacene Thin-Film Transistor

    NASA Astrophysics Data System (ADS)

    Kang, Seong Jun; Noh, Myungkeun; Park, Dae Sik; Kim, Hui Jung; Kim, Sang Yeol; Koo, Bon Won; Kang, In Nam; Whang, Chung Nam

    2004-11-01

    We fabricated pentacene thin film-transistors on a glass substrate with a SiO2 layer via thermal evaporation in ultrahigh vacuum. We investigated the influence of channel length, channel width, and the deposition rate of a pentacene layer on organic thin film transistors (OTFTs) performance. Field-effect mobility of the transistors markedly increased as channel width decreased and channel length increased. The maximum drain current of OTFTs increased as channel length decreased. These observations indicate that the grain boundary scattering of charge carriers in the pentacene layer is a major hurdle in charge conduction, similarly to the observation in poly-Si TFTs. The maximum field-effect mobility was 0.69 cm2/Vs for a device prepared at 0.1 Å/s with a 50 μm channel length and a 20 μm channel width. Channel width/length ratio (W/L) as well as the deposition rate of the pentacene layer should be carefully chosen to increase field-effect mobility and maximum drain current in OTFTs.

  20. Low-temperature processable amorphous In-W-O thin-film transistors with high mobility and stability

    SciTech Connect

    Kizu, Takio; Aikawa, Shinya; Mitoma, Nobuhiko; Shimizu, Maki; Gao, Xu; Lin, Meng-Fang; Tsukagoshi, Kazuhito; Nabatame, Toshihide

    2014-04-14

    Thin-film transistors (TFTs) with a high stability and a high field-effect mobility have been achieved using W-doped indium oxide semiconductors in a low-temperature process (∼150 °C). By incorporating WO{sub 3} into indium oxide, TFTs that were highly stable under a negative bias stress were reproducibly achieved without high-temperature annealing, and the degradation of the field-effect mobility was not pronounced. This may be due to the efficient suppression of the excess oxygen vacancies in the film by the high dissociation energy of the bond between oxygen and W atoms and to the different charge states of W ions.

  1. Investigation of channel width-dependent threshold voltage variation in a-InGaZnO thin-film transistors

    SciTech Connect

    Liu, Kuan-Hsien; Chou, Wu-Ching; Chang, Ting-Chang; Wu, Ming-Siou; Hung, Yi-Syuan; Sze, Simon M.; Hung, Pei-Hua; Chu, Ann-Kuo; Hsieh, Tien-Yu; Yeh, Bo-Liang

    2014-03-31

    This Letter investigates abnormal channel width-dependent threshold voltage variation in amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistors. Unlike drain-induced source barrier lowering effect, threshold voltage increases with increasing drain voltage. Furthermore, the wider the channel, the larger the threshold voltage observed. Because of the surrounding oxide and other thermal insulating material and the low thermal conductivity of the IGZO layer, the self-heating effect will be pronounced in wider channel devices and those with a larger operating drain bias. To further clarify the physical mechanism, fast IV measurement is utilized to demonstrate the self-heating induced anomalous channel width-dependent threshold voltage variation.

  2. Investigation of channel width-dependent threshold voltage variation in a-InGaZnO thin-film transistors

    NASA Astrophysics Data System (ADS)

    Liu, Kuan-Hsien; Chang, Ting-Chang; Wu, Ming-Siou; Hung, Yi-Syuan; Hung, Pei-Hua; Hsieh, Tien-Yu; Chou, Wu-Ching; Chu, Ann-Kuo; Sze, Simon M.; Yeh, Bo-Liang

    2014-03-01

    This Letter investigates abnormal channel width-dependent threshold voltage variation in amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistors. Unlike drain-induced source barrier lowering effect, threshold voltage increases with increasing drain voltage. Furthermore, the wider the channel, the larger the threshold voltage observed. Because of the surrounding oxide and other thermal insulating material and the low thermal conductivity of the IGZO layer, the self-heating effect will be pronounced in wider channel devices and those with a larger operating drain bias. To further clarify the physical mechanism, fast IV measurement is utilized to demonstrate the self-heating induced anomalous channel width-dependent threshold voltage variation.

  3. Enhanced mobility of Li-doped ZnO thin film transistors fabricated by mist chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Jeon, Hye-ji; Lee, Seul-Gi; Kim, H.; Park, Jin-Seong

    2014-05-01

    Mist chemical vapor deposition (mist-CVD)-processed, lithium (Li)-doped ZnO thin film transistors (TFTs) are investigated. Li doping significantly increases the field-effect mobility in TFTs up to ˜100 times greater than that of undoped ZnO. The addition of Li into mist-CVD-grown ZnO semiconductors leads to improved film quality, which results from the enhanced crystallinity and reduced defect states, including oxygen vacancies. Our results suggest that Li doping of ZnO-based oxide semiconductors could serve as an effective strategy for high-performance, mist-CVD-processed oxide TFTs with low-cost and low-temperature fabrication.

  4. Scanning gate study of organic thin-film field-effect transistor

    NASA Astrophysics Data System (ADS)

    Aoki, N.; Sudou, K.; Matsusaki, K.; Okamoto, K.; Ochiai, Y.

    2008-03-01

    Scanning gate microscopy (SGM) has been applied for a study of organic thin-film field effect transistor (OFET). In contrast to one-dimensional nano-material such a carbon nanonube or nano-structure such a quantum point contact, visualization a transport characteristic of OFET channel is basically rather difficult since the channel width is much larger than the size of the SGM tip. Nevertheless, Schottky barriers are successfully visualized at the boundary between the metal electrodes and the OFET channel at ambient atmosphere.

  5. All solution processed organic thin film transistor-backplane with printing technology for electrophoretic display

    USGS Publications Warehouse

    Lee, Myung W.; Song, C.K.

    2012-01-01

    In this study, solution processes were developed for backplane using an organic thin film transistor (OTFT) as a driving device for an electrophoretic display (EPD) panel. The processes covered not only the key device of OTFTs but also interlayer and pixel electrodes. The various materials and printing processes were adopted to achieve the requirements of devices and functioning layers. The performance of OTFT of the backplane was sufficient to drive EPD sheet by producing a mobility of 0.12 cm2/v x sec and on/off current ratio of 10(5).

  6. Unified gate capacitance model of polysilicon thin-film transistors for circuit applications

    NASA Astrophysics Data System (ADS)

    Deng, W.; Zheng, X.; Chen, R.; Wu, W.; An, Z.

    2008-07-01

    The characteristics of the gate capacitance at polysilicon thin-film transistors (poly-Si TFTs) based on terms of surface potential have been described and modeled in this paper. An explicit approximate relation for surface potential as a function of terminal voltages is developed. The theory is based on an assumed exponential distribution of trap states in the energy gap. Moreover, the model has been found to give an accurate description of the unique features of poly-Si TFTs, such as rapid increase of Cgs in leakage region and Cgd in kink region. The good agreement between simulated model results and experimental data confirms the accuracy and efficiency of this model.

  7. Influence of molecular structure and microstructure on device performance of polycrystalline pentacene thin-film transistors

    NASA Astrophysics Data System (ADS)

    Cheng, Horng-Long; Mai, Yu-Shen; Chou, Wei-Yang; Chang, Li-Ren

    2007-04-01

    The authors have fabricated the pentacene thin films on polymethylmethacrylate (PMMA) and on silicon dioxide dielectric surfaces featuring similar surface energy and surface roughness. On both surfaces the pentacene films displayed high crystal quality from x-ray diffraction scans, although the film on PMMA had significantly smaller grain size. The pentacene transistors with PMMA exhibited excellent electrical characteristics, including high mobility of above 1.1cm2/Vs, on/off ratio above 106, and sharp subthreshold slope below 1V/decade. The analysis of molecular microstructure of the pentacene films provided a reasonable explanation for the high performance using resonance micro-Raman spectroscopy.

  8. Technological Innovation of Thin-Film Transistors: Technology Development, History, and Future

    NASA Astrophysics Data System (ADS)

    Yamamoto, Yoshitaka

    2012-06-01

    The scale of the liquid crystal display industry has expanded rapidly, driven by technological innovations for thin-film transistors (TFTs). The TFT technology, which started from amorphous silicon (a-Si), has produced large TVs, and low-temperature polycrystalline silicon (poly-Si) has become a core technology for small displays, such as mobile phones. Recently, various TFT technological seeds have been realized, indicating that new information appliances that match new lifestyles and information infrastructures will be available in the near future. In this article, I review the history of TFT technology and discuss the future of TFT technological development from the technological innovation viewpoint.

  9. Critical invisible defect detection system of thin film transistor panels using Kelvin probe force microscopy

    NASA Astrophysics Data System (ADS)

    Park, Yonmook; Heo, Keun

    2016-07-01

    In this paper, a novel method that can perform measurements of the contact potential difference (CPD) between a tip and a thin film transistor (TFT) panel using the Kelvin probe force microscopy (KPFM) is proposed for inspection of critical invisible defects on TFT panels. In this application, the surface potential of a TFT panel is inferred from the electrostatic interaction force between a tip and a TFT panel induced by the electric field. The experimental results are given to illustrate that the KPFM provides a novel and feasible way to detect the most critical invisible defects on TFT panels.

  10. Ambipolar organic thin-film transistor-based nano-floating-gate nonvolatile memory

    SciTech Connect

    Han, Jinhua; Wang, Wei Ying, Jun; Xie, Wenfa

    2014-01-06

    An ambipolar organic thin-film transistor-based nano-floating-gate nonvolatile memory was demonstrated, with discrete distributed gold nanoparticles, tetratetracontane (TTC), pentacene as the floating-gate layer, tunneling layer, and active layer, respectively. The electron traps at the TTC/pentacene interface were significantly suppressed, which resulted in an ambipolar operation in present memory. As both electrons and holes were supplied in the channel and trapped in the floating-gate by programming/erasing operations, respectively, i.e., one type of charge carriers was used to overwrite the other, trapped, one, a large memory window, extending on both sides of the initial threshold voltage, was realized.

  11. Investigation of Nonvolatile Memory Effect of Organic Thin-Film Transistors with Triple Dielectric Layers

    NASA Astrophysics Data System (ADS)

    Yu, Hsin-Chieh; Chen, Ying-Chih; Huang, Chun-Yuan; Su, Yan-Kuin

    2012-03-01

    Pentacene thin-film transistor (TFT) memory using poly(2-hydroxyethyl methacrylate) (PHEMA)-based polymer dielectric layers has been developed. The electric performance and memory behaviors of memory TFTs can be significantly improved by using triple polymer dielectric layers consisting of PHEMA/poly(methyl methacrylate) (PMMA)/PHEMA. This can be attributed to the improvement of the channel/dielectric interface. This memory effect is due to the charge storage of the dipolar group or molecules in the dielectric. The devices exhibit a wide memory window (ΔVth, >20 V), switchable channel current, and long retention time.

  12. Electrochromism Properties of Palladium Doped Tungsten-Oxide Thin Films Prepared with RF Reactive Sputtering

    NASA Astrophysics Data System (ADS)

    Yabumoto, Taihei; Iwai, Yuki; Miura, Noboru; Matsumoto, Setsuko; Nakano, Ryotaro; Matsumoto, Hironaga

    Palladium doped tungsten oxide thin films were prepared by RF reactive sputtering in a mixture of argon and oxygen at room temperature. XRD patterns indicated that these films were amorphous. SEM imaging indicated a smaller grain size of palladium doped thin film compared with that of undoped tungsten oxide thin film. With electrochromism, palladium doped tungsten oxide exhibited a reverse optical modulation with respect to the applied potential.

  13. Enhanced Performance Consistency in Nanoparticle/TIPS Pentacene-Based Organic Thin Film Transistors

    SciTech Connect

    He, Zhengran; Xiao, Kai; Durant, William Mark; Anthony, John E.; Kilbey, II, S Michael; Chen, Jihua; Li, Dawen

    2011-01-01

    In this study, inorganic silica nanoparticles are used to manipulate the morphology of 6,13-bis(triisopropylsilylethynyl)-pentacene (TIPS pentacene) thin films and the performance of solution-processed organic thin-film transistors (OTFTs). This approach is taken to control crystal anisotropy, which is the origin of poor consistency in TIPS pentacene based OTFT devices. Thin film active layers are produced by drop-casting mixtures of SiO{sub 2} nanoparticles and TIPS pentacene. The resultant drop-cast films yield improved morphological uniformity at {approx}10% SiO{sub 2} loading, which also leads to a 3-fold increase in average mobility and nearly 4 times reduction in the ratio of measured mobility standard deviation ({mu}{sub Stdev}) to average mobility ({mu}{sub Avg}). Grazing-incidence X-ray diffraction, scanning and transmission electron microscopy as well as polarized optical microscopy are used to investigate the nanoparticle-mediated TIPS pentacene crystallization. The experimental results suggest that the SiO{sub 2} nanoparticles mostly aggregate at TIPS pentacene grain boundaries, and 10% nanoparticle concentration effectively reduces the undesirable crystal misorientation without considerably compromising TIPS pentacene crystallinity.

  14. Fabrication of high performance thin-film transistors via pressure-induced nucleation

    PubMed Central

    Kang, Myung-Koo; Kim, Si Joon; Kim, Hyun Jae

    2014-01-01

    We report a method to improve the performance of polycrystalline Si (poly-Si) thin-film transistors (TFTs) via pressure-induced nucleation (PIN). During the PIN process, spatial variation in the local solidification temperature occurs because of a non-uniform pressure distribution during laser irradiation of the amorphous Si layer, which is capped with an SiO2 layer. This leads to a four-fold increase in the grain size of the poly-Si thin-films formed using the PIN process, compared with those formed using conventional excimer laser annealing. We find that thin films with optimal electrical properties can be achieved with a reduction in the number of laser irradiations from 20 to 6, as well as the preservation of the interface between the poly-Si and the SiO2 gate insulator. This interface preservation becomes possible to remove the cleaning process prior to gate insulator deposition, and we report devices with a field-effect mobility greater than 160 cm2/Vs. PMID:25358809

  15. Grain Boundary Induced Bias Instability in Soluble Acene-Based Thin-Film Transistors.

    PubMed

    Nguyen, Ky V; Payne, Marcia M; Anthony, John E; Lee, Jung Hun; Song, Eunjoo; Kang, Boseok; Cho, Kilwon; Lee, Wi Hyoung

    2016-01-01

    Since the grain boundaries (GBs) within the semiconductor layer of organic field-effect transistors (OFETs) have a strong influence on device performance, a substantial number of studies have been devoted to controlling the crystallization characteristics of organic semiconductors. We studied the intrinsic effects of GBs within 5,11-bis(triethylsilylethynyl) anthradithiophene (TES-ADT) thin films on the electrical properties of OFETs. The GB density was easily changed by controlling nulceation event in TES-ADT thin films. When the mixing time was increased, the number of aggregates in as-spun TES-ADT thin films were increased and subsequent exposure of the films to 1,2-dichloroethane vapor led to a significant increase in the number of nuleation sites, thereby increasing the GB density of TES-ADT spherulites. The density of GBs strongly influences the angular spread and crystallographic orientation of TES-ADT spherulites. Accordingly, the FETs with higher GB densities showed much poorer electrical characteristics than devices with lower GB density. Especially, GBs provide charge trapping sites which are responsible for bias-stress driven electrical instability. Dielectric surface treatment with a polystyrene brush layer clarified the GB-induced charge trapping by reducing charge trapping at the semiconductor-dielectric interface. Our study provides an understanding on GB induced bias instability for the development of high performance OFETs. PMID:27615358

  16. Controlling the dimensionality of charge transport in organic thin-film transistors

    PubMed Central

    Laiho, Ari; Herlogsson, Lars; Forchheimer, Robert; Crispin, Xavier; Berggren, Magnus

    2011-01-01

    Electrolyte-gated organic thin-film transistors (OTFTs) can offer a feasible platform for future flexible, large-area and low-cost electronic applications. These transistors can be divided into two groups on the basis of their operation mechanism: (i) field-effect transistors that switch fast but carry much less current than (ii) the electrochemical transistors which, on the contrary, switch slowly. An attractive approach would be to combine the benefits of the field-effect and the electrochemical transistors into one transistor that would both switch fast and carry high current densities. Here we report the development of a polyelectrolyte-gated OTFT based on conjugated polyelectrolytes, and we demonstrate that the OTFTs can be controllably operated either in the field-effect or the electrochemical regime. Moreover, we show that the extent of electrochemical doping can be restricted to a few monolayers of the conjugated polyelectrolyte film, which allows both high current densities and fast switching speeds at the same time. We propose an operation mechanism based on self-doping of the conjugated polyelectrolyte backbone by its ionic side groups. PMID:21876143

  17. Electrical and Optical Properties of Copper Oxide Thin Films by Sol-Gel Technique

    NASA Astrophysics Data System (ADS)

    Hashim, H.; Shariffudin, S. S.; Saad, P. S. M.; Ridah, H. A. M.

    2015-11-01

    Copper oxide were prepared by sol-gel technique and deposited onto quartz substrates as thin films using spin coating method. The aim of this research was to study the effects of different spin coating speeds of copper oxide thin films on the electrical and optical properties of the thin films. Five samples of copper oxide thin films with different spin coating speeds of 1000, 1500, 2000, 2500 and 3000 rpm were annealed at 600°C for 30 minutes. UV-Vis spectrophotometer and two-point probe technique were used to characterize the optical and electrical properties of the deposited films. Based on the results obtained, it revealed that the electrical conductivity of the copper oxide thin films reduce as the spin coating speeds increase. The calculated optical band gap and the resistivity of the copper oxide thin films also decrease when the spin coating speeds are increased.

  18. Bismuth ferrite based thin films, nanofibers, and field effect transistor devices

    NASA Astrophysics Data System (ADS)

    Rivera-Beltran, Rut

    In this research an attempt has been made to explore bismuth ferrite thin films with low leakage current and nanofibers with high photoconductivity. Thin films were deposited with pulsed laser deposition (PLD) method. An attempt has been made to develop thin films under different deposition parameters with following target compositions: i) 0.6BiFeO3-0.4(Bi0.5 K0.5)TiO3 (BFO-BKT) and ii) bi-layered 0.88Bi 0.5Na0.5TiO3-0.08Bi0.5K0.5TiO 3-0.04BaTiO3/BiFeO3 (BNT-BKT-BT/BFO). BFO-BKT thin film shows suppressed leakage current by about four orders of magnitude which in turn improve the ferroelectric and dielectric properties of the films. The optimum remnant polarization is 19 muC.cm-2 at the oxygen partial pressure of 300 mtorr. The BNT-BKT-BT/BFO bi-layered thin films exhibited ferroelectric behavior as: Pr = 22.0 muC.cm-2, Ec = 100 kV.cm-1 and epsilonr = 140. The leakage current of bi-layered thin films have been reduced two orders of magnitude compare to un-doped bismuth ferrite. Bismuth ferrite nanofibers were developed by electrospinning technique and its electronic properties such as photoconductivity and field effect transistor performance were investigated extensively. Nanofibers were deposited by electrospinning of sol-gel solution on SiO2/Si substrate at driving voltage of 10 kV followed by heat treatment at 550 °C for 2 hours. The composition analysis through energy dispersive detector and electron energy loss spectroscopy revealed the heterogeneous nature of the composition with Bi rich and Fe deficient regions. X-ray photoelectron spectroscopy results confirmed the combination of Fe3+ and Fe2+ valence state in the fibers. The photoresponse result is almost hundred times higher for a fiber of 40 nm diameter compared to a fiber with 100 nm diameter. This effect is described by a size dependent surface recombination mechanism. A single and multiple BFO nanofibers field effect transistors devices were fabricated and characterized. Bismuth ferrite FET behaves

  19. Towards solution-processed ambipolar hybrid thin-film transistors based on ZnO nanoparticles and P3HT polymer

    NASA Astrophysics Data System (ADS)

    Diallo, Abdou Karim; Gaceur, Meriem; Berton, Nicolas; Margeat, Olivier; Ackermann, Jörg; Videlot-Ackermann, Christine

    2013-06-01

    Solution-processed n-channel oxide semiconductor thin-film transistors (TFTs) were fabricated using zinc oxide (ZnO) nanoparticles. Polycrystalline fused-ZnO nanoparticle films were produced by spin-coating ZnO nanosphere dispersions following by a subsequent heat treatment. The solution-processable semiconductor ink based on ZnO was prepared by dispersing the synthesized ZnO nanospheres in isopropanol mixed with ethanolamine to various concentrations from 20 to 80 mg/mL. Such concentration dependence on morphology and microstructure of thin films was studied on spin-coated ZnO films by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Spin-coated ZnO films involved as active layers in transistor configuration delivered an almost ideal output characteristic (Id-Vd) with an electron mobility up to 3 × 10-2 cm2/V s. As a p-channel semiconductor, a poly(3-hexylthiophene) (P3HT) solution-processable ink was deposited by spin-coating on top of closely packed ZnO nanoparticles-based films to form an uniform overlying layer. A hybrid (inorganic-organic) interface was formed by the direct contact between ZnO and P3HT leading to carrier redistribution. Such solution-processed hybrid thin-film transistors delivered in air well balanced electron and hole mobilities as 3.9 × 10-5 and 2 × 10-5 cm2/V s, respectively.

  20. The Integration and Applications of Organic Thin Film Transistors and Ferroelectric Polymers

    NASA Astrophysics Data System (ADS)

    Hsu, Yu-Jen

    Organic thin film transistors and ferroelectric polymer (polyvinylidene difluoride) sheet material are integrated to form various sensors for stress/strain, acoustic wave, and Infrared (heat) sensing applications. Different from silicon-based transistors, organic thin film transistors can be fabricated and processed in room-temperature and integrated with a variety of substrates. On the other hand, polyvinylidene difluoride (PVDF) exhibits ferroelectric properties that are highly useful for sensor applications. The wide frequency bandwidth (0.001 Hz to 10 GHz), vast dynamic range (100n to 10M psi), and high elastic compliance (up to 3 percent) make PVDF a more suitable candidate over ceramic piezoelectric materials for thin and flexible sensor applications. However, the low Curie temperature may have impeded its integration with silicon technology. Organic thin film transistors, however, do not have the limitation of processing temperature, hence can serve as transimpedance amplifiers to convert the charge signal generated by PVDF into current signal that are more measurable and less affected by any downstream parasitics. Piezoelectric sensors are useful for a range of applications, but passive arrays suffer from crosstalk and signal attenuation which have complicated the development of array-based PVDF sensors. We have used organic field effect transistors, which are compatible with the low Curie temperature of a flexible piezoelectric polymer,PVDF, to monolithically fabricate transimpedance amplifiers directly on the sensor surface and convert the piezoelectric charge signal into a current signal which can be detected even in the presence of parasitic capacitances. The device couples the voltage generated by the PVDF film under strain into the gate of the organic thin film transistors (OFET) using an arrangement that allows the full piezoelectric voltage to couple to the channel, while also increasing the charge retention time. A bipolar detector is created by

  1. Hafnium carbide formation in oxygen deficient hafnium oxide thin films

    NASA Astrophysics Data System (ADS)

    Rodenbücher, C.; Hildebrandt, E.; Szot, K.; Sharath, S. U.; Kurian, J.; Komissinskiy, P.; Breuer, U.; Waser, R.; Alff, L.

    2016-06-01

    On highly oxygen deficient thin films of hafnium oxide (hafnia, HfO2-x) contaminated with adsorbates of carbon oxides, the formation of hafnium carbide (HfCx) at the surface during vacuum annealing at temperatures as low as 600 °C is reported. Using X-ray photoelectron spectroscopy the evolution of the HfCx surface layer related to a transformation from insulating into metallic state is monitored in situ. In contrast, for fully stoichiometric HfO2 thin films prepared and measured under identical conditions, the formation of HfCx was not detectable suggesting that the enhanced adsorption of carbon oxides on oxygen deficient films provides a carbon source for the carbide formation. This shows that a high concentration of oxygen vacancies in carbon contaminated hafnia lowers considerably the formation energy of hafnium carbide. Thus, the presence of a sufficient amount of residual carbon in resistive random access memory devices might lead to a similar carbide formation within the conducting filaments due to Joule heating.

  2. Linking Precursor Alterations to Nanoscale Structure and Optical Transparency in Polymer Assisted Fast-Rate Dip-Coating of Vanadium Oxide Thin Films

    PubMed Central

    Glynn, Colm; Creedon, Donal; Geaney, Hugh; Armstrong, Eileen; Collins, Timothy; Morris, Michael A.; Dwyer, Colm O’

    2015-01-01

    Solution processed metal oxide thin films are important for modern optoelectronic devices ranging from thin film transistors to photovoltaics and for functional optical coatings. Solution processed techniques such as dip-coating, allow thin films to be rapidly deposited over a large range of surfaces including curved, flexible or plastic substrates without extensive processing of comparative vapour or physical deposition methods. To increase the effectiveness and versatility of dip-coated thin films, alterations to commonly used precursors can be made that facilitate controlled thin film deposition. The effects of polymer assisted deposition and changes in solvent-alkoxide dilution on the morphology, structure, optoelectronic properties and crystallinity of vanadium pentoxide thin films was studied using a dip-coating method using a substrate withdrawal speed within the fast-rate draining regime. The formation of sub-100 nm thin films could be achieved rapidly from dilute alkoxide based precursor solutions with high optical transmission in the visible, linked to the phase and film structure. The effects of the polymer addition was shown to change the crystallized vanadium pentoxide thin films from a granular surface structure to a polycrystalline structure composed of a high density of smaller in-plane grains, resulting in a uniform surface morphology with lower thickness and roughness. PMID:26123117

  3. Influence of underneath pentacene thickness on performance of p-n heterojunction organic thin film transistors

    NASA Astrophysics Data System (ADS)

    Zhou, Jianlin; Jiang, Yuyu; Wang, Zhen; Hu, Shengdong; Gan, Ping; Shen, Xiaoqing

    2016-02-01

    Organic thin film transistors (OTFTs) with heterojunction semiconducting layers composed of p-type pentacene and n-type fluorinated copper phthalocyanine (F16CuPc) have been fabricated. The influence of pentacene film thickness on performance of transistors is carefully investigated. It has been found that, with the increase of pentacene film thickness, the electron mobility increases at first and then decreases intensely. But the shift of VT is opposite comparing with electron mobility. The performance improvement can be attributed to the increase of free electron carriers by band bending at the pentacene/F16CuPc interface, and better F16CuPc film quality grown upon pentacene. Comparing with island growth-mode, layer-by-layer growth-mode of pentacene facilitates the growth of the upper F16CuPc film.

  4. Memory operation devices based on light-illumination ambipolar carbon-nanotube thin-film-transistors

    SciTech Connect

    Aïssa, B.; Nedil, M.; Kroeger, J.; Haddad, T.; Rosei, F.

    2015-09-28

    We report the memory operation behavior of a light illumination ambipolar single-walled carbon nanotube thin film field-effect transistors devices. In addition to the high electronic-performance, such an on/off transistor-switching ratio of 10{sup 4} and an on-conductance of 18 μS, these memory devices have shown a high retention time of both hole and electron-trapping modes, reaching 2.8 × 10{sup 4} s at room temperature. The memory characteristics confirm that light illumination and electrical field can act as an independent programming/erasing operation method. This could be a fundamental step toward achieving high performance and stable operating nanoelectronic memory devices.

  5. Transparent ambipolar organic thin film transistors based on multilayer transparent source-drain electrodes

    NASA Astrophysics Data System (ADS)

    Zhang, Nan; Hu, Yongsheng; Lin, Jie; Li, Yantao; Liu, Xingyuan

    2016-08-01

    A fabrication method for transparent ambipolar organic thin film transistors with transparent Sb2O3/Ag/Sb2O3 (SAS) source and drain electrodes has been developed. A pentacene/N,N'-ditridecylperylene-3,4,9,10-tetracarboxylic di-imide (PTCDI-C13) bilayer heterojunction is used as the active semiconductor. The electrodes are deposited by room temperature electron beam evaporation. The devices are fabricated without damaging the active layers. The SAS electrodes have high transmittance (82.5%) and low sheet resistance (8 Ω/sq). High performance devices with hole and electron mobilities of 0.3 cm2/V s and 0.027 cm2/V s, respectively, and average visible range transmittance of 72% were obtained. These transistors have potential for transparent logic integrated circuit applications.

  6. Combustion-process derived comparable performances of Zn-(In:Sn)-O thin-film transistors with a complete miscibility

    SciTech Connect

    Jiang, Qingjun; Lu, Jianguo Cheng, Jipeng; Sun, Rujie; Feng, Lisha; Dai, Wen; Yan, Weichao; Ye, Zhizhen; Li, Xifeng

    2014-09-29

    Amorphous zinc-indium-tin oxide (a-ZITO) thin-film transistors (TFTs) have been prepared using a low-temperature combustion process, with an emphasis on complete miscibility of In and Sn contents. The a-ZITO TFTs were comparatively studied in detail, especially for the working stability. The a-ZITO TFTs all exhibited acceptable and excellent behaviors from Sn-free TFTs to In-free TFTs. The obtained a-ZTO TFTs presented a field-effect mobility of 1.20 cm{sup 2} V{sup −1} s{sup −1}, an on/off current ratio of 4.89 × 10{sup 6}, and a long-term stability under positive bias stress, which are comparable with those of the a-ZIO TFTs. The In-free a-ZTO TFTs are very potential for electrical applications with a low cost.

  7. Thickness dependent low-frequency noise characteristics of a-InZnO thin-film transistors under light illumination

    SciTech Connect

    Choi, Hyun-Sik; Jeon, Sanghun

    2014-01-13

    The influence of illumination on the electrical characteristics of amorphous indium–zinc oxide (a-IZO) thin-film transistors (TFTs) has been investigated. The electrical properties are found to depend significantly on the active thickness (T{sub IZO}) of the a-IZO TFT. The active thickness is seen to play a major role in the carrier transport mechanism. Based on the carrier fluctuation model, the low-frequency noise (LFN) characteristics of a-IZO devices of varying thicknesses were evaluated before as well as after illumination. Similar to the results of DC and capacitance–voltage (C–V) measurements, the LFN characteristics too show that the light-induced carrier transport becomes significantly enhanced for relatively thick (T{sub IZO} ≥ 60 nm) a-IZO devices.

  8. Subgap states in p-channel tin monoxide thin-film transistors from temperature-dependent field-effect characteristics

    NASA Astrophysics Data System (ADS)

    Jeong, Chan-Yong; Lee, Daeun; Han, Young-Joon; Choi, Yong-Jin; Kwon, Hyuck-In

    2015-08-01

    This paper experimentally investigates the subgap density of states (DOS) in p-type tin monoxide (SnO) thin-film transistors (TFTs) for the first time by using temperature-dependent field-effect measurements. As the temperature increases, the turn-on voltage moves in the positive direction, and the off-current and subthreshold slope continuously increase. We found that the conductivity of the SnO TFT obeys the Meyer-Neldel (MN) rule with a characteristic MN parameter of 28.6 eV-1 in the subthreshold region, from which we successfully extracted the subgap DOS by combing the field-effect method and the MN relation. The extracted subgap DOS from fabricated p-type SnO TFTs are exponentially distributed in energy, and exhibit around two orders of magnitude higher values compared to those of the n-type amorphous indium-gallium-zinc oxide TFTs.

  9. Effect of etching stop layer on characteristics of amorphous IGZO thin film transistor fabricated at low temperature

    NASA Astrophysics Data System (ADS)

    Li, Xifeng; Xin, Enlong; Chen, Longlong; Shi, Jifeng; Zhang, Jianhua

    2013-03-01

    Transparent bottom-gate amorphous Indium-Gallium-Zinc Oxide (a-IGZO) thin-film transistors (TFTs) had been successfully fabricated at relative low temperature. The influence of reaction gas ratio of N2O and SiH4 during the growth of etching stop layer (SiOx) on the characteristics of a-IGZO TFTs was investigated. The transfer characteristics of the TFTs were changed markedly because active layer of a-IGZO films was modified by plasma in the growth process of SiOx. By optimizing the deposition parameters of etching stop layer process, a-IGZO TFTs were manufactured and exhibited good performance with a field-effect mobility of 8.5 cm2V-1s-1, a threshold voltage of 1.3 V, and good stability under gate bias stress of 20 V for 10000 s.

  10. The effect of Ta doping in polycrystalline TiO{sub x} and the associated thin film transistor properties

    SciTech Connect

    Ok, Kyung-Chul Park, Yoseb Park, Jin-Seong E-mail: jsparklime@hanyang.ac.kr; Chung, Kwun-Bum E-mail: jsparklime@hanyang.ac.kr

    2013-11-18

    Tantalum (Ta) is suggested to act as an electron donor and crystal phase stabilizer in titanium oxide (TiO{sub x}). A transition occurs from an amorphous state to a crystalline phase at an annealing temperature above 300 °C in a vacuum ambient. As the annealing temperature increases from 300 °C to 450 °C, the mobility increases drastically from 0.07 cm{sup 2}/Vs to 0.61 cm{sup 2}/Vs. The remarkable enhancement of thin film transistor performance is suggested to be due to the splitting of Ti 3d band orbitals as well as the increase in Ta{sup 5+} ions that can act as electron donors.

  11. Conducting glasses recovered from thin film transistor liquid crystal display wastes for dye-sensitized solar cell cathodes.

    PubMed

    Chen, C-C; Chang, F-C; Peng, C Y; Wang, H Paul

    2015-01-01

    Transparent conductive glasses such as thin film transistor (TFT) array and colour filter glasses were recovered from the TFT-liquid crystal display panel wastes by dismantling and sonic cleaning. Noble metals (i.e. platinum (Pt)) and indium tin oxide (ITO) are generally used in the cathode of a dye-sensitized solar cell (DSSC). To reduce the DSSC cost, Pt was replaced with nano nickel-encapsulated carbon-shell (Ni@C) nanoparticles, which were prepared by carbonization of Ni²⁺-β-cyclodextrin at 673 K for 2 h. The recovered conductive glasses were used in the DSSC electrodes in the substitution of relatively expensive ITO. Interestingly, the efficiency of the DSSC having the Ni@C-coated cathode is as high as 2.54%. Moreover, the cost of the DSSC using the recovered materials can be reduced by at least 24%. PMID:25399759

  12. Effects of Li doping on the performance and environmental stability of solution processed ZnO thin film transistors

    NASA Astrophysics Data System (ADS)

    Nayak, Pradipta K.; Jang, Jongsu; Lee, Changhee; Hong, Yongtaek

    2009-11-01

    We report the effects of lithium (Li) doping on the performance and environmental stability of solution processed zinc oxide (ZnO) thin film transistors (TFTs). It was found that appropriate amount of Li doping significantly reduced the background conductivity of ZnO films and also improved the orientation of ZnO crystallites along the c-axis. A highest field-effect mobility of 3.07 cm2/V s was found for the 5 at. % Li-doped ZnO TFTs. However, 15 and 25 at. % Li-doped ZnO TFTs showed good environmental stability of Ion/Ioff ratio with reasonable field-effect mobility.

  13. Improved AMOLED with aligned poly-Si thin-film transistors by laser annealing and chemical solution treatments

    NASA Astrophysics Data System (ADS)

    Wu, G. M.; Chen, C. N.; Feng, W. S.; Lu, H. C.

    2009-12-01

    Low-temperature polycrystalline silicon (LTPS) thin-film transistors (TFT) were prepared for the active-matrix organic light-emitting displays (AMOLED). The excimer laser annealing (ELA) recrystallization technique was employed with a chemical solution treatment process to improve the TFT characteristic uniformity and the AMOLED display image quality. The characteristics of the poly-Si array thin films were influenced by XeCl ELA optic module design, TFT device channel direction, and laser irradiation overlap ratio. The ELA system module provided aligned poly-Si grain size of 0.3 μm by the homogenization lens design. The chemical solution treatment process included a dilute HF solution (DHF), ozone (O 3) water, and buffer oxide etching solution (BOE). The PMOS TFT showed better field effect mobility of 87.6 cm 2/V s, and the threshold voltage was -1.35 V. The off current ( Ioff) was 1.25×10 -11 A, and the on/off current ratio was 6.27×10 6. In addition, the image quality of the AMOLED display was highly improved using the 2T1C structure design without any compensation circuit.

  14. 7-Octenyltrichrolosilane/trimethyaluminum hybrid dielectrics fabricated by molecular-atomic layer deposition on ZnO thin film transistors

    NASA Astrophysics Data System (ADS)

    Huang, Jie; Lee, Mingun; Lucero, Antonio T.; Cheng, Lanxia; Ha, Min-Woo; Kim, Jiyoung

    2016-06-01

    We demonstrate the fabrication of 7-octenytrichlorosilane (7-OTS)/trimethylaluminum (TMA) organic–inorganic hybrid films using molecular-atomic layer deposition (MALD). The properties of 7-OTS/TMA hybrid films are extensively investigated using transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), and electrical measurements. Our results suggest that uniform and smooth amorphous hybrid thin films with excellent insulating properties are obtained using the MALD process. Films have a relatively high dielectric constant of approximately 5.0 and low leakage current density. We fabricate zinc oxide (ZnO) based thin film transistors (TFTs) using 7-OTS/TMA hybrid material as a back gate dielectric with the top ZnO channel layer deposited in-situ via MALD. The ZnO TFTs exhibit a field effect mobility of approximately 0.43 cm2 V‑1 s‑1, a threshold voltage of approximately 1 V, and an on/off ratio of approximately 103 under low voltage operation (from ‑3 to 9 V). This work demonstrates an organic–inorganic hybrid gate dielectric material potentially useful in flexible electronics application.

  15. Rational Design of ZnO:H/ZnO Bilayer Structure for High-Performance Thin-Film Transistors.

    PubMed

    Abliz, Ablat; Huang, Chun-Wei; Wang, Jingli; Xu, Lei; Liao, Lei; Xiao, Xiangheng; Wu, Wen-Wei; Fan, Zhiyong; Jiang, Changzhong; Li, Jinchai; Guo, Shishang; Liu, Chuansheng; Guo, Tailiang

    2016-03-01

    The intriguing properties of zinc oxide-based semiconductors are being extensively studied as they are attractive alternatives to current silicon-based semiconductors for applications in transparent and flexible electronics. Although they have promising properties, significant improvements on performance and electrical reliability of ZnO-based thin film transistors (TFTs) should be achieved before they can be applied widely in practical applications. This work demonstrates a rational and elegant design of TFT, composed of poly crystalline ZnO:H/ZnO bilayer structure without using other metal elements for doping. The field-effect mobility and gate bias stability of the bilayer structured devices have been improved. In this device structure, the hydrogenated ultrathin ZnO:H active layer (∼3 nm) could provide suitable carrier concentration and decrease the interface trap density, while thick pure-ZnO layer could control channel conductance. Based on this novel structure, a high field-effect mobility of 42.6 cm(2) V(-1) s(-1), a high on/off current ratio of 10(8) and a small subthreshold swing of 0.13 V dec(-1) have been achieved. Additionally, the bias stress stability of the bilayer structured devices is enhanced compared to the simple single channel layer ZnO device. These results suggest that the bilayer ZnO:H/ZnO TFTs have a great potential for low-cost thin-film electronics. PMID:26977526

  16. Oxidation Effects in Rare Earth Doped Topological Insulator Thin Films.

    PubMed

    Figueroa, A I; van der Laan, G; Harrison, S E; Cibin, G; Hesjedal, T

    2016-01-01

    The breaking of time-reversal symmetry (TRS) in topological insulators is a prerequisite for unlocking their exotic properties and for observing the quantum anomalous Hall effect (QAHE). The incorporation of dopants which exhibit magnetic long-range order is the most promising approach for TRS-breaking. REBiTe3, wherein 50% of the Bi is substitutionally replaced by a RE atom (RE = Gd, Dy, and Ho), is a predicted QAHE system. Despite the low solubility of REs in bulk crystals of a few %, highly doped thin films have been demonstrated, which are free of secondary phases and of high crystalline quality. Here we study the effects of exposure to atmosphere of rare earth-doped Bi2(Se, Te)3 thin films using x-ray absorption spectroscopy. We demonstrate that these RE dopants are all trivalent and effectively substitute for Bi(3+) in the Bi2(Se, Te)3 matrix. We find an unexpected high degree of sample oxidation for the most highly doped samples, which is not restricted to the surface of the films. In the low-doping limit, the RE-doped films mostly show surface oxidation, which can be prevented by surface passivation, encapsulation, or in-situ cleaving to recover the topological surface state. PMID:26956771

  17. Oxidation Effects in Rare Earth Doped Topological Insulator Thin Films

    PubMed Central

    Figueroa, A. I.; van der Laan, G.; Harrison, S. E.; Cibin, G.; Hesjedal, T.

    2016-01-01

    The breaking of time-reversal symmetry (TRS) in topological insulators is a prerequisite for unlocking their exotic properties and for observing the quantum anomalous Hall effect (QAHE). The incorporation of dopants which exhibit magnetic long-range order is the most promising approach for TRS-breaking. REBiTe3, wherein 50% of the Bi is substitutionally replaced by a RE atom (RE = Gd, Dy, and Ho), is a predicted QAHE system. Despite the low solubility of REs in bulk crystals of a few %, highly doped thin films have been demonstrated, which are free of secondary phases and of high crystalline quality. Here we study the effects of exposure to atmosphere of rare earth-doped Bi2(Se, Te)3 thin films using x-ray absorption spectroscopy. We demonstrate that these RE dopants are all trivalent and effectively substitute for Bi3+ in the Bi2(Se, Te)3 matrix. We find an unexpected high degree of sample oxidation for the most highly doped samples, which is not restricted to the surface of the films. In the low-doping limit, the RE-doped films mostly show surface oxidation, which can be prevented by surface passivation, encapsulation, or in-situ cleaving to recover the topological surface state. PMID:26956771

  18. Oxidation Effects in Rare Earth Doped Topological Insulator Thin Films

    NASA Astrophysics Data System (ADS)

    Figueroa, A. I.; van der Laan, G.; Harrison, S. E.; Cibin, G.; Hesjedal, T.

    2016-03-01

    The breaking of time-reversal symmetry (TRS) in topological insulators is a prerequisite for unlocking their exotic properties and for observing the quantum anomalous Hall effect (QAHE). The incorporation of dopants which exhibit magnetic long-range order is the most promising approach for TRS-breaking. REBiTe3, wherein 50% of the Bi is substitutionally replaced by a RE atom (RE = Gd, Dy, and Ho), is a predicted QAHE system. Despite the low solubility of REs in bulk crystals of a few %, highly doped thin films have been demonstrated, which are free of secondary phases and of high crystalline quality. Here we study the effects of exposure to atmosphere of rare earth-doped Bi2(Se, Te)3 thin films using x-ray absorption spectroscopy. We demonstrate that these RE dopants are all trivalent and effectively substitute for Bi3+ in the Bi2(Se, Te)3 matrix. We find an unexpected high degree of sample oxidation for the most highly doped samples, which is not restricted to the surface of the films. In the low-doping limit, the RE-doped films mostly show surface oxidation, which can be prevented by surface passivation, encapsulation, or in-situ cleaving to recover the topological surface state.

  19. Thin film bismuth iron oxides useful for piezoelectric devices

    DOEpatents

    Zeches, Robert J.; Martin, Lane W.; Ramesh, Ramamoorthy

    2016-05-31

    The present invention provides for a composition comprising a thin film of BiFeO.sub.3 having a thickness ranging from 20 nm to 300 nm, a first electrode in contact with the BiFeO.sub.3 thin film, and a second electrode in contact with the BiFeO.sub.3 thin film; wherein the first and second electrodes are in electrical communication. The composition is free or essentially free of lead (Pb). The BFO thin film is has the piezoelectric property of changing its volume and/or shape when an electric field is applied to the BFO thin film.

  20. Fabrication of water-stable organic transistors using crystalline rubrene thin-film and polymer-treated dielectric (Presentation Recording)

    NASA Astrophysics Data System (ADS)

    Kim, Jaejoon; Lee, Hyoek Moo; Cho, Sung Oh

    2015-10-01

    For the real application of organic electronics, stable operation of electronic devices in humid or aqueous condition is essential and desirable. However, most of organic semiconductors were very weak to the oxygen or water and especially, cannot be operated well in aqueous condition without an encapsulation. Here, we present water-stable organic thin-film transistors with highly crystallized rubrene and polymer-treated dielectrics. These high water-stability could be achieved by two factors. First, rubrene, a well-known p-type semiconducting material, showed high air and water stability after the crystallization of `abrupt heating'. By the fabrication and aqueous operation of rubrene thin film transistor, we could show the water stability of crystallized thin-film rubrene. Such high environmental stability is attributed to the fact that rubrene has comparatively low HOMO level of -5.4 eV and large bandgap energy of 3.2 eV and that the rubrene thin-film is composed of well-interconnected orthorhombic rubrene crystals. Second, the polymer-treatment of dielectrics can enhance long-term water stability of fabricated rubrene thin-film transistor. By the complete immersion test of transistors, we could characterize the increase of water-stability after the treatment of dielectrics with cross-linked polymer. For this purpose, polystyrene is cross-linked by electron irradiation and the water penetration into semiconductor/dielectric interface was decreased due to the decreased surface energy of polymer dielectric compared to the SiO₂. The fabricated rubrene thin-film transistors showed a field-effect mobility of ~0.5 cm2V-1s-1 and long-term stability under ambient and aqueous conditions. Also, we investigated their potential applications in chemical or bio sensors.

  1. High-quality germanium dioxide thin films with low interface state density using a direct neutral beam oxidation process

    NASA Astrophysics Data System (ADS)

    Wada, Akira; Zhang, Rui; Takagi, Shinichi; Samukawa, Seiji

    2012-05-01

    High-quality germanium dioxide (GeO2) as a gate oxide is in high demand for use in future high mobility Ge-channel field-effect transistors. GeO2 thin films were directly formed by using a damage-free and low-temperature process of neutral beam oxidation (NBO) after treatment with hydrogen (H) radicals. GeO2 thin films (equivalent oxide thickness (EOT) = 1.7 nm) with a high-quality interface and an extremely low interface state density (<1 × 1011 cm-2 eV-1) could be formed even at low temperature (300 °C) by combining the H radical treatment, which resulted in the removal of native oxides, with the NBO process we developed.

  2. Electronic properties of organic thin film transistors with nanoscale tapered electrodes

    NASA Astrophysics Data System (ADS)

    Park, Jeongwon

    2008-10-01

    Organic thin-film transistors (OTFTs) have received increasing attention because of their potential applications in displays, optoelectronics, logic circuits, and sensors. Ultrathin OTFTs are of technical interest as a possible route toward reduced bias stress in standard OTFTs and enhanced sensitivity in chemical field-effect transistors (ChemFETs). ChemFETs are OTFTs whose output characteristics are sensitive to the presence of analytes via changes in the channel mobility and/or threshold voltage induced by analyte chemisorption onto the channel materials. The fundamental understanding of charge transport properties of organic thin-films is critical for the applications. OTFT has been demonstrated by many groups; however, there has been much less progress towards more reliable contact structure between organic materials and electrodes. This thesis investigates the electrical properties of metal phthalocyanine thin-film devices. In chapter 1, the basic electrical properties in OTFTs are reviewed. In chapter 2, we have investigated the microfabrication process of OTFTs to control the contact morphology and the charge transport properties of phthalocyanine thin-film devices. In chapter 3, the channel thickness dependence of the mobility was investigated in bottom-contact copper phthalocyanine (CuPc) OTFTs. The current-voltage characteristics of bottom contact CuPc OTFTs with low contact resistance fabricated by the bilayer photoresist lift-off process were analyzed to determine the mobility, threshold voltage and contact resistance. The independence of measured electronic properties from channel thickness is due to the contact resistance being negligible for all channel thicknesses. For practical applications, the aging and recovery process in CuPc OTFTs were investigated in chapter 4. An origin of the aging process on CuPc OTFTs has been investigated based on the responses of thick 1000ML CuPc OTFTs under a controlled atmosphere. The recovery process under 30

  3. Investigation of optical loss mechanisms in oxide thin films

    SciTech Connect

    Chow, A.F.; Kingon, A.I.; Auciello, O.; Poker, D.B.

    1995-05-01

    KNbO{sub 3}, K(Ta,Nb)O{sub 3}, KTaO{sub 3}, and Ta{sub 2}O{sub 5} thin films have been grown by ion-beam sputter deposition. KNbO{sub 3} has excellent nonlinear properties for second harmonic generation; however, high optical losses are still characteristic of these films. Several loss mechanisms, such as, high angle grain boundaries, twin domains, interface and surface scattering, and oxygen vacancies can all contribute to the high losses. In order to isolate the various mechanisms, amorphous Ta{sub 2}O{sub 5} films, epitaxial cubic KTaO{sub 3} and tetragonal K(Ta,Nb)O{sub 3} films were grown on MgO and Al{sub 2}O{sub 3} substrates subjected to post-deposition annealing treatments and various oxygen pressure conditions. The optical losses and refractive indices were observed to differ depending on the substrate surface and annealing treatments. Resonant scattering experiments were performed to analyze the oxygen composition. The optical properties of these oxide thin film systems are reported and the breakdown of the loss mechanisms is addressed.

  4. New fabrication of zinc oxide nanostructure thin film gas sensors

    NASA Astrophysics Data System (ADS)

    Hendi, A. A.; Alorainy, R. H.

    2014-02-01

    The copper doped zinc oxide thin films have been prepared by sol-gel spin coating method. The structural and morphology properties of the Cu doped films were characterized by X-ray diffraction and atomic force microscope. XRD studies confirm the chemical structure of the ZnO films. The optical spectra method were used to determined optical constants and dispersion energy parameters of Cu doped Zno thin films. The optical band gap of undoped ZnO was found to be 3.16 eV. The Eg values of the films were changed with Cu doping. The refractive index dispersion of Cu doped ZnO films obeys the single oscillator model. The dispersion energy and oscillator energy values of the ZnO films were changed with Cu doping. The Cu doped ZnO nanofiber-based NH3 gas sensors were fabricated. The sensor response of the sensors was from 464.98 to 484.61 when the concentration of NH3 is changed 6600-13,300 ppm. The obtained results indicate that the response of the ZnO film based ammonia gas sensors can be controlled by copper content.

  5. Wettability of oxide thin films prepared by pulsed laser deposition: New insights

    NASA Astrophysics Data System (ADS)

    Prakash, Saurav

    The objective of the thesis is to investigate the wettability of good quality oxide thin films prepared by pulsed laser deposition (PLD). In this work, many shortfalls in the water contact angle measurement of thin films of oxides, responsible for the wide scatter in the values reported in literature, have been addressed. (Abstract shortened by UMI.).

  6. Enhanced electrochromism in cerium doped molybdenum oxide thin films

    SciTech Connect

    Dhanasankar, M.; Purushothaman, K.K.; Muralidharan, G.

    2010-12-15

    Cerium (5-15% by weight) doped molybdenum oxide thin films have been prepared on FTO coated glass substrate at 250 {sup o}C using sol-gel dip coating method. The structural and morphological changes were observed with the help of XRD, SEM and EDS analysis. The amorphous structure of the Ce doped samples, favours easy intercalation and deintercalation processes. Mo oxide films with 10 wt.% of Ce exhibit maximum anodic diffusion coefficient of 24.99 x 10{sup -11} cm{sup 2}/s and the change in optical transmittance of ({Delta}T at 550 nm) of 79.28% between coloured and bleached state with the optical density of ({Delta}OD) 1.15.

  7. Nanoscale reduction of graphene oxide thin films and its characterization

    NASA Astrophysics Data System (ADS)

    Lorenzoni, M.; Giugni, A.; Di Fabrizio, E.; Pérez-Murano, Francesc; Mescola, A.; Torre, B.

    2015-07-01

    In this paper, we report on a method to reduce thin films of graphene oxide (GO) to a spatial resolution better than 100 nm over several tens of micrometers by means of an electrochemical scanning probe based lithography. In situ tip-current measurements show that an edged drop in electrical resistance characterizes the reduced areas, and that the reduction process is, to a good approximation, proportional to the applied bias between the onset voltage and the saturation thresholds. An atomic force microscope (AFM) quantifies the drop of the surface height for the reduced profile due to the loss of oxygen. Complementarily, lateral force microscopy reveals a homogeneous friction coefficient of the reduced regions that is remarkably lower than that of native graphene oxide, confirming a chemical change in the patterned region. Micro Raman spectroscopy, which provides access to insights into the chemical process, allows one to quantify the restoration and de-oxidation of the graphitic network driven by the electrochemical reduction and to determine characteristic length scales. It also confirms the homogeneity of the process over wide areas. The results shown were obtained from accurate analysis of the shift, intensity and width of Raman peaks for the main vibrational bands of GO and reduced graphene oxide (rGO) mapped over large areas. Concerning multilayered GO thin films obtained by drop-casting we have demonstrated an unprecedented lateral resolution in ambient conditions as well as an improved control, characterization and understanding of the reduction process occurring in GO randomly folded multilayers, useful for large-scale processing of graphene-based material.

  8. Printable ion-gel gate dielectrics for low-voltage polymer thin-film transistors on plastic.

    PubMed

    Cho, Jeong Ho; Lee, Jiyoul; Xia, Yu; Kim, BongSoo; He, Yiyong; Renn, Michael J; Lodge, Timothy P; Frisbie, C Daniel

    2008-11-01

    An important strategy for realizing flexible electronics is to use solution-processable materials that can be directly printed and integrated into high-performance electronic components on plastic. Although examples of functional inks based on metallic, semiconducting and insulating materials have been developed, enhanced printability and performance is still a challenge. Printable high-capacitance dielectrics that serve as gate insulators in organic thin-film transistors are a particular priority. Solid polymer electrolytes (a salt dissolved in a polymer matrix) have been investigated for this purpose, but they suffer from slow polarization response, limiting transistor speed to less than 100 Hz. Here, we demonstrate that an emerging class of polymer electrolytes known as ion gels can serve as printable, high-capacitance gate insulators in organic thin-film transistors. The specific capacitance exceeds that of conventional ceramic or polymeric gate dielectrics, enabling transistor operation at low voltages with kilohertz switching frequencies. PMID:18931674

  9. Improving Contact Interfaces in Fully Printed Carbon Nanotube Thin-Film Transistors.

    PubMed

    Cao, Changyong; Andrews, Joseph B; Kumar, Abhinay; Franklin, Aaron D

    2016-05-24

    Single-walled carbon nanotubes (CNTs) printed into thin films have been shown to yield high mobility, thermal conductivity, mechanical flexibility, and chemical stability as semiconducting channels in field-effect, thin-film transistors (TFTs). Printed CNT-TFTs of many varieties have been studied; however, there has been limited effort toward improving overall CNT-TFT performance. In particular, contact resistance plays a dominant role in determining the performance and degree of variability in the TFTs, especially in fully printed devices where the contacts and channel are both printed. In this work, we have systematically investigated the contact resistance and overall performance of fully printed CNT-TFTs employing three different printed contact materials-Ag nanoparticles, Au nanoparticles, and metallic CNTs-each in the following distinct contact geometries: top, bottom, and double. The active channel for each device was printed from the dispersion of high-purity (>99%) semiconducting CNTs, and all printing was carried out using an aerosol jet printer. Hundreds of devices with different channel lengths (from 20 to 500 μm) were fabricated for extracting contact resistance and determining related contact effects. Printed bottom contacts are shown to be advantageous compared to the more common top contacts, regardless of contact material. Further, compared to single (top or bottom) contacts, double contacts offer a significant decrease (>35%) in contact resistance for all types of contact materials, with the metallic CNTs yielding the best overall performance. These findings underscore the impact of printed contact materials and structures when interfacing with CNT thin films, providing key guidance for the further development of printed nanomaterial electronics. PMID:27097302

  10. Intrinsically stretchable and transparent thin-film transistors based on printable silver nanowires, carbon nanotubes and an elastomeric dielectric

    PubMed Central

    Liang, Jiajie; Li, Lu; Chen, Dustin; Hajagos, Tibor; Ren, Zhi; Chou, Shu-Yu; Hu, Wei; Pei, Qibing

    2015-01-01

    Thin-film field-effect transistor is a fundamental component behind various mordern electronics. The development of stretchable electronics poses fundamental challenges in developing new electronic materials for stretchable thin-film transistors that are mechanically compliant and solution processable. Here we report the fabrication of transparent thin-film transistors that behave like an elastomer film. The entire fabrication is carried out by solution-based techniques, and the resulting devices exhibit a mobility of ∼30 cm2 V−1 s−1, on/off ratio of 103–104, switching current >100 μA, transconductance >50 μS and relative low operating voltages. The devices can be stretched by up to 50% strain and subjected to 500 cycles of repeated stretching to 20% strain without significant loss in electrical property. The thin-film transistors are also used to drive organic light-emitting diodes. The approach and results represent an important progress toward the development of stretchable active-matrix displays. PMID:26173436

  11. Intrinsically stretchable and transparent thin-film transistors based on printable silver nanowires, carbon nanotubes and an elastomeric dielectric

    NASA Astrophysics Data System (ADS)

    Liang, Jiajie; Li, Lu; Chen, Dustin; Hajagos, Tibor; Ren, Zhi; Chou, Shu-Yu; Hu, Wei; Pei, Qibing

    2015-07-01

    Thin-film field-effect transistor is a fundamental component behind various mordern electronics. The development of stretchable electronics poses fundamental challenges in developing new electronic materials for stretchable thin-film transistors that are mechanically compliant and solution processable. Here we report the fabrication of transparent thin-film transistors that behave like an elastomer film. The entire fabrication is carried out by solution-based techniques, and the resulting devices exhibit a mobility of ~30 cm2 V-1 s-1, on/off ratio of 103-104, switching current >100 μA, transconductance >50 μS and relative low operating voltages. The devices can be stretched by up to 50% strain and subjected to 500 cycles of repeated stretching to 20% strain without significant loss in electrical property. The thin-film transistors are also used to drive organic light-emitting diodes. The approach and results represent an important progress toward the development of stretchable active-matrix displays.

  12. Monolithically integrated, flexible display of polymer-dispersed liquid crystal driven by rubber-stamped organic thin-film transistors

    SciTech Connect

    Mach, P.; Rodriguez, S. J.; Nortrup, R.; Wiltzius, P.; Rogers, J. A.

    2001-06-04

    This letter describes the monolithic integration of rubber-stamped thin-film organic transistors with polymer-dispersed liquid crystals (PDLCs) to create a multipixel, flexible display with plastic substrates. We report the electro-optic switching behavior of the PDLCs as driven by the organic transistors, and we show that our displays operate robustly under flexing and have a contrast comparable to that of newsprint. {copyright} 2001 American Institute of Physics.

  13. Studies of polycrystalline pentacene thin-film transistors at the microscopic level

    NASA Astrophysics Data System (ADS)

    Cheng, Horng-Long; Chou, Wei-Yang; Kuo, Chia-Wei; Mai, Yu-Shen; Tang, Fu-Ching; Lai, Szu-Hao

    2006-08-01

    The electronic transport properties of polycrystalline pentacene-based thin film transistors (TFTs) were investigated at the microscopic level using microRaman spectroscopy. All the pentacene film, which were thermally evaporated as a layer with thickness of 70 nm, featured polycrystalline structure with only "thin film" phase polymorph and grain morphology as verified by x-ray diffraction (XRD) measurements. We have investigated the molecular vibrational modes of pentacene in the active channel during operations the organic TFT devices using in-situ Raman spectroscopy. Extra vibrational modes resulting from vibrational coupling effect in pentacene film were studied. The interlayer and intralayer intermolecular vibrational coupling energy was calculated from the Davydov splitting using a simple coupled-oscillator model. The results suggest that the C-H in-plane bending vibrational coupling energy of pentacene molecules in solid film is affected by operating device. Additionally, the aromatic C-C stretching vibrational modes also were investigated. However, it is rather difficult to obtain the variations of lattice parameters of pentacene film in a very small active channel by using electron diffraction and XRD. At the same time, MicroRaman technique provides the capability to explore the intermolecular coupling and molecular structure modifications.

  14. Air-stable solution-processed n-channel organic thin film transistors with polymerenhanced morphology

    DOE PAGESBeta

    He, Zhengran; Shaik, Shoieb; Bi, Sheng; Chen, Jihua; Li, Dawen

    2015-05-04

    N,N0-1H,1H-perfluorobutyl dicyanoperylenecarboxydiimide (PDIF-CN2) is an n-type semiconductor exhibiting high electron mobility and excellent air stability. However, the reported electron mobility based on spin-coated PDIF-CN2 film is much lower than the value of PDIF-CN2 single crystals made from vapor phase deposition, indicating significant room for mobility enhancement. In this study, various insulating polymers, including poly(vinyl alcohol), poly(methyl methacrylate) (PMMA), and poly(alpha-methylstyrene) (PaMS), are pre-coated on silicon substrate aiming to enhance the morphology of the PDIF-CN2 thin film, thereby improving the charge transport and air stability. Atomic force microscopy images reveal that with the pre-deposition of PaMS or PMMA polymers, the morphologymore » of the PDIF-CN2 polycrystalline films is optimized in semiconducting crystal connectivity, domain size, and surface roughness, which leads to significant improvement of organic thin-film transistor (OTFT) performance. Particularly, an electron mobility of up to 0.55 cm2/V s has been achieved from OTFTs based on the PDIF-CN2 film with the pre-deposition of PaMS polymer.« less

  15. Air-stable solution-processed n-channel organic thin film transistors with polymerenhanced morphology

    SciTech Connect

    He, Zhengran; Shaik, Shoieb; Bi, Sheng; Chen, Jihua; Li, Dawen

    2015-05-04

    N,N0-1H,1H-perfluorobutyl dicyanoperylenecarboxydiimide (PDIF-CN2) is an n-type semiconductor exhibiting high electron mobility and excellent air stability. However, the reported electron mobility based on spin-coated PDIF-CN2 film is much lower than the value of PDIF-CN2 single crystals made from vapor phase deposition, indicating significant room for mobility enhancement. In this study, various insulating polymers, including poly(vinyl alcohol), poly(methyl methacrylate) (PMMA), and poly(alpha-methylstyrene) (PaMS), are pre-coated on silicon substrate aiming to enhance the morphology of the PDIF-CN2 thin film, thereby improving the charge transport and air stability. Atomic force microscopy images reveal that with the pre-deposition of PaMS or PMMA polymers, the morphology of the PDIF-CN2 polycrystalline films is optimized in semiconducting crystal connectivity, domain size, and surface roughness, which leads to significant improvement of organic thin-film transistor (OTFT) performance. Particularly, an electron mobility of up to 0.55 cm2/V s has been achieved from OTFTs based on the PDIF-CN2 film with the pre-deposition of PaMS polymer.

  16. Aqueous combustion synthesis of aluminum oxide thin films and application as gate dielectric in GZTO solution-based TFTs.

    PubMed

    Branquinho, Rita; Salgueiro, Daniela; Santos, Lídia; Barquinha, Pedro; Pereira, Luís; Martins, Rodrigo; Fortunato, Elvira

    2014-11-26

    Solution processing has been recently considered as an option when trying to reduce the costs associated with deposition under vacuum. In this context, most of the research efforts have been centered in the development of the semiconductors processes nevertheless the development of the most suitable dielectrics for oxide based transistors is as relevant as the semiconductor layer itself. In this work we explore the solution combustion synthesis and report on a completely new and green route for the preparation of amorphous aluminum oxide thin films; introducing water as solvent. Optimized dielectric layers were obtained for a water based precursor solution with 0.1 M concentration and demonstrated high capacitance, 625 nF cm(-2) at 10 kHz, and a permittivity of 7.1. These thin films were successfully applied as gate dielectric in solution processed gallium-zinc-tin oxide (GZTO) thin film transistors (TFTs) yielding good electrical performance such as subthreshold slope of about 0.3 V dec(-1) and mobility above 1.3 cm2 V(-1) s(-1). PMID:25354332

  17. Characterizing p-channel thin film transistors using ZnO/hydrated polyvinyl alcohol as the conducting channel

    SciTech Connect

    Liau, Leo Chau-Kuang Hsu, Tzu-Hsien; Lo, Pei-Hsuan

    2014-08-11

    We report the characteristics of p-channel thin film transistors (p-TFTs) with ZnO/hydrated polyvinyl alcohol (PVA) (ZnO/PVA) conducting channels. The metal-oxide-semiconductor structure of the p-TFTs was composed of indium tin oxide (ITO)/SiO{sub 2}/ZnO/PVA layers. The TFT was assembled using PVA gel, which was glued to ITO substrates patterned to form source and drain electrodes. The ZnO/PVA composite film acted as an effective conducting film because of the chemisorption reaction at the film interface where free electrons can be generated. The formation of the conducting channel was also affected by V{sub G} applied to the TFT. The ZnO/PVA-based TFTs demonstrated p-channel transistor performance, shown by current-voltage (I-V) data analysis. The electrical parameters of the device were evaluated, including the on/off ratio (∼10{sup 3}), threshold voltage (V{sub th}, −1 V), and subthreshold swing (−2.2 V/dec). The PVA/ZnO-based p-TFTs were fabricated using simple and cost-effective approaches instead of doping methods.

  18. Studies on nickel-tungsten oxide thin films

    SciTech Connect

    Usha, K. S.; Sivakumar, R.; Sanjeeviraja, C.

    2014-10-15

    Nickel-Tungsten oxide (95:5) thin films were prepared by rf sputtering at 200W rf power with various substrate temperatures. X-ray diffraction study reveals the amorphous nature of films. The substrate temperature induced decrease in energy band gap with a maximum transmittance of 71%1 was observed. The Micro-Raman study shows broad peaks at 560 cm{sup −1} and 1100 cm{sup −1} correspond to Ni-O vibration and the peak at 860 cm{sup −1} can be assigned to the vibration of W-O-W bond. Photoluminescence spectra show two peaks centered on 420 nm and 485 nm corresponding to the band edge emission and vacancies created due to the addition of tungsten, respectively.

  19. Studies on nickel-tungsten oxide thin films

    NASA Astrophysics Data System (ADS)

    Usha, K. S.; Sivakumar, R.; Sanjeeviraja, C.

    2014-10-01

    Nickel-Tungsten oxide (95:5) thin films were prepared by rf sputtering at 200W rf power with various substrate temperatures. X-ray diffraction study reveals the amorphous nature of films. The substrate temperature induced decrease in energy band gap with a maximum transmittance of 71%1 was observed. The Micro-Raman study shows broad peaks at 560 cm-1 and 1100 cm-1 correspond to Ni-O vibration and the peak at 860 cm-1 can be assigned to the vibration of W-O-W bond. Photoluminescence spectra show two peaks centered on 420 nm and 485 nm corresponding to the band edge emission and vacancies created due to the addition of tungsten, respectively.

  20. A light-stimulated synaptic transistor with synaptic plasticity and memory functions based on InGaZnOx-Al2O3 thin film structure

    NASA Astrophysics Data System (ADS)

    Li, H. K.; Chen, T. P.; Liu, P.; Hu, S. G.; Liu, Y.; Zhang, Q.; Lee, P. S.

    2016-06-01

    In this work, a synaptic transistor based on the indium gallium zinc oxide (IGZO)-aluminum oxide (Al2O3) thin film structure, which uses ultraviolet (UV) light pulses as the pre-synaptic stimulus, has been demonstrated. The synaptic transistor exhibits the behavior of synaptic plasticity like the paired-pulse facilitation. In addition, it also shows the brain's memory behaviors including the transition from short-term memory to long-term memory and the Ebbinghaus forgetting curve. The synapse-like behavior and memory behaviors of the transistor are due to the trapping and detrapping processes of the holes, which are generated by the UV pulses, at the IGZO/Al2O3 interface and/or in the Al2O3 layer.

  1. Effect of curing temperature on nano-silver paste ink for organic thin-film transistors.

    PubMed

    Kim, Minseok; Koo, Jae Bon; Baeg, Kang-Jun; Noh, Yong-Young; Yang, Yong Suk; Jung, Soon-Won; Ju, Byeong-Kwon; You, In-Kyu

    2012-04-01

    Silver (Ag) metal electrode having 20 microm channel length was printed by reverse offset printing (ROP) using nano-silver paste ink for the source/drain of organic thin-film transistors (OTFT). Specific resistance and surface roughness of printed Ag electrodes with increasing curing temperature were investigated, and surface morphology and grain growth mechanism were systematically verified using a scanning electron microscope (SEM) and atomic force microscope (AFM) in order to obtain an optimized ROP Ag electrode. The Ag electrode was applied to fabricate top-gate/bottom-contact poly(3-hexylthiophene) OTFT devices, which showed reproducible OTFT characteristics such as the field-effect mobility, threshold voltage, and an on/off-current ratio of -10(-3) cm2/Vs, 0.36 V, and -10(2), respectively. PMID:22849104

  2. Operational stability in pentacene thin-film transistors with threshold voltages tuned by oxygen plasma treatment

    NASA Astrophysics Data System (ADS)

    Kimura, Yoshinari; Kitamura, Masatoshi; Kitani, Asahi; Arakawa, Yasuhiko

    2016-02-01

    Pentacene-based organic thin-film transistors (TFTs) having a SiO2 gate dielectric treated with oxygen plasma have been investigated for control of the threshold voltage. The threshold voltage changed in the wide range from -15 to 80 V, depending on plasma treatment time, AC power for plasma generation, and gate dielectric thickness. The threshold voltage change was attributed to negative charges induced on and/or near the surface of the gate dielectric. The threshold voltage change on the order of 1 V was particularly proportional to plasma treatment time. The predictable change enables the control of threshold voltage in this range. In addition, the effect of gate bias stress on threshold voltage was examined. The results suggested that gate bias stress does not negate the threshold voltage change induced by plasma treatment.

  3. Ultraviolet-enhanced device properties in pentacene-based thin-film transistors

    SciTech Connect

    Choi, Jeong-M.; Hwang, D. K.; Hwang, Jung Min; Kim, Jae Hoon; Im, Seongil

    2007-03-12

    The authors report on the ultraviolet (UV)-enhanced device properties in pentacene-based thin-film transistors (TFTs). Pentacene TFTs showed a degraded mobility and lowered saturation current after illumination by a high energy UV with 254 nm wavelength. However, under 364 nm UV these devices surprisingly displayed enhanced saturation current and also showed threshold voltage shift toward lower values, maintaining their mobilities. The saturation current increase and threshold voltage shift were further related to the negative fixed charges excessively formed at the pentacene/dielectric interface by the low energy UV. The authors thus conclude that a low energy UV could rather enhance the pentacene TFT performances and also control the threshold voltage of the device.

  4. DC sputtered amorphous In-Sn-Zn-O thin-film transistors: Electrical properties and stability

    NASA Astrophysics Data System (ADS)

    Nakata, Mitsuru; Zhao, Chumin; Kanicki, Jerzy

    2016-02-01

    In this study, we investigated the electrical properties of DC sputtered amorphous In-Sn-Zn-O (a-ITZO) thin-film transistors (TFTs) fabricated under various process conditions. Fabricated a-ITZO TFTs achieved a threshold voltage (VT) of 1.0 V, subthreshold swing (SS) of 0.38 V/dec and field-effect mobility (μeff) of around 30 cm2/V s. An analytical field-effect mobility model is proposed for a-ITZO TFTs with key parameters extracted using different methods. The impacts of a-ITZO channel thickness and oxygen gas flow ratio on device performance were evaluated. Finally, the a-ITZO TFT bias-temperature stress (BTS) induced electrical instability was studied. In comparison to amorphous In-Ga-Zn-O (a-IGZO) TFTs, improved electrical stability was observed for a-ITZO TFTs using exactly the same BTS conditions.

  5. Low Temperature Polycrystalline Silicon Thin Film Transistor Pixel Circuits for Active Matrix Organic Light Emitting Diodes

    NASA Astrophysics Data System (ADS)

    Fan, Ching-Lin; Lin, Yu-Sheng; Liu, Yan-Wei

    A new pixel design and driving method for active matrix organic light emitting diode (AMOLED) displays that use low-temperature polycrystalline silicon thin-film transistors (LTPS-TFTs) with a voltage programming method are proposed and verified using the SPICE simulator. We had employed an appropriate TFT model in SPICE simulation to demonstrate the performance of the pixel circuit. The OLED anode voltage variation error rates are below 0.35% under driving TFT threshold voltage deviation (Δ Vth =± 0.33V). The OLED current non-uniformity caused by the OLED threshold voltage degradation (Δ VTO =+0.33V) is significantly reduced (below 6%). The simulation results show that the pixel design can improve the display image non-uniformity by compensating for the threshold voltage deviation in the driving TFT and the OLED threshold voltage degradation at the same time.

  6. Electrical mobility in organic thin-film transistors determined by noise spectroscopy

    NASA Astrophysics Data System (ADS)

    Bonavolontà, C.; Albonetti, C.; Barra, M.; Valentino, M.

    2011-11-01

    Organic field-effect transistors (OFET) based on both n-type (perylene derivative) and p-type (α-sexithiophene and pentacene) organic thin films are characterized using low-frequency noise spectroscopy to estimate the charge carrier mobility. The power spectral density shows that the exposure of OFET to air affects the thermal noise fluctuations and that the thermal noise RMS value depends on gate voltage. The power spectral density noise proves that the carrier mobility is gate-voltage dependent. Unlike the I-V measurements, the noise spectroscopy analysis demonstrates the dependence of the mobility on the carrier polarity. We discuss the charge mobility and transport mechanism of a pentacene device with and without electrodes functionalized by an octanethiol chain. The results show that in the functionalized device the carrier mobility is improved and does not depend on the high gate voltage.

  7. High performance organic thin film transistor with phenyltrimethoxysilane-modified dielectrics

    NASA Astrophysics Data System (ADS)

    Yuan, Guang Cai; Xu, Zheng; Gong, Cheng; Cai, Qin Jia; Lu, Zhi Song; Shi, Jing Sheng; Zhang, Fu Jun; Zhao, Su Ling; Xu, Na; Li, Chang Ming

    2009-04-01

    In this work, fabrication of organic thin film transistors (OTFTs) using a phenyltrimethoxysilane (PhTMS) modified SiO2 insulator greatly improves the device electrical properties over those with plain or octadecyltrichlorosilane (OTS) modified SiO2, particularly improves the carrier mobility, the subthreshold slope, and channel resistance resulted from reduced density of charge trapping states at the semiconductor/insulator interface. The pentacene OTFTs with modification from PhTMS (3.5‰ v/v) achieves carrier mobility of 1.03 cm2/V s, on/off current ratio of 1.98×105, and subthreshold slope of 0.20 V/decade. This work renders a new, simple approach to significantly improve the OTFT performance.

  8. Influence of inserting a thin fullerene layer on pentacene organic thin-film transistor

    NASA Astrophysics Data System (ADS)

    Li, Yu-Chang; Lin, Yu-Ju; Wei, Chia-Yu; Chou, Dei-Wei; Tsao, Chun-Ho; Wang, Yeong-Her

    2012-03-01

    The performance of organic thin-film transistors (TFTs) with a pentacene/fullerene(C60)/pentacene (PCP) sandwich structure is presented. Using a 3.5 nm-thick C60 layer inserted between the pentacene films, the obtained hole mobility is improved by more than six times. By applying atomic force microscopy, x-ray diffraction, Raman spectrum, and transmission line method analysis, one can reasonably infer that the smoother surface of the pentacene film covered with thin C60 layer delays the phase transformation of the upper pentacene film, resulting in stronger intermolecular coupling and the reduction of channel resistance of the PCP TFTs from 3.03 to 1.72 MΩ, and, therefore, improving the device performance.

  9. Enhancing the performance of organic thin film transistors using a novel photoalignment method

    NASA Astrophysics Data System (ADS)

    Chou, Wei-Yang; Kuo, Chia-Wei; Mai, Yu-Shen; Lin, Shih-Ting; Cheng, Hong-Long; Liao, Chi-Chang; Shu, Dun-Ying

    2004-10-01

    This study first demonstrated the feasibility of using the photoalignment method to adequately control the structural anisotropy of pentacene films, which are active semiconducting layers, in thin-film transistors (TFTs) with conspicuous anisotropic electrical characteristics. The photoaligned pentacene films were characterized with respect to structure and morphology using x-ray diffraction, atomic force microscopy and Raman scattering. Compared to the uncontrolled pentacene films, a maximum 25-times increase in field-effect mobility (up to 0.82 cm2/Vs) is achieved in the photoaligned pentacene-based TFTs by aligning pentacene orientation parallel to the current flow direction using a photoaligned polyimide layer. Mobility anisotropic ratios ranging between 2.7-8.3 for the current flow parallel and perpendicular to the alignment of the photoaligned pentacene films have been observed for photoaligned pentacene-based TFTs.

  10. Numerical Analysis on the Mechanical Properties of Organic Thin Film Transistor

    NASA Astrophysics Data System (ADS)

    Lee, S. C.; Lee, D. K.; Seol, Y. G.; Ahn, J. H.; Lee, N. E.; Kim, Y. J.

    The organic thin film transistor (OTFT) on flexible substrate electroplated electrodes has many advantages as in the fabrication of low cost sensors, e-paper, smart cards, and flexible displays. In this study, we simulated the mechanical and electrical characteristics of the OTFT with various voltage conditions by using COMSOL. The model consisting of a channel, source and drain was employed to investigate the temperature distribution and thermal stress concentration. The channel length is 40 µm and the voltage ranged between -20V and -40V. The OTFT was fabricated using pentacene as a semiconducting layer and electroplated Ni as a gate electrode. Mechanical properties of the fabricated OTFT were characterized by thermal stress which was predicted with the result of stress distribution.

  11. All-printed and transparent single walled carbon nanotube thin film transistor devices

    NASA Astrophysics Data System (ADS)

    Sajed, Farzam; Rutherglen, Christopher

    2013-09-01

    We present fully transparent single-walled all-carbon nanotube thin film transistors (SWCNT TFT) fabricated using low-cost inkjet printing methods. Such a demonstration provides a platform towards low cost fully printed transparent electronics. The SWCNT TFTs were printed with metallic and semiconducting SWCNT using a room temperature printing process, without the requirement of expensive cleanroom facilities. The unoptimized SWCNT TFTs fabricated exhibited an Ion/off ratio of 92 and mobility of 2.27 cm2V-1s-1 and transmissivity of 82%. The combination of both high electrical performance and high transparency make all-SWCNT TFTs desirable for next generation transparent display backplanes and products such as Google Glass.

  12. Influence of curvature on the device physics of thin film transistors on flexible substrates

    SciTech Connect

    Amalraj, Rex; Sambandan, Sanjiv

    2014-10-28

    Thin film transistors (TFTs) on elastomers promise flexible electronics with stretching and bending. Recently, there have been several experimental studies reporting the behavior of TFTs under bending and buckling. In the presence of stress, the insulator capacitance is influenced due to two reasons. The first is the variation in insulator thickness depending on the Poisson ratio and strain. The second is the geometric influence of the curvature of the insulator-semiconductor interface during bending or buckling. This paper models the role of curvature on TFT performance and brings to light an elegant result wherein the TFT characteristics is dependent on the area under the capacitance-distance curve. The paper compares models with simulations and explains several experimental findings reported in literature.

  13. A high-k ferroelectric relaxor terpolymer as a gate dielectric for orgnaic thin film transistors

    SciTech Connect

    Wu, Shan; Shao, Ming; Burlingame, Quinn; Chen, Xiangzhong; Lin, Minren; Xiao, Kai; Zhang, Qiming

    2013-01-01

    Poly(vinylidenefluoride-trifluoroethylene-chlorofluoroethylene) (P(VDF-TrFE-CFE)) is a ferroelectric terpolymer relaxor with a static dielectric constant of 50, which was developed using defect modification to eliminate remnant polarization in the normal ferroelectric PVDF. In this work, this solution processable terpolymer was used as the gate insulator in bottom gated organic thin-film transistors with a pentacene semiconductor layer. Due to the high dielectric constant of P(VDF-TrFE- CFE), a large capacitive coupling between the gate and channel can be achieved which causes a high charge concentration at the interface of the semiconductor and dielectric layers. In this device, an on/ off ratio of 104 and a low minimum operation gate voltage (5-10 V) were attained

  14. Review on thin-film transistor technology, its applications, and possible new applications to biological cells

    NASA Astrophysics Data System (ADS)

    Tixier-Mita, Agnès; Ihida, Satoshi; Ségard, Bertrand-David; Cathcart, Grant A.; Takahashi, Takuya; Fujita, Hiroyuki; Toshiyoshi, Hiroshi

    2016-04-01

    This paper presents a review on state-of-the-art of thin-film transistor (TFT) technology and its wide range of applications, not only in liquid crystal displays (TFT-LCDs), but also in sensing devices. The history of the evolution of the technology is first given. Then the standard applications of TFT-LCDs, and X-ray detectors, followed by state-of-the-art applications in the field of chemical and biochemical sensing are presented. TFT technology allows the fabrication of dense arrays of independent and transparent microelectrodes on large glass substrates. The potential of these devices as electrical substrates for biological cell applications is then described. The possibility of using TFT array substrates as new tools for electrical experiments on biological cells has been investigated for the first time by our group. Dielectrophoresis experiments and impedance measurements on yeast cells are presented here. Their promising results open the door towards new applications of TFT technology.

  15. Amorphous semiconducting and conducting transparent metal oxide thin films and production thereof

    SciTech Connect

    Perkins, John; Van Hest, Marinus Franciscus Antonius Maria; Ginley, David; Taylor, Matthew; Neuman, George A.; Luten, Henry A.; Forgette, Jeffrey A.; Anderson, John S.

    2010-07-13

    Metal oxide thin films and production thereof are disclosed. An exemplary method of producing a metal oxide thin film may comprise introducing at least two metallic elements and oxygen into a process chamber to form a metal oxide. The method may also comprise depositing the metal oxide on a substrate in the process chamber. The method may also comprise simultaneously controlling a ratio of the at least two metallic elements and a stoichiometry of the oxygen during deposition. Exemplary amorphous metal oxide thin films produced according to the methods herein may exhibit highly transparent properties, highly conductive properties, and/or other opto-electronic properties.

  16. Origin of mobility enhancement by chemical treatment of gate-dielectric surface in organic thin-film transistors: Quantitative analyses of various limiting factors in pentacene thin films

    NASA Astrophysics Data System (ADS)

    Matsubara, R.; Sakai, Y.; Nomura, T.; Sakai, M.; Kudo, K.; Majima, Y.; Knipp, D.; Nakamura, M.

    2015-11-01

    For the better performance of organic thin-film transistors (TFTs), gate-insulator surface treatments are often applied. However, the origin of mobility increase has not been well understood because mobility-limiting factors have not been compared quantitatively. In this work, we clarify the influence of gate-insulator surface treatments in pentacene thin-film transistors on the limiting factors of mobility, i.e., size of crystal-growth domain, crystallite size, HOMO-band-edge fluctuation, and carrier transport barrier at domain boundary. We quantitatively investigated these factors for pentacene TFTs with bare, hexamethyldisilazane-treated, and polyimide-coated SiO2 layers as gate dielectrics. By applying these surface treatments, size of crystal-growth domain increases but both crystallite size and HOMO-band-edge fluctuation remain unchanged. Analyzing the experimental results, we also show that the barrier height at the boundary between crystal-growth domains is not sensitive to the treatments. The results imply that the essential increase in mobility by these surface treatments is only due to the increase in size of crystal-growth domain or the decrease in the number of energy barriers at domain boundaries in the TFT channel.

  17. Radiation sensitivity of graphene field effect transistors and other thin film architectures

    NASA Astrophysics Data System (ADS)

    Cazalas, Edward

    An important contemporary motivation for advancing radiation detection science and technology is the need for interdiction of nuclear and radiological materials, which may be used to fabricate weapons of mass destruction. The detection of such materials by nuclear techniques relies on achieving high sensitivity and selectivity to X-rays, gamma-rays, and neutrons. To be attractive in field deployable instruments, it is desirable for detectors to be lightweight, inexpensive, operate at low voltage, and consume low power. To address the relatively low particle flux in most passive measurements for nuclear security applications, detectors scalable to large areas that can meet the high absolute detection efficiency requirements are needed. Graphene-based and thin-film-based radiation detectors represent attractive technologies that could meet the need for inexpensive, low-power, size-scalable detection architectures, which are sensitive to X-rays, gamma-rays, and neutrons. The utilization of graphene to detect ionizing radiation relies on the modulation of graphene charge carrier density by changes in local electric field, i.e. the field effect in graphene. Built on the principle of a conventional field effect transistor, the graphene-based field effect transistor (GFET) utilizes graphene as a channel and a semiconducting substrate as an absorber medium with which the ionizing radiation interacts. A radiation interaction event that deposits energy within the substrate creates electron-hole pairs, which modify the electric field and modulate graphene charge carrier density. A detection event in a GFET is therefore measured as a change in graphene resistance or current. Thin (micron-scale) films can also be utilized for radiation detection of thermal neutrons provided nuclides with high neutron absorption cross section are present with appreciable density. Detection in thin-film detectors could be realized through the collection of charge carriers generated within the

  18. High-mobility ZrInO thin-film transistor prepared by an all-DC-sputtering method at room temperature

    PubMed Central

    Xiao, Peng; Dong, Ting; Lan, Linfeng; Lin, Zhenguo; Song, Wei; Luo, Dongxiang; Xu, Miao; Peng, Junbiao

    2016-01-01

    Thin-film transistors (TFTs) with zirconium-doped indium oxide (ZrInO) semiconductor were successfully fabricated by an all-DC-sputtering method at room temperature. The ZrInO TFT without any intentionally annealing steps exhibited a high saturation mobility of 25.1 cm2V−1s−1. The threshold voltage shift was only 0.35 V for the ZrInO TFT under positive gate bias stress for 1 hour. Detailed studies showed that the room-temperature ZrInO thin film was in the amorphous state with low carrier density because of the strong bonding strength of Zr-O. The room-temperature process is attractive for its compatibility with almost all kinds of the flexible substrates, and the DC sputtering process is good for the production efficiency improvement and the fabrication cost reduction. PMID:27118177

  19. High-mobility ZrInO thin-film transistor prepared by an all-DC-sputtering method at room temperature.

    PubMed

    Xiao, Peng; Dong, Ting; Lan, Linfeng; Lin, Zhenguo; Song, Wei; Luo, Dongxiang; Xu, Miao; Peng, Junbiao

    2016-01-01

    Thin-film transistors (TFTs) with zirconium-doped indium oxide (ZrInO) semiconductor were successfully fabricated by an all-DC-sputtering method at room temperature. The ZrInO TFT without any intentionally annealing steps exhibited a high saturation mobility of 25.1 cm(2)V(-1)s(-1). The threshold voltage shift was only 0.35 V for the ZrInO TFT under positive gate bias stress for 1 hour. Detailed studies showed that the room-temperature ZrInO thin film was in the amorphous state with low carrier density because of the strong bonding strength of Zr-O. The room-temperature process is attractive for its compatibility with almost all kinds of the flexible substrates, and the DC sputtering process is good for the production efficiency improvement and the fabrication cost reduction. PMID:27118177

  20. High-mobility ZrInO thin-film transistor prepared by an all-DC-sputtering method at room temperature

    NASA Astrophysics Data System (ADS)

    Xiao, Peng; Dong, Ting; Lan, Linfeng; Lin, Zhenguo; Song, Wei; Luo, Dongxiang; Xu, Miao; Peng, Junbiao

    2016-04-01

    Thin-film transistors (TFTs) with zirconium-doped indium oxide (ZrInO) semiconductor were successfully fabricated by an all-DC-sputtering method at room temperature. The ZrInO TFT without any intentionally annealing steps exhibited a high saturation mobility of 25.1 cm2V‑1s‑1. The threshold voltage shift was only 0.35 V for the ZrInO TFT under positive gate bias stress for 1 hour. Detailed studies showed that the room-temperature ZrInO thin film was in the amorphous state with low carrier density because of the strong bonding strength of Zr-O. The room-temperature process is attractive for its compatibility with almost all kinds of the flexible substrates, and the DC sputtering process is good for the production efficiency improvement and the fabrication cost reduction.

  1. Physical properties in thin films of iron oxides.

    SciTech Connect

    Uribe, J. D.; Osorio, J.; Barrero, C. A.; Girata, D.; Morales, A. L.; Hoffmann, A.; Materials Science Division; Univ. de Antioquia

    2008-01-01

    We have grown hematite ({alpha}-Fe{sub 2}O{sub 3}) thin films on stainless steel substrates and magnetite (Fe{sub 3}O{sub 4}) thin films on (0 0 1)-Si single crystal substrates by a RF magnetron sputtering process. {alpha}-Fe{sub 2}O{sub 3} thin films were grown in an Ar atmosphere at substrate temperatures around 400 C, and Fe{sub 3}O{sub 4} thin films in an Ar/O{sub 2} reactive atmosphere at substrate temperatures around 500 C. Conversion electron Moessbauer (CEM) spectra of {alpha}-Fe{sub 2}O{sub 3} thin films exhibit values for hyperfine parameter characteristic of the hematite stoichiometric phase in the weak ferromagnetic state [R.E. Vandenberghe, in: Moessbauer Spectroscopy and Applications in Geology, University Gent, Belgium, 1990. [1

  2. Synthesis and Oxidation Resistance of h-BN Thin Films

    NASA Astrophysics Data System (ADS)

    Stewart, David; Meulenberg, Robert; Lad, Robert

    Hexagonal boron nitride (h-BN) is an exciting 2D material for use in sensors and other electronic devices that operate in harsh, high temperature environments. Not only is h-BN a wide band gap material with excellent wear resistance and high temperature stability, but recent reports indicate that h-BN can prevent metallic substrates from oxidizing above 600°C in low O2 pressures. However, the PVD of highly crystalline h-BN films required for this oxidation protection has proven challenging. In this work, we have explored the growth of h-BN thin films by reactive RF magnetron sputtering from an elemental B target in an Ar/N2 atmosphere. The film growth rate is extremely slow and the resulting films are atomically smooth and homogeneous. Using DC biasing during deposition and high temperature annealing treatments, the degree of film crystallinity can be controlled. The oxidation resistance of h-BN films deposited on inert sapphire and reactive metal substrates such as Zr and ZrB2 has been examined by techniques such as XPS, XRD, and SEM after oxidation between 600 and 1200°C under varying oxygen pressures. The success of h-BN as a passivation layer for metallic substrates in harsh environments is shown to depend greatly on its crystalline quality and defects. Supported by the NSF SusChEM program.

  3. High mobility bottom gate InGaZnO thin film transistors with SiO{sub x} etch stopper

    SciTech Connect

    Kim, Minkyu; Jeong, Jong Han; Lee, Hun Jung; Ahn, Tae Kyung; Shin, Hyun Soo; Park, Jin-Seong; Jeong, Jae Kyeong; Mo, Yeon-Gon; Kim, Hye Dong

    2007-05-21

    The authors report on the fabrication of thin film transistors (TFTs), which use an amorphous indium gallium zinc oxide (a-IGZO) channel, by rf sputtering at room temperature and for which the channel length and width are patterned by photolithography and dry etching. To prevent plasma damage to the active channel, a 100-nm-thick SiO{sub x} layer deposited by plasma enhanced chemical vapor deposition was adopted as an etch stopper structure. The a-IGZO TFT (W/L=10 {mu}m/50 {mu}m) fabricated on glass exhibited a high field-effect mobility of 35.8 cm{sup 2}/V s, a subthreshold gate swing value of 0.59 V/decade, a thrseshold voltage of 5.9 V, and an I{sub on/off} ratio of 4.9x10{sup 6}, which is acceptable for use as the switching transistor of an active-matrix TFT backplane.

  4. Enhanced Sensitivity of Gas Sensor Based on Poly(3-hexylthiophene) Thin-Film Transistors for Disease Diagnosis and Environment Monitoring

    PubMed Central

    Cavallari, Marco R.; Izquierdo, José E. E.; Braga, Guilherme S.; Dirani, Ely A. T.; Pereira-da-Silva, Marcelo A.; Rodríguez, Estrella F. G.; Fonseca, Fernando J.

    2015-01-01

    Electronic devices based on organic thin-film transistors (OTFT) have the potential to supply the demand for portable and low-cost gadgets, mainly as sensors for in situ disease diagnosis and environment monitoring. For that reason, poly(3-hexylthiophene) (P3HT) as the active layer in the widely-used bottom-gate/bottom-contact OTFT structure was deposited over highly-doped silicon substrates covered with thermally-grown oxide to detect vapor-phase compounds. A ten-fold organochloride and ammonia sensitivity compared to bare sensors corroborated the application of this semiconducting polymer in sensors. Furthermore, P3HT TFTs presented approximately three-order higher normalized sensitivity than any chemical sensor addressed herein. The results demonstrate that while TFTs respond linearly at the lowest concentration values herein, chemical sensors present such an operating regime mostly above 2000 ppm. Simultaneous alteration of charge carrier mobility and threshold voltage is responsible for pushing the detection limit down to units of ppm of ammonia, as well as tens of ppm of alcohol or ketones. Nevertheless, P3HT transistors and chemical sensors could compose an electronic nose operated at room temperature for a wide range concentration evaluation (1–10,000 ppm) of gaseous analytes. Targeted analytes include not only biomarkers for diseases, such as uremia, cirrhosis, lung cancer and diabetes, but also gases for environment monitoring in food, cosmetic and microelectronics industries. PMID:25912354

  5. Digital radiology using active matrix readout of amorphous selenium: radiation hardness of cadmium selenide thin film transistors.

    PubMed

    Zhao, W; Waechter, D; Rowlands, J A

    1998-04-01

    A flat-panel x-ray imaging detector using active matrix readout of amorphous selenium (a-Se) is being investigated for digital radiography and fluoroscopy. The active matrix consists of a two-dimensional array of thin film transistors (TFTs). Radiation penetrating through the a-Se layer will interact with the TFTs and it is important to ensure that radiation induced changes will not affect the operation of the x-ray imaging detector. The methodology of the present work is to investigate the effects of radiation on the characteristic curves of the TFTs using individual TFT samples made with cadmium selenide (CdSe) semiconductor. Four characteristic parameters, i.e., threshold voltage, subthreshold swing, field effect mobility, and leakage current, were examined. This choice of parameters was based on the well established radiation damage mechanisms for crystalline silicon metal-oxide-semiconductor field-effect transistors (MOSFETs), which have a similar principle of operation as CdSe TFTs. It was found that radiation had no measurable effect on the leakage current and the field effect mobility. However, radiation shifted the threshold voltage and increased the subthreshold swing. But even the estimated lifetime dose (50 Gy) of a diagnostic radiation detector will not affect the normal operation of an active matrix x-ray detector made with CdSe TFTs. The mechanisms of the effects of radiation will be discussed and compared with those for MOSFETs and hydrogenated amorphous silicon (a-Si:H) TFTs. PMID:9571621

  6. Anisotropy and micromagnetics in complex oxide thin films

    NASA Astrophysics Data System (ADS)

    Wynn, Thomas Andrew

    Complex oxide perovskites are a class of material with a remarkably wide range of functional properties including magnetism, superconductivity, metal-to-insulator transitions, colossal magnetoresistance, and in some cases high magnetocrystalline anisotropy. Reduction in length scales through thin film deposition and nanopatterning results in altered properties from their bulk constituents. In this work, thin films of La0.7Sr0.3CoO3 (LSCO) and LSCO/La 0.7Sr0.3MnO3 (LSMO) bilayers of varying thicknesses were deposited onto (LaAlO3)0.3(Sr2TaAlO 6)0.7 (LSAT) substrates, and their anisotropic magnetic properties were measured along the in- plane [100] and [110] directions using superconducting quantum interference device (SQUID) magnetometry and soft x-ray magnetic spectroscopy. The LSCO showed thickness dependent magnetism, and films were non-magnetic below a critical thickness of 4 nm. Magnetic LSCO films showed unique anisotropic effects on the saturation magnetization (Ms), with a lower M s in the [110] direction than the [100] direction. This potentially indicates the existence of a hard component in the [110] direction that is not being switched at fields in the SQUID magnetometer (7 T). Normalized hysteresis loops indicate the LSCO films display little magnetocrystalline anisotropy within the plane of the film. LSCO/LSMO bilayers with a fixed LSMO layer of 6 nm in thickness showed cobalt magnetism at thicknesses where single layers were non-magnetic, suggesting that the substrate/film interface is not the cause of the non-magnetic layer in the LSCO thin films. Magnetic coupling occurs in bilayers with LSCO layer thicknesses of below 4 nm, and both LSCO and LSMO layers showed a [110] easy axis. When the layer thickness of LSCO was increased above 8 nm, the LSCO layer developed a soft component at the LSCO/LSMO interface. This soft LSCO component remained coupled with the LSMO, though the easy axis changed to the [100] direction, and the harder, non-interface LSCO

  7. Formation of carriers in Ti-oxide thin films by substitution reactions

    SciTech Connect

    Liu, Y. S.; Lin, Y. H.; Wei, Y. S.; Liu, C. Y.

    2012-02-15

    Conductive Ti-oxide thin films are produced using a reactive sputtering and post-annealing process. The lowest resistivity of Ti-oxide thin films (2.30 x 10{sup -2}{Omega}-cm) can be achieved after annealing for 1 h at 400 deg. C in ambient O{sub 2}. Additionally, the Hall measurement results indicate that the carrier concentration increases during the initial 1-h annealing process before decreasing during subsequent annealing. By curve fitting the O{sub ls} core-level peaks in the x ray photoelectron spectroscopy (XPS) spectrum of the annealed Ti-oxide thin films, we found that the oxygen (O) vacancy concentration monotonically increases with annealing time, which differs from the behavior of the carrier concentration regarding annealing time. This means that the O-vacancy mechanism alone cannot explain the formation of carriers in Ti-oxide thin films. By curve-fitting core-level Ti peaks in the XPS spectrum of annealed Ti-oxide thin films, a Ti{sup 3+}-to-Ti{sup 4+} substitution reaction in the TiO{sub 2} phase of the Ti-oxide thin film after annealing plays the dominant role in the formation of conduction carriers. Instead of the O-vacancy mechanism, the Ti{sup 3+}-to-Ti{sup 4+} substitution mechanism can explain the concentration of carriers in Ti-oxide thin films following annealing.

  8. Lateral solid-phase epitaxy of oxide thin films on glass substrate seeded with oxide nanosheets.

    PubMed

    Taira, Kenji; Hirose, Yasushi; Nakao, Shoichiro; Yamada, Naoomi; Kogure, Toshihiro; Shibata, Tatsuo; Sasaki, Takayoshi; Hasegawa, Tetsuya

    2014-06-24

    We developed a technique to fabricate oxide thin films with uniaxially controlled crystallographic orientation and lateral size of more than micrometers on amorphous substrates. This technique is lateral solid-phase epitaxy, where epitaxial crystallization of amorphous precursor is seeded with ultrathin oxide nanosheets sparsely (≈10% coverage) deposited on the substrate. Transparent conducting Nb-doped anatase TiO2 thin films were fabricated on glass substrates by this technique. Perfect (001) orientation and large grains with lateral sizes up to 10 μm were confirmed by X-ray diffraction, atomic force microscopy, and electron beam backscattering diffraction measurements. As a consequence of these features, the obtained film exhibited excellent electrical transport properties comparable to those of epitaxial thin films on single-crystalline substrates. This technique is a versatile method for fabricating high-quality oxide thin films other than anatase TiO2 and would increase the possible applications of oxide-based thin film devices. PMID:24867286

  9. Lithium cobalt oxide thin film and its electrochromism

    NASA Astrophysics Data System (ADS)

    Wei, Guang; Haas, Terry E.; Goldner, Ronald B.

    1989-06-01

    Thin films of lithium cobalt oxide have been prepared by RF-sputtering from powdered LiCoO2. These films permit reversible electrolytic removal of lithium ions upon application of an anodic voltage in a propylene carbonate-lithium perchlorate electrolyte, the films changing in color from a pale amber transparent state to a dark brown. A polycrystalline columnar film structure was revealed with SEM and TEM. X ray examination of the films suggests that the layered rhombohedral LiCoO2 structure is the major crystalline phase present. Oxidation-reduction titration and atomic absorption were used for the determination of the film stoichiometry. The results show that the as deposited-films on glass slides are lithium deficient (relative to the starting material) and show a high average cobalt oxidation state near +3.5. The measurements of dc conductivity suggest a band to band conduction at high temperature (300 to 430 K) and hopping conduction in localized states at low temperature (4 to 270 K). The thermoelectric power data show that the films behave as p-type semiconductors. Transmission and reflectance measurements from 400 nm to 2500 nm show significant near-IR reflectivity.

  10. High-performance p-channel polycrystalline-germanium thin-film transistors via excimer laser crystallization and counter doping

    NASA Astrophysics Data System (ADS)

    Liao, Chan-Yu; Huang, Ching-Yu; Huang, Ming-Hui; Chou, Chia-Hsin; Cheng, Huang-Chung

    2016-04-01

    High-quality polycrystalline-germanium (poly-Ge) thin films have been successfully fabricated by excimer laser crystallization (ELC). Grains as large as 1 µm were achieved by ELC at 300 mJ/cm2. Meanwhile, the defect-generated hole concentrations in Ge thin films were significantly reduced. Furthermore, the majority carriers could then be converted to n-type by counter doping (CD) with a suitable dose. Then, high-performance p-channel Ge thin-film transistors (TFTs) with a high on/off current ratio of up to 1.7 × 103 and a high field-effect mobility of up to 208 cm2 V-1 s-1 were demonstrated for a channel width and length both of 0.5 µm. It was revealed that ELC combined with CD is effective for attaining high-performance p-channel poly-Ge TFTs.

  11. Thin film complementary metal oxide semiconductor (CMOS) device using a single-step deposition of the channel layer.

    PubMed

    Nayak, Pradipta K; Caraveo-Frescas, J A; Wang, Zhenwei; Hedhili, M N; Wang, Q X; Alshareef, H N

    2014-01-01

    We report, for the first time, the use of a single step deposition of semiconductor channel layer to simultaneously achieve both n- and p-type transport in transparent oxide thin film transistors (TFTs). This effect is achieved by controlling the concentration of hydroxyl groups (OH-groups) in the underlying gate dielectrics. The semiconducting tin oxide layer was deposited at room temperature, and the maximum device fabrication temperature was 350 °C. Both n and p-type TFTs showed fairly comparable performance. A functional CMOS inverter was fabricated using this novel scheme, indicating the potential use of our approach for various practical applications. PMID:24728223

  12. Thin Film Complementary Metal Oxide Semiconductor (CMOS) Device Using a Single-Step Deposition of the Channel Layer

    PubMed Central

    Nayak, Pradipta K.; Caraveo-Frescas, J. A.; Wang, Zhenwei; Hedhili, M. N.; Wang, Q. X.; Alshareef, H. N.

    2014-01-01

    We report, for the first time, the use of a single step deposition of semiconductor channel layer to simultaneously achieve both n- and p-type transport in transparent oxide thin film transistors (TFTs). This effect is achieved by controlling the concentration of hydroxyl groups (OH-groups) in the underlying gate dielectrics. The semiconducting tin oxide layer was deposited at room temperature, and the maximum device fabrication temperature was 350°C. Both n and p-type TFTs showed fairly comparable performance. A functional CMOS inverter was fabricated using this novel scheme, indicating the potential use of our approach for various practical applications. PMID:24728223

  13. Flexible All-organic, All-solution Processed Thin Film Transistor Array with Ultrashort Channel.

    PubMed

    Xu, Wei; Hu, Zhanhao; Liu, Huimin; Lan, Linfeng; Peng, Junbiao; Wang, Jian; Cao, Yong

    2016-01-01

    Shrinking the device dimension has long been the pursuit of the semiconductor industry to increase the device density and operation speed. In the application of thin film transistors (TFTs), all-organic TFT arrays made by all-solution process are desired for low cost and flexible electronics. One of the greatest challenges is how to achieve ultrashort channel through a cost-effective method. In our study, ultrashort-channel devices are demonstrated by direct inkjet printing conducting polymer as source/drain and gate electrodes without any complicated substrate's pre-patterning process. By modifying the substrate's wettability, the conducting polymer's contact line is pinned during drying process which makes the channel length well-controlled. An organic TFT array of 200 devices with 2 μm channel length is fabricated on flexible substrate through all-solution process. The simple and scalable process to fabricate high resolution organic transistor array offers a low cost approach in the development of flexible and wearable electronics. PMID:27378163

  14. Method for producing silicon thin-film transistors with enhanced forward current drive

    DOEpatents

    Weiner, K.H.

    1998-06-30

    A method is disclosed for fabricating amorphous silicon thin film transistors (TFTs) with a polycrystalline silicon surface channel region for enhanced forward current drive. The method is particularly adapted for producing top-gate silicon TFTs which have the advantages of both amorphous and polycrystalline silicon TFTs, but without problem of leakage current of polycrystalline silicon TFTs. This is accomplished by selectively crystallizing a selected region of the amorphous silicon, using a pulsed excimer laser, to create a thin polycrystalline silicon layer at the silicon/gate-insulator surface. The thus created polysilicon layer has an increased mobility compared to the amorphous silicon during forward device operation so that increased drive currents are achieved. In reverse operation the polysilicon layer is relatively thin compared to the amorphous silicon, so that the transistor exhibits the low leakage currents inherent to amorphous silicon. A device made by this method can be used, for example, as a pixel switch in an active-matrix liquid crystal display to improve display refresh rates. 1 fig.

  15. α,ω-dihexyl-sexithiophene thin films for solution-gated organic field-effect transistors

    NASA Astrophysics Data System (ADS)

    Schamoni, Hannah; Noever, Simon; Nickel, Bert; Stutzmann, Martin; Garrido, Jose A.

    2016-02-01

    While organic semiconductors are being widely investigated for chemical and biochemical sensing applications, major drawbacks such as the poor device stability and low charge carrier mobility in aqueous electrolytes have not yet been solved to complete satisfaction. In this work, solution-gated organic field-effect transistors (SGOFETs) based on the molecule α,ω-dihexyl-sexithiophene (DH6T) are presented as promising platforms for in-electrolyte sensing. Thin films of DH6T were investigated with regard to the influence of the substrate temperature during deposition on the grain size and structural order. The performance of SGOFETs can be improved by choosing suitable growth parameters that lead to a two-dimensional film morphology and a high degree of structural order. Furthermore, the capability of the SGOFETs to detect changes in the pH or ionic strength of the gate electrolyte is demonstrated and simulated. Finally, excellent transistor stability is confirmed by continuously operating the device over a period of several days, which is a consequence of the low threshold voltage of DH6T-based SGOFETs. Altogether, our results demonstrate the feasibility of high performance and highly stable organic semiconductor devices for chemical or biochemical applications.

  16. Flexible All-organic, All-solution Processed Thin Film Transistor Array with Ultrashort Channel

    PubMed Central

    Xu, Wei; Hu, Zhanhao; Liu, Huimin; Lan, Linfeng; Peng, Junbiao; Wang, Jian; Cao, Yong

    2016-01-01

    Shrinking the device dimension has long been the pursuit of the semiconductor industry to increase the device density and operation speed. In the application of thin film transistors (TFTs), all-organic TFT arrays made by all-solution process are desired for low cost and flexible electronics. One of the greatest challenges is how to achieve ultrashort channel through a cost-effective method. In our study, ultrashort-channel devices are demonstrated by direct inkjet printing conducting polymer as source/drain and gate electrodes without any complicated substrate’s pre-patterning process. By modifying the substrate’s wettability, the conducting polymer’s contact line is pinned during drying process which makes the channel length well-controlled. An organic TFT array of 200 devices with 2 μm channel length is fabricated on flexible substrate through all-solution process. The simple and scalable process to fabricate high resolution organic transistor array offers a low cost approach in the development of flexible and wearable electronics. PMID:27378163

  17. Method for producing silicon thin-film transistors with enhanced forward current drive

    DOEpatents

    Weiner, Kurt H.

    1998-01-01

    A method for fabricating amorphous silicon thin film transistors (TFTs) with a polycrystalline silicon surface channel region for enhanced forward current drive. The method is particularly adapted for producing top-gate silicon TFTs which have the advantages of both amorphous and polycrystalline silicon TFTs, but without problem of leakage current of polycrystalline silicon TFTs. This is accomplished by selectively crystallizing a selected region of the amorphous silicon, using a pulsed excimer laser, to create a thin polycrystalline silicon layer at the silicon/gate-insulator surface. The thus created polysilicon layer has an increased mobility compared to the amorphous silicon during forward device operation so that increased drive currents are achieved. In reverse operation the polysilicon layer is relatively thin compared to the amorphous silicon, so that the transistor exhibits the low leakage currents inherent to amorphous silicon. A device made by this method can be used, for example, as a pixel switch in an active-matrix liquid crystal display to improve display refresh rates.

  18. Metal contact effect on the performance and scaling behavior of carbon nanotube thin film transistors.

    PubMed

    Xia, Jiye; Dong, Guodong; Tian, Boyuan; Yan, Qiuping; Zhang, Han; Liang, Xuelei; Peng, Lianmao

    2016-05-21

    Metal-tube contact is known to play an important role in carbon nanotube field-effect transistors (CNT-FETs) which are fabricated on individual CNTs. Less attention has been paid to the contact effect in network type carbon nanotube thin film transistors (CNT-TFTs). In this study, we demonstrate that contact plays an even more important role in CNT-TFTs than in CNT-FETs. Although the Schottky barrier height at the metal-tube contact can be tuned by the work function of the metal, similar to the case in CNT-FETs, the contact resistance (Rc) forms a much higher proportion of the total resistance in CNT-TFTs. Interestingly, the contact resistivity was found to increase with channel length, which is a consequence of the percolating nature of the transport in CNT films, and this behavior does not exist in CNT-FETs and normal 2D Ohmic conductors. Electrical transport in CNT-TFTs has been predicted to scale with channel length by stick percolation theory. However, the scaling behavior is also impacted, or even covered up by the effect of Rc. Once the contact effect is excluded, the covered scaling behavior can be revealed correctly. A possible way of reducing Rc in CNT-TFTs was proposed. We believe the findings in this paper will strengthen our understanding of CNT-TFTs, and even accelerate the commercialization of CNT-TFT technology. PMID:27121370

  19. Flexible All-organic, All-solution Processed Thin Film Transistor Array with Ultrashort Channel

    NASA Astrophysics Data System (ADS)

    Xu, Wei; Hu, Zhanhao; Liu, Huimin; Lan, Linfeng; Peng, Junbiao; Wang, Jian; Cao, Yong

    2016-07-01

    Shrinking the device dimension has long been the pursuit of the semiconductor industry to increase the device density and operation speed. In the application of thin film transistors (TFTs), all-organic TFT arrays made by all-solution process are desired for low cost and flexible electronics. One of the greatest challenges is how to achieve ultrashort channel through a cost-effective method. In our study, ultrashort-channel devices are demonstrated by direct inkjet printing conducting polymer as source/drain and gate electrodes without any complicated substrate’s pre-patterning process. By modifying the substrate’s wettability, the conducting polymer’s contact line is pinned during drying process which makes the channel length well-controlled. An organic TFT array of 200 devices with 2 μm channel length is fabricated on flexible substrate through all-solution process. The simple and scalable process to fabricate high resolution organic transistor array offers a low cost approach in the development of flexible and wearable electronics.

  20. Effect of thermal annealing on the properties of transparent conductive In–Ga–Zn oxide thin films

    SciTech Connect

    Li, Ling; Fan, Lina; Li, Yanhuai; Song, Zhongxiao; Ma, Fei E-mail: chlliu@mail.xjtu.edu.cn; Liu, Chunliang E-mail: chlliu@mail.xjtu.edu.cn

    2014-03-15

    Amorphous In–Ga–Zn oxide (IGZO) thin films were prepared using radio frequency magnetron sputtering at room temperature. Upon thermal annealing at temperatures even up to 500 °C, the amorphous characteristics were still maintained, but the electronic properties could be considerably enhanced. This could be ascribed to the increased optical band gap and the increased oxygen vacancies, as corroborated by the microstructure characterizations. In addition, the surface became smoother upon thermal annealing, guaranteeing good interface contact between electrode and a-IGZO. The optical transmittance at 400–800 nm exceeded 90% for all samples. All in all, thermal annealing at appropriate temperatures is expected to improve the performances of relevant a-IGZO thin film transistors.

  1. Defect Mediated Ferromagnetism in Zinc Oxide Thin Film Heterostructures

    NASA Astrophysics Data System (ADS)

    Mal, Siddhartha

    Recent developments in the field of spintronics (spin based electronics) have led to an extensive search for materials in which semiconducting properties can be integrated with magnetic properties to realize the objective of successful fabrication of spin-based devices. Since zinc oxide (ZnO) posits a promising player, it is important to elucidate the critical issues regarding the origin and nature of magnetism in ZnO thin film heterostructures. Another critical issue in the development of practical devices based on metal oxides is the integration of high quality epitaxial thin films on the existing technology based on Si (100) substrates, which requires appropriate substrate templates. The present research work is focused on the study of room temperature ferromagnetism (RTFM) caused by intrinsic defects and precise control of RTFM using thermal treatments and laser and ion irradiation. We performed a systematic study of the structural, chemical, electrical, optical and magnetic properties of undoped ZnO films grown under different conditions as well as the films that were annealed in various environments. Oxygen annealed films displayed a sequential transition from ferromagnetism to diamagnetism as a function of the annealing temperature. An increase in the green band intensity has been observed in oxygen annealed ZnO films. Reversible switching of room-temperature ferromagnetism and n-type conductivity have been demonstrated by oxygen and vacuum annealing. Detailed electron energy loss spectroscopy and secondary ion mass spectroscopy studies have been presented to rule out the possibility of external source of magnetism. Electron-Paramagnetic Resonance (EPR) measurements indicate the presence of a broad peak at g=2.01. This would be most consistent with the magnetic moment arising from the oxygen vacancies (g=1.996), although the possible contribution from Zn vacancies (g=2.013) cannot be entirely ruled out. The magnetic moment in these films may arise from the

  2. The effects of buffer layers on the performance and stability of flexible InGaZnO thin film transistors on polyimide substrates

    NASA Astrophysics Data System (ADS)

    Ok, Kyung-Chul; Ko Park, Sang-Hee; Hwang, Chi-Sun; Kim, H.; Soo Shin, Hyun; Bae, Jonguk; Park, Jin-Seong

    2014-02-01

    We demonstrated the fabrication of flexible amorphous indium gallium zinc oxide thin-film transistors (TFTs) on high-temperature polyimide (PI) substrates, which were debonded from the carrier glass after TFT fabrication. The application of appropriate buffer layers on the PI substrates affected the TFT performance and stability. The adoption of the SiNx/AlOx buffer layers as water and hydrogen diffusion barriers significantly improved the device performance and stability against the thermal annealing and negative bias stress, compared to single SiNx or SiOx buffer layers. The substrates could be bent down to a radius of curvature of 15 mm and the devices remained normally functional.

  3. Impact of universal mobility law on polycrystalline organic thin-film transistors

    NASA Astrophysics Data System (ADS)

    Raja, Munira; Donaghy, David; Myers, Robert; Eccleston, Bill

    2012-10-01

    We have developed novel analytical models for polycrystalline organic thin-film transistor (OTFT) by employing new concepts on the charge carrier injection to polysilicon thin-films. The models, also incorporate the effect of contact resistance associated with the poor ohmic nature of the contacts. The drain current equations of the OTFT, both in the quasi-diffusion and quasi-drift regimes, predict temperature dependencies on essential material and device parameters. Interestingly, under the drift regime, the polycrystalline OTFT model reveals similar power dependencies on the applied voltages, to those of purely disordered model developed by utilizing the universal mobility law (UML). Such similarities are not thought to be coincidental since the effect of gate voltage on surface potential is influenced by the Fermi level pinning in the grain boundary. Nonetheless, the best fits on the data of 6,13-bis(tri-isopropylsilylethynyl) OTFTs are attained with the proposed polycrystalline rather than the disordered model, particularly at low gate voltages where the diffusive component is dominant. Moreover, in order to understand the effect of grain boundaries, we devise a relationship for the dependency of the effective mobility on carrier concentration, assuming a crystalline region to be in direct contact with a disordered region. Interestingly, we find a similar dependency as the UML in purely disordered materials, which further signifies the conduction to be limited by the grain boundaries. Subsequently, an analytical model for the variation of the effective mobility with gate voltage is established. Such models are vital in assisting the development of more accurate designs of the novel organic circuits.

  4. Surface measurement of indium tin oxide thin film by wavelength-tuning Fizeau interferometry.

    PubMed

    Kim, Yangjin; Hibino, Kenichi; Sugita, Naohiko; Mitsuishi, Mamoru

    2015-08-10

    Indium-tin oxide (ITO) thin films have been widely used in displays such as liquid crystal displays and touch panels because of their favorable electrical conductivity and optical transparency. The surface shape and thickness of ITO thin films must be precisely measured to improve their reliability and performance. Conventional measurement techniques take single point measurements and require expensive systems. In this paper, we measure the surface shape of an ITO thin film on top of a transparent plate using wavelength-tuning Fizeau interferometry. The surface shape was determined by compensating for the phase error introduced by optical interference from the thin film, which was calculated using the phase and amplitude distributions measured by wavelength-tuning. The proposed measurement method achieved noncontact, large-aperture, and precise measurements of transparent thin films. The surface shape of the sample was experimentally measured to an accuracy of 5.13 nm. PMID:26368388

  5. Light-Modulation of the Charge Injection in a Polymer Thin-Film Transistor by Functionalizing the Electrodes with Bistable Photochromic Self-Assembled Monolayers.

    PubMed

    Mosciatti, Thomas; Del Rosso, Maria G; Herder, Martin; Frisch, Johannes; Koch, Norbert; Hecht, Stefan; Orgiu, Emanuele; Samorì, Paolo

    2016-08-01

    High fatigue resistance, bistability, and drastic property changes among isomers allow efficient modulation of the current output of organic thin-film transistors (OTFTs) to be obtained by a photogating of the charge-injection mechanism. PMID:27184349

  6. Transparent conductive reduced graphene oxide thin films produced by spray coating

    NASA Astrophysics Data System (ADS)

    Shi, HongFei; Wang, Can; Sun, ZhiPei; Zhou, YueLiang; Jin, KuiJuan; Yang, GuoZhen

    2015-01-01

    Reduced graphene oxide thin films were fabricated on quartz by spray coating method using a stable dispersion of reduced graphene oxide in N,N-Dimethylformamide. The dispersion was produced by chemical reduction of graphene oxide, and the film thickness was controlled with the amount of spray volume. AFM measurements revealed that the thin films have near-atomically flat surface. The chemical and structural parameters of the samples were analyzed by Raman and XPS studies. It was found that the thin films show electrical conductivity with good optical transparency in the visible to near infrared region. The sheet resistance of the films can be significantly reduced by annealing in vacuum and reach 58 kΩ with a light transmittance of 68.69% at 550 nm. The conductive transparent properties of the reduced graphene oxide thin films would be useful to develop flexible electronics.

  7. Tuning electrical properties in amorphous zinc tin oxide thin films for solution processed electronics.

    PubMed

    Chandra, R Devi; Rao, Manohar; Zhang, Keke; Prabhakar, Rajiv Ramanujam; Shi, Chen; Zhang, Jie; Mhaisalkar, Subodh G; Mathews, Nripan

    2014-01-22

    Solution processed zinc tin oxide (ZTO) thin film transistors (TFTs) were fabricated by varying the Zn/Sn composition. The addition of Sn to the zinc oxide (ZnO) films resulted in improved electrical characteristics, with devices of Zn0.7Sn0.3O composition showing the highest mobility of 7.7 cm(2)/(V s). An improvement in subthreshold swings was also observed, indicative of a reduction of the interfacial trap densities. Mobility studies at low temperature have been carried out, which indicated that the activation energy was reduced with Sn incorporation. Kelvin probe force microscopy was performed on the films to evaluate work function and correlated to the metal-semiconductor barrier indicating Zn0.7Sn0.3O films had the smallest barrier for charge injection. Organic-inorganic hybrid complementary inverters with a maximum gain of 10 were fabricated by integrating ZTO TFTs with poly-3-hexylthiophene (P3HT) transistors. PMID:24380364

  8. Low-voltage polymer/small-molecule blend organic thin-film transistors and circuits fabricated via spray deposition

    SciTech Connect

    Hunter, By Simon; Anthopoulos, Thomas D.; Ward, Jeremy W.; Jurchescu, Oana D.; Payne, Marcia M.; Anthony, John E.

    2015-06-01

    Organic thin-film electronics have long been considered an enticing candidate in achieving high-throughput manufacturing of low-power ubiquitous electronics. However, to achieve this goal, more work is required to reduce operating voltages and develop suitable mass-manufacture techniques. Here, we demonstrate low-voltage spray-cast organic thin-film transistors based on a semiconductor blend of 2,8-difluoro- 5,11-bis (triethylsilylethynyl) anthradithiophene and poly(triarylamine). Both semiconductor and dielectric films are deposited via successive spray deposition in ambient conditions (air with 40%–60% relative humidity) without any special precautions. Despite the simplicity of the deposition method, p-channel transistors with hole mobilities of >1 cm{sup 2}/Vs are realized at −4 V operation, and unipolar inverters operating at −6 V are demonstrated.

  9. High-mobility BaSnO3 thin-film transistor with HfO2 gate insulator

    NASA Astrophysics Data System (ADS)

    Kim, Young Mo; Park, Chulkwon; Kim, Useong; Ju, Chanjong; Char, Kookrin

    2016-01-01

    Thin-film transistors have been fabricated using La-doped BaSnO3 as n-type channels and (In,Sn)2O3 as source, drain, and gate electrodes. HfO2 was grown as gate insulators by atomic layer deposition. The field-effect mobility, Ion/Ioff ratio, and subthreshold swing of the device are 24.9 cm2 V-1 s-1, 6.0 × 106, and 0.42 V dec-1, respectively. The interface trap density, evaluated to be higher than 1013 cm-2 eV-1, was found to be slightly lower than that of the thin-film transistor with an Al2O3 gate insulator. We attribute the much smaller subthreshold swing values to the higher dielectric constant of HfO2.

  10. Influence of an anomalous dimension effect on thermal instability in amorphous-InGaZnO thin-film transistors

    SciTech Connect

    Liu, Kuan-Hsien; Chou, Wu-Ching E-mail: wuchingchou@mail.nctu.edu.tw; Chang, Ting-Chang E-mail: wuchingchou@mail.nctu.edu.tw; Chen, Hua-Mao; Tai, Ya-Hsiang; Tsai, Ming-Yen; Hung, Pei-Hua; Chu, Ann-Kuo; Wu, Ming-Siou; Hung, Yi-Syuan; Hsieh, Tien-Yu; Yeh, Bo-Liang

    2014-10-21

    This paper investigates abnormal dimension-dependent thermal instability in amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistors. Device dimension should theoretically have no effects on threshold voltage, except for in short channel devices. Unlike short channel drain-induced source barrier lowering effect, threshold voltage increases with increasing drain voltage. Furthermore, for devices with either a relatively large channel width or a short channel length, the output drain current decreases instead of saturating with an increase in drain voltage. Moreover, the wider the channel and the shorter the channel length, the larger the threshold voltage and output on-state current degradation that is observed. Because of the surrounding oxide and other thermal insulating material and the low thermal conductivity of the IGZO layer, the self-heating effect will be pronounced in wider/shorter channel length devices and those with a larger operating drain bias. To further clarify the physical mechanism, fast I{sub D}-V{sub G} and modulated peak/base pulse time I{sub D}-V{sub D} measurements are utilized to demonstrate the self-heating induced anomalous dimension-dependent threshold voltage variation and on-state current degradation.

  11. Influence of an anomalous dimension effect on thermal instability in amorphous-InGaZnO thin-film transistors

    NASA Astrophysics Data System (ADS)

    Liu, Kuan-Hsien; Chang, Ting-Chang; Chou, Wu-Ching; Chen, Hua-Mao; Tsai, Ming-Yen; Wu, Ming-Siou; Hung, Yi-Syuan; Hung, Pei-Hua; Hsieh, Tien-Yu; Tai, Ya-Hsiang; Chu, Ann-Kuo; Yeh, Bo-Liang

    2014-10-01

    This paper investigates abnormal dimension-dependent thermal instability in amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistors. Device dimension should theoretically have no effects on threshold voltage, except for in short channel devices. Unlike short channel drain-induced source barrier lowering effect, threshold voltage increases with increasing drain voltage. Furthermore, for devices with either a relatively large channel width or a short channel length, the output drain current decreases instead of saturating with an increase in drain voltage. Moreover, the wider the channel and the shorter the channel length, the larger the threshold voltage and output on-state current degradation that is observed. Because of the surrounding oxide and other thermal insulating material and the low thermal conductivity of the IGZO layer, the self-heating effect will be pronounced in wider/shorter channel length devices and those with a larger operating drain bias. To further clarify the physical mechanism, fast ID-VG and modulated peak/base pulse time ID-VD measurements are utilized to demonstrate the self-heating induced anomalous dimension-dependent threshold voltage variation and on-state current degradation.

  12. Temperature and layer thickness dependent in situ investigations on epindolidione organic thin-film transistors

    PubMed Central

    Lassnig, R.; Striedinger, B.; Jones, A.O.F.; Scherwitzl, B.; Fian, A.; Głowacl, E.D.; Stadlober, B.; Winkler, A.

    2016-01-01

    We report on in situ performance evaluations as a function of layer thickness and substrate temperature for bottom-gate, bottom-gold contact epindolidione organic thin-film transistors on various gate dielectrics. Experiments were carried out under ultra-high vacuum conditions, enabling quasi-simultaneous electrical and surface analysis. Auger electron spectroscopy and thermal desorption spectroscopy (TDS) were applied to characterize the quality of the substrate surface and the thermal stability of the organic films. Ex situ atomic force microscopy (AFM) was used to gain additional information on the layer formation and surface morphology of the hydrogen-bonded organic pigment. The examined gate dielectrics included SiO2, in its untreated and sputtered forms, as well as the spin-coated organic capping layers poly(vinyl-cinnamate) (PVCi) and poly((±)endo,exo-bicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic acid, diphenylester) (PNDPE, from the class of polynorbornenes). TDS and AFM revealed Volmer-Weber island growth dominated film formation with no evidence of a subjacent wetting layer. This growth mode is responsible for the comparably high coverage required for transistor behavior at 90–95% of a monolayer composed of standing molecules. Surface sputtering and an increased sample temperature during epindolidione deposition augmented the surface diffusion of adsorbing molecules and therefore led to a lower number of better-ordered islands. Consequently, while the onset of charge transport was delayed, higher saturation mobility was obtained. The highest, bottom-contact configuration, mobilities of approximately 2.5 × 10−3cm2/Vs were found for high coverages (50 nm) on sputtered samples. The coverage dependence of the mobility showed very different characteristics for the different gate dielectrics, while the change of the threshold voltage with coverage was approximately the same for all systems. An apparent decrease of the mobility with increasing coverage on the

  13. Molds and Resists Studies for Nanoimprint Lithography of Electrodes in Low-Voltage Polymer Thin-Film Transistors

    NASA Astrophysics Data System (ADS)

    Cavallari, Marco Roberto; Zanchin, Vinicius Ramos; Pojar, Mariana; Seabra, Antonio Carlos; de Assumpção Pereira-da-Silva, Marcelo; Fonseca, Fernando Josepetti; de Andrade, Adnei Melges

    2014-05-01

    A low-cost patterning of electrodes was investigated looking forward to replacing conventional photolithography for the processing of low-operating voltage polymeric thin-film transistors. Hard silicon, etched by sulfur hexafluoride and oxygen gas mixture, and flexible polydimethylsiloxane imprinting molds were studied through atomic force microscopy (AFM) and field emission gun scanning electron microscopy. The higher the concentration of oxygen in reactive ion etching, the lower the etch rate, sidewall angle, and surface roughness. A concentration around 30 % at 100 mTorr, 65 W and 70 sccm was demonstrated as adequate for submicrometric channels, presenting a reduced etch rate of 176 nm/min. Imprinting with positive photoresist AZ1518 was compared to negative SU-8 2002 by optical microscopy and AFM. Conformal results were obtained only with the last resist by hot embossing at 120 °C and 1 kgf/cm2 for 2 min, followed by a 10 min post-baking at 100 °C. The patterning procedure was applied to define gold source and drain electrodes on oxide-covered substrates to produce bottom-gate bottom-contact transistors. Poly(3-hexylthiophene) (P3HT) devices were processed on high-κ titanium oxynitride (TiO x N y ) deposited by radiofrequency magnetron sputtering over indium tin oxide-covered glass to achieve low-voltage operation. Hole mobility on micrometric imprinted channels may approach amorphous silicon (˜0.01 cm2/V s) and, since these devices operated at less than 5 V, they are not only suitable for electronic applications but also as sensors in aqueous media.

  14. Electrochromism and Electronic Structures of Nitrogen Doped Tungsten Oxide Thin Films Prepared by RF Reactive Sputtering

    NASA Astrophysics Data System (ADS)

    Nakagawa, Koichi; Miura, Noboru; Matsumoto, Setsuko; Nakano, Ryotaro; Matsumoto, Hironaga

    2008-09-01

    The doping effect of nitrogen on amorphous tungsten trioxide (a-WO3) thin films was investigated with regard to electrochromism and electronic structures. The N-doped thin films exhibit a change in electrochromic coloration from transparent yellow to black, whereas the un-doped thin films exhibit blue coloration. In addition, a new absorption peak related to nitrogen doping is observed at 2.3 eV in photoabsorption spectra during the electrochemical coloration/bleaching process. To explain these experimental results, the electronic structures of N-doped tungsten oxide were calculated by the DV-Xα molecular orbital method.

  15. Metal contact effect on the performance and scaling behavior of carbon nanotube thin film transistors

    NASA Astrophysics Data System (ADS)

    Xia, Jiye; Dong, Guodong; Tian, Boyuan; Yan, Qiuping; Zhang, Han; Liang, Xuelei; Peng, Lianmao

    2016-05-01

    Metal-tube contact is known to play an important role in carbon nanotube field-effect transistors (CNT-FETs) which are fabricated on individual CNTs. Less attention has been paid to the contact effect in network type carbon nanotube thin film transistors (CNT-TFTs). In this study, we demonstrate that contact plays an even more important role in CNT-TFTs than in CNT-FETs. Although the Schottky barrier height at the metal-tube contact can be tuned by the work function of the metal, similar to the case in CNT-FETs, the contact resistance (Rc) forms a much higher proportion of the total resistance in CNT-TFTs. Interestingly, the contact resistivity was found to increase with channel length, which is a consequence of the percolating nature of the transport in CNT films, and this behavior does not exist in CNT-FETs and normal 2D Ohmic conductors. Electrical transport in CNT-TFTs has been predicted to scale with channel length by stick percolation theory. However, the scaling behavior is also impacted, or even covered up by the effect of Rc. Once the contact effect is excluded, the covered scaling behavior can be revealed correctly. A possible way of reducing Rc in CNT-TFTs was proposed. We believe the findings in this paper will strengthen our understanding of CNT-TFTs, and even accelerate the commercialization of CNT-TFT technology.Metal-tube contact is known to play an important role in carbon nanotube field-effect transistors (CNT-FETs) which are fabricated on individual CNTs. Less attention has been paid to the contact effect in network type carbon nanotube thin film transistors (CNT-TFTs). In this study, we demonstrate that contact plays an even more important role in CNT-TFTs than in CNT-FETs. Although the Schottky barrier height at the metal-tube contact can be tuned by the work function of the metal, similar to the case in CNT-FETs, the contact resistance (Rc) forms a much higher proportion of the total resistance in CNT-TFTs. Interestingly, the contact

  16. Perovskite Oxide Thin Film Growth, Characterization, and Stability

    NASA Astrophysics Data System (ADS)

    Izumi, Andrew

    Studies into a class of materials known as complex oxides have evoked a great deal of interest due to their unique magnetic, ferroelectric, and superconducting properties. In particular, materials with the ABO3 perovskite structure have highly tunable properties because of the high stability of the structure, which allows for large scale doping and strain. This also allows for a large selection of A and B cations and valences, which can further modify the material's electronic structure. Additionally, deposition of these materials as thin films and superlattices through techniques such as pulsed laser deposition (PLD) results in novel properties due to the reduced dimensionality of the material. The novel properties of perovskite oxide heterostructures can be traced to a several sources, including chemical intermixing, strain and defect formation, and electronic reconstruction. The correlations between microstructure and physical properties must be investigated by examining the physical and electronic structure of perovskites in order to understand this class of materials. Some perovskites can undergo phase changes due to temperature, electrical fields, and magnetic fields. In this work we investigated Nd0.5Sr 0.5MnO3 (NSMO), which undergoes a first order magnetic and electronic transition at T=158K in bulk form. Above this temperature NSMO is a ferromagnetic metal, but transitions into an antiferromagnetic insulator as the temperature is decreased. This rapid transition has interesting potential in memory devices. However, when NSMO is deposited on (001)-oriented SrTiO 3 (STO) or (001)-oriented (LaAlO3)0.3-(Sr 2AlTaO6)0.7 (LSAT) substrates, this transition is lost. It has been reported in the literature that depositing NSMO on (110)-oriented STO allows for the transition to reemerge due to the partial epitaxial growth, where the NSMO film is strained along the [001] surface axis and partially relaxed along the [11¯0] surface axis. This allows the NSMO film enough

  17. Quasi one-dimensional transport in doped polythiophene and polythiophene thin film transistors

    NASA Astrophysics Data System (ADS)

    Yuen, Jonathan Dsu-Bei

    Conducting and semiconducting polymers are important materials in the development of printed, mechanically flexible, large area electronics for various applications, such as flat panel displays and photovoltaic cells. The development of conjugated polymers of high mobility for thin-film transistor active layers, in particular, has been very rapid, starting with early mobilities of around 10-4cm2/Vs to a recent report of 1cm 2/Vs in transistors with an active layer of poly(2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene) (PBTTT). Metallic behavior has a long history in the field of conjugated polymers and recently, even "true" metallic transport has been observed with drho/dT > 0. Thus, development of such high-mobility polymers also raises the possibility that similar behavior will also occur in such materials. A suitable candidate is PBTTT, which is a high performance, rigid-rod conjugated polymer that possesses a thermally-induced liquid crystalline phase where the polymer chains pack into stacked structures, forming two-dimensional layered terraces which extend laterally over hundreds of nanometers, contributing greatly to its high mobility. In this work, the electrical properties of PBTTT are studied under high charge densities both as the active layer in transistors and in electrochemically doped films, in order to determine the mechanism that governs its transport. This thesis will first describe the process of experimental setup and optimization required to produce high performance transistors and doped films; data derived from this is analyzed and correlated to suitable models that may describe charge behavior in these samples. We show that the data obtained using a wide range of parameters (temperature, gate-induced carrier density, source-drain voltage and doping level) scale onto the universal curve predicted for transport in a systems with electronic structure described by the Luttinger Liquid model, a one-dimensional "metallic" system where

  18. Synthesis and Applications of Titanium Oxide Nanotube Thin Films

    NASA Astrophysics Data System (ADS)

    Miyauchi, Masahiro; Tokudome, Hiromasa

    Layer-by-layer or vertically aligned TiO2 nanotube thin films were fabricated by using hydrothermally grown titanate nanotubes. These films were optically transparent and exhibited various functions. Layer-by-layer growth of TiO2 nanotubes on glass substrates was achieved by alternate layer deposition using an aqueous solution of colloidal titanate nanotubes and that of a polycation. These films exhibited photoinduced hydrophilic conversion, low-reflectivity, and significant electrochromism, owing to their unique one dimensional open-pore nanostructure. In addition, transparent thin films of vertically aligned TiO2 nanotube arrays were grown by a hydrothermal treatment of metal Ti thin film on glass substrates. These nanotube arrays were well adhered to the substrates and exhibited super-hydrophilicity even under the dark condition and the efficient electron field emission.

  19. Fully Solution-Processed Flexible Organic Thin Film Transistor Arrays with High Mobility and Exceptional Uniformity

    PubMed Central

    Fukuda, Kenjiro; Takeda, Yasunori; Mizukami, Makoto; Kumaki, Daisuke; Tokito, Shizuo

    2014-01-01

    Printing fully solution-processed organic electronic devices may potentially revolutionize production of flexible electronics for various applications. However, difficulties in forming thin, flat, uniform films through printing techniques have been responsible for poor device performance and low yields. Here, we report on fully solution-processed organic thin-film transistor (TFT) arrays with greatly improved performance and yields, achieved by layering solution-processable materials such as silver nanoparticle inks, organic semiconductors, and insulating polymers on thin plastic films. A treatment layer improves carrier injection between the source/drain electrodes and the semiconducting layer and dramatically reduces contact resistance. Furthermore, an organic semiconductor with large-crystal grains results in TFT devices with shorter channel lengths and higher field-effect mobilities. We obtained mobilities of over 1.2 cm2 V−1 s−1 in TFT devices with channel lengths shorter than 20 μm. By combining these fabrication techniques, we built highly uniform organic TFT arrays with average mobility levels as high as 0.80 cm2 V−1 s−1 and ideal threshold voltages of 0 V. These results represent major progress in the fabrication of fully solution-processed organic TFT device arrays. PMID:24492785

  20. Temperature-dependent charge injection and transport in pentacene thin-film transistors

    NASA Astrophysics Data System (ADS)

    Kim, Dong Wook; Shin, Hyunji; Park, Ji-Ho; Park, Jaehoon; Choi, Jong Sun

    2015-11-01

    The electrical characteristics of p-channel pentacene thin-film transistors (TFTs) were analyzed at different operating temperatures ranging from 253 to 353 K. An improvement in the drain current and field-effect mobility of the pentacene TFTs is observed with increasing temperature. From the Arrhenius plots of field-effect mobility extracted at various temperatures, a lower activation energy of 99.34 meV was obtained when the device is operating in the saturation region. Such observation is ascribed to the thermally activated hole transport through the pentacene grain boundaries. On the other hand, it was found that the Au/pentacene contact significantly affects the TFTs electrical characteristics in the linear region, which resulted in a higher activation energy. The activation energy based on the linear field-effect mobility, which increased from 344.61 to 444.70 meV with decreasing temperature, implies the charge-injection-limited electrical behavior of pentacene TFTs at low temperatures. The thermally induced electrical characteristic variations in pentacene TFTs can thus be studied through the temperature dependence of the charge injection and transport processes.

  1. Roll-printed organic thin-film transistor using patterned poly(dimethylsiloxane) (PDMS) stamp.

    PubMed

    Jo, Jeongdai; Yu, Jong-Su; Lee, Taik-Min; Kim, Dong-Soo; Kim, Kwang-Young

    2010-05-01

    The roll-printed gate, source, and drain electrodes of organic thin-film transistors (OTFTs) were fabricated by gravure printing or gravure-offset printing using patterned poly(dimethylsiloxane) (PDMS) stamp with various channel lengths and low-resistance silver (Ag) pastes on flexible 150 x 150 mm2 plastic substrates. Bottom-contact roll-printed OTFTs used polyvinylphenol (PVP) as polymeric dielectric and bis(triisopropyl-silylethynyl) pentacene (TIPS-pentacene) as organic semiconductor; they were formed by spin coating or ink-jetting. Depending on the choice of roll-printing method, the printed OTFTs obtained had a field-effect mobility of between 0.08 and 0.1 cm2/Vs, an on/off current ratio of between 10(4) and 10(5), and a subthreshold slope of between 1.96 and 2.32 V/decade. The roll-printing using patterned PDMS stamp and soluble processes made it possible to fabricate a printed OTFT with a channel length of between 12 to 74 microm on a plastic substrate; this was not previously possible using traditional printing techniques. The proposed fabrication process was 20 steps shorted than conventional fabrication techniques. PMID:20359007

  2. Vapor-phase-processed fluorinated self-assembled monolayer for organic thin-film transistors

    NASA Astrophysics Data System (ADS)

    Roh, Jeongkyun; Lee, Changhee; Kwak, Jeonghun; Jung, Byung Jun; Kim, Hyeok

    2015-09-01

    A vapor-phase-processed fluorinated silazane self-assembled monolayer (SAM), 1,3-bis(trifluoropropyl)-1,1,3,3-tetramethyldisilazane (FPDS), was introduced as a surface modifier for pentacene-based organic thin-film transistors (OTFTs). A remarkable improvement in the field effect mobility from 0.25 cm2/Vs (without SAM-treatment) to 0.42 cm2/Vs (with FPDS-treatment) was observed, which was attributed to the better pentacene growth on a hydrophobic surface. A significant reduction in the contact resistance was also observed by FPDS treatment due to the improved bulk conductivity and diminished charge trapping at the gate dielectric surface by the SAM treatment. In addition, FPDS treatment efficiently improved the bias stability of the OTFTs; the drain-to-source current degradation by the bias stress was greatly reduced from 80% to 50% by FPDS treatment, and the characteristic time for charge trapping of the FPDS treated OTFTs was approximately one order of magnitude larger than that of the OTFTs without SAM treatment.

  3. Effects of Au source/drain thickness on electrical characteristics of pentacene thin-film transistors

    NASA Astrophysics Data System (ADS)

    Kwon, Jin-Hyuk; Hahn, Joonku; Bae, Jin-Hyuk; Ham, Youngjin; Park, Jaehoon; Baang, Sungkeun

    2015-11-01

    We investigate the electrical characteristics of top-contact pentacene thin-film transistors (TFTs) fabricated with various thicknesses of the Au source and the drain (S/D) electrodes, i.e., 20, 30, 50, 70, and 105 nm. Pentacene TFTs exhibit enhancements in the drain current and the fieldeffect mobility with increasing thickness of Au S/D electrodes up to 50 nm, after which the TFT performance degrades with increasing Au thickness. A transmission line method is used to analyze the contact resistance between the Au electrode and the pentacene layer in the TFTs, and ultraviolet photoemission spectroscopy measurements are performed to determine the work function of the Au films. The lowest contact resistance, 73 kΩ·cm, is obtained for the 50-nm-thick Au case and is ascribed to the high work function (4.67 eV) of the film. Consequently, the effects of the Au S/D thickness on the performance of top-contact pentacene TFTs can be understood through the behavior of the charge injection at the Au electrode/pentacene interface.

  4. Thin film transistor based on TiOx prepared by DC magnetron sputtering.

    PubMed

    Chung, Sung Mook; Shin, Jae-Heon; Hong, Chan-Hwa; Cheong, Woo-Seok

    2012-07-01

    This paper reports on the thin film transistor (TFT) based on TiOx prepared by direct current (DC) magnetron sputtering for the application of n-type channel transparent TFTs. A ceramic TiOx target was prepared for the sputtering of the TiO2 films. The structural, optical, and electrical properties of the TiO2 films were investigated after their heat treatment. It is observed from XRD measurement that the TiO2 films show anatase structure having (101), (004), and (105) planes after heat treatment. The anatase-structure TiO2 films show a band-gap energy of approximately 3.20 eV and a transmittance of approximately 91% (@550 nm). The bottom-gate TFTs fabricated with the TiO2 film as an n-type channel layer. These devices exhibit the on-off ratio, the field-effect mobility, and the threshold voltage of about 10(4), 0.002 cm2/Vs, and 6 V, respectively. These results indicate the possibility of applying TiO2 films depositied by DC magnetron sputtering to TiO2-based opto-electronic devices. PMID:22966586

  5. Universal diffusion-limited injection and the hook effect in organic thin-film transistors.

    PubMed

    Liu, Chuan; Huseynova, Gunel; Xu, Yong; Long, Dang Xuan; Park, Won-Tae; Liu, Xuying; Minari, Takeo; Noh, Yong-Young

    2016-01-01

    The general form of interfacial contact resistance was derived for organic thin-film transistors (OTFTs) covering various injection mechanisms. Devices with a broad range of materials for contacts, semiconductors, and dielectrics were investigated and the charge injections in staggered OTFTs was found to universally follow the proposed form in the diffusion-limited case, which is signified by the mobility-dependent injection at the metal-semiconductor interfaces. Hence, real ohmic contact can hardly ever be achieved in OTFTs with low carrier concentrations and mobility, and the injection mechanisms include thermionic emission, diffusion, and surface recombination. The non-ohmic injection in OTFTs is manifested by the generally observed hook shape of the output conductance as a function of the drain field. The combined theoretical and experimental results show that interfacial contact resistance generally decreases with carrier mobility, and the injection current is probably determined by the surface recombination rate, which can be promoted by bulk-doping, contact modifications with charge injection layers and dopant layers, and dielectric engineering with high-k dielectric materials. PMID:27440253

  6. Evaluation of interface trap densities and quantum capacitance in carbon nanotube network thin-film transistors.

    PubMed

    Yoon, J; Choi, B; Choi, S; Lee, J; Lee, J; Jeon, M; Lee, Y; Han, J; Lee, J; Kim, D M; Kim, D H; Kim, S; Choi, S-J

    2016-07-22

    The interface trap density in single-walled carbon nanotube (SWNT) network thin-film transistors (TFTs) is a fundamental and important parameter for assessing the electronic performance of TFTs. However, the number of studies on the extraction of interface trap densities, particularly in SWNT TFTs, has been insufficient. In this work, we propose an efficient technique for extracting the energy-dependent interface traps in SWNT TFTs. From the measured dispersive, frequency-dependent capacitance-voltage (C-V) characteristics, the dispersive-free, frequency-independent C-V curve was obtained, thus enabling the extraction and analysis of the interface trap density, which was found to be approximately 8.2 × 10(11) eV(-1) cm(-2) at the valence band edge. The frequency-independent C-V curve also allows further extraction of the quantum capacitance in the SWNT network without introducing any additional fitting process or parameters. We found that the extracted value of the quantum capacitance in SWNT networks is lower than the theoretical value in aligned SWNTs due to the cross point of SWNTs on the SWNT network. Therefore, the method proposed in this work indicates that the C-V measurement is a powerful tool for obtaining deep physical insights regarding the electrical performance of SWNT TFTs. PMID:27285674

  7. Analytical and T-CAD modeling of pentacene thin-film transistors

    NASA Astrophysics Data System (ADS)

    Chen, Yet-Min; Chen, Yu-Sheng; Huang, Jian-Jang; Lee, Jiun-Haw; Wang, Yu-Wu; Wang, Yi-Kai

    2006-08-01

    Many researches report that the mobility in organic material is dependent on not only the gate field but also the grain size. There is also some evidence to prove that the gate length is strongly related to the carrier mobility. We construct both the analytical model of organic thin film transistor and the large signal circuit model designed by T-CAD to fit the measured I DS - V DS curves. We first apply basic I DS - V DS equations in both triode and saturation regions with mobility μ best fitted to measured I-V curves. The "best-fitted" μ increases with the gate length, and is related to the increase of total channel resistance due to the presence of small grains size of pentacene next to source/drain electrodes. We then use the Advanced Design System software to design the large signal circuit model. Similar to the MOSFET, we add the additional parameters to fit the I DS - V DS curves, ex: Rgd, Rgs, and Rp. Here, Rgd. With the circuit simulation, we find that Rgd presents the leakage current from gate to source, and it affects the slope of curves in the saturation region in the I DS - V DS curves. The equivalent circuit can fit the I DS - V DS curves very well with the proper parameter set.

  8. Flexible suspended gate organic thin-film transistors for ultra-sensitive pressure detection

    NASA Astrophysics Data System (ADS)

    Zang, Yaping; Zhang, Fengjiao; Huang, Dazhen; Gao, Xike; di, Chong-An; Zhu, Daoben

    2015-03-01

    The utilization of organic devices as pressure-sensing elements in artificial intelligence and healthcare applications represents a fascinating opportunity for the next-generation electronic products. To satisfy the critical requirements of these promising applications, the low-cost construction of large-area ultra-sensitive organic pressure devices with outstanding flexibility is highly desired. Here we present flexible suspended gate organic thin-film transistors (SGOTFTs) as a model platform that enables ultra-sensitive pressure detection. More importantly, the unique device geometry of SGOTFTs allows the fine-tuning of their sensitivity by the suspended gate. An unprecedented sensitivity of 192 kPa-1, a low limit-of-detection pressure of <0.5 Pa and a short response time of 10 ms were successfully realized, allowing the real-time detection of acoustic waves. These excellent sensing properties of SGOTFTs, together with their advantages of facile large-area fabrication and versatility in detecting various pressure signals, make SGOTFTs a powerful strategy for spatial pressure mapping in practical applications.

  9. High-performance thin-film transistors fabricated using excimer laser processing and grain engineering

    SciTech Connect

    Giust, G.K.; Sigmon, T.W.

    1998-04-01

    High-performance polysilicon thin-film transistors (TFT`s) are fabricated using an excimer laser to recrystallize the undoped channel and dope the source-drain regions. Using a technique the authors call grain engineering they are able to control grain microstructure using laser parameters. Resulting polysilicon films are obtained with average grain sizes of {approximately}4--9 {micro}m in sub-100 nm thick polysilicon films without substrate heating during the laser recrystallization process. Using a simple four-mask self-aligned aluminum top-gate structure, they fabricate TFT`s in these films. By combining the grain-engineered channel polysilicon regions with laser-doped source-drain regions, TFT`s are fabricated with electron mobilities up to 260 cm{sup 2}/Vs and on/off current ratios greater than 10{sup 7} To their knowledge, these devices represent the highest performance laser-processed TFT`s reported to date fabricated without substrate heating or hydrogenation.

  10. Evaluation of interface trap densities and quantum capacitance in carbon nanotube network thin-film transistors

    NASA Astrophysics Data System (ADS)

    Yoon, J.; Choi, B.; Choi, S.; Lee, J.; Lee, J.; Jeon, M.; Lee, Y.; Han, J.; Lee, J.; Kim, D. M.; Kim, D. H.; Kim, S.; Choi, S.-J.

    2016-07-01

    The interface trap density in single-walled carbon nanotube (SWNT) network thin-film transistors (TFTs) is a fundamental and important parameter for assessing the electronic performance of TFTs. However, the number of studies on the extraction of interface trap densities, particularly in SWNT TFTs, has been insufficient. In this work, we propose an efficient technique for extracting the energy-dependent interface traps in SWNT TFTs. From the measured dispersive, frequency-dependent capacitance–voltage (C–V) characteristics, the dispersive-free, frequency-independent C–V curve was obtained, thus enabling the extraction and analysis of the interface trap density, which was found to be approximately 8.2 × 1011 eV‑1 cm‑2 at the valence band edge. The frequency-independent C–V curve also allows further extraction of the quantum capacitance in the SWNT network without introducing any additional fitting process or parameters. We found that the extracted value of the quantum capacitance in SWNT networks is lower than the theoretical value in aligned SWNTs due to the cross point of SWNTs on the SWNT network. Therefore, the method proposed in this work indicates that the C–V measurement is a powerful tool for obtaining deep physical insights regarding the electrical performance of SWNT TFTs.

  11. A hybrid mask mould lithography scheme and its application in nanoscale organic thin film transistors

    NASA Astrophysics Data System (ADS)

    Cheng, Xing; Li, Dawen; Guo, L. Jay

    2006-02-01

    Nanoimprint lithography (NIL) has stimulated great interest in both academic research and industrial development due to its high resolution, high throughput and low cost advantages. Though NIL has been demonstrated to be very successful in replicating nanoscale features, it also has its limitations as a general lithography technique. Its fundamental moulding characteristics (i.e. physically displacing polymer materials) frequently lead to pattern defects when replicating arbitrary patterns, especially patterns with broad size distribution. To solve this problem, we have developed a combined nanoimprint and photolithography technique that uses a hybrid mould to achieve good pattern definitions. In this work, we applied this technique to fabricate finger-shaped nanoelectrodes, and demonstrated nanoscale pentacene organic thin film transistors (OTFTs). Methods of the hybrid mask-mould (HMM) fabrication and results on the device electrical characteristics are provided. With combined advantages of both photolithography and NIL, and the applicability to general nanoscale device and system fabrication, this method can become a valuable choice for low cost mass production of micro- and nanoscale structures, devices and systems.

  12. Highly Crystalline CVD-grown Multilayer MoSe2 Thin Film Transistor for Fast Photodetector

    PubMed Central

    Jung, Chulseung; Kim, Seung Min; Moon, Hyunseong; Han, Gyuchull; Kwon, Junyeon; Hong, Young Ki; Omkaram, Inturu; Yoon, Youngki; Kim, Sunkook; Park, Jozeph

    2015-01-01

    Hexagonal molybdenum diselenide (MoSe2) multilayers were grown by chemical vapor deposition (CVD). A relatively high pressure (>760 Torr) was used during the CVD growth to achieve multilayers by creating multiple nuclei based on the two-dimensional crystal growth model. Our CVD-grown multilayer MoSe2 thin-film transistors (TFTs) show p-type-dominant ambipolar behaviors, which are attributed to the formation of Se vacancies generated at the decomposition temperature (650 °C) after the CVD growth for 10 min. Our MoSe2 TFT with a reasonably high field-effect mobility (10 cm2/V · s) exhibits a high photoresponsivity (93.7 A/W) and a fast photoresponse time (τrise ~ 0.4 s) under the illumination of light, which demonstrates the practical feasibility of multilayer MoSe2 TFTs for photodetector applications. PMID:26477744

  13. Universal diffusion-limited injection and the hook effect in organic thin-film transistors

    PubMed Central

    Liu, Chuan; Huseynova, Gunel; Xu, Yong; Long, Dang Xuan; Park, Won-Tae; Liu, Xuying; Minari, Takeo; Noh, Yong-Young

    2016-01-01

    The general form of interfacial contact resistance was derived for organic thin-film transistors (OTFTs) covering various injection mechanisms. Devices with a broad range of materials for contacts, semiconductors, and dielectrics were investigated and the charge injections in staggered OTFTs was found to universally follow the proposed form in the diffusion-limited case, which is signified by the mobility-dependent injection at the metal-semiconductor interfaces. Hence, real ohmic contact can hardly ever be achieved in OTFTs with low carrier concentrations and mobility, and the injection mechanisms include thermionic emission, diffusion, and surface recombination. The non-ohmic injection in OTFTs is manifested by the generally observed hook shape of the output conductance as a function of the drain field. The combined theoretical and experimental results show that interfacial contact resistance generally decreases with carrier mobility, and the injection current is probably determined by the surface recombination rate, which can be promoted by bulk-doping, contact modifications with charge injection layers and dopant layers, and dielectric engineering with high-k dielectric materials. PMID:27440253

  14. Wafer scale fabrication of carbon nanotube thin film transistors with high yield

    NASA Astrophysics Data System (ADS)

    Tian, Boyuan; Liang, Xuelei; Yan, Qiuping; Zhang, Han; Xia, Jiye; Dong, Guodong; Peng, Lianmao; Xie, Sishen

    2016-07-01

    Carbon nanotube thin film transistors (CNT-TFTs) are promising candidates for future high performance and low cost macro-electronics. However, most of the reported CNT-TFTs are fabricated in small quantities on a relatively small size substrate. The yield of large scale fabrication and the performance uniformity of devices on large size substrates should be improved before the CNT-TFTs reach real products. In this paper, 25 200 devices, with various geometries (channel width and channel length), were fabricated on 4-in. size ridged and flexible substrates. Almost 100% device yield were obtained on a rigid substrate with high out-put current (>8 μA/μm), high on/off current ratio (>105), and high mobility (>30 cm2/V.s). More importantly, uniform performance in 4-in. area was achieved, and the fabrication process can be scaled up. The results give us more confidence for the real application of the CNT-TFT technology in the near future.

  15. Graphene-based electrodes for enhanced organic thin film transistors based on pentacene.

    PubMed

    Basu, Sarbani; Lee, Mu Chen; Wang, Yeong-Her

    2014-08-21

    This paper presents 6,13-bis(triisopropylsilylethynyl)pentacene (TIPS-pentacene) and pentacene-based organic thin film transistors (OTFTs) with monolayer graphene source-drain (S-D) electrodes. The electrodes are patterned using conventional photolithographic techniques combined with reactive ion etching. The monolayer graphene film grown by chemical vapor deposition on Cu foil was transferred on a Si dioxide surface using a polymer-supported transfer method to fabricate bottom-gate, bottom-contact OTFTs. The pentacene OTFTs with graphene S-D contacts exhibited superior performance with a mobility of 0.1 cm(2) V(-1) s(-1) and an on-off ratio of 10(5) compared with OTFTs with Au-based S-D contacts, which had a mobility of 0.01 cm(2) V(-1) s(-1) and an on-off ratio of 10(3). The crystallinity, grain size, and microscopic defects (or the number of layers of graphene films) of the TIPS-pentacene/pentacene films were analyzed by X-ray diffraction spectroscopy, atomic force microscopy, and Raman spectroscopy, respectively. The feasibility of using graphene as an S-D electrode in OTFTs provides an alternative material with high carrier injection efficiency, chemical stability, and excellent interface properties with organic semiconductors, thus exhibiting improved device performance of C-based electronic OTFTs at a reduced cost. PMID:25000388

  16. Sensitivity of the threshold voltage of organic thin-film transistors to light and water

    SciTech Connect

    Feng, Cong; Marinov, Ognian; Deen, M. Jamal; Selvaganapathy, Ponnambalam Ravi; Wu, Yiliang

    2015-05-14

    Analyses of extensive experiments with organic thin-film transistors (OTFTs) indicate that the threshold voltage V{sub T} of an OTFT has a temporal differential sensitivity. In particular, V{sub T} changes initially by changing the light illumination intensity or making/removing a contact of water with the organic semiconductor. Keeping the conditions stationary, then the initial shift of V{sub T} diminishes, since the time dependence of V{sub T} gradually recovers the OTFT to the state before applying the change in the environmental conditions. While still causing a differential and time-variant shift of V{sub T}, the deionized water does not have a dramatic impact on OTFTs that use the polymer DKPP-βT (diketopyrrolopyrrole β-unsubstituted quaterthiophene) as the active semiconductor material. Observations for the impact of water are made from experiments with an OTFT that has a microfluidic channel on the top the electrical channel, with the water in the microfluidic channel in direct contact with the electrical channel of the OTFT. This arrangement of electrical and microfluidic channels is a novel structure of the microfluidic OTFT, suitable for sensing applications of liquid analytes by means of organic electronics.

  17. Low temperature atomic layer deposited ZnO photo thin film transistors

    SciTech Connect

    Oruc, Feyza B.; Aygun, Levent E.; Donmez, Inci; Biyikli, Necmi; Okyay, Ali K.; Yu, Hyun Yong

    2015-01-01

    ZnO thin film transistors (TFTs) are fabricated on Si substrates using atomic layer deposition technique. The growth temperature of ZnO channel layers are selected as 80, 100, 120, 130, and 250 °C. Material characteristics of ZnO films are examined using x-ray photoelectron spectroscopy and x-ray diffraction methods. Stoichiometry analyses showed that the amount of both oxygen vacancies and interstitial zinc decrease with decreasing growth temperature. Electrical characteristics improve with decreasing growth temperature. Best results are obtained with ZnO channels deposited at 80 °C; I{sub on}/I{sub off} ratio is extracted as 7.8 × 10{sup 9} and subthreshold slope is extracted as 0.116 V/dec. Flexible ZnO TFT devices are also fabricated using films grown at 80 °C. I{sub D}–V{sub GS} characterization results showed that devices fabricated on different substrates (Si and polyethylene terephthalate) show similar electrical characteristics. Sub-bandgap photo sensing properties of ZnO based TFTs are investigated; it is shown that visible light absorption of ZnO based TFTs can be actively controlled by external gate bias.

  18. Universal diffusion-limited injection and the hook effect in organic thin-film transistors

    NASA Astrophysics Data System (ADS)

    Liu, Chuan; Huseynova, Gunel; Xu, Yong; Long, Dang Xuan; Park, Won-Tae; Liu, Xuying; Minari, Takeo; Noh, Yong-Young

    2016-07-01

    The general form of interfacial contact resistance was derived for organic thin-film transistors (OTFTs) covering various injection mechanisms. Devices with a broad range of materials for contacts, semiconductors, and dielectrics were investigated and the charge injections in staggered OTFTs was found to universally follow the proposed form in the diffusion-limited case, which is signified by the mobility-dependent injection at the metal-semiconductor interfaces. Hence, real ohmic contact can hardly ever be achieved in OTFTs with low carrier concentrations and mobility, and the injection mechanisms include thermionic emission, diffusion, and surface recombination. The non-ohmic injection in OTFTs is manifested by the generally observed hook shape of the output conductance as a function of the drain field. The combined theoretical and experimental results show that interfacial contact resistance generally decreases with carrier mobility, and the injection current is probably determined by the surface recombination rate, which can be promoted by bulk-doping, contact modifications with charge injection layers and dopant layers, and dielectric engineering with high-k dielectric materials.

  19. Flexible suspended gate organic thin-film transistors for ultra-sensitive pressure detection

    PubMed Central

    Zang, Yaping; Zhang, Fengjiao; Huang, Dazhen; Gao, Xike; Di, Chong-an; Zhu, Daoben

    2015-01-01

    The utilization of organic devices as pressure-sensing elements in artificial intelligence and healthcare applications represents a fascinating opportunity for the next-generation electronic products. To satisfy the critical requirements of these promising applications, the low-cost construction of large-area ultra-sensitive organic pressure devices with outstanding flexibility is highly desired. Here we present flexible suspended gate organic thin-film transistors (SGOTFTs) as a model platform that enables ultra-sensitive pressure detection. More importantly, the unique device geometry of SGOTFTs allows the fine-tuning of their sensitivity by the suspended gate. An unprecedented sensitivity of 192 kPa−1, a low limit-of-detection pressure of <0.5 Pa and a short response time of 10 ms were successfully realized, allowing the real-time detection of acoustic waves. These excellent sensing properties of SGOTFTs, together with their advantages of facile large-area fabrication and versatility in detecting various pressure signals, make SGOTFTs a powerful strategy for spatial pressure mapping in practical applications. PMID:25872157

  20. Flexible pH sensors based on polysilicon thin film transistors and ZnO nanowalls

    NASA Astrophysics Data System (ADS)

    Maiolo, L.; Mirabella, S.; Maita, F.; Alberti, A.; Minotti, A.; Strano, V.; Pecora, A.; Shacham-Diamand, Y.; Fortunato, G.

    2014-09-01

    A fully flexible pH sensor using nanoporous ZnO on extended gate thin film transistor (EGTFT) fabricated on polymeric substrate is demonstrated. The sensor adopts the Low Temperature Polycrystalline Silicon (LTPS) TFT technology for the active device, since it allows excellent electrical characteristics and good stability and opens the way towards the possibility of exploiting CMOS architectures in the future. The nanoporous ZnO sensitive film, consisting of very thin (20 nm) crystalline ZnO walls with a large surface-to-volume ratio, was chemically deposited at 90 °C, allowing simple process integration with conventional TFT micro-fabrication processes compatible with wide range of polymeric substrates. The pH sensor showed a near-ideal Nernstian response (˜59 mV/pH), indicating an ideality factor α ˜ 1 according to the conventional site binding model. The present results can pave the way to advanced flexible sensing systems, where sensors and local signal conditioning circuits will be integrated on the same flexible substrate.