National Nano Device Laboratories

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Wu H.-C.,National Chiao Tung University | Chien C.-H.,National Chiao Tung University | Chien C.-H.,National Nano Device Laboratories
Applied Physics Letters | Year: 2013

This work demonstrates In-Ga-Zn-O (IGZO) as source and drain electrodes in IGZO-thin film transistors (TFTs). The fabricated TFT depicts excellent electrical properties; its mobility is 18.02 (cm2/V s), threshold voltage (Vth) is 0.3 (V), on/off ratio is 1.63 × 108 and subthreshold swing (S.S.) is 239 (mV/decade). We find using rapid thermal annealing treatment can convert IGZO into an effective conductor, and the transparency of IGZO remained almost unchanged. We also find sufficient thermal budget is needed for getting stable transfer curve and output characteristic; otherwise, current fluctuation in on-state can be easily observed. With IGZO electrodes, fully transparent IGZO-TFTs can be thus realized on a glass substrate. © 2013 American Institute of Physics.


Teng L.-F.,National Chiao Tung University | Liu P.-T.,National Chiao Tung University | Lo Y.-J.,National Chiao Tung University | Lee Y.-J.,National Nano Device Laboratories
Applied Physics Letters | Year: 2012

By using microwave annealing technology instead of thermal furnace annealing, this work elucidates the electrical characteristics of amorphous InGaZnO thin film transistor (a-IGZO TFT) with a carrier mobility of 13.5cm 2/Vs, threshold voltage of 3.28V, and subthreshold swing of 0.43V/decade. This TFT performance with microwave annealing of 100s is well competitive with its counterpart with furnace annealing at 450°C for 1h. A physical mechanism for the electrical improvement is also deduced. Owing to its low thermal budget and selective heating to materials of interest, microwave annealing is highly promising for amorphous oxide in semiconductor TFT manufacturing. © 2012 American Institute of Physics.


Kuo Y.-Y.,National Chiao Tung University | Chien C.-H.,National Chiao Tung University | Chien C.-H.,National Nano Device Laboratories
Electrochimica Acta | Year: 2013

A sinter-free method to transfer anodized TiO2 nanotube-arrays to a polyethylene terephthalate (PET) sheet is proposed. Since the anodized nanotube-array was crystallized independently before transferring to the PET, the internal charge transport resistance and the charge recombination rate are unchanged for the nanotubes on the PET sheet, and no high temperature sintering process is required. With hydrothermal treatment, the dye sensitized solar cell fabricated utilizing a low temperature bonded nanotube/PET as a photoelectrode exhibits a power conversion efficiency of 5.41%, which is only 0.87% lower than the power conversion efficiency of the solar cell using nanotubes bonded on a conductive glass through high temperature processes. © 2013 Elsevier Ltd. All rights reserved.


Nolen C.M.,National Nano Device Laboratories | Denina G.,University of California at Riverside | Teweldebrhan D.,National Nano Device Laboratories | Bhanu B.,University of California at Riverside | Balandin A.A.,National Nano Device Laboratories
ACS Nano | Year: 2011

Practical applications of graphene require a reliable high-throughput method of graphene identification and quality control, which can be used for large-scale substrates and wafers. We have proposed and experimentally tested a fast and fully automated approach for determining the number of atomic planes in graphene samples. The procedure allows for in situ identification of the borders of the regions with the same number of atomic planes. It is based on an original image processing algorithm, which utilizes micro-Raman calibration, light background subtraction, lighting nonuniformity correction, and the color and grayscale image processing for each pixel. The outcome of the developed procedure is a pseudo color map, which marks the single-layer and few-layer graphene regions on the substrate of any size that can be captured by an optical microscope. Our approach works for various substrates and can be applied to mechanically exfoliated, chemically derived, deposited or epitaxial graphene on an industrial scale. © 2011 American Chemical Society.


Bai S.-N.,Chienkuo Technical University | Wu S.-C.,National Nano Device Laboratories
Journal of Materials Science: Materials in Electronics | Year: 2011

Zinc oxide (ZnO) nanowires with various morphologies are synthesized by the hydrothermal method on silicon substrates coated with ZnO thin films. The ZnO films are used as the seed layer and are prepared using the sol-gel technique. Experimental results demonstrate that the synthesis of ZnO nanowires is dependent on the crystalline properties of the ZnO seed-layer films. Sol concentration is the controlled parameter for the preparation of ZnO seed-layer films in this study. The ZnO films are found to have the hexagonal wurtzite structure with highly preferred growth along the c-axis at suitable sol concentrations. The vertically aligned ZnO nanowire arrays on the substrates are believed to be the result of the epitaxial growth of the ZnO seed layer. Scanning electron microscopy shows that nanowires with uniform distribution in length, diameter, and density are obtained. X-ray diffraction patterns clearly reveal that the ZnO nanowires are primarily grown along the c-axis direction. Transmission electron microscopy and selected-area electron diffraction measurements show that the nanowires have good crystalline properties. The well-aligned and high surface areas of the ZnO nanowires make them a potential candidate for applications in solar cells, field emission devices, and ultra-sensitive gas sensors. © 2010 Springer Science+Business Media, LLC.


Lu M.-P.,National Nano Device Laboratories | Lu M.-Y.,National Chung Cheng University | Chen L.-J.,National Tsing Hua University
Advanced Functional Materials | Year: 2014

Persistent challenges in the nanofabrication of optoelectronic memory elements with ready size-scalability, multibit data storage, and ultralow optical writing energy have limited progress toward the construction of optical data storage/buffering elements in high-density photonic-electronic circuits. Here, a multibit programmable optoelectronic nanowire (NW) memory is described that operates with an ultralow optical writing energy [ca. 180 aJ bit -1 (ca. 330 photons bit-1)] and a low standby power consumption (<1 pW) at room temperature. In this system, photoionized charged defects behave as surface trapped charges to achieve the electrical memory effect. As a result of the high surface electric field, the rate of dissociation of the photoexcited charge is amplified, thereby decreasing the optical writing energy. Moreover, the extremely high dynamic photoconductive gain (ca. 10 10) makes it possible to write multibit optical data bit-by-bit into the NW. These findings should open new opportunities in next-generation multifunctional nanochips for optical data storage/buffering, optical data processing, and optical sensing purposes. A multibit programmable optoelectronic nanowire (NW) memory operates with an ultralow optical writing energy (ca. 330 photons bit-1) at room temperature. In this system, photoionized charged defects behave as surface trapped charges to achieve the electrical memory effect. The extremely high dynamic photoconductive gain (ca. 10 10) makes it possible to write multibit optical data bit-by-bit into the NW. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Lu M.-P.,National Nano Device Laboratories
Physical Review B - Condensed Matter and Materials Physics | Year: 2012

Charges trapped in the gate dielectric and acting as long-range scatterers can have a significant effect on carrier transport in graphene-based nanodevices. In this study, we theoretically investigated the charge capture kinetics of short-distance channel-defect interactions in graphene nanoribbon nanodevices by employing the nonradiative multiphonon theory in conjunction with the Coulomb energy (ΔE). The peaks that emerged from the electron capture rate strongly correlated with the singularity characteristics of a one-dimensional (1D) density of states. Furthermore, we elaborate herein on how the value of ΔE plays a decisive role in determining the capture kinetics for the trapping of channel carriers in the interface dielectric defects in 1D nanodevices. © 2012 American Physical Society.


Hsueh T.-J.,National Nano Device Laboratories | Shieh J.-M.,National Nano Device Laboratories | Yeh Y.-M.,National Nano Device Laboratories
Progress in Photovoltaics: Research and Applications | Year: 2015

A green energy device with a CuInGaSe2 (CIGS) photovoltaic (PV) cell covered with a passive light-trapping structure (ZnO nanowires (NWs)) and connected to an active energy-harvesting device (thermoelectric generator (TEG)) is presented. The efficiency of the ZnO NWs/CIGS PV device obtained using a deposition temperature of 550 C and Cd-free processes reaches 16.5%. The series-connected CIGS PV cell with a TEG had a record-high efficiency of 22% at a cool-side temperature (Tc) below 5 C. The open-circuit voltage (Voc) of the hybrid CIGS PV/TEG device was increased from 0.64 to 0.85 V. This technology has potential for high-efficiency energy-harvesting applications. Copyright © 2014 John Wiley & Sons, Ltd.


Hong C.-C.,National Tsing Hua University | Huang S.-Y.,National Tsing Hua University | Shieh J.,National United University | Chen S.-H.,National Nano Device Laboratories
Macromolecules | Year: 2012

In this paper, sub-20 nm ferroelectric PVDF-TrFE copolymer nanograss structures with aspect ratios up to 8.9 were developed. This study demonstrated sub-20 nm PVDF-TrFE nanograss structures that are nanoimprinted using a silicon nanograss mold in a single step. Vertically oriented PVDF-TrFE nanopillars were poled using the developed flip-stacking poling method. According to the PFM measurements, the piezoelectricity of flat thin films fabricated in this work reaches 14.0 pm/V. The maximum output voltage of the single PVDF-TrFE nanopillar was 526 mV, and the maximum piezoelectricity of the single PVDF-TrFE nanopillar was 210.4 pm/V. The piezoelectricity of the developed PVDF-TrFE nanograss structures was 5.19 times larger than that of the PVDF-TrFE flat thin films. The developed technique is simple, economical, and easy to fabricate. The developed ferroelectric PVDF-TrFE copolymer nanograss structures, which showed enhanced piezoelectricity compared to the PVDF-TrFE flat thin films, have potential applications in nanotip-based protein biosensors, nanotip-based tactile sensors, and power nanogenerators. © 2012 American Chemical Society.


Cheng C.-L.,National formosa University | Yang J.-Y.,National Nano Device Laboratories
IEEE Electron Device Letters | Year: 2012

Crisscrossed Eu 3+-doped Y(OH) 3 nanotubes spin cast on the front surface of the screen-printed monocrystalline silicon solar cells (SPMSSCs) have been fabricated to enhance the conversion efficiency (CE) of the SPMSSCs. Organic-solvent-dispersible Eu 3+-doped Y(OH) 3 nanotubes were hydrothermally synthesized according to the modified liquid-solid-solution synthetic strategy. Intense and well-resolved photoluminescent lines in the range of 525-700 nm are observed from the Eu 3+-doped Y(OH) 3 nanotubes. The achievement of a CE improvement of more than 2% absolute from 15.2% to 17.2% in the SPMSSCs with Eu 3+-doped Y(OH) 3 nanotubes was explored. © 2012 IEEE.

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