Anodization for Simplified Processing and Efficient Charge Transport in Vertical Organic Field‐Effect Transistors

Vertical organic transistors are an attractive alternative to realize short channel transistors, which are required for powerful electronic devices and flexible electronic circuits operating at high frequencies. Unfortunately, the vertical device architecture comes along with an increased device fabrication complexity, limiting the potential of this technology for application. A new design of vertical organic field‐effect transistors (VOFETs) with superior electrical performance and simplified processing is reported. By using electrochemical oxidized aluminum oxide (AlO_x) as a pseudo self‐aligned charge‐blocking structure in vertical organic transistors, direct leakage current between the source and drain can be effectively suppressed, enabling VOFETs with very low off‐current levels despite the short channel length. The anodization technique is easy to apply and can be surprisingly used on both n‐type and p‐type organic semiconductor thin films with significant signs of degradation. Hence, the anodization technique enables a simplified process of high‐performance p‐type and n‐type VOFETs, paving the road toward complementary circuits made of vertical transistors.     

A vertically periodic defected ground structure and its application in reducing the size of microwave circuits

The microstrip and coplanar waveguide transmission lines combined by a vertically periodic defected ground structure (VPDGS) are proposed. The slow-wave effect, equivalent circuit, and the performances are shown. As an application example, VPDGS is adopted in the matching networks of an amplifier for size-reduction. Two series microstrip lines in input and output matching networks of the amplifier are reduced to 38.5% and 44.4% of the original lengths, respectively, due to the increased slow-wave effects, while the amplifier performances are preserved.     

A compact LTCC-based Ku-band transmitter module

Presents design, implementation, and measurement of a three-dimensional (3-D)-deployed RF front-end system-on-package (SOP) in a standard multi-layer low temperature co-fired ceramic (LTCC) technology. A compact 14 GHz GaAs MESFET-based transmitter module integrated with an embedded bandpass filter was built on LTCC 951AT tapes. The up-converter MMIC integrated with a voltage controlled oscillator (VCO) exhibits a measured up-conversion gain of 15 dB and an IIP3 of 15 dBm, while the power amplifier (PA) MMIC shows a measured gain of 31 dB and a 1-dB compression output power of 26 dBm at 14 GHz. Both MMICs were integrated on a compact LTCC module where an embedded front-end band pass filter (BPF) with a measured insertion loss of 3 dB at 14.25 GHz was integrated. The transmitter module is compact in size (400 /spl times/ 310 /spl times/ 35.2 mil/sup 3/), however it demonstrated an overall up-conversion gain of 41 dB, and available data rate of 32 Mbps with adjacent channel power ratio (ACPR) of 42 dB. These results suggest the feasibility of building highly SOP integrated RF front ends for microwave and millimeter wave applications.     

Ultra-wideband (from DC to 110 GHz) CPW to CPS transition

A new ultra-wideband, low-loss and small-size coplanar waveguide (CPW) to coplanar strip (CPS) transition which can be used from DC to 110 GHz is presented. The proposed transition connects CPW with CPS by the reformed air-bridge. Two ground planes of CPW are tied at their ends by a line and the centre of the line is connected to the ground strip of CPS by another line. Owing to the symmetry of the proposed structure, the currents of two ground planes of CPW are combined with the same phase and transferred to the ground strip of CPS. With height of 3 μm, the signal line of CPW passes over two connecting lines and is connected to the signal strip of CPS. For the back-to-back transition structure, insertion loss <1 dB and return loss >15 dB are obtained from 0.5 to 110 GHz     

Highly Stretchable or Transparent Conductor Fabrication by a Hierarchical Multiscale Hybrid Nanocomposite

As is frequently seen in sci‐fi movies, future electronics are expected to ultimately be in the form of wearable electronics. To realize wearable electronics, the electric components should be soft, flexible, and even stretchable to be human‐friendly. An important step is presented toward realization of wearable electronics by developing a hierarchical multiscale hybrid nanocomposite for highly flexible, stretchable, or transparent conductors. The hybrid nanocomposite combines the enhanced mechanical compliance, electrical conductivity, and optical transparency of small CNTs (d ≈ 1.2 nm) and the enhanced electrical conductivity of relatively bigger Ag nanowire (d ≈ 150 nm) backbone to provide efficient multiscale electron transport path with Ag nanowire current backbone collector and local CNT percolation network. The highly elastic hybrid nanocomposite conductors and highly transparent flexible conductors can be mounted on any non‐planar or soft surfaces to realize human‐friendly electronics interface for future wearable electronics.     

Detection of microorganisms and toxins with evanescent wave fiber-optic biosensors

Conventional procedures to detect microorganisms and toxins in food, water, and human specimens can take hours or days to perform and may provide inconclusive identification. The complex nature of many sample matrices as well as the presence of particulate matter in samples often severely reduces the sensitivity and specificity of conventional bacterial detection systems, especially those that rely on immunological reactions for capture or detection. Evanescent wave fiber-optic biosensors can identify such target analytes in minutes directly from complex matrix samples using robust antibody-based assays, significantly improving the detection sensitivity, selectivity, and speed. In addition, live microbial targets can be recovered from fiber-optic waveguides to determine microorganism viability, confirm identification, and preserve as evidence.     

Single-Chip Eye Tracker Using Smart CMOS Image Sensor Pixels

The eye tracker is a system that detects the point where the user gazes on. The conventional eye tracker using a Charge-Coupled Device (CCD) camera needs many peripherals and software computation causing high cost, computation time and power consumption. This paper proposes a single-chip eye tracker using smart CMOS Image Sensor (CIS) pixels. The proposed eye tracker does not require additional peripherals and operates at higher speed than the conventional approach. The prototype chip was designed and fabricated for a 32 × 32 smart CIS pixels array with a 0.35-μ m CMOS process. The test results show ± 1 pixel error at the rate of 125 frame-per-second. The power consumption is 260 mW with 3.3 V supply voltage and the silicon area is 3.8 mm²     

Significantly Enhanced Photoluminescence of Doped Polymer‐Metal Hybrid Nanotubes

We report on the significantly enhanced photoluminescence (PL) of hybrid double‐layered nanotubes (HDLNTs) consisting of poly(3‐methylthiophene) (P3MT) nanotubes with various doping levels enveloped by an inorganic, nickel (Ni) metal nanotube. From laser confocal microscopy PL experiments on a single strand of the doped‐P3MT nanotubes and of their HDLNTs, the PL peak intensity of the HDLNT systems increased remarkably up to ～350 times as the doping level of the P3MT nanotubes of the HDLNTs increased, which was confirmed by measurements of the quantum yield. In a comparison of the normalized ultraviolet and visible absorption spectra of the doped‐P3MT nanotubes and their HDLNTs, new absorption peaks corresponding to surface‐plasmon (SP) energy were created at 563 and 615 nm after the nanoscale Ni metal coating onto the P3MT nanotubes, and their intensity increased on increasing the doping level of the P3MT nanotube. The doping‐induced bipolaron peaks of the HDLNTs of doped‐P3MT/Ni were relatively reduced, compared with those of the doped‐P3MT nanotubes before the Ni coating, due to the charge‐transfer effect in the SP‐resonance (SPR) coupling. Both energy‐transfer and charge‐transfer effects due to SP resonance contributed to the very‐large enhancement of the PL efficiency of the doped‐P3MT‐based HDLNTs.     

Forecasting Winning Bid Prices on an Online Auction Market - Data Mining Approaches -

To solve information asymmetry problem on online auction, this study suggests and validates a forecasting model of winning bid prices. Especially, it explores the usability of data mining approaches, such as neural network and Bayesian network in building a forecasting model. This research empirically shows that, in forecasting winning bid prices on online auction, data mining techniques have showed better performance than traditional statistical analysis, such as logistic regression and multivariate regression.     

Highly Concentrated and Conductive Reduced Graphene Oxide Nanosheets by Monovalent Cation–π Interaction: Toward Printed Electronics

A novel route to preparing highly concentrated and conductive reduced graphene oxide (RGO) in various solvents by monovalent cation–π interaction. Previously, the hydrophobic properties of high‐quality RGO containing few defects and oxygen moieties have precluded the formation of stable dispersion in various solvents. Cation–π interaction between monovalent cations, such as Na⁺ or K⁺, and six‐membered sp² carbons on graphene were achieved by simple aging process of graphene oxide (GO) nanosheets dispersed in alkali solvent. The noncovalent binding forces introduced by the cation–π interactions were evident from the chemical shift of the sp² peak in the solid ¹³C NMR spectra. Raman spectra and the I‐V characteristics demonstrated the interactions in terms of the presence of n‐type doping effect due to the adsorption of cations with high electron mobility (39 cm²/Vs). The RGO film prepared without a post‐annealing process displayed superior electrical conductivity of 97,500 S/m at a thickness of 1.7 μm. Moreover, mass production of GO paste with a concentration as high as 20 g/L was achieved by accelerating the cation–π interactions with densification process. This strategy can facilitate the development of large scalable production methods for preparing printed electronics made from high‐quality RGO nanosheets.