Study on Characteristics of Various RF Transmission Line Structures on PES Substrate for Application to Flexible MMIC

In this work, the coplanar waveguide is fabricated on a PES (poly[ether sulfone]) substrate for application to a flexible monolithic microwave integrated circuit, and its RF characteristics were thoroughly investigated. The quality factor of the coplanar waveguide on PES is 40.3 at a resonance frequency of 46.7 GHz. A fishbone‐type transmission line (FTTL) structure is also fabricated on the PES substrate, and its RF characteristics are investigated. The wavelength of the FTTL on PES is 5.11 mm at 20 GHz, which is 55% of the conventional coplanar waveguide on PES. Using the FTTL, an impedance transformer is fabricated on PES. The size of the impedance transformer is 0.318 mm × 0.318 mm, which is 69.2% of the size of the transformer fabricated by the conventional coplanar waveguide on PES. The impedance transformer showed return loss values better than –12.9 dB from 5 GHz to 50 GHz and an insertion loss better than –1.13 dB in the same frequency range.     

High current conduction with high mobility by non-radiative charge recombination interfaces in organic semiconductor devices

We report a unique non-radiative p-n-p junction structure to provide high current conduction with high mobility in organic semiconductor devices. The current conduction was improved by increasing p-n junctions made with intrinsic p-type hole transport layer and n-type electron transport layer. The excellent hole mobility of 5.3 × 10^?1 cm²/V s in this p-n-p device configuration is measured by the space charge limited current method with an electric field of 0.3 MV/cm. Enhanced current conduction of 248% at 4.0 V was observed in fluorescent blue organic light-emitting diodes with introduction of non-radiative p-n-p-n-p junction interfaces. Thereupon, the power efficiency at 1000 cd/m² was improved by 22% and the driving voltage also was reduced by 17%, compared to that of no interface device. Such high current conduction with high mobility is attributed to the carrier recombination at p-n-p interfaces through coulombic interaction. This non-radiative p-n-p junction structure suggested in this report can be very useful for many practical organic semiconductor device applications.     

Optimized contrast enhancement for real-time image and video dehazing

A fast and optimized dehazing algorithm for hazy images and videos is proposed in this work. Based on the observation that a hazy image exhibits low contrast in general, we restore the hazy image by enhancing its contrast. However, the overcompensation of the degraded contrast may truncate pixel values and cause information loss. Therefore, we formulate a cost function that consists of the contrast term and the information loss term. By minimizing the cost function, the proposed algorithm enhances the contrast and preserves the information optimally. Moreover, we extend the static image dehazing algorithm to real-time video dehazing. We reduce flickering artifacts in a dehazed video sequence by making transmission values temporally coherent. Experimental results show that the proposed algorithm effectively removes haze and is sufficiently fast for real-time dehazing applications.     

Enhanced carrier mobility and photon-harvesting property by introducing Au nano-particles in bulk heterojunction photovoltaic cells

In this study, polymer solar cells (PSCs) doped with Au nanoparticles (Au NPs) were successfully fabricated to maximize the photon-harvesting properties on the photoactive layer. In addition, a conductivity-enhanced hybrid buffer layer was introduced to improve the photon absorption properties and effectively separate the generated charges by adding Au NPs and dimethylsulfoxide (DMSO) to the PH 500 as a buffer layer. The PSC performance was optimized with a 88% improvement over the conventional PSCs (photoactive area: 225 mm², power conversion efficiency (PCE): 3.2%) by the introduction to the buffer layer of Au NPs and DMSO at 10 wt% and 1.0 wt%, respectively, and with 15 wt% Au NP doping in the photoactive layer. The internal resistance was decreased due to the increased photocurrent caused by the localized surface plasmon resonance (LSPR) effect of the Au NPs in the photoactive layer and by the improvement of carrier mobility induced by the DMSO doping of the buffer layer. As a result, the series resistance (R_S) deceased from 42.3 to 19.7 Ω cm² while the shunt resistance (R_SH) increased from 339 to 487 Ω cm².     

Skew correction of business card images acquired in PDA

An efficient algorithm for rotational skew correction of business card images acquired in a PDA (personal digital assistant) camera is presented. The proposed method is composed of four parts: block adaptive binarisation (BAB), stripe generation, skew angle calculation and image rotation. In BAB, an input image is binarised block by block so as to lessen the effects of irregular illumination and shadow over the input image. In stripe generation, character string clusters are generated merging adjacent characters and their strings, and then only clusters useful for skew angle calculation are output as stripes. In skew angle calculation, the direction angles of the stripes are calculated using their central moments and then the skew angle of the input image is determined averaging the direction angles. In image rotation, the input image is rotated by the skew angle. Experimental results show that the proposed method yields root mean square error of 0.44/spl deg/ for test images of several types of business cards acquired by a PDA under various surrounding conditions.     

A high efficiency transmitter and receiver for magnetic resonant wireless battery charging system in 0.35 μm BCD

This paper presents a transmitter and receiver for magnetic resonant wireless battery charging system. In the receiver, a wide-input range CMOS multi-mode active rectifier is proposed for a magnetic resonant wireless battery charging system. The configuration is automatically changed with respect to the magnitude of the input AC voltage. The output voltage of the multi-mode rectifier is sensed by a comparator. Furthermore, the configuration of the multi-mode rectifier is automatically selected by switches as original rectifier mode, 1-stage voltage multiplier or 2-stage voltage multiplier mode. As a result, a rectified DC voltage is output from 7.5 to 19 V for an input AC voltage of 5–20 V. In the transmitter, a class-E power amplifier (PA) with an automatic power control loop and load compensation circuit is proposed to improve the power efficiency. The transmitted power is controlled by adjusting the signal applied to the gate of the power control transistor. In addition, a parallel capacitor is also controlled to enhance the efficiency and compensate for the load variation. This chip is implemented using 0.35 μm BCD technology with an active area of around 5,000 × 2,500 μm. When the magnitude of the input AC voltage is 10 V, the power conversion efficiency of the multi-mode active rectifier is about 94 %.The maximum power efficiency of the receiver is about 70 %. The transmitter provides an output power control range of 10–30.2 dBm. The maximum power efficiency of the PA is 71.5 %.     

Selective and nonselective wet etching of Zn0.9Mg0.1O/ZnO

Wet etch rates at 25°C for Zn_0.9Mg_0.1O grown on sapphire substrates by pulsed laser deposition (PLD) were in the range 300–1100 nm · min⁻¹ with HCl/H₂O (5×10⁻³−2×10⁻² M) and 120–300 nm · min⁻¹ with H₃PO₄/H₂O (5×10⁻³−2×10⁻² M). Both of these dilute mixtures exhibited diffusion-limited etching, with thermal activation energies of 2–3 kCal · mol⁻¹. By sharp contrast, the etch rates for ZnO also grown on sapphire by PLD were much slower in similar solutions, with rates of 1.2–50 nm · min⁻¹ in HCl/H₂O (0.01–1.2 M) and 12–54 nm · min⁻¹ in H₃PO₄/H₂O (0.02–0.15 M). The etching was reaction limited over the temperature range 25–75°C, with activation energies close to 6 kCal · mol⁻¹. The resulting selectivity of Zn_0.9Mg_0.1O over ZnO can be a high as ∼400 with HCl and ∼30 with H₃PO₄.     

elemental redistribution and interfacial reaction mechanism for the flip chip Sn-3.0Ag-(0.5 or 1.5)Cu solder bump with Al/Ni(V)/Cu under-Bump metallization during aging

In flip chip technology, Al/Ni(V)/Cu under-bump metallization (UBM) is currently applicable for Pb-free solder, and Sn−Ag−Cu solder is a promising candidate to replace the conventional Sn−Pb solder. In this study, Sn-3.0Ag-(0.5 or 1.5)Cu solder bumps with Al/Ni(V)/Cu UBM after assembly and aging at 150°C were employed to investigate the elemental redistribution, and reaction mechanism between solders and UBMs. During assembly, the Cu layer in the Sn-3.0Ag-0.5Cu joint was completely dissolved into solders, while Ni(V) layer was dissolved and reacted with solders to form (Cu_1−y,Ni_y)₆Sn₅ intermetallic compound (IMC). The (Cu_1−y,Ni_y)₆Sn₅ IMC gradually grew with the rate constant of 4.63 × 10⁻⁸ cm/sec^0.5 before 500 h aging had passed. After 500 h aging, the (Cu_1−y,Ni_y)₆Sn₅ IMC dissolved with aging time. In contrast, for the Sn-3.0Ag-1.5Cu joint, only fractions of Cu layer were dissolved during assembly, and the remaining Cu layer reacted with solders to form Cu₆Sn₅ IMC. It was revealed that Ni in the Ni(V) layer was incorporated into the Cu₆Sn₅ IMC through slow solid-state diffusion, with most of the Ni(V) layer preserved. During the period of 2,000 h aging, the growth rate constant of (Cu_1−y,Ni_y)₆Sn₅ IMC was down to 1.74 × 10⁻⁸ cm/sec^0.5 in, the Sn-3.0Ag-1.5Cu joints. On the basis of metallurgical interaction, IMC morphology evolution, growth behavior of IMC, and Sn−Ag−Cu ternary isotherm, the interfacial reaction mechanism between Sn-3.0Ag-(0.5 or 1.5)Cu solder bump and Al/Ni(V)/Cu UBM was discussed and proposed.     

接触面陷阱密度对a-InSnZnO薄膜晶体管器件电气性能的影响研究

We reported the influence of interface trap density（Nt） on the electrical properties of amorphous InSnZnO based thin-film transistors,which were fabricated at different direct-current（DC） magnetron sputtering powers.The device with the smallest N_t of 5.68×10¹¹ cm^-2 and low resistivity of 1.21×10^-3Ω·cm exhibited a turn-on voltage(V_ON) of-3.60 V,a sub-threshold swing（S.S） of 0.16 V/dec and an on-off ratio(I_ON/I_OFF) of⁸ x 108.With increasing N_t,the V_ON,S.S and I_ON/I_OFF were suppressed to-9.40 V,0.24 V/dec and 2.59×10⁸,respectively.The V_TH shift under negative gate bias stress has also been estimated to investigate the electrical stability of the devices.The result showed that the reduction in N_t contributes to an improvement in the electrical properties and stability.     

Materials and Wireless Microfluidic Systems for Electronics Capable of Chemical Dissolution on Demand

Electronics that are capable of destroying themselves, on demand and in a harmless way, might provide the ultimate form of data security. This paper presents materials and device architectures for triggered destruction of conventional microelectronic systems by means of microfluidic chemical etching of the constituent materials, including silicon, silicon dioxide, and metals (e.g., aluminum). Demonstrations in an array of home‐built metal‐oxide‐semiconductor field‐effect transistors that exploit ultrathin sheets of monocrystalline silicon and in radio‐frequency identification devices illustrate the utility of the approaches.