bluuebunny/crossref_metadata_2025 huggingface dataset:
Systematic Investigation of the Intrinsic Channel Properties and Contact Resistance of Monolayer and Multilayer Graphene Field-Effect Transistor
Authors: Nagashio Kosuke , Nishimura Tomonori , Kita Koji , Toriumi Akira
Published: May 2010

The intrinsic channel properties of monolayer and multilayer graphene were systematically investigated as a function of layer number by the exclusion of contact resistance using four-probe measurements. We show that the continuous change in normalized sheet resistivity from graphite to a bilayer graphene is governed by one unique property, i.e., the band overlap, which markedly increases from 1 meV for a bilayer graphene to 11 meV for eight layers and eventually reaches 40 meV for graphite. The monolayer graphene, however, showed a deviation in temperature dependence due to a peculiar linear dispersion. Additionally, contact resistivity was extracted for the case of typical Cr/Au electrodes. The observed high contact resistivity, which varies by three orders of magnitude (from ∼103 to 106 Ω µm), might significantly mask the outstanding performance of the monolayer graphene channel, suggesting its importance in future research.
Rotational Behavior of Stripe Domains Appearing in Hybrid Aligned Chiral Nematic Liquid Crystal Cells
Authors: Nose Toshiaki , Miyanishi Toshitaka , Aizawa Yuki , Ito Ryouta , Honma Michinori
Published: May 2010

The appearance of stripe domains is strongly affected by various cell conditions such as thickness, applied voltage, and surface alignment. In this work, we adopt hybrid surface alignment to investigate the appearance of stripe domains under asymmetric surface anchoring. It is observed that the stripe direction rotates continuously according to the cell thickness and applied voltage, which has potential as a unique diffraction grating. It is also found that the rotational response time is always several seconds for any size of cell, because a large area rotation is achieved by the sum of small poly domain rotations related to defect creation–extinction processes on their boundaries.
Characteristic Improvements of ZnO-Based Metal–Semiconductor–Metal Photodetector on Flexible Substrate with ZnO Cap Layer
Authors: Ji Liang-Wen , Wu Cheng-Zhi , Lin Chih-Ming , Meen Teen-Hang , Lam Kin-Tak , Peng Shi-Ming , Young Sheng-Joue , Liu Chien-Hung
Published: May 2010

In this work, ZnO-based metal–semiconductor–metal photodetectors with and without a ZnO cap layer were fabricated on flexible substrates of poly(ethylene terephthalate) (PET) for comparative analysis. The ZnO films were prepared by a low-temperature sputtering process. The photodetector with a ZnO cap layer (stack structure: ZnO/Ag/ZnO/PET) shows a much higher UV-to-visible rejection ratio of 1.56 ×103than that without. This can be attributed to the photocurrents that are not only significantly increased in the UV region but also slightly suppressed in the visible region for such a novel structure. With an incident wavelength of 370 nm and an applied bias of 3 V, the responsivities of both photodetectors with and without a ZnO cap layer are 3.80 ×10-2and 2.36 ×10-3A/W, which correspond to quantum efficiencies of 1.13 and 0.07%, respectively. The Schottky barrier height at the Ag/ZnO interface is also determined to be 0.782 eV.
Narrow Bandstop Filters with Wide and Flattened Sidebands Using Silicon-Based and Suspended Membrane Type of Guided-Mode Resonance Structures
Authors: Chang Chia-Chi , Lan Hsiao-Chin , Hsiao Hsu-Liang , Jheng Jhong-Wei , Lu I-Chun , Lee Yun-Chih , Wu Mount-Learn
Published: May 2010

In this paper, the simple two-layer silicon-based and suspended-membrane-type guided-mode resonance (GMR) filter with a narrow bandstop spectrum as well as wide and flattened sidebands is experimentally demonstrated. The proposed filter based on a free-standing silicon nitride membrane suspended on a silicon substrate is realized by using the anisotropic wet etching to remove the substrate beneath the silicon nitride layer. Both of grating and waveguide structures are fabricated simultaneously on a silicon nitride membrane. Moreover, the silicon dioxide membrane playing a role on modifying the spectral response of proposed GMR filter is deposited beneath the free-standing silicon nitride layer. The resonance wavelength of proposed band-stop filter is controlled at 1580.6 nm with a bandwidth less than 0.92 nm, measured in full-width at half-maximum (FWHM). The improved spectral performance including the sideband can be extended to be 415 nm with the maximum transmittance greater than 93%.
Design and Simulation of Silicon Waveguide Optical Circulator Employing Nonreciprocal Phase Shift
Authors: Takei Ryohei , Mizumoto Tetsuya
Published: May 2010

In this paper, we propose an optical circulator employing a nonreciprocal phase shift with a silicon waveguide. Two types of optical circulators are investigated, a perfectly circulating four-port optical circulator and a three-port optical circulator. Nonreciprocal characteristics are obtained owing to the first-order magneto-optic effect of a magneto-optic garnet directly bonded onto a silicon guiding layer. The waveguide structure is designed by numerical simulations. When we use a 220-nm-thick and 500-nm-wide silicon waveguide core, the required length of the nonreciprocal phase shifter is 348.3 µm at a wavelength of 1.55 µm. The four-port optical circulator exhibits a crosstalk below -20 dB in a wavelength range between 1.54 and 1.56 µm. The three-port optical circulator exhibits a crosstalk below -20 dB in a wavelength range between 1.53 and 1.57 µm. The total length of both types of optical circulators is approximately 420 µm.
Effect of Silicon Doping on Performance of 30-Pair InxGa1-xN/GaN Quantum Well Solar Cells
Authors: Jeng Ming-Jer , Su Te-Wen , Lee Yu-Lin , Chang Yuan-Hsiao , Chang Liann-Be , Lin Ray-Ming , Jiang Jhong-Hao , Lu Yuan-Chieh
Published: May 2010

Silicon doping in a barrier layer has been demonstrated to improve crystal quality and the interfacial quality of InGaN/GaN quantum wells. Furthermore, it also reduces piezoelectric field with heavy silicon doping. In this work, the characteristics of 30-pair InxGa1-xN/GaN quantum well solar cells with undoped wells/undoped barriers (UWUB), Si-doped wells/Si-doped barriers (DWDB), and undoped wells/Si-doped barriers (UWDB) are compared and investigated. The short circuit currents (Jsc) of the solar cells with UWUB, DWDB, and UWDB are 0.54, 0.16, and 0.23 mA/cm2, respectively. This indicates that the electric field in quantum wells dominates the collected current capability. The open circuit voltages (Voc) of the solar cells with UWUB, DWDB, and UWDB are 2.18, 1.38, and 1.91 V, respectively. Recombination rate determinesVoc. The solar cell with UWUB exhibits the highest efficiency among the three solar cells. The temperature dependences of solar efficiency differ in three cases. As temperature increases, solar efficiency decreases in the UWUB sample, and increases in the DWDB and UWDB samples owing to the competition between the increasingJscand the decreasingVoc.
Amplified Pulse Emissions with Variable Delay Times in Vibronic Transition Bands of Thiophene/Phenylene Co-Oligomer Single Crystals
Authors: Matsuoka Naoki , Hiramatsu Toru , Yanagi Hisao , Sasaki Fumio , Hotta Shu
Published: May 2010

Time-resolved photoluminescence of thiophene/phenylene co-oligomer (TPCO) single crystals has been measured at 7 K. The amplified pulse emissions with time delay are demonstrated in the 0–2 vibronic transition band of the TPCO single crystal under high-intensity excitation. We identify the delayed pulse emission to the 2A
1 vibration line. The pulse peak of the 2A
1 line exhibits a maximum delay time of 70 ps at 7 K. We consider that the amplified pulse emissions with time delay in single crystals occur at a vibronic transition band with the largest spontaneous emission intensity in the PL spectrum under weak excitation.
Nickel Plating on Silicon for Fabricating an Infrared Wire-Grid Polarizer
Authors: Saito Mitsunori , Yamamoto Tatsuya , Yamada Itsunari , Nishii Junji , Mihara Susumu , Urano Masashi
Published: May 2010

An IR polarizer was fabricated by plating a Ni wire-grid on a Si substrate. The Si surface was processed by photolithography to create grooves with ∼200 nm width, ∼200 nm spacing, and ∼300 nm depth. After surface treatment, the Si plate was put in a plating bath for ∼5 min to fill the grooves with Ni. The excess Ni film that was deposited outside the grooves was removed by mechanical polishing. The fabricated wire-grid exhibited a polarization function with an extinction ratio of 15–20 dB in the 3–13 µm wavelength range.
Injection Molded Optical Lens Using a Heat Resistant Thermoplastic Resin with Electron Beam Cross-Linking
Authors: Sano Tomomi , Iyoda Yoshitomo , Shimazu Takayuki , Harumoto Michiko , Inoue Akira , Nakabayashi Makoto , Ito Hiroshi
Published: May 2010

The poor heat resistant properties of a transparent thermoplastic resin was improved by electron beam irradiation cross-linking. A correcting aspheric lens for a 635-nm laser diode was fabricated using an injection molding machine, and was irradiated with an electron beam. The near field pattern (NFP), the far field pattern (FFP) at the focus position and the transmittance of the lens did not change after exposure to a 260 °C reflow process for 60 s.
Ultrashort Pulse Compression for Mode-Locked Ti:Sapphire Laser by Using a Tapered Fiber and Grating Pair
Authors: Lin Ja-Hon , Taso Chih-Chieh , Hsu Kuei-Chu , Lin Kuei-Huei , Lai Yinchieh
Published: May 2010

Extracavity pulse compression for pulses from an 82 MHz mode-locked Ti:sapphire laser is demonstrated by utilizing a tapered fiber of 1 µm in diameter and 10 mm in length. Group velocity dispersion of the tapered fiber is calculated, which shows two zero dispersion wavelengths locating at 545 and 1250 nm, respectively. The nonlinear coefficient γ of the tapered fiber is estimated to be 733 (W-1 km-1) at 880 nm wavelength. With 80 fs input pulses at 880 nm center wavelength, the optical bandwidth is broadened beyond 22 THz by the tapered fiber. After dispersion compensation by a grating pair with 1.45 cm separation, 26 fs output pulses are obtained. One-third pulse compression ratio has been experimentally demonstrated in this work for center wavelengths ranging from 720 to 880 nm.
Mn Doping in Half-Heusler Semiconductors: Microstructural and Transport Properties
Authors: Wang Fangfang , Fukuhara Tadashi , Maezawa Kunihiko , Masubuchi Shinichi
Published: May 2010

The possibility of Mn doping in half-Heusler semiconductors (CoTiSb, FeVSb, NiTiSn, and NiZrSn) is reported. Mn-added polycrystalline ingots of these semiconductors were prepared by arc melting. Microstructural properties of these ingots indicate that the solubility limit of Mn in the half-Heusler phase is confined to a relatively limited range, that is, 0% for CoTiSb and FeVSb, 1% for NiTiSn, and 2% for NiZrSn. The electrical resistivity of polycrystalline NiZr0.98Mn0.02Sn indicates semiconducting temperature dependence with a transport gap of 84 meV.
Investigation of Threshold Voltage Variability at High Temperature Using Takeuchi Plot
Authors: Tsunomura Takaaki , Nishida Akio , Hiramoto Toshiro
Published: May 2010

The property of metal–oxide–semiconductor field-effect transistors' (MOSFETs) threshold voltage (V
T) variability at high temperature is investigated by evaluating the device matrix array test element group (DMA-TEG). It is revealed that V
T variation is lower at high temperature than at room temperature, and that V
T at high temperature has a strong correlation with V
T at room temperature. The normal property of V
T variability both at room and high temperatures is validated using the normal probability plot. The decrease in V
T variation at high temperature stems from the reduction of the channel depletion layer width (W
dep). The temperature dependence of V
T variation is evaluated using the Takeuchi plot, the V
T variation normalization method. It is revealed that the change in B
VT, the parameter of V
T variation in the Takeuchi plot, is very small with varying temperature.
Uniform Surface Patterning with Two-Dimensional Gold Nanoparticle Array Excited by Oblique Femtosecond Laser Irradiation
Authors: Miyanishi Tomoya , Tanaka Yuto , Terakawa Mitsuhiro , Obara Minoru
Published: May 2010

We present optical field distributions and nanohole patterning properties on a silicon substrate when a femtosecond laser is irradiated obliquely to a two-dimensional (2D) gold nanoparticle array on a silicon surface. It is necessary to control plasmon polaritons in a gold nanoparticle array by adjusting interparticle distance and the incident angle of the laser for uniform nanohole patterning with an 800 nm femtosecond laser. The uniform 2D nanohole patterning is studied by finite-difference time-domain (FDTD) calculation and experiment using a femtosecond laser. Using an array with gold particles of 200 nm diameter, the near-field intensity on the Si surface is much larger than that of a single isolated particle if the interparticle distance is larger than 200 nm and the incident angle is approximately 50°. The oblique irradiation of p-polarized incident laser to the surface of the substrate ensures that uniform nanohole array patterning is achieved.
Low-Frequency Noise in Carbon-Nanotube/Cellulose Composite Paper
Authors: Tanaka Tomo , Sano Eiichi , Imai Masanori , Akiyama Kousuke
Published: May 2010

Low-frequency noise characteristics for carbon-nanotube (CNT)/cellulose composite paper were experimentally investigated. The measured low-frequency noise exhibited 1/f characteristics and can be explained by Hooge's empirical law. Large noise coefficients suggested that CNT–CNT junctions, not the CNTs themselves, are the dominant source of 1/f noise in the composite paper.
Influence of Incorporating Rare Earth Metals on the Schottky Barrier Height of Ni Silicide
Authors: Zhang Ying-Ying , Jung Soon-Yen , Oh Jungwoo , Shin Hong-Sik , Oh Se-Kyung , Wang Jin-Suk , Majhi Prashant , Jammy Raj , Lee Hi-Deok
Published: May 2010

Characterized herein is a different physical mechanism for the formation of Ni silicide by incorporating rare earth (RE) metals such as ytterbium (Yb), erbium (Er), and dysprosium (Dy). Although the incorporation of any RE metal increases the Schottky barrier height (SBH) for holes in Ni silicide due to the formation of a ternary phase silicide, Yb induced the greatest increase in SBH because, unlike the other metals, Yb atoms accumulated at the silicide/silicon interface.
Modification of Semianalytical Finite Element Model for Radio Frequency Sheaths in Single- and Dual-Frequency Capacitively Coupled Plasmas: Incorporating Ion Density Oscillation at Low Frequency
Authors: Denpoh Kazuki , Shirafuji Tatsuru
Published: May 2010

The semianalytical rf sheath model for single- and dual-frequency capacitively coupled plasmas based on the finite element method has been modified by incorporating ion density oscillation at low frequency into it. Using the new rf sheath model, we have confirmed that the ion density in a one-dimensional dual-frequency (60 MHz/2 MHz) sheath responds to 2 MHz, but not to 60 MHz. The electron density profile affected by the ion density oscillation agrees well with a result from a particle-in-cell, Monte Carlo collision plasma model referred to in this study. This is an indirect but positive proof of the validity of our modified rf sheath model. We have also applied the model to a sheath around a gap between a wafer and a focus ring in a dual-frequency (40 MHz + 3.2 MHz) etching reactor to demonstrate its capability for multidimensional simulation.
Model for Bias Frequency Effects on Plasma-Damaged Layer Formation in Si Substrates
Authors: Eriguchi Koji , Nakakubo Yoshinori , Matsuda Asahiko , Takao Yoshinori , Ono Kouichi
Published: May 2010

Bias frequency effects on damaged-layer formation during plasma processing were investigated. High-energy ion bombardment on Si substrates and subsequent damaged-layer formation are modeled on the basis of range theory. We propose a simplified model introducing a stopping powerSd(Eion) with a power-law dependence on the energy of incident ions (Eion). We applied this model to damaged-layer formation in plasma with an rf bias, where various energies of incident ions are expected. The ion energy distribution function (IEDF) was considered, and the distribution profile of defect sites was estimated. We found that, owing to the characteristic ion-energy-dependent stopping powerSd(Eion) and the straggling, the bias frequency effect was subject to suppression, i.e., the thickness of the damaged layer is a weak function of bias frequency. These predicted features were compared with experimental data on the damage created using an inductively coupled plasma reactor with two different bias frequencies; 13.56 MHz and 400 kHz. The model prediction showed good agreement with experimental observations of the samples exposed to plasmas with various bias configurations.
Characteristics of Ion-Induced Bending Phenomenon
Authors: Yoshida Tomoya , Nagao Masayoshi , Kanemaru Seigo
Published: May 2010

We propose a technique of bending thin films based on the ion-induced bending (IIB) phenomenon that allows the fabrication of three-dimensional device structures and arrays, such as devices for micro-electromechanical systems (MEMSs). We investigated the IIB characteristics with various types of thin films under various ion irradiation conditions. We found that the important parameters of the IIB phenomenon were the depth of ion irradiation and ion dose. We also found that bending curvature could be controlled by the normalized depth of ion implantation and the dose of ions. Microsized regions of vertically standing thin-film arrays that were tens of nanometers thick could be produced with this technique.
High Performance of Ultralow Temperature Polycrystalline Silicon Thin Film Transistor on Flexible Metal Foil Substrate
Authors: Park Dong Jin , Park Byung Ok
Published: May 2010

A high performance ultralow temperature polycrystalline silicon (poly-Si) thin film transistor (TFT) was obtained on a flexible metal foil substrate using the optimization of a benzocyclobutene (BCB) planarization process for a rough flexible metal foil substrate surfaces, the high quality SiO2 interface layer formation between the gate dielectric film and the poly-Si film using plasma oxidation, and a successful crystallization of large grain poly-Si films with a sequential lateral solidification (SLS) method. High performances with field effect mobilities of 196 and 95 cm2 V-1 s-1, threshold voltages of 1.6 and -1.5 V and sub-threshold swings of 0.53 and 0.45 V/decade were obtained for n-channel metal–oxide–semiconductor (nMOS) and p-channel metal–oxide–semiconductor (pMOS) TFT on flexible metal foil substrate, respectively.
Evaluation of Post Ion-Implantation Resist Strip with the Background Signal of a Light Scattering Tool
Authors: Halder Sandip , Vos Rita , Wada Masayuki , Tsvetanova Diana , Claes Martine , Mertens Paul W. , Radovanović Sanda , Dighe Prasanna , Amann Christophe , Simpson Gavin , Polli Marco
Published: May 2010

A new method for the fast evaluation of photoresist residue removal efficiency is discussed in this paper. In this method “haze” which is the low frequency component of the background signal of a light scattering instrument is mapped over the entire wafer. Since, the background signal is sensitive to any kind of surface anomaly it can be used as a metric for any kind of surface roughness or residues. The goal of this work was to devise a fast and cheap screening method for photoresist residue removal efficiency. Using this method we show that cleaning solutions can be easily screened for their residue removal efficiencies based on the haze signal of the light scattering instrument. Different ion implantation conditions are checked and also different aerosol spray assisted cleaning conditions are evaluated.
Effect of DC Bias Voltage on the Characteristics of Low Temperature Silicon–Nitride Films Deposited by Internal Linear Antenna Inductively Coupled Plasma Source
Authors: Gweon Gwang Ho , Lim Jong Hyeuk , Hong Seung Pyo , Yeom Geun Young
Published: May 2010

The characteristics of silicon–nitride deposited at the temperature lower than 100 °C using an internal linear-type inductively coupled plasma were investigated as functions of the NH3/SiH4 ratio and ion bombardment energy applied to the substrate (dc bias voltage) for use as the gate dielectric material of flexible display devices. Decreasing the NH3/SiH4 ratio to 2 and increasing the dc bias voltage to -150 V decreased the Si–O bonding and increased the Si–N bonding, resulting in a more nitrogen-rich SiN
x
thin film. In addition, the capacitance-voltage measurement of the metal-insulator-semiconductor devices fabricated with the SiN
x
thin film deposited at various dc bias voltages showed a hysteresis curve in the cyclic voltage measurement and the increase of the dc bias voltage with decreasing hysteresis voltage. The interface trap density measured at a dc bias voltage of -150 V and NH3/SiH4 ratio of 2 showed the lowest interface trap charge density of about 2×1011 cm-2. Under these conditions, the dielectric constant was as high as 7.2.
Fabrication of Peristaltic Micropump Driven by a Single-Phase Pneumatic Force
Authors: Jeong Ok Chan , Konishi Satoshi
Published: May 2010

In this paper, we describe a micropump with self-generated peristaltic action, operated by a single-phase pneumatic force for use in a functional microhand. The micropump consists of three actuators and a microfluidic channel. The actuators are connected by a single microchannel for the supply of external compressed air. The self-generated peristaltic motion of the cascaded actuators is created by the pressure loss and the deformation of the actuator diaphragm induced by the applied pressure. Both the fluidic resistance along the microchannel and the fluidic capacitance of the actuator diaphragms result in the sequential deformation of the cascaded actuators, like a triple low-pass filter in an electrical circuit. The micropump was fabricated by soft lithography using only polydimethylsiloxane. The flow rate of the working fluid was observed and measured. The experimental results confirmed that the improved design of the actuators enables a high flow rate of working fluid at a low pressure.
Improved Resistive Switching Dispersion of NiOx Thin Film by Cu-Doping Method
Authors: Liu Chih-Yi , Lin Xin-Jie , Wang Hung-Yu , Lai Chun-Hung
Published: May 2010

Thermally grown NiO
x
and Cu-doped NiO
x
(Cu:NiO
x
) thin films were fabricated as resistive layers for Cu/NiO
x
/Pt and Cu/Cu:NiO
x
/Pt devices and their resistive switching properties were investigated. The two devices had reversible resistive switching properties, nondestructive readout, and long retention. However, the Cu/NiO
x
/Pt device had large voltage dispersions in the resistive switching operation. This work improved the voltage dispersions of the resistive switching operation by Cu-doping in the NiO
x
thin film. The operating voltages of the Cu/Cu:NiO
x
/Pt device were also smaller than those of the Cu/NiO
x
/Pt device. This study suggests the conducting filament model to explain resistive switching behavior and improved resistive switching dispersions. The Cu-doping method produced more defects within the NiO
x
thin film, which improved voltage dispersion and decreased operation voltages.
Model for Analysis of Biaxial and Triaxial Stresses by X-ray Diffraction Assuming Orthotropic Materials
Authors: Santos Edson M. , Orlando Marcos T. D. , Miltão Milton S. R. , Martinez Luis G. , Alves Alvaro S. , Passos Carlos A.
Published: May 2010

In this work we aim to develop expressions for the calculation of biaxial and triaxial stresses in polycrystalline anisotropic materials, and to determine their elastic constants using the theory of elasticity for continuum isochoric deformations; thus, we also derive a model to determine residual stress. The constitutive relation between strain and stress in these models must be assumed to be orthotropic, obeying the generalized Hooke's law. One technique that can be applied with our models is that of X-ray diffraction, because the experimental conditions are similar to the assumptions in the models, that is, it measures small deformations compared with the sample sizes and the magnitude of the tensions involved, and is insufficient to change the volume (isochoric deformation). Therefore, from the equations obtained, it is possible to use the sin
2ψ technique for materials with texture or anisotropy by first characterizing the texture through the pole figures to determine possible angles ψ that can be used in the equation, and then determining the deformation for each diffraction peak with the angles ψ obtained from the pole figures.
Regrowth of Semipolar GaN on Nanoporous GaN Template by Metal Organic Chemical Vapor Deposition
Authors: Lee Dong-Hun , Jang Jong-Jin , Kong Bo-Hyun , Cho Hyung-Koun , Nam Okhyun
Published: May 2010

A nanoporous semipolar GaN template has been fabricated by photoenhanced electrochemical etching to obtain porous GaN with nanoscale pores. The surface morphology of regrown semipolar GaN on a nanoporous GaN template was enhanced by surface modification. Cross-sectional transmission electron microscopy (TEM) images showed reductions in the densities of dislocations and basal stacking faults at the regrown interface. Photoluminescence measurement also revealed that the crystallinity of regrown GaN was improved by reducing the density of defects. Our results suggest that the photoenhanced electrochemical etching and regrowth technique is promising for high-quality semipolar GaN growth with a reduced defect density on a sapphire substrate.
Interferometric Optical Isolator with Air/Si/Magnetic-Garnet Waveguide Operated in Unidirectional Magnetic Field
Authors: Yokoi Hideki , Igarashi Shun , Uchiumi Yuki
Published: May 2010

An optical isolator with a Si guiding layer that makes use of a nonreciprocal phase shift is discussed. The Si guiding layer is sputter-deposited on a garnet substrate. The magnetooptic waveguide in the optical isolator has an air/Si/magnetic-garnet structure. The optical isolator can be operated in a unidirectional magnetic field owing to an interferometer with distinct layer structures. Various layer structures will be proposed for unidirectional magnetic field operation.
X-ray Stress Evaluation in Phase Change GeSbTe Material and TiW Electrodes
Authors: Li Minghua , Shi Luping , Zhao Rong , Chong Tow Chong , Li Yi
Published: May 2010

Stress generation and relaxation upon Ge2Sb2Te5 (GST) crystallization were studied by X-ray diffraction technique, which allows the stress in either GST or Ti3W7 (TiW) to be evaluated independently within TiW/GST/TiW multilayer film. The GST crystallization results in tensile stress in the GST film and additional compressive stress in the TiW film, due to volume shrinkage of the GST film. Moreover, the tensile stress in the GST film is significantly increased when it is sandwiched between TiW films. Interfacial effect is proposed to attribute the dependence of stress on the capping layer thickness.
Synthesis of Pd(II) Ink and Surface Treatment of the Polyimide Film for Inkjet Printing
Authors: Suh Seung Wook , Lee Yong Sang , Park Byung Ki , Kim Dong Soo
Published: May 2010

By hydrolyzing PdCl2 with NH4Cl and then by adding a stabilizing agent to it, the Pd(II) catalyst ink with the excellent storage stability, and as a low viscosity and surface tension as water was synthesized. Polyimide (PI) film was used as a substrate for manufacturing a printed circuit by inkjet printing of the Pd(II) catalyst ink, while various characteristic changes of the printing were observed depending on the contact angle on the substrate surface. The contact angle was affected by the concentration of KOH solution and by the duration of surface treatment, and a surface condition suitable for composing Cu circuit was obtained by printing Pd(II) catalyst ink and electroless plating when it was treated in 1–3 M KOH solution for 10 min. The physical properties of the Pd(II) catalyst ink were analyzed using a surface tension meter, viscometer, pH meter and ultraviolet–visible (UV–vis) spectrophotometer, whereas the surface properties of the PI film were analyzed using a contact angle instrument, fourier transform infrared–attenuated total reflectance (FTIR–ATR), video microscope, X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM), and atomic force microscopy (AFM). The physical properties of Pd(0) particles were analyzed by XPS, FESEM, and AFM, while the characteristics of electroless plating were analyzed by video microscope and XPS.
Synthesis of Direct Printable CdS Nanoparticles for Cu(In,Ga)Se2/CdTe Thin-Film Solar Cell
Authors: Hwang Se-Yeon , Kim Nam-Soo
Published: May 2010

CdS nanoparticles were synthesized for the application in direct write technology. Various parameters such as deposition time, pH, and cadmium ion concentration, were varied in order to observe optimum conditions for the synthesis of CdS nanoparticles. As a result of this study, it was confirmed that the optimum conditions for synthesis of CdS nanoparticles were pH 11, 70 °C, and 3 mmol/dm3 cadmium. CdS nanoparticles, synthesized under these conditions, were under-filled between two glass substrates, and the elements, cadmium and sulphur, on glass substrates were observed with an energy-dispersive X-ray spectrometer (EDX). This indicates that the deposition of CdS nanoparticles by a direct printing process into two substrates is possible, and CdS nanoparticles can be applied to the fabrication of a Cu(In,Ga)Se2/CdTe thin-film solar cell.
Laser Curing of the Silver/Copper Nanoparticle Ink via Optical Property Measurement and Calculation
Authors: Kim Tae-Yeop , Hwang Jun-Young , Moon Seung-Jae
Published: May 2010

The spectral optical properties of the silver/copper nanoparticle ink at visible and near-infrared wavelength were measured by ellipsometry. The purpose of the measurement of the optical properties is to select the optimal process parameters such as working wavelength and laser incidence angle by finding the maximum absorption wavelength. The reflectance and absorptivity of the nano-ink including silver/copper nanoparticles were calculated from the experimentally obtained refractive indices. The absorptivity has been maximized at the green wavelength for the normal incident angle to the target at the initial stage of the curing. Therefore, a continuous wave green laser at the wavelength of 532 nm is chosen for the laser curing. For the laser curing process, the inkjet-printed silver/copper nano-ink samples on the glass and poly(ethylene terephthalate) (PET) substrates are adopted to find the effect of the substrate materials on laser curing process. The used laser energy is 31.62 and 177.27 W/cm2 to analyze the effect of the laser intensity on laser curing process. The nano-ink on the PET substrate has lower specific resistance than that on the glass substrate with the identical laser irradiation time. The higher laser intensity is recommended to obtain the lower specific resistance with same laser irradiation. Compared with the 30-min furnace curing process at the temperature of 250 °C, a few seconds laser curing process can be effectively adopted with appropriate scanning system to shorten the curing time.
Preparation and Characterization of Silicon Nanoparticles for Solution-Processed Thin Film
Authors: Son Ha-Young , Lim Eunhee , Kwon Ha Young , Lee Sungkoo , Lee Kyeong K.
Published: May 2010

We describe the synthesis of the alkoxy-capped silicon nanoparticles (Si NPs) via solution route without an explicit reduction process. Based on the UV–visible absorption and photoluminescence (PL) emission spectra of the alkoxy-capped Si NPs, the average size of Si NPs is estimated to be ca. 3 nm. Fourier transform infrared (FT-IR) spectroscopy on the sintered Si thin film confirms elimination of the alkyl groups from the nanoparticles as evidenced by the shrinkage of the absorption peaks corresponding to –CH
n
and Si–OR. Although the silicon film was highly resistive, we have consistently observed the electrical conduction from films coated with the doped NPs.
Low-Temperature Solution-Deposited Oxide Thin-Film Transistors Based on Solution-Processed Organic–Inorganic Hybrid Dielectrics
Authors: Song Keunkyu , Jeong Youngmin , Jun Taewhan , Koo Chang Young , Kim Dongjo , Woo Kyoohee , Kim Areum , Noh Junghun , Cho Seongwhan , Moon Jooho
Published: May 2010

We describe low-temperature, solution-deposited, oxide semiconductor thin-film transistors (TFTs) with a solution-processed gate dielectric in this study. The sol–gel-derived indium zinc oxide (IZO) semiconductor matched well with the organic–inorganic hybrid dielectric annealed at 200 °C, forming a coherent interface between the semiconductor and the dielectric without evidence of chemical damage. The IZO-TFTs made with a 420-nm-thick hybrid dielectric layer showed good performance: a low off-current on the order of <10-10 A, a field-effect mobility of 3.3×10-2 cm2 V-1 s-1, and a low threshold gate voltage of ∼2.4 V. Spin-coating of the IZO semiconductor on a hybrid dielectric/glass substrate results in TFTs optically transparent in the entire visible region (∼90%). Our solution-processable materials of the semiconductor and the gate dielectric can open the possibility of realizing flexible transparent devices using all-solution processing.
Highly Efficient Organic Photovoltaic Cells with Molybdenum Oxide Buffer Layer
Authors: Jung Jaewook , Kim Donghwan , Shin Won Suk , Moon Sang-Jin , Lee Changjin , Yoon Sung Cheol
Published: May 2010

For improving the power conversion efficiency and fill factor of the organic photovoltaic cells (OPVs), molybdenum oxide (MoO3) can be used as a buffer layer. In this study, we fabricated OPVs by inserting a thin and transparent molybdenum oxide (MoO3) layer between the transparent indium tin oxide (ITO) and the organic photoactive layer, with the configuration of ITO/MoO3 (10 nm)/poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C61 butyric acid methyl ester (PC60BM)/lithium fluoride (LiF)/Al. By spin-coating, the device showed power conversion efficiencies as high as 4.2% under AM 1.5G (100 mW/cm2), enhanced fill factor of 0.67, a short circuit current density (J
sc) of 9.32 mA/cm2, and open-circuit voltage (V
oc) of 0.67 V. In the case of flexible OPVs, device with 10-nm-thick MoO3 buffer or 45-nm-thick PEDOT:PSS buffer exhibited the power conversion efficiency (PCE) and fill factor (FF) of 1.54% and 0.44 or 0.76% and 0.30, respectively.
Thin Film Transistors with Ink-Jet Printed Amorphous Oxide Semiconductors
Authors: Kim Dongjo , Jeong Youngmin , Koo Chang Young , Song Keunkyu , Moon Jooho
Published: May 2010

We investigated the influence of the thickness of printed Ga–In–Zn-O (GIZO) channel on transistor performance. Semiconductor layers were ink-jet printed using sol–gel derived GIZO solution and the thickness of the resulting active layers varied depending on the pre-heated substrate temperature. We found that GIZO film thickness significantly influences device performance. Thin film transistors (TFTs) with thicker active layers showed higher on-current/off-current mobility and a threshold voltage shift in the negative direction. The dependence of the electric characteristics on thickness resulted from the increased intrinsic free charge carriers as the active layer thickness increased. Ink-jet printing conditions need to be carefully controlled to maximize device performance.
Organic Thin-Film Transistors with Transfer-Printed Au Electrodes on Flexible Substrates
Authors: Cho Hyunduck , Yoon Hyunsik , Char Kookheon , Hong Yongtaek , Lee Changhee
Published: May 2010

Bottom-gate, bottom-contact organic thin-film transistors (OTFTs) based on 6,13-bis(tri-isopropylsilylethynyl) pentacene (TIPS-pentacene) were fabricated on flexible substrates by transfer-printing and solution-based processes and their performances were characterized. Au gate and source/drain electrodes were transfer-printed from a release-layer-coated flexible mold at 2.4 MPa and 120 °C in ambient air. A polymer gate dielectric of poly(4-vinyl phenol) (PVP) and an active layer of TIPS-pentacene were deposited by solution processing. In addition, the TFT characteristics in channels of 40 and 4 µm length were compared. Also, the lack of saturation of the drain–source current (I
DS) was investigated by considering the output characteristics in a short channel.
Transparent Flexible Zinc–Indium–Tin Oxide Thin-Film Transistors Fabricated on Polyarylate Films
Authors: Cheong Woo-Seok , Bak Jun-Yong , Kim Hong Seung
Published: May 2010

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 cm2V-1s-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 cm2V-1s-1and an SS of 0.18.
Fabrication of Microgrooves on Roll Surfaces Using a Scanner and a Telecentric Lens
Authors: Noh Jiwhan , Suh Jeong , Na Suckjoo
Published: May 2010

A method of fabricating microgrooves on a roll surface was developed using a mirror scanner and a telecentric lens instead of a focusing lens. We used a telecentric lens with a large focal length to fabricate microgrooves on the roll. We also define “fabrication depth of focus” in order to estimate the possible fabrication area on a roll surface. The possible fabrication area was calculated using a scanner and a telecentric lens on a standstill roll. After that, the roll was rotated for the next fabrication area. By this method, microgrooves could be fabricated on the entire roll surface. The experimental results showed that the proposed method is quite promising for fabricating microgrooves on rolls that can be used for printing electronic devices.
Effects of Blanket Roller Deformation on Printing Qualities in Gravure-Offset Printing Method
Authors: Kim Kwangsoo , Kim Chung Hwan , Kim Heon-Yeoung , Kim Dong-Soo
Published: May 2010

In this paper, the deformation of the blanket roller when using the gravure-offset printing method for printed electronics, as well as the effect of this deformation on the quality of the printing, is examined. The mechanical properties of the blanket roller, which is made of silicone rubber compounds, are measured using a rubber tester. Mooney–Rivlin material parameters are obtained for the nonlinear elastic properties by conducting uniaxial and biaxial tests. The commercial finite element method (FEM), which is a numerical tool for solving partial differential equations (PDEs), is used to analyze the deformation of the blanket roller. In the FEM model, we consider the large-scale deformation of rubber showing nonlinear elastic behavior, and introduce a contact condition between flexible and rigid bodies. The parametric study shows that in the gravure-offset printing process, the distortions of the printed pattern, as well as changes in gain and changes in the position of the patterns caused by nip deformation of the rubber blanket, is significantly affected by printing loading and friction. Moreover, non-uniform friction condition due to partly patterned zone also makes a local pattern distortion.
Study of Improvement of Scan Mura in In-Plane Switching Panel Fabricated by the Inkjet Spacer Process
Authors: Kwon Dhang , Cho Hang Sup , Lee Myoung Ho , Lee Jeong Hoon , Seo Hyeon Jin , Kang Dong Woo , Kim Bong Chul , Yu Sang Jeon
Published: May 2010

In this paper, we have investigated the scan mura due to the difference of spacer position in each nozzle of inkjet heads for inkjet spacer process. It was found that the difference of the cell gap was about 0.051 µm between a bright area and a dark area in panel with strong scan mura. The difference of the cell gap means the subtracted value of the cell gap in the dark area from the cell gap in the bright area. In the case of adjusting of dropped ink velocity on each nozzle, the scan mura is improved, but is not perfect. On the other hand, the scan mura is drastically improved by the randomization of spacer position using nozzle mixing method (NMM), where the difference of cell gap is only 0.009 µm. It is considered that the scan mura is strongly influenced by ink dropped position, the inkjet process.
Numerical and Experimental Evaluation of Picoliter Inkjet Head for Micropatterning of Printed Electronics
Authors: Yoo Young-Seuck , Kim Changsung Sean , Park Yoon Sok , Sim Won-Chul , Park Changsung , Joung Jaewoo , Park Jin-Goo , Oh Yongsoo
Published: May 2010

A design process based on multiphysics modeling and micro-electro-mechanical systems (MEMS) fabrication has been established to develop a picoliter inkjet printhead for micro-patterning for printed electronics. Piezoelectric actuator is designed with numerical analysis using Covent-Ware with consideration of electrical characteristic of piezoelectric material and physical characteristic of silicon structure. The displacements of a piezoelectric actuator according to voltage waveform are evaluated and verified by laser doppler vibrometer (LDV). Piezoelectric printheads have been fabricated with silicon and silicon-on-insulator (SOI) wafers by MEMS process and silicon to silicon bonding method. As a preliminary approach, liquid metal jetting phenomena are identified by simulating droplet ejection and droplet formation in a consequent manner. Parametric studies are followed by the design optimization process to deduce key issues to inkjet head performance: printhead configuration, input voltage amplitude, ink viscosity and meniscus movement using computational fluid dynamics (CFD). By adjusting the driving voltage along with optimizing the drive waveform, the droplet volume and velocity can be controlled and evaluated by a drop watcher system. As a result, inkjet printhead capable of ejecting 1 pL droplet, which is required by electronic applications such as fabricating metal lines on printed circuit board (PCB), is developed.
Selective Formation of a SnO2 Cap Layer, Its Growth Behavior, and Oxidation Resistance
Authors: Fujii Yoshihito , Koike Junichi , Sutou Yuji , Li Zifeng , Neishi Koji
Published: May 2010

In this paper, we propose a new method of cap-layer formation. The cap layer of SnO2 is formed by the displacement plating of Sn, followed by the oxidation of the plated Sn. An excellent plating selectivity was found between Cu and SiO2, but not with SiOCH. The SnO2 layer of 90 nm thickness showed a good oxidation resistance of the underlying Cu after heat treatment at 480 °C in air (P
O2=105 Pa). In contrast, the SnO2 layers of 6 and 9 nm thickness showed oxidation resistance at 400 °C in Ar+10 ppm O2 (P
O2=1 Pa), but not in Ar+1000 ppm O2 (P
O2=100 Pa).
A 3 nm Self-Forming InOx Diffusion Barrier for Advanced Cu/Porous Low-k Interconnects
Authors: Perng Dung-Ching , Hsu Kuo-Chung , Yeh Jia-Bin
Published: May 2010

The copper diffusion barrier properties of a 3 nm self-forming InO
x
layer on a porous ultralow-k (p-ULK) film have been investigated. A 5 at. % In doped Cu film was directly deposited onto porous low-k films by co-sputtering, followed by annealing at various temperatures. Transmission electron microscopy (TEM) images showed that a 3 nm layer was self-formed at the interface between Cu–In and p-ULK films after annealing at 400 °C for 1 h. An EDS line scan on the region near this interface showed obvious accumulation of In at the interface. X-ray photoelectron spectroscopy (XPS) analyses indicated that the self-formed interfacial layer was InO
x
. The self-forming InO
x
layer prevented Cu agglomeration on the p-ULK film surface. The XPS atomic depth profiles showed that the self-formed InO
x
barrier was thermally stable against Cu diffusion to at least 500 °C for 5 h. The sheet resistance of the post 500 °C annealed Cu–In film was comparable to that of a pure Cu film. The Cu–In self-forming barrier approach may be a viable candidate for Cu/p-ULK interconnects.
Initial Cu Growth in Cu-Seeded and Ru-Lined Narrow Trenches for Supercritical Fluid Cu Chemical Deposition
Authors: Kondoh Eiichi , Matsubara Masahiro , Tamai Kakeru , Shimogaki Yukihiro
Published: May 2010

The morphological stability of Cu films in narrow trenches during the initial growth of Cu was studied at temperatures of 140–280 °C for the chemical deposition of Cu in supercritical CO2. Cu seed layers agglomerated and the deposited Cu and the seed layer coalesced at elevated temperatures. This mechanism resulted in bottom-up like growth at lower temperatures of 160–180 °C. The seed agglomeration was suppressed by starting deposition before reaching the temperature at which agglomeration started of about 150 °C. When Ru-lined trenches were used instead of Cu-seeded trenches, no clear agglomeration or grain coarsening was observed and Cu grew with a conformal topography.
Formation of Palladium Silicide on Heavily Doped Si(001) Substrates Using Ti Intermediate Layer
Authors: Suryana Risa , Nakatsuka Osamu , Zaima Shigeaki
Published: May 2010

The formation of palladium silicide on Pd/Ti/Si systems with and without heavy B-doping has been investigated. For comparison, Pd2Si was also formed on Pd/Si systems. The agglomeration of Pd2Si could be retarded in Pd/Ti/Si systems with and without B-doping after annealing at 600 °C. The existence of the Ti layer could improve the thermal stability of Pd2Si. In addition, epitaxial or highly oriented Pd2Si formed in Pd/Ti/Si systems. The two orientation relationships of Pd2Si layers were identified to be Pd2Si[110]∥Si[110] and Pd2Si[110]∥Si[001], and Pd2Si[100]∥Si[110] and Pd2Si[001]∥Si[001]. The formation of strained epitaxial Pd2Si layers was found in Pd/Ti/Si systems. The improvement in the thermal stability of Pd2Si and the formation of epitaxial or highly oriented Pd2Si in Pd/Ti/Si systems were observed with and without B-doping.
Plasma-Enhanced Atomic Layer Deposition of Cobalt Using Cyclopentadienyl Isopropyl Acetamidinato-Cobalt as a Precursor
Authors: Kim Jae-Min , Lee Han-Bo-Ram , Lansalot Clement , Dussarrat Christian , Gatineau Julien , Kim Hyungjun
Published: May 2010

Cobalt plasma-enhanced atomic layer deposition (PE-ALD) using cyclopentadienyl isopropyl acetamidinato-cobalt [Co(CpAMD)] precursor and NH3 plasma was investigated. The PE-ALD Co thin films were produced well on both SiO2 and Si(001) substrates. The deposition characteristics and films properties such as resistivity, chemical bonding states and quantitative impurity level contents were investigated. Especially, Co deposition using this precursor was possible at very low growth temperature as low as 100 °C, which enable the deposition on polymer-based substrate. We demonstrate that this low growth temperature PE-ALD can be applicable to patterning of Co film by lift-off method, which was realized by direct deposition of Co on photoresist patterned substrate.
Effects of Water Desorption from SiO2 Substrates on the Thickness of Manganese Oxide Diffusion Barrier Layer Formed by Chemical Vapor Deposition
Authors: Matsumoto Kenji , Neishi Koji , Itoh Hitoshi , Miyoshi Hidenori , Sato Hiroshi , Hosaka Shigetoshi , Koike Junichi
Published: May 2010

A manganese oxide (MnO
x
) diffusion barrier layer was formed by chemical vapor deposition (CVD) on SiO2 substrates with or without preannealing. The thickness dependence of the MnO
x
layer was investigated in relation to the desorption behavior of water vapor from the substrates. A good correlation was found between MnO
x
thickness and the amount of desorbed water vapor. It is necessary to control the amount of absorbed water in the substrate to form a thin MnO
x
barrier layer with good thickness reproducibility.