bluuebunny/crossref_metadata_2025 huggingface dataset:
A MODIFIED SUB-CELL-FIX METHOD FOR RE-INITIALIZATION OF LEVEL-SET DISTANCE FUNCTION AND ITS DEPENDENCE TESTS ON GRID STRETCHING
Authors: SUN MING BO , BAI XUE SONG , LIU WEI DONG , LIANG JIAN HAN , WANG ZHEN GUO
Published: June 2010

The sub-cell-fix (SCF) method proposed by Russo and Smereka3 computes the distance function of the cells adjacent to the zero level-set without disturbing the original zero level-set. A modified sub-cell-fix scheme independent of local curvature is developed in this paper, which makes use of a combination of the points adjacent to zero level-set surfaces and preserves the interface in a second-order accuracy. The new sub-cell-fix scheme is capable of handling large local curvature, and as a result it demonstrates satisfactory performance on several challenging test cases. The limitations of the modified scheme on stretched grids are tested and it is found that the highly stretched grid causes large numerical errors, and needs further assessment and modification.
CALCULATION AND ANALYSIS OF ELECTRICAL BEHAVIOR IN DISORDERED SEMICONDUCTING POLYMERS BASED ON EXTENDED GAUSSIAN DISORDER MODEL
Authors: WANG L. G. , ZHANG H. W. , TANG X. L. , MU C. H.
Published: June 2010

We calculate and analyze some electrical properties of semiconducting polymers in detail based on the extended Gaussian disorder model.10 It is shown that the carrier density at the interface (the boundary carrier density) has an important influence on the current–voltage (J–V) characteristics. Too large or too small values of the boundary carrier density will lead to incorrect J–V characteristics. Additionally, we show that numerically calculated carrier density is a decreasing function of the distance from the interface, and the slope of curves decrease with the increasing boundary carrier density. On the other hand, numerically calculated electric field is an increasing function of the distance and the slope of curves increase with the increasing boundary carrier density. Furthermore, it is also shown that both the maximum of carrier density and the minimum of electric field appear near the interface. These results are in accordance with the experimental measurements and the simulation results.
QUANTUM DOT GEOMETRY AS A DESIGNING TOOL FOR DOT-IN-A-WELL STRUCTURES
Authors: BATENIPOUR NASRINDOKHT , SAGHAFI KAMYAR , MORAVVEJ-FARSHI M. K.
Published: June 2010

In this paper, we report results of our investigation on the effect of quantum dot (QD) geometry on desirable properties of a dot-in-a-well (DWELL) structure. Our simulation results reveal that QD geometry plays a key role in tuning the electronic properties of DWELL structure and can be employed as a designing tool. The structure under investigation consists of an InAs QD confined in an InGaAs well of size ~12.3 nm which in turn is sandwiched in a GaAs bulk. Using the path integral Monte Carlo (PIMC) method, we calculate the electronic properties of DWELL structure for QDs of spherical, ellipsoidal, and conical shapes. We demonstrate the dependence of the electron energy on QD geometry. We show that although the stronger confinement within the conical quantum dot (CQD) forces its maximum capacity (N max ) to be smaller than those of the spherical quantum dot (SQD) and ellipsoidal quantum dot (EQD), the overall maximum capacity of a DWELL with conical dot (CDWELL) is larger than those of the DWELLs with spherical and ellipsoidal dots (SDWELL and EDWELL). Moreover, we show that the electron distribution within the structure is a strong function of the QD geometry inside the well.
Investigation of Spacer Engineering on n-Type Field Effect Transistor Performance during Laser Spike Annealing
Authors: Huang Chien-Chao , Chen Hao-Yu , Lee Sanboh
Published: June 2010

A new liner oxide spacer structure of n-type field effect transistors (n-FETs) with a favorable stress optimum has been investigated to improve the crystallization in the amorphous area of the source–drain extension (SDE) implantation during laser spike annealing. The dopant activation performance of n+ polycrystalline silicon is identical to the sheet resistance judgement for two spacer schemes of n-FETs devices, but the junction leakage of the oxide liner spacer is lower than that of the conventional composite spacer. The stress within SDE depth induced by the spacer is changed from compressive to tensile stress when the conventional composite spacer was replaced by the oxide liner spacer.
Effect of Dopant, Crystal Orientation, and Space Charge Layer on Oxygen Diffusion in Bi4Ti3O12Ceramics
Authors: Sakaguchi Isao , Matsumoto Kenji , Nagata Hajime , Hiruma Yuji , Haneda Hajime , Takenaka Tadashi
Published: June 2010

We studied oxygen diffusion in non- and Nb2O5-doped Bi4Ti3O12(BIT) ceramics by two-dimensional isotope mapping. In non-doped BIT, the grain boundary acted as a barrier to oxygen diffusion, reflecting the presence of a space charge layer at the grain boundary. In Nb2O5-doped BIT, a textured morphology was found by bulk and grain-boundary diffusion of oxygen. Diffusion coefficients were determined from the individual grains and grain boundaries. The difference in diffusion paths resulted from the decrease in oxygen-defect concentration owing to the addition of Nb2O5. The bulk-diffusion coefficient along theab-plane was about one order of magnitude larger than that in the direction of thec-axis. The grain-boundary-diffusion coefficients varied by about two orders of magnitude. The bulk and grain-boundary diffusion of oxygen depended significantly on the crystal orientation.
Liquid-Crystal Blazed Gratings with Spatially Distributed Pretilt Angle
Authors: Honma Michinori , Nose Toshiaki , Yanase Satoshi , Yamaguchi Rumiko , Sato Susumu
Published: June 2010

An electrically tunable liquid-crystal (LC) blazed grating was demonstrated by introducing a periodic pattern of pretilt angle that was controlled by adjusting the rubbing density. In the proposed LC grating, an asymmetrically varying LC molecular orientation was realized even without voltage application. The diffracted light intensity was controlled by adjusting the applied voltage, and the diffraction effect disappeared under a sufficiently high applied voltage. Asymmetric diffraction patterns were obtained and it was revealed that 0th-, 1st-, and 2nd-order diffraction beams can be switched with an appropriate applied voltage. A maximum diffraction efficiency of 0.68 for the 1st-order diffraction was experimentally obtained; however, it is much less than the theoretical limit of unity. It is likely that the difference between optical path lengths for extraordinary and ordinary rays is not linearly distributed.
Application of Commercially Available Liquid Crystal Polymer Films for the Improvement of Color and Viewing Angle Performance of Twisted Nematic Devices
Authors: Sergan Tatiana A. , Lavrentovich Marina D. , Kelly Jack R. , Kameyama Tadayuki
Published: June 2010

In our work we analyzed the optical performance of liquid crystal polymer films by Nippon Mitsubishi Oil and by Fuji Film. We applied the films for twisted nematic (TN) display compensation and found several non-traditional display configurations. One display configuration employs flipped Nippon Mitsubishi Oil films mounted on polarizers, the second one, a combination of both types of films on one TN side and two crossed uniaxial films on the other. The compensated devices demonstrate greatly improved optical characteristics that surpass all those previously known, utilize the commercially available films, and are experimentally verified.
Changes in Chemical and Structural Properties of Phase-Change Material GeTe with Nitrogen Doping and Annealing
Authors: Kim Ki-Hong , Choi Sang-Jun , Chung Jae-Gwan , Lee Jun-Ho , Heo Sung
Published: June 2010

In this study, changes in the chemical, structural, and electrical properties of undoped and 8.4 at. % nitrogen-doped GeTe films were investigated. The transition temperature of sheet resistance increased as a result of nitrogen doping, which corresponded well with phase transformations. The shift of chemical potential toward lower binding energies strongly depended on crystallization. The Ge/Te ratio showed a tendency to increase towards the surface only for undoped GeTe. Nitrogen doping may suppress the instability of GeTe.
Experimental Investigation of First Hyperpolarizability by a Prism Coupling Waveguide Method
Authors: Pan Kankai , Deng Xiaoxu , Li Honggen , Yuan Wen , Wei Wei , Liu Feng
Published: June 2010

The complex first hyperpolarizability of chromophore for electrooptic effect has been determined by a prism coupling waveguide method. By measuring the field-induced changes in the reflected intensity of the prism–waveguide coupling system at different guided wave resonance dips, the real and imaginary parts of the first hyperpolarizability of the chromophore are simultaneously obtained without using the Kramers–Kronig transformation.
Special Laser Wavelength Generation Using a Volume Bragg Grating as Nd:GdVO4 Laser Mirror
Authors: Chung Te-Yuan , Liao Chien-Jung , Lien Yu-Hung , Yang Sideny S. , Shy Jow-Tsong
Published: June 2010

A 1071 nm laser using Nd:GdVO4 as the gain medium is demonstrated. A volume Bragg grating (VBG) with a reflection central wavelength at 1069.8 nm was used. The laser was operated in CW mode. The output wavelength range could exceed 1.3 nm by tuning the VBG temperature. Single longitudinal mode operation was achieved with an output power larger than 100 mW using a simple linear cavity setup. A brief discussion about the VBG thermal effect is also presented.
Polarization Characteristics Variation of Visible Light on Reflection from ZnO Based Amorphous Films
Authors: Misra Kamakhya Prakash , Srivastava Atul , Shukla R. K. , Misra P. , Srivastava Anchal
Published: June 2010

The change in polarization characteristics of visible light reflected from amorphous ZnO and Ca doped ZnO thin films were studied. Highly transparent thin films of ZnO and Ca doped ZnO were deposited on glass substrate by sol–gel spin coating technique. Reflection studies revealed that the change in the polarization state and azimuth of the electric vector introduced by sample films are quite different as compared to those for reflected beam from uncoated substrate. The rotation of electric vector in reflected light was found to depend considerably on variation in angle of incidence as well as Ca concentration in ZnO. Films, interestingly, changed the incident plane polarized light to elliptically polarized on reflection.
Internal Stress and Microstructure of Zinc Oxide Films Sputter-Deposited with Carbon Dioxide Gas
Authors: Ashida Toru , Kato Kazuhiro , Omoto Hideo , Takamatsu Atsushi
Published: June 2010

The internal stress and microstructure of ZnO films were investigated as a function of carbon dioxide (CO2) gas flow ratio [CO2/(O2+CO2)] during sputter deposition. The internal stress of the ZnO films decreased with increasing CO2 gas flow ratio. The carbon concentration in the films deposited using CO2 gas increased by up to 4.0 at. %. Furthermore, the ZnO films deposited without CO2 gas exhibited a preferred orientation of (002); however, the C-doped ZnO films exhibited random orientations. These findings suggest that the C atoms incorporated in the ZnO crystal lattice induce this random orientation, thereby relaxing the internal stress of C-doped ZnO films.
Characterization of CsLiB6O10 Crystal Grown in a Dry Atmosphere
Authors: Kawamura Takahiro , Shimizu Yohei , Yoshimura Masashi , Fukushima Yuji , Nishioka Masato , Kaneda Yushi , Kitaoka Yasuo , Mori Yusuke , Sasaki Takatomo
Published: June 2010

We grew CsLiB6O10 (CLBO) crystals in a dry atmosphere to obtain high-quality crystals that include less water as an impurity. We estimated the level of water impurity in the crystals using a nonpolarized Fourier transform infrared spectrometer and also measured bulk laser damage resistance using a 266 nm high-repetition-rate ultraviolet pulse laser. We found that the CLBO crystals grown in a dry atmosphere had an approximately 80% less water impurity and 1.2- to 1.5-fold greater resistance to laser damage than the CLBO crystals grown in an ambient atmosphere.
Intensity Flow Estimation of Thin Film Transistor Liquid Crystal Display Panel Surface Image Using Multiweighted Morphology Pairs
Authors: Kim Se-Yun , Jung Chang-Do , Song Young-Chul , Park Kil-Houm
Published: June 2010

In this paper, we present a new image enhancement method for a vision-based automated defect inspection system on the surface image of a thin film transistor liquid crystal display (TFT-LCD) panel. The TFT-LCD image has nonuniform brightness, which is a major difficulty in finding defective regions. The proposed method effectively estimates the nonuniform intensity variation except in defective regions using multiweighted morphological filters. After estimation, defects can be segmented easily using difference from the original image. Experimental results verified the performance of the proposed method.
Patterning of Two-Dimensional Graphene Oxide on Silicon Substrates
Authors: Ishikawa Ryousuke , Bando Masashi , Morimoto Yoshitaka , Park Sang Yoon , Sandhu Adarsh
Published: June 2010

Chemically synthesized graphene is promising for device applications because the chemical approach enables ease of mass production and chemical modification of its properties. However, a major drawback of graphene based devices is that it is difficult to integrate the small flakes of graphene into device architectures. In order to overcome this limitation, we describe a simple procedure for patterning graphene oxide (GO) flakes onto predefined locations of silicon substrates. We exploited the negatively charged surface of GO flakes, and successfully patterned GO flakes onto photolithographically defined positively charged regions on silicon substrates. We demonstrate the simultaneous fabrication of multiple GO flakes device structures by controlling the surface chemistry of substrates. Our procedure for the precise positioning of GO flakes will be an important step in the fabrication of graphene devices.
Disturbance Effects in Extreme Ultraviolet Interferometric Lithography Affecting Interference Fringes
Authors: Saib Mohamed , Constancias Christophe , Michallon Philippe , Dalzotto Bernard , Besacier Maxime
Published: June 2010

We set up an extreme ultraviolet (EUV) interferometer lithography tool dedicated to the study of the photoresist properties at the EUV wavelength. Two coherent beams are recombined to generate a standing wave, which can be recorded in a photoresist. However, other physical phenomena are generated by the interferometer structure which can disturb the quality of interference fringes. The Fresnel effect is one of these phenomena which is fully detailed in this work. Accurate numerical models have been compared to experimental studies to quantify the reduction of the interference area by the Fresnel effect. Depending on the Fresnel number (N
F), several advantageous conditions are presented in order to reduce the Fresnel disturbance on resist.
Development of Extreme Ultraviolet Interference Lithography System
Authors: Fukushima Yasuyuki , Sakagami Naoki , Kimura Teruhiko , Kamaji Yoshito , Iguchi Takafumi , Yamaguchi Yuya , Tada Masaki , Harada Tetsuo , Watanabe Takeo , Kinoshita Hiroo
Published: June 2010

Extreme ultraviolet interference lithography was carried out at the long undulator beamline in NewSUBARU. It was confirmed that the spatial coherence length is 1.1 mm using a 10-µm-wide slit in the Young's double slit experiment. A 25-nm half pitch (hp) resist pattern was successfully replicated by extreme ultraviolet interference lithography (EUV-IL) utilizing a two-window transmission grating pattern of a 50-nm line and space (L/S). For the replication of a 20-nm L/S resist pattern by EUV-IL, we contrived a fabrication process that is suitable for a transmission grating pattern of 40-nm L/S and smaller. Employing a hard-mask process with a silicon dioxide (SiO2) layer on a tantalum–nitride (TaN) layer in the fabrication of a two-window transmission grating, we successfully achieved five times larger dry-etch selectivity in comparison with a non-hard-mask process. As a result, we confirmed the ability to apply this process to a 40-nm hp grating.
Imaging Performance Improvement of an Extreme Ultraviolet Microscope
Authors: Takase Kei , Kamaji Yoshito , Sakagami Naoki , Iguchi Takafumi , Tada Masaki , Yamaguchi Yuya , Fukushima Yasuyuki , Harada Tetsuo , Watanabe Takeo , Kinoshita Hiroo
Published: June 2010

The extreme ultraviolet microscope (EUVM) has been developed for an actinic mask inspection of a EUV finished mask and a EUV blank mask. Using this microscope, amplitude defects on a finished mask and phase defects on a glass substrate are observed. However, it has a problem of low contrast, which originates from 1) thermal noise of a charge coupled device (CCD) camera, 2) wave aberrations of an optical component, and 3) a nonuniform illumination intensity. To resolve these issues, EUVM was improved. 1) To reduce a thermal noise, a cooled CCD camera is installed. 2) To remove wave aberrations of a back-end turning mirror, a Mo/Si multiplayer-coated thick glass substrate with a high surface accuracy is employed instead of a Si wafer substrate. Furthermore, in situ alignment was carried out to remove wavefront aberrations for a Schwarzschild imaging optics. In addition, 3) by installing a scanning system on the front-end turning mirror, a highly uniform illumination intensity was achieved. As a result, images of less than 100 nm without astigmatism were obtained.
Fresnel Zone Plate Manufacturability Analysis for Direct-Write Lithography by Simulating Focusing and Patterning Performance versus Fabrication Errors
Authors: Tsai Kuen-Yu , Chen Sheng-Yung , Pei Ting-Han , Li Jia-Han
Published: June 2010

Zone plate array lithography (ZPAL) in the X-ray or EUV regimes is one possible next-generation lithography solution because of its potential for high-resolution and maskless operation. To achieve a high throughput, Fresnel zone plates (FZPs) are integrated to form arrays of massively parallel exposure beams. FZP fabrication errors and uniformity can be serious issues in ZPAL systems, which are usually assembled and tested directly after zone plate arrays (ZPAs) are fabricated. The yield of this approach can decrease significantly with increasing beam number. A new ZPA design-to-manufacture flow that takes fabrication errors into account before the assembly process is proposed. The errors can be clearly screened by rigorous optical and lithography simulations. The effectiveness of the proposed approach is demonstrated by analyzing preliminary FZP designs of different zone numbers subject to imperfect zone width control. Simulation results indicate that FZPs with smaller zone numbers can tolerate larger radius deviations.
A Study of Flare Variation in Extreme Ultraviolet Lithography for Sub-22 nm Line and Space Pattern
Authors: Lee Junhwan , Song Kangyoo , Kim Changreol , Kim Yongdae , Kim Ohyun
Published: June 2010

One of the critical issues in extreme ultraviolet lithography (EUVL) is flare, which is an integrated light scattering from surface roughness in the EUVL optical system. Flare degrades the control of critical dimension (CD) uniformity across the exposure field. Also, it generates larger CD sensitivity as line and space (L/S) half pitch size decreases. Therefore, we discussed the calculation of accurate flare maps to compensate for flare variation. The influence of three-dimensional (3D) mask topography on flare was investigated with different absorber thicknesses, off-axis illumination angles, and azimuthal angles. Some types of dummy patterns were found to be effective in controlling the flare variation within a L/S patterned target and the average flare of a L/S patterned target. Our studies has definitely made progress in an effective flare variation compensation using a rule-based correction for sub-22 nm L/S half pitch node and beyond.
Electron Beam Recorder for Patterned Media Mastering
Authors: Kitahara Hiroaki , Uno Yuhei , Suzuki Hiroaki , Kobayashi Takashi , Tanaka Hiroshi , Kojima Yoshiaki , Kobayashi Masaki , Katsumura Masahiro , Wada Yasumitsu , Iida Tetsuya
Published: June 2010

Patterned media are promising technologies to realize the next-generation hard disk drives (HDD) with an areal density beyond 1 Tbit/in.2. Two types of patterned media have been proposed: one is the discrete track medium (DTM) and the other is the bit-patterned medium (BPM). Both DTM and BPM require very small feature sizes and extremely tight tolerances. The mastering process is a key technology for production of patterned media, and electron beam mastering is the only means to carry out the process. We developed a new electron beam recorder (EBR) for patterned media mastering. In this paper, we introduce the technologies and the recording performance of the EBR. The EBR has four primary technical features: a 100 kV EB column, a high-precision r–θ stage system, a stage error correction system, and an EBR formatter for patterned media. In experimentals, the EBR demonstrated the following recording performance. The EBR achieved sufficient recording accuracy for the requirements of DTM with 1 Tbit/in.2 areal density. The EBR succeeded in high-density recording of a DTM pattern with 35-nm track pitch for over 1.5 Tbit/in.2 areal density. The EBR showed high throughput and good recording stability by recording a 1.8-in. DTM master. In this experiment, the EBR achieved a line width uniformity of less than 1 nm and a short exposure time of about 50 h for whole-area recording. We proved the practicality of the EBR for patterned media production.
Manufacturability Analysis of a Micro-Electro-Mechanical Systems–Based Electron-Optical System Design for Direct-Write Lithography
Authors: Chen Sheng-Yung , Chen Shin-Chuan , Chen Hsing-Hong , Tsai Kuen-Yu , Pan Hsin-Hung
Published: June 2010

Multiple-electron-beam–direct-write lithography is one promising candidate for next-generation lithography because of its high resolution and ability of maskless operation. To achieve the throughput for high-volume manufacturing, miniaturized electro-optics elements are utilized to drive massively parallel beams simultaneously. Fabrication errors and uniformity of the elements can be serious issues in multiple-beam systems. Traditionally, electron optical systems (EOSs) are assembled and tested directly after the elements are fabricated. The yield by this technique can degrade significantly with multiple beams. In this work, a new EOS design-to-manufacturing flow which takes fabrication errors into account before the assembly process is proposed. The errors and imperfect components can be clearly screened by rigorous electron trajectory simulation. The effectiveness of the proposed approach is demonstrated with an fabricated electron-optical-objective-lens subject to imperfect hole profiles and substrate topography. Simulation results indicate that its EOS performances are acceptable even with significant fabrication errors.
Design and Fabrication of Multi-Aperture Plate for Multi-Ion Beam Patterning System
Authors: Choi Yeonsoon , Kim Tae-Gon , Han Jin , Min Byung-Kwon , Kim Young-Joo , Lee Sang Jo
Published: June 2010

For the multi-ion beam patterning system, it is necessary to develop a multi-aperture plate with a beam-controllable aperture device for individual adjustment of multi-ion beams on the stage. It is important to select the appropriate material for the multi-aperture plate to confirm the durability against damage by ion beams since the multi-aperture is located under a relatively strong ion beam. To prepare the controllable aperture system on the bottom side of the multi-aperture plate, the materials must be suitable for the microfabrication process. From an experimental etching test of some candidate materials, a silicon substrate with a magnesium oxide coating was selected for the multi-aperture plate. The structure also includes a Mo mesh on the top surface to solve the surface charging problem caused by ion beams, resulting in improved ion beam penetration through the aperture. Finally, a beam-controllable aperture device was designed with embedded parallel electrodes for durable and stable beam control and fabricated by the silicon microfabrication process.
Fluorinated-Polymer Based High Sensitivity Extreme Ultraviolet Resists
Authors: Santillan Julius Joseph , Yamashita Tsuneo , Morita Masamichi , Tanaka Yoshito , Itani Toshiro
Published: June 2010

There is a growing interest in the fluorinization of resist materials in improving pattern formation efficiency for extreme ultraviolet (EUV) lithography. The increased polymer absorption coefficient obtained through this resist platform is expected to enhance acid production and in effect improve pattern formation efficiency. Based on this, a EUV resist which was synthesized by co-polymerizing tetrafluoroethelyne (TFE) and functional norbornene derivative was investigated. Relatively high sensitivity of 6.3 mJ·cm-2 for half-pitch (hp) 45 nm and satisfactory resolution limit of hp 40 nm was achieved. However, at present, line width roughness (LWR) was measured at comparatively large values of more than 8.4 nm at hp 45 nm. Further material and process optimizations may be necessary to improve its present lithographic capability. However, these initial results have shown the potential of fluorinated-polymer based platform as a possible solution for high sensitivity, high resolution and low LWR EUV resists.
Decomposition and Roughness Analysis of Chemically Amplified Molecular Resist for Reducing Line Width Roughness
Authors: Shiono Daiju , Hada Hideo , Sato Kazufumi , Fukushima Yasuyuki , Watanabe Takeo , Kinoshita Hiroo
Published: June 2010

A molecular resist material, which includes only one protecting group per molecule was designed and synthesized as Prot-1. After confirming the structure and purity of Prot-1, resist A formulated with Prot-1 as a base material was prepared. Resist A showed a good contrast curve. To confirm the decomposition behavior by an electron beam (EB) exposure, resist A was analyzed using high performance liquid chromatography (HPLC). From the HPLC analysis, it was found that the dissolution switching of resist A due to EB exposure was caused by a deprotection reaction of Prot-1. We evaluated the resolution and line edge roughness (LER) of resist A using EB lithography. Resist A showed 25 nm half pitch (hp) resolution and a partially resolved 20 nm hp at an exposure dose of 36 µC/cm2 using an EB writing system with an acceleration voltage (V) of 50 kV. The LER of resist A was 3.8 nm (3σ) for a 100-nm-hp line-and-space pattern, which is similar to a ZEP520A non chemically amplified resist. As a result, we confirmed that a uniform deprotection reaction of just one deprotection group of resist A in the exposed area improved LER and resolution.
Ambipolar Behavior in Epitaxial Graphene-Based Field-Effect Transistors on Si Substrate
Authors: Olac-vaw Roman , Kang Hyun-Chul , Karasawa Hiromi , Miyamoto Yu , Handa Hiroyuki , Fukidome Hirokazu , Suemitsu Tetsuya , Suemitsu Maki , Otsuji Taiichi
Published: June 2010

In this research, ambipolar behavior, which is one of graphene's unique characteristics, is studied for the epitaxial graphene formed on 3C-SiC grown on a Si substrate. The graphene channel is believed to be unintentionally p-type-doped at Dirac-point voltages of approximately +0.11 to +0.12 V. However, as drain voltage negatively increases, Dirac point voltage shifts. The drain current in the p-channel mode of operation saturates at a lower level than that in the n-channel mode of operation. These behaviors are caused by asymmetric carrier transport throughout channel-substrate heterojunctions (i.e., graphene, thin n-type SiC layer, and p-type Si substrate) and source/drain Schottky metal contacts. The interface between the p-type Si substrate and n-type SiC has a significant effect on transport in graphene channels. The results may be helpful for understanding transport in the device and for suppressing ambipolar operation, leading to a unipolar FET operation.
Computer Design of Source/Drain Extension Region Profile and Spacer Length in Tri-Gate Body-Tied Fin Field-Effect Transistors with High-k Gate Dielectrics
Authors: Song Jae-Joon , Moon Dae-hyun , Kim Ohyun
Published: June 2010

The influences of source/drain extension region engineering and high-k gate dielectrics on the device performance of tri-gate body-tied fin field-effect transistors (FinFETs) was investigated to achieve the International Technology Roadmap for Semiconductor (ITRS) projections for high-performance (HP) logic technology. The impact of lateral source/drain doping gradient (L
dg) and spacer length (L
sp) on short-channel effects (SCEs) was extensively analyzed by three-dimensional device simulation. Results show that a lateral doping gradient along with an appropriate spacer length not only can effectively control SCEs, resulting in a low off-current, but also can be optimized to achieve low values of intrinsic gate delay and high values of on-current. The ratio of spacer length to lateral doping gradient (L
sp/L
dg) between 2.7 and 4 is optimal for achieving a low intrinsic gate delay, a low off-current, and a high on/off-current ratio. The present work provides valuable design guidelines in the performance of tri-gate body-tied FinFETs with optimal source/drain extension region engineering and serves as a tool for optimizing important device and technological parameters.
Microwave Characterization of a Field Effect Transistor with Dielectrophoretically-Aligned Single Silicon Nanowire
Authors: Kang Myung-Gil , Ahn Jae-Hyun , Lee Jongwoon , Hwang Dong-Hoon , Kim Hee-Tae , Rieh Jae-Seong , Whang Dongmok , Son Maeng-Ho , Ahn Doyeol , Yu Yun-Seop , Hwang Sung-Woo
Published: June 2010

Microwave (MW) characteristics of a field effect transistor (FET) incorporating a single silicon nanowire (SiNW) were obtained from S-parameter measurements in the frequency range of 0.05 to 20 GHz. The single SiNW was aligned, using the alternating current (ac) dielectrophoresis alignment method, between the drain and source electrode forming a coplanar waveguide (CPW) structure. Analysis of the FET was performed using equivalent circuit modeling by advanced device system (ADS) simulation. By fitting the measured data with the simulation results, the parameters of the single SiNW FET were obtained and the cutoff frequency was derived.
Suppression of Fermi Level Pinning and Flat Band Voltage Shift by Inserting Diamond-Like Carbon at a High-k/SiO2 Interface in a Gate Stack Structure
Authors: Iwashita Yuta , Adachi Tetsuya , Itaka Kenji , Ogura Atsushi , Chikyow Toyohiro
Published: June 2010

Fermi level pinning (FLP) has been a major impediment to limiting flat band voltage (V
fb) shift in the metal/high-k gate stacks. This phenomenon occurs due to dipole formation at the high-k/SiO2 interface, caused by oxygen diffusion from the high-k oxide to the underlying SiO2. One method of eliminating FLP is to suppress oxygen diffusion through the high-k/SiO2 interface. Diamond-like carbon (DLC) has potential as an oxygen diffusion barrier, since it has an appropriate optical band gap and dielectric constant. After inserting DLC into a high-k/SiO2 interface, we found that FLP was suppressed, since we observed a less flat band shift before and after rapid thermal annealing in an oxygen atmosphere. We could also see a clear work function dependence, giving direct evidence of FLP elimination when using Pt and W in an HfO2/DLC/SiO2 gate stack.
Reactive Ion Etching of Si Using Ar/F2 Plasma
Authors: Matsutani Akihiro , Ohtsuki Hideo , Koyama Fumio
Published: June 2010

We investigated the Si dry etching process using Ar/F2 plasma. A vertical etching profile and a smooth etched surface, which satisfy the requirements for optical device fabrication, were obtained. The etching rate of Si was approximately 0.1 µm/min at 5 Pa and 150 W. We believe that Ar/F2 plasma etching is a very simple and useful process for fabricating Si-based optical devices, such as photonic crystals, narrow optical waveguides, and micro-electro-mechanical systems (MEMS). In addition, this etching process is suitable for the protection of the earth environment, because the global warming potential (GWP) of F is 0.
Structural Changes in Diamond-Like Carbon Films Fabricated by Ga Focused-Ion-Beam-Assisted Deposition Caused by Annealing
Authors: Kanda Kazuhiro , Okada Makoto , Kang Yuji , Niibe Masahito , Wada Akira , Ito Haruhiko , Suzuki Tsuneo , Matsui Shinji
Published: June 2010

The desorption processes of H and Ga from diamond-like carbon (DLC) film synthesized by focused-ion-beam chemical vapor deposition (FIB-CVD) were investigated by elementary analysis and local structure analysis after heat treatment under various conditions. The elementary composition of FIB-CVD DLC film was determined using a combination of Rutherford backscattering spectra and elastic recoil detection analysis spectra. Local structure analysis was performed by the measurement of near-edge X-ray absorption fine structure using synchrotron radiation. Desorption of H from FIB-CVD DLC film by heat treatment was found to comprise two types of process. One is the local graphitization along paths, where residual Ga atoms move by annealing. In this process, Ga acts as a catalyst for the graphitization of DLC. The other process is derived from the graphitization of the whole DLC film by heat, regardless of Ga. In this process, the sp2 content increases considerably.
Mechanical Characteristics of Nanosprings Fabricated by Focused-Ion-Beam Chemical Vapor Deposition Using Ferrocene Source Gas
Authors: Nakai Yasuki , Kang Yuji , Okada Makoto , Haruyama Yuichi , Kanda Kazuhiro , Ichihashi Tetsuya , Matsui Shinji
Published: June 2010

The mechanical characteristics of iron-containing nanosprings (Fe-containing nanosprings) fabricated by focused-ion-beam chemical vapor deposition (FIB-CVD) using a ferrocene (C10H10Fe) source gas were investigated. The shear and Young's moduli were 34 and 92 GPa, respectively. We also evaluated the annealing effect of Fe-containing nanosprings and observed a droplet containing Fe and Ga on the nanospring after annealing at 600 °C. The spring constant rapidly decreased after annealing at 600 °C. By scanning electron microscopy energy–dispersive X-ray spectroscopy (SEM–EDX) and transmission electron microscopy energy–dispersive X-ray spectroscopy (TEM–EDX) line analysis, it was confirmed that the decrease in the spring constant was due to Ga removal.
Electrostatic Deposition of Aerosol Particles Generated from an Aqueous Nanopowder Suspension on a Chemically Treated Substrate
Authors: Naim M. Nazli , Bakar Noor Fitrah Abu , Iijima Motoyuki , Kamiya Hidehiro , Lenggoro I. Wuled
Published: June 2010

The state of electrostatically deposited aerosol particles from a suspension that contains TiO2 particles on the surface of a solid substrate using electrospray was demonstrated. The particles were initially electrosterically stable in 7.5 wt % aqueous solution with a mean particle size of 50 nm. During deposition, the particles were pumped with different flow rates between 0.6 and 1.2 mL/h through a stainless steel capillary tube of 0.1 mm inner diameter. The particles were emitted at the tip of the capillary tube as an electrified liquid cone before forming into a highly charged droplet. For comparison, two types of substrate surfaces with and without chemical treatment were prepared. Atomic force microscopy (AFM) scanning and contact angle measurements showed that surface treatment increased the substrate roughness and created a hydrophilic surface. Raman analysis also showed the existence of an oxide layer and a P–O network on the treated substrate. Field emission scanning electron microscopy FE-SEM image analysis showed that more TiO2 particles were deposited on the treated substrate than on the untreated substrate.
Raman Scattering of Single-Walled Carbon Nanotubes in Early Growth Stages Using Laser-Irradiated Chemical Vapor Deposition
Authors: Tsuji Tomoki , Inoue Koichi , Ohno Yasuhide , Maehashi Kenzo , Matsumoto Kazuhiko
Published: June 2010

We have investigated the characteristics of single-walled carbon nanotubes (SWNTs) in early stages of growth by laser-irradiated chemical vapor deposition (LICVD) using an Ar-ion laser as a source of heat. Raman scattering spectroscopy measurements reveal that in the growth stages by LICVD, SWNTs with small diameters were mainly synthesized, while SWNTs with larger diameters were grown in a longer irradiation time. These phenomena were explained by the changes in catalyst nanoparticle size during the LICVD process. Suppressing the migration and coalescence of catalyst nanoparticles by pulsed post irradiation, the growth of only SWNTs with small diameters was promoted by pulsed post irradiation subsequent to catalyst nanoparticle formation in the early stages of growth by LICVD.
Growth Mechanisms and Characteristics of ZnO Nanostructures Doped with In and Ga
Authors: Yang Su-Hua , Hong Sheng-Yu , Tsai Cheng-Hsun
Published: June 2010

In this paper we present the crystallization, photoluminescence (PL), and field-emission (FE) properties of ZnO nanostructures doped with In and Ga cationic substituents and grown by the vapor-phase transport process. During the growth, Zn/ZnO
x
was adsorbed on the surface of Ag nanograins and self-catalyzed to form ZnO nanoparticles. Hexagonal-faced nanobricks and nanorods were grown by increasing the ZnO vapor concentration. However, nanodisks rather than nanobricks were grown when In2O3 was doped. Furthermore, the nanodisks aggregated to form nanoballs when the synthesis was carried out at high In2O3 doping concentrations. In contrast, nanostructures with a sea-urchin-like morphology were grown when Ga2O3 was doped; individual nanorods with a screw-dislocation structure grew from the same root. We present the growth mechanisms for the ZnO, ZnO:In, and ZnO:Ga nanostructures. ZnO:Ga nanorods exhibited better PL intensity and FE properties than ZnO nanorods and ZnO:In nanoballs.
Atomic and Electronic Structure Investigation and Luminescence Property of Eu2+-Doped β-SiAlON Green Phosphor: Ab initio Calculations
Authors: Yoo Dong Su , Ryu Jeong Ho , Park Hong-Lae , Lee Sung-Ho , Chung Yong-Chae
Published: June 2010

The atomic and electronic structure of Eu-doped β-SiAlON with various Al–O pair concentrations was calculated using density functional theory. The luminescence properties were analyzed by using quantitative calculation of the bandgap and the wavelength. Interstitially doped Eu ion was found near N atoms in the atomic channel parallel to the [0001] axis and the lattice parameters of the primitive cell became larger as the Al–O pair concentration increased. The additional states originated from the hybridization of Eu 4f with Si 3p and N 2p. The calculated wavelengths from the energy gap between the valance band maximum and the extra level was about 540 nm in the high Al–O pair concentration. The calculated results are well agreed with experimental results.
Mechanism of Enhanced Dispersion of Single-Walled Carbon Nanotubes with Proteins by Alcohols and Chaotropes
Authors: Hirano Atsushi , Maeda Yutaka , Akasaka Takeshi , Shiraki Kentaro
Published: June 2010

Protein–single-walled carbon nanotube (SWNT) conjugates have attracted remarkable attention for their application to biotechnology. However, low dispersion of the conjugates in aqueous solvents attributable to the strong interaction between sidewalls of SWNTs has limited their application. We previously reported that alcohols enhance the dispersion of single-walled carbon nanotubes with protein, but the mechanism has not been clarified. Herein we suggest a mechanism of the dispersion enhancement through a comparison of the effect of alcohols and chaotropes on the hydrophobic interaction of SWNTs, which shows that the adjuvants play an important role in the dispersion kinetics. The dispersion technique based on the mechanism provides us opportunities to develop a new field of applications and investigate physical properties of SWNTs.
Electron Spin Resonance Spectroscopic Study of Size-Controlled Ink Particles Isolated from Sepia officinalis
Authors: Matsuura Toshihiko , Watanabe Shingo , Akutagawa Sei-ichi , Shimoyama Yuhei , Kobayashi Takanori , Taya Yoshihiro , Ueno Takashi
Published: June 2010

The paramagnetic properties of size-controlled ink particles isolated from the ink sacs of Sepia officinalis were studied by electron spin resonance (ESR) spectroscopy. Both the size-controlled ink particles and synthetic melanins seemingly yielded similar ESR spectra consisting of a singlet with a slightly asymmetrical signal. However, the progressive microwave power saturation revealed a clear difference between their paramagnetic behaviors. In comparison with synthetic melanins, the ESR spectra of the ink particles readily reached saturation, indicating a long spin–lattice relaxation time. On the other hand, the ESR linewidth depended on particle size. This implies that the particle size is related to the distance between paramagnetic species in the particles. Hence, it is reasonable that the large ink particle has the weakest spin–spin interaction among these samples. The employment of the size-controlled ink particles enabled us to determine precisely the paramagnetic parameters of Sepia inks.
Structures and Electronic States of Water Molecules on Graphene Surface: A Density Functional Theory Study
Authors: Abe Shigeaki , Nagoya Yoshinori , Watari Fumio , Tachikawa Hiroto
Published: June 2010

Effects of water molecules on the electronic states of graphene have been investigated by means of density functional theory (DFT) and time-dependent DFT methods at the PW91PW91 and B3LYP/6-31G(d) levels of theory. Solvation caused by one to four water molecules (n=1–4) was examined in the present study. A graphene composed of 14 benzene rings was used as a model of finite-sized graphene (C42H16). The water molecules interact with the graphene surface via hydrogen bonding. The band gap of graphene was slightly red-shifted by the solvation. This shift was caused by the formation of hydrogen bonds between H2O and the graphene surface. The electronic states of the graphene–water system were discussed on the basis of theoretical results.
Fabrication of Nanochannels with High Aspect Ratios on a Silicon Substrate by Local Focused Ion Beam Implantation and Deep Reactive Ion Etching
Authors: Han Jin , Kim Tae-Gon , Min Byung-Kwon , Lee Sang Jo
Published: June 2010

Recently, demands for nanochannels have been increasing in biological and nanofluidic applications. In this paper, a fabrication process that produces a nanochannel with a width of less than 20 nm and a high aspect ratio is proposed. For the versatility of channel pattern design, focused ion beam (FIB) direct writing is applied for mask fabrication. A metal mask pattern is fabricated using localized ion implantation method and is used for a deep reactive ion etching (DRIE) process. A process condition for minimum undercut in the DRIE process is determined. The proposed method is applied to the fabrication of nanochannels with various dimension and patterns.
Effects of Environmental Gas in UV Nanoimprint on the Characteristics of UV-Curable Resin
Authors: Wang Qing , Hiroshima Hiroshi
Published: June 2010

In this study we investigated the effects of ambient gas on the characteristics of UV-curable resin in UV nanoimprint process by comparing the pattern transfer fidelity and residual layer thicknesses of the samples carried out in air and pentafluoropropane gas. We found that the resin pattern shrinkage induced by UV exposure was markedly affected by the ambient gas environment. The pattern shrinkage reached 22% in pentafluoropropane, while it reached only 3% in air. Also, the effects of pentafluoropropane on residual layer thickness were investigated. It was found that the residual layer using pentafluoropropane was much thinner than could be expected from the shrinkage induced by pentafluoropropane alone. We believe that the thinning of the residual layer is caused not only by shrinkage, but also by a decrease in the viscosity of UV-curable resin.
Room-Temperature Nanoimprinting Using Liquid-Phase Hydrogen Silsesquioxane with Hard Poly(dimethylsiloxane) Mold
Authors: Kang Yuji , Okada Makoto , Minari Chiaki , Kanda Kazuhiro , Haruyama Yuichi , Matsui Shinji
Published: June 2010

A new room-temperature imprinting method was developed using liquid-phase hydrogen silsesquioxane (HSQ) with a hard poly(dimethylsiloxane) (h-PDMS) mold. The simultaneous imprinting of arbitrary patterns including both submicron and greater than 100 µm patterns on a 4-in. wafer were replicated at room-temperature and a low pressure with high throughput, because the solvent in HSQ gradually evaporated through the pores of the h-PDMS mold. A bilayer structure was successfully fabricated using as HSQ pattern as an etching mask without removing the residual layer.
In situ Visualization of Imprinting Process for Patterning Microstructures on Glass Substrate
Authors: Chen Lien-Kai , Hung Yu-Min , Sung Cheng-Kuo
Published: June 2010

In this paper, we present anin situvisualization approach for investigating the formation mechanism of the imprinting process for patterning microstructures on a glass substrate. In the experimental study, K-PG375 was used as a glass substrate, and a mold with V-groove patterns was fabricated on glassy carbon. The microstructure profile corresponding to relative process parameters during imprinting was visualized using the proposed measurement system. Meanwhile, the finite element method (FEM) was also utilized to predict the formed microstructures at different stages. The visualized profile apparently indicated the filling behavior of glass flow during the imprinting process. Good agreement between FEM simulation and experimental results was achieved even though a slight difference between them was discovered because of calculation error from the experiment. As a result, comparison of the conditions, parameters, and results of FEM simulation with the experimental results can assist us profoundly in probing into many relative issues, such as the mechanism of microstructure formability on a glass substrate, the effect of process parameters on glass imprinting, and the pressure and velocity distribution of glass flow, which enable us to efficiently optimize the imprinting process.
Immobilization of Gold Nanoparticles on Aluminum Oxide Nanoporous Structure for Highly Sensitive Plasmonic Sensing
Authors: Hiep Ha Minh , Yoshikawa Hiroyuki , Taniyama Shunichi , Hoa Le Quynh , Kondoh Kenji , Saito Masato , Tamiya Eiichi
Published: June 2010

In this work, we investigate the optical properties of a nanostructure design with plasmonic gold nanoparticles (AuNPs) and photonic thin-film multilayers of aluminum oxide on an aluminum film. An aluminum oxide nanoporous surface fabricated by the two-step anodizing method is treated with cationic poly(allyl amine) to fix AuNPs on the surface. The porous nanostructure partially trapped two nanoparticles, producing a small number of nanoparticle dimers on the substrate surface. The experimental and simulation results show that the plasmonic spectra of these gold nanoparticle dimers (AuNDs) are enhanced by the interference spectra of the Al2O3/Al multilayer. On the basis of the longitudinal localized surface plasmon resonance (LSPR) band of AuNDs, our nanostructure substrate showed a high sensitivity to various solutions with different refractive indices, thus showing promising potential for the to development of a new nanosensor for the label-free monitoring of biomolecular interactions.