bluuebunny/crossref_metadata_2025 huggingface dataset:
Aerodynamic Stabilization of Flexible Optical Disk with Triangularly Arranged Stabilizer System
Authors: Aman Yasutomo , Onagi Nobuaki , Murata Shozo , Uchida Keisuke
Published: July 2005

We have developed a flexible optical disk (FOD) system comprising a flexible disk and stabilizer, which can achieve a small axial runout of the disk through simplified stabilizer control. The approach adopts a new stabilizer system made up of triangularly arranged stabilizers (TASs), which consists of one main stabilizer (MS) that stabilizes the pickup focus area on the disk and two auxiliary stabilizers (ASs) that control the balancing conditions around the MS. We experimentally demonstrated that the TAS system could effectively stabilize a flexible disk even under conditions with no active stabilizer adjustments, such as axial position control and tilt control, which could not be eliminated in our previous single-stabilizer system. The suppressed axial runout without active adjustments was sufficiently small of less than 5 µm at linear velocities from 5.7 to 13.0 m/s up to double the speed of Blu-ray disk system. The results indicated that the FOD system with the TASs, which is easily operated, could be implemented in high-density optical disk systems with a high numerical-aperture (NA) pickup.
Wavelength Margin Analysis in Advanced Collinear Holography
Authors: Horimai Hideyoshi , Tan Xiaodi , Li Jun , Suzuki Kenji
Published: July 2005

The wavelength margin of advanced collinear holography, which utilizes co-axially aligned information and reference beams modulated by the same spatial light modulator simultaneously, is analyzed and compared that of conventional 2-axis holography. Being the large wavelength margin, a laser diode as a light source of the holography is possible.
Low-Density Parity-Check Coding for Holographic Data Storage
Authors: Hayashi Hideki , Kimura Kazuhiko
Published: July 2005

Since the signal-to-noise ratio (SNR) of a holographic storage system is one of the dominant factors that determine the recording capacity, an improvement in SNR is crucial to the achievement of a high recording capacity. We therefore applied a low-density parity-check (LDPC) code and its soft iterative decoding to a holographic storage system. We examined the bit error rate (BER) performance by simulation and experiment, using the LDPC code as an error correction code and a 2:4 modulation code as a recording code. The simulation revealed that the LDPC code shows an SNR improvement of 5.3 dB and a coding gain of 4.8 dB at a BER of 1×10-5. The experiment indicated that an LDPC decoder completely corrects bit errors in a signal, which is reproduced from a recorded hologram, with an SNR of 12.5 dB and a raw BER of 1.3×10-2. The LDPC coding is thus effective in achieving a high recording capacity.
Adaptive Equalization Using Expanded Maximum-Likelihood Detector Output for Optical Recording Systems
Authors: Lee Joohyun , Lee Jaejin
Published: July 2005

For high-density optical recording systems, the effectiveness of the partial–response maximum-likelihood (PRML) detection scheme is limited by the channel asymmetry. Hence, to solve the problem and improve detection performance, we present an adaptive equalization scheme using the output of an expanded maximum-likelihood (ML) detector. The proposed PRML detection method adapts well to the asymmetric optical recording channels and has better bit error rate performance than the conventional PRML detection method.
A New Approach for Estimating the Life Expectancy of Optical Disk for Digital Archival Storage
Authors: Okino Yoshihiro , Irie Mitsuru , Kubo Takahiro
Published: July 2005

In this study, we examine a lifetime estimation method for optical disks using the Eyring acceleration model and statistical analysis. The standardized life expectancy of an optical disk is defined as its minimum lifetime at a 95% survival probability and a 95% confidence level under disk conditions in terms of its degree of usage. We confirmed the capability of this method of estimating life expectancy by considering the stresses of temperature and relative humidity, and providing a confidence level.
Automatic Write Strategy Setting
Authors: Nakajo Yukihisa , Roh Junki
Published: July 2005

Recently, various types of recordable optical disc have been distributed worldwide. Despite their popularity, the adjustment of write strategy for optimal recording is still a complex and time-consuming operation. In this study, our group focused on deviation, a parameter of the write strategy setting, and developed a method in which a write strategy calculation can be performed by making the value of this deviation close to 0. As a result, we can set up the optimum write strategy in 10 min.
Near-Field Optical Flying Head with Protruding Aperture and Its Fabrication
Authors: Hirata Masakazu , Oumi Manabu , Nakajima Kunio , Ohkubo Toshifumi
Published: July 2005

One of the most important parameters related to the near-field readout principle is aperture-to-media spacing (effective spacing). We proposed a near-field optical head with a protruding aperture that can reduce the effective spacing beyond the mechanical limit of the flying height and localize the near-field on the medium. Using nanostep lithography, we fabricated the protruding aperture, whose extension is 20 nm with 5 nm accuracy, so that the effective spacing is successfully reduced to 50 nm on a 3.2×3.6 mm flying head. We demonstrated signal readout with a 150 nm-long line-and-space pattern in chromium with the head. The flying height was estimated to be 75 nm, so that the effective spacing was 54 nm. The circumferential speed was 2.7 m/s and the signal frequency was 9.1 MHz. We also propose a promising structure for an optical head of higher density.
Effects of Solvent and Ambient Humidity on Nanodot Structures for Near-Field Optical Data Storage Using Self-Assembled Diblock Copolymer
Authors: Matsuyama Tsuyoshi , Kawata Yoshimasa
Published: July 2005

We present the formation of nanodot structures on a glass substrate by the self-assembly of a diblock copolymer. The structures can be used as nanopatterned media for near-field optical data storage with high data density. Improvements in the carrier-to-noise ratio (CNR) and in the uniformity of the recorded bit marks are expected with these structures. It is found that the structure of nanodots depends strongly on the ambient humidity during dripping and subsequent spin-casting and also on the solvent used. Nanodots of uniform size can be formed on a glass substrate with benzene, toluene, or toluene blended with acetone as a solvent when the ambient humidity is in the range of 60% to 70%. The size of the individual nanodots as well as the distance between two consecutive nanodots can be controlled, and the nanodots may be aligned like regular hexagonal close-packed structures by adjusting the volume ratio of acetone to toluene.
Analysis of Near-Field Readout Characteristics Using Approximate Vector Diffraction Calculation
Authors: Saito Kimihiro , Shinoda Masataka , Furuki Motohiro , Nakaoki Ariyoshi , Kobayashi Seiji
Published: July 2005

In a near-field optical readout system using a solid immersion lens (SIL), comparisons of the readout characteristics of different types of disc structure were made. We measured the frequency responses of the readout signals of a Si-etched disc, an injection molded polycarbonate disc and a phase-change disc. The calculation results obtained by an approximate vector diffraction method agreed well with the measured differences between the readout characteristics of the three discs.
High-Density Near-Field Optical Disc Recording
Authors: Shinoda Masataka , Saito Kimihiro , Ishimoto Tsutomu , Kondo Takao , Nakaoki Ariyoshi , Ide Naoki , Furuki Motohiro , Takeda Minoru , Akiyama Yuji , Shimouma Takashi , Yamamoto Masanobu
Published: July 2005

We developed a high-density near-field optical recording disc system using a solid immersion lens. The near-field optical pick-up consists of a solid immersion lens with a numerical aperture of 1.84. The laser wavelength for recording is 405 nm. In order to realize the near-field optical recording disc, we used a phase-change recording media and a molded polycarbonate substrate. A clear eye pattern of 112 GB capacity with 160 nm track pitch and 50 nm bit length was observed. The equivalent areal density is 80.6 Gbit/in2. The bottom bit error rate of 3 tracks-write was 4.5×10-5. The readout power margin and the recording power margin were ±30.4% and ±11.2%, respectively.
Improvement of Noise Characteristics in Super-Resolution Near-Field Structure Disc
Authors: Hwang Inoh , Kim Jooho , Bae Jaecheol , Kim Hyunki , Yoon Duseop , Park Insik , Shin Dongho
Published: July 2005

The research interest in super-resolution near-field structure (Super-RENS) technology is shifting from the signal intensity (carrier-to-noise ratio, CNR) to the signal uniformity (jitter or bER). To achieve uniform signal characteristics, it is important to reduce signal fluctuation in the super-RENS disc. In this study, we investigated the relationship between signal fluctuation and low-frequency noise (LFN), and analyzed the LFN increase in recording and readout processes. It was found that signal fluctuation had a close relationship with LFN. It was also found that certain recorded mark shapes, such a bubble shape, and high readout power increased the LFN during recording and readout processes of a super-RENS disc. Therefore, using non bubble-type recording material and low super-resolution readout material, we markedly improved the LFN of a super-RENS disc.
Towards Cover-Layer Incident Read-Out of a Dual-layer Disc with a NA=1.5 Solid Immersion Lens
Authors: Verschuren Coen A. , Zijp Ferry , Eerenbeemd Jack M. A. van den , Mark Martin B. van der , Lee Ju-Il
Published: July 2005

We present the status of our efforts to demonstrate the feasibility of recording on a cover-layer protected dual-layer optical disc with a blue laser and NA=1.45 objective lens that is based on a solid immersion lens (SIL). We discuss the potential data density and some practical and theoretical considerations for the light path, the objective lens and the media. In particular, we show a lens design and results of prototype manufacturing for a NA=1.45 lens that focuses on the data layer of an optical disc through a sub-wavelength air gap and a 3 µm spin coated cover-layer that protects the data on the disc.
Two-Photon Absorption Recording in Photochromic Diarylethenes Using Laser Diode for Three-Dimensional Optical Memory
Authors: Shiono Teruhiro , Itoh Tatsuo , Nishino Seiji
Published: July 2005

We have studied two-photon absorption (TPA) recording in photochromic diarylethenes for a three-dimensional (3D) optical memory, and demonstrated the TPA recording for the first time using a laser diode with a pulse width of 2 ns without a thermal influence. In comparison with the recording sensitivity by a femtosecond fiber laser, it was found that the peak power can be greatly reduced and the TPA sensitivity has squared characteristics depending on the pulse width range from 94 fs to 2 ns. Finite difference time domain (FDTD) analysis of optical intensity through refractive pits suggests that 3D recording in multilayered medium is more suitable, because optical aberrations induced by the lens effect of refractive pits are greatly reduced and the reflectance from a pit is improved, in comparison with that in a bulk medium.
Near Field Recording on First-Surface Write-Once Media with a NA=1.9 Solid Immersion Lens
Authors: Verschuren Coen A. , Zijp Ferry , Lee Ju-Il , Eerenbeemd Jack M. A. van den , Mark Martin B. van der , Urbach H. Paul
Published: July 2005

We present a single-wavelength near field recording set-up with a blue laser and a NA=1.9 solid immersion lens in a conventional focus and tracking actuator. The most important aspects to realize such a near field recording system are discussed, in particular, gap error signal normalization and correction of chromatic aberration of the objective lens. First recording results demonstrate that the set-up is fully operational.
Anneal-Less Domain Wall Displacement Detection of 27 Gbit/in2 Land/Groove Recording Using a Deep Groove Substrate and a Blue Laser
Authors: Hiroki Tomoyuki , Deguchi Kyosuke , Morita Kuniyuki , Yokoyama Ryuichi , Konishi Masahito , Miyaoka Yasuyuki , Koyama Osamu
Published: July 2005

We have studied an anneal-less domain wall displacement detection (DWDD) disk of a land/groove recording on a deep groove substrate using a numerical aperture (NA) 0.65 objective lens and a blue laser diode (LD). The substrates were prepared using a stamper formed by reactive ion etching (RIE) and O2 plasma treatment to realize both steep side-wall angles and smooth surfaces on the substrates. In designing the groove shape, we have clarified three key factors: the groove edge shape, the groove depth and the land width. These factors affected the magnetic film discontinuity at the groove edge and the recording power margin on the land. We have achieved a recording density of 27 Gbit/in2 by optimizing the groove shape.
Two-Dimensional Optical Storage Mastering: Adding a New Dimension to Liquid Immersion Mastering
Authors: Boamfa Marius I. , Neijzen Jaap H. M.
Published: July 2005

We present a novel-mastering concept of Two-dimensional structures using a single writing spot. We describe its implementation for the existing liquid immersion mastering set-up, from initial concept and feasibility analysis to mastered discs of up to 60 GB/layer data density.
Properties of Super-Resolution Near-Field Structure with Platinum-Oxide Layer in Blu-ray Disc System
Authors: Kikukawa Takashi , Fukuzawa Narutoshi , Kobayashi Tatsuhiro
Published: July 2005

The super-resolution near-field structure with a platinum-oxide layer was applied to the Blu-ray Disc system. The carrier-to-noise ratios of 50.1, 46.2, and 39.2 dB were obtained at the mark lengths of 75, 50, and 37.5 nm, respectively, which are smaller than the resolution limit of 119 nm of the optics. Mark position recording with a mark length of 50 nm was also attempted, and we succeeded in retrieving recorded patterns correctly without loss of the signal.
In-Sb Phase-Change Material for 16× Rewritable Digital Versatile Disk
Authors: Suzuki Eiko , Miura Hiroshi , Harigaya Makoto , Ito Kazunori , Iwata Noriyuki , Watada Atsuyuki
Published: July 2005

We investigated Sb-based In-Sb as a material for high-speed recording that is capable of maintaining a highly stable amorphous phase. The crystalline phase of In-Sb is unstable at approximately its eutectic composition. After an aging test, InSb was segregated, and its reflectivity was reduced. For an Sb-rich In-Sb, we confirmed that its crystalline phase is stable and its crystallization speed is high. We demonstrated the feasibility of 16× digital versatile disk (DVD) recording using 2T-period multiple-pulse strategy.
Phase Change Super Resolution near Field Structure ROM
Authors: Kim Hyunki , Hwang Inoh , Kim Jooho , Park Changmin , Ro Myongdo , Lee Jinkyung , Jung Moonil , Park Insik
Published: July 2005

We confirmed a super resolution phenomenon and a typical super resolution near field structure threshold phenomenon in a read only memory (ROM)-type sample disk. We found that this super resolution phenomenon originates from a phase-change layer and is closely related to the thermal properties of the super resolution layer. We also improved the readout stability using a co-sputtered layer with phase change (GST) and dielectric materials (ZnS-SiO2).
Signal Characteristics of Super-Resolution Near-Field Structure Disks with 100 GB Capacity
Authors: Kim Jooho , Hwang Inoh , Kim Hyunki , Park Insik , Tominaga Junji
Published: July 2005

We report the basic characteristics of super resolution near-field structure (Super-RENS) media at a blue laser optical system (laser wavelength 405 nm, numerical aperture 0.85). Using a novel write once read many (WORM) structure for a blue laser system, we obtained a carrier-to-noise ratio (CNR) above 33 dB from the signal of the 37.5 nm mark length, which is equivalent to a 100 GB capacity with a 0.32 micrometer track pitch, and an eye pattern for 50 GB (2T: 75 nm) capacity using a patterned signal. Using a novel super-resolution material (tellurium, Te) with low super-resolution readout power, we also improved the read stability.
Investigation on Super-Resolution Near-Field Blu-Ray-Type Phase-Change Optical Disk with Sb2Te3 Mask Layer
Authors: Shi Luping , Chong Tong Chong , Tan Pik Kee , Li Jianming , Hu Xiang , Miao Xiangshui , Wang Qingfang
Published: July 2005

Super-resolution near-field phase-change Blu-ray-type optical disks with a mask layer of Sb2Te3 were studied theoretically and experimentally with a laser wavelength of 405 nm and a numerical aperture (NA) of 0.85. The modulation transfer function (MTF) was calculated and the thermal performance was simulated by the finite element method. Super-resolution near-field phase-change Blu-ray-type optical disks with different structures were fabricated and measured. It was shown that the thermal shield layer was helpful in reducing recorded mark size and improving readout stability. Recorded marks as small as 16 nm were observed. The relevant mechanism was discussed.
Energy-Gap-Induced Super-Resolution (EG-SR) Optical Disc Using ZnO Interference Film
Authors: Mori Go , Yamamoto Masaki , Tajima Hideharu , Takamori Nobuyuki , Takahashi Akira
Published: July 2005

We have developed a super-resolution read-only memory (ROM) disc with a high readout stability using a zinc oxide (ZnO) thin film. Applying the reversible and repeatable change in the optical constants of ZnO induced by heat, we can successfully confirm super-resolution effects that can read out a small mark beyond the optical diffraction limit. By realizing this characteristic in a ROM disc, we obtained a linear bit density twofold higher than that of a conventional disc in the blue-laser optical system. To clarify the origin of ZnO super resolution, we performed two types of test: a test to compare ZnO super-resolution characteristics using blue- and red-laser optical systems, and a test to determine the relationship between the absorption edges of semiconductor films with various energy band gaps and readout laser wavelength.
High-Deposition-Rate Dielectric Thin Film for Phase Change Optical Disc
Authors: Kariyada Eiji , Ohkubo Shuichi , Tanabe Hideki , Ide Tatsunori
Published: July 2005

To improve the productivity of high density digital versatile disk-rewritable media (HD DVD-rewritable media), a silicon-nickel oxynitride (SiNiON) film that can be sputtered with a SiNi target in an atmosphere of mixed argon, oxygen, and nitrogen gases has been developed. The SiNiON film had a deposition rate almost the same as that of the ZnS-SiO2 film widely used in phase change recording media, and its refractive index was sufficiently low, that is, 1.54. Its structure was a mixed matrix of Si, Ni, O, and N, rather than a mixture of SiO2 and Si3N4 clusters. HD DVD-rewritable media using the SiNiON film showed almost the same excellent read/write characteristics as those of the media using the SiO2 film.
Write-Once Disc with BiFeO Thin Films for Multilevel Optical Recording
Authors: Sasa Noboru , Hayashi Yoshitaka , Fujii Toshishige , Watada Atsuyuki , Komoda Hirotaka
Published: July 2005

We optimized BiFeO thin film for use in multilevel optical recording. Due to minimal intersymbol interference (ISI), we obtained a 2.57% sigma-to-dynamic range (SDR) at a recording capacity of 25 GB. We confirmed that our write-once disc achieved a recording capacity of 25 GB using a laser diode with a 405-nm wavelength and a 0.65-numerical aperture objective lens.
Optical Read-Only-Memory Card System Based on the Talbot Effect
Authors: Hoog Thomas de , Kastelijn Aukje , Hendriks Rob , Verberne René , Busch Christopher
Published: July 2005

We present our progress in developing an optical storage system for portable devices, consisting of a removable read-only-memory (ROM) card and a robust reader. The bit patterns stored on the card medium are read out using an array of probes that are generated by means of the Talbot effect. The data are recovered in a parallel fashion by detection with a standard pixelated image sensor. To attain a large data capacity, a multiplexing scheme has been developed: from a large number of different data pages, individual pages can be selected by scanning the probe array over the medium in x and y direction. In order to position the probes accurately it is required to have accurate position information. A method has been devised to generate servo signals by making use of the moiré interference effect. A compact demonstrator was built that demonstrates feasibility of this position control method.
Inkjet Printing of Polymeric Field-Effect Transistors and Its Applications
Authors: Kawase Takeo , Moriya Soichi , Newsome Christopher J. , Shimoda Tatsuya
Published: July 2005

In this paper, the inkjet printing of polymeric field-effect transistors (FETs), inverters and active-matrix backplanes will be reviewed. Inkjet printing, which is characterized as an additive and noncontact patterning method, is an efficient method of fabricating organic devices. All-solution-processed FETs were prepared in ambient air by inkjet-printing the liquid sources of a conductor or a semiconductor, and exhibited a high on–off current ratio of more than 105. This stability is attributed to the high ionization potential (5.4 eV) of the fluorene–bithiophene copolymer used in our work. Channel lengths of less than 20 µm were also achieved by depositing an aqueous dispersion of a conducting polymer along a prepatterned strip that exhibited a hydrophobic surface, thus defining the transistor channel. Partially-solution-processed FETs were also obtained by combining conventional vacuum processes and the inkjet printing of solutions. This approach is considered to be efficient for producing actual devices, and flexible active-matrix backplanes were fabricated using this structure. A flexible electrophoretic display has been achieved by laminating an inkjet-printed active-matrix backplane with an electrophoretic device.
Injection and Transport of High Current Density over 1000 A/cm2 in Organic Light Emitting Diodes under Pulse Excitation
Authors: Nakanotani Hajime , Oyamada Takahito , Kawamura Yuichiro , Sasabe Hiroyuki , Adachi Chihaya
Published: July 2005

We succeeded in injecting and transporting a maximum high current density of J=1163 A/cm2 in organic light-emitting diodes using short-pulse excitation combined with a highly thermally conductive silicon substrate (thermal conductivity: 148 W m-1 K-1) and a small cathode configuration (cathode radius r=50 µm). A maximum current density almost 20 times higher than that associated with direct current (DC) operation was observed by driving an OLED with a short pulse voltage. With short-pulse excitation, the decrease in external quantum efficiency (ηext) obeyed a typical singlet–singlet exciton annihilation model well, indicating that the generation of Joule heat in OLEDs can be suppressed under pulse operation.
Active Matrix Driving Organic Light-Emitting Diode Panel Using Organic Thin-Film Transistors
Authors: Ohta Satoru , Chuman Takashi , Miyaguchi Satoshi , Satoh Hideo , Tanabe Takahisa , Okuda Yoshiyuki , Tsuchida Masami
Published: July 2005

We developed an active matrix driving organic light-emitting diode (OLED) panel on a glass substrate using two organic thin-film transistors (OTFTs) per pixel, a switching OTFT and a driving OTFT. The OTFTs are bottom contact structures with the high-dielectric constant gate insulator tantalum oxide (Ta2O5, relative dielectric constant of 23) produced by anodization in ammonium adipate solution and with pentacene as the active layer. The W/L (where W and L are the OTFTs channel width and length, respectively) was 400 µm/10 µm for the switching OTFTs and 680 µm/10 µm for the driving OTFTs. The characteristics of the OTFTs were improved by treating the Ta2O5 surface with hexamethyldisilazane (HMDS), so that the field-effect mobility was 2.0×10-1 cm2 V-1 s-1 and the current on/off ratio was 105. A green phosphorescent dopant, tris(2-phenylpyridine)iridium [Ir(ppy)3], was used for the OLED layer. The panel had 8×8 pixels and the aperture ratio was 27%. We confirmed a 16-gray-scale representation and a luminance of 400 cd/m2.
Charge Carrier Transport in Neat Thin Films of Phosphorescent Iridium Complexes
Authors: Matsusue Noriyuki , Suzuki Yuichiro , Naito Hiroyoshi
Published: July 2005

The charge carrier transport properties of neat thin films of red-, green- and blue-phosphorescence Ir complexes have been investigated in terms of time-of-flight transient photocurrent measurement. Bis(2-(2'-benzo[4,5-a]thienyl)pyridinato-N,C
3')iridium(acetylacetonate) (btp2Ir(acac)) (red-phosphorescence emitter) and iridium(III) bis[(4,6-di-fluorophenyl)-pyridinato-N,C
2']picolinate (FIrpic) (blue-phosphorescence emitter) thin films exhibit bipolar charge transport. In contrast, the electron and hole transit signals of fac-tris(2-phenylpyridine)iridium(III) (Ir(ppy)3) (green-phosphorescence emitter) thin films are unobservable. The charge carrier transport properties of thin films of an Ir-complex-doped 4,4'-N,N'-dicarbazole-biphenyl (CBP) and the appropriateness of FIrpic as a triplet-exciton and hole blocking layer are shown.
Photoelectron Spectroscopy of the Contact between the Cathode and the Active Layers in Plastic Solar Cells: The Role of LiF
Authors: Jönsson S. K. M. , Carlegrim E. , Zhang F. , Salaneck W. R. , Fahlman M.
Published: July 2005

The surfaces and electrode interfaces of a polymer blend used in prototype solar cells have been characterized with photoelectron spectroscopy. The polymer blend in question is a 1:4 mixture of APFO-3:PCBM. Based on surface analysis of the pristine film we can conclude that the surface of the blend is a 1:1 mixture of APFO-3 and PCBM. The electrode systems studied are the widely used Al and Al/LiF contacts. LiF prevents formation at the Al/organic interface of Al-organic complexes that destroy the π-conjugation. In addition to this, there are two other beneficial, thickness dependent, effects. Decomposition of LiF occurs for thin enough layers in which the LiF species are in contact with both the organic film and the Al atoms, which creates a low workfunction contact. For thicker (multi)layers, the dipole formed at the LiF/organic interface is retained as no decomposition of the LiF occurs upon Al deposition.
Study of Molecular Structures and Properties of Europium(III) Complexes with Phosphine Oxides by NMR Analysis
Authors: Iwanaga Hiroki , Amano Akio , Oguchi Masayuki
Published: July 2005

The 31P-NMR spectra of europium complexes with β-diketones and phosphine oxides in CDCl3, DMSO-d
6, toluene-d
8 with dissolved fluorinated polymers, and fluorinated solvent were investigated as well as the temperature dependence of these spectra. When a mixture of europium complex 1 and 1.0 molar equivalent of trioctylphosphine oxide and triphenylphosphine oxide was dissolved in a fluorinated solvent, europium complex 2 with two types of phosphine oxides was formed at room temperature. In CDCl3 and toluene-d
8 solutions, however, this complex was identified only at low temperatures. This difference is thought to be due to the differences in the speed of ligand exchanges. In DMSO-d
6 solution, no signal corresponding to the europium complex with phosphine oxides was observed. This implies that the major portion of phosphine oxides is not coordinated with europium ions in DMSO-d
6 solution. The fluorescence intensity of each europium complex in a solvent was correlated to the solvent and the 31P-NMR spectrum. It was found that the fluorescence intensity was the highest in the fluorinated solvent.
Electrode Effects of Organic Thin-Film Transistor with Top and Bottom Contact Configuration
Authors: Yoshida Manabu , Uemura Sei , Hoshino Satoshi , Takada Noriyuki , Kodzasa Takehito , Kamata Toshihide
Published: July 2005

Organic semiconductors have several unique properties that are different from those of inorganic semiconductors. Therefore, in order to develop an organic transistor, it is important to investigate structural factors of a device that govern the operation mechanism. Recently, we have designed a new device structure of an organic field-effect transistor (FET) with a diagonal configuration of source and drain electrodes, named as the top and bottom contact (TBC) configuration. In this device structure, the source and drain electrodes are prepared individually; therefore, it is convenient to independently study electrode effects on FET properties. In this study, we have prepared a pentacene TBC-FET, and studied electric field effects on FET properties in relation to the electrode configuration. By controlling several factors for the bottom electrode, we have observed marked changes in FET properties. It was revealed that the observed phenomena were mainly due to a difference in carrier injection efficiency.
Liquid Crystal Display Cells Fabricated on Plastic Substrate Driven by Low-Voltage Organic Thin-Film Transistor with Improved Gate Insulator and Passivation Layer
Authors: Fujisaki Yoshihide , Sato Hiroto , Fujikake Hideo , Inoue Youji , Tokito Shizuo , Kurita Taiichiro
Published: July 2005

Organic thin-film transistor (OTFT)-driven 5×5 polymer-dispersed liquid crystal (PDLC) display cells on a flexible plastic substrate have been developed. It is necessary to increase the maximum usable gate voltage of OTFT to obtain a high contrast ratio. We propose a stacked gate insulator that consists of polyvinylphenol and anodized Ta2O5 for decreasing the gate leakage current and increase the maximum voltage. The OTFT with the insulator showed a field-effect mobility of 0.4 cm2/(V s), a current on/off ratio of 105, a low threshold voltage of 1.1 V, and a subthreshold slope of 0.2 V/decade. Leakage current was successively decreased up to a gate voltage of 15 V, maintaining a low-voltage operation of OTFT. Double passivation layers using polyvinylalcohol and photosensitive acrylic material are also proposed to prevent the degradation of OTFT by liquid crystal. The bending characteristics of OTFT on plastic substrates were also measured for various radiuses of curvature. The OTFT can operate at a radius of curvature exceeding 20 mm. On the fabricated display cells, we confirmed a good display operation with a contrast ratio of 10:1 with a low driving voltage of 12–13 V.
Interpretation of Dominant Impurities in Cu Films by Secondary Ion Mass Spectrometry and Glow Discharge Mass Spectrometry
Authors: Lim Jae-Won , Bae Joon Woo , Mimura Kouji , Isshiki Minoru
Published: July 2005

Cu films were deposited on Si (100) substrates at substrate bias voltages of 0 V and -50 V by non-mass separated ion beam deposition. SIMS and GDMS were used to determine the impurity concentrations of a Cu target and Cu films. According to the quantitative GDMS results, many unknown peaks observed in the SIMS spectra of the Cu films were assigned to cluster states such as C
x
H
x
, O
x
H
x
, and C
x
O
x
H
x
. Moreover, it was found that the dominant impurities in the films were H, C, N, and O elements.
Characterisation of Organic Field-Effect Transistor by Scanning Raman Spectroscopy
Authors: Leung Shee-Ann , Tojo Takayuki , Murata Hideyuki
Published: July 2005

Organic molecular semiconductors, such as pentacene (C22H14), is of great interest for potential application in thin-film organic field-effect transistors (OFETs). Novel scanning Raman microscopy was applied to the analysis of OFETs. Effective channel sizes in top-contact and bottom-contact OFETs were determined from scanning Raman spectra. The bottom-contact OFET showed a sharp change in Raman intensity at the gold/pentacene interface over a short distance while the top-contact OFET showed a gradual change in Raman intensity over a wide region. In the case of a gold electrode deposited on pentacene, the real channel size could be as small as half of the intended size. This resulted in the decrease in effective channel size and thus in the overestimation of the calculated mobility. The small channel length could be attributed to the presence of gold (composite) inside the channel in the top-contact OFET.
Fabrication of Highly Oriented Rubrene Thin Films by the Use of Atomically Finished Substrate and Pentacene Buffer Layer
Authors: Haemori Masamitsu , Yamaguchi Jun , Yaginuma Seiichiro , Itaka Kenji , Koinuma Hideomi
Published: July 2005

We report the remarkable effects of physical and chemical treatments of substrate surface on the physical vapor deposition of rubrene thin films. Highly c-axis oriented rubrene thin films were fabricated by combinatorial molecular beam epitaxy on atomically flat α-Al2O3 (0001) substrates, the surface of which was partially modified with pentacene buffer film. Rubrene thin films grown at room temperature on a sapphire substrate without pentacene buffer layer did not exhibit any X-ray diffraction pattern, whereas films deposited on a pentacene buffer layer exhibited peaks of c-axis orientation. Atomic force microscope images of the crystalline films show the steps of 1.3 nm height which correspond to the half c-axis length of the rubrene crystal. Preliminary, p-type operation was observed in bottom-gate field effect transistors using this rubrene film deposited on a pentacene buffer.
Photoconductive Properties of Organic Films Based on Porphine Complex Evaluated with Image Pickup Tubes
Authors: Aihara Satoshi , Miyakawa Kazunori , Ohkawa Yuji , Matsubara Tomoki , Takahata Tamotsu , Suzuki Shiro , Kubota Misao , Tanioka Kenkichi , Kamata Norihiko , Terunuma Daiyo
Published: July 2005

We have fabricated two types of organic photoconductive films; a layered structure of tetra(4-methoxyphenyl) porphine cobalt complex (Co–TPP) and bathocuproine (BCP) (target A), and another of Co–TPP, tris-8-hydroxyquinoline aluminum (Alq3) and BCP (target B). The photoconductive properties of each film have been measured using image pickup tubes. The dark current was drastically reduced in target B compared with that in target A at the same applied electric field. The external quantum efficiency reached 20% in target B, which is twenty times higher than that in target A. Image pickup of a test chart from target B at standard TV operation was also demonstrated. High resolution and excellent tone sufficient for television use has been obtained.
Enhancement of Laser Emission Intensity in Dye-Doped Cholesteric Liquid Crystals with Single-Output Window
Authors: Amemiya Kazuhiro , Nagata Takaaki , Song Myoung Hoon , Takanishi Yoichi , Ishikawa Ken , Nishimura Suzushi , Toyooka Takehiro , Takezoe Hideo
Published: July 2005

Lasing from a dye-doped cholesteric liquid crystal (CLC) has been studied in cells with a single-output window. One of the glass substrates of the cells was coated with a polymeric CLC film having a high reflectance for laser emission or an aluminum layer for reflection of both pump and lasing beams. Laser emission toward one direction was observed with enhanced intensity.
Effects of Sputtering Parameters on the Formation of Single-Oriented (002) Ti Film on Si
Authors: Mireba Kazuhiro , Shinkai Satoko , Yanagisawa Hideto , Sasaki Katsutaka , Abe Yoshio
Published: July 2005

We investigated the preparation conditions of a single-oriented (002) Ti film on a Si substrate, as functions of sputtering parameters, using an ultrahigh-vacuum dc magnetron sputtering system. We found that a single-oriented (002) Ti film with an excellent electrical property grew on (001) and (111) Si under an optimum sputtering power of 100 W and an optimum substrate temperature of 150°C. It was revealed that this is due to the formation of an amorphous silicide interlayer at the Si interface as a buffer layer for relaxing the misfit.
An in-situ Fabrication and Characterization System Developed for High Performance Organic Semiconductor Devices
Authors: Yamaguchi Jun , Yaginuma Seiichiro , Haemori Masamitsu , Itaka Kenji , Koinuma Hideomi
Published: July 2005

We have designed and set up a fabrication and characterization system for organic devices which enables us to assemble all components of devices and to characterize the device properties without breaking the vacuum. Using this system, top and bottom contact C60 field effect transistors (FETs) were fabricated and their performance was characterized. The top contact FET exhibited a mobility as high as 1.4 cm2/(V·s), which was higher than the bottom contact FET.
Doping Effect of Tetrathianaphthacene Molecule in Organic Semiconductors on Their Interfacial Electronic Structures Studied by UV Photoemission Spectroscopy
Authors: Tanaka Senku , Kanai Kaname , Kawabe Eiji , Iwahashi Takashi , Nishi Toshio , Ouchi Yukio , Seki Kazuhiko
Published: July 2005

The n-type doping ability of the electron-donating organic molecule tetrathianaphthacene (TTN) was examined by ultraviolet photoemission spectroscopy (UPS) for two kinds of matrix organic semiconductors, hexadecafluorophthalocyaninatozinc (F16ZnPc) and tris(8-hydroxyquinoline)aluminum (Alq3). The observed dependence of the UPS spectra suggests that TTN acts as a good donor in F16ZnPc, while the effect was not so significant for Alq3. These results and the consideration of the energy parameters of these molecules indicate that a close match between the highest occupied molecular orbital of the dopant and the lowest unoccupied molecular orbital of the matrix is important for efficient n-type doping.
Hybrid Density Functional Theory (DFT) Study on Electronic States of Halogen-Substituted Organic–Inorganic Hybrid Compounds: Al-NTCDA
Authors: Tachikawa Hiroto , Kawabata Hiroshi
Published: July 2005

Hybrid density functional theory (DFT) calculations have been carried out for high-performance molecular devices, complexes of naphthalene tetracarboxylic dianhydride (NTCDA) and halogen-substituted NTCDA with aluminum (denoted by Al4(X)4NTCDA, where X denotes H, F, Cl or Br). The four hydrogen atom of NTCDA were substituted with X atoms. It was found that the electronic state of the complex in the ground state is composed of a charge-transfer state expressed by (Al4)δ+((X)4NTCDA)δ-. Also, it was predicted that the binding energy of the Al atom was enhanced by the halogen substitution, indicating that the complex of (X)4NTCDA (X = halogen atoms) is more stable in terms of energy than that of pure NTCDA (X=H). The large binding energy results in the high material stability in atmosphere. By photoirradiation of the complex, the interaction between Al and NTCDA was changed from ionic to covalent. This electronic excitation was assigned to the back donation of an electron from NTCDA to Al, and it was predicted theoretically that the absorption spectrum appears as a charge-transfer (CT) band in the near infrared region. The effects of halogen-substitution on the electronic states of NTCDA are discussed on the basis of theoretical results.
Possibility of Prompt 238U Activity Concentration Determination by Gamma-Ray Spectroscopy
Authors: Bikit Istvan , Mrdja Dusan , Todorovic Natasa , Varga Ester , Forkapic Sofija , Veskovic Miroslav , Slivka Jaroslav , Conkic Ljiljana
Published: July 2005

Recent results on 238U/234Th disequilibria in marine studies seriously challenge the possibility of the prompt gamma-ray spectroscopic determination of 238U activity concentration in environmental samples from the gamma-ray lines of the first daughter of 238U, the nucleus 234Th. In this paper we present the results of the gamma-ray spectrometric measurements of 234Th, which were repeated using the same soil and sediment samples at least one year after the first measurement. We did not find any indication of Th activity variation due to 238U/234Th disequilibria. All the obtained results prove that the 238U and depleted uranium determination in soil and sediment samples using 234Th gamma-ray lines introduces at most a systematic error of 3% into the obtained results.
Workfunction Tuning Using Various Impurities for Fully Silicided NiSi Gate
Authors: Sano Kousuke , Hino Masaki , Ooishi Norihiro , Shibahara Kentaro
Published: July 2005

Workfunction tuning by the implantation of various impurities and by changing silicidation conditions was investigated for a fully silicided NiSi gate. In the case of Sb implantation, it was found that the NiSi gate workfunction was decreased by 0.34 eV from 4.60 eV, for an undoped NiSi gate, to 4.26 eV due to the lowering of the silicidation temperature. Ge, which has not been used for workfunction tuning before, induced a decrease in NiSi gate workfunction in the same way. In the case of In implantation, a decrease in accumulation capacitance in capacitance–voltage (C–V) characteristics was observed. The origin of this problem was found to be void formation at the oxide interface. The voids were also found in NiSi predoped with Sb and silicided at 450°C or lower.
Behavior of Metal-Induced Negative Oxide Charges on the Surface of N-type Silicon Wafers Using Frequency-Dependent AC Surface Photovoltage Measurements
Authors: Shimizu Hirofumi , Shin Ryuhei , Ikeda Masanori
Published: July 2005

The metal-induced negative charge on the surface of n-type silicon (Si) wafers, previously reported in the atomic bridging model as (AlOSi)-and (FeOSi)-networks, was investigated using AC surface photovoltage (SPV) as a function of the frequency (f) of a chopped photon beam, with the aid of an AC SPV instrument developed in-house. A frequency-dependent AC SPV in Al-contaminated wafers was observed immediately after the rinsing. In the early stages of exposure to air at room temperature after rinsing, the induced AC SPV at frequencies of less than approximately 100 Hz was flat with frequency. This indicated that majority carrier conduction was the dominant mechanism, suggesting that the surface was depleted and/or weakly inverted. With the passage of time, the AC SPV in the lower frequency region increased, yielding an AC SPV vs frequency relationship approaching 1/f. This demonstrated that the Al-induced negative charge [(AlOSi)-] increased and finally became limited by the depletion layer capacitance (strongly inverted state). The frequency-dependent AC SPV caused by Fe-induced negative charge [(FeOSi)-] was identified as being dependent on Fe concentration on the Si surface. The higher the Fe concentration, the more strongly inverted the Si surface became. The metal-induced oxide charge could be observed, together with other oxide charges such as fixed oxide charge.
Deep-Level Transient Spectroscopy Studies of Filling Behavior of a Hydrogen-Related Metastable Defect in n-Type Silicon
Authors: Tokuda Yutaka , Nakamura Wakana , Nakashima Koji , Iwata Hiroyuki
Published: July 2005

Deep-level transient spectroscopy (DLTS) has been used to study the filling behavior of a hydrogen-related metastable defect labeled EM1 (E
c-0.29 eV) which is observed in oxygen-rich n-type silicon implanted with hydrogen ions at 88 K and subsequently heated to room temperature. The EM1 DLTS peak height decreases exponentially with filling pulse duration time in the range studied (1 ms to 50 s) and reaches saturation with a nonzero value. This result contradicts the filling behavior due to the carrier capture process at traps. The decreasing exponential dependence of the EM1 DLTS peak height on filling time is reproduced when the measurement is restricted to temperatures up to 175 K. This observation is ascribed to the transformation of EM1 occurring during DLTS measurements, which is different from its metastable reaction reported previously. EM1, the stable state under reverse bias, is transformed into two stable states under zero bias with different activation energies.
Acceleration of Cu Surface Precipitation from Bulk by Adsorbed Organic Molecules
Authors: Ohkubo Yasuo , Matsumoto Kei , Nagai Kiyoshi
Published: July 2005

Cu has the highest solubility and diffusivity in silicon. Hence Cu in the bulk of silicon wafers can easily diffuse to the wafer surface even at room temperature, and is in danger of deteriorating the devices. It is reported that such a Cu out diffusion phenomenon is affected by the wafer surface condition. It is also known that adsorbed organic molecules on the wafer surface can be a factor changing the surface condition. We investigated the correlation between adsorbed organic molecules on the wafer surface and Cu out diffusion. We found that the organic molecules adsorbed on the wafer lower the surface electrostatic potential, and accelerate Cu out diffusion. We also found that Cu precipitates caused by the out diffusion phenomenon lower the surface potential, and then promote the out diffusion of Cu onto the wafer surface.
Modeling of Degradation Effects on the High Frequency Noise of Metal–Oxide–Semiconductor Field-Effect Transistors
Authors: Teng Heng-Fa , Jang S.-L. , Juang M.-H.
Published: July 2005

This paper proposes a hot-carrier stressed high-frequency noise model for metal–oxide–semiconductor field-effect transistors (MOSFETs). We first use the analytical method to develop a new fresh high-frequency noise model for MOSFETs, this model incorporates the effects of gate resistance, gate-induced current noise and non-local channel carrier heating, it can be used to calculate the minimum noise figure F
min, optimized source admittance Y
opt, and equivalent noise resistance R
n and admittance G
i. Secondly, we develop a new post-stress high-frequency noise model for MOSFETs, within this model the effects of hot-carrier stress induced interface states on the high-frequency noise performance can be evaluated. This model provides insightful device physics about the evolution of spatial noise sources within the channel versus stress time. The modeled results are in agreement with the experimental data of nMOSFETs with 0.25, 0.3 and 0.8-µm channel lengths.
Analysis of Sb–As Surface Exchange Reaction in Molecular Beam Epitaxy of GaSb/GaAs Quantum Wells
Authors: Nakai Takanori , Yamaguchi Koichi
Published: July 2005

GaSb/GaAs quantum wells (QWs) were grown on the GaAs(001) substrate by molecular beam epitaxy (MBE), and their QW structures were analyzed using a kinetic model that takes into account the surface exchange reaction of As and Sb atoms during GaAs cap growth. The photoluminescence peak energy of GaSb/GaAs QWs depended on the growth temperature of the GaAs cap layer, and this dependence was explained by a broadening of the QW structure, due to the As–Sb exchange reaction. The calculated optical transition energy of the analyzed QW structure almost agreed with experimental results after adjusting the bowing parameter (b
v) for the valence band edge in GaAs1-x
Sb
x
alloys and the activation energy of the Sb–As surface exchange reaction (E
Sb, E
As). As the result, b
v=0.67±0.06, E
Sb=1.68±0.01 eV and E
As=1.80±0.01 eV were obtained.
Structural Analysis of Hydrogenated a-Si Films by Reverse Monte Carlo Simulation
Authors: Tabuchi Norikazu , Kawahara Toshio , Arai Takashi , Morimoto Jun , Matsumura Hideki
Published: July 2005

Reverse Monte Carlo (RMC) simulation is one of the most useful tools for determining the three-dimensional (3D) atomic structure of non hydrogenated amorphous silicon (a-Si) or a-Si containing only a small atomic percentage of hydrogen. In this paper, the applicability of RMC simulation to conventional hydrogenated a-Si (a-Si:H) with a hydrogen content of 10% or more, which is prepared by plasma enhanced chemical vapor deposition (PECVD), is extensively studied. The coordination constraint method, in which coordination numbers are specified in advance as boundary conditions of the RMC simulation, is introduced using information on the concentration of Si–H and Si–H2 bonds from infrared (IR) absorption measurements. The consistency of the RMC structural model with other experimental results obtained by Raman spectroscopy and small angle X-ray scattering is checked to confirm the validity of the RMC analysis itself. It is found that the RMC simulation with coordination constraints can be adapted even for the PECVD a-Si:H containing 10% hydrogen, and that the method is applicable to know the 3D atomic structure of various types of a-Si film.