Conference Abstracts

Group A: Basic Research / Support Research

Session 7: Nanofabrication and Molecular Electronics

Session 10: Ultrasonic Micro-Spectroscopy and Semiconductor Spintronics

Session 13: Plasma science, Optical Devices and Surface Science I

Session 16: Plasma science, Optical Devices and Surface Science II

Session 7: Nanofabrication and Molecular Electronics

7-1 Title Invited talk: Formation of Meso- and Micro-porous Silicon Multilayers for Sensing Chemical Vapors
Author(s) Mohamed Shaker Salem
Abstract A porous silicon multilayer prepared by sinusoidally modulating current density during anodization of silicon produces a kind of 1-D photonic structure known as porous silicon rugate filter (PSRF). When this structure is exposed to condensable vapor, capillary condensation of vapor takes place in the nanometer-sized pores. This produces a remarkable red shift in the spectrum. PSRF is usually fabricated from a heavily doped substrate (p+) because the resulting multilayer is mechanically less fragile than the multilayer >prepared from a lightly doped substrate (p). The latter substrate generates a microporous structure which is important to make condensation at low vapor concentrations. In this study, we compare the sensing performance of oxidized p-PSRF and p+-PSRF to chemical vapor.

7-2 Title Non-contact scanning nonlinear dielectric microscopy with quartz tuning fork force gradient sensor
Author(s) Mirai Katoh and Yasuo Cho
Abstract Scanning nonlinear dielectric microscopy is utilized to for an analysis of electronic devices on a nanometer or atomic scale resolution. But diffuse equipments have some problems; the wear of probe edge or the surface destruction of specimen were caused by scan on contact of SNDM probe and specimen. We applied non-contact atomic force microscopy with a height feedback control system by a quartz tuning fork to scanning nonlinear dielectric microscopy.

7-3 Title Non-label DNA sensing by porous Si in conjugated with infrared microspectroscopy
Author(s) Ryotaro Yamaguchi, Ken-ichi Ishibashi, Ko-ichiro Miyamoto, Ayumi Hirano, Yasuo Kimura and Michio Niwano
Abstract We propose a porous silicon (por-Si) based DNA chip using infrared (IR) microspectroscopy. Por-Si has been demonstrated to be a sensitive platform because of its large internal surface area. In our method, we are able to detect DNA hybridization through analysis of IR spectral profiles of DNA bases, thus eliminating the need for DNA labeling. In addition, we can distinguish DNA molecules from other foreign substances from the IR spectra. In this study, we have investigated the feasibility of our method by measuring the IR absorption spectra of DNA molecules on por-Si surfaces.

7-4 Title Application of anodic titanium nanotubes to dye sensitized solar cells
Author(s) Kenichi ishibashi
Abstract We have fabricated titanium oxide (TiO2) nanotubes of about 10 µm in length through anodization of metal titanium (Ti) in new electrolyte for 5 minutes, which are 1/100 times shorter than in previous reports. The unique geometry of TiO2 nanotubes can improve the characteristics of DSSCs and we have applied the anodic TiO2 nanotubes to the negative electrode of DSSC and characterized its electrical property. Our results indicate that anodization process of metal Ti is a promising fabrication method of TiO2 nanotubes for the negative electrode of DSSCs.

7-5 Title Observation of initial oxidation process on Si(001)-2~1 by scanning tunneling microscopy
Author(s) Hideaki Togashi, Hidehito Asaoka, Tatsuya Yamazaki and Maki Suemitsu
Abstract With the shrinkage of the CMOS devices, the gate-oxide thickness is now in the range of 1.5-2.0 nm. In this situation, clarification of the mechanism of the initial oxidation is of crucial importance because it may have great impacts on the quality of the resultant oxide film. We report our scanning-tunneling-microscopy (STM) observation on the initial oxidation of Si(001)-2x1 surface in its island-growth (T, P) regime. It was found that the oxide islands initially grow one-dimensionally until the number of the oxygen atoms within an island becomes four, above which the islands are prone to be converted into two-dimensional ones.

7-6 Title Trap-Elimination and Injection-Switching at Organic Field Effect Transistor
Author(s) Satoshi Ogawa, Yasuo Kimura, Hisao Ishii and Michio Niwano
Abstract Recently, it was proposed in the literature that the electron-trap on a hydroxyl-containing dielectric interface of an organic field effect transistor (OFET) hinders its n-type operation. We fabricated pentacene and fullerene OFETs with a hydroxyl-free insulating material, a long-chain alkane, i.e, tetratetracontate (TTC), C44H90 layer coated on the SiO2 dielectric layer. The displacement current measurements clearly demonstrated that the electron trap of the SiO2 surface is suppressed by the TTC layer. For a pentacene FET with an Al electrode and SiO2 dielectric layer, a p-type operation was observed, while the operation mode was switched to the n-type by theinsertion of TTC on the SiO2 interface.

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Session 10: Ultrasonic Micro-Spectroscopy and Semiconductor Spintronics

10-1 Title Plasma-assisted molecular beam epitaxy growth of ZnMgO layers on O-polar Zn substrate
Author(s) Mohamed Belmoubarik, Ohtani Keita and Ohno Hideo
Abstract ZnMgO layers are grown on (000-1)-oriented ZnO (O-polar) substrates by plasma-assisted molecular beam epitaxy. X-ray diffraction (XRD) measurements of grown ZnMgO layers with various Mg contents are carried out to evaluate the crystallinity and the change in lattice parameters of those layers. X-ray photoelectron spectroscopy (XPS) indicates that the Mg content maximum of ZnMgO layers grown at the substrate temperature of 450C with single-phase (0002)-oriented wurtzite structure is approximately 45 %. Reciprocal lattice space mapping measurements show that the a-lattice constants of ZnMgO layers are nearly equal to that of ZnO, which indicates the formation of pseudomorphic ZnMgO layers.

Author(s) Nakano Tatsuya, Masafumi Shirai, Yoshio Miura and Kazutaka Nagano
Abstract We have studied the effect of the co-doping of oxygen or beryllium on the exchange interaction between chromium spins in chromium-doped gallium nitride, (Ga,Cr)N, by means of first-principles calculations. The ferromagnetic exchange interactions are reduced by the co-doping of beryllium near chromium. On the other hand, the oxygen co-doping reduces the ferromagnetic interaction remarkably only for the case of chromium-oxygen-chromium complex formation. For increasing the Curie temperature of (Ga,Cr)N, it is necessary to fabricate the region that contains chromium ions densely in the sample by using, e.g., the delta-doping method.

10-3 Title Current- and magnetic field-induced domain wall motion in a ferromagnetic semiconductor (Ga,Mn)As structure
Author(s) Michihiko Yamanouchi, Daichi Chiba, Fumihiro Matsukura, Tomasz Dietl and Hideo Ohno
Abstract To study the mechanism of domain wall (DW) motion by current, we have measured the DW velocity moved by external magnetic fields in a 20-nm thick (Ga0.955Mn0.045)As film with perpendicular magnetic easy axis, which is the same sample used for the measurements of the current-induced DW velocity in our previous work (Phys. Rev. Lett. 2006). The results show that the magnetic field-induced DW creep scales differently compared to current-induced DW motion, indicating critical role of spin-transfer.

10-4 Title Theoretical consideration of determining accurate acoustical physical constants of AlN single crystals
Author(s) Yuji Ohashi, Mototaka, Arakawa, Hiroyuki Odegawa and Jun-ichi Kushibiki
Abstract AlN single crystal belonging to the class 6mm of the hexagonal system is a promising material for applications of acoustic wave devices operating at high frequency as well as ultraviolet light emitting devices. In this paper, a method of accurately determining acoustical physical constants of AlN was theoretically investigated using the line-focus-beam / plane-wave ultrasonic material characterization system. Proper combinations of propagation directions and modes that make measurement errors in the determined constants small were selected through calculations using the published constants of AlN single crystals. We developed a determination procedure of the constants.

10-5 Title Optical detection of local nuclear spin coherence in semiconductor quantum wells
Author(s) Shunichiro Matsuzaka, Haruki Senada, Yusuke Kondo, Ken Morita, Yuzo Ohno and Hideo Ohno
Abstract We demonstrate detection of nuclear spin coherence in n-GaAs/AlGaAs (110) quantum wells by a time-resolved Kerr rotation (TRKR) technique combined with pulse rf NMR. The Larmor precession of the electron spins was monitored by TRKR as a measure of local nuclear magnetic field. The temporal nuclear polarization after the irradiation of a single-pulsed resonant rf magnetic field for 71Ga was observed by the change of the Kerr rotation angle K at a fixed time delay between pump and probe pulses. We traced the oscillation of K, i.e. the Rabi oscillation, as a function of the pulse width.

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Session 13: Plasma Science, Optical Devices and Surface Science I

13-1 Title Invited talk: Water-Soluble Fluorescent Bio-Compatible Carbon Nanotubes Using PEGylated Fluorescein
Author(s) Nozomi Nakayama-Ratchford, Sarunya Bangsaruntip, Xiaoming Sun and Hongjie Dai
Abstract We report the use of PEGylated fluorescein to non-covalently functionalize single-walled carbon nanotubes (SWNTs). Fluorescein (fluor), a commonly used fluorophore, is found to adsorb onto the sidewall of SWNTs, and the hydrophilic polyethylene glycol (PEG) chain linked to the fluor can impart water solubility. The resulting SWNT-fluor-PEG suspension was found to be stable in aqueous environments even at high temperatures and more importantly, in biological media. Fluorescence of the fluor adsorbed on SWNT is quenched; however, it remains sufficiently fluorescent for use as a fluorescent label. The utility of SWNT-Fluor-PEG as a simultaneous fluorescent marker and transporter into cells is demonstrated.

13-2 Title Effects of Ion-Energy and -Flux on the Growth of Freestanding-Individual Single-Walled Carbon Nanotubes with Diffusion-Plasma CVD
Author(s) Toshiaki Kato and Rikizo Hatakeyama
Abstract A combination of plasma-processing and nanotube-manipulation techniques is an inevitable issue for a future application of nanotube-based electronics devices. On the other hand, any quantitative discussion has not been achieved about effects of plasmas on a structural deformation of single-walled carbon nanotubes (SWNTs). This background motivates us to investigate the effects of ions on the growth of SWNTs during a plasma chemical vapor deposition. According to detailed plasma characterizations, there exists an obvious threshold of the ion energy for the growth of damage-free high quality SWNTs, and a diffusion area in the plasma is found to be fairly suitable to fulfill such a condition.

13-3 Title Effect of Mn-Mn distance on magnetism for NiAs-type Mn50(Te50-xSbx) films fabricated by sputtering method
Author(s) Yoshito Ashizawa, Shin Saito, Masakiyo Tsunoda and Migaku Takahashi
Abstract The structures, magnetisms, and their correlation for the NiAs-type 50(Te50-xSbx) films fabricated by sputtering method were investigated with changing the nearest Mn-Mn distance, dMn-Mn, by substitution of Te and Sb. It was found that the dMn-Mn decreased with gentle slope from 3.34 to 3.31 Å in 0 ≤ x ≤ 16, and reduced gradually down to 2.89 Å in x ≥ 23, and the magnetism of the Mn50(Te50-xSbx) films with the dMn-Mn from 2.89 Å to 3.34 Å was changed from antiferromagnetism to ferrimagnetism, and discontinuously to ferromagnetism with decreasing the dMn-Mn.

13-4 Title Epitaxial Growth of Highly-Strained-Si/Relaxed-Ge/Si(100) Using ECR Plasma CVD for Future Si-based Heterodevices
Author(s) Katsutoshi Sugawara, Masao Sakuraba and Junichi Murota
Abstract By using electron-cyclotron resonance Ar plasma enhanced SiH4 and GeH4 reaction, epitaxial growth of highly-strained-Si/relaxed-Ge/Si(100) without substrate heating has been investigated. Deposited Si on the relaxed Ge/Si(100) has atomically flat surface and large strain, and intermixing at hetero-interface of strained-Si/relaxed-Ge is not observed. Especially, strain amount of 1.7-nm-thick strained Si reaches about 4 %, whose value indicates that strained Si lattice is almost matched to the relaxed Ge one. These results indicate that lowering deposition temperature is necessary to obtain highly strained Si on Ge buffer.

13-5 Title Electronic and Magnetic Properties of Fe Filled Single-Walled Carbon Nanotubes
Author(s) Yongfeng Li, Toshiro Kaneko, Tomoyuki Ogawa, Migaku Takahashi and Rikizo Hatakeyama
Abstract Electronic properties of single-walled carbon nanotubes (SWNTs) filled with Fe are studied by fabricating them as the channels of field-effect transistors (FETs) devices. The synthesis of Fe-filled SWNTs is realized by using ferrocene as a starting material. Our results reveal that Fe-filled SWNTs can exhibit high performance unipolar n-type semiconducting behavior at a high filling level and p-n junction diode behavior at a low filling level. Moreover, at a low temperatures Coulomb blockade phenomenon is significantly observed on SWNTs due to the Fe encapsulation. Furthermore, magnetic measurements indicate that superparamagnetic behavior is observed for encapsulated Fe particles due to their small size.

13-6 Title Electrical Transport Properties of Cs-encapsulated Double-Walled Carbon Nanotubes Synthesized Via Plasma Ion-Irradiation Method
Author(s) Yongfeng Li, Rikizo Hatakeyama and Toshiro Kaneko
Abstract Electronic transport properties of Cs-encapsulated double-walled carbon nanotubes (DWNTs) synthesized via a plasma irradiation method are investigated for the first time. Our results indicate that Cs-encapsulated DWNTs exhibit a high performance n-type characteristic in contrast to ambipolar behavior of pristine DWNTs. At low temperatures Coulomb blockade transport characteristics are observed for the encapsulated DWNTs, and the size of quantum dots formed in DWNTs is estimated on the order of several nanometers. The electronic properties of the Cs-encapsulated DWNTs are found to be controllable by adjusting the Cs filling level during the plasma ion irradiation process.

13-7 Title 3C-SiC(111) film grown on Si(110) substrate using organosilane
Author(s) Atsushi Konno, Maki Suemitsu, Yuzuru Narita, Hideki Nakazawa, Kanji Yasui, Takashi Ito and Tatso Endo
Abstract Heteroepitaxy of 3C-SiC on Si(110) substrate has been conducted by using monomethylsilane gas-source MBE. X-ray diffraction (XRD) indicates formation of a (111)-oriented SiC film on this Si(110) substrate. The FWHM of the XRD rocking curve, as compared with a 3C-SiC(111) film grown on Si(111) substrate, is reduced by 41% (out-of-plane), and the lattice-constant anisotropy between the lateral and the growth directions is also reduced. These results indicate improved crystallinity of the present 3C-SiC(111)/Si(110) film as a result of reduced strain in the film.

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Session 16: Plasma Science, Optical Devices and Surface Science II

16-1 Title Invited talk: Non-thermal plasma synthesis and passivation of silicon nanocrystals
Author(s) Lorenzo Mangolini and Uwe Kortshagen
Abstract A non-thermal continuous flow reactor for the synthesis of small silicon nanoparticles will be presented. Contrary to other gas phase techniques, our approach allows obtaining freestanding crystals that are small enough to show photoluminescence in the visible and with a high production rate. Liquid and gas phase passivation techniques have been tested to passivate defects at the particle surface and to obtain the optimum optical properties. Quantum yields beyond 60% have been reproducibly measured for samples that have a peak emission wavelength around 800 nm and that have been capped in the liquid phase with 1-dodecene.

16-2 Title Controlled Ion Irradiation to Liquids in RF Discharge Plasmas
Author(s) Kazuhiko Baba, Toshiro Kaneko and Rikizo Hatakeyama
Abstract Ion behaviors at an interfacial region between gas and liquid phases are investigated using radio frequency discharge plasmas coexisted with liquids in vacuum system. The ions are found to be irradiated to liquids with their energies controlled, which is realized by the formation of sheath electric fields on the liquid surface. In the case that ionic liquids are used as the liquid-phase medium, the ion irradiation causes the change of liquid color and has an effect on the plasma parameters in gas phase such as an increase in the electron density.

16-3 Title Formation of P Atomic Layer Doped Si/Si1-xGex (100) Heterostracture Using Ultraclean LPCVD For Future Si Based Heterodevices
Author(s) Yohei Chiba, Masao Sakuraba and Junichi Murota
Abstract P atomic layer doping in Si epitaxial growth by alternately supplied PH3 and Si2H6 using ultraclean low pressure CVD have been investigated. By Si epitaxial growth on the P surface at 450 oC using Si2H6, heavy P doping with the P concentration over 3x1021 cm-3 is achieved in an ultrathin region. Hall mobility of electron is higher than that for uniformly P-doped Si with lower P concentration of 1020 cm-3. From the mobility degradation by heat treatment up to 800 oC, it is expected that two-dimensional arrangement of P atoms is achieved for the as-deposited films.

16-4 Title Room-Temperature Emission of Terahertz Radiation from InGaP/InGaAs/GaAs Grating-Bicoupled Two-Dimensional Plasmon-Resonant Photomixers
Author(s) Mitsuhiro Hanabe, Yahya Moubarak Meziani, Taiichi Otsuji and Eiichi Sano
Abstract We experimentally observed terahertz emission of radiation stimulated by photoinduced two-dimensional (2-D) plasma instability at room temperature from our original InGaP/InGaAs/GaAs grating-bicoupled plasmon resonant photomixer. Photoelectrons drifting into highly-dense plasmon cavity grating from adjacent lightly-dense one extensively promote the plasma instability, resulting in emission of terahertz radiation. Vertical cavity formed between the 2-D plasmon grating plane and the indium-tin-oxide (ITO) mirror at the back surface gains the radiation. Photoresponses to CW lasers were first measured, showing extraordinary plasmon resonant peaks. Electromagnetic response to 80-fs impulsive photoexcitation shows stimulated emission of radiation in the terahertz range.

16-5 Title Measurement of few-photon optical nonlinearity
Author(s) Nobuyuki Matsuda, Ryosuke Shimizu, Yasuyoshi Mitsumori, Hideo Kosaka and Keiichi Edamatsu
Abstract Measurement of single-photon optical nonlinearity will be a key technique to the quantum information processing. We are trying to measure such weak nonlinearity, constructing a highly sensitive and robust measurement system which realizes a measurement of small nonlinear phase shifts induced by a few photons via cross-Kerr effect. We used a photonic crystal fiber as a nonlinear medium. Firstly, we demonstrated it in a classical regime to evaluate our system. Secondly, by suppressing optical noises, we measured few-photon nonlinear phase shifts. Finally we have successfully measured ~10-6 rad. nonlinear phase shifts induced by approximately 10 photons.

16-6 Title Magnetic viscosity phenomena in exchange coupled CoFe/MnIr bilayers
Author(s) Dong Young Kim, Masakiyo Tsunoda and Migaku Takahashi
Abstract The complex permeability spectra were measured in the low (10 Hz ~ 1 MHz) and microwave (100 MHz ~ 9 GHz) frequency ranges in CoFe/MnIr bilayers. The magnetic viscosity effect is dominantly observed below the critical antiferromagnet thickness (tcAF) at low frequency range. This phenomenon was analyzed using the relaxation behavior of AF layer coupled with ferromagnet layer across the exchange anisotropy Jc. Over the AF relaxation frequency, the AF spin become stable and nearly fixed. Therefore, we conclude that the enhanced total effective field at tAF tcAF directly correlated to Jc, but not depends on anisotropy constant of AF layer.

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