bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of Diameter on Longitudinal Displacement in Disk Shape 10-μm-thick Lead Zirconate Titanate Films
Authors: Iijima Takashi , Osone Satoko , Shimojo Yoshiro , Okino Hirotake , Yamamoto Takashi 
Published: April 2011

AbstractMicro-machined piezoelectric film devices are usually fabricated onto substrates, so that the displacement response of the film is clamped with the substrate. To investigate the longitudinal displacement behavior of 10-μm-thick lead zirconate titanate (PZT) films deposited onto Si substrates, disk shape structures with diameters of 20 to 80-μm were fabricated by an reactive ion etching (RIE) process. The polarization-field (P-E) hysteresis curves did not show a remarkable difference with decreasing the PZT disk diameter. On the other hand, unipolar driven longitudinal displacement increased, and the amount of the displacement was saturated at a diameter of 30 and 20 μm. The AFM measured longitudinal piezoelectric constants, AFM d33, were estimated in the case of before poling and after poling at 100V for 10 min. The AFM d33 for the before and after poling process were 65 and 94 pm/V for 80-μm-diameter film disk, and 153 and 315 pm/V for 20-μm-diameter film disk, respectively. The value of poled AFM d33 for 20-μm-diameter film disk was comparable to bulk PZT ceramics. These results suggest that the decrease of the disk diameter reduces the Si substrate bending related with the clamping effect between the film and substrate, and facilitates domain reorientation in the poling process. It seems that the actual piezoelectric constant of films can be estimated from the longitudinal displacement when the ratio of the PZT disk diameter, d, to the PZT film thickness, t, shows d/t < 3 for 10-μm-thick PZT films.
Effect of PLT Buffer Layers on the PZT Thin Films for Scaling-Down Ferroelectric Materials
Authors: Dong Hua Li , Lee Eun Sun , Chung Hyun Woo , Ahn Byung Du , Lee Sang Yeol 
Published: April 2011

AbstractThe Hysteresis characteristics of below 400 nm- thick Pb(Zr0.52Ti0.48)O3 (PZT) thin films grown on Pt (111) /Ti/SiO2/Si substrates have showed very poor with remanent polarization of 1∼3 μC/cm2 in our previous research. To study the further scaling-down, we introduced the method of our previous research that the (Pb0.72La0.28)Ti0.94O3 (PLT) buffer layers play an important role in enhancing the ferroelectric properties of the PZT thin films. As a result, the remanent polarization of 300 nm-thick PZT thin films with the 10 nm-thick PLT buffer layers have showed 32 μC/cm2 at applied voltage of 8 V and 24 μC/cm2 at applied voltage of 5 V. Inserted the PLT seed layers between the PZT thin films and substrate, the hysteresis characteristics of PZT thin films were improved a lot. The dielectric and leakage current properties of PZT thin films were also investigated.
Observation of Domain Switching in Fatigued Epitaxial Pb(Zr,Ti)O3 Thin Films
Authors: Kim Yong Kwan , Yokoyama Shintaro , Ueno Risako , Morioka Hitoshi , Sakata Osami , Kimura Shigeru , Saito Keisuke , Funakubo Hiroshi 
Published: April 2011

AbstractWe performed x-ray diffraction measurements by using highly brilliant synchrotron radiation on epitaxial Pb(Zr0.35Ti0.65)O3 film capacitor structures. Small regions of 300-nm-thick epitaxial Pb(Zr,Ti)O3 thin films with Pt and SrRuO3 top electrodes were measured after applying various numbers of switching cycles of the electric field. Epitaxial Pb(Zr,Ti)O3 thin films were prepared on epitaxial (100)cSrRuO3/(100)SrTiO3 substrates by pulsed-metalorganic chemical vapor deposition. The volume faction of c-domain and remanent polarization was plotted against the number of switching cycles. In the both capacitors, the Vc increased as the switching cycle increased independent of fatigue behavior.
Morphology Control, Dopant Incorporation, and Selective Epitaxial Growth of 4H-SiC at Low Temperatures Using CH3Cl Growth Precursor
Authors: Koshka Yaroslav , Krishnan Bharat , Lin Huang-De , Melnychuk Galyna 
Published: April 2011

AbstractLow-temperature homoepitaxial growth of 4H-SiC using halo-carbon precursors was further investigated to address the problems limiting increase of the growth rate of the defect-free epilayers at growth temperatures below 1300°C. Enhanced etching of Si clusters in the gas phase was achieved by adding HCl during the low-temperature growth. The effective Si/C ratio above the growth surface was increased as a result of reduced depletion of silicon vapor species by cluster condensation, which resulted in drastically improved epilayer morphology and significant increase of the growth rate. An intentional insitu nitrogen doping of epitaxial layers during 1300°C growth on Si and C faces revealed more than an order of magnitude higher nitrogen donor incorporation in the C-face epitaxial layers. Finally, a feasibility of selective epitaxial growth using low-temperature masking materials such as SiO2 was demonstrated.
High-Resolution X-ray Topography of Dislocations in 4H-SiC Epilayers
Authors: Kamata Isaho , Tsuchida Hidekazu , Vetter William M , Dudley Michael 
Published: April 2011

AbstractSilicon carbide (SiC) substrates and epilayers contain many crystal defects, such as micropipes, screw dislocations, threading edge dislocations (TEDs), basal plane dislocations (BPDs) and stacking faults. To investigate these defects, synchrotron radiation topography is frequently carried out. When the monochromatic synchrotron X-ray topography is taken by the grazing-incidence reflection geometry using 11-28 reflection, screw dislocations, TEDs and BPDs are simultaneously seen and shown as different topographic images [1]. Many studies of dislocations were reported using 11-28 reflections in 4H-SiC [1,2]. Topographic images of the dislocations have been analyzed by the ray-tracing method of computer simulation [3]. However, experimental images of dislocations were not fully matched to the fine structure of simulation images, because of a lack of resolution in recording media: conventional films and nuclear emulsion plates [3]. This time, we report obtaining high-resolution topographic images using a new recording medium, and compare results between the experiment and the computer simulation. Synchrotron topography in 11-28 reflection was carried out at SPring8 applying holography films as high-resolution recording media. The TED images are distinguished as four types, which have ribbon-like features with different rotating angles, through the use of the films. The four different TED images agree well with the computer simulated images which have been reported by Vetter et.al. taking into account of the different Burgers vector directions [3]. By comparing the three topographic images taken at g=-12-18, 11-28 and 2-1-18, we confirmed experimentally that the four types of TED images originated from the difference of Burgers vector directions. We also investigated high-resolution topographic images of elementary screw dislocations, micropipes, and BPDs in 4H-SiC epilayers. The experimental image of screw dislocation fairly matched with simulated image. The fine features in the experimental topographic images of micropipes and BPDs are also compared with the simulated images in detail. [1] T. Ohno, H. Yamaguchi, S. Kuroda, K. Kojima, T. Suzuki, K. Arai: J. cryst. Growth. Vol. 260 (2004) 209. [2] H. Tsuchida, T. Miyanagi, I. Kamata, T. Nakamura, R. Ishii, K. Nakayama and Y.Sugawara: Jpn. J. Appl. Phys. Vol. 25, (2005), L806-808. [3] W. Vetter, H. Tsuchida, I. Kamata, M. Dudley: J. Appl. Cryst. Vol. 38, (2005), 442-447.
The Formation Mechanism of Carrot Defects in SiC Epifilms
Authors: Chen Hui , Wang Guan , Chen Yi , Jia Xiaoting , Bai Jie , Dudley Michael 
Published: April 2011

AbstractCarrot-like defects in a 7&#61616; off-cut (from [0001] toward <1-210> direction) 4H-SiC wafer with a 36μm thick 4H-SiC epilayer have been investigated using Nomarski optical microscopy, synchrotron white beam x-ray topography (SWBXT), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). X-ray topographs confirm that threading screw dislocations are often associated with the carrots. Cross-sectional TEM observation confirms that a prismatic stacking fault exists below the carrot. This fault was found to show contrast in all observed diffraction geometries except for g=0004. A model for the mechanism of formation of this type of defect during epitaxial growth is proposed.
Deep Levels in As-Grown and Electron-Irradiated P-type 4H-SiC
Authors: Danno Katsunori , Kimoto Tsunenobu 
Published: April 2011

AbstractDeep levels in as-grown and electron-irradiated p-type 4H-SiC have been investigated by deep level transient spectroscopy (DLTS). Three hole traps, namely HK2, HK3, and HK4, could be detected in the temperature range from 350K to 700K. Activation energies of the hole traps were estimated to be 0.84 eV for HK2, 1.27 eV for HK3, and 1.44 eV for HK4 from the Arrhenius plot of emission-time constants assuming temperature-independent capture cross section. By double-correlated DLTS (DDLTS), they were revealed to be donor-like (+/0) traps. The concentrations of HK3 and HK4 centers were clearly increased by low-energy (116 keV) electron irradiation. Based on thermal stability of the HK3 and HK4 centers up to 1350°C and the dependence of HK4 concentration on the electron fluence, they may originate from a complex including defect(s) caused by carbon displacement.
Advances in 4H-SiC Homoepitaxy for Production and Development of Power Devices
Authors: Thomas Bernd , Hecht Christian , Stein René , Friedrichs Peter 
Published: April 2011

AbstractIn this paper we present results of epitaxial layer deposition for production needs using our hot-wall CVD multi-wafer system. This equipment exhibits a capacity of 7x3” wafers per run and can be upgraded to a 6x4” setup. Characteristics of epilayers and reproducibility of the proc-esses are reported. Furthermore, we show recent results of p-type SiC homoepitaxial growth on 3” 4° off-oriented substrates using a single-wafer hot-wall CVD. The dependence of layer prop-erties on growth parameters, doping and thickness uniformity as well as doping memory effects are discussed. For the characterization of epitaxially grown pn-junctions first research grade pin-diodes were fabricated. The p-type emitters were either deposited in the same growth run to-gether with the n-type buffer and drift layers (continuous growth) or the n- and p-layers were grown in two different growth runs (separate growth).
Degradation of Current Gain in SiC BJTs
Authors: Agarwal Anant , Krishnaswami Sumi , Richmond James , Capell Craig , Ryu Sei-Hyung , Palmour John , Jones Kenneth , Scozzie Charles 
Published: April 2011

AbstractThe reduction in the current gain of SiC BJTs has been observed after operating the devices for as little as 15 minutes. It is accompanied by an increase in the on-resistance of the BJT. The origin of the current gain degradation in the BJTs is investigated. Two possible mechanisms, which may be simultaneously present in the device, are thought to be responsible: (a) increase in the surface recombination particularly in the region between the emitter and the base implant, and (b) bulk recombination in the base due to the generation and growth of stacking faults. Initial observation reveals the presence of stacking fault in the base-emitter region when the device is forward-biased. At the same time, minimizing the effect of recombination from the surface using improved passivation helped in the suppression of the current gain degradation in SiC BJTs.
DNA-Templated Assembly of Conducting Gold Nanowires
Authors: Satti Amro , Aherne Damian , Barrett Claire , Floyd Liam , Quinn Aidan , Redmond Gareth , Fitzmaurice Donald 
Published: April 2011

AbstractThe use of DNA to template the assembly of gold nanowires from gold nanoparticles is reported. Double-stranded calf thymus DNA, was deposited on a polystyrene-coated silicon wafer substrate. The substrate was then exposed to an aqueous dispersion of positively charged gold nanoparticles (~ 4 nm diameter), which adsorbed at the negatively charged DNA template. The adsorbed nanoparticles were then enlarged and enjoined by electroless deposition leading to formation of continuous nanowires of 85 nm average diameter. Gold electrodes were then overlaid on individual nanowires using conventional lithographic techniques. Two-terminal current-voltage measurements were employed to characterize the electrical characteristics of single nanowires. The nanowires exhibit resistivity values < 6 × 10-7 Ωm. These and related findings have implications for the design and assembly of next generation electronic devices.
Understanding and Control of Lateral Contraction in Stamping Lithography
Authors: Li Zheng , Tan Li , Liu Gang-yu 
Published: April 2011

AbstractThin film contraction under external mechanical stress can be used to miniaturize size and increase density of patterned features on top. Nonlinear Finite Element Analysis is used to provide guidance on this contraction process. It was found that the substrate contraction causes stress accumulation along interfaces between protruded features and substrate. These stress accumulation complexes the control of profile changes on patterned features and suggest a design of patterned features arranged beyond a critical distance to avoid cross-interference.
Controlling Length of Gold Nanorods and Monitoring Their Growth Mechanism Using X-ray Absorption Spectroscopy
Authors: Liu Ru-Shi , Chen H. M. , Hu S. F. 
Published: April 2011

AbstractA new approach to fabricate long length of gold nanorods by controlling the volume of growth solution will be reported. The shape evolutions ranging from fusiform nanoparticles to 1-D rods was observed. Increasing the addition of growth solution can control the length of nanorods. The length of rods can be extended to 2 £gm, and nanorods with aspect ratios of up to ~ 70 could be obtained. Moreover, X-ray absorption spectroscopy (XAS) is applied herein to elucidate the growth mechanism of gold nanorods. The gold ions were directly reduced to gold atoms by ascorbic acid during the reaction, and then gold atoms were deposited on the surface of gold seeds that were introduced into the reaction. Extended X-ray absorption fine structure (EXAFS) confirmed the growth of gold and the environment around Au atoms over the reaction. The XAS are expected to have wide applications in the growth of gold and other related materials.
Experimental and Ab-initio Investigations of Osmium Diboride
Authors: Hebbache M. M. , Stuparevic L. , Zivkovic D. , Zemzemi M. 
Published: April 2011

AbstractMore than half a century after their discovery, almost nothing is known about the physical properties of osmium borides, thought their structures have been clearly identified in the early sixties. We re-examined the phase diagram of the binary system osmium-boron and confirm the existence of two hexagonal phases, OsB1.1, Os2B3 and an orthorhombic phase, OsB2. Our microhardness measurements show that the synthesized OsB2 is extremely hard. In addition, first-principles calculations have been conducted to investigate its physical properties. It is shown that OsB2 is also a low compressibility material. Most of the transition metal borides have already found applications as in protective armor, nuclear reactors, reinforcement, etc. OsB2 can be used in applications like hard coating.
Photolithographic Process Based on High Contrast Acrylate Photoresist for Multi-Protein Patterning
Authors: Chatzichristidi Margarita , Petrou Panagiota S. , Douvas Antonios M. , Diakoumakos Constantinos D. , Raptis Ioannis , Misiakos Konstantinos , Kakabakos Sotirios S. , Argitis Panagiotis 
Published: April 2011

ABSTRACTContinuing the effort of our group for biocompatible, photoresist-based lithographic processes, high contrast near UV photoresists are presented along with a novel multi-step lithographic scheme. The proposed lithographic scheme is based on successive lithographic steps (exposure at 310 nm) on the same substrate for the patterning of different proteins. The photoresists are based on (meth)acrylate tetrapolymers and a near UV sensitive sulfonium salt as photoacid generator and can be processed under mild baking and development conditions allowing patterning of proteins without denaturation and loss of their molecular recognition capability. Protein patterning in successive lithographic steps down to 2μm has been achieved. Sub-1μm patterning structures have been also obtained. Lithographic results were evaluated with SEM and fluorescence microscopy, after the recognition of the patterned biomolecules by their fluorescently labeled counterparts.
Spin Relaxation in SiGe Islands
Authors: Malissa Hans , Jantsch Wolfgang , Chen Gang , Lichtenberger Herbert , Fromherz Thomas , Schäffler Friedrich , Bauer Günther , Tyryshkin Alexei , Lyon Stephen , Wilamowski Zbyslaw 
Published: April 2011

ABSTRACTWe present our work on the spin relaxation of electrons confined in SiGe islands. Ge islands are grown on unstructured and structured Si(100) substrates by MBE, and lead to strain in the Si layer that is deposited on top. These quantum dot structures are investigated by photoluminescence and electron spin resonance (ESR) experiments, the latter both in continuous wave and pulsed mode. We observe a g-factor and an ESR line width that correspond to Si conduction band electrons with additional inhomogeneous broadening.
The Role of Local Fields in the Optical Properties of Silicon Nanocrystals
Authors: Trani Fabio , Ninno Domenico , Cantele Giovanni , Iadonisi Giuseppe 
Published: April 2011

ABSTRACTIn this paper we discuss the role of local fields in the optical properties of silicon nanocrystals. Using a semiempirical tight binding approach, local field effects are included into the linear response theory, going beyond the standard independent particle approximation. The results show that local field effects give an important contribution to the optical properties of silicon nanocrystals, leading to a strong suppression of the absorption in the visible spectral range. This effect is attributed to the classical surface polarization contribution. A comparison between the atomistic tight binding approach and a classical dielectric model shows that the dielectric model gives reasonable results not only for large, but even for small silicon nanocrystals.
Multi-mode Mid-IR Silicon Raman Amplifiers
Authors: Jalali Bahram , Raghunathan Varun , Rice Robert R 
Published: April 2011

ABSTRACTThis paper discusses the prospects of silicon as a Mid-wave Infra-red Raman crystal. As a specific example of novel devices that can be realized, we introduce the concept of multi-mode silicon Raman amplifiers and their application in infrared image pre-amplification. The same technology also has application in incoherent beam combining.
Carbon Nanotubes as Potential Cold Cathodes for Vacuum Microelectronic Applications
Authors: Gupta Sanju 
Published: April 2011

ABSTRACTMaterials science is playing a dramatic role in discovering new materials with tailored physical properties. Cold cathodes/field emitters are one of the examples. Electron field emitting materials are of vital importance for a variety of vacuum microelectronic devices including field emission displays for flat panel displays, electron microscopes, X-ray generators, and vacuum lamps. This is the driving force to investigate the advanced nanostructured carbons as cold cathodes as one of the potential candidates. Recently, they are also being proposed for thermionic power generators. The rationale is that reducing one or more dimensions of a system below some critical length changes the systems' physical properties, where carbon nanotubes (CNTs) in the class of carbon nanostructures serve as a model example. In this paper, synthesis and characterization of vertically aligned multiwall and single-/double-wall carbon nanotube films using a microwave plasma-assisted chemical vapor deposition technique for vacuum microelectronics is presented. Recent advances in their synthesis, processing, and characterization indicate that the above mentioned potential is slowly being realized. Experiments showed that by continuous reduction in the thickness of the catalyst film produces hollow concentric tubes in contrast to bamboo-like multiwalled tubes with larger thickness. To assess the electron field emission properties, besides the traditional field emission (I-V) properties, temperature dependent field electron emission microscopy (T-FEEM) enabling real-time imaging of electron emission providing information on emission site density, temporal variation of the emission intensity, and insight into the role of adsorbates from nanotube films will be discussed. Physics based models (such as negative or low electron affinity, geometric enhancement, surface dipole, tunneling due to adsorbates, structure modification due to doping etc.) will be described to support the experimental observations in addition to weak thermionic field emission contribution. These findings provided a great insight into the field emission mechanism and a contrasting comparison between small and large diameter carbon nanotubes.
Chemically Modified Multiwalled Carbon Nanotubes as an Additive for Supercapacitorsβ
Authors: Kim Yong-Jung , Abe Yusuke , Yanagiura Takashi , Kitani Masaaki , Kodama Tsuyoshi , Higuchi Keita , Endo Morinobu 
Published: April 2011

ABSTRACTThe incorporation of chemically modified multi-walled carbon nanotubes (MWNTs) have demonstrated, as an additive material to enhance the electrical conductivity, into the electrode gives rise to a highly improved rate capability of a super-capacitor. The preferential attack of potassium hydroxide on less disordered carbon results in the formation of high-performance MWNTs with increased surface area, electrical conductivity and sustained long tube morphology, simultaneously. It is envisaged that newly developed functional MWNTs will be utilized in various electrochemical systems, where high current is critically required.
Patterning Scheme Based on Photoacid Induced Spectral Changes for Single Layer, Patterned Full Color Light Emitting Diodes
Authors: Vasilopoulou Maria , Pistolis Giorgos , Botsialas Athanasios , Stathopoulos Nikos , Rangoussi Maria , Argitis Panagiotis 
Published: April 2011

ABSTRACTPhotochemically induced emission tuning (PIET) for the definition of different color emitting areas in a single conducting polymeric layer is demonstrated. The commercially available poly(9-vinylcarbazole) (PVK), well known as a hole transporting layer in OLEDs technology, was used. The three primary colors emitting areas in a single layer of PVK film were defined using a suitable green emitter 1-[4-(dimethylamino)phenyl]-6-phenylhexa-1,3,5,-triene (DMA-DPH) along with the red emitter (4-dimethylamino-4'-nitrostilbene) (DANS). The selected emitters were dispersed in the PVK films in the presence of a photoacid generator (PAG). Various onium salts were tested as photoacid generators in order to select those, which could cause effectivily the photoinduced protonation and emission tuning of the probes molecules. Through proton induced bleaching of the red emitter and proton induced spectral shift of the green one, the definition of all three primary color emitting areas was possible. In this way the unexposed areas of the film remain red, the areas exposed with the intermediate dose become green and the fully exposed areas emit blue color. Intermediate colors and white light can also be obtained.