bluuebunny/crossref_metadata_2025_split huggingface dataset:
Soft Lithography Fabrication of Fully Flexible and Transparent all Organic FETs for Large Area Applications
Authors: Cosseddu Piero , Orgiu Emanuele , Bonfiglio Annalisa 
Published: April 2011

ABSTRACTFully flexible and transparent all organic field effect transistors were fabricated by means of an innovative and inexpensive technique. A 1.8μm thick polyethylenetetherephtalate sheet, Mylar® (Du Pont), was used as gate dielectric and at the same time as mechanical support for the whole structure. We used pentacene, deposited by thermal sublimation, as semiconducting layer, whereas poly(ethylene-dioxythiophene)/polystyrene sulfonate (PEDOT/PSS) was used for the realization of the electrodes. Gate electrodes were realized by spin coating, while source and drain electrodes were patterned by micro-contact printing. We fabricated typical p-type field effect transistors, with mobilities up to 2 × 10−1cm2/Vs and Ion/Ioff up to 105, in a very simple and inexpensive way. It is worth to note that this technique allows the realization of bottom contact and top contact transistors. We realized both bottom contact and top contact devices on the same substrate and with the same active layer and we investigated how the structure itself and the active layer morphology influence the electrical properties in terms of hole mobility, Series Contact Resistance and parasitic capacitance effects. The comparison between top-contact and bottom-contact devices shows interesting marked differences that can be mainly attributed to a different PEDOT:PSS/semiconductor interface quality, influencing the most meaningful parameters. The flexibility of the obtained structure and the easy scalability of the technological process, suitable for roll to roll mass production processes, open the way for economic production of high-resolution organic devices
Electronic Structure of Defects in Fcc-C22
Authors: Domingos Helder Sousa 
Published: April 2011

ABSTRACTClassical and ab-initio calculations were carried out on bulk defects and surfaces of the carbon allotrope Fcc-C22. The results revealed a number of possible defects with spin polarization and one with antiferromagnetic character. The surfaces were shown to be able to host magnetic polarization. Extrinsic light dopants (H and N) were shown to introduce spin polarization for small dopant concentration and to metallize the systems for large concentrations.
Spin Injection and Spin Dynamics at CuPC/GaAs(100) Interface
Authors: Ding Huanjun , Gao Yongli , Sanchez-Albaneda Marina , Wüstenberg Jan-Peter , Cinchetti Mirko , Andreyev Oleksiy , Bauer Michael , Aeschlimann Martin 
Published: April 2011

ABSTRACTSpin injection from GaAs(100) to organic semiconductor copper phthalocyanine (CuPc) has been investigated experimentally with spin-resolved two-photon photoemission (SR-2PPE) spectroscopy. With SR-2PPE, the dynamics of both electron and spin relaxation have been studied with femtosecond time resolution. The spin-polarized electrons are originally generated in GaAs through optical pumping and injected into CuPc. We observed an enhancement in spin polarization at the interface after initial CuPc deposition. This demonstrates that interface spin scattering is insignificant, which is similar to our previous result of spin injection at CuPc/Co interface. The spin polarization dropped when the CuPc film became thick, an effect attributed to bulk attenuation in CuPc. The lifetime of the unoccupied orbits in CuPC was also studied with red-blue excitation of photon energy 1.56 eV and 3.12 eV, respectively. There was a strong asymmetry in the time-resolved spectra, and an unexpected long lifetime when the lower unoccupied orbital was excited. A simple explanation of this phenomenon will be discussed.
Sol-Gel Process Derived Superhydrophobic Silica Thin Films for Antistiction of MEMS Devices
Authors: Wong ChingPing , Zhu Lingbo , Hess Dennis W , Wong C. P. 
Published: April 2011

ABSTRACTBased on the theory of superhydrophobicity for low surface energy coatings, we describe a superhydrophobic antistiction silica coating for MEMS devices. The process uses a novel sol-gel process sequence with a eutectic liquid as a templating agent. The eutectic liquid displays negligible vapor pressure and very low melting point (12°C at ambient conditions) to reduce solvent loss during the high speed spincoating process. After a fluoroalkyl silane treatment, superhydrophobicity is achieved on the as-prepared silica thin film. The solvent can be extracted after the gelation and aging processes. Spin speed effect, eutectic liquid:TEOS ratio in the solution were studied in order to optimize the surface roughness to ensure excellent super-hydrophobicity. Comparison of the silica thin films with silicon pillar surfaces showed that superhydrophobicity for the traditional sol-gel derived silica films demonstrated significant improvement, especially under humid conditions. The AFM force curve obtained with a tipless probe showed that the interaction force is greatly reduced on a rough silica superhydrophobic surface. This result offers great potential to reduce stiction failures in MEMS devices.
Smooth Ag Film Deposited Using e-beam Evaporated Ge as an Intermediate Layer for Applications in Nanoscale Devices and Optical Superlens
Authors: Vj Logeeswaran , Kobayashi Nobuhiko P. , Wu Wei , Islam M.Saif , Xuanlai Fang Nicholas , Wang Shih Yuan , Williams R. Stanley 
Published: April 2011

ABSTRACTIn this paper, we highlight a new method to obtain smoother silver (Ag) film characterized by much smaller average RMS surface roughness of ∼0.7nm, peak-to-valley separation of ∼4nm and grain-size distribution ~15nm as compared to conventionally obtainable Ag film characterized by RMS surface roughness of ∼10nm, peak-to-valley separation of ∼20nm and grain-size distribution of ∼100nm. Thin Ag films of ∼15nm (optically thin) were deposited on double-polished borosilicate glass and silicon (100) substrates with 2nm Germanium (Ge) intermediate layers. An optically thick Ag film of 60nm was also prepared with 2nm Ge. The Germanium thicknesses were also varied and similar surface morphology improvements are observable on all the samples. The AFM image analysis shows that having the evaporated Ge intermediate layer drastically changes the Ag surface morphology, namely, the surface roughness, peak-to-valley and grain size distribution. Our smooth Ag results are very promising for applications in molecular electronics interconnect, optical metamaterials, plasmonic superlens and nanophotonics.
Assembly of Fine-Pitch Carbon Nanotube Bundles for Electrical Interconnect Applications
Authors: Zhu Lingbo , Hess Dennis W , Wong ChingPing 
Published: April 2011

ABSTRACTCarbon nanotubes (CNTs) have been proposed as electrical interconnects, due to their excellent properties. However, the current nanotube growth techniques suffer from several drawbacks. One of the main challenges for applying CNTs to the circuitry is the high growth temperature (>600°C). Such temperatures are incompatible with microelectronic processes. The other issue is the poor adhesion between CNTs and the substrates, which will result in long term reliability issues and high contact resistance. To overcome these disadvantages, we have successfully demonstrated a methodology that we term “CNT transfer technology”. The distinctive CNT-transfer-technology features are separation of CNT growth and CNT device assembly at solder reflow temperature. In this paper, we combined our expertise in growth of well-aligned open-ended CNT bundles with the CNT transfer process to assemble CNT bundles for fine-pitch interconnects applications. To demonstrate the feasibility of transfer process to assemble the fine-pitch CNT bundles, the CNT bundles with diameter, aspect-ratio and pitch of 25 μm, 4, and 80 μm, respectively, were assembled on the copper substrates. The measured resistivity of the long CNTs is ∼2.3×10−4 Ω-cm. The CNT-solder alloy interfaces were observed by the SEM. The results indicated that molten SnPb solder form strong mechanical bonding with open-ended CNTs, suggesting the superior CNT/solder interfacial properties by solder reflow process.
Making Plastic Remember: Electrically Rewritable Polymer Memory Devices
Authors: Prime Dominic , Paul Shashi 
Published: April 2011

AbstractOrganic based electronic memory devices are currently receiving an unprecedented amount attention as possible alternatives for conventional semiconductor memories, due to their simple device structures, ease of fabrication, compatibility with flexible substrates and low cost. Polymer memory devices (PMDs) based on active layers containing gold nanoparticles (Q-Au) with 8-hydroxyquinoline (8HQ) will be presented in this report. Memory performance attributes will also be presented, which are less reported in the literature, but still essential for the realisation of viable organic memory technologies.
Dielectric Characteristics of Donor Doped Nonlead Ba(Cu1/3Nb2/3)O3 Perovskite Material Synthesized by Microwave-assisted Citrate-nitrate Sol-gel Route
Authors: Manavbasi Alp , LaCombe Jeffrey C 
Published: April 2011

AbstractNonlead perovskite type, Ba(Cu1/3Nb2/3−xWx)O3 (x = 0, 0.025), ferroelectric ceramic powders (BCN) were prepared by the microwave-assisted citrate-nitrate sol-gel technique. The gel was formed from a stable and homogeneous sol prepared by mixing stable solutions of barium- and copper-nitrate, tungsten citrate, and peroxo-citrato-niobium precursors. Microwave irradiation of the gel resulted in a dark, fluffy precursor material after auto-combustion. Calcination of the as-combusted samples produces a single phase with tetragonal splitting in X-Ray diffraction patterns. The crystallite size of the synthesized samples was found to be 41 nm. Particle morphology and the size of nanocrystalline powders were characterized by scanning electron microscopy and photon correlation spectroscopy, respectively. Electrical and dielectric properties of sintered samples were investigated by impedance spectroscopy. The isothermal ac measurements were performed from room temperature, up to 600 °C for W6+ doped and undoped BCN samples.
HfOx Thin Films for Resistive Memory Device by Use of Atomic Layer Deposition
Authors: Chen Pang Shiu , Lee Heng-Yuan , Wang Ching-Chiun , Tsai Ming-Jinn , Liu Kou-Chen 
Published: April 2011

AbstractThe materials properties and resistance switching characteristics of hafnium oxide-based binary oxide were investigated for next generation memory device application. A nonstoichometric hafnium oxide (HfOx) film with a mixture structure of monoclinic and tetragonal phase and some metallic Hf-Hf bonds on TiN/Si were prepared by atomic layer chemical vapor deposition (ALCVD). Resistance random access memory devices consisting of Pt/HfOx/TiN/Si with low power operation (< 0.4 mW) and reset current (< 100 mA) were fabricated. The resistance ratio of high resistance state to low resistance state maintains 100∼1000 and after 1000 cycles of repetitively switching. A 1-nm-thick Al2O3 film in the interface between top electrode and HfOx films, the Pt/Al2O3/HfOx/TiN/Si memory devices were found that soft-error of set and reset process often occurred. Interface states in the anode side play an important role in maintaining a stable resistive switching for HfOx-based memory devices.
Preparation of Ge2Sb2Te5 Thin Film for Phase Change Random Access Memory by Magnetron Sputtering on Small Hole Patterns
Authors: Kikuchi Shin , Nishioka Yutaka , Kimura Isao , Jimbo Takehito , Ueda Masahisa , Kokaze Yutaka , Suu Koukou 
Published: April 2011

AbstractPhase Change Random Access Memory [PRAM] is one of the candidates for next generation memory due to its non-volatility, high speed, high density and compatibility with Si-based semiconductor process. Ge2Sb2Te5 [GST] thin film, an active layer in this device, is utilized because it has the well-known property of rapid crystallization without phase separation in erasable compact discs industry.In order to integrate PRAM to beyond 512Mbit, a high writing current and degradation of cell transition at small cell size become a problem. To resolve these problem, Confined Cell structure PRAM was suggested. However, it was difficult to fill GST layer in a small hole with a conventional sputtering tool because a big overhang occurred.In this work, we prepared GST films on the small hole patterned wafer by a new concept sputtering tool which designed developed a new concept sputtering tool. The structure of GST film was observed with cross section SEM and the film composition was measured with XRF.It was observed an overhang was suppressed and a GST film was filled in a small hole with a new concept tool. In addition, the uniformity of the GST film composition was good at less than 1% in 200mm φ substrate.
The effect of Porosity of Metal Zinc Films on the Formation of ZnO Prepared by Thermal Oxidation
Authors: Chao Liang-chiun , Liau Chung-chi 
Published: April 2011

AbstractZnO thin films have been prepared by thermal oxidation of metal zinc films with different porosity. High and low porosity metal zinc films are prepared by DC magnetron sputtering and capillaritron ion beam sputtering, respectively. Near bandgap UV emission of ZnO thin films prepared from thermal oxidation of the low porosity film exhibit a maximum PL intensity after thermal oxidation at 410°C, while ZnO films prepared by thermal oxidation of the high porosity films exhibit a maximum PL intensity at oxidation temperature of 900°C. SEM micrographs indicate that ZnO prepared by thermal oxidation of low porosity films have a smooth surface morphology after thermal oxidation at 410°C, while ZnO prepared by thermal oxidation of high porosity zinc films exhibit a grain size of ∼ 800 nm after thermal oxidation at 1000°C.
Cu-doped ZnSe Film with Stoichiometric Composition Deposited at Room Temperature using Compound Sources
Authors: Orita Masahiro , Narushima Takashi , Yanagita Hiroaki 
Published: April 2011

AbstractStoichiometric Cu-doped ZnSe crystalline films were prepared on glass substrates from ZnSe and Cu2Se powders using the evaporation method without intentional heating. Post-annealing treatment at 400°C in a vacuum improved the crystallinity, and no secondary phase was observed using X-ray diffraction for a film with a Cu concentration of Cu/(Zn + Cu) = 0.10, which had a conductivity of 28 Scm-1 and good transparency at green and red wavelengths. The thermal probe test indicated p-type carrier polarity, and the effects of annealing were confirmed by irradiating the as-deposited films with a YAG laser (ë = 355 nm). Possibility of producing transparent p-type conducting films on polymer substrates is demonstrated.
Characterization of CdS/CdTe Solar Cells Fabricated by Different Processes
Authors: Tamara Potlog , Khrypunov G. , Kaelin M. , Zogg H. , Tiwari A. N. 
Published: April 2011

AbstractThis paper analyses the photovoltaic parameters of the most promising CdS/CdTe solar cells for large application prepared by close space sublimation (CSS) and high vacuum evaporation (HVE). CdS/CdTe solar cells that have an efficiency of~10 % have been studied by current-voltage, capacitance-voltage and quantum efficiency measurements. The current-voltage characteristics show that the addition of small amounts of Cu or Te to back contacts by thermal evaporation improves contact properties by p+-doping the CdTe surface and creating a pseudo-ohmic contact. The cell deposited by CSS seriously suffers in FF compared to the cells prepared by HVE. For both types of the cells above mentioned measurements reveal that the efficiency of CdS/CdTe solar cells fabricated by CSS is limited by a light-dependent shunt resistance and by a high series resistance, but concerning of the cells fabricated by HVE - by the formation of a thick layer of CdS1-xTex at the interface.
Polarized Luminescence of Defects in CuGaSe2
Authors: Siebentritt Susanne , Augustin Sven , Papathanasiou Niklas , Hebert Damon , Rockett Angus , Bläsing Jürgen , Lux-Steiner Martha Ch 
Published: April 2011

AbstractThe linear polarisation of luminescence light allows conclusions on the symmetry of defects in semiconductors with non-cubic symmetry, like chalcopyrites, for which three shallow acceptors have been identified by photoluminescence. The polarisation dependent photoluminescence allows to determine the symmetry of the defects relative to the c-axis of the crystal. A simple geometrical model implies that chalcogen sites show a predominant direction perpendicular to the c-axis, while metal sites show a predominant direction parallel to the c-axis. Since all three shallow acceptors show polarization parallel to the c-axis, it can be concluded that they are situated on a metal site
Characterization of Local Electrical Property of Coincidence Site Lattice Boundary in Location-controlled Silicon Islands by Scanning Probe Microscopy
Authors: Matsuki Nobuyuki , Ishihara R. , Baiano A. , Hiroshima Y. , Inoue S. , Beenakker C.I.M. 
Published: April 2011

AbstractLocal electrical property of coincidence site lattice boundaries (CSLBs) in location-controlled silicon islands, which are fabricated using micro-Czochralski process (grain filter), was characterized by scanning spreading resistance microscopy (SSRM) and scanning spreading resistance microscopy (SCM). Some CSLBs found in a silicon island are analyzed as Sigma 3 and Sigma 9 by electron back scattering diffraction pattern. These CSLBs are determined as {111}Sigma 3 and {221}Sigma 9 by referring to previous observation results made by transmission electron microscopy. {111}Sigma3 CSLBs shows no activity for SCM or SSRM; this is consistent with previous prediction that {111}Sigma 3 CSLB is not electrical active. We verified a capability of SCM and SSRM for characterizing local electrical property of coincidence site lattice boundary in silicon.
Structural Analysis in Low-V-defect Blue and Green GaInN/GaN Light Emitting Diodes
Authors: Zhu Mingwei , Detchprohm Theeradetch , Xia Yong , Zhao Wei , Li Yufeng , Senawiratne Jayantha , You Shi , Liu Lianghong , Preble Edward A. , Hanser Drew , Wetzel Christian 
Published: April 2011

AbstractIn this study, we characterized the structural defects in blue and green GaInN/GaN LEDs grown on c-plane bulk GaN and sapphire substrates. Low density large V-defects with diameters around 600 nm were found in the blue LEDs on bulk GaN. They were initiated by edge-type threading dislocations (TDs) around the homoepitaxial growth interface. On the other hand, a high density 7×109 cm−2 of smaller V-defects with sidewalls on {1101} facets was observed in the active region of green LEDs on sapphire. Their diameter ranges from 150 to 200 nm. Misfit dislocations (MDs) generated in the quantum wells are found to initiate these V-defects. With optimizing the epitaxial growth conditions, the generation of MDs and their smaller V-defects was largely suppressed. As a result, the light output power improved by one order of magnitude. For green LEDs on bulk GaN, another unique type of defect was found in the active region: an inclined dislocation pair (IDP). In it a pair of dislocations propagate at a tilt angle of 18 to 23° from the [0001] growth direction towards <1100>. This defect seems to be a path of strain relief in the high indium composition quantum wells.
Mn- and Fe- doped GaN for spintronic applications
Authors: Malguth Enno , Hoffmann Axel , Werner Stefan , Kane Matthew H. , Ferguson Ian T. 
Published: April 2011

AbstractIn the context of ferromagnetic spin-coupling in dilute magnetic semiconductors, we present optical investigations on Mg co-doped GaMnN and Fe doped GaN. A complex luminescence feature occurring in Mg co-doped GaMnN around 1 eV was previously attributed to the internal 4T2(F)—4T1(F) transition of Mn4+ involved in different complexes. Selective excitation studies indicate the presence of at least three different complexes. Photoluminescence excitation spectra suggest that the internal Mn3+ transition may represent an excitation mechanism. Magneto photoluminescence spectra indicate equal g values for the ground and excited state. Low temperature infrared absorption spectra of Fe doped GaN allow to unambiguously establish the electronic structure of the Fe2+ center in GaN. Our results suggest that the Fe2+(5T2) state is stabilized against Jahn-Teller coupling by the reduced site-symmetry of the hexagonal lattice.
Two-Dimensional Growth Mode and Reduction of Dislocation Density in Nitride Layers
Authors: Pakula Krzysztof , Baranowski Jacek M. , Borysiuk Jolanta 
Published: April 2011

AbstractHeteroepitaxial two-dimensional (2D) and three-dimensional (3D) MOVPE growth of nitride layers on sapphire substrates using low temperature (LT) AlN nucleation layer are discussed. It is shown by Atomic Force Microscopy and Transmission Electron Microscopy that the 2D or 3D growth mode of successive AlGaN layers depends predominantly on the growth conditions of the underneath LT AlN nucleation layer.Modifications of growth conditions of LT AlN nucleation layer in respect of the growth in the conventional way, leads to a drastic change in properties of the successively grown at high temperature AlGaN layer. Main modification is connected with a drastic reduction of the growth rate of LT AlN nucleation layer at higher rector pressure. In this case the growth at high temperature starts evenly on the whole surface, retaining atomic flatness, and occurs in the 2D mode. Therefore, it is possible to grow even a very thin, continuous AlGaN layers directly on top of LT nucleation layer.The 2D growth mode leads to significant change in extended defect distribution. Edge dislocation density being close to 1010 cm−2, results in the effective relaxation of the internal stress. On the other hand mix dislocations density are close to 108 cm−2. All observed mix dislocations occur in pairs with dislocations with opposite sign. This suggests that all mix dislocations originate from dislocation half-loops. Both types of dislocations, edge and half loops can be effectively reduce in-situ, during the growth using annealing in the presence of silane. This process and precise control of the growth conditions leads to decreasing of mix dislocations density to 2·106 cm−2 and edge dislocations density to 5·108 cm−2.The newly developed two-dimensional growth mode of nitride layer opens up a new way to reduce strain, decrease density of dislocations and improvement of crystallographic properties.
Phase Transitions in Silicon-Carbon-Nitride Compounds
Authors: Kroll Peter , Gracia Jose , Riedel Ralf 
Published: April 2011

AbstractThe crystal structures of α-Si(NCN)2 and Si2N2(NCN) undergo phase transformations upon compression. A new modification of HP-Si(NCN)2 exhibits all Si atoms in octahedral coordination to N and may be achievable below 30 GPa. In Si2N2(NCN) we find partial increase of coordination for Si, C, and N atoms at about 60 GPa. In both cases, the carbodiimide moiety is the source for the internal reaction that lead to compactification of the structure at elevated pressures. We present 29Si NMR chemical shifts that may help to identify the new coordination environments.