bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thermodynamic Analysis and Purification for Source Materials in Sublimation Crystal Growth of Aluminum Nitride
Authors: Du Li , Edgar James 
Published: January 2010

AbstractSource material purification according to a thermodynamic analysis is reported for the sublimation crystal growth of aluminum nitride in an inert reactor. OAlOH is strongly favored over all other possible oxygen containing compounds in both the Al-O-H-N and Al-O-H-C-N systems, while Al2O, proved to be the most favorable oxygen containing gas species for Al-O-N system in previous study, become secondary favorable gas species. A low temperature (<1200 °C) treatment is effective in eliminating oxygen and hydrogen from the source powder. Carbon monoxide is another important oxygen containing gas species in the Al-O-H-C-N system, and is favored over Al2O at certain temperature and pressure. Carbothermal reduction with intentionally added carbon (graphite) can further reduce the oxygen concentration. Experiments show that high-temperature sintering minimizes the oxygen concentration and reduces the specific surface area of the source. With only 5.5% of mass loss, the purification produced a source with low O, H, and C concentrations of 0.018 wt%, 6ppm, and 0.006wt%.
X-ray Diffraction Study of InGaN/GaN Superlattice Implanted with Eu3+ Ions
Authors: Ebdah Mohammad Ahmad , Kordesch Martin E. , Anders Andre , Jadwisienczak Wojciech M. 
Published: January 2010

AbstractIn this work, europium implanted InGaN/GaN SL with a fixed well/barrier thickness ratio grown by metal-organic chemical-vapor deposition (MOCVD) on GaN/(0001) sapphire substrate were investigated. The as-grown and Eu ion implanted InGaN/GaN SLs were annealed at different temperatures ranging from 600°C to 950°C in nitrogen ambient. The quality of the SL interfaces in undoped and implanted structures has been investigated by X-ray diffraction (XRD) at room temperature. The characteristic satellite peaks of SLs were measured for the (0002) reflection up to the second order in the symmetric Bragg geometry. The XRD simulation spectrum of the as-grown SL agrees well with the experimental results. The simulation results show x=0.06 atomic percent the InGaN well sub-layers, with thicknesses of 2.4 and 3.3 nm for single InGaN well and GaN barrier, respectively. It was observed that annealing of the undoped SL does not significantly affect the interfacial quality of the superstructure, whereas, the Eu ion implanted InGaN/GaN SL undergo partial induced degradation. Annealing the implanted SLs shows a gradual improvement of the multilayer periodicity and a reduction of the induced degradation with increasing the annealing temperature as indicated by the XRD spectra.
Fluorescent Nanodiamonds: Effect of Surface Termination
Authors: Kratochvílová Irena , Taylor Andrew , Kovalenko Alexander , Fendrych Frantisek , Řezáčová Vladimira , Petrák Vaclav , Zalis Stanislav , Šebera Jakub , Nesládek Milos 
Published: January 2010

AbstractIt has been reported that physico-chemical properties of diamond surfaces are closely related to the surface chemisorbed species on the surface. Hydrogen chemisorption on a chemical vapor deposition grown diamond surface is well-known to be important for stabilizing diamond surface structures with sp3 hybridization. It has been suggested that an H-chemisorbed structure is necessary to provide a negative electron affinity condition on the diamond surfaces. Negative electron affinity condition could change to a positive electron affinity by oxidation of the H-chemisorbed diamond surfaces. Oxidized diamond surfaces usually show characteristics completely different from those of the H-chemisorbed diamond surfaces. The unique electron affinity condition, or the surface potential, is strongly related to the chemisorbed species on diamond surfaces. The relationship between the surface chemisorption structure and the surface electrical properties, such as the surface potential of the diamond, has been modelled using DFT based calculations.
Nanodiamond Particles in Electronic and Optical Applications
Authors: Shenderova Olga , Hens Suzanne Ciftan , Vlasov Igor , Borjanovic Vesna , McGuire Gary 
Published: January 2010

AbstractCurrent use of nanodiamond (ND) particles in electronic-related applications is mostly restricted to their role in seeding of substrates for growth of diamond films by chemical vapor deposition (CVD). While it is a niche application, nanometer-sized diamond particles are indispensable in this role. Seeding of substrates using a novel slurry of detonation nanodiamond particles in dimethylsulfoxide (DMSO) and methanol is one of the topics of this article. At the same time, optical applications of NDs, particularly development of photoluminescent NDs for biomedical applications is one of the most popular current research topics. In this paper perspectives for the use of detonation NDs and specifically the role of surface functionalization in imparting photoluminescent properties to detonation NDs as well as enhanced photoluminescence of proton irradiated ND-polydimethylsiloxane composites are discussed.
Simulations of CVD Diamond Film Growth Using a Simplified Monte Carlo Model
Authors: May Paul William , Harvey Jeremy N. , Allan Neil L. , Richley James C. , Mankelevich Yuri A. 
Published: January 2010

AbstractA simple 1-dimensional Monte Carlo (KMC) model has been developed to simulate the chemical vapour deposition (CVD) of a diamond (100) surface. The model considers adsorption, etching/desorption, lattice incorporation, and surface migration along and across the dimer rows. The reaction probabilities for these processes are re-evaluated in detail and their effects upon the predicted growth rates and morphology are described. We find that for standard CVD diamond conditions, etching of carbon species from the growing surface is negligible. Surface migration occurs rapidly, but is mostly limited to CH2 species oscillating rapidly back and forth between two adjacent radical sites. Despite the average number of migration hops being in the thousands, the average diffusion length for a surface species is <2 sites.
Optical Monitoring of Nanocrystalline Diamond with Reduced Non-diamond Contamination
Authors: Remes Zdenek , Kromka Alexander , Izak Tibor , Purkrt Adam , Vanecek Milan 
Published: January 2010

AbstractPreviously, the nanocrystalline grain boundaries were often contaminated by the “non-diamond phase” with the photo-ionization threshold at 0.8 eV. Here, we present the optical spectra of the NCD films grown on transparent substrates by the microwave plasma enhanced chemical vapor deposition (CVD) at a relatively low temperature below 600°C. The transmittance and reflectance spectra are useful to evaluate the film thickness, the surface roughness and the index of refraction. The direct measurement of the optical absorptance by the laser calorimetry and photothermal deflection spectroscopy (PDS) provides high sensitive methods to measure the weak optical absorption of thin films with rough surface. The optical measurements indicate the high optical transparency of our standard, nominally undoped 0.2-0.3 μm thick NCD film with low non-diamond content. However, the optical scattering is rather high in UV and needs to be reduced.
Capacitive Field-effect (bio-)chemical Sensors Based on Nanocrystalline Diamond Films
Authors: Bäcker Matthias , Poghossian Arshak , Abouzar Maryam H. , Wenmackers Sylvia , Janssens Stoffel D. , Haenen Ken , Wagner Patrick , Schöening Michael Josef 
Published: January 2010

AbstractCapacitive field-effect electrolyte-diamond-insulator-semiconductor (EDIS) structures with O-terminated nanocrystalline diamond (NCD) as sensitive gate material have been realized and investigated for the detection of pH, penicillin concentration, and layer-by-layer adsorption of polyelectrolytes. The surface oxidizing procedure of NCD thin films as well as the seeding and NCD growth process on a Si-SiO2 substrate have been improved to provide high pH-sensitive, non-porous thin films without damage of the underlying SiO2 layer and with a high coverage of O-terminated sites. The NCD surface topography, roughness, and coverage of the surface groups have been characterized by SEM, AFM and XPS methods. The EDIS sensors with O-terminated NCD film treated in oxidizing boiling mixture for 45 min show a pH sensitivity of about 50 mV/pH. The pH-sensitive properties of the NCD have been used to develop an EDIS-based penicillin biosensor with high sensitivity (65-70 mV/decade in the concentration range of 0.25-2.5 mM penicillin G) and low detection limit (5 μM). The results of label-free electrical detection of layer-by-layer adsorption of charged polyelectrolytes are presented, too.
Interaction of Hydrogen and Oxygen with Nanocrystalline Diamond Surfaces
Authors: Haensel Thomas , Ahmed Syed Imad-Uddin , Uhlig Jens , Koch Roland , Garrido José A. , Stutzmann Martin , Schaefer Juergen A. 
Published: January 2010

AbstractNanocrystalline diamond films (NCD) are strong candidates for applications in a wide variety of fields. An important concern in all these applications is to understand the properties of variously prepared NCD surfaces. This contribution is focussed on the surface science study of hydrogen and oxygen containing NCD films using X-ray photoelectron spectroscopy (XPS) as well as high resolution electron energy loss spectroscopy (HREELS). Previous studies have demonstrated that hydrogen, oxygen, and gases from the ambient environment as well as water can result in drastic surface changes affecting conductivity, wettability, tribological properties, etc. In this contribution we analyzed differently prepared NCD surfaces as a function of parameters such as the annealing temperature under ultrahigh vacuum conditions (UHV). We are able to identify the thermal stability of a number of species at the interface, which are related to different characteristics of C-H, C-OH, C=O, and C=C bonds. Furthermore, a formation of graphitic-like species appears at higher annealing temperatures. An atomic hydrogen treatment was also applied to the NCD surface to obtain further information about the surface composition.
Study of Growth Kinetics of Ultra-Long Carbon Nanotube Arrays through Wall Number Statistical Investigation
Authors: Cui Xinwei , Wei Weifeng , Chen Weixing 
Published: January 2010

AbstractThe unique properties of carbon nanotubes (CNTs) strongly depend on their structures. In this study, the growth kinetics of ultra-long multi-walled CNT (MWCNT) arrays by water-assisted chemical vapor deposition (WACVD) has been investigated based on the statistical studies of CNT wall number. It was found that the kinetics of MWCNT arrays in WACVD demonstrated a lengthening and thickening growth. In the linear lengthening stage, CNT wall number remains constant and catalysts preserve the activity; while in the thickening stage, CNTs thicken substantially through the gas phase-induced thickening process and catalysts start to deactivate. The effects of ethylene and hydrogen flow rates on the MWCNT array growth have also been studied. It was found that by changing ethylene flow rate, different linear lengthening stages corresponding to different CNT wall numbers could be obtained. These findings provide experimental solutions to fabrication MWCNT arrays with both selective heights and controllable wall numbers by WACVD.
Electron Beam Induced Two-State Noise in Carbon Nanotubes
Authors: Chan Jack , Burke Brian G. , Hu Chong , Campbell Joe , Harriott Lloyd , Williams Keith A. 
Published: January 2010

AbstractDiscrete current switching is induced in carbon nanotubes by electron beam irradiation. Switching amplitudes of 3% to 6% are observed at room temperature. Switching is created by electron beam exposure with dosage as low as 1000 pC/cm. Relative switching amplitude remains constant as the bias voltage varies, suggesting that current fluctuation is dominated by mobility fluctuation. Changes in the noise power spectral density following electron beam exposure will be discussed.
Comparing Field Emission Stability of Lithography-free, Modified Multi-walled Carbon Nanotubes
Authors: Pandey Archana , Prasad Abhishek , Moscatello Jason , Yap Yoke Khin 
Published: January 2010

AbstractField emission from carbon nanotubes (CNTs) has been known for more than a decade but there is no commercialized product available in the market. Apparently, we need to improve our basics understanding on stable field emission from CNTs. Here we compared the field emission properties of as grown vertically-aligned multi-walled carbon nanotubes (MWCNTs) to two types of modified MWCNTs: 1) Conical bundles of opened-tip MWCNTs, and 2) Opened-tip MWCNTs embedded in poly-methyl methacrylate (PMMA). We found that both types of modified MWCNTs have lower emission thresholds and better emission stability than the as grown samples. Among these modified samples, MCNTs embedded in PMMA has lower emission thresholds and better emission stability. We attributed these improvements to the filling of spacing between MWCNTs with PMMA that has higher dielectric constant than vacuum.
Photocatalytic Segmented Nanowires and Single-step Iron Oxide Nanotube Synthesis: Templated Electrodeposition as all-round Tool
Authors: Maas Michiel G. , Rodijk Eddy J.B. , Maijenburg Wouter , ten Elshof Johan E , Blank Dave H.A. 
Published: January 2010

AbstractTemplated electrodeposition was used to synthesize silver-zinc oxide nanowires and iron oxide (Fe2O3) nanotubes in polycarbonate track etched (PCTE) membranes. Metal/oxide segmented nanowires were made to produce hydrogen gas from a water/methanol mixture under ultraviolet irradiation. It was observed that gas production increased during irradiation.
Iron oxide nanotubes were synthesized via a gel synthesis route, avoiding clogging of the membrane pores during growth. The nanotubes formed without thermal after-treatment. Transmission electron microscopy (TEM) analysis and selected area electron diffraction (SAED) revealed a completely amorphous iron oxide structure. By demonstrating the synthesis of photocatalytically active segmented nanowire and nanotubes without post-treatment steps, templated electrodeposition can be a versatile and low cost tool for nanowires with designed functionality or fast nanotube synthesis.
Effect of hydrogen plasma treatment on the luminescence and photoconductive properties of ZnO nanowires
Authors: Li Yanbo , Uchino Ryohei , Tokizono Takero , Paulsen Alexander , Zhong Miao , Shuzo Masaki , Yamada Ichiro , Delaunay Jean-Jacques 
Published: January 2010

AbstractZnO nanowires with strong green emission synthesized by chemical vapor deposition were treated using hydrogen plasma. The effect of hydrogen plasma treatment was studied by means of photoluminescence and photoconductivity. A strong passivation of the green emission and a significant enhancement of the near band edge emission were found after the hydrogen plasma treatment. The conductivity of the nanowires in dark was increased by more than 3 orders of magnitude. The photoconductivity also increased after the hydrogen plasma treatment. The observed changes in the luminescence and photoconductive properties of the ZnO nanowires were likely caused by hydrogen atoms occupying both oxygen vacancies and interstitial sites.
FIB-deposited carbon-based superconducting nanowires with Tc ˜ 7 K
Authors: Dhakal Pashupati , McMahon Gregory , Norris Liam , Oh Jeong Il , Naughton Michael J. 
Published: January 2010

AbstractWe have fabricated carbon-containing nanowires by a gallium focused ion beam-induced deposition process from the precursor phenanthrene, C14H10. The electrical conductivity of the nanowires is only weakly temperature dependent below 300K, and reveals a superconducting state below Tc ˜ 7 K. We have measured the temperature dependence of the resistive upper critical field Hc2(T), and from those data, estimate the zero temperature critical field and coherence length to be 8.8 T and 6.1 nm, respectively. The Tc of this material is approximately 40% higher than that in any other FIB/direct write nanowire, such as those based on W(Ga), and thus offers the possibility of fabricating superconducting direct-write nanostructures that function at liquid helium temperature.
Spectrophotometric Investigation on the Growth Mechanism of a Single Tapered CuO Nanowire
Authors: Chatterjee Anindita , Huang C-Y , Liu S-B , Wu S-Y , Cheng Chia-Liang 
Published: January 2010

AbstractIn this study, well separated tapered CuO nanowires have been synthesized on copper grid using an easy and cost effective thermal oxidation method. A set of spectroscopic investigations have been performed on one single tapered CuO nanowire using Energy Dispersive X-ray, confocal Raman and confocal Photoluminescence spectroscopy to get insight into the mechanism of growth of the nanowires. Energy Dispersive X-ray studies reveal crystallization process of CuO nanowires occur from Cu/Cu2O mixed phase state to pure CuO structure. Raman measurements indicate a little sharpening of the Raman peaks with increasing growth temperature of the nanowires starting from 400°C to 600°C. Photoluminescence studies were carried out by mapping along the length of the nanowire to investigate the growth as well as optical properties of a single tapered CuO nanowire. As the diameter of the single tapered CuO nanowire decreases, the green emission of the nanowire gradually shifts towards the higher energy side. A steady blue shift of 20 nm of the photoluminescence peak has been attributed to the nanosize effect of the tapered nanowire along the length and enhanced surface defects.
Synthesize of Metal-semiconductor Segmented Nanowire by Electrodeposition
Authors: Eom HyeonJin , Yoo Bongyoung 
Published: January 2010

AbstractRecently, thermoelectric (TE) is ignited by enhancement of nano-science and engineering that uncovers the possibility of increasing of figure of merit (ZT). As a candidate for thermoelectric materials, metal could not be considered because of their high thermal conductivity. However, according to other research, it is feasible to decrease thermal conductivity of also metal without much degradation of the electrical conductivity, which strongly implies that nanoscale metal can be utilized to improve thermoelectric properties of devices, especially power factor. Semiconductor-semiconductor superlattice nanowire structure has been studied as one of the best candidates for thermoelectric devices, because of their photon scattering characteristics at the interfaces. In this research, instead of semiconductor-semiconductor superlattice structure, metal-semiconductor superlattice structure was synthesized, and its microstructure and electrical properties are investigated. With this structure, improvement of electrical conductivity as well as degradation of thermal conductivity with phonon scattering would be anticipated. Metal-semiconductor superlattice nanowires were acquired with electrochemical displacement method, which can exchange the material which has low reduction potential with more noble materials in aqueous electrolyte. To achieve this, Ni-Ag superlattice structure was firstly prepared as metal-metal superlattice structure. The electrolyte for the electrodeposition of Ni-Ag segmented nanowries was consisted of 0.3 mol/L C6H5Na3O7, 0.7mol/L NiSO4 and AgNO3. Electrodeposition was performed galvanostatically in two electrode cell configuration with anodized aluminum oxide(AAO) template. Cu layer was deposited at the one side of AAO template as a working electrode, platinum coated titanium stripe as counter electrode. The composition of electrodeposits could be controlled by applied potential which is directly related the applied current density. Ni-rich phase could be obtained when the applied current density was over 10mA/cm2 and Ag-rich phase at 0.5mA/cm2. After acquiring Ni-Ag segmented nanowire structure, we synthesized the metal-semiconductor segemented nanowries (Ag-BiTe segmented nanowire) by using galvanic-displacement method. Because standard reduction potential energy of nickel is more negative (-0.25V) than that of BiTe in Bi ion and Te ion contained bath, it is possible to make displacement of Ni with BiTe using galvanic displacement. The morphology was investigated by SEM and composition profile was observed by EDS. In conclusion, nanoscale metal-semiconductor segmented nanowires were synthesized by electrodeposition and electrochemical displacement method. Their structural characteristics and electrical properties were investigated to understand the possibility of this segmented nanowires as a thermelectrical materials.
Synthesis and Structural Characterization of Ultra-thin Flexible Au Nanowires
Authors: Kisner Alexandre , Heggen Marc , Tillmann Karsten , Mourzina Yulia , Offenhäeusser Andreas 
Published: January 2010

AbstractAu nanowires (AuNWs) were produced by electroless reduction of HAuCl4 in a micellar structure formed by oleylamine and investigated by means of high-resolution transmission electron microscopy (HRTEM). Micrometer long ultra-thin flexible AuNWs with 1—2 nm diameter and AuNWs with about 12 nm diameter and a few hundred nm length were produced. Their extremities show a characteristic bulging. In contradiction with previous work, the bodies of the 12 nm nanowires are defect-free along the axial direction, their extremities, however, show the presence of twin boundaries. Ultra-thin AuNWs were often found as bundles presenting lengths of few micrometers. Although they are stable in solution for months, they were found to be quite sensitive to electron beam irradiation during HRTEM experiments, with a tendency to break up into face centered cubic (fcc) Au droplets. It is proposed that the micellar configuration of oleylamine plays a fundamental role in the atomic arrangement of nanowires. Finally, we anticipate our results to be a starting point for a more realistic experimental investigation of surface effects on the mechanical properties of ultra-thin nanowires with high aspect ratio, which have been only widely exploited theoretically.
Electrodeposited Metallic Nanowires as a Scanning Probe Tip
Authors: Motoyama Munekazu , Prinz Fritz B. 
Published: January 2010

AbstractThis paper describes lateral deformations of electrodeposited Ni nanowires as an atomic force microscope (AFM) probe tip. The maximum end deflections for nanowires to break the elasticity, which beam mechanics indicates, were applicable to our observed results.
Optically Controlled Nanomagnets
Authors: Mackowski Sebastian , Gurung Tak , Karczewski Grzegorz , Jackson Howard E , Smith Leigh 
Published: January 2010

AbstractWe report on single dot photoluminescence imaging and spectroscopy at B=0T on magnetically doped CdMnTe self-assembled quantum dots with average Mn concentration of several percent. Quasi-resonant excitation with circularly polarized laser leads to formation of magnetic polarons with magnetization induced by the laser light. In this case all quantum dots are polarized in the same direction. In contrast, when the dots are populated using above the barrier excitation, with randomly polarized excitons, the resultant magnetization is random and varies from dot to dot. These experiments demonstrate a way to control the magnetization of magnetically doped quantum dots by means of light excitation. In addition, they point towards extremely long spin memory times in these structures, reaching hundreds of microseconds, making CdMnTe quantum dots promising candidates for local magnetic field sources on the nanoscale.