bluuebunny/crossref_metadata_2025_split huggingface dataset:
Raman spectroscopy of self-assembled InAs quantum dots in wide-bandgap matrices of AlAs and aluminium oxide
Authors: Tenne D. A. , Milekhin A. G. , Bakarov A. K. , Bajutova O. R. , Haisler V. A. , Toropov A. I. , Schulze S. , Zahn D. R. T. 
Published: April 2011

ABSTRACTVibrational properties of self-assembled InAs quantum dots (QD’s) embedded in AlAs and aluminium oxide were studied by Raman spectroscopy. The InAs/AlAs QD structures were grown by molecular beam epitaxy on GaAs (001) substrates. The following main features of the phonon spectra of InAs/AlAs QD nanostructures were observed: 1) asymmetric lines of QD LO phonons affected by strain, confinement and size inhomogeneity of QD’s; 2) confined phonons of InAs wetting layer (WL); 3) two bands of interface phonons in the AlAs frequency region, attributed to modes associated with the planar interface WL/AlAs matrix and the three-dimensional QD/matrix interface; 4) doublets of folded acoustic phonons caused by periodicity in the multilayer QD structures. The influence of growth temperature, varied from 420 to 550°C, on the morphology of QD’s was investigated. QD’s grown at 420°C are found to have the smallest size. Increasing the temperature up to 480°C leads to the formation of larger InAs islands and improved size homogeneity. Further temperature elevation (above 500°C) causes partial re-evaporation of InAs leading to a decrease of QD size and density, and, finally, their complete disappearance. InAs QD’s embedded in aluminium oxide were fabricated by selective oxidation of the AlAs matrix in self-assembled InAs/AlAs QD’s. Micro-Raman spectroscopy data show that depending on oxidation conditions (humidity, temperature) InAs QD’s in an oxide matrix can be even more strained than before oxidation, or become fully relaxed. At the boundaries of oxidized/non-oxidized areas the presence of amorphous and crystalline As clusters is evident.
Photoluminescence within Crystalline-Si/SiO2 Single Quantum Wells.
Authors: Lockwood D. J. , Dharma-wardana M. W. C. , Lu Z. H. , Grozea D. H. , Carrier P. , Lewis Laurent J. 
Published: April 2011

ABSTRACTUltrathin single quantum wells of crystalline silicon (c-Si) confined by SiO2 have been prepared by chemical and thermal processing of silicon-on-insulator wafers. The photoluminescence (PL) produced by these nanometer-thick single wells contains two bands: one exhibits a peak energy of ∼1.8 eV, while the second increases rapidly in peak energy with decreasing c-Si layer thickness. Comparison with theories based on self-consistent first-principles calculations shows that the increase in PL peak energy of the second band is consistent with that predicted for the c-Si energy gap of such wells. It also agrees with the measured band gap variation. The ∼1.8 eV PL band is attributed to the recombination of electron-hole pairs confined at the c-Si/SiO2 interface.
A New Synthetic Route to Alkyl Terminated Silicon Nanoparticles.
Authors: Pettigrew Katherine A. , Power Philip P. , Kauzlarich Susan M. 
Published: April 2011

ABSTRACTThis paper describes the preparation of alkyl terminated silicon nanoparticles that are air and moisture stable by the oxidation of magnesium silicide with bromine and then the subsequent termination with an alkyl Grignard reagent. The nanoparticles have been characterized by transmission electron microscopy (TEM), high-resolution TEM (HRTEM), energy-dispersive X-ray spectroscopy (EDS), Fourier transform infrared (FTIR) spectroscopy, and fluorescence spectroscopy.
New Pairs of Inks and Papers for Photolithography, Microcontact Printing, and Scanning Probe Nanolithography
Authors: Porter Lon A. , Choi Hee Cheul , Schmeltzer J. M. , Ribbe Alexander E. , Buriak Jillian M. 
Published: April 2011

ABSTRACTCurrently, there is considerable interest in producing patterned metallic structures with reduced dimensions for use in technologies such as ultra large scale integration (ULSI) device fabrication, nanoelectromechanical systems (NEMS), and arrayed nanosensors, without sacrificing throughput or cost effectiveness. Research in our laboratory has focused on the preparation of precious metal thin films on semiconductor substrates via electroless deposition. This method provides for the facile interfacing of metal nanoparticles with a group (IV) and III-IV compound semiconductor surfaces. Morphologically complex films composed of gold, platinum, and palladium nanoparticles have been prepared as a result of the immersion of germanium and gallium arsenide substrates into dilute, aqueous solutions of tetrachloraurate (III), tetrachloroplatinate (II), and tetrachloropalladate (II), respectively. Continuous metallic films form spontaneously under ambient conditions, in the absence of a fluoride source or an externally applied current. This facile electroless deposition methodology provides an alternative to complex and expensive vacuum methods of metallization, yet allows for the preparation of both thin and thick nanostructured films with control over surface morphology and deposition rate. Furthermore, precious metal films prepared in this way exhibit excellent adhesion to the underlying semiconductor substrate. The resultant films were characterized utilizing scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and scanning probe microscopy (SPM). In order to apply this novel metallization method toward the development of useful technologies, patterning utilizing photolithography, microcontact printing (μCP), and scanning probe nanolithography (SPN) has been demonstrated.
Sol-gel Template Synthesis and Liquid CO2 Developed TiO2/CdS Composite Nanowire Arrays
Authors: Cheng Bin , Murray Clarence W. , Samulski Edward T. 
Published: April 2011

ABSTRACTTiO2/CdS composite nanowire (∼ 200 nm diameter and ∼ 50 μm length) arrays were successfully prepared by the sol-gel template method. An anticipated good nanowire arrays was obtained by using liquid or supercritical CO2 to develop the target materials in purification process. The morphology, crystallinity, and composition of the product was characterized by SEM, XRD, and EDX.
Preparation and Characterization of Fine barium carbonate Particles
Authors: Lihong Su. , Shenru Qiao. , Jun Xiao. , ying Huang. , Aibo Zhang. , qiuyu Zhang. 
Published: April 2011

ABSTRACTAs a starting material to produce BaTiO3 ceramic, BaCO3 fine powders (<1 μm in diameter) are required. In this paper, how to transform 2–3μm length viraulate BaCO3 microlite into 0.2–0.8μm globose particle is discussed. The factors that affect aggregation and dispersion in fine powder are experienced. Special equipment is introduced to this process. The particle diameter is determined by the SEM micrograph. The whole process is a simple method.
Preparation and Photoactive Characterization of Tube-shaped Al-doped ZnO Ceramics.
Authors: Fujishiro Yoshinobu , Awano M. , Kanzaki S. 
Published: April 2011

ABSTRUCT:Tubular Al-doped ZnO particles were prepared by homogeneous precipitation in the mixed solutions of Al(NO3)2, Zn(NO3)2, sodium dodecyl sulfate (SDS) surfactant and urea. At the molar ratio of Metal ions(Mt) : SDS : urea : H2O is 1 : 2 : 20 : 60, tubular products formed by heating at 80°C for 12 h. Plate like ZnO particles were obtained at Mt : SDS : urea : H2O = 1 : 2 : 10 : 60 or 1 : 1 : 20 : 60. The diameter of typical ZnO tube is ca.100 nm, and the length of tube is about 600nm (aspect ratio = 6). The relative surface area of tubular Al-doped ZnO is ca. 40.2 m2/g. The photo-decomposition rate of NO3- ions using tubular Al-doped ZnO particles was higher than standard TiO2 photo-catalysts (P-25) by irradiation >290nm light in 10mM KNO3-10vol%EtOH solutions at 30°C. The obtained materials showed DC conductive properties as compacted substrate by sintered at 400°C.
Electroless Deposition and Patterning of Morphologically Complex Precious Metal Films on Semiconductor Surfaces
Authors: Porter Lon A. , Choi Hee Cheul , Ribbe Alexander E. , Buriak Jillian M. 
Published: April 2011

ABSTRACTPrecious metals are choice materials for a myriad of applications due their high electrical conductivity, resistance to corrosion, and ligand binding specificity. Indispensable in modern electronics fabrication, precious metals also enjoy widespread use as catalysts, support substrates, and sensor elements. Recent progress towards metallization on diminishing size regimes has imposed increasingly stringent demands upon thin film preparation methodologies. Metallization techniques employed in ultra large scale integration (ULSI) device fabrication, nanoelectromechanical systems (NEMS), and arrayed nanosensors will require unparalleled control of surface morphology, deposition rate, and substrate adhesion without sacrificing throughput or cost effectiveness. Furthermore, precious metal films of this type are essential for fundamental investigations aimed at elucidating the intricate nature of interfacial topics ranging from self-assembled monolayers (SAMs) to heterogeneous catalysis. In contrast to complex and expensive vacuum methods of metallization, research in our laboratory has focused on the preparation of precious metal thin films on semiconductor substrates via electroless deposition. Thin and thick films of gold, platinum, and palladium nanoparticles have been prepared as a result of the immersion of germanium and gallium arsenide substrates into dilute, aqueous solutions of tetrachloraurate (III), tetrachloroplatinate (II), and tetrachloropalladate (II), respectively. This methodology yields nanostructured precious metal films with control over surface morphology and deposition rate. Moreover, metal films prepared in this manner exhibit excellent adhesion to the underlying semiconductor substrate. The resultant films were characterized utilizing scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and scanning probe microscopy (SPM). This method provides for the facile interfacing of metal nanostructures with group (IV) and III-IV compound semiconductor surfaces.
Electrophoretic Deposition of CdSe Nanocrystal Films on Conducting Electrodes
Authors: Islam Mohammad A. , Xia Yuqi , Kraines Benjamin J. , Herman Irving P. 
Published: April 2011

ABSTRACTA dc electric field is used to attract thermally charged CdSe nanocrystals in solution to rapidly form large-area, micron-thick films of equal thickness on both electrodes. A pair of Au-on-Si or conducting ITO-on-glass electrodes was submerged in the nanoparticle solution and a dc voltage was applied in a dark room. Uniform, robust, very smooth, and apparently identical films formed on both electrodes. Photoluminescence and absorption of the films showed that they are indeed made of dense arrays of individual nanocrystals. The deposition implies there are both positively and negatively thermally charged dots in solution. These high quality dense arrays of the nanoparticles could be useful in several applications.
Anisotropy in the Phonon Dispersion Relations of Graphite and Carbon Nanotubes Measured by Raman Spectroscopy
Authors: Samsonidze Georgii G. , Saito Riichiro , Jorio Ado , Souza Filho Antonio G. , Grüneis Alexander , Pimenta Marcos A. , Dresselhaus Gene , Dresselhaus Mildred S. 
Published: April 2011

ABSTRACTThe possible semiconducting device use of single wall carbon nanotubes (SWNTs) requires a technique for the determination of the exact structure of the nanotubes assembled in the device configuration. Raman spectroscopy has been established as a precise and non-destructive tool for the characterization of graphitic nanostructures. Double resonance theory, which is used to explain the dispersive nature of the Raman bands, has attracted much attention for its potential use for the characterization of the electronic and phonon spectra of these nanostructures. Dispersive features in the Raman spectra of low dimensional graphitic materials, such as carbon nanotubes, can be used to measure directly the anisotropy, or the trigonal warping effect, in the phonon dispersion relations about the hexagonal corner of the Brillouin zone (BZ) of graphite.
TEM and PL Study of FeSi2 Precipitates Formed in Si by Iron Implantation Using a Metal Vapor Vacuum Arc Ion Source
Authors: Gao Y. , Cheung W.Y. , Wong S.P. , Shao G. , Homewood K.P. 
Published: April 2011

ABSTRACTIn this work, FeSi2 precipitates were formed in Si by iron implantation using a metal vapor vacuum arc ion source. Transmission electron microscopy (TEM) was used to determine the crystal and defect structures of the implanted samples. It was found that the implantation temperature played an important role on the shape and phase formation of the FeSi2 precipitates, as well as the formation and distribution of the dislocation loops. When implantation was performed at an elevated temperature of about 380°C, there were a lot of dislocation loops formed and only β-FeSi2 precipitates were observed. When implanted at a low temperature of about -100°C followed by a dual step annealing process, the samples were found to be free of dislocation loops, and γ-FeSi2 and β-FeSi2 precipitates coexisting and coherent with the silicon substrate were observed. Photoluminescence (PL) spectra of different line shapes from these implanted samples were observed. By combining the PL and TEM results, the origins of the PL peaks in different samples could be distinguished and identified to be from β-FeSi2 precipitates or from crystal defects in the samples.
Electroluminescent devices based on Er-doped Si nanoclusters
Authors: Priolo F. , Iacona F. , Pacifici D. , Irrera A. , Miritello M. , Franzò G. , Sanfilippo D. , Di G. , Fallica P.G. 
Published: April 2011

ABSTRACTThe electroluminescence (EL) properties of Er-doped Si nanoclusters (nc) embedded in metal-oxide-semiconductor devices are investigated. It is shown that, due to the presence of Si nc dispersed in the SiO2matrix, an efficient carrier injection occurs and Er is excited producing an intense 1.54 μm room temperature luminescence. The EL properties as a function of the current density, temperature and time have been studied in details, elucidating the radiative and non-radiative de-excitation properties of the system. We have also estimated the excitation cross section for Er under electrical pumping finding a value of −1×10 cm. This value is two orders of magnitude higher than the effective excitation cross section of Er ions through Si nc under optical pumping, and quantum efficiencies of ∼1% are obtained at room temperature in these devices. These data will be presented and the impact on future applications discussed.
Resist Requirements and Limitations for Nanoscale Electron-Beam Patterning
Authors: Alexander Liddle J. , Gallatin Gregg M. , Ocola Leonidas E. 
Published: April 2011

ABSTRACTElectron beam lithography still represents the most effective way to pattern materials at the nanoscale, especially in the case of structures, which are not indefinitely repeating a simple motif. The success of e-beam lithography depends on the availability of suitable resists. There is a substantial variety of resist materials, from PMMA to calixarenes, to choose from to achieve high resolution in electron-beam lithography. However, these materials suffer from the limitation of poor sensitivity and poor contrast.In both direct-write and projection e-beam systems the maximum beam current for a given resolution is limited by space-charge effects. In order to make the most efficient use of the available current, the resist must be as sensitive as possible. This leads, naturally, to the use of chemically amplified (CA) systems. Unfortunately, in the quest for ever smaller feature sizes and higher throughputs, even chemically amplified materials are limited: ultimately, sensitivity and resolution are not independent. Current resists already operate in the regime of < 1 electron/nm2. In this situation detailed models are the only way to understand material performance and limits.Resist requirements, including sensitivity, etch selectivity, environmental stability, outgassing, and line-edge roughness as they pertain to, high-voltage (100 kV) direct write and projection electron-beam exposure systems are described. Experimental results obtained on CA resists in the SCALPEL® exposure system are presented and the fundamental sensitivity limits of CA and conventional materials in terms of shot-noise and resolution limits in terms of electron-beam solid interactions are discussed.
New Processing Techniques for the Creation of Micro-Opto-Mechanical Machines and Photonic Devices Embedded in Glass
Authors: Abraham Meg , Fuqua Peter , Taylor David P. , Hansen William W. , Helvajian Henry , Presser Nathan , Livingston Frank , Lumondiere Stephen La 
Published: April 2011

ABSTRACTThe use of lasers to create intricate three-dimensional and buried structures [1] in photostructural glass has been well demonstrated at The Aerospace Corporation over the past four years. In these instances the glass used (Foturan™, made by the Schott Group) forms a silver nucleation sites on exposure to intense UV laser light via a two-photon process. Subsequent annealing causes a localized crystal growth to form a meta-silicate phase which can be etched in dilute hydrofluoric acid at rates of 20 to 50 times that of the unprocessed glass. We are now in the process of experimenting with another formulation of photosensitive glass, also pioneered by Corning Glass Works, that behaves differently during the bake process. In the second case, a photoexposure and bake process creates a silver-halide crystal and forms an adjacent void in the glass. A second photoexposure and bake allows for the migration of more silver into the void creating patterned formations of silver nano-wires [2]. Recent experiments with this type of glass have shown that the manipulation of the size and density of the embedded nano-wires as well as the overall pattern of the clusters can be controlled using direct-write exposure to laser processing.
Optical Nanolithography Using Evanescent Fields
Authors: Blaikie Richard J. , McNab Sharee J. , Alkaisi Maan M. 
Published: April 2011

ABSTRACTIn the optical near field region the well understood resolution limits for projection optical lithography can be overcome. This offers the possibility of performing optical nanolithography without the need to use expensive, deep ultraviolet light sources. For exposures that utilise evanescent fields close to metallic amplitude masks sub-diffraction-limited resolution has been achieved experimentally, and the theoretical resolution limits have been explored using vector electromagnetic near field simulations. Resolution down to 20nm using exposure wavelengths greater than 400nm is predicted. It is also found that the exposure wavelength is of secondary importance in this regime, and that the properties of the mask are much more significant. Scaling to smaller feature sizes requires better resolution and control during mask manufacture, rather than the conventional (and costly) approach of driving the exposure wavelength deeper and deeper into the ultraviolet. Near field interference effects have also been explored, and the characteristics of spatial frequency doubling using Evanescent Interferometric Lithography (EIL) have been determined by simulation. Sub-diffraction-limited resolution can be achieved with increased exposure intensity compared with conventional interferometric lithography. The tradeoff is against the depth of field in the resultant interference pattern. Finally, the use of negative refraction and surface plasmons have been investigated to improve further the resolution in the evanescent near field, and to produce novel, three dimensional near field patterns.
Wet-Process Molecular Planting in A Specific Site on Silicon with Si-C Covalent Bonds
Authors: Tada Hirokazu , Ara Masato , Tanaka Shoji 
Published: April 2011

ABSTRACTAlkyl monolayers anchored covalently on silicon were prepared through the reaction between 1-alkenes and hydrogen-terminated silicon (111) surfaces. The 2D-patterning of the surface was done by local oxidation with an atomic force microscope (AFM) and 3D-molecular assemblies were fabricated by immobilization of molecules in a specific site of the patterned surface. The surfaces were anodized with a contact-mode AFM by applying a positive bias voltage to the surface with respect to the platinum-coated cantilever under ambient conditions, which resulted in nanometer-scale oxidation of surfaces. The anodized areas were etched and terminated with hydrogen atoms by NH4F solution, in which we could immobilize various molecules having C=C bonds. We put arylamine molecules to which organic dyes such as fluoroscein were anchored. The intensity of luminescence varied depending on dopant concentration of substrates. Luminescence was very weak on highly-doped silicon possibly due to effective energy transfer from dyes to substrates. The method demonstrated is one of the promising ways to fabricate 3D-assemblies of molecular-scale electronic devices with a stable interface on silicon.
FIB-assisted Pt Deposition for Carbon Nanotube Integration and 3-D Nanoengineering
Authors: Dovidenko K. , Rullan J. , Moore R. , Dunn K. A. , Geer R. E. , Heuchling F. 
Published: April 2011

ABSTRACTIn this study, the Focused Ion Beam (FIB) instrument has been used for carbon nanotubes integration and nanoegineering studies. Results of thorough investigation (electrical, structural and chemical) of ultra-thin Pt contact lines and pads fabricated by the FIB, along with evaluation of nanomodification of the carbon nanotubes under the Ga+ ion beam and during Pt deposition are presented. The initial stages of FIB-assisted Pt deposition on multi-wall nanotubes are studied by transmission electron microscopy (TEM). The FIB parameters are optimized to provide non-destructive imaging and controllable Pt deposition with minimal damage on the nanotubes. We have demonstrated effective use of FIB-fabricated Pt pads as means of attaching the nanotubes to the substrate for atomic force and ultrasonic force microscopy studies.
Interband Transitions in GaInNAs/GaAs Single Quantum Wells
Authors: Manasreh M. O. , Friedman D. J. , Ma W. Q. , Workman C. L. , George C. E. , Salamo G. J. 
Published: April 2011

ABSTRACTPhotoluminescence (PL) spectra of interband transitions in GaInNAs/GaAs single quantum wells grown by metalorganic chemical vapor deposition technique on semi-insulating GaAs substrates were measured at 77 K for several samples grown with different In composition and dimethylhydrazine (DMH)/III ratios. The results show that the PL intensity increases as the In mole fraction is increased from 0 to 25%, but the PL intensity is degraded for samples with an In mole fraction of 30% or higher. The peak position energies of the PL spectra were investigated as a function of the DMH/III ratio. Thermal annealing effect induced a blue-shift in the PL spectra peak position energy in samples grown with high DMH/III ratio.
Properties of GaAsSb QW Heterostructures Having Various Barrier Materials Grown by Metalorganic Chemical Vapor Deposition
Authors: Noh Min Soo , Ryou Jae Hyun , Chang Ying-Lan , Weissman Robert , Dupuis Russell D. 
Published: April 2011

ABSTRACTPseudomorphic GaAs1-xSbx quantum-well (QW) structures grown on GaAs substrates by metalorganic chemical vapor deposition (MOCVD) have been studied with various barrier materials to investigate the energy band lineup. To determine the band lineup of these structures, we have performed low-temperature current-dependent cathodoluminescence (LT-CL) measurements at 10K. For the structure with GaAs barriers, the data show strong evidence of Type-II staggered band lineup, which means that holes are confined in the valence band heavy-hole level of the GaAs1-xSbx quantum well and electrons are confined in the conduction band of the GaAs barrier.For the InGaP barriers, however, we observed only one peak that is related to transitions of a Type-I band lineup. From the LT-CL results, we find that the valence-band discontinuity ratio (Qv) between the GaAs0.73Sb0.27 double quantum wells (DQWs) and the GaAs barriers is ∼1.20. Furthermore, to improve the carrier confinement, we propose that InGaP barriers provide a Type-I band lineup with the GaAsSb QW.