bluuebunny/crossref_metadata_2025_split huggingface dataset:
Room Temperature Emission from Erbium Nanoparticles Embedded in a Silicon Matrix
Authors: Thilderkvist A. , Michel J. , Ngiam S.-T. , Kimerling L. C. , Kolenbrander K. D. 
Published: April 2011

AbstractStrong room temperature photoluminescence emission from thin films of Er nanoparticles embedded in a matrix of silicon is reported. The Er nanoparticles were produced by a pulsed laser ablation supersonic expansion technique. After a heat treatment at 500°C in an Ar-atmosphere, intense Er-related luminescence appears at λ = 1.54 gim, characteristic of intra-4f emission from Er3÷. Only a 50% reduction in photoluminescence intensity is observed as the temperature increases from 4 K to 300 K. A photocarrier mediated process is responsible for the excitation of the optically active Er-centers.
Investigation of Local Structures Around Luminescent Centers in Doped Nanocrystal Phosphors
Authors: Soo Y. L. , Huang S. W. , Ming Z. H. , Kao Y. H. , Goldburt E. , Hodel R. , Kulkarni B. , Bhargava R. 
Published: April 2011

AbstractExtended x-ray absorption fine structure (EXAFS) technique has been employed to investigate the local structures around luminescent centers in nanocrystals of Mn-doped ZnS and Tb-doped Y2O3. Size-dependent local structural changes around Mn luminescent centers have been found in Mn-doped nanocrystals of ZnS by using Mn K-edge EXAFS. Local structures around Tb investigated by Tb Li-edge EXAFS also show substantial differences between bulk and nanocrystal samples. This structural information is useful for understanding the novel optical properties of doped nanocrystals.
Persistent Spectral Hole-Burning of CuCI Semiconductor Quantum dots
Authors: Okamoto Shinji , Masumoto Yasuaki 
Published: April 2011

AbstractPersistent spectral hole-burning (PSHB) phenomena of semiconductor quantum dots enable to perform the precise, high-resolution spectroscopy for the quantum dots of a certain size. We succeeded in the observation of the higher-excited states of excitons in CuCI quantum dots by means of the PSHB phenomena. Moreover, the exciton-state-splitting is observed and in agreement with the theoretical results on the assumption of platelet quantumdots.
Stress Effects in 2d Arsenic Diffusion in Silicon
Authors: Rao V. , Zagozdzon-Wosik W. 
Published: April 2011

AbstractProximity rapid thermal diffusion (RTD) using arsenic has been used for doping high aspect ratio trench capacitors which may be used in high density dynamic memories. Nonuniformity of doping has been observed in SEM analyses at the trench comers after preferential etching used for junction delineation. Severe thinning was seen at the bottom comers of the junctions produced at low temperatures for long times (90 sec). This non- uniformity was alleviated at high diffusion temperatures for short time resulting in very uniform junctions. We modeled diffusion processes for trench doping using a process simulator, TSUPREM-IV. Default program data produced large discrepancies with experimental results and a new set of parameters was derived. The stress model in the oxide growth was incorporated in our calculations of the diffusion profiles to simulate formation of the dopant glass and obtain match with the experimental results.
Combine Spectroscopic Ellipsometry and Grazing X-ray Reflectance for Fine Characterization of Complex Epitaxial Structures
Authors: Boher P. , Stehle J. L. 
Published: April 2011

AbstractSpectroscopic Ellipsometry (SE) and Grazing X-ray Reflectance (GXR) techniques are applied on different III-V epitaxial structures in order to extract accurately their structural information. Thickness information are obtained directly from Fourier transformation of the GXR spectra and confirmed by simulation of the reflectance curve. Compositions are deduced from SE regression using GXR thickness as input values. Examples on monolayer and bilayer structures are first remembered. Then the potentiality of the method is demonstrated to more complex systems (multilayer mirrors and HEMT structures).
Use of Advantageous Impurity Effects in Metallization
Authors: Murarka S. P. 
Published: April 2011

AbstractImpurities control electrical, mechanical, physical, and chemical properties of the materials. We have manipulated their introduction into semiconductors, insulators, and metals to achieve otherwise unattainable properties. More recently, the continued miniaturization of the solid state devices and circuits have challenged the existing interconnection and contact metallization materials and schemes. These have led to an investigation of new multilevel metallization schemes with lower resistivities and higher reliabilities. In addition, efforts are being made to re-examine the use of newer Al-alloys that may satisfy the resistivity and reliability requirements. This paper will briefly review the existing practices, future needs, and current research activities focused to satisfy these future needs.
Interface Stresses in Nanostructured Multilayered Materials
Authors: Cammarata R. C. , Sieradzki K. 
Published: April 2011

AbstractSurface and interface stresses, which are intrinsic thermodynamic quantities associated with all types of solid surfaces and interfaces are reviewed. A simple model for one type of interface stress is presented. These stresses can strongly influence the structure and mechanical behavior of nanostructured materials such as multilayered materials withultrathin layer thicknesses.
Magnetic Properties of Nanoscale Iron Particles Photodeposited in Glass
Authors: Sunil D. , Gafney H. D. , Tsang C. , Rafailovich M. H. , Sokolov J. , Gambino R. J. , Huang D. M. 
Published: April 2011

AbstractTransmission Electron Microscopy(TEM) and magnetization measurements were used to study the correlation between size of the iron particles precipitated in glass and their magnetic properties. The iron particles les s than 40 Å in diameter photodeposited in porous Vycor glass(PVG) show superparamagnetic behavior at room temperature. As the size of the particles increases and reaches about 100 Å in diameter, the magnetization curve shows minor hysteresis with a very large coercivity.
High Quality AlGaAs Regrowth on Oxide-Free AlxGa1-xAs (x=0.26) by Metalorganic Chemical Vapor Deposition
Authors: Lee Kun-Jing , Huang Z. C. , Chen J. C. 
Published: April 2011

AbstractThe Al0.13Ga0.87As epilayers were regrown by metalorganic chemical vapor deposition (MOCVD) on different AI0.26Ga0.74As substrate layers. It was found that the quality of regrown A10.13Ga0.87As layers were significantly improved when a Se-doped Al0 26Ga0.74As substrate was used. Electrochemical C-V profile showed that no oxide formation and impurity incorporation at the regwon interface. Low-temperature (14.9 K) photoluminescence showed that the full width of half maximum (FWHM) of the bound exciton peak is as low as 4.51 meV. We attributed this improvement to the Se-passivation effect at the surface of Se-doped A10.26Ga0.74As substrate-layers. Results show that Se will delay the formation of native oxide to achieve the better quality of regrown AlGaAs layers.
Single-Photon Ionization, In Situ Optical Diagnostic Of Molecular Beam Epitaxial Growth Of GaAs
Authors: Ott Adina K. , Casey Sean M. , Alstrin April L. , Leone Stephen R. 
Published: April 2011

AbstractSingle-photon ionization time-of-flight mass spectrometry (SPI-TOFMS) is used in situ to monitor desorbing species and surface reactions during molecular beam epitaxy (MBE) of GaAs. In this method, the 1064 nm fundamental output of a Nd:YAG laser is tripled twice to produce 118 nm (10.5 eV) photons. The pulsed light is passed in front of a growing substrate, giving gaseous scattered molecules sufficient energy to ionize, but not fragment, them. Ionized species are detected with time-of-flight mass spectrometry. Arrangement of the experiment also allows for simultaneous real time monitoring with reflection high-energy electron diffraction (RHEED).Mass spectra are examined and analyzed to quantify fluxes and relative ionization cross sections of growth species. The real time behavior of arsenic and gallium mass signals during epitaxy is presented as a function of substrate temperature and incident gallium flux. Surface reactions are proposed to elucidate mechanisms of arsenic incorporation and compared to measured RHEED results.
In-Situ Monitoring Of Mocvd Grown Inall_ As/Gaas Epitaxial Layers By Two Laser Beams Reflectometry
Authors: Baek Jong-Hyeob , Lee Bun , Choi Sung Woo , Lee Jin Hong , Lee El-Hang 
Published: April 2011

AbstractWe report application of in-situ laser reflectometry in monitoring InAl1−xAs (0 ≤ x ≤1) epitaxial layers grown on a GaAs substrate by low pressure metal-organic chemical vapor deposition. Two different lasers were used simultaneously: One was a He-Ne laser operating at 0.6328 μm and the other was a diode laser operating at 1.53 μm. The two laser beams were incident on the growing layer at an angle of 71° from the surface normal, and the reflected beams were detected by Si and Ge photovoltaic detectors, respectively. Since the epitaxial layer of InxAl1−xAs (0 ≤ x ≤1) has a wide range of index of refraction, the reflected signals showed a variety of patterns. The optical constants of the InxAl1−xAs epitaxial layers were obtained for the entire range of composition.
Single-Crystal Fine-Positioning Devices for Scanned-Probe Microscopies
Authors: Kleiman R. N. 
Published: April 2011

AbstractWe have developed a novel fine-positioning device for scanned-probe microscopies. Instead of the conventional scanner tube made of ceramic PZT material, we have constructed analogous structures from single-crystal piezoelectric wafers. Single-crystal materials, in particular Lithium Niobate, are available which solve many of the problems inherent with PZT. In addition, their superior thermal and mechanical properties lead to improved performance in a number of significant ways. We discuss the actual implementation of this idea in the construction of a scanner, possible applications for this design, and briefly discuss results obtained.
Double Modulation and Selective Excitation Photoreflectance for Characterizing Highly Luminescent Semiconductor Structures and Samples with Poor Surface Morphology
Authors: Amirtharaj P. M. , Chandler-Horowitz D. , Bour D. P. 
Published: April 2011

AbstractPhotoreflectance (PR) is a powerful, contactless, and nondestructive technique capable of probing interband electronic transitions and built-in electric-fields at the surface and in interface regions in semiconductor materials and microstructures. It has been widely used as a characterization tool. However, its application to highly luminescent systems, such as quantum-well (QW) lasers and samples with poor surface morphology has been limited because of the difficulty in minimizing the interference from the luminescence and the pump beam that is scattered from the surface. We present a double modulation procedure where both the probe and pump beams are modulated which allows the PR component to be completely separated from the luminescence and scattered contributions. The separation is achieved through the appropriate choice of modulation frequencies and specially designed tuned amplifiers. A complete PR system, along with the necessary circuits, is presented. In addition, we have also exploited the freedom provided by the system to choose any pump wavelength to selectively modulate specific regions of the multilayer structure (QW, barrier, and cladding layer) and extract detailed information regarding the properties of each layer. The applicability of the procedure is demonstrated by fully characterizing a GaInP based QW laser structure used for visible emitters and by measurements on a saw-cut and chemically etched back surface of a commercial GaAs wafer. Finally, procedures attempted in the past to overcome difficulties with the luminescence and surface scattering are discussed and compared to the double modulation PR technique.
Characterization of AlGaAs/GaAs Heterojunction Bipolar Transistors Using Photoreflectance and Spectral Ellipsometry
Authors: Smith Patricia B. , Kim Tae S. , Magel Lissa K. , Duncan Walter M. , Ley A. Vance , Brette Nick A. 
Published: April 2011

AbstractPhotoreflectance spectroscopy (PR) and spectral ellipsometry (SE) have been used to characterize the doping and structure of heterojunction bipolar transistors (HBT). This information provides a more complete description of the epitaxial HBT structure than is possible by relying solely on electrical characterization of specially processed test structures. Additional benefit is derived from the nondestructive nature of both SE and PR. The measurements are fast enough to be implemented on all production-bound HBT material. We describe our recent results comparing capacitance-voltage measurements with PRderived doping levels in the emitter layer of the HBT. We also describe some work comparing SE fit results with Auger electron spectroscopy depth profiles for InGaAs contact layer composition and thickness.
Exciton Dynamics in Ultrathin InAs/GaAs Quantum-Wells
Authors: Brübach J. , Haverkort J. E. M. , Wolter J. H. , Wang P. D. , Ledentsov N. N. , Torres C. M. Sotomayor 
Published: April 2011

AbstractWe have studied the transient behaviour of a sharp emission line, which emerges close to the heavy-hole (hh) exciton photoluminescence line in a 1.6 monolayer thick InAs layer embedded in a GaAs matrix, when the light-hole (lh) exciton transition is excited. We find, that the decaytime of the sharp line is equal to the lh-exciton lifetime for excitation on resonance, but it strongly decreases for excitation off resonance. Since in our structure the energy separation between the hhand lh-exciton transitions amount to one GaAs LO phonon we conclude, that the sharp line originates from double resonant Raman scattering for off resonant excitation, whereas it is predominantly due to resonant luminescence for excitation on resonance. The strong decrease of the intensity of the sharp line due to a temperature rise from 4 to 18K proves the existence of a well confined lh-exciton state. In addition, we performed carrier capture measurements on this structure. We find a constant capture time of 20ps at the lh-exciton transition, whereas the capture time decreases step-like from 55ps to 22ps within the hh-exciton transition. This provides clear evidence for a two-step capture process, where the lh-level acts as an intermediate capture state.
Optical Characterization of Hydrogenated Silicon Films in the Extended Energy Range
Authors: Globus T. , Fonash S. J. , Gildenblat G. 
Published: April 2011

AbstractThis work introduces a new interference technique for the diagnostic characterization of hydrogenated silicon thin films. The interference technique is based on new self-consistent data analysis algorithms for simultaneous optical transmission and specular reflection using exact interference equations for the system of a film on a substrate. It provides a quick non-destructive optical measurement of absorption coefficient and refractive index spectra of amorphous silicon (a-Si:H) and polycrystalline silicon (poly-Si:H) thin films in a wide range of the incident photon energies (0.5–3.5 eV). This non-contacting, high sensitivity method is a powerful probe of various material properties including thickness, refractive index and absorption spectra, hydrogen content, alloy fraction, energies of localized defect states and their concentrations. Experimental results for optical study of hydrogenated Si films indicate that the proposed method makes possible high precision measurements of the absorption in the region near the fundamental edge. In this region the absorption coefficient varies over several orders of magnitude. Also, the absorption related to impurities and defects in the subgap energy region at least from 102 cm−1 can be detected. As a result, the interference technique shows promise in providing feedback for monitoring film growth and device fabrication processes.
In Situ Multi-Wavelength Ellipsometric Control of Thickness and Composition For Bragg Reflector Structures
Authors: Herzinger Craig , Johs Blaine , Chow Peter , Reich Dave , Carpenter Greg , Croswell Dan , Hove Jim Van 
Published: April 2011

AbstractWe have demonstrated real-time feedback control of thickness and composition for Bragg reflector structures using in situ multi-wavelength ellipsometry. This demonstration was performed under conditions which were not ideal for ellipsometric measurements: the angle of incidence for the ellipsometric measurement beam was far away from the Brewster angle, substrate rotation was enabled (which caused an angular wobble in the measurement beam), and strain effects were present in the ellipsometer windows. Furthermore, to simulate drift in the MBE system (and test the effectiveness of the ellipsometer control), the Ga effusion cell was ramped to change the Ga flux by 50% during two of the growth runs. Results of the growth control precision and accuracy are presented; the influence of the non-ideal measurement conditions on the ellipsometer growth control capability is also discussed.
Non-Destructive Characterisation of Rapid Thermally Annealed N+-Doped Polysilicon Using Spectroscopic Ellipsometry
Authors: Carline R. T. , Leong W. Y. , Cullis A. G. , Houlton M. R. , Hope D. A. 
Published: April 2011

AbstractThe use of spectroscopic ellipsometry (SE) to characterise the effects of rapid thermal annealing on Si implanted with phosphorous and phosphorous with fluorine are presented. Variations in the measured SE spectra with anneal temperature and presence/absence of fluorine are clearly observed. Spectra are successfully modelled using refractive indices which are graded with depth. Comparison with cross-sectional transmission-electron microscopy and secondary ion mass spectroscopy show that the results can be correlated with both the crystallinity and impurity distribution in the poly-Si.
Influence of Ohmic Contacts on Semi-Insulating GaAs Detector Performances
Authors: Castaldini A. , Cavallini A. , Canali C. , Chiossit C. , Papa C. Del , Nava F. , Lanzieri C. 
Published: April 2011

AbstractOhmic contact has been observed to play an important role in the performances ofLiquid Encapsulated Czochralski gallium arsenide particle detectors since it is possible to control the injection of charge carriers which determines the device performances. Alloyed and implanted contacts characteristics have been compared to relate the presence of electrically active defects induced during contact preparation to the final detector efficiency. In-situ optical probing investigations have been carried out to analyze the electric field distribution. Spectroscopic investigations show that the contact fabrication process significantly influences the trap density, whilst it does not change their type.
Acoustic Emission for The Diagnostic of Semiconductor Structures
Authors: Lyashenko O. V. , Perga V. M. 
Published: April 2011

AbstractAcoustic emission (AE), electric current fluctuation, as well as luminescence intensity fluctuations in lightemitting semiconductor structures have been investigated. The authors examined the hypothesis about the origin of nonelectronic acoustic low frequency noise that is observed in electronic systems. The various sets of AE's sources allow one to understand the various dynamics of the AE in the structures on the A3B5 compound base and p-n germanium diodes.
Study of Periodic Surface Nanostructures Using Coherent Grating X-Ray Diffraction (CGXD)
Authors: Shen Qun 
Published: April 2011

AbstractIt is shown that an x-ray interference phenomenon, Coherent Grating X-ray Diffraction (CGXD), can be used to study lateral nanostructure arrays on crystal surfaces and interfaces. Compared to Fraunhofer grating diffraction of visible light, x-ray grating diffraction contains information not only about geometric profiles of a surface, but also about the internal crystalline structures and lattice strain distributions in grating features. Grating diffraction patterns can also be measured in a white-beam Laue method using highly collimated polychromatic synchrotron radiation. This provides a way for parallel data collection and is useful inin-situstudies of structural evolution of nanostructure arrays.
Transmission Electron Diffraction Techniques for NM Scale Strain Measurement in Semiconductors
Authors: Vanhellemont J. , Janssens K. G. F. , Frabboni S. , Smeys P. , Balboni R. , Armigliato A. 
Published: April 2011

AbstractAn overview is given of transmission electron microscopy techniques to address strain with nm scale spatial resolution. In particular the possibilities and limitations of (large angle) convergent beam electron diffraction ((LA)CBED) and electron diffraction contrast imaging (EDCI) techniques are discussed in detail. It will be shown by a few case studies that unique and quantitative information on local strain distributions can be obtained by the combined use of both (LA)CBED and EDCI in correlation with three dimensional finite element simulations of the strain distributions in the thinned specimen.
Optical and Structural Characterization of Arsenide/Phosphide Interfaces Formed by Flow Modulation Epitaxy
Authors: Emerson D. T. , Smart J. A. , Whittingham K. L. , Chumbes E. M. , Shealy J. R. 
Published: April 2011

AbstractBulk GaAsP, 20Å–500Å GaAsP/GaInP single quantum wells and 70 Å period GaAsP/GaInP superlattices were deposited on GaAs substrates by Flow Modulation Epitaxy. In these structures, the disordered GaInP is lattice matched while the GaAsP is in tension with the As mole fraction varying from 0.6 to 1. The structures were studied using asymmetric x-ray diffraction, 1K photoluminescence, Raman scattering, transmission electron microscopy and atomic force microscopy. Raman and x-ray diffraction are used to assess the structural quality of the superlattices, especially with regard to the presence/absence of superlattice x-ray satellites and disorder activated longitudinal acoustic phonons. A model including the effects of composition, strain, and confinement on longitudinal optic phonons is described and used to estimate the composition, using Raman scattering, in the thin, pseudomorphic GaAsP layers in the superlattices. Photoluminescence is used to assess the composition of the interfacial layers in the single quantum wells and to determine transition energies in the superlattices. In addition, analysis of the heterostructure luminescence, including prediction of the energy band alignment as calculated with the model solid theory corrected for strain, is found to suggest the presence of a type II band alignment in the heterostructures for some values of GaAsP composition. Finally, Raman scattering and x-ray diffraction are used to compare arsenide to phosphide interfaces in GaAs and InP-based heterostructures.
Characterization Of Nitrogen Species For P-Type Doping Of Znse
Authors: Kimura K. , Kajiyama H. , Miwa S. , Asuda T. Y , Kuo L. H. , Jin C. G. , Tanaka K. , Yao T. 
Published: April 2011

AbstractLaser-induced fluorescence(LIF) spectroscopy has been applied to the detection of excited nitrogen molecules coming out of a plasma source used for p-type doping of ZnSe. With the use of a fluorescence-photon-counting system, the fluorescence of nitrogen molecules in the A3 Σ u+ (v=0) state was observed even in a high vacuum condition ˜ 10−4 Pa. The correlation between LIF intensity of nitrogen molecules in the A3 Σ u+(v=0) state and the net acceptor concentration of nitrogen doped ZnSe epitaxial layers was investigated.