bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characterization of SinGem Strained Layer Superlattice P-N Junctions
Authors: Engvall Jesper , Olajos Janos , Grimmeiss Hermann G. , Presting Hartmut , Kibbel Horst , Kasper Erich 
Published: March 2011

AbstractA series of three p-n junctions consisting of ten monolayer strain adjusted SinGem superlattices (Si6Ge4, Si5Ge5, Si4Ge6) has been characterized with respect to Current-Voltage, Capacitance-Voltage and Short Circuit Photocurrent measurements. The samples were grown by MBE with an Antimony surfactant resulting in improved interface sharpness. Superlattice interband transitions were measured by Short Circuit Current spectroscopy and bandgap energies were determined by a fitting procedure. The temperature dependence of the junction capacitance and of the Short Circuit Current indicate a potential barrier for electrons at the superlattice-buffer interface that impedes electron transport from the p-n junction at lower temperatures.
The Relationship Between Surface Chemistry and Photoluminescence of Porous Silicon
Authors: Li Kun-Hsi , Tsai Chaochieh , Campbell Joe C. , Kovar Milan , White John M 
Published: March 2011

AbstractGreen photoluminescence (PL) is observed from an as-anodized porous Si wafer immersed in the anodization electrolyte and the PL turns red after the sample is removed from the electrolyte and is blown dry. The PL of porous Si immersed in alcohol exhibits a blue shift and a marked decrease in intensity relatively to dry, as-anodized wafers. However, when the immersed samples are treated with UV for a few minutes, the PL peak shifts to a longer wavelength. Fourier-transform infrared spectroscopy reveals that alkoxy surface species and silicon hydride species backbonded to oxygen atoms appear on the UV-treated samples. Furthermore, the PL characteristics and surface species of the UV-treated samples can be recovered to those of as-anodized wafers by dipping in HF. These results point out the importance of surface chemistry in the luminescence process of porous Si.
Enhanced Luminescence and Optical Cavity Modes from Uniformly Etched Porous Silicon
Authors: Doan Vincent V. , Curtis C. L. , Credo G. M. , Sailor M. J. , Penner R. M. 
Published: March 2011

AbstractUniform layers of porous silicon have been produced in a photoelectrochemical etch that show intensity enhancements of up to 100 fold, relative to samples etched in the dark. These films can also show fine structure in their photoluminescence (PL) spectra characteristic of longitudinal optical cavity modes. The highly luminescent, uniform porous layer is generated by illumination with blue or green light during the electrochemical etch of singlecrystal (B-doped) Si, and the enhancement is attributed to a localized photochemical etch process. The relevance of the increased PL intensity and interference-induced spectral changes to measurements of the intrinsic emission spectrum of porous Si are discussed.
Luminescence Studies of MBE Grown SI/SIGE Quantum Wells
Authors: Gail M. , Brunner J. , Menczigar U. , Zrenner A. , Abstreiter G. 
Published: March 2011

AbstractWe report on detailed luminescence studies of MBE grown Si/Si1-xGex quantum well structures. Both well width and composition is varied over a wide range. Bandgap photoluminescence is observed for all samples grown at elevated temperatures. The measured bandgap energies are in good agreement with subband calculations based on effective mass approximation and taking into account the segregation of Ge atoms during growth. Diffusion is found to limit quantum well (QW) growth with Ge-contents above 35% at high temperatures. The photoluminescence signals are detected up to about 100K and can be attributed to interband transitions of free excitons. We also present investigations of the exciton binding energy as a function of well width and composition. The observed shift of the exciton binding energy is compared with results of a variational calculation. A distinct onset in photocurrent and electroluminescence up to 200 K are observed in quantum well diodes.
Photoluminescence of Chemically Etched Polycrystalline and Amorphous Si Thin Films
Authors: Steckl A. J. , Xu J. , Mogul H. C. 
Published: March 2011

AbstractSi thin films were deposited on quartz at temperatures ( TD ) ranging from 540 to 640°C. X-ray diffraction indicates that films deposited at TD < 580°C are amorphous, while those deposited above 600°C are poly-crystalline with a <220> texture. The Si films were made porous by stain-etching in HF:HNO3:H2O. Only Si films deposited at 590°C and above show photoluminescence (PL), centered at ∼650-670 nm under UV excitation. Films deposited at TD < 580°C do not luminesce even after very long etch times, which produce a highly porous structure. The PL intensity and the x-ray signal follow a very similar trend with TD. It appears that a minimum level of crystallinity is required for photoemission in porous Si and that a strong relationship exists between them.
Nonlinear Optical Properties and Fatigue Effect in Porous Silicon
Authors: Griviekas Vytautas , Kolenda Jonas , Misoguti Lino , Basmaji Pierre , Zilio Sirgio C. 
Published: March 2011

AbstractWe report results of photoluminescence (PL) fatigue and nonlinear optical absorption in anodized porous silicon (PS) samples aged in air for a few months. The fatigue strength is found different for PS emitting below 1.65 eV, in 1.65 - 2.05 eV range and above 2.05 eV, revealing the different nature of PL. A comparison with two special glasses is made, and a possible explanation for PL mechanism in PS is discussed.
Synthesis of Dislocation Free Siy(SnxC1−x)1−y Alloys by Molecular Beam Deposition and Solid Phase Epitaxy
Authors: He Gang , Savellano Mark D. , Atwater Harry A. 
Published: March 2011

AbstractSynthesis of strain-compensated single-crystal Siy(SnxC1-x)1-y alloy films on silicon (100) substrates has been achieved with compositions of tin and carbon greatly exceeding their normal equilibrium solubility in silicon. Amorphous SiSnC alloys were deposited by molecular beam deposition from solid sources followed by thermal annealing. In situ monitoring of crystallization was done using time-resolved reflectivity. Good solid phase epitaxy was observed for Si0.98Sn0.01C0.01, at a rate about 20 times slower than that of pure silicon. Compositional and structural analysis was done using Rutherford backscattering, electron microprobe, ion channeling, x-ray diffraction, and transmission electron microscopy.
Simulation of A Low Loss Optical Modulator for Fabrication in Simox Material
Authors: Tang C K , Reed G T , Walton A J , Rickman A G 
Published: March 2011

AbstractA novel phase modulator has been designed and analysed, assuming fabrication in a silicon-on-insulator material such as SIMOX. The proposed modulator is based upon a transverse p-i-n structure, utilising the plasma dispersion effect to produce the desired refractive index change in an optical rib waveguide. The device has been studied using the MEDICI two dimensional device simulation package to optimise the injected carrier interaction with the propagating optical mode. Whilst the device is designed to support a single optical mode, it measures several micrometers in cross sectional dimensions, thereby simplifying fabrication and allowing efficient coupling to other single mode devices such as optical fibers. Furthermore the device has an extremely high figure of merit, predicting over 200 degrees of induced phase shift per volt per mm. This implies a short active length together with a low power requirement.
Electroluminescence Evaluation of the SiO2-Si Structures Using an Electrolyte-SiO2-Si Cell
Authors: Baraban A.P. , Konorov P.P. , Bota S.A. , Morante J.R. 
Published: March 2011

AbstractThe use of an Electrolyte-SiO2-Si system allows a detailed control of the electron injection from the electrolyte into SiO2 layer, and makes feasible to reach the electron heating in the conduction band of SiO2 before to take place the irreversible breakdown.The injected and heated electrons enhance the probability of the SiO2 defect excitation as well as the Si-O bond breaking. Both features give raise to the relaxation processes which are responsible of the electroluminescence characteristics of the oxide. So, the measured electroluminescence spectrum presents straightforward information on the defect types, their nature and possible precursor defect behaviour. Results on silicon oxides obtained from different technological processes and treatments, corroborate the above analysis and show the electro-luminescence of SiO2 as an interesting and powerful method to evaluate the SiO2 properties.
X-Ray Investigation of Strain Relaxation in Short-Period SimGen Superlattices using Reciprocal Space Mapping
Authors: Hamberger P. , Koppensteiner E. , Bauer G. , Kibbel H. , Presting H. , Kasper E. , Pesek A. 
Published: March 2011

AbstractThe optoelectronic properties of SimGen strained layer superlattices (SLS's) depend strongly on the structural perfection. We used double crystal and triple axis x-ray diffractometry to characterize the structural properties of short period Si9Ge6 SLS's grown on about lμm thick step-graded SiGe alloy buffers. As grown SLS's and samples annealed subsequently at 550°C, 650°C and 780°C for 60 mmn were investigated. Precise strain data were extracted from two-dimensional reciprocal space maps around (004) and (224) reciprocal lattice points. These data were used as refined input parameters for the dynamical simulation of the integrated intensity along the qll[004] direction. Annealing causes interdiffusion as indicated by the decreasing superlattice (SL)-satellite peak intensities and by the change of the Si/Ge thickness ratio. However, the full width at half maximum of the SL satellite peaks does not change significantly with annealing up to 650°C. The in-plane SL lattice constant in both samples is increased only slighty by annealing (< 9×10−3 Å). Consequently the interface intermixing due to interdiffusion is the main cause for the shift of the luminescence energy to higher values in these annealed samples.
Unimportance of Siloxene in Luminescent Porous Silicon as Determined by Nexafs & Exafs
Authors: Friedman S.L. , Marcus M.A. , Adler D.L. , Xie Y.-H. , Harris T.D. , Citrin P.H. 
Published: March 2011

AbstractNear-edge-- and extended--x-ray absorption fine structure measurements, as well as luminescence excitation and emission spectra, were obtained from samples of porous Si and siloxene. Contrary to a recently proposed explanation for the room temperature luminescence in porous Si, the combined data indicate that siloxene is not principally responsible for the observed effect.
Comparative Study of Light-Emitting Porous Silicon Anodized with Light Assistance and in the Dark
Authors: Tsybeskov L. , Peng C. , Duttagupta S.P. , Ettedgui E. , Gao Y. , Fauchet P.M. , Carver G.E. 
Published: March 2011

AbstractIn this study, we compare two different types of light emitting porous silicon (LEpSi) samples: LEpSi anodized in the dark (DA) and LEpSi anodized with light assistance (LA). On the basis of photoluminescence (PL), Raman, FTIR, SEM, spatially resolved reflectance (SRR) and spatially resolved photoluminescence (SRPL) studies, we demonstrate that the luminescence in LA porous silicon is strong, easily tunable, very stable and originates from macropore areas. These attractive properties result from passivation by oxygen in the Si-O-Si bridging configuration that takes place during electrochemical anodization. In addition, we have been able to correlate light emission with the presence of crystalline silicon nanograins.
Enhanced Band-Gap Luminescence in Strain-Symmetrized (Si)m(Ge)n Superlattices
Authors: Menczigar U. , Abstreiter G. , Kibbel H. , Presting H. , Kasper E. 
Published: March 2011

AbstractWe report on band-gap luminescence in short period, strain symmetrized (Si)m(Ge)n superlattices grown on relaxed, step-graded Sil-xGex alloy buffer layers. The dislocation density in the superlattices, which were grown at 500°C using Sb as a surfactant, is reduced by 2-3 orders of magnitude compared with superlattices grown on thin, partly relaxed Sil-xGex buffer layers. Due to the improved quality of the superlattices, well defined band-gap luminescence could be observed which is for a (Si)6(Ge)4 superlattice strongly enhanced compared with a Si0.6Ge0.4 alloy reference sample. The measured band-gap energies compare well with theoretical predictions. To study the influence of interdiffusion of the Si- and Gelayers on the band-gap of the superlattices, the samples were annealed and studied with photoluminescence and Raman spectroscopy. An increasing band-gap and a decreasing luminescence efficiency was found with increasing intermixing of the layers. These experimental results are well described with an interdiffuision model of the layers in conjunction with an effective mass calculation.
Silicon Nanostructures in Si-Based Light-Emithing Devices
Authors: Namavar Fereydoon , Pinizzotto R.F. , Yang H. , Kalkhoran N. , Maruska P. 
Published: March 2011

AbstractHigh resolution cross-sectional electron microscopy and electron diffraction of an np heterojunction porous Si device, capable of emitting light at visible wavelengths, clearly indicates the presence of Si nanostructures within the quantum size regime. These results indicate that the quantum confinement effect is at least partially responsible for photoluminescence at visible wavelengths.
Visible Photoluminescence From Porous Silicon Carbide
Authors: Matsumoto T. , Tamaki T. , Futagi T. , Mimura H. , Kanemitsu Y. 
Published: March 2011

AbstractWe have fabricated porous silicon carbide using single crystal 6H–SiC that has a wider indirect bandgap than silicon crystal prepared by electrochemical anodization. We have observed intense blue–green luminescence with the peak wavelength of around 500 nm at room temperature. The luminescence intensity is about five hundred times stronger than that of free electron to acceptor recombination in 6H–SiC crystal. This porous SiC offers an intense blue–green luminescent material. The results of structural analysis (secondary electron microscope analysis) and optical measurements (photoluminescence spectrum, Raman spectrum, and picosecond luminescence decay) suggest that the origin of the intense blue–green luminescence is the same as that of the intense red luminescence of porous silicon.
Characterization of Photoluminescence From Anodically Etched SiC/Si Heterostructures
Authors: Steckl A. J. , Su J. N. , Xu J. , Li J. P. , Yuan C. , Yih P. H. , Mogul H. C. 
Published: March 2011

AbstractPatterned SiC/Si heterostructures have been treated by anodic etching in HF/ethanol solutions at 25°C. The anodic process used a current density ranging from 2-10 mA/cm2 and times from 2-5 min. The SiC/Si samples had SiC regions and exposed Si regions of dimensions from 2.5 μm to ∼500 gm. For μm substrates, short etching times (≥3 min) result in selectivcarea UV-induced visible photoluminescence (PL) being observed at 25°C from only the SiC regions. Longer etching times (≥3 min) render both the SiC-protected and the exposed Si regions photoluminescent, with nearly identical spectral characteristics and with a peak located at 660-670 nm. The selective-area PL is based on the rapid lateral etching of the n-Si surface under the SiC layer due to either high surface stress caused by the lattice mismatch between SiC and Si and/or to a higher SiC conductance. This is confirmed by the time progression of the PL images in the SiC regions. The PL degradation with UV exposure time has been shown to be substantially reduced by a passivation procedure involving HNO3/H2O. For SiC/p-Si structures, the exposed Si regions become photoluminescent upon very short anodization time, while the SiC regions did not luminesce at all for even the longest anodization times used (5 min).
Optical Studies of porous Silicon
Authors: Lin T. , Sixta M. E. , Cox J. N. , Delaney M. E. 
Published: March 2011

AbstractThe optical properties of both electrochemically anodized and chemically stain-etched porous silicon are presented. Fourier transform infrared (FTIR) spectroscopy showed that absorbance in stain-etched samples was 3x and 1.7x greater than in anodized samples for the SiH/SiH2 stretch and scissors-bending modes, respectively. Also, oxygen is detected in stain-etched samples immediately after formation, unlike anodized samples. Photoluminescence measurements showed different steady state characteristics. Electrochemical-etched silicon samples stored in air increased in photoluminescent intensity over time, unlike the stain-etched samples. A photoluminescent device made by anodization on epitaxial p-type material (0.4 Ωm) on n-type substrate (0.1 Ω-cm) did not exhibit electroluminescence.
Prospects for Infrared Electroluminescence From Porous Silicon
Authors: Koch F. , Kux A. 
Published: March 2011

AbstractEfficient visible luminescence from porous Si requires the 3-dimensional confinement of charges in structures with typical ∼3nm size. Such microporously etched Si acts as an intrinsic wide-gap material and is highly resistive. The material does not have the good transport properties consistent with an efficient electrical excitation. We instead suggest to employ mesoporously etched, p+-type Si with its better conductivity in electroluminescence application. The material luminesces in two spectral bands centered about 0.8eV and 1.0eV in the infrared. Both emissions originate from surface-bound states. We report on the temperature dependence of luminescence, on transport and first attempts to generate infrared light by the injection of electrical current.
Oxygen-Enhanced 1.54μm Photoluminescence of Er+3 in Silicon
Authors: D'avltaya F. Arnaud , Campidelli Y. , Chroboczek J.A. , Favennec P.N. , L'haridon H. , Moutonnet D. , Wasiela A. 
Published: March 2011

AbstractFavennec et al. (Jap. J. Appl. Phys. 29, L524, 1990) reported that the 1.54μm photoluminescence of Si implanted with Er+3 is activated by oxygen impurities. We observe a significant enhancement in the luminescence in Er-doped silicon epitaxial layers MBE-grown with intentional oxygen contamination. The PL is shown to be a bulk property of the material as it persisted after a partial layer removal by wet etching.
1.54 μm Photoluminescence of Erbium Implanted Hydrogenated Amorphous Silicon
Authors: Kechouane M. , Beldi N. , Mohammed-Brahim T. , L'Haridon H. , Salvi M. , Gauneau M. 
Published: March 2011

AbstractThe luminescence of erbium implanted in hydrogenated amorphous silicon (a-Si : H) is presented. For the first time an intense and relatively sharp luminescence at 1.54 mm is observed in a-Si : H, using implanted erbium. The Er+ emission intensity strongly depends on the hydrogen film content and on the measurement temperature. A direct correlation between the optical gap energy of the semiconductor and the hydrogen film content is observed.
Dependence of Residual Stress of Diamond-Like Carbon Films on Precursor Gases and Process Parameters of RF PACVD
Authors: Lee Kwang-Ryeol , Baik Young-Joon , Yong Eun Kwang 
Published: March 2011

ABSTRACTResidual compressive stress of diamond-like carbon (DLC) films was measured by beam deflection method. DLC films were deposited on thin Si wafers using r.f. plasma decomposition of methane and benzene. Negative bias voltage of the cathode was varied from -100 to -800 V and deposition pressure from 3 to 100 mTorr. When using benzene as precursor gas, the residual stress monotonically increases as increasing . (Here, Vb is the negative bias voltage of cathode and P the deposition pressure.) In case of using methane, however, the residual stress has a maximum value at between 70 and 100 V/mTorr1/2. Because of the difference in molecular size between benzene and methane, the mean free path of ions in benzene discharge is 5 times shorter than that in methane discharge. The contrasting behavior of residual stress is discussed in terms of the difference in ion energies at the specimen surface due to the difference in mean free path. On the other hand, total hydrogen concentration decreases as increasing in both cases. This result thus shows that the total hydrogen concentration cannot be a key to understand the behavior of residual stress.
Effects of Film Thickness and Annealing Temperature on the Stress in Amorphous Gd-Fe Alloy Thin Films
Authors: Zhou Zhi-feng , Fan Yu-dian 
Published: March 2011

ABSTRACTGd-Fe films were deposited by magnetron sputtering on glass substrates. The results shoved that the stress is compressive in most cases, and a larger compressive stress exists at the film-substrate interface. The stress is independent on the film thickness when the film thickness is greater than 0.20 μm. The stress becomes tensile only when the annealing temperature attains 400ºC. Therefore, the interfacial stress and the growth stress coexist in the Gd-Fe films, and the former will not be dominant when the film thickness is greater than 0. 2μm. The interfacial stress may originate from the inhomogeneous distribution of film composition at the interface, and the origin of growth stress can be explained by the atomic peening effect. The relation between the stress and the annealing temperature can be comprehended with the amorphous structure model.
Mechanical Characterization of Thin Films Using Full-Field Measurement of Diaphragm Deflection
Authors: Pratt R. I. , Johnson G. C. 
Published: March 2011

ABSTRACTA new method for evaluating the elastic moduli and residual stresses in thin films is presented. This technique is based on measurement of the complete deflected shape of pressurized diaphragms made of the material to be evaluated. It offers important advantages over previous techniques in which only the displacement of the center of the diaphragm is measured as a function of pressure. The experimental apparatus uses a laser beam and its reflection from the sample surface to determine relative height. Measurements are made over an area of the sample by performing a two-dimensional scan of the sample under the laser beam. The most important advantage of determining the entire deformed shape of the diaphragm is that the shape is known rather than assumed. This way, the particular theory chosen to analyze the structural response does not also dictate a deformed shape based solely on the maximum deflection at the midpoint. Plate theory, as opposed to the more traditional membrane theory, is used to account for the dominance of bending behavior at low pressure and near the diaphragm edges. An energy method is employed to estimate stiffness and residual stress. The accuracy of this approximate method is directly related to how closely the assumed mode shape used in the analysis approximates the true response of the structure. Since these surface profiles are measured experimentally, the resulting property estimates are obtained with increased confidence.
Stress Measurements in Materials for Magnetic Recording
Authors: Raman V. , Coffey K.R. , Umphress R. , Howard J.K. 
Published: March 2011

ABSTRACTInvestigations of the mechanical behavior of materials used in magnetic recording is of considerable practical importance in order to assure reliable file performance. With this objective, we have investigated the magnitude of the internal stresses observed in four sputtered thin film materials typically used in magnetic recording. First, the magnitude of the stresses observed in sputtered carbon films with and without hydrogen were measured and the nature of stress relaxation and thermal stability in different ambicnts were investigated. Second, the magnitude of the internal stress in CoPtCr magnetic media with and without a Cr-based sublayer that enhances magnetic performance was examined. Finally, the magnitude of stresses typically observed in thicker sputtered films of alumina were investigated both at room temperature and at elevated temperatures. The magnitude of the stresses observed in these sputtered films and their influence on mechanical performance are discussed.