bluuebunny/crossref_metadata_2025_split huggingface dataset:
Optical Properties of Free-Standing Porous Si Films
Authors: Kanemitsu Y. , Uto H. , Masumoto Y. , Matsumoto T. , Futagi T. , Mimura H. 
Published: March 2011

AbstractWe have studied optical properties of free-standing porous Si thin films fabricated by electrochemical anodization. The average diameter of Si crystallite spheres is evaluated by Raman spectroscopy and transmission electron microscopy. The blueshift of optical absorption spectrum is observed with a decrease in the average diameter of Si crystallites. However, there is no clear size dependence of the peak energy of broad photoluminescence spectrum. Spectroscopic analysis strongly suggests that the photogeneration of carriers occurs in the c-Si core whose band gap is modified by the quantum confinement effect, whereas the radiative recombination of carriers occurs in the near-surface region of small crystallites.
Porous Silicon Nanostructure Revealed By Electron Spin Resonance
Authors: Xiao Y. , McMahon T.J. , Pankove J.I. , Tsuo Y.S. 
Published: March 2011

AbstractElectron spin resonance (ESR) study of annealed porous Si (PS) samples shows the existence of 20% to 30% of oxygen related Pbl (.Si-Si2O) centers, in addition to the Pb0 (·Si-Si3) centers already reported by other groups. The 29Si hyperfine and superhyperfine lines are well-defined at room temperature. We find that the nanostructure of PS, although twisted as appeared in scanning electron microscopy images, is well aligned with the underlying crystal lattice, and the ESR line broadening is mainly due to the local strain around the dangling bonds and not to the nanoscale column or particle misalignment.
Effect of Preparation Conditions on the Silicon L-Edge In Electrochemically Prepared Porous Silicon
Authors: Buuren T. Van , Tiedje T. , Weydanz W. 
Published: March 2011

AbstractHigh resolution measurements of the silicon L-edge absorption in electrochemically prepared porous silicon show that the absorption threshold is shifted to higher energy relative to bulk silicon, and that the shift is dependent on how the porous silicon is prepared. When the porous silicon is made from n-type material with light exposure, the blue shift increases logarithmically with the anodizing current. Porous silicon prepared by anodizing p-type silicon exhibits a blue shift in the L-edge which increases with the time spent in the HF solution after the anodizing potential is turned off. The data are consistent with the quantum confinement model for the electronic structure of porous silicon.
Two-Dimensional Excitons in Siloxene
Authors: Brandt M. S. , Rosenbauer M. , Stutzmann M. 
Published: March 2011

AbstractThe luminescence properties of two different modifications of siloxene are studied with photoluminescence excitation spectroscopy (PLE) und optically detected magnetic resonance (ODMR). The luminescence of as prepared siloxene, which consists of isolated silicon planes, is resonantly excited at the bandgap, indicating a direct bandstructure. The observation of Δm = ±2 transitions in ODMR shows that triplet excitons contribute to the luminescence process. In contrast, annealed siloxene consisting primarily of six-membered silicon rings shows a PLE typical of a material with an indirect bandgap. The ODMR signal of annealed siloxene and of porous silicon show the same Gaussian line with a typical width of 400 G, which can arise from strong dipolar coupling of an electron and a hole ≈ 5Å apart.
Variations in the Photoluminescence Intensity of Chemically and Anodically Etched Silicon Films
Authors: Williams P.S , Kidder J.N. , Yun H. , Crain D. , Pearsall T.P. 
Published: March 2011

AbstractWe are studying the effects of etch conditions on the surface morphology, chemistry, and luminescent properties of porous silicon (PS) films. Luminescent silicon films are produced by chemical etching using solutions of HNO3 in HF and by anodic etching using aqueous HF electrolytes. Films produced by both methods are analyzed and compared using photoluminescence (PL), vibrational, and X-ray photoelectron (XPS) spectroscopies. The initial characterization of PS is performed immediately following the etching process, resulting in oxide-free films (as confirmed by XPS). In chemically etched PS films, the luminescent intensity decreases as the vol. % HNO3 in etch solution increases. Spectral features evolve in the PL spectrum of chemically etched films as the result of aging under ambient conditions and when the films are cooled under illumination. Moreover, we have also found that increased electrolyte convection results in a decrease in photoluminescence intensity of PS films formed anodically. The role of electrolyte flow in modifying the luminescent properties of PS is being evaluated in an etch cell with well-characterized hydrodynamics.
Ion Exchange Effects in Porous Silicon
Authors: Matvienko B. , Basmaji P. , Grivickas V. , Bernussi A. 
Published: March 2011

AbstractWe report an effect of alkaline metal ion incorporation into porous silicon (PS) structure from the electrolyte during anodic etching. Blue shift of the whole luminescence spectrum was obtained as a consequence of ion incorporation. We suggest the presence of zeolite-type structures in PS, as an explanation to the observed properties.
Energy Localisation and Surface Interactions in the Luminescence of Porous Silicon
Authors: Gardelis S. , Dawson P. , Hamilton B. 
Published: March 2011

AbstractThe fundamental mechanisms controlling the light emission from porous Si remain unresolved. In this paper we report attempts to modify the luminescence using a variety of surface processing steps, such as vacuum annealing with subsequent anneals in nitrogen and oxygen, exposure to hydrofluoric acid (HF) and rapid thermal oxidation. Luminescence, infrared absorption, and electron spin resonance (ESR) have all been used to gain more information on the link between the optical emission and the localisation of the electrons in this material system. We present evidence that the silicon dangling bond is the key component in the non-radiative recombination. This is based on measurements shown that hydrogen coverage of the surface is significant because of saturation of the dangling bonds and a subsequent reduction in the competing non-radiative paths rather than as an active component in the radiative transition. Finally, we focus our attention upon the lower energy band which appears in the luminescence spectrum of porous Si (∼0.9eV) by examining its behavior under the surface treatments mentioned above. We found that this luminescence band originates from the surface of the porous layer and its intensity correlates well with increasing oxidation of the porous layer.
Electroluminescence From μc-SiC / Porous Si PN Junctions
Authors: Mimura H. , Futagi T. , Matsumoto T. , Ohta Y. , Kitamura K. , Kanemitsu Y. 
Published: March 2011

AbstractWe have measured electrical properties and electroluminescence (EL) characteristics of the light-emitting diode (LED) based on a pn junction of n-type microcrystalline silicon carbide (μc-SiC) and porous silicon (PS). The μc-SiC/PS pn junctions showed rectification behavior, and a uniform red EL was observed at a forward voltage larger than 15V. From the relationship between the EL intensity and the forward current, the EL mechanism is interpreted as the recombination of electron-hole pairs doubly injected into the PS layer. No degradation was observed in the EL intensity during the measurements over 8 hours. These results means that μc-SiC serves well as a electron injector to the PS.
Monocrystam Disiocationless Si:Ge, Grown from the Helt Wits Gd Impurity
Authors: V.V. Borschensky , D.I. Brinkevich , V.V. Petrov , V.S. Prosolovch 
Published: March 2011

AbstractThe properties of Si grown from the melt having impurities of germanium and gadolinium have been studied by IR-absorption and Hall effect methods.It was stated that Ge and Gd are effective getters for technological impurities of oxygen and carbon in silicon melt. It has been shown that the combined doping by rare earth and isovalent impurities allows to increase the thermostability of dislocationless monocrystals of silicon.
Epitaxial Layers Si: (Sn,Yb) Produced by the Crystallization From the Melt-Solution on the Basis of Sn.
Authors: Brinkevich D.I. , Kazuchits N.M. , Petrov V.V. 
Published: March 2011

AbstractEpitaxial layers (EL) Si:Sn doped with Yb in the process of liquid phase epitaxy were studied by optical microscopy and photoluminescence (PL) methods.At low concentration of lanthanoid (0,01 < Nyb > 0,1 weight %) the good planarity of the interface and high quality of the surface are detected. At NYb > 0,1 weight % microirregularities are presented.In EL Si:(Sn, Yb) irradiated by 4,5 MeV-electrons the suppression of the generation of radiaton defects, responsible for G– and C-lines of PL, has been found. This effect has been explainedwithin the score of the model takeng into the consideration gettering propering ofYb in reference to the impurities of 0 and C as deformation fields, attributed to the presence of Sn atoms.
High Concentrations of Erbium in Crystal Silicon by Thermal or Ion-Beam-Induced Epitaxy of Erbium-Implanted Amorphous Silicon
Authors: Custer J. S. , Polman A. , Snoeks E. , Hoven G. N. van den 
Published: March 2011

AbstractSolid phase epitaxy and ion-beam-induced epitaxial crystallization of Er-doped amorphous Si are used to incorporate high concentrations of Er in crystal Si. During solid phase epitaxy, substantial segregation and trapping of Er is observed, with maximum Er concentrations trapped in single crystal Si of up to 2 x 1020 /cm3. Ion-beam-induced regrowth results in very little segregation, with Er concentrations of more than 5 X 1020 /cm3 achievable. Photoluminescence from the incorporated Er is observed.
Optical Direct and Indirect Excitation of Er3+ Ions in Silicon
Authors: Majima A. , Uekusa S. , Ootake K. , Abe K. , Kumagai M. 
Published: March 2011

AbstractOptical direct and indirect excitation of erbium (Er) ions in silicon substrates was performed in order to investigate the high efficiency of Er3+− related 1.54μm emission (4I13/2→4I15/2) for direct excitation that is not concerned with the indirect band gap and low quantum efficiency of a Si host. The samples were prepared by ion-implantation or thermal diffusion methods. In each sample, photoluminescence (PL) showed the peaks originating from 4I13/2→4I15/2 of Er3+ ions.In Er thermally diffused samples, optical excitation for energy level 4I11/2 of Er3+ ions was successfully effected by photoluminescence excitation spectroscopy (PLE). The PLE spectra consisted six peaks (963.1nm, 965.0nm, 976.lnm, 978.9nm and 980.9nm) which were caused by direct excitation (4I15/2→4I11/2) of Er3+ ions. The emission directly excited is about 2 times more intense than the indirectly excited emission. The six peaks originating from the splitting of the 4I11/2 levels meant that Er3+ ions were in the sites of noncubic symmetry. The samples prepared by Er ion-implantation did not show the effect.
Effect of the Er3+ Concentration on the Luminescence of Ca1-xErxF2+x Thin Films Epitaxially Grown on Si(100)
Authors: Barriere A.S. , Raoux S. , Favennec P.N. , L'haridon H. , Moutonnet D. 
Published: March 2011

AbstractCa1-xErxF2+x thin films, with a substitution rate, x, varying from 1 to 20%, were deposited on Si(100) substrates by sublimation of high purity solid solution powders under ultra-high-vacuum. Rutherford backscattering studies have shown that the films have the composition of the initial solid solution powders, are quite homogeneous and are epitaxially grown on the substrates.The optical properties of these films were studied by means of cathodoluminescence and photoluminescence. At room temperature, the emissions due to the de-excitations from the 4S3/2, 4F9/2, 4I11/2 and 4I13/2 excited levels to the 4I15/2 ground state of Er3+ (4f11) ions are easily detected (λ = 0.548, 0.66, 0.98 and 1.53 μm)The strong 1.53 μm infrared luminescence, which presents evident potential applications for optical communications, is maximum for an erbium substitution rate included between 15 and 17%. These Er concentrations are three or four orders of magnitude greater than the optimum ones in the case of Er-doped semiconductors, which are close to 1018 cm-3. In the visible range, the luminescences are also important.They allow us to detect high energy ion or electron beams. However their maximum efficiencies were observed for a relatively low erbium concentration, close to 1%. These different behaviours are explained by the cross relaxation phenomena, which depopulate the higher levels to the benefit of the 4I13/2 → 4I15/2 transition.The energy distribution of the Stark sublevels of the 4I15/2 state, which results from crystal field splitting, was deduced from a photoluminescence study at 2K. The obtained results show that the environment of the luminescent centres does not change with the erbium concentration.At last, it must be noted that the refractive index of the layers increases with the erbium concentration, leading to the realization of optical guides. Consequently opto-electronic components could be developed from such erbium doped heterostructures.
Reduction of Misfit Dislocation Density in Finite Lateral Size Sil-xGex Films Grown by Selective Epitaxy
Authors: Vescan L. , Stoica T. , Dieker C. , LÜth H. 
Published: March 2011

AbstractIn Si0.88Ge0.12/Si strained layers misfit dislocations formed during growth in small pads are generated at a significantly higher critical thickness than on extended areas, while pads of lateral size of 10 μm or smaller show no evidence of misfit dislocations at all. The SiGe layers investigated were selectively grown on patterned substrates with pad sizes from 2 μm to 1 cm. An elastic relaxation model was used to calculate the pad size dependence of the critical thickness. The main hypothesis of the model is that the density of misfit dislocations is solely affected by the elastic relaxation at the edges of small epitaxial areas. This equilibrium model is able to explain the observed absence of misfit dislocations on small pads, however it predicts a critical thickness for finite sizes much lower than the observed one.
Intrasubband 1.55 μm Electrooptical Modulation in SiGe Asymmetric Quantum Well Structures
Authors: Friedman Lionel R. , Soref Richard A. 
Published: March 2011

AbstractA new, fast, intrasubband 1.55 μm electrooptic modulator in the SiGe/Si/CaF2-on-Si steppedquantum- well system is proposed and analyzed. At electric fields of ±8 V/μm, resonant 1-3 conduction intrasubband absorption is predicted to give 18 dB of optical extinction for narrow-linewidth transitions. We expect this field effect modulator to have microwave response, plus compatibility with Si-based optoelectronic integration.
Photoluminescence Investigations of High Purity Mbe-Grown Sil−xGex/Si Single Quantum Wells
Authors: Wachter M. , Schdffler F. , Thonke K. , Sauer R. , Herzog H.-J. , Kasper E. 
Published: March 2011

AbstractSil-xGex/Si(100) single quantum well samples were grown by MBE with x varying from 18.5% to 36%, well widths Lz from 1.1 nm to 175 nm, and growth temperatures To in the range from 350°C to 750°C. We studied the photoluminescence (PL) properties in detail using Fourier transform spectroscopy. In most of the samples, the dominant and phononresolved SiGe band edge PL exhibits exclusively free exciton luminescence even at sample temperatures as low as 2 K. From the absence of bound excitons we conclude that the background concentration of shallow impurities is low in our SiGe layers. Variation of the growth temperature of the Si cap layer strongly influences the efficiency of the SiGe band edge PL at higher temperatures, whereas the PL efficiency is less affected at T=4 K. This indicates a reduction of the concentration of non-radiative defects in the cap layer when it is grown at higher temperatures. A broad PL band 150 meV below the SiGe bandgap, supposed to be typical for MBE-grown material, is weakly observed in only a few samples. The strength of the broad PL band does not unambiguously depend on the strain energy density in the SiGe layer as recently suggested.
Separation of Nucleation and Crystallization in the Solution-Phase Synthesis of Group IV Quantum Structures
Authors: Heath James R. , Seidler Paul F. 
Published: March 2011

AbstractSolution-phase chemical syntheses are presented for the fabrication of Ge quantum structures, including 0-dimensional dots, 1-dimensional wires, and 2-dimensional platelets. The syntheses, which are based on the reduction of chlorogermanes and organochlorogermanes, are carried out in two steps. Step I, the nucleation step, is done at ambient temperature with a liquid metal reducing agent (NaK) and under the influence of sonication. Step 2, crystallization, is carried out at elevated temperatures and pressures in a sealed bomb. Separation of these two steps is shown to be critical for obtaining size and shape control over the product crystallite.
Mechanical Parameter Extraction Using Resonant Structures
Authors: Elders J. , Tilmans H.A.C. , Bouwstra S. , Elwenspoek M. 
Published: March 2011

ABSTRACTIn order to model and design micromechanical sensors and actuators, it is of crucial importance that thin film mechanical parameters, such as the Young's modulus and the residual stress, are known. In this paper, the parameter extraction method using resonant structures has been used to obtain these data and has been compared with the bulge test. Circular aluminum diaphragms have been used as samples.
Study of Bulk and Film-Substrate Composite Materials Behaviour Under Vickers Indentation By Three-Dimensional Finite Element Simulation
Authors: Wang Haifeng , Bangert Herwig 
Published: March 2011

ABSTRACTThree-dimensional finite element simulation is employed to investigate the general indentation behaviour of bulk materials and corresponding film-substrate systems in Vickers hardness test. MARC™, a routine finite element software package was used on the following samples: bulk aluminium, bulk steel and their respective film-substrate systems, i.e., aluminium on steel as soft film on hard substrate and steel on aluminium as reverse situation. The results are given in two different cross-sectional planes, i.e., through opposite pyramidal edges and perpendicular to pyramidal side faces. In all cases the calculation provides a general view of the deformation characteristics, but also values for material displacement and the extension and shape of the stress fields as well as the plastically deformed zone under load or after load release. The indenter load versus indentation depth relation during loading and unloading are also calculated for all the examples.
The Calibration of the Nanoindenter
Authors: Mccormick N J , Gee M G , Hall D J 
Published: March 2011

The nanoindenter has a tremendous potential for the measurement of mechanical properties of thin films and coatings. Information can be obtained about plastic, elastic and time dependent deformation behaviour. In some cases fracture behaviour of the coatings and the adhesion of the coating to the substrate can also be investigated.Before accurate and reproducible measurements can be made the nanoindenter needs to be suitably calibrated. The magnitude of the uncertainties associated with calibration and their relevance to measurements are also required. Additionally it is important that a thorough understanding of the effect of thermal drift on the measurement process is developed. Traceability of calibration is also an important consideration.The primary areas where calibration is essential are displacement, load and shape of the indenter.
Microstructure Based Modelling of Stress Migration and Electromigration Induced Failure Distributions
Authors: Børgesen P. , Korhonen M. A. , Brown D. D. , Li C.-Y. 
Published: March 2011

ABSTRACTStress and current induced degradation of the interconnects may well define the ultimate limits on device density and total on-chip power in microelectronic circuits. The two damage mechanisms are found to be mutually interdependent in a fashion determined by the line microstructure, as well as by design features such as W-studs and refractory metal back up layers. We have developed a comprehensive model for the synergistic effects of stress migration and electromigration, taking such factors into account. The present work reviews the modelling of the statistical failure distributions, with emphasis on the temperature and current density dependencies, for the case of 'near-bamboo' sub-micron lines.
Mechanical Stress Effects on Electromigration Voiding in a Meandering Test Stripe
Authors: Lowry Lynn E. , Tai Beverly H. , Mattila J. , Walsh LH. 
Published: March 2011

ABSTRACTEarlier experimental findings concluded that electromigration voids in these meandering stripe test structures were not randomly distributed and that void nucleation frequently occurred sub-surface at the metal/thermal oxide interface. The data showed a strong correlation between void area, void growth rate and stripe segment length [1]. The influence of mechanical stress on electromigration damage in these test structures has been examined by applying tensile stresses to both passivated and unpassivated samples. The stress distributions are calculated using finite element analysis for each of the test conditions. The resulting impact on electromigration voiding, as well as mechanical stress voiding, and lateral hillock formation is discussed.
Non-Destructive Evaluation of Strains and Voiding in Passgvated Copper Metallizations
Authors: Vinci Richard P. , Marieb Thomas N. , Bravman John C. 
Published: March 2011

ABSTRACTStress induced voiding in passivated Cu lines was investigated by x-ray strain analysis and in-situ high voltage scanning electron microscope (HVSEM) techniques. Cu lines on a Ta underlayer and Cu lines on an Al underlayer were patterned by a trilayer liftoff technique and passivated with Si3N4. For direct observation of stress voiding, specimens were heated to 350ºC in the HVSEM and then cooled and held at 150ºC. Identical samples were subjected to the same thermal cycle for strain state determination using x-ray techniques. The hydrostatic stress state at each temperature was calculated from the measured strains. Few initial voids were observed after passivation in either sample. After heating to 350ºC and cooling to the dwell temperature, no new voiding was seen in the Ta/Cu lines. Measured hydrostatic strains were half those measured in the Al/Cu lines. Heavy voiding was observed in the Al/Cu lines after cooling to the dwell temperature.
Stress Gradient and Relaxation Measurements in AL and Oxygen-Implanted AL Films.
Authors: Besser Paul R. , Bader Stefan , Venkatraman Ramnath , Bravman John C. 
Published: March 2011

ABSTRACTSynchrotron radiation has been used in the grazing incidence geometry to determine the stress gradients and stress relaxation in 0.6 μm thick Al uniform films. We have examined both pure Al and Al implanted with 3 at % oxygen. The films were cycled between 23°C and 400°C. The surface of the pure Al films was more highly stressed, on average, than the film as a whole, both in tension and in compression. In contrast, the surface of the oxygen-implanted film was relaxed relative to the average film stress in compression but was more stressed in tension. The larger gradient in stress in the implanted films reduces during subsequent thermal cycling. These differences are attributed to the microstructures of the films. The O-implanted film develops a small, non-columnar grain structure and forms small Al2O3 particles during annealing. The small grain size allows diffusional relaxation to occur in compression, relieving the stress in areas close to the film surface.