bluuebunny/crossref_metadata_2025_split huggingface dataset:
Buffer-layer Effect on Mixed-Phase Cells Studied by Micro-Raman and Photoluminescence Spectroscopy
Authors: Hilchey Andrea , Lawyer Chris , Wang Keda , Han Daxing , Yan Baojie , Yue Guozhen , Yang Jeffrey , Guha Subhendu 
Published: April 2011

ABSTRACTWe use micro-Raman and photoluminescence (PL) spectroscopy to study the effects of an a-Si:H buffer layer at the i/p interface of the mixed-phase silicon solar cells. We find that the signature of the crystalline 520 cm−1 mode still appears on the Raman spectrum for the cells with a 100 Å thick a-Si:H buffer layer; but it completely disappears for cells with a 500 Å thick a-Si:H buffer layer. At 80 K, the PL spectral lineshape reflects the features of the electronic states in the band tails. The characteristics of the PL spectra of the mixed-phase cells are a narrower main band than the standard a-Si:H band and an extra low energy band from the grain boundary region. As the thickness of the a-Si:H buffer layer increases, the PL main band becomes broader, and the low energy band is depressed. We find that, after light soaking, the PL main band is slightly broadened for the cells with no a-Si:H buffer layer, almost no change for the cells with a 100 Å thick buffer layer, and a remarkable decrease in total PL intensity for the cells with a 500 Å thick buffer layer. In addition, the PL intensity of the defect band increases after light soaking for the cells with a 500 Å thick buffer layer, where light-induced defect generation in the a-Si:H buffer layer masks the changes in the mixed-phase intrinsic layer. The Raman and PL results are consistent with previous observations of the effect of an a-Si:H buffer layer on the performance and metastability against light soaking for mixed-phase solar cells.
Influence of the Distribution of Tail States in a-Si:H on the Field Dependence of Carrier Drift Mobilities
Authors: Brinza Monica , Emelianova Evguenia V. , Stesmans André , Adriaenssens Guy J. 
Published: April 2011

ABSTRACTExponential distributions of tail states have been able, within the framework of a multiple-trapping transport model, to account rather well for the time-of-flight photoconductivity transients that are measured with ‘standard’ a-Si:H, i.e. material prepared by plasma-enhanced chemical vapor deposition at ∼250°C. A field-dependent carrier mobility in the dispersive transport regime is part of the observations. However, samples prepared in an expanding thermal plasma, although still exhibiting the dispersive transients, fail to show this field dependence. The presence of a Gaussian component in the density of valence-band tail states can account for such behavior for the hole transients. Nanoscale ordered inclusions in the amorphous matrix are thought to be responsible for the Gaussian density of states contribution.
Amorphous Silicon based Solar Cell Technologies: Status, Challenges, and Opportunities
Authors: Arya Rajeewa R. 
Published: April 2011

ABSTRACTAdvances in amorphous silicon solar cell and module development over the past two decades has led to widespread commercial application in consumer and building integrated photovoltaic applications (BIPV). The technology has taken two pathways: (i) superstrate and (ii) substrate. Both pathways have unique advantages over crystalline modules and have demonstrated promising stability and reliability with continuous improvement in performance. Multi-junction modules with amorphous and microcrystalline silicon have demonstrated initial conversion efficiencies in the range of 13%-13.5%.
Hole Drift-Mobility Measurements and Multiple-Trapping in Microcrystalline Silicon
Authors: Dylla T. , Finger F. , Schiff E. A. 
Published: April 2011

ABSTRACTWe present photocarrier time-of-flight measurements of the hole drift-mobility in microcrystalline silicon samples with a high crystalline volume fraction; typical room-temperature values are about 1 cm2/Vs. Temperature-dependent measurements are consistent with the model of multiple-trapping in an exponential bandtail. While this model has often been applied to amorphous silicon, its success for predominantly crystalline samples is unexpected. The valence bandtail width is 31 meV, which is about 10-20 meV smaller than values reported a-Si:H, and presumably reflects the greater order in the microcrystalline material. The hole band-mobility is about 1 cm2/Vs – essentially the same magnitude as has been reported for electrons and for holes in amorphous silicon, and suggesting that this magnitude is a basic characteristic of mobility-edges, at least in silicon-based materials. The attempt-frequency is about 109 s-1; this value is substantially smaller than the values 1011 - 1012 s-1 typically reported holes in amorphous silicon, but the physical significance of the parameter remains obscure.
Enhanced Surface Diffusion in Low-temperature a-Si:H Processing
Authors: Dalakos George T. , Plawsky Joel L. , Persans Peter D. 
Published: April 2011

ABSTRACTGlow discharge amorphous hydrogenated silicon (a-Si:H) prepared at near room temperature typically results in an inhomogeneous morphology that is undesirable for a number of thin film applications. The most commonly observed features of this include columnar morphology and surface roughness. This usually results from anodic deposition, where substrates are placed on the grounded electrode. We have discovered that placing substrates on the RF-powered electrode (referred to as cathodic deposition) offers a much wider processing range for homogenous growth than anodic growth. We have also found that the magnitude of the surface roughness and the bulk void fraction of both anodic and cathodic a-Si:H thin films processed at low-temperatures is proportional to ∼D/F, where D is the surface diffusivity and F, the adatom flux, though anodic and cathodic deposition affect these global parameters differently. Surface processes unique to cathodic deposition can enhance adatom surface diffusion, while diffusion during anodic deposition is fixed and cannot attain homogeneous growth at high adatom fluxes. Processing a-Si:H on the cathode, associated with enhanced adatom surface diffusion, allows for homogeneous growth even at high deposition rates that has benefits for a number of applications.
Non-contact Electrical Measurements of Sheet Resistance and Leakage Current Density for Ultra-shallow (and other) Junctions
Authors: Faifer Vladimir N. , Current Michael I. , Walecki Wojtek , Souchkov Vitali , Mikhaylov Georgy , Van Phuc , Wong Tim , Nguyen Tan , Lu Jiansong , Lau S.H. , Koo Ann 
Published: April 2011

ABSTRACTA novel, non-contact method for determination of ultra-shallow junction sheet resistance and leakage current density has been developed based on monitoring the dynamics of photo-generated carriers by means of spatially separated capacitive probes. At light modulation frequencies of about 100 kHz, spatially resolved surface voltage signals give a direct measure of the junction sheet resistance, independent of the junction depth. At lower light modulation frequencies, the junction leakage current density is determined. Combining capacitive monitoring of modulated photo-generated free carriers with a precision wafer motion stage allows for rapid acquisition of sheet resistance and leakage data for efficient wafer-scale mapping applications.
Electrical profiles of ultra-low energy antimony implants in silicon
Authors: Alzanki T. , Gwilliam R. , Emerson N. , Sealy B. J. , Collart E. 
Published: April 2011

ABSTRACTA novel Differential Hall Effect technique is used to obtain doping profiles of 2keV implants of antimony in <100> silicon at a depth resolution of 2nm. The electrical profiles are compared with atomic profiles determined from Secondary Ion Mass Spectroscopy (SIMS) measurements. We demonstrate good consistency between the two profiling techniques and confirm that the SIMS profiles can be used to identify the junction depth. The profiles show that antimony does not diffuse significantly for annealing temperatures below 800°C.
Atomistic Modeling and Simulation of Impurity Atmosphere in Silicon and Edge Dislocation Locking Effects
Authors: Karoui A. 
Published: April 2011

ABSTRACTA theoretical study of edge dislocation locking by impurities in silicon is presented. Three groups of impurities are considered: (i) light atoms O, N, and C., (ii) large atoms Ga, and Ge, and (iii) small dopant atoms B, P, and Al. Based on impurity size effect model, these three groups produce distinct different dislocation locking effects. Atoms from the first group strongly bind with edge dislocations. The O, N, and C atmospheres are similar, with a slightly stronger occupancy probability for O and N in the vicinity of the dislocation core. For the second group, Ge loosely binds to dislocation and resists at most 1/3 of the separation shear stress that the first group can withstand. Germanium has only a small chance to reach the dislocation core. The third impurity group does not resist shear any separation stress from edge dislocations. Moreover, B and P atoms can not be trapped at all by edge dislocations. At a local atomic fraction of 10−4, edge dislocation-impurity binding energy varies from 0.008 eV/Å for P to 1.7 eV/Å for N and 1. 8 eV/Å for O. In addition, using molecular mechanics on system of 34552 atoms the self-energy of an edge dislocation was calculated and found equal to 156 meV/Å.
Optimization of Dielectric Cap Adhesion to Ultra-Low-k Dielectrics
Authors: Spencer Greg , Soyemi Alfred , Junker Kurt , Vires Jason , Turner Michael , Kirksey Stuart , Sieloff David , Ramani Narayanan 
Published: April 2011

AbstractIn this work, the adhesion of CVD dielectric caps to ULK MSQ spin-on dielectric materials with k values of 2.2 and 2.0, and a ULK CVD material with a k value of 2.7 is presented. A substantial improvement in cap adhesion to both the k2.2 ULK MSQ and the k2.7 ULK CVD material is demonstrated. The improvement is obtained using a low-k CVD glue material between the ULK dielectric and the subsequent cap material and/or by optimizing the CVD cap film deposition. Four-point bend measurement of adhesion strength is used to quantify the improvement in interface adhesion. The improvement in CVD cap adhesion is demonstrated to be strongly dependent upon both the glue layer film and the cap deposition conditions. While optimization of the CVD cap materials results in adequate adhesion for the k2.2 ULK MSQ, these improvements are demonstrated not to extend to the k2.0 ULK MSQ film.
Comparative Studies of Ultra Low-κ Porous Silica Films with 2-D Hexagonal and Disordered Pore Structures
Authors: Fujii Nobutoshi , Yamada Kazuhiro , Oku Yoshiaki , Hata Nobuhiro , Seino Yutaka , Negoro Chie , Kikkawa Takamaro 
Published: April 2011

AbstractPeriodic 2-dimensional (2-D) hexagonal and the disordered pore structure silica films have been developed using nonionic surfactants as the templates. The pore structure was controlled by the static electrical interaction between the micelle of the surfactant and the silica oligomer. No X-ray diffraction peaks were observed for the disordered mesoporous silica films, while the pore diameters of 2.0-4.0 nm could be measured by small angle X-ray scattering spectroscopy. By comparing the properties of the 2-D hexagonal and the disordered porous silica films which have the same porosity, it is found that the disordered porous silica film has advantages in terms of the dielectric constant and Young's modulus as well as the hardness. The disordered porous silica film is more suitable for the interlayer dielectrics for ULSI.
Effect of Mode-Mixity and Porosity on Interfacial Fracture of Low-k Dielectrics
Authors: Merrill Caroline C. , Ho Paul S. 
Published: April 2011

AbstractIn this study, we developed a system allowing interfacial adhesion measurements as a function of mode-mixity, from pure tension to pure shear. Results show that the debonding energy increases, by a factor of 3 to 10, as the amount of shear stress increases, approaching mode II conditions. For low k dielectrics, the debonding energy was found to decrease with increasing porosity and increase with increasing plasticity. The crack propagation is also dependent on mode-mixity.
Effect of Aqueous Solution Chemistry on the Accelerated Cracking of Lithographically Patterned Arrays of Copper and Nanoporous Thin-Films
Authors: Guyer E. P. , Dauskardt R. H. 
Published: April 2011

AbstractThe effect of moisture and aqueous solution chemistry on the rate of crack growth in lithographically patterned arrays of copper and low dielectric constant (LKD) materials is reported. Crack growth in the direction orthogonal to the features is demonstrated to fail at significantly increased loads compared to parallel cracking. Decreasing feature width is also shown to increase the structures resistance to fracture, particularly at reduced loads. The chemical interactions and mechanisms of energy dissipation are discussed.
Effect of Surface Chemistry on the diffusion of Copper in nanoporous dielectrics
Authors: Rodriguez Oscar , Cho Woojin , Saxena Ravi , Achanta Ravi , Gill William N. , Plawsky Oel L 
Published: April 2011

AbstractThis work is aimed at understanding the nature of the interactions between metal interconnects and nanoporous dielectrics in integrated circuits. Electrical testing of MIS capacitors is used to assess Cu diffusion and charge injection in the dielectric in the presence of an electric field. We have found that surface modification of nanoporous silica reveals the importance of chemically bound or adsorbed water species in the dielectric and how they trigger metal diffusion. We propose that a combination of moisture-related species in the dielectric and interfacial oxygen oxidize Cu. The copper oxide acts as a source for Cu ions available for diffusion. A quantitative analysis of Cu drift in nanoporous dielectrics that shows the importance of surface chemistry is presented and the mechanism of metal diffusion and charge injection in nanoporous dielectrics is discussed.
Mortality Dependence of Cu Dual Damascene Interconnects on Adjacent Segment
Authors: Chang C.W. , Gan C.L. , Thompson C.V. , Pey K.L. , Choi W.K. , Hwang N. 
Published: April 2011

AbstractThree terminal ‘dotted-I’ interconnect structures, with vias at both ends and an additional via in the middle, were tested under a variety of test conditions. Failures (mortalities) were observed even when segments were tested under conditions that would not have led to failure in two-terminal structures. Mortalities were found in right segments with jL values as low as 1250 A/cm, which is lower when compared to the immortality condition (jL)cr of 3700 A/cm reported for similar via-terminated structures. Moreover, we found that the mortality of a dotted-I segment is dependent on the direction and magnitude of the current in the adjacent segment. These results suggest that there is not a definite value of the jL product that defines true immortality in individual segments that are part of an interconnect tree. More importantly, the critical jL value for a single segment of Cu interconnects may be reduced or increased by an adjacent segment. Therefore independently determined (jL)cr values cannot be directly applied to interconnects with branched segments, but rather the magnitude as well as the direction of the current flow in the adjoining segments must be taken into consideration in evaluating the immortality of interconnect segments in an interconnect network.
Polymer Based Photodetectors
Authors: Narayan K. S. , Kabra D. , Dutta S. 
Published: April 2011

AbstractRecent developments in our laboratory related to polymer-based light sensors are reviewed. The inherent processibility of the active polymer medium is utilized in the implementation of different designs for the opto-electronic applications. The utility of these devices as sensitive photodetectors, image sensors and position sensitive detectors is demonstrated. The schottky-type layer formation at interfaces of polymers such as polyalkylthiophenes and aluminum accompanied by the enhanced photo-induced charge separation due to high local electric field is tapped for some of these device structures. The sensitivity of polymer-based field effect transistors to light also provides a convenient lateral geometry for efficient optical-coupling and control of the transistor state. The range of these polymer-detectors available with the option of operating in the diode and transistor modes should be an attractive feature for many potential applications.
Nano-Scale Devices Embedded in Self-Supporting Polymer Foils
Authors: Könenkamp R. , Chen J. , Klaumuenzer S. , Engelhardt R. 
Published: April 2011

AbstractSelf-supporting polymer foils of several micrometer thickness have been structured using irradiation by fast heavy ions and subsequent etching. Very deep, well defined nanostructures can be prepared in this way. These can then be used as templates for semiconductor deposition and the fabrication of robust embedded electronic devices. Electron microscopy shows void- filling poly-crystalline growth in the polymer films. Electrical experiments show low sensitivity when mechanical forces are exerted on the foil, suggesting that the embedded nano- devices can be used as reliable sensors in applications with considerable bending of the foils. Two different transistor arrangements will be discussed.
Compositional control and structural properties of ZnSe1-xTex epitaxial films on lattice- matched InGaAs/InP (001) by photoassisted Metal Organic Vapor Phase Expitaxy (MOVPE)
Authors: Yarlagadda Bhanu Prakash , Rodriguez Angel , Li Peng , Ayers John , Jain Faquir 
Published: April 2011

AbstractWe report the growth of ZnSe1−xTex (x < 0.9) epitaxial layers using photoassisted Metal- Organic Vapor Phase Epitaxy (MOVPE) on lattice-matched InGaAs/InP (001) substrates. Ternary compositional control was studied as a function of the gas phase composition, growth temperature (360°C – 400°C) and irradiation (12 mW/cm2 – 48mW/cm2). Compositional and structural data were obtained by x-ray rocking curves from 004 and 044 reflections. Lower growth temperatures increased the relative tellurium incorporation but at the expense of the growth rate.
Dynamics of grain boundary motion at the atomic level
Authors: Merkle K. L. , Thompson L. J. , Phillipp F. 
Published: April 2011

AbstractGrain boundaries (GBs) in polycrystalline materials play a pivotal role in controlling their mechanical and physical behavior. High-resolution electron microscopy (HREM) was used to study thermally activated GB migration in thin films of Al and Au at elevated temperatures (T > 0.5 Tm). Grain boundary engineering via epitaxial templating allowed the manufacture of well-defined grain and interfacial geometries. These techniques enabled the observation of tilt, but also twist and general GBs at atomic resolution in-situ at high temperatures. Surface-energy driven GB migration occurred in general GBs, whereas tilt GB motion was curvature driven. Digital analysis of HREM video recordings have given considerable insight in the dynamics of GB motion at elevated temperatures. It is not surprising that the complex and diverse migration mechanisms depend on GB geometry as well as on interatomic interactions. The results provide, among others, direct evidence for collective effects by concerted atomic shuffles, ledge propagation in (113) symmetric tilt GBs, and motions of triple junctions at elevated temperatures.
In-Situ Investigation of Grain Boundary Mobility and Character in Aluminum Alloys in the Presence of a Stored Energy Driving Force
Authors: Taheri Mitra L. , Rollett Anthony D. , Weiland Hasso 
Published: April 2011

AbstractThis paper investigates the effect of solute in Al alloys on grain boundary character and mobility based on experiments in which individual boundaries migrate under a stored energy driving pressure acquired from prior plastic strain; among those studied are Zr, Fe and Si. A compensation effect is noted for both alloys studied with respect to both temperature and solute content. As supported by the literature, boundaries exhibit a maximum mobility for a 38-39°<111> misorientation in initial annealing experiments; this mobility maximum is asymmetric with a sharp cutoff below 38-39° but a more gradual decrease at misorientations beyond 40°. The presence of a minimum at 38-39° is found at both higher temperatures and higher solute concentrations. A shift in texture dependency with solute and temperature is also observed. This transition from a local mobility maximum to a minimum is discussed within the context of recent developments in solute drag theory.
Optical characterization of hierarchically self-assembled GaAs/AlGaAs quantum dots
Authors: Marabelli F. , Rastelli A. , Schmidt O. G. , Beaurin G. , Geddo M. , Guizzetti G. 
Published: April 2011

ABSTRACTRecently, a simple method has been developed to obtain inverted GaAs/AlGaAs quantum dots (QDs) below a quantum well (QW) via multi-step (hierarchical) self-assembly [1]. Here we report on the optical characterization of a series of structures GaAs QDs with different size. The study is performed by means of reflectance (R) down to T=15 K, photo- and thermo-reflectance (T>80 K) and by spectroscopic ellipsometry (at RT). Such measurements allow us to check the thickness and composition of the barrier layers and to complete the study of the electronic states involved in the emission properties of QDs and QW levels. QW states were well identified and their energies and shift with the size parameters well agree with the photoluminescence (PL) data. The identification of QD states seems less straightforward in R measurements and deserves further investigation.
Nitrogen induced optical phonon shift in GaNyAs1-y studied by Raman Scattering
Authors: Tay Li-Lin , Lockwood David J. , Gupta James A. 
Published: April 2011

ABSTRACTWe present a Raman study of pseudomorphically strained epitaxial films of the ternary alloy GaNyAs1-y grown on GaAs(100) with y ranging from 0 to 0.06. The optical phonon Raman spectrum of the alloy displays a two-mode behavior. The GaAs-like first order modes for y = 0.06 are represented by the strong longitudinal optic (LO1) mode at 287.4 cm-1 and the weaker transverse optic (TO1) mode at 269.0 cm-1, while the GaN-like LO2 mode is observed at 475.6 cm-1. Two very broad disorder-induced acoustic bands are evident at 80 and 170 cm-1 due to atomic disorder within the crystalline network. Raman studies show that as the nitrogen concentration in the alloy increases, the GaAs-like LO1 band shifts linearly towards lower wavenumber while the linearly increasing GaN-like LO2 phonon band deviates from linearity at higher nitrogen concentration (y ≥ 0.03). The reason for the deviation of the LO2 phonon from linearity is discussed.
Improved performance of GaSb-based MIR photodetectors through electrochemical passivation in sulphur containing solutions
Authors: Piotrowska A. , Papis E. , Golaszewska K. , Lukasiewicz R. , Kaminska E. , Piotrowski T. T. , Kruszka R. , Kudla A. , Rutkowski J. , Szade J. , Winiarski A. , Wawro A. , Aleszkiewicz M. 
Published: April 2011

ABSTRACTSulfur passivation effects on the performance of LPE-grown GaSb/InGaAsSb/AlGaAsSb mesatype photodiodes operating in wavelengths range 1.9 – 2.3 μm have been investigated. (NH4)2S, Na2S, and (NH2)2CS have been chosen as sulfur sources in either aqueous or C3H7OH solutions. Electrochemical passivation of mesa side walls was proven to reduce photodiodes dark current and increasing their differential resistance by a factor of 4. As a result devices characterized by the detectivity of 1.5–2×1010 cmHz1/2/W and dark current density of 20 mA/cm2 at –0.5V bias have been fabricated and their long-term stability has been proven.