bluuebunny/crossref_metadata_2025 huggingface dataset:
The Role of Deep Defect Relaxation Dynamics in Optical Processes in Hydrogenated Amorphous Silicon
Authors: Zhong Fan , David Cohen J.
Published: April 2011

We report results of a transient modulated photocurrent technique which allows us to observe the time evolution of the D0 sub-band under the application of optical bias light and after turning off this bias light Our measurements show that the D0 band shifts monotonically to shallower thermal energies after the bias light is applied, with roughly 10 seconds to saturation at 300K and to deeper thermal energies after removing the bias light, with a decay time of over 1000 seconds. We have also found there exists an intimate relation between the motion of the D0 band and that of the quasi Fermi level as deduced from the transient photoconductivity and therefore, in particular, to the long time photoconductivity decay. This relation is exactly reproduced by the assumption of a D0 band whose energy position evolves in time, together with a recombination process dominated by changes in the charge state of a deeper defect band under light bias.
Origin of Photodegradation in a-Si:H - Bond Breaking or Charge Trapplng?
Authors: Shimizu Tatsuo , Kumeda Minoru , Zhang Qing , Zhang Jinyan , Ohtsuka Toshihiro
Published: April 2011

In order to clarify the microscopic origin of the photodegradation in a-Si:II, two kinds of approaches have been done. One approach is to carry out the light soaking both at room temperature (RT) and 77 K to cause the photodegradation and to investigate the recovery by thermal annealing. The other approach is to investigate the light-induced ESR in hydrogenated amorphous silicon-nitrogen alloys (a-Si1-xNx:H) and to see the x-dependence down to x = 0. From the first approach, it is found that there is a very broad continuous distribution of annealing activation energies from a few eV through 1.4 eV. It appears less likely that such a wide distribution of annealing activation energy is related with the bond-breaking model. On the other hand, it is found from the second approach that there exist two distinct origins for the light-induced spins, the fast process and the slow process, which are likely to be the carrier capture and the bond breaking, respectively. From the continuation of the observed behavior to a-Si:H, that is, x = 0 in a-Si1-xNx:H, the RT photodegradation in a-Si:H appears to be the bond breaking.
Thermodynamics and Kinetics of Hydrogen Evolution in Hydrogenated Amorphous Silicon Films
Authors: Sridhar Nagarajan , Chung D. D. L. , Anderson W. A.
Published: April 2011

The enthalpy (endothermic) of hydrogen evolution from p-type (boron doped) amorphous silicon with 17 at. % H was 4.8, 10.3, 15.8 and 17.3 kJ/g, the evolution temperature was 585, 606, 625 and 644 °C and the entropy of evolution was 5.6, 11.7, 17.5 and 18.9 J/g.K at heating rates of 5, 10, 20 and 30 °C/min respectively. That the enthalpy and entropy increased with heating rate means that the evolution involves not only Si-H bond breaking, but also Si-Si bond breaking and other defect formation. The Si-Si bond breaking and defect formation were enhanced at high heating rates, which caused high rates of hydrogen evolution. For n-type (phosphorous-doped) and intrinsic amorphous silicon with 25 and 23 at. % H respectively, the enthalpy and entropy of hydrogen evolution were higher than the p-type case, due to severe defect formation resulting from the higher hydrogen content. The activation energy of hydrogen evolution was 1.38, 2.5 and 4 kJ/g for the p-type, intrinsic and n-type materials respectively. Crystallization which occurred at temperatures higher than hydrogen evolution, was delayed for the amorphous silicon film in a higher disordered state after hydrogen evolution, suggesting that hydrogen evolution influenced the crystallization process.
Thermal Equilibrium Processes in a-Si:H Solar Cells
Authors: Lee Jae-Hee , Koh Jae-Seog , Jang Jin
Published: April 2011

Hydrogenated amorphous silicon (a-Si:H) solar cells are prepared by plasma enhanced chemical vapor deposition (PECVD). Before quenching the solar cells, the short circuit current (Jsc), open circuit voltage (Voc), fill factor (F. F.) and conversion efficiency (η) are 17.79 mA/cm2, 0.79 V, 53.29, and 7.49 %, respectively. After thermal quenchine the solar cells from 200°C, Jsc, Voc, F. F., and η are 18.64 mA/cm2, 0.8 V, 53.79, and 8.02 %, respectively. We investigated the thermal equilibrium processes of each P, I, and N layers. Also, we obtained the dark current-voltage characteristics of a-Si:H solar cells before and after quenching. We analyze the results in terms of the change of the internal electric field in a-Si:H solar cells, caused by the shift of the Fermi level of P layer toward valence band.
Light-Induced Changes Among Fast-Relaxing Hydrogens in Plasma-Deposited Hydrogenated Amorphous Silicon
Authors: Kernan M. J. , Corey R. L. , Fedders P. A. , Leopold D. J. , Norberg R. E. , Turner W. A. , Paul W.
Published: April 2011

Light-induced rearrangements in a-Si:H,D during and after illumination have been studied by deuteron magnetic resonance (DMR). A film sample was deposited on a 230°C Al substrate by plasma decomposition of S1H4 and D2. The high quality film contained 4 at.% H and 4 at. % D. DMR spectra of fast-relaxing components were examined at 700 msec or less after radio frequency saturation. At 30 K these showed a broad central signal (primarily nanovoid-trapped HD and D2), part of which shifted paramagnetically during illumination. No comparable shifts were shown by spectral components from Si-bonded hydrogen or from microvoid-contained dense fluid hydrogen. The observed post-illumination shifts vanished upon 150°C dark anneal and reflected light-induced metastable magnetic changes in the surroundings of hydrogen trapped in nanovoids.
Optoelectronic Properties of High-Gap Amorphous Silicon-Carbon Alloys
Authors: Chu V. , Conde J. P. , Brogueira P. , Micaelo P. , Jarego J. P. , da Silva M. F. , Soares J. C.
Published: April 2011

The dependence of the properties of hydrogenated amorphous silicon-carbon alloys deposited with a 1:10 silane (SiH4) to methane (CH4) or ethylene (C2H4) gas flow ratios with the hydrogen dilution, deposition pressure and power is studied. In methane-based films the carbon content shows a decrease (from ≈0.75 to 0.55) with increasing hydrogen dilution from 0 to 98%, while the ethylene-based films show no dependence of the carbon fraction (≈0.9) on hydrogen dilution. The photoconductivity shows an increase for hydrogen dilutions above 90= for both methane and ethylene-based films. While this increase is attributed, in the case of methane, to the observed decrease in carbon content, no corresponding decrease in carbon content is observed in the ethylene-based films, suggesting a decrease in the density of recombination centers with hydrogen dilution. The Urbach tail and the room-temperature photoluminescence peak correlate with carbon content independent of the carbon source-gas and deposition conditions used.
Thermopower and 1/f Noise Measurements in Amorphous Silicon-Carbon Alloys
Authors: Dyalsingh H. M. , Khera G. M. , Kakalios J.
Published: April 2011

Thermopower, conductivity and 1/f noise measurements have been performed on a series of n-type doped hydrogenated amorphous silicon carbon films that are prepared with varying gas phase concentrations of CH4. The increased disorder at the mobility edge associated with alloying is characterized by the Q-function, which is obtained by combining thermopower and conductivity measurements, and is also reflected in the noise power spectra and noise statistics.
Spectral Response of a-Si:H p-i-n Solar Cells Degraded by Blue and Red Light
Authors: Mittiga A. , Mariuc L. , Fasolino T. , Romano A. , Fiorini P. , Bonito P.
Published: April 2011

We have degraded a-Si:H p-i-n solar cells at Voc using both red and blue light to investigate the effect of a possible different spatial distribution of defects in the intrinsic layer. We have found that the I-V and the spectral response curves of the degraded cells depend on the total density of defects only and are not sensitive to the wavelength of the degradation light. These experimental results and some peculiar features of the spectral response of the degraded cells are explained with the aid of a numerical simulation program.
Fabrication of Undoped and N+ Microcrystalline si Films Using SiH2Ci2
Authors: Byun Jae Seong , Jeon Hong Bin , Jun Jung Mok , Yoo Jae Ho , Lee Kyung Ha , Park Min , Jang Jin
Published: April 2011

We have studied the growth of undoped and n+ μc-Si:H (:CI) films by Remote Plasma CVD using SiH4/SiH2Cl2/H2/He mixtures. It was found that the μc-Si film can be fabricated by increasing flow rate of SiH2Cl2 and/or H2. The deposited undoped μc-Si film exhibited a maximum crystalline volume fraction of 85 %, obtained from Raman spectroscopy. The n-type μc-Si film, deposited with SiH4/SiH2Cl2/H2/PH3/He mixtures, shows a room temperature conductivity of 2 S/cm, conductivity activation energy of 29.8 meV and optical band gap of-2.0 eV. The optical band gap of n-type μc-S1 deposited using SiH2Cl2 is much higher compared to conventional μc-Si film.
c-Si (n +)/a-Si Alloy/Pd Schottky Barrier Device for the Effective Evaluation of Photovoltaic Performance of a-Si Alloy Materials
Authors: Deng X. , Jones S. J. , Evans J. , Izu M.
Published: April 2011

The Schottky barrier device with a metal/a-Si (n+) /a-Si alloy/metal structure has been widely used as an alternative evaluation tool for the photovoltaic performance of a-Si alloy material since it more reliably reflects the carrier transport in a solar cell than the conventional material characterization tool such as PDS, CPM, and SSPG, and is easier to be fabricated compared with a complete nip solar cell. However, a multiple chamber device making system is still needed to fabricate such a device since one does not want to deposit the a-Si intrinsic material to be studied together with an n+ layer in the same chamber. We have explored the use of a Schottky barrier device deposited on heavily doped n-type crystalline wafer substrate, c-Si (n+) /a-Si alloy/metal, as an evaluation tool for a-Si alloy materials. In this device, besides the evaporation of a thin semi-transparent metal layer, only the active a-Si alloy layer needs to be deposited using the plasma enhanced or other deposition techniques. We have compared the performance of such a device with that of reference n-i-p solar cells deposited at the same time and demonstrated that the FF measured under weak red light show a good correlation between these two types of devices. Therefore the c-Si (n+) /a-Si alloy/metal device can be used as a convenient technique to reliably evaluate the material performance in a solar cell device.
Properties of Glass Substrates for Poly-Si Amlcd Technology
Authors: Moffatt Dawne M.
Published: April 2011

A major force for change in substrate requirements in the late 90's may well be the commercialization of poly-silicon thin film transistor (TFT) Active Matrix Liquid Crystal Display (AMLCDs) technology. The processes necessary for “poly-Si” occur at temperatures that are 150–300°C higher than the current amorphous-Si LCD processes. This impacts the thermal shrinkage and thermal gravimetric warp requirements of the glass, particularly as display resolutions tighten, as enabled by poly-Si. In addition, the expected integration of more components (e.g. chip-on-glass) impacts the requirements for the thermal expansion of the substrate.

One approach for meeting the poly-Si demands for greater thermal-dimensional stability is to use glasses with higher temperature capability. A new glass, Code 1737, with the highest strain point commercially available at over 660°C, now enables poly-Si processing with acceptable sag and shrinkage after annealing. A logical goal for the next significant glass advancement would be to eliminate annealing altogether, but it is unclear what temperature capability is required. In this study, various glasses with strain points ranging from 600–800°C have been evaluated in terms of their density, thermal expansion, and thermal shrinkage following poly-Si thermal process simulations. It has been confirmed that the magnitude of shrinkage decreases with increasing strain point for glasses in this compositional family. In addition, future new insight into the effect of thermal expansion coefficient has been developed; the lower the thermal expansion coefficient (for a given strain point), the lower the magnitude of the shrinkage for a given strain point and high temperature thermal cycle. This is important new learning in the area of substrates for flat panel displays that will help in further design and development of glasses for future AMLCDs.
Sulfidization in Alcoholic Solutions: A New Surface Passivation Method for GaAs
Authors: Bessolov Vasily N. , Ivankov Andrew F. , Konenkova Elena V. , Lebedev Mikhail V.
Published: April 2011

A new approach to GaAs surface passivation is suggested which consists in the treatment of GaAs in sulfide solutions in which different alcohols are used as solvents. It has been found that the photoluminescence efficiency of sulfide-treated GaAs associates with the dielectric constant of the solvent being used. With the decrease of dielectric constant value the PL intensity of sulfidized GaAs increases. Sulfidizing in isopropanol-, butanol- or t-butanol-based solutions leads to the formation of sulfide coat which PL properties remain constant even after strong laser irradiation. The effect of the solvent on the GaAs PL efficiensy is explained whithin the framework of hard and soft acids and bases. Thus the use of alcohol-based sulfide solution with low dielectric constant value greatly reduces surface recombination losses in sulfide-treated GaAs.
Effects of Additive Elements on Electrical Properties of Tantalum Oxide Films.
Authors: Fujikawa Hisayoshi , Taga Yasunori
Published: April 2011

Ta2O5-based composite films prepared by magnetron sputtering have been investigated with respect to their dielectric properties. As additive third oxides, Y2O3 and WO3 were found to be effective in improving insulating properties without decreasing their dielectric constant. Furthermore, electrical properties of Ta2O5-Y2O3 films were investigated by measuring the current-voltage characteristics in the temperature range from 100 to 330 K. Measurement of temperature dependence of the leakage current revealed that the conduction mechanism at RT changed from the Poole-Frenkel type to the Fowler-Nordheim tunneling type by adding Y2O3 into Ta2O5. Based on the detailed analysis of the results, it is concluded that the addition of Y2O3 into the Ta2O5 film is effective in the reduction of defect density without high-temperature annealing and the alteration of electrical conduction mechanisms of the films.
Investigation of Free Exciton Properties in GaAs Epitaxial Layer
Authors: Fengmei Wu , Yi Shi , Parenteau Martin , Jorio Anouar , Youdou Zheng , Carlone Cosmo
Published: April 2011

The transition energy, the binding energy, the intensity, the broadening and the lifetime of the free-exciton transitions in GaAs epitaxial layer have well been investigated using photoconductivity measurement which is analyzed in term of an improved fitting model. We have found that as the thickness is increased, the bind energy increases, but both the intensity of the high excitonic level and the lifetime of the excitons decrease. These effects are attributed mainly to imperfections located near the surface of the epitaxial layer.
Transient Diffusion and Gettering of Au and Cu to Cavities in Si
Authors: Wong-Leung J. , Williams J. S. , Nygren E.
Published: April 2011

This paper addresses the diffusion and gettering of Cu and Au to internal cavities in Si introduced by H-implantation. Rutherford backscattering and channeling and cross-sectional transmission electron microscopy are the main analysis methods used. During annealing at temperatures and times typical of low temperature device processing conditions, we observe a transient gettering regime in which implanted Au and Cu segregate to cavities leaving metal concentrations in the Si lattice well below the solubility level. Longer times and/or higher temperatures are required for equilibrium to be reached. These results may have important implications for developing optimum gettering strategies during thermal processing of device structures.
Analysis of Dislocation Networks and Electronic Properties of Dendritic Web Silicon
Authors: Morelhão S. L. , Meier D. L. , Neugebauer G. T. , Bathey B. B. , Mahajan S.
Published: April 2011

During the growth of dendritic web silicon, an ideal material for fabrication of high efficiency solar cells, a thin ribbon of silicon single crystal is obtained. Due to thermal stresses characteristic in this growth process, dislocations and residual stresses are observed in most ribbons. In this study, transmission X-ray topography was used for analyzing dislocation networks in as-grown web silicon. We were able to correlate minority carrier diffusion length with the configuration of the networks that are strongly affected by twin planes lying midway across the web thickness. Analysis of the networks is also useful in providing information regarding regions of high stress levels associated with a given growth environment.
Order and Disorder in Semiconductors
Authors: Queisser Hans J.
Published: April 2011

The astounding success of microelectronics rests on a simple materials principle : creating a highly purified and perfected , spatially ordered semiconductor matrix , whose electrical and optical properties may be selectively adjusted by local substitutions of host atoms by dopant atoms. This unique materials utilization differs remarkably from all earlier technologies , because the controlled, almost imperceptibly small disorder by doping (rather than the ordered host ) dominates the relevant properties ! Defect control is thus a major concern for semiconductor technology. Homogeneity is an absolute necessity for this strategy, but only a few of the semiconductors can be made so homogeneous as to suppress the strong deleterious effects of inhomogeneity. Recent advances are summarized : atomic resolution of defect analyses, multiatom reactions and hope for applications,contactless measurements, gettering as well as detailed theory of simulations. The emergence of novel quantum devices, with both reduced dimensions and reduced dimensionalities heralds a paradigm change, since the quantizing small geometries exert stronger influences than defects do; nevertheless, materials perfection and interface control remain prerequisites for these structures.
Deep Level Defects in GaN Characterized by Capacitance Transient Spectroscopies
Authors: Gütz W. , Johnson N. M. , Street R. A. , Amano H. , Akasaki I.
Published: April 2011

Electronic defects in MOCVD-grown n-type GaN were characterized by conventional deep level transient spectroscopy (DLTS) and by photoemission capacitance transient spectroscopy (O-DLTS) performed on Schottky diodes. With DLTS two deep levels were detected with thermal activation energies for electron emission to the conduction band of 0.16 eV and 0.44 eV. With O-DLTS we demonstrate four new deep levels with optical threshold energies for electron photoemission of ∼ 0.87 eV, 0.97 eV, 1.25 eV and 1.45 eV. The O-DLTS apparatus and the measurement are discussed in detail. We also report characterization of the Au-GaN barrier height of the Schottky diode by internal photoemission.
Relation Between Structure and Carrier Lifetime in As-Implanted GaAs
Authors: Liliental-Weber Z. , Swider W. , Kagiichi H. , Claverie A. , Wang H. H. , Whitaker J. F.
Published: April 2011

The structure of As implanted GaAs layers before and after annealing are described and the relation between the structural quality and carrier lifetime was determined. Subpicosecond carrier lifetimes were found already for as-implanted layers, and this value changes only slightly after annealing in the temperature range up to 600°C. Annealing of As-implanted layers leads to the growth of As precipitates with a similar orientation relationship as those observed in low-temperature MBE-grown GaAs layers. However, it is still not clear whether point defects created by implantation or the As precipitates are responsible for the short carrier lifetime.
Radiative Recombination Processes in Boron Modulation-Doped SiGe Quantum Wells
Authors: Buyanova I. A. , Chen W. M. , Henry A. , Ni W. X. , Hansson G. V. , Monemar B.
Published: April 2011

The radiative recombination processes of the two-dimensional hole gas formed in SiGe quantum wells (QWs) due to modulation doping are studied in details by photoluminescence (PL) spectroscopy. Boron-modulation-doped Si/Sil−xGex/Si heterostructures grown by molecular beam epitaxy (MBE) are studied. It is shown that charge transfer of holes from the doped Si layers causes the filling of the SiGe QWs leading to an appearance of a broad asymmetric PL band with a characteristic sharp high energy cut-off and enhanced recombination near the Fermi edge. A reduction of this PL enhancement is observed with an increase of measuring temperature. The PL bandwidth and the high energy cut-off are found to vary with either the doping level or the spatial separation between the delta-doped layers and the QWs. This PL band is argued to arise from the recombination of the holes in the QWs and electrons confined near the QWs as a result of the band bending induced by the delta-doping. The shape of the PL band with enhanced intensity near the Fermi edge are discussed in terms of the phase space filling and many-body effects.
Introduction of Radiative Isoelectronic Complexes During Molecular Beam Epitaxial Growth of Si and Si1-xGex/Si Superlattices
Authors: Moore Karen L. , King Oliver , Hall Dennis G. , Bevk Joze , Furtsch Matthias
Published: April 2011

Radiative isoelectronic impurity complexes consisting of pairs of Be atoms that bind excitons can be formed in both Si and SiGe/Si superlattices during growth by molecular beam epitaxy. We describe the conditions under which these radiative complexes can be formed and show that they can be localized in the alloy layers of a superlattice. Experimental results from samples with grown-in Be are compared to previous results from ion implanted samples. Superlattices of varying well widths are examined and a narrowing of the no-phonon linewidth is observed.
The Kinetics of Capture and Emission of Discrete DX Related Centers in Silicon Doped AlGaAs Using Time Analyzed Transient Spectroscopy
Authors: Agarwal Sandeep , Mohapatra Y. N.
Published: April 2011

The kinetics of multiple DX related emission centers are studied using the isothermal Time Analyzed Transient Spectroscopy (TATS) of constant capacitance voltage transients. Four distinct emitting centers have been obtained using higher order TATS in the same silicon doped Al0.33As0.67As sample without use of hydrostatic pressure. Accurate identification of the multiple DX states has allowed a better understanding of the charge redistribution process during capture. Improved resolution due to increase in order of spectroscopy has enabled quantitative fitting of spectral lineshape and thus accounting for degree of nonexponentiality associated with each of the four discrete centers. The capture kinetics of these centers are studied over six orders in magnitude of filling time. The resulting quality of kinetic data makes possible detailed quantitative comparison with kinetics predicted by positive U and negative U models of DX centers. We show that our data is in agreement with positive U model of DX center.
Adjacent Layer Composition Effects on Fetbco Thin Film Magnetic Properties
Authors: Hintz Michael B.
Published: April 2011

The magneto-optical (MO) layer in current rare earth-transition metal (RE-TM) based MO recording media is typically 20 nm to 60 nm thick. It has been suggested, however, that media structures employing a multiplicity of thinner MO layers may be advantageous, e.g., for multilevel recording applications [1] or media noise reduction [2]. As magnetic layer thickness is reduced, interactions among magnetic layers and adjacent materials can have an increasingly large influence on magnetic properties; in many instances, these interactions can dominate the observed magnetic behavior.

As a means of studying MO layer - adjacent layer interactions, we have used thin (≈3 nm) films of several materials to separate single 24 nm thick ion-beam-deposited FeTbCo layers into N thinner layers of 24/N nm thickness (N × 24/N). As N increases, the FeThCo magnetic properties generally change; however, the relative magnitude of the changes is strongly dependent upon the adjacent layer composition. Magnetization (Ms), energy product (MsHc) at 30 C and Curie temperature data for 1 × 24 nm structures and 6 × 4 nm structures are compared and discussed for specimens employing SiCx, Six, YOx, HfOx, Si and SiOx adjacent layer materials.
Interlayer Coupling in Magnetic/Pd Multilayers
Authors: Shi Zhu-Pei , Klein Barry M.
Published: April 2011

The Anderson model of local-state conduction electron mixing is applied to the problem of interlayer magnetic coupling in metallic multilayered structures with palladium (Pd) spacer layers. An oscillation period of 5 spacer monolayers and the tendency towards ferromagnetic bias of the interlayer magnetic coupling that we obtain are consistent with the experimental data.
Crystal Structure Dependence of Antiferromagnetic Coupling in FE/SI Multilayers
Authors: Michel R. P. , Chaiken A. , Wall M. A.
Published: April 2011

Recent reports of temperature dependent antiferromagnetic coupling in Fe/Si multilayers have motivated the generalization of models describing magnetic coupling in metal/metal multilayers to metal/insulator and metal/semiconductor layered systems. Interesting dependence of the magnetic properties on layer thickness and temperature are predicted. We report measurements that show the antiferromagnetic (AF) coupling observed in Fe/Si multilayers is strongly dependent on the crystalline coherence of the silicide interlayer. Electron diffraction images show the silicide interlayer has a CsCl structure. It is not clear at this time whether the interlayer is a poor metallic conductor or a semiconductor so the relevance of generalized coupling theories is unclear.
Surface Anisotropy in Epitaxial FE(110)/MO(110) Multilayers
Authors: Osgood R.M. , White R.L. , Clemens B.M.
Published: April 2011

We have prepared epitaxial Fe(110)/Mo(110) multilayers by sputter deposition. These films exhibit a large uniaxial anisotropy and may be attractive as islanded in-plane recording media. The large uniaxial anisotropy is due to the intrinsic surface anisotropy of the Fe(110)/Mo(110) interface, which is of the same magnitude as the surface anistropy of the Fe(110)/W(110) interface but has a different sign (the surface anisotropy of the Fe(110)/Mo(110) interface prefers the [001] axis of magnetization). The magnetoelastic component of the anisotropy is not large. A novel magneto-optic technique was used to measure the transverse component of the magnetization and deduce information about the anisotropy and domain structure of the multilayers.
Studies On Magnetic Configurations In Multilayers by A Quantum Spin Model
Authors: Kawazoe Yoshiyuki , Takahashi Manabu , Hu Xiao , Tao Ruibao
Published: April 2011

A method based on the variation of the magnetization direction of each layer and Holstein- Primakoff transformation is presented to estimate the magnetization configuration in a superlattice of quantum ferromagnetic system with an interface between perpendicular and in-plane easy-axis layers. Numerical results on the magnetization configurations under different applied magnetic fields, critical field, and critical anisotropic parameter are given.
Epitaxial Growth of (111) TbFe2 by Sputter Deposition
Authors: Wang C.T. , Osgood R.M. , White R.L. , Clemens B.M.
Published: April 2011

The effect of in-plane strain in (111)-oriented epitaxial TbFe2 films on the magnetization orientations was studied. Magnetocrystalline anisotropy, shape anisotropy, and magnetoelastic energy were calculated to determine the magnetization orientation in the presence of various in-plane strains. Theoretical considerations indicate that a compressive strain smaller than -0.065% can induce an out-of-plane magnetization. DC magnetron sputtering from Tb and Fe elemental targets was used to grow 50, 100, 200, and 400 Å thick epitaxial TbFe2(111) films at 600°C on (110)-oriented sapphire substrates with 1000 Å thick epitaxial Mo(110) buffer layers. The growth rate of the TbFe2(111) films was 1.44 Å/sec. X-ray diffractometry, Rutherford backscattering spectrometry, and vibrating sample magnetometry were used to characterize the crystal structure, epitaxial orientation, composition, stress and strain state, and magnetic properties of the TbFe2 films. The TbFe2(111) films were epitaxial with twins rotated by 60° and were in tensile strain states with the resulting in-plane magnetization.
Growth and Characterization of Fept Compound thin Films
Authors: Visokay M.R. , Sinclair R.
Published: April 2011

FePt alloy films were deposited at 50 and 49°C onto amorphous SiO2 and single crystal [001] MgO and [0001] Al2O3 using DC magnetron cosputtering, resulting in polycrystalline and [001] and [111] epitaxial films, respectively. High temperature deposition resulted in ordered films with the tetragonal Ll structure and out-of-plane magnetic easy axes while low temperature deposition yielded chemically disordered fcc alloys with in-plane easy axes. Significant modification of the magneto-optic Kerr spectrum is observed for ordered relative to disordered alloys for all orientations. The Kerr rotation has a strong orientation dependence for the ordered, but not disordered films.
Structure and Magnetism in Mo/Co Multilayers
Authors: Foiles C.L. , Franklin M.R. , Loloee R.
Published: April 2011

The magnetic and structural properties of Co in Mo/Co multilayers are an unresolved issue. Two independent studies report different structures for thicker Co layers in multilayers of comparable dimensions as well as significant differences in both the form and the layer thickness for a loss of ferromagnetism. Both studies base their structural claims on a limited number of Bragg lines. We have used x-ray diffraction, transmission electron diffraction, and EXAFS to probe the structure of Mo/Co multilayers having Co layer thicknesses from 4 to 63Å. Our structural and magnetic results for these samples are compared to those of the above studies and are contrasted with results for Mo/Fe multilayers having comparable dimensions.
In-Situ XPS Study of the Aluminum Poly(p-Phenylenevinylene) Interface
Authors: Konstadinidis K. , Papadimitrakopoulos F. , Galvin M. , Opila R.
Published: April 2011

The chemical and electronic properties of aluminum/poly(p-phenylenevinylene) (PPV) interfaces were studied in situ using x-ray photoelectron spectroscopy (XPS). It was observed that the aluminum atoms react with the oxygen-containing groups present as impurities on the surface of PPV to form Al-O-C linkages. The Al atoms also interact with the wrsystem of the polymer as indicated by changes in the valence band. Contrary to to recent suggestions (Ettedgui et al.) the relation between surface oxygen content and band bending is not straightforward, as shown by deposition on PPV surfaces prepared by two different synthetic routes.
Effects of Surface Modification on the Structure of Adsorbed Block Copolymer Monolayers
Authors: Pai-panandiker Rahool S. , Dorgan John R.
Published: April 2011

Improving the processing and formability of ceramic components prior to firing (as green bodies) requires an enhanced understanding of how the polymeric binder components function. We report on the role of surface energetics on the structure of the copolymeric monolayers formed via adsorption from solution. Also, results on the effects of surface energetics on the kinetics of the adsorption are reported. A silicon wafer with an oxide layer is used as the surface and adsorption takes place from toluene. Surface energetics are varied by treatment of the oxide surface with a series of silane coupling agents which contain either amine, epoxide, or vinyl functional groups. The block copolymers used consist of relatively short poly(ethylene oxide) (PEO) blocks and much longer polystyrene (PS) blocks. Ellipsometry is used to determine the grafting density, σ (chains/nm2), and Fourier Transform Infrared spectroscopy is used to investigate the copolymer on the surface. It is seen that the time required to reach equilibrium increases as the strength of the interaction between the copolymer and the surface increases. Also, the diblock copolymers appear to obey the scaling laws proposed by Marques and Joanny on all the surfaces studied. ( i.e., σ ∝ 1/NA, when the copolymer is symmetric or moderately symmetric and σ ∝ 1/β2, when the copolymers are asymmetric, where NA is the number of segments of the adsorbing block and β is the ratio of the size of the nonadsorbing block to that of the adsorbing block.)
XPS Study of Buried Metal/Polymer and Polymer/Metal Interface
Authors: Wu P. K.
Published: April 2011

Metal/Polymer systems have potential applications as interconnect materials in integrated circuits. Polymers with low dielectric constants, if used as interlayer dielectric, can reduce the RC time constant. Device speed can be doubled if a polymer can replace the present dielectric material, SiO2. However, the problem of weak metal/polymer adhesion must be understood and resolved. In situ deposition and analysis are the most controlled means to study an interface formation process. However, for practical reasons, i.e., application, time, cost, and flexibility, it is critical to study metal/polymer interface ex situ. X-ray Photoelectron Spectroscopy (XPS), can be used to determine the composition and bonding structures of buried interfaces. This is achieved by examining peeled surfaces, thin overlayer, and lowenergy- ion sputtered surfaces. The possible adhesion mechanism or failure mode is determined by correlating XPS results with adhesion strength. Based on these results, adhesion enhancement methods, such as substrate surface treatments, can be formulated. The product of these treatments can be evaluated using the same analysis. These techniques for studying buried interfaces using XPS are reviewed and results of their applications to the metal/Teflon AF 1600 interface is presented.
Post CMP Cleaning Using Ice Scrubber Cleaning
Authors: Takenaka N. , Satoh Y. , Ishihama A. , Sakiyama K.
Published: April 2011

The surface cleaning technology with the use of ice scrubber cleaning has been developed to remove the particles after Chemical Mechanical Polishing (CMP) process. The ice particles with a high speed nearly equal to the sound velocity bombarded the Si wafer surface, as a result, the residue from the slurry solution was reduced from ∼5/cm2 to ∼0.05/cm2 and the metal impurities are completely eliminated below the defect limitation for ICP mass spectroscopy. The charge build-up damage due to the high speed particles is not introduced into the the MOS capacitors. This technology is quite effective, compared with the conventional brush scrubber method and is applicable for the cleaning process below the quarter micron devices.
Determination of Organic Contamination From Polymeric Construction Materials for Semiconductor Technology
Authors: Budde Klaus J.
Published: April 2011

Volatile organic surface contaminants on silicon wafers lead to strong detrimental impact on semiconductor production yield and product reliability. Our model for the mechanism of impact is introduced and discussed.

Only a few metrology methods are suited for the ultratrace detection of volatiles on surfaces and their identification. The data presented in this paper were achieved by ion mobility spectrometry followed by mass spectrometry (IMS/MS).

Eleven commercial wafer storage and transport boxes were screened by sampling the contaminants onto silicon wafers at room temperature. In a second set of experiments, enhanced stress testing was performed at elevated temperatures for polypropylene, polycarbonate, polytetrafluoro ethylene, perfluoro alkoxy polymer, polyvinylidene fluoride and acrylonitrile-butadiene-styrene copolymer. From the outgassing behaviour of single contaminants, valuable information can be achieved.

Test method E 46 (SEMI) samples the contaminants onto the wafer under the real conditions of use. The data for six virgin minienvironments are shown.
Submicron, Noble Metal Particle Reference Standards: A Proposal
Authors: Hockett R. S. , Craig Angela Y. , Le Diem
Published: April 2011

There is a need in the semiconductor industry to develop new techniques and instrumentation for the elemental and chemical analysis of submicron, particularly <0.2 μm, particles. The development of these techniques and instrumentation could be assisted by submicron particle reference standards. We propose that high number-density, noble metal (Cu, Ag, Au) particles on silicon, with controlled diameters in the range of 0.02 μm to 0.10 μm, be developed and used as particle reference standards.
Removal of Fluorine From a Si (100) Surface by a Remote RF Hydrogen Plasma
Authors: Barnak J. P. , King S. , Montgomery J. , Ku Ja-Hum , Nemanich R. J.
Published: April 2011

Fluorine contamination was removed from a Si(100) surface by an atomic H flux. The surface was intentionally contaminated to approximate the residual fluorine concentration remaining after a concentrated HF last process. By dipping the wafers in concentrated HF the thin oxide was removed and replaced with a hydrogen and fluorine terminated surface. This surface was then either vacuum annealed or exposed to a 20 Watt rf excited H-plasma at 50 mTorr, in order to achieve an atomically clean surface. The substrate temperature during the Hplasma exposure and vacuum anneal was 450°C. The surface chemistry was characterized with x-ray photoemission spectroscopy (XPS), auger electron spectroscopy (AES), and angle-resolved UV photoemission spectroscopy (ARUPS). The surface symmetry was characterized with low energy electron diffraction (LEED). Before the H-plasma exposure, the XPS spectra indicated Si-F bonding, and a l×1 LEED diffraction pattern was observed. Immediately following the Hplasma exposure, the fluorine concentration was reduced below detection limits of XPS, and the surface showed a 2×1 reconstruction. A mechanism is proposed by which molecular HF results from atomic hydrogen interactions with fluorine on the surface.
Low Temperature Film Growth by Supersonic Jets of CBr4
Authors: Ohlberg Douglas A. A. , Rose Garry , Ren James , Stanley Williams R.
Published: April 2011

Pulsed, supersonic jets of CBr4 seeded in a hydrogen bath gas have been used to deposit films on silicon at low temperatures (c A. 100° C) in a high vacuum chamber. IN situ analysis of the films using x-ray photoelectron spectroscopy (XPS) and depth profiling indicate a surface composition of 34% Br and 66 % C and a bulk composition of 88% C and 12% Br. the deposition efficiency of CBr4 was found to drop dramatically when seeded in bath gases of deuterium, helium, and argon, suggesting that the film growth is an activated process, requiring precursor energies of at least 3.6 eV.
Luminescent Nanometer-Sized Si Crystals Formed in an amorphous Silicon Dioxide Matrk by Ion Implantation and Annealing
Authors: Iwayama T.S. , Terao Y. , Kamiya A. , Takeda M. , Nakao S. , Saitoh K.
Published: April 2011

Si ion implantation followed by thermal annealing has been used to synthesize luminescent nanometer-sized Si crystals in an amorphous Si02 matrix. Transmission electron microscopy indicates the formation of Si nanocrystals by annealing at 1100 °C, and the growth in average size of Si nanocrystals with increasing annealing time. the shape of the emission spectrum of the photoluminescence is found to be independent of both excitation energy and annealing time, while the excitation spectrum of photoluminescence increases as the photon energy increases and its shape depends on annealing time. the results indicate that the photons are absorbed by Si nanocrystals, for which the band-gap energy is modified by the quantum confinement effects, and the emission of photons is not due to direct electron-hole recombination inside Si nanocrystals but is related to defects probably at the interface between Si nanocrystals and Si02.
Planar Laser-Induced Fluorescence Diagnostics of Pulsed Laser Ablation of Silicon
Authors: Goodwin D. G. , Capewell D. L. , Paul P. H.
Published: April 2011

Planar laser-induced fluorescence has been used to acquire time sequence images of ground-state, neutral Si and SiO during laser ablation of an Si target in vacuum and in the presence of a background gas at a fluence of 3-4 J/cm2. the SiO images, taken in air, strongly suggest that the observed SiO is created through reaction of silicon with oxygen at the contact front as the plume expands.
Effects of Laser Irradiation on Growth and Doping Characteristics of GaAs in Chemical Beam Epitaxy
Authors: Dong H. K. , Li N. Y. , Tu C. W.
Published: April 2011

In this paper, we report laser-assisted chemical beam epitaxy (CBE) of GaAs using triethylgallium (TEGa), tris-dimethylaminoarsenic (TDMAAs), and an ar ion laser operating at visible or ultraviolet (UV) wavelength. the laser-assisted growth with TDMAAs, compared to as4 or asH3, shows a wider range of growth enhancement at low substrate temperatures. Unlike CBE of GaAs without laser irradiation, laser-enhanced GaAs growth rate was found to be constant as the V/III incorporation ratio changes. by using diiodomethane (CI2H2) as a dopant gas, the GaAs films with laser irradiation show a much higher hole concentration than those grown simultaneously without laser irradiation at substrate temperatures from 460-530°C. Laser irradiation was also found to enhance silicon incorporation at low temperatures. Photothermal effects are responsible for laser-enhanced growth and silicon doping, but the wider temperature window in laser-enhanced growth and the laser-enhanced carbon incorporation are caused by additional photocatalytic or photochemical effects.
Spreading Kinetics of Molten 60Sn40Pb on Higher Melting Temperature Pb-Sn Alloy Substrates
Authors: Conrad H. , Guo Z. , Jung D. Y.
Published: April 2011

The spreading of molten 60Sn40Pb drops on higher melting point Pb-Sn alloy substrates (3 to 10 wt.% Sn) was investigated for reflow temperatures of 205° to 300°C. Following melting the drop assumed the form of a slightly flared, spherical cap with some penetration into the substrate beneath the contact area. The effects of time and temperature on the contact angle θ and the depth of penetration h were of the form

where the apparent activation energy Q was 4.2 kcal/mole for θ and 16 kcal/mole for h. The time exponent m (negative for θ and positive for h) decreased with temperature from ∼ 0.2–0.3 at 205°C to ∼0.05 at 260° and then increased again at higher temperatures. The magnitude of Q for θ is in accord with that for the viscosity of molten Pb-Sn alloys and that for h with a combined liquid-solid diffusion involved in the dissolution. Further work is however needed to identify unequivocally the mechanisms which govern the wetting in these duplex Pb-Sn alloy systems.
Stress Concentrations in Electronic Packaging
Authors: Mahajan Ravi , Madenci Erdogan , Ileri Levent , Thurston Mark
Published: April 2011

The reliability of ceramic and plastic packages used in microelectronics is compromised by interface (delamination) and homogeneous (bulk) cracking that is initiated during processing and stress testing. These cracking failures have certain characteristics in that they begin at locations of geometric stress concentrations and propagate along typical failure paths. Characterization of these stress concentrations is therefore essential to a good design and for defining material response parameters such as bulk and interfacial fracture toughness. In this paper, applications of a general-purpose finite element technique for the characterization of stress concentrations are presented. The technique uses the full twodimensional elasticity solution for different materials that are bonded together. It is possible to use this technique to extract relevant material parameters, such as stress intensity factors, the J-integral, or energy release rate, and hence to eventually define the conditions necessary for crack initiation and propagation.
Waveguides Fabricated in Fused Silica by Germanium Ion Implantation at Varying Doses
Authors: Leech Patrick W. , Ridgway Mark C.
Published: April 2011

The implantation of MeV Ge3+ ions into fused silica has been used to fabricate single mode channel waveguides with a low propagation loss of 0.10–0.15 dB/cm. The loss coefficient, α, has been measured as a function of ion dose (8 × 1013 to 8 × 1016 ions/cm2) and annealing temperature (250 to 600 °C) at λ = 1300 nm. The value of cc for the as-implanted waveguides exhibited a minimum of -1.0 dB/cm at an intermediate range of dose from 8 × 1014 to 8 × 1015 ions/cm2. A progressive reduction in α occurred as the annealing temperature was increased from 300 to 500 °C. Annealing of the implanted waveguides at 500 °C for 1 h has produced an order of magnitude decrease in α to 0.1 dB/cm at 8 × 1014 ions/cm2. At doses which were outside of the intermediate range, the value of α was ≥ 10 dB/cm. This trend in α with ion dose has been attributed to the dominance of a residual nuclear component of damage after annealing.
Ion Synthesis of Colloidal Silver Nanoclusters in the Organic Substrate
Authors: Stepanov A. L. , Abdullin S. N. , Khaibullin R. I. , Valeev V. F. , Osin Yu. N. , Bazarov V. V. , Khaibullin I. B.
Published: April 2011

High-dose ion implantation was used to create silver metallic grains in the epoxy resins The structure and optical properties of Ag/organic systems were investigated by transmission electron microscopy and absorption UV-visible spectroscopy, It was established that silver implantation into the organic substrate produced colloidal nanoclusters in the near-surface region, whose average size and size distribution were function of dose value. The silver nanoclusters give rise to optical absorption at the plasmon wavelength. and maximum absorption was shown to be correlated with filling factors. The d.c. resistivities of irradiated samples were measured in temperature range from 5 to 300 K The observed exp(T0/T)n behaviour of resistivity indicated that synthesized metal particles are separated.
Fundamental Performance Limits of Active Polymer Integrated Optics
Authors: Lytel Rick
Published: April 2011

This paper presents a summary of the benefits and limits of active polymer waveguide devices and an overview of the use of active EO polymers in modulation devices with reduced length.
Enzymatically Degradable Synthetic Polymers
Authors: Shao Wen , Leong Kam W.
Published: April 2011

Complex coacervation is an appealing method of microencapsulating delicate proteins for controlled drug delivery. Natural polyelectrolytes, such as collagen, gelatin, hyaluronic acid, and chondroitin sulfate, are popular choices for formulating the microspheres. For advantage of versatility, synthetic systems are attractive. Typical synthetic polyelectrolytes are composed of a carbon-carbon backbone that is nonbiodegradable. To design synthetic polyelectrolytes that are biodegradable, we synthesized diamines containing dipeptide or tripeptide sequences that are enzymatically degradable. The enzymatically degradable linkages comprised gly-phe, gly-phe-phe, or gly-gly-phe, and lysine and 2,3-diaminopropionic acid co-monomers served as the charged component. Using an interfacial polymerization technique, these monomers were condensed with diacyl chlorides, including succinyl, adipoyl, or terephthaloyl chloride to form polyamides. Results of gel permeation chromatography and ninhydrin assays showed that the polymers degraded in PBS containing α-chymotrypsin.