bluuebunny/crossref_metadata_2025_split huggingface dataset:
Deep Levels Associated with Oxygen Precipitation in CZ Silicon and Correlation with Minority Carrier Lifetimes
Authors: Chan S. S. , Varker C. J. , Whitfield J. D. , Carpenter R. W. 
Published: March 2011

AbstractA dominant electron trap in boron-doped CZ silicon at Ec −0.41 ± 0.02 eV with a electron capture cross section >10−14 cm2 has been observed with DLTS in 2-step annealed (16 hrs at 800°C + 16 hrs at 1050°C) seed end wafers where oxygen precipitation is pronounced. A strong correlation between the generation lifetime τg (as calculated from junction reverse generation currents) and the density of this trap is also observed. Electron microscopy showed the dominant precipitates to be {100} plate type containing only Si and 0, with dislocations and punched-out loops in close proximity. Wafers from the center- or tang-sections of the ingot or those given a 1-step anneal (conditions which result in much less oxygen precipitation) contain a low density (<1.2 × 1012 cm−3) of a hole trap at Ev +0.25 eV not correlated with Tg. These wafers contain precipitates with a different morphology with much rower or minimal dislocation densities. Possible origins of the lifetime controlling electron trap is discussed.
Evidence of Lattice Relaxation in Platinum-Doped Silicon
Authors: Mayo Santos , Lowney J. R. , Bell M. I. 
Published: March 2011

AbstractThe photoionization cross section of the platinum-acceptor level in silicon was measured (in relative units) as a function of photon energy. Capacitance transients due to electron emission from this level were studied in a p+n gated photodiode at temperatures of 40, 60, and 80 K. Measurements were made over the wavelength range of 2 to 5 μm with light from a prism monochromator with a constant bandpass of 10 meV. The platinum density in the diode was about 1014 cm−3, providing a ratio of deep to shallow (phosphorus) levels of about 0.1. The data are in good agreement with the Ridley-Amato lattice-coupling model when a Huang-Rhys parameter of S = 0.3 is used, corresponding to a Frank-Condon shift of 15 meV if an average phonon energy of 50 meV is assumed. The electronic energy of the acceptor level was 226 ± 5 meV below the conduction band, independent of temperature and in agreement with previous studies of thermal ionization. The present results provide the first clear experimental evidence of lattice relaxation associated with a deep level in silicon. However, the observed Huang-Rhys parameter is smaller than the theoretical estimates of Lowther (S ≅ 1), suggesting that multiphonon emission may not be the only mechanism for carrier recombination involving this level.
Identification of M Centers in InP
Authors: Wager J. F. , Vechten J. A. Van 
Published: March 2011

AbstractSimple atomic models are proposed for three metastable centers in InP, which have been called “M centers”. All undergo “large lattice relaxation” and emit or absorb multiple electrons on changing atomic configuration. The one which has been most thoroughly studied is called M and is introduced by MeV electron irradiation. The second, called M:P, is present in as grown device quality InP and is a problem for MISFET devices. The third, called M:Fe, is present in Fe doped InP that has been processed at high T to produce a p+ region. Our model for M consists of a V−InP+In defect complex in one configuration and 2P+In + V+p in the other configuration. Transformation between these two configurations occurs by nearest neighbor hopping of a P atom between vacant sites. The “negative U” character of the M center is a simple consequence of the P atom hop. Our model for the M:P center is a V+p one configuration and a V−InIn−p in the other, the transformation occurs by In atom hopping. For the M:Fe center we tentatively propose Fe−In + V−In in one configuration and Fe−In V+PP+In for the other, the transformation again occurring by P atom hopping. It is also possible that the Fe occupies a bond centered interstitial position, Fe−2bc, in the first configuration and Fe−InV+P in the second, the transformation occurring by Fe atom motion. A distinction between these two possibilities can be made with a pressure dependence measurement. It is noted that the activation energies for these transformations support the Ballistic Model for vacancy migration.
Identification of the Double Acceptor States of Some Transition Metal Impurities in GaAs
Authors: Hennel A.M. 
Published: March 2011

AbstractThe double acceptor states of chromium, cobalt and nickel were identified by means of the optical and transport measurements under external fields such as hydrostatic pressure, uniaxial stress and magnetic field. The axial fields enable us to observe optical line splittings, which give information about defect symmetries. This technique has been used to identify a double acceptor state of nickel in the GaAs energy gap. High pressure eliminates a degeneracy between defect levels and crystal bands. This leads to activation of new charge states of some impurities. In the case of chromium and cobalt impurities, their double acceptor levels were found to be degenerate with the conduction band of GaAs. A trend existing for the energies of the double acceptor levels permits us to conclude that there will be no other acceptors among the transition metal impurities in GaAs.
High Resolution Transmission Electron Microscopy of Proton Implanted Gallium Arsenide
Authors: Sadana D. K. , Zavada J. M. , Jenkinson H. A. , Sands T. 
Published: March 2011

AbstractHigh resolution transmission electron microscopy (HRTEM) has been performed on cross-sectional specimens from high dose (1016 cm−2) H+ implanted (100) GaAs (300 keV at room temperature). It was found that annealing at 500°C created small (20-50Å) loops on {111} near the projected range (Rp)(3.2 μm). At 550-600°C, voids surrounded by stacking faults, microtwins and perfect dislocations were observed near the Rp. A phenomenological model explaining the observed results is proposed.
A Study of Co and Mn in ZnO Varistors
Authors: Pike G. E. , Seager C. H. , Dosch R. G. 
Published: March 2011

AbstractZnO varistors are polycrystalline materials which have highly non—linear current/voltage characteristics controlled by depletion regions around the grain boundaries. Dissolved transition metals at concentrations of about 1 at.% are required to achieve this large nonlinearity, but their role is unclear. To address this issue we have usedthe technique of photothermal deflection spectroscopy to measure the optical absorption of varistors containing Co or Mn, both common dopants. Prominent peaks and edges appear in the spectra, and are associated with substitutional Co2+and Mn2+ ions whose ground states are deep within the ZnO bandgap. Electro— and photoluminescence spectra show Stokes shifted peaks for some of these transitions. The spectral dependence of the photoconductivity shows that some of the absorption features correspond to ionization of the impurities. This result is used to show how the dark impact ionization of these impurities due to a high applied voltage can contribute to the current/voltage nonlinearity.
Dry—Processing Induced Isolation—Degradation in GaAs Integrated Circuits
Authors: Chang M.F. , Lee C.P. , Sheng N.H. , Kirkpatrick C.G. , Chen R.T. 
Published: March 2011

AbstractOur study shows that the isolation—degradation in semi—insulating GaAs substrate is closely related to dry—processes during the device fabrication. It was found that EL2, the major electron trap in undoped LEC semiinsulating GaAs, could be passivated by plasma—assisted etchings or depositions. The passivation of EL2 causessurface leakage and leads to crosstalk in GaAs ICs.
EBIC Spectroscopy - A New Approach to Microscale Characterization of Deep Levels in Semi-Insulating GaAs
Authors: Li C.-J. , Sun Q. , Lagowski J. , Gatos H.C. 
Published: March 2011

AbstractWe propose a new approach to the defect characterization in semiinsulating (SI) GaAs which combines the high spatial resolution and scanning capability of the Electron Beam-Induced Current (EBIC) mode of Scanning Electron Microscopy (SEM) with the advantages of optical and thermal spectroscopies employed in the identification of deep levels. In the PHOTO-EBIC approach a DC electron beam and a chopped subbandgap monochromatic light impinge on the SI GaAs through a semi-transparent Au electrode. The photoinduced modulation of the EBIC as a function of the subbandgap energy of incident photons constitutes a structure which corresponds to the photoionization of deep levels. In the thermally stimulated EBIC (TS-EBIC) the deep levels are filled at low temperature by the excess carriers generated by an electron beam. Subsequently, the changes of EBIC as a function of temperature constitute a spectrum of peaks which correspond to different deep levels. The peak position determines the deep level energy while the magnitude of peaks can be used for the assessment of the relative concentration of deep levels located within the small volume probed by the electron beam.
Local Vibrational Mode Spectroscopy of Impurities in Semiconductors
Authors: Newman R. C. 
Published: March 2011

AbstractInfrared band—mode and LVM absorption is illustrated for a range of impurities and impurity—complexes in silicon and gallium arsenide. We discuss the effects of changes in the local force constants and contributions to the dipole moment resulting from displacements of host lattice atoms. The difficulties in establishing absolute calibrations relating the strength of the absorption to the concentration of defects are highlighted. Our purpose is to show how the measurements lead to characterization of crystals and how they complement other diagnostic techniques to evaluate effects of irradiation, heat treatments, diffusions etc.
Optical Properties of the Pb Center at the Si/SiO2 Interface
Authors: Edwards Arthur H. , Fowler W. Beall 
Published: March 2011

AbstractWe present theoretical results for the optical prooerties of the Pb center at the Si/SiO2 interface. Using wave functions obtainec from semiempirical (MINDO/3) cluster calculations, we have calculated electric dipole matrix elements connecting the singly occupied (neutral) defect state to the unoccupied conduction-band-like states, as well as those connecting the occupied valence-band-like states to the singly occupied defect state and to the unoccupied defect state. We predict the absorption cross section for excitation from the valence band to the unoccupied state to be of order 10−19 cm2 and that for excitation from the valence band to the occupied state and from the occupied state to the conduction band to be an order of magnitude larger. We also predict that the absorption will in some cases be strongly dependent on the direction of the polarization. Effects of symmetry lowering in the oxide and of distortions in the silicon are discussed.
Comparison of the Optical Cross Section for the Si Dangling Bond in a- Si:H and At the c - Si/SiO2 Interface
Authors: Jackson W. B. , Johnson N. M. 
Published: March 2011

AbstractThe optical properties of the trivalent silicon dangling bond defect in hydrogenated amorphous silicon and at the Si/SiO2 interface are compared. While both defects give rise to ambipolar deep levels within the gap, significant differences in the optical properties between the two systems are found. The absorption in a-Si:H is significantly stronger and is dominated by a transition from the defect to the conduction band while the absorption at the interface is dominated by hole emission. The average dipole matrix element squared is roughly independent of energy in both systems with a magnitude of ∼30Å2. Implications of these results for optical measurements in other silicon systems are discussed.
A Dynamic Jahn-Teller Effect in the ESR Spectrum of the N1 Centre in Diamond
Authors: Loubser J.H.N. , Wyk J.A. Van 
Published: March 2011

AbstractThe N1 centre in Type Ia diamonds is a di-nitrogen centre with S = ½. One nitrogen's interaction with the unpaired electron at room temperature gives a large splitting, All = 46.4 G, A ⊥ = 32.2 G with <111> symmetry while the hyperfine splitting due to the other one has <110> symmetry with parameters All = 2.95 ±.03 G, A⊥ = 2.81 ±.03 G. As the temperature is increased averaging effects start; first some hyperfine lines broaden at about 150°C and disappear at 200°C. At still higher temperatures new lines appear and at about 850°C the averaging process is completed. The interpretation of the dynamics leads to a model of a non-planar N-C-C-N configuration with the electron jumping between the two N-C bonds. The measured activation energy is 0.4 eV which is about midway between the measured values for a similar effect in the isolated nitrogen centre, P1, (E = 0.7eV) and the N-C-N, W7, centre (E = 0.24 eV).
Cross-Sectional Transmission Electron Microscopy of Defects in Beta Silicon Carbide Thin Films
Authors: Carter C.H. , Edmond J.A. , Palmour J.W. , Ryu J. , Kim H.J. , Davis R.F. 
Published: March 2011

AbstractTechniques have been developed at NCSU for fabricating cross-sectional transmission electron microscopy (XTEM) foils from monocrystalline beta silicon carbide thin films grown by chemical vapor deposition. The results of the TEM observations are utilized to discern the efficacy of the various processing parameters in terms of film quality and defect structure as well as oxidation, ion implantation and annealing procedures.
Thermodynamics of Deep Levels in Semiconductor
Authors: Vechten J.A. van 
Published: March 2011

AbstractThermodynamnies is obviously central to the ultimate goal ol an exquisite control of the electronic properties of scmiconducting devices and to the uinderstanding this will require. It should also be useful for the subsidiary goal of the firm identification of the various electrically active defects. This subsidiary goal will not be achieved unless adequate attention is paid to the reactions among the various atomic and ionization states of the defects, the electrons and the holes.
Special Aspects of Diffusion in Metallic Thin Films
Authors: Gupta D. 
Published: March 2011

ABSTRACTThe diffusion processes in thin films are largely controlled by their microstructure and chemistry. In this publication, we discuss briefly how the recently devel-oped experimental techniques coupled with the available analytical treatments have been able to characterize these processes. Actually a hierarchy of diffusion rates along the atomic defects in thin films, namely the vacancies, grain-boundaries and dislocations, has been found. The interactions of solutes present in thin films with the atomic defects in altering the diffusion rates are discussed. It has also been possible to measure diffusion in amorphous metallic alloy films and its features are described. Finally, we outline the general principles for modifying diffusion in thin films to achieve the desired technological objectives.
The Structure of Si and Ge Deposited by Ion Beam Sputtering
Authors: Windischmann H. , Cavese J. M. , Collins R. W. , Harris R. D. , Gonzalez-Hernandez J. 
Published: March 2011

ABSTRACTThe crystallinity for silicon and germanium films deposited by ion beam sputtering (IBS) as a function of substrate temperatures was determined using Raman spectroscopy, spectroscopic ellipsometry, electrical conductivity and x-ray diffraction measurements. The results show that IBS silicon crystallizes between 300–350°C while germanium crystallizes between 20–200°C. Reasonably good agreement is obtained among the four distinctively different characterization techniques in identifying the onset of crystallinity. A direct relationship is observed between the substrate temperature required for crystallization and the log of the operating pressure for various deposition techniques. Energetic particle stimulation during film growth appears to reduce the crystallization temperature at a given operating pressure. Raman data show that the crystallization temperature depends on the deposition rate. A graded structure is observed in films deposited above 300°C, probably due to oxygen contamination.
Thin Films of Diamond-Like Carbon
Authors: Kerwin David B. , Daudin Bruno , Dubus Michel , Fontenille J. , Robinson Raymond S. , Spain Ian L. 
Published: March 2011

ABSTRACTThin films of hard, diamond-like, carbon have been deposited on glass, silicon and sapphire substrates using three different ion beam deposition techniques: (a) ion beam sputter-deposition from a graphite target, (b) sputter-deposition with simultaneous bombardment of the growing film using a second ion beam, (c) primary ion deposition using a beam extracted from an Ar-hydrocarbon plasma. Structural, mechanical optical and electrical properties were measured. It was found that the hydrogen content controlled the internal (compressive) stress and that relatively stress-free films contained ,∼ 30 atomic % H (average). The H content could be correlated with the H/C arrival ratio from the gas phase. Optical absorption and luminescence measurements gave a band gap of '∼, 1 ev with band-tailing. Resistivity measurements and their temperature dependence fitted variable range hopping models. Hardnesses were ≿ 7 Mohs. The properties of the films were consistent with a mixture of sp3 and sp2 bonds in an amorphous, hydrogenated structure.
Electronic Properties of Thin PD Overlayers on Au(111): Relationship to Chemisorption Properties
Authors: Shena Xinyin , Frankel D. J. , Hermanson J. , Lapeyre G. J. , Smith R. J. 
Published: March 2011

ABSTRACTWe present results for the electronic structure and chemical properties of thin Pd films grown epitaxially on Au(lll) single-crystal substrates. Photoemission spectroscopy is used to monitor the development of the Pd d-bands near the Fermi energy (EF ) as a function of overlayer thickness. The state density aF E is relatively small for the single Pd monolayer (ML), but increases monotonically with overlayer thickness, resembling the bulk Pd electronic structure for films thicker than 5 ML. At the same time we observe that the 1 ML Pd film is iner with respect to CO chemisorption, while the multilayer films readily chemisorb CO, similar to bulk Pd. We examine possible models for the inert behavior of the Pd monolayer, based on related slab calculations which show the substrate-induced modification of the electronic structure in the overlayer.
Capillary Instabilities in Thin, Polycrystalline Films
Authors: Srolovitz David J. , Safran S. A. 
Published: March 2011

ABSTRACTThin films can break up into islands only if they are perturbed by substrate-intersecting perturbations. Grain boundary grooves and vertex pits are typical defects which nucleate holes in these films. Holes which exceed a critical size - proportional to the ratio of the film thickness to the equilibrium contact angle - grow, eventually disconnecting the film.
The Structural Properties of Sputtered Zinc Oxide
Authors: Hickernell Fred S. 
Published: March 2011

ABSTRACTX-ray diffraction, chemical etching and electron microscopy are useful in delineating the microstructural properties of c-axis normal oriented polycrystalline zinc oxide films, sputter deposited on amorphous substrates. Dense ZnO films with high crystalline content and low etch rates have a strong piezoelectric effect and low surface acoustic wave and guided optical wave propagation loss. The structural properties are dependent upon substrate conditions, deposition parameters and the type of sputtering system used. Scanning electron microscope examination of the surface and side fractures of high quality ZnO films show smooth continuous upper surface and side regions with no vertical fiber grain structures apparent. Light chemical etching reveals surface defects consisting of uniformly distributed conical shaped etch pit structures with a lateral to vertical etch ratio of 3 to 1. A correlation has been made between film structure and single crystal zinc oxide. The structural picture which emerges is that of a predominantly positive polarity (0001) upper surface layer with localized negative polarity (0001) fiber grain inversions. The sputter conditions which lead to low defect density films are a high substrate temperature, high deposition rate and low reactive gas pressures to promote the adatom mobility necessary for the preferred (0001) zinc face growth. Post deposition laser and thermal annealing can be used to reduce stress in the films and improve their guided optical wave properties.
Electrcn Trapping/Detrapping in Thin SiO2 Under High Fields
Authors: Wu N. R. , Chiao S. , Wang C. , Bhushan B. , Yang C. Y. 
Published: March 2011

ABSTRACTA constant alternating current stressing technique is employed to study the electron trapping and detrapping cha~acteristics
within a layer of thin silicon dioxide (˜.100 Å). A two-charge centroid model is proposed to explain the trapping/detrapping phenomena under high electric fields. The oxide breakdown mechanism induced by the local field of trapped electrons is also discussed.
Electronic and Optical Properties of A—(Si, Ge):H Alloys
Authors: Daial Vikram , Booker James F. , Leonard Mark 
Published: March 2011

AbstractWe describe the preparation and electronic and optical properties of amorphous (Si, Ge) alloys. A—(Si, Ge):H alloys were prepared by glow discharge decomposition of SiH4 and GeH4. The bandgap was varied between 1.78 and 1.42 eV by changing the GeH4:SiH4 ratio in the gas phase. We find a distinct influence of growth temperature on electronic properties. Films grown at low temperatures (200–250C) tendto have much lower photo conductivity than films grown at higher temperatures (300–325C). The electron (μ τ) products of high temperature films are general> 1X10–7 cm2/V. We also obtain very sharp valence band tails in a—(Si, Ge):H alloys, with slopes of ∼ 40 meV. The hole (μ τ) product is generally ∼1–2X10–8 cm2/V. All these properties suffer a catastrophic decline when bandgap is reduced below about 1.5 eV.
Preparation of α-(Si.Ge):H Alloys by D.C. Glow Discharge Deposition
Authors: Slobodin D. , Aljishi S. , Schwarz R. , Wagner S. 
Published: March 2011

AbstractWe report the preparation of α-(Si.Ge):H alloy films by decomposition of SiF4, GeF4, and H2 in a d.c. glow discharge. Germanium is incorporated very efficiently from GeF4. The germanium content and optical gap canbe controlled by varying the GeF4 flow while keeping the SiF4 and H2 flows constant. The films, all prepared at 300 ºC substrate temperature, exhibit high photo- to dark-conductivity ratios for compositions of up to -25% germanium.
Amorphous Silicon—Germanium Deposited by Photo—CVD
Authors: Itozaki H. , Fujita N. , Hitotsuyanagi H. 
Published: March 2011

AbstractHydrogenated amorphous silicon germanium (a—SiGe:H) films were deposited by photo—chemical vapor deposition (Photo—CVD) of SiH4 and GeH4 with mercury sensitizer. Their band gap was controlled from 0.9 eV to 1.9 eV by changing the gas ratio of SiH4 and GeH4. High quality opto—electrical properties have been obtained for thea—SiGe:H films by Photo—CVD. Hydrogen termination and microstructure of a-SiGe:H were investigated by infrared absorption and transmission electron microscopy. Ana—Si:H solar cell and an a—Si:H/a—SiGe:H stacked solar cell were made, each of which has conversion efficiency 5.3% and 5.1%, respectively.
Properties of A—Sin:H Films Prepared by Glow Discharge of Si2H6—Nh3 Gas Mixture
Authors: Kojima Y. , Narikawa S. , Matsuyama T. , Imada E. , Nojima H. , Hayakawa T. , Ehara S. 
Published: March 2011

AbstractThe electrical and optical properties of a—SiNx:H films prepared by the glow discharge of Si2H6-NH3 gas mixture have been investigated in a wide range of the molar ratio of NH3 to Si2H6 The maxima of the dark—and the photo—conductivity are observed at the molar ratio of about 10-1. At this molar ratio the deposition rate is about33 Å/sec. The optical gap and the compositional ratio of nitrogen to silicon change smoothly from those of a—Si:H to those of a—Si3N4. It is found that the valency control is possible in a—SiNx:H films prepared at a high deposition rate.