bluuebunny/crossref_metadata_2025_split huggingface dataset:
HCP-FCC Transition in Epitaxial Co-Cu Superlattices
Authors: Lamelas F. J. , Lee C. H. , He Hui , Vavra W. , Clarke Roy 
Published: September 2012

ABSTRACTA series of epitaxial Co-Cu superlattices has been grown on GaAs (110) substrates by molecular beam epitaxy. Detailed analysis of x-ray diffuse scattering scans along Co (101ℓ) reveals a crossover from from the bulk hcp phase of Co to metastable fcc stacking. Our measurements indicate a strong correlation between structural symmetry and the magnetic anisotropy in Co - noble metal superlattices. In particular, the perpendicular easy axis of magnetization onsets at Co layer thickness ♣ 19 Å in Cohcp-Au compared to only ˜11 Å in Cofcc-Cu.
Temperature Dependence of Two-Dimensional Spin Anisotropies
Authors: Richter Roy , Gay Jack G. 
Published: September 2012

ABSTRACTLarge anisotropy energy is an essential property of high quality permanent magnets. In previous work we have calculated the spin polarized electronic structure and anisotropy of monolayers and slabs of Fe, Ni, and V. In this work we calculate the dependence on temperature of the spin anisotropy of a ferromagnetic monolayer of Fe. We find the easy direction of magnetization is not sensitive to the temperature; the variations calculated here are likely too small to be observed. It is perpendicular to the plane of the surface for both low and high temperatures. The calculations become progressively more ill-behaved as the temperatures are lowered and require more computer time for satisfactory convergence.For Fe/Cu {100}, we find the spins always prefer to point out of plane. Experimental results in general are consistent with this view, although the systems seem to be difficult to prepare.
The D-Band Exchange Splitting for Thin Gadolinium Overlayers
Authors: Lagraffe O. , Dowben P. A. , Onellion M. 
Published: September 2012

ABSTRACTThin (0–6 monolayer) films of gadolinium on Cu(100) have been investigated using synchrotron radiation photoemission. From the definite selection of final state symmetries in photoemission, we have been able to determine a lower bound to the exchange splitting of the gadolinium 5d band. The gadolinium films on Cu(100) exhibit an exchange splitting that changes from approximately 1.1 eV to 0.6 eV as the overlayer thickness increases. The results for thicker films agree with the accepted values for the 5d exchange splitting of bulk gadolinium.
Growth, Characterization and Magnetic Properties Of HCP Fe/Ru Superlattices Synthetized by MBE
Authors: Maurer M. , Ousset J. C. , Piecuch M. , Ravet M. F , Sanchez J. P. 
Published: September 2012

ABSTRACTHexagonal-close-packed Fex/Rux superlattices with the modulation along the (0001) axis, contaln fully hcp Fe layers. The interatomic Fe-Fe distances are enlarged by about 10% as compared to fcc Fe. Ferromagnetic behavior is found when Fe layers are thicker than about 4 monolayers.
Study of Medium-Deep Traps in Undoped GaAs Grown by Arsenic-Pressure Controlled Cz Method
Authors: Shiraki Hiroyuki , Tokuda Yutaka , Sassa Koichi 
Published: September 2012

ABSTRACTProperties of medium-deep traps in n-type undoped GaAs crystals grown by arsenic-pressure controlled Czochralski (PCZ) method were studied by using capacitance transient spectroscopy (CTS) and temperature-dependent Hall (TDH) measurement. EL3 and EL6-like (EM2) traps were dominant medium-deep traps in D LTS measurements. The dependence of EM2 peak height on the duration of filling pulse and the detailed analysis of CTS showed that the trap EM2 spectrum consisted of three electron traps which had thermal emission activation energies of approximately 0.35 eV and various capture cross sections with activation energies for electron capture. On the other hand, the trap EL6 spectrum in n-type LEC GaAs was described by two levels of traps with activation energies of 0.32 eV and 0.33 eV for electron emission, respectively. It was concluded that so-called EL6 formed a family and some of its components were classified as defects with large lattice relaxation.
Point Defect Assisted Crystal Growth of Bulk ZnSe
Authors: Terashima K. , Toklzaki E. , Kondo H. , Tanigawa S. , Uedono A. , Watauchi S. , Ujihira Y. 
Published: September 2012

ABSTRACTBulk ZnSe single crystals were grown by annealing a CVD grown polycrystalline ingot in a selenium atmosphere for two weeks at 1000°C. To identify the defect structures closely related to the observed grain growth, point defects in bulk ZnSe were subsequently investigated using the positron annihilation technique. A striking result has been obtained; the selenium interstitial type defects were dominantly observed in the crystals grown under a selenium ambient. The fraction of annihilations from the trap states at selenium interstitial type defects in ZnSe increased with increasing the selenium pressure in the annealing ampoule. These results indicated that selenium interstitial type defects enhanced the atomic migration in the crystal and strongly assisted the recrystallization by dislocation climb.
Microstructural and Microchemical Characterisation of CuInSe2 Ingots Grown by the Vertical Bridgman Technique
Authors: Mullan C. A. , Casey S. M. , Jones C. , Kiely C. J. , Imanieh M. , Tomlinson R. D. 
Published: September 2012

ABSTRACTThe microstructure and microchemistry of a number of melt textured CuInSe2 ingots prepared from a variety of starting charge compositions have been investigated using a combination of TEM, EPMA and Auger spectroscopy. If a stoichiometric starting mixture is used, In-rich and Cu-rich precipitates are found at the first and last to freeze zones of the ingot respectively, accompanied by an intervening mid-portion of inclusion free (although slightly off-stoichiometry) CuInSe2 We have found that in order to achieve an optimum matrix composition, a Cu-rich charge is required; however, this leads to a fine distribution of copper selenide particles throughout the ingot. If the starting charge is In-rich, then the boule contains In-rich precipitates and the matrix composition is In-rich and Cu-deficient. These observations are correlated with the observed electrical characteristics of the boules.
Stability Against Concentration Fluctuations in Compound Semiconductors
Authors: Desre P. J. 
Published: September 2012

ABSTRACTThe variation of the composition within the narrow range of off stoic hiometry allowed for compounds is determinant for the population of various intrinsic point defects. As such concentration fluctuations result in inhomogeneities of defect distributions. On the basis of statistical thermodynamics, applied to concentration fluctuation analysis in the III-V compounds, a thermodynamic stability length is defined and calculated as a function of temperature for GaAs, GaSb and GaP. This thermodynamic stability length defines the scale above which full composition homogeneity is unattainable.
Thermal Stability of SiHn Configurations in Fz Silicon Single Crystals
Authors: Kouketsu Masami , Isomae Seiichi 
Published: September 2012

ABSTRACTThermal stability of SiHn (n=1∼4) configurations in FZ silicon crystals grown in Ar/H2 has been investigated by means of infrared absorption spectroscopy. Infrared absorption peaks at 2210, 2192, 2123 and 1946 cm−1, which are due to SiH4, SiH3, SiH2 and SiH units in silicon lattice, has been observed. It is found that the concentration of SiH4 and SiH increase with the decrease in SiH2 and SiH3 concentration at 500°C, and vice versa at 600°C. Annealing results suggest thermally induced structural transformations of SiHn configurations. We propose a model of the transformations through the cleavage of adjacent Si-H bonds to form a Si-Si bond and a H2 molecule, as well as the reaction of a H2 molecule with a Si-Si bond.
Impurity and Stoichiometry Control in Atomic Layer Epitaxy
Authors: Yokoyama H. , Ikuta K. , Inoue N. 
Published: September 2012

ABSTRACTWe investigate the intrinsic point defects in epilayers grown by atomic layer epitaxy (ALE). Ga vacancies and antisite As atoms in the epilayers are detected by photoluminescence spectroscopy. This shows that the ALE epilayer was grown under As-rich conditions. We propose increasing the TMG flux to reduce the number of point defects. With this method, the number of point defects in ALE epilayers can be decreased to less than that in conventionally grown epilayers. Moreover, it is'found that these point defects are formed by the incomplete Ga coverage, not by the steric hindrance as previously suggested. The carbon concentration is decreased by one order of magnitude by using nitrogen instead of hydrogen as the carrier gas. As an application of this low defect density, we fabricated a GaAs/AlAs resonant tunneling diode and observed the negative resistance at room temperature.
Thin Oxide Defects Resulting from Plasma Induced Wafer Charging
Authors: Fang Sychyi , McVittie James P. 
Published: September 2012

ABSTRACTEEPROM charge monitors reveal that an O2 plasma induces a negative charge which peaks at the wafer center for the asher used. The charge damage to small gate area MOS capacitors is investigated by using “antenna” structure. The post plasma interface state density increases with increasing antenna size and varies by two orders of magnitude. A hole trapping induced breakdown mechanism during plasma charging is supported by new experimental evidence such as the annealing and polarity effects of charge-to-breakdown and tunneling currents. Where stressing has not being severe, these hole traps are annealable at T > 650°C, while in severely stressed areas early breakdown occurs which is not annealable.
Optimization of MBE of CdTe/CdTe: Refinement in Structural Quality Evaluation of MBE Grown (111) CdTe
Authors: Lee M. B. , Fanning T. , Di Marzio D. , Casagrande L. G. , Dudley M. 
Published: September 2012

ABSTRACTA detailed optimization of MBE growth of CdTe on CdTe (111)β using white beam synchrotron x-ray topography, and x-ray rocking curve analysis has been carried out. Defect structures in (111)5 substrates and epilayers are imaged with white beam topography and, for the first time, direct observation of stress induced microtwin growth in CdTe epilayers has been made. X-ray rocking curve analysis of CdTe substrates is shown to be relatively insensitive to defect structures consisting of dislocations and inclusions. On the other hand rocking curve analysis of (111) epilayers reveals a sensitivity to the presence of microtwin. The defect microstructure of a CdTe (111)Bepilayer with the narrowest rocking curve FWHM value published to date (9.4 arc-sec) will be discussed.
Mosaic Spread of the Heteroepitaxial Structures from Renninger Scan
Authors: Morelhão S. L. , Cardoso L. P. 
Published: September 2012

ABSTRACTIn this work, a method of obtaining mosaic spread of the heteroepitaxial structures using Renninger scan (RS) peak profiles is reported. A simulation program was developed in order to account for the influence of the wavelengths, incident beam divergence, sample mosaic spread (layer and substrate) in the profile of the RS peaks. Surface three beam multiple diffraction cases with a forbidden or even very weak primary reflections are used to provide simpler intensity expressions and high intensity in RS. GaAs/Si samples have been analyzed as an application of this method.
Noble Gas Incorporation in Sputtered and Ion Beam Assisted Grown Silicon Films
Authors: van Veen A. , Greuter M. J. W. , Niesen L. , Nielsen B. , Lynn K.G. 
Published: September 2012

ABSTRACTGas desorption measurements have been performed on sputter deposited silicon films. The sputter gas was argon or krypton. Parameters influencing the incorporation process e.g. bias voltage, substrate temperature and arrival rate ratio of silicon and noble gas atoms have been systematically varied. The films, a-Si and c-Si, have been characterised by various techniques for composition and defect analysis. A model has been applied to describe the composition of the growing silicon layer. Underlying mechanisms like gas-gas sputtering have been studied in separate ion implantation experiments. For a-Si concentrations as high as 6% Ar and Kr have been found. An important effect is the injection of self- interstitial atoms caused by the low energy heavy ion bombardment. It causes the layer to grow without large open volume defects.
Atomic Structures of Planar Defects in Si and GaAs
Authors: Takeda S. , Muto S. , Hirata M. 
Published: September 2012

ABSTRACTAtomic structures of planar defects in Si and GaAs have been studied by TEM. An HREM image of the edge of {113} planar defect has been obtained with <110> incidence. An analysis of the image has showed diat the edge consists of 5-, 6- and 7-membered rings without dangling bond. Anisotropie morphology of the defect could be understood from the model proposed in this report. Weak diffuse scattering and an extinction rule in diffraction patterns from the defect have been found. The experimental evidence has supported the model of the {113} defect.A planar defect on {111} in a heavily Si doped GaAs has been studied. The result has indicated that Si precipitates on the two {111} net planes inserted in the GaAs matrix.
Recombination Activity of Individual Extended Defects in Silicon
Authors: Cavallini A. , Castaldini A. 
Published: September 2012

ABSTRACTDislocations and point defects introduce energy levels deep in the gap, which dramatically change the material electrical properties. Because of the coexistence of a multitude of dislocation types and dislocation-point defect interaction mechanisms, it would be highly desirable to identify the particular type of defect related to specific traps.The electrical activity of extended defects (planar precipitates and dislocations) is here examined in terms of their recombination activity, investigated by electron as well as light beam induced current methods of scanning microscopy.Besides, a scanning modification of spectroscopy is used to identify traps at individual defects. The method, named quenched infra-red beam induced current, combines the scanning light beam induced current technique with the spectroscopie bulk analysis called “infrared quenching of photoconductivity”.Defect energy levels are found on the basis of the particular features of the beam induced current as a function of injected carrier generation rate, temperature and quenching excitation.
Evaluation of Vacancy-Type Defects in Simox Substrates by a Slow Positron Beam and a Pulsed Positron Beam
Authors: Kametani H. , Akiyama H. , Yamaguchi Y. , Koumaru M. , Wei L. , Tabuki Y. , Tanigawa S. , Uedono A. , Watauchi S. , Ujihira Y. , Suzuki R. , Ohgaki H. , Mikado T. 
Published: September 2012

ABSTRACTSlow/monoenergetic positron beams and pulsed positron beams have been used as a non-destructive probe to investigate vacancy-type defects in SIMOX substrates which were formed by high - dose oxygen implantation and high-temperature annealing. To obtain depth profiles of vacancy-type defects, a positron beam in the 0–30keV energy range was used. Doppler broadened annihilation spectrum and positron lifetime were measured as a function of incident positron energy. These measurements show the following results; vacancy -type defects exist near the surface of the top silicon layer even if the specimen was analyzed as defect -free Silicon by XTEM, and in the case of the as-implanted specimen, cavities in diameter of about 50–200A are created in the top silicon layer and they include high pressure gases.
Transmission Electron Microscopy of Hydrogen-Induced Defects in Low Temperature Epitaxial Silicon
Authors: Anderson G. B. , Tsai C. C. , Thompson R. 
Published: September 2012

ABSTRACTHydrogen is commonly used in crystalline Si for passivation of defects and impurities. When single crystal Si undergoes a post-hydrogenation step, hydrogen-induced platelets have been shown to form in the first 100 nm of the Si. The same hydrogen platelets occur in homoepitaxial Si grown by low temperature (350°C or below) plasma-enhanced chemical vapor deposition with hydrogen dilution. This study has used transmission electron microscopy (TEM) to examine the structure of these hydrogen-induced platelets. TEM has shown that the platelets generally grow in tne (111) crystal planes of the Si. The size of the platelets, which ranges from 5 to 100 nm, increases with growth temperature but the density of platelets decrease at higher growth temperatures. The hydrogen platelets are not confined to the epitaxial Si layer only but also grow into the substrate. High resolution TEM shows the platelets dilate the silicon lattice by approximately 60% of a Si <111> plane. TEM has also shown that platelets cause no net displacement of the local Si lattice. Tilting experiments performed in the TEM show that the platelets are composed of a circular two-dimensional structure. Our results indicate that the hydrogen-induced platelets found in low temperature epitaxial Si are structurally the same as those seen in crystalline Si that has undergone post-hydrogenation processes.
Influence of Surface Relaxation and Multi-Dislocation Strain Field Interactions on X-ray Topographic Images of Dislocations in Semiconductor Materials
Authors: Wu Jun , Fannin Thomas , Dudley Michael , Shastry Vijay , Anderson Peter 
Published: September 2012

ABSTRACTAnalysis of the white beam synchrotron x-ray topographic contrast behavior of screw dislocations comprising slip bands in silicon, observed under low absorption conditions, is presented. For both individual and groups of dislocations, observed “Direct Image” contrast at the surface intersections of dislocation lines, on reflections for which g·b=0, could be accounted for using equi-misorientation contour analysis using displacement fields which take surface relaxation effects into account. This contrast is shown to be a sensitive function of the local stress environment. In addition, diffuse area contrast observed within and in the vicinity of slip bands on such reflections is also observed to be very sensitive to long range strain fields associated with adjacent slip bands and other defects in the local slip band environment.
Infrared Absorption by Free Carriers in Si and Influence on Oxygen Determination by Ftir-Spectroscopy
Authors: Koster L. , Bittersberger F. 
Published: September 2012

ABSTRACTUsing FTIR-spectroscopy for the determination of the oxygen content in CZ Si, an additional absorption of IR light occurs for doping densities above 1015/cm3, which is caused by the free carriers. It increases nearly linearly with the carrier density and reduces multiple reflections within the sample. Excessively low oxygen values are obtained if this effect is neglected. The deviation from the true values can amount up to 15 % and depends on carrier density, type of doping, oxygen content and sample thickness. Measurements of the absorption coefficient induced by the free carriers were performed for p-and n-type FZ material in dependence of the IR wavelength and of the doping concentration. The obtained values at the wavelength of the oxygen absorption band (1107 cm−1) were used to calculate correction factors for the oxygen content in the doping range from 1 * 1017 to 1 * 1015/cm3. An example shows that the correction reaches 5 % for carrier densities of 1 * 1017/cm3, n-type and 2 * 1016/cm3, p-type, respectively, for an assumed sample thickness of 0.7 mm.
Characterization of Defects in Heavily Si-Doped GaAs by A Monoenergetic Positron Beam
Authors: Uedono A. , Ujihira Y. , Wei L. , Tanigawa S. 
Published: September 2012

ABSTRACTNative defects in Si-doped, Zn-doped and undoped GaAs grown by horizontal Bridgman (HB) method and molecular beam epitaxiy (MBE) were studied by a monoenergetic positron beam. Positron lifetime spectra and Doppler broadening profiles were also measured by using energetic positrons. It was found that monovacancies were usually found in Si-doped HB-GaAs, however, divacancies were created in a specimen with low impurity concentration. For Zn-doped HB-GaAs, interstitial clusters were found to be major type of defects. The high concentration of monovacancies and of divacancies coexist in heavily Si-doped MBE-GaAs. These vacancy-complexes were found to act to reduce the concentration of free carriers.
EL2 Related Anomalous Splitting in the Photoreflectance Response of Semi-Insulating GaAs
Authors: Durbin C. , Estrera J. , Glosser R. , Duncan Walter , Henry R.L. , Nordquist P. , Bottka N. , Gaskill D.K. 
Published: September 2012

ABSTRACTAnomalous splitting has been observed in the photoreflectance (PR) response of SI:GaAs in the vicinity of the exciton at 78 K. Recent photohiminescence (PL) measurements suggest the splitting is correlated with the EL2 content of the samples. Separation between the two peaks in PR measurements range from about 2 to 4 meV. A striking effect is that each peak is maximized by a different phase setting of the lock-in. The splitting is sample dependent and is also affected by several other factors including surface conditions, temperature, pump beam intensity and modulation frequency.
Dynamic Behavior of Intrinsic Point Defects in Fz and Cz Silicon Crystals
Authors: Abe Takao , Takeno Hiroshi 
Published: September 2012

ABSTRACTDetaching the crystals from the melt revealed the real state and dynamic change of intrinsic point defects. From this observation it is confirmed that the predominant point defects near the melting point are vacancies. Clusters of interstitial-type dislocation loops (CDL) are eliminated by taking an extremely low growth rate under 0.2 mm/min and nitrogen doping. The anomalous oxygen precipitate (AOP) of the crystals grown in a nitrogen ambient is enhanced. AOP and ring-oxidation induced stacking fault (R-OSF) coexist at the periphery in nitrogen doped crystals. Almost all crystals have defect boundaries between periphery and center region which may be attributed to a stress field in the crystals during growth.
Characterization of Metal-Oxide-Silicon Interface by Monoenergetic Positron Beam
Authors: Ohji Yuzuru , Uedono Akira , Wei Long , Tabuki Yasushi , Tanigawa Shoichiro 
Published: September 2012

ABSTRACTMOS device interfaces are investigated using carrier injection and monoenergetic positron beam experiments. Carrier injection reveals that the holes injected into gate S1O2 film seem to be the main cause of the interface state generation and the dielectric breakdown of thin-gate SiO2. Positron annihilation experiments show that the positron diffuse along the electric field in the Si and the gate SiO2 and are trapped in the interface region before annihilation. The obtained value of 5 at the SiO2/Si interface was 0.500 ±0.003. The behavior of holes in the SiO2 and SiO2/Si interface are simulated using the monoenergetic positron annihilation technique.
Defects Introduced by Low Dose Be-Implantation Probed by a Monoenergetic Positron Beam
Authors: Uedono A. , Ujihira Y. , Wei L. , Tabuki Y. , Tanigawa S. , Wada K. , Nakanishi H. 
Published: September 2012

ABSTRACTVacancy-type defects in 60-keV Be+-implanted GaAs and InP were studied by a monoenergetic positron beam. The depth distributions of vacancy-type defects were obtained from measurements of Doppler broadening profiles of the positron annihilation as a function of incident positron energy. Vacancy-type defects introduced by ion implantation were observed in n-type GaAs. For p-type GaAs, however, this was not the case. This can be attributed to the recombination of vacancy-type defects and pre-existed interstitial-type defects in p-type GaAs. The defects induced by ion implantation in InP were also studied.