bluuebunny/crossref_metadata_2025 huggingface dataset:
Nucleation of Oxygen Precipitates in a Quenched Czochralski Silicon Crystal
Authors: Ikari A. , Haga H. , Yoda O. , Uedono A. , Ujihira Y.
Published: September 2012

We have studied the nucleation of oxygen precipitates in Czochralski (Cz) Si crystal quenched from high temperature (1390°C). We observed that the oxygen precipitation was enhanced by the quenching treatment. We found the density of precipitates in the quenched crystal depended on quenching temperature and that nuclei for oxygen precipitates were introduced during quenching. We studied these nuclei using infrared absorption (IR) and positron annihilation techniques. In order to clarify the state of the nuclei, the quenched specimens were irradiated with 3-MeV electrons at a dose of 1×1018e/cm2and vacancy-oxygen complexes were introduced. Positron lifetime spectra and IR absorption spectra for these specimens were measured as a function of isochronal annealing temperature. From the annealing behavior of the vacancy-oxygen complexes, it was found that oxygen clusters are introduced by the quenching and these clusters are the nuclei for the enhanced precipitation of the quenched Si crystal.
Effects of Concurrent Co or Ti Silicidation on Transient Diffusion and End-of-Range Damage in Phosphorus Implanted Silicon
Authors: Honeycutt J.W. , Ravi J. , Rozgonyi G. A.
Published: September 2012

The effects of Ti and Co silicidation on P+ ion implantation damage in Si have been investigated. After silicidation of unannealed 40 keV, 2×1015 cm-2 P+ implanted junctions by rapid thermal annealing at 900°C for 10–300 seconds, secondary ion mass spectrometry depth profiles of phosphorus in suicided and non-silicided junctions were compared. While non-silicided and TiSi2 suicided junctions exhibited equal amounts of transient enhanced diffusion behavior, the junction depths under COSi2 were significantly shallower. End-of-range interstitial dislocation loops in the same suicided and non-silicided junctions were studied by planview transmission electron microscopy. The loops were found to be stable after 900°C, 5 minute annealing in non-silicided material, and their formation was only slightly effected by TiSi2 or COSi2 silicidation. However, enhanced dissolution of the loops was observed under both TiSi2 and COSi2, with essentially complete removal of the defects under COSi2 after 5 minutes at 900°C. The observed diffusion and defect behavior strongly suggest that implantation damage induced excess interstitial concentrations are significantly reduced by the formation and presence of COSi2, and to a lesser extent by TiSi2. The observed time-dependent defect removal under the suicide films suggests that vacancy injection and/or interstitial absorption by the suicide film continues long after the suicide chemical reaction is complete.
Defect Annihilation in Czochralski-Grown Silicon During Out-Diffusion Process Probed with Variable-Energy Positron Beam
Authors: Kitano T. , Wei L. , Tabuki Y. , Tanigawa S. , Mikoshiba H.
Published: September 2012

The defect annihilation in CZ-crystal was first detected during the process of oxygen out-diffusion, by the positron measurements with a variable-energy beam. The defects, which were related to oxygen atoms such as oxygen cluster, were mainly annihilated at the high temperature, ex., 1150°C. The defect concentration was decreasing down to one tenth, compared with that for an as-grown crystal.
Effects of Fluorine on MOS Properties
Authors: Ma T. P.
Published: September 2012

The incorporation of small amounts of fluorine has been found to improve the properties of MOS devices. In this paper, some of these results will be reviewed, several techniques to introduce fluorine will be described, the distributions of F resulting from these processes will be shown, and the possible mechanisms leading to the improved MOS device reliability will be discussed.
Depth Profiles of Thermal Donors in Czochralski-Grown N-Type Silicon
Authors: Tokuda Yutaka , Shimokata Toshihisa , Katayama Masayuki , Hattori Tadashi
Published: September 2012

Depth profiles of thermal donors introduced by heat treatment at 450°C in Czochralski-grown n-type silicon have been studied through capacitance-voltage measurements of Au Schottky diodes in the oxygen concentration range 8.1×1017 to 15.3×1017 cm3 Thermal donor concentrations increase with depth and their depth profiles are fitted to the error function equation. The obtained diffusivity decreases with annealing time and is higher for samples with the lower initial oxygen concentrations. Combining with the infrared absorption measurements, it is found that the curves of the diffusivity as a function of loss of interstitial oxygen coincide with each other. The similar tendency is observed on the oxygen diffusivity evaluated with secondary ion mass spectrometry. These results indicate that the oxygen diffusivity at 450°C is related to both the outdiffusion and clustering of oxygen. Depth profiles of thermal donors formed at 650°C are also reported.
Effects of Deliberate Metal Contamination on CCD Imagers
Authors: McColgin William C. , Lavine J. P. , Kyan J. , Nichols D. N. , Russell J. B. , Stancampiano C. V.
Published: September 2012

The effects of intentional metal contamination on silicon charge-coupled device imagers are reported. Such imagers are both sensitive to and provide sensitive measures of the presence of metals in the fabrication process. High-purity iron, cobalt, nickel, copper, palladium, and gold were deliberately introduced into the device wafers just before the last high temperature step. Metals were found to cause both electrical defects and distinctive imaging defects.

We find that transition metals can be effectively removed from device regions by internal gettering, but that this gettering can be defeated by a fast cool-down. Gold, however, is poorly gettered.
Some Possibilities of using Defects for Applications in Semiconductors
Authors: Lannoo Michel
Published: September 2012

Specific situations where defects have a positive impact on the properties of semiconductors are examined. In a first category are ranged defects used as probes for characterizing materials. Then semiconductors with high concentration of defects like low temperature GaAs and porous Si are discussed. This is followed by cases where direct use is made of the defect properties (optical, pressure…). Finally several possibilities for defect engineering of materials are reviewed.
Drain Current DLTS Spectra and GaAs Substrate Crystal Effect on Low-Frequency-Oscillations of Si-Implanted Mesfets
Authors: Saito Yasuyuki , Suga Tohru , Inoue Kazuhiko , Mitani Tatsuro , Tomizawa Yutaka , Nishio Johji , Terashima Kazutaka , Katsumata Tohru , Fukuda Katsuyoshi , Washizuka Shoichi , Yashiro Satao , Tarami Shigeoki , Nakajima Masahiro , Watanabe Masayuki
Published: September 2012

We report drain-current (Id) deep level transient spectroscopy (DLTS) spectra and liquid-encapsulated-Czochralski-technique (LEC) GaAs crystal effect on low-frequency-oscillation (LFO) of wide gate (400-μm) Si-implanted GaAs metal- semiconductor field- effect- transistors (MESFETs). In the range of this experiment we could not find distinguishing DLTS peaks surely to be linked with Id-LFO of the MESFETs. Stoichiometric-melt growth LEC-boules showed relatively large Id-LFO phenomena. As-rich-melt growth LEC-boules showed tolerance to Id-LFO. We conclude that Id-LFO is not directly linked to deep centers themselves but interaction between deep centers and potential profiles and electrons. Stability of potential profile or band profile depends on “pinning’ center, which affects Fermi-level or quasi-Fermi-level stability. ‘Pinning’ center such as EL2s of ‘LEC GaAs crystals” is essential.
Comparison of Current-Induced Migration of Be and C in GaAs/AlGaAs HBTs
Authors: Ren F. , Fullowan T. R. , Lothian J. R. , Wisk P. W. , Abernathy C. R. , Kopf R. F. , Emerson A. B. , Downey S. W. , Pearton S. J.
Published: September 2012

We contrast the stability under bias-aging conditions of GaAs/AlGaAs HBTs utilizing highly Be- or C-doped base layers. Devices with Be doping display a rapid degradation of dc current gain and junction ideality factor. At 200°C, a 2 × 10 μm2 Be-doped device (4 × 1019cm−3 base doping) operated at a current density of 2.5 × 104 A. cm−2 shows a decrease in gain from 16 to 1.5 within 2h. Under the same conditions a C-doped device with even higher base-doping (7 × 1019 cm−3) is stable over periods of 36h, the longest time we tested our structures. The degradation of Be-doped devices is consistent with the mechanism of recombination-enhanced diffusion of interstitials into the adjoining layers. Similar results are obtained with Zn-doped devices. Since C occupies the As sub-lattice rather than the Ga sublattice as with Be and Zn, it is not susceptible to reaction with Ga interstitials injected during growth or bias-aging.
Dislocations as Sinks for Self-Interstitials in Gold Doped Float Zone Silicon
Authors: Mariani G. , Pichaud B. , Taylor W. J. , Yang W. -S.
Published: September 2012

Self-interstitial sink efficiencies of dislocations γ were measured in gold doped FZ (111) and (100) samples, we found respectively γ=0.4–0.5 and γ=0.2–0.3. γ is probably sensitive to dislocation character and to the deformation process.
Vacancy Promoted Interdiffusion in Quantum Wells and Applications to Optoelectronic Devices
Authors: Ghisoni M. , Rivers A. W. , Lee K. , Parry G. , Zhang X. , Staton-Bevan A. , Pate M. , Hill G. , Button C. , Roberts J. S.
Published: September 2012

In this paper we shall look at a technique, known as impurity free vacancy diffusion (IFVD) for selectively altering the optoelectronic response of quantum well material after growth with a view to monolithic device integration. We will discuss the mechanism, practical considerations and some possible applications.
Visible Luminescence from Silicon: Quantum Confinement or Siloxene?
Authors: Brandt M. S. , Fuchs H. D. , Höpner A. , Rosenbauer M. , Stutzmann M. , Weber J. , Cardona M. , Queisser H. J.
Published: September 2012

The discovery of strong visible photoluminescence at room temperature from porous silicon has triggered new hope that light-emitting devices compatible with existing Si-technology might become possible. We first review the luminescence behavior observed in silicon-based materials such as amorphous Si, microcrystalline Si, or SiO2. We then critically discuss the present model for the luminescence from porous silicon based on quantum confinement in view of the growing experimental evidence for the importance of both hydrogen and oxygen to obtain efficient luminescence from this material. We propose an alternative explanation based on the presence of siloxene (SieO3H6) in porous silicon which is corroborated by experimental results obtained with photoluminescence, Raman and IR spectroscopy. An important aspect is that siloxene can be prepared by methods different from anodic oxidation, and one particular technique will be described together with possible ways to tune the luminescence energy.
A Consistent Model for Disordering of GaAs/AlAs- Superiattices During Zinc Diffusion
Authors: Zimmermann H. , Tan T. Y. , Goesele U.
Published: September 2012

A model for the disordering of GaAs/AlAs-superlattices during zinc diffusion, which is consistent with recently established models for gallium self-diffusion and zinc diffusion in GaAs, is presented. Four coupled partial differential equations resulting from the model are solved numerically. In accordance with measured data in the literature, no disordering without zinc can result for temperatures around 600°C. Zinc diffusion, however, produces a large amount of gallium self-interstitials, which leads to a complete disordering of superlattices with a period thickness of 32 nm to a depth of about 0.8 μm within one hour. The used values for the diffusion coefficient and the equilibrium concentration of gallium self-interstitials are a consistent splitting of the gallium interstitial dominated self-diffusion coefficient.
Electron Accumulation in AIGaSb/InAs Qw System, - Evidence for Coexistence of Deep Acceptor and Donor -
Authors: Ideshita S. , Furukawa A. , Mochizuki Y. , Mizuta M.
Published: September 2012

We investigated the reason of the (imbalanced) accumulation of electrons in AIGaSb/lnAs/AIGaSb QW system in spite of the p-type conduction of undoped AIGaSb. It was found that the concentration of the accumulated electrons negligibly depended on the number of the interfaces, but increased linearly with the effective AlSb thickness. These results indicate that donor levels in AIGaSb are the dominant electron sources. We propose a model that the deep acceptors with larger concentration and donors coexist, and the electron accumulation depends on the energy position of the acceptor in AIGaSb with respect to the quantum level in the InAs well. Acceptor levels obtained experimentally are about 100 meV higher than the bottom of the InAs conduction band, and we succeeded in eliminating the electron accumulation by making the quantum level of the InAs well higher than this acceptor level. The origins of the donors and acceptors are also discussed.
Effect of Lt GaAs on Epitaxial Al/GaAs Schottky Diode Characteristics
Authors: Zhang Kai , Miller D. L.
Published: September 2012

The effect of LT GaAs on the effective barrier height of the epitaxial Al/GaAs Schottky contact was investigated for the first time by inserting a thin LT GaAs layer (50 ∼ 500Å) between the in situ deposited Al film and conventional MBE GaAs epitaxial layer. The activation energy plot of saturation current for the devices showed that the effective barrier height exhibits a dependence on LT GaAs thickness and reaches a saturated barrier height when the LT GaAs layer exceeds a critical thickness. Compared to the samples which had no LT GaAs layer, the effective Schottky barrier height was decreased from 0.79 eV to 0.35 eV for the n-GaAs samples, and increased from 0.55 eV to 0.72 eV for the p-GaAs samples. The Schottky barrier height modification achieved by LT GaAs is tentatively explained in the terms of a bulk Fermi level pinning model. The work described here suggests that LT GaAs can be used as a defect source with controlled thickness to study defect associated phenomena such as Schottky barrier height modification.
Effects of Rapid Thermal Annealing on SiNx Capped MBE GaAs
Authors: Ito Akira , Usami Akira , Ueda Hiroyuki , Kano Hiroyuki , Wada Takao
Published: September 2012

Effects of rapid thermal annealing (RTA) with a SiNx encapsulant on molecular beam epitaxial GaAs are studied with deep level transient spectroscopy (DLTS) measurements and x-ray photoelectron spectroscopy (XPS) measurements. The RTA was performed at various temperatures form 800°C to 1100°C for 6sec. The electron trap EL2 is produced by the RTA above 850°C The EL2 depth profile produced after the RTA is fitted with a complementary error function. The SiNx cap layer is more effective to prevent the formation of the EL2 than the SiO* cap layer during the RTA, because the critical temperature of the SiNx cap where the EL2 concentration starts to increase is higher than that of the SiOx cap. Slight increase of the oxidized Ga atoms is observed after the RTA near the cap surface. The enhancement of the EL2 trap is discussed considering the outdiffusion of Ga atoms into the cap layer during the RTA.
The Diffusivtty-Mobility Ratio Under Strong Magnetic Field in Small Gap Superlattices with Graded Structures
Authors: Ghatak Kamakhya P. , De Badal
Published: September 2012

In this paper we have studied the Einstein relation for the diffusivity-mobllity ratio (DMR) in small-gap superi at tices (SLS) with graded structures under magnetic quantization by formulating a new dispersion law. It is found, taking inAs/ GaSb SL as an example that the DMR increases in an oscillatory way with increasing carrier degeneracy due to SdH effect. The DMR in SL. is greater than that of the constituent materials. The theoretical results are in agreement with the suggested experimental method of determining the DMR in degenerate materials having arbitrary dispersion laws.
Relaxation-Induced Gettering of Metal Impurities in Silicon: Microscopic Properties of Effective Gettering Sites
Authors: Seibt M.
Published: September 2012

Some gettering processes like internal gettering or backside damage gettering base on heterogeneous precipitation of metal impurities at defects in pre-de ter mined parts of silicon wafers during cooling from high temperatures. We consider microscopic properties of effective heterogeneous nucleation sites for cobalt, nickel and copper impurities from the fundamental point of view of suicide precipitate formation. We follow the basic concept that such gettering sites are defects which allow fast precipitation, i.e. which remove kinetic limitations known from homogeneous precipitation of these impurities at small supersaturation. For Co and Ni it follows that distorted lattice sites in the core of dislocations may establish high incorporation rates of interstitial atoms into suicide particles, whereas for Cu sinks for silicon self-interstitials are suitable gettering sites.
Intrinsic Gettering of Iron in Czochralski Silicon Crystals
Authors: Aoki M. , Hara A. , Ohsawa A.
Published: September 2012

We present a new experimental approach to studying the mechanism of intrinsic gettering of Fe in Czochralski silicon crystals. We present our experimental method and results for as-grown and intrinsic gettered wafers with high and low-level Fe surface contamination. We found that when annealing at the Fe supersaturation temperature, Fe concentration decreases faster in intrinsic gettered wafers than in as-grown wafers. Concentration saturated with annealing time for each sample and the saturated Fe concentration followed a simple Arrhenius relationship. Re-emission of Fe from the bulk defect region occurred above the gettering temperature. We conclude that in intrinsic gettering, Fe precipitates preferentially in the bulk defect region when the Fe impurities supersaturate as temperature drops.
Influence of Rapid Thermal Annealing on Recombination Properties of Polycrystalline Silicon
Authors: Kittler M. , Seifert W.
Published: September 2012

Rapid thermal annealing was shown by EBIC to increase the minority-carrier diffusion length in cast polycrystalline silicon. The beneficial effect is due to a deactivation of intragrain defects (mainly dislocations) and is stable against post-RTA annealing up to at least 600 °C/ 10 min.
Persistent Photo-Hall Phenomenon and Near-Bandedge Absorption in Lightly N-Type Lec GaAs
Authors: Tüzemem S. , Brozel M. R.
Published: September 2012

The novel infrared imaging technique for assessment of undoped semi-insulating (SI) GaAs substrates known as Reverse Contrast is known to result from absorption from point defects whose concentrations approximately anti-correlate with those of EL2, deep donor defects. The absorption that occurs within - 65 meV of Eg in cooled samples is sufficiently strong that commercial wafers can be mapped with simple infrared CCTV imaging equipment. RC defects are thought to be very deep acceptors with an ionization energy close to the Conduction Band. Concentrations of RC defects are not measurable in SI GaAs as they are un-ionized in the dark. Like EL2 defects they can be photo-quenched by irradiation with mid-gap light.

In this paper, we present novel Hall Effect measurements on very lightly Te-doped n-type GaAs where at least a fraction of RC defects are ionized. A permanent increase in the carrier concentration is observed after photo-quenching corresponding to the bleaching of RC defects. The carrier concentration returns to its initial value at the same temperature at which the absorption of RC defects is recovered. This result allows a calibration for the absorption coefficient to be found.
Electronic Theory of Gettering and Passivation of Impurities in Semiconductors
Authors: Masuda-Jindo K.
Published: September 2012

We calculate the interaction (segregation) energies Egegr between the extended lattice defects (dislocations and grain boundaries) and impurity atoms in semiconductors by using a microscopic electronic theory. In particular, we use the tight-binding recursion method coupled to the generalized zeros-and poles method and investigate the interaction between the extended lattice defects and various kinds of the impurity atoms in semiconductors (Si). For the systematic understanding of the impurity gettering, we consider a wide variety of impurities, both sp-valence and transition metal impurities, Ti, V, Cr, Mn, Fe, Co, Ni and Cu. We will show that the variation of the gap states plays an important role in determining the interaction energy Esegr between the impurity atom and the extended lattice defects- We also discuss the passivation of the extended lattice defects by interstitial light impurities like hydrogen in Si crystal, we present a simple physical interpretation of the impurity gettering and passivation in semiconductors.
Magnetic and Transport Behavior of Af-Coupled Layers with a Limited Number of Repetitions
Authors: Willekens M.M.H. , Swagten H.J.M. , Duif A.M. , Bloemen P.J.H. , Van Kempen R.J.T. , Lenczowski S.K.J. , De Jonge W.J.M.
Published: September 2012

We investigated the magnetization behavior of [(Co/Pd) 4-Ru]x samples with perpendicular anisotropy and a limited number of repetitions (x = 1,‥,22). In these systems the Co/Pd Multilayers behave as single magnetic entities. A detailed analysis and comparison of the magnetization curves observed by MOKE and VSM permits us to observe the magnetization reversal and hysteresis of the individual layers and to determine the antiferromagnetic coupling J between each pair of layers. A gradual increase in J is observed in all samples when going from the bottom layer to the top layer. Magnetoresistance curves show the same sharp transitions as the magnetization curves. A clear distinction can be made between an outer layer and an inner layer. These results will be compared with model calculations.
Electronic States in Magnetic Quantum Wells
Authors: Ortega J. E. , Himpsel F. J. , Mankey G. J. , Willis R. F.
Published: September 2012

We have searched for the electronic states that mediate oscillatory magnetic coupling in superlattices, and have found strong evidence that these are quantum well states, which are created by quantizing the momentum of s,p-band states perpendicular to the interfaces. The quantum well picture also explains how quantum well states in noble metals become spin-polarized, due to a spin-dependent electron reflectivity at the interface with the ferromagnet. The resulting implications for magnetoresistance are discussed.
Quantum well States in Fe (100) Ultrathin Films Observed by Magneto-Optical Effect
Authors: Suzuki Yoshishige , Katayama Toshikazu
Published: September 2012

We report on the Magneto-optical Kerr rotation (<φ>K) spectra of ultrathin Fe films on Au or Ag (100) substrates and the φK oscillation due to interlayer thickness in Fe/Au/Fe sandwich films. In 3.5–4.5 eV, a new φK peak appears in the bcc-Fe (100) ultrathin films on the fcc-Au (100) surface and it shifts towards the higher energy side with increasing Fe layer thickness. The absolute value of eXy for 3Å (2ML) thick Fe layers is twice as large as that of bulk Fe at 3.7 eV. The thickness dependence of the transition energy of this new peak in the spectra is well explained by the concept of quantum well states in the Fe ultrathin layers, attributing the new transition to a transition from the majority spin Δ5 band ({px±i py), {dxz±i dyZ}; M=±l) to the Δ1 quantum well states (s, pz, dz2; M=0). The new peak is also observed in the Fe/Au (100) artificial superlattices. Using the εxy obtained experimentally for the Fe ultrathin films and the εxy of literature, we can reproduce the experimental φK spectra of the artificial superlattices by optical calculation. On the other hand, we cannot observe the same behavior for the ultrathin Fe films grown on a fcc-Ag (100) surface and covered by a Au (100) ultrathin film, although the εXy of Fe is different from that of the bulk and shows some structures in 2–3 eV. These structures around 2.5 eV are thought to be due to polarized Au atoms adjacent to an Fe layer.

An oscillation of φK as a function of interlayer thickness, d, was observed in photon energy region between about 2.5 and 3.8 eV for the Fe (6Å) /Au (dÅ) /Fe (6A) sandwiched film. The oscillation period was about 10Å (5ML) of Au. The oscillation is thought to be closely related with a formation of spin polarized quantum well states of Δ1 band in Au layers sandwiched by magnetic layers.
Quantum-Well Contributions to the RKKY Coupling in Magnetic Multilayers
Authors: Jones B. A. , Hanna C. B.
Published: September 2012

We study the effects of quantum-well states on the calculated RKKY coupling. We find that the bound states of a finite-size potential well of depth V give an added oscillation period of size For the simplest case of a spherical free-electron Fermi surface, thus two periods appear: the original, “fast,” π/kf oscillation, and the quantum-well one The quantum-well contributions have larger amplitude, and are in fact the predominant oscillation. For physically reasonable V (tenths of an eV) this period is around 8–10Å. We discuss evidence for these effects in experimental systems.
Increase in Period of Oscillatory Coupling in Cu by Doping with Ni
Authors: Parkin S.S.P. , Chappertt C , Herman F.
Published: September 2012

The origin of oscillatory interlayer coupling via Cu is explored in sputtered Co/Cu Multilayers by varying the hole concentration in the copper layers by doping with elements of different valence. Detailed studies were carried out for a series of Cu-Ni alloys. The oscillation period of pure Cu is observed to increase monotonically with increasing Ni concentration and is almost doubled for 40 atomic % Ni. The increase in oscillation period can be accounted for by considering changes in the topology of (he Fermi surface of the alloy resulting from the change in band Tilling.
Giant Magnetoresistance in Sputtered NIFE/AG Multilayers
Authors: Rodmacq B. , Mallon A. , Gerard Ph.
Published: September 2012

The Magnetoresistive properties of sputtered Ni8.1Fe1.9/Ag Multilayers have been investigated as a function of both Ag and NiFe layer thicknesses and thermal treatments. For the virgin sample, the Magnetoresistance (MR) ratio at room temperature goes through a maximum of 17% for a Ag thickness of about 11 A. In addition, the R (H) curve is found to be perfectly linear and reversible. Contrary to the MR ratio, the saturation field is observed to decrease continuously as the Ag thickness increases, leading to an increasing slope of the R (H) curves. Upon annealing, we observe both an increase of the MR ratio and a decrease of the saturation field, leading to a three fold increase of the MR slope for annealing temperatures of 280°C. Such a behavior appears to be highly dependent on the layer thicknesses.
Giant Magnetoresistance in Co/Ag Multilayers
Authors: Tan M. , Barnard J. A. , Parker M. R. , Seale D.
Published: September 2012

The Magnetoresistance (MR), Magnetic properties, and crystal structure of dc magnetron sputtered CO/Ag periodic multilayers have been investigated. The Co layer thickness was fixed at -30 Å while the thickness of the Ag layer was systematically varied. ‘Giant’ magnetoresistance was observed. The MR ratio has been found to decline monotonically with increasing Ag thickness in the range 30 Å to 107 Å. Although the maximum room temperature MR ratio is a Modest 4.78%, a more technologically significant measurement of field sensitivity (MR ratio/FWHM of the MR vs. H peak) is a promising 0.1%/Oe at its best. The effect of the number of bilayer units has also been examined and no substantial differences were noted between multilayers containing 8, 9, and 10 bilayer units. Coercivities as determined by both magnetometer and the splitting of the MR peaks are in agreement and increase from 25 to 38 Oe with increasing Ag thickness. Evidence for antiferromagnetic coupling is apparent in the hysteresis loops. High angle X-ray diffractometry (HXRD) in the θ-2θ mode revealed a strong Ag (111) texture in the film, with satellite peaks indicating a layered structure. Low angle XRD (LXRD) also yielded broad superlattice peaks in all samples at least to the second order.
Giant Magnetoresistance in Annealed Fe/Cr Multilayers
Authors: Rensing Noa More , Clemens Bruce M.
Published: September 2012

The giant magnetoresistance effect in antiferromagnetically coupled Fe/Cr Multilayers has been attributed to spin dependent scattering at the interfaces between the constituents. One possible source of this spin dependent scattering is chromium impurities in the iron layers due to intermixing at the interfaces. Annealing the films can promote the diffusion of the components, increasing the impurity concentration and therefore the Magnetoresistance. For this study Fe/Cr Multilayers were annealed at several temperatures and for several durations. Annealing at moderate temperatures (∼ 350°C) increases the Magnetoresistance, while higher temperature anneals (∼ 600°C) cause the magnetoresistance to disappear completely. Long anneals at 330°C (> 100 hours) also reduce the Magnetoresistance. VSM Measurements indicate that the antiferromagnetic coupling is reduced in the annealed samples but show no evidence of Magnetically “dead” alloy layers. Low angle X-ray diffraction indicates that the structural effect of annealing is very subtle in comparison to the significant magnetic effect.
Grain Boundary Diffusion in Co/Cu and Co/Cr Magnetic Thin Films
Authors: Holl-Pellerin John G. , Anderson S.G.H. , Ho P.S. , Coffey K.R. , Howard J.K. , Barmak K.
Published: September 2012

X-ray photoelectron spectroscopy (XPS) has been used to investigate grain boundary diffusion of Cu and Cr through 1000 Å thick Co films in the temperature range of 325°C to 400°C. Grain boundary diffusivities were determined by modeling the accumulation of Cu or Cr on Co surfaces as a function of time at fixed annealing temperature. The grain boundary diffusivity of Cu through Co is characterized by a diffusion coefficient, D0gb, of 2 × 104cm2/sec and an activation energy, Ea,gb, of 2.4 eV. Similarly, Cr grain boundary diffusion through Co thin films occurs with a diffusion coefficient, Do,gb, of 6 × 10-2cm2/sec and an activation energy, Ea,gbof 1.8 eV. The Co film microstructure has been investigated before and after annealing by x-ray diffraction and transmission electron Microscopy. Extensive grain growth and texturing of the film occurred during annealing for Co deposited on a Cu underlayer. In contrast, the microstructure of Co deposited on a Cr underlayer remained relatively unchanged upon annealing. Magnetometer Measurements have shown that increased in-plane coercivity Hc, reduced remanence squareness S, and reduced coercive squareness S*result from grain boundary diffusion of Cu and Cr into the Co films.
Quantitative Analysis of Polarized Neutron Specular Reflectivity from a Co/Cu (111) Superlattice at the Second Antiferromagnetic Maximum
Authors: Ankner J.F. , Schreyer A. , Majkrzak C.F. , Bröhl K. , Zeidler Th. , Bödeker P. , Zabel H.
Published: September 2012

We have used polarized neutron reflectivity to prove the existence of oscillatory coupling in MBE-grown Co/Cu (111) superlattices. For a sample of composition [3.4 nm Co/2.0 nm Cu]10, we find that only a small fraction of the sample volume exhibits coherent antiferromagnetic order, with the structure of the remainder of the film being attributable to ferromagnetic domains and small disordered structures.
Observation of X-Ray Absorption Magnetic Circular Dichroism in well-Characterized Iron-Cobalt-Platinum Multilayers
Authors: Jankowski A.F. , Waddill G.D. , Tobin J.G.
Published: September 2012

Magnetic circular dichroism in the Fe 2p x-ray absorption is observed in multilayers of (Fe9.5Å/Pt9.5Å)92. The Magnetization and helicity are both in the plane of this multilayer which is prepared by magnetron sputter deposition. This sample is part of a study to examine magnetization in the ternary multilayer system of FeCo/Pt. Lattice and layer pair spacings are measured using x-ray scattering. The atomic concentration profiles of the multilayer films are characterized using Auger electron spectroscopy coupled with depth profiling. Conventional and high resolution transmission electron microscopy are used to examine the thin film, growth morphology and atomic structure.
Magnetic Properties of Epitaxial 6 ML fcc-Fe/Cu (100) Films
Authors: Swartzendruber L. J. , Bennett L. H. , Kief M. T. , Egelhoff W. F.
Published: September 2012

A study has been made of the magnetic properties of epitaxial 6 Monolayer (ML) fcc-Fe films on Cu (100) with various thicknesses of epitaxial Cu deposited on top of the Fe. It was found that the magnetic properties undergo striking changes as a function of the Cu thickness. The easy axis of magnetization goes from being in-plane for the bare Fe to perpendicular upon the deposition of 1 ML Cu. Concurrently there is a dramatic decrease in the Kerr signal intensity at saturation. Upon depositing a second ML of Cu the Kerr signal intensity more than doubles, and the easy axis remains perpendicular. For Cu overlayers of 3 ML to 10 ML the Kerr signal intensity at saturation gradually diminishes to below the level of detectability, as if the Fe were nonmagnetic. A superlattice consisting of 60 ML Cu/ (6 ML 57Fe/10 ML Cu)×5/Cu (100) was fabricated and studied at room temperature by conversion electron Mòssbauer spectroscopy. The results confirmed that the Fe is indeed nonmagnetic. The four inner Fe layers of the 6 ML film have the same isomer shift as bulk fcc-Fe in precipitates in Cu, and the two boundary Fe layers exhibit an asymmetric quadrupole doublet.
In Situ Rheed and Magneto-Optic Study of Ultrathin Cobalt Films on (111) Gold Substrate: Effect of a Metallic Overlayer
Authors: S Ould-Mahfoud , R. Megy , N. Bardou , B. Bartenlian , P. Beauvillain , C Chappert , J. Corno , B. Lecuyer , G. Sczigel , P. Veillet , D. Weller
Published: September 2012

We present a comparative in situ RHEED and Polar Magneto-optic Kerr Effect study of the first stages of the growth of a Au overlayer on top of a (111) Co ultrathin film. Drastic behaviours are evidenced on the RHEED diagram, Magnetic anisotropy and coercive force, around 1,5 ML of Au coverage.
Theoretical Studies on the Magnetic Moments of Iron Nitrides Including Fe16N2
Authors: Sakuma Akimasa , Sugita Yutaka
Published: September 2012

The spin-polarized band calculations for the iron nitrides, Fe3N, Fe4N and Fe16N2, have been performed with use of LMTO-ASA Method in the frame of local spin density functional formalism. The results show that the most distant Fe atoms from N have the largest magnetic moment. The central role of the N atom is to bring about the large magnetic moments through the lattice expansion. Concurrently, the N atoms promote an itinerancy of electrons and then in turn prevent the exchange-splitting. This results in an Fe16N2 with the lowest N concentration having the largest magnetic moments. Quantitatively, the obtained magnetic moments are in fair agreements with the experimental results except for Fe16Nr The calculated magnetic moment of Fe6N2 is about 2.4 ΜB/Pε, while the measured value is reported as 3.5 ΜB/FB. The orbital magnetic moment of Fe16N2 is about 0.07 ΜB, which is too small to make up for the difference from the experimental value.
A Tight-Binding Study of Very Thin Transition Metal Film Magnetic Anisotropy
Authors: Pick S. , Dreysse H.
Published: September 2012

We discuss shortly some problems that have been met in recent systematic calculations of the magnetic anisotropy energy (MAE) performed by the present authors as well as in studies of other investigators. As an example, we present MAE for ferromagnetic (001) bilayers with antiferromagnetic inter-plane coupling and for an antiferromagnetic (001) Monolayer. It appears that antiferromagnetism can invoke specific effects and under certain conditions, both MAE and magnetic orbital moment are strongly enhanced.
Magnetization Reversal in CoPt Magnetooptic Recording Alloys
Authors: Kleinefeld T. , Kim W.S. , Valentin J. , Weller D.
Published: September 2012

High resolution Kerr Microscopy has been used to study newly developed Co25Pt75 alloy films with perpendicular magnetic anisotropy. In particular, the dynamics of magnetization reversal processes wase investigated by means of time resolved domain pattern analysis. Domain wall motion dominated magnetization reversal as well as nucleation dominated processes were observed. Magnetic aftereffect phenomena were confirmed by relaxation measurements of magnetic domains. The fractal dimension of the observed domains is correlated to the macroscopic coercivity determined from hysteresis loop Measurements.
Neutron and X-Ray Scattering Studies of (FeF2) M (CoF2)n Multilayers
Authors: Lederman D. , Belanger D. P. , Wang J. , Han S-J. , Paduani C. , Ramos C. A. , Nicklow R. M.
Published: September 2012

We have performed elastic neutron scattering measurements of the staggered magnetization in (FeF2) M (CoF2) n superlattices. Thermal expansion Measurements, which are proportional to the magnetic contribution to the specific heat, were also carried out using high resolution x-ray diffraction. One of the two measured samples has thicknesses of M = n = 4.5 and the other M = 26 and n = 28 Monolayers, as determined from high angle x-ray θ — 2θ scans. In the M = n = 4.5 sample, only one transition is observed at T/v = 62.9K. Analysis of the neutron data, including the rounding effects, indicates an effective β ≈ 0.42. This does not compare well with the 3D Ising exponent β = 0.325. The X-ray data also show the existence of only one specific heat anomaly at T = 62.8 K. For the M = 26, n = 28 sample, dips in the staggered magnetization and peaks in the thermal expansion were observed at T ≈ 40 K and 74 K. The higher temperature anomaly, associated primarily with the FeF2 layers, is sharper than the lower one, which is presumably rounded by the staggered ordering field imposed by the long range order in the FeF2 regions on the CoF2 regions.
Magnetostriction and Stress in High Moment FeTaN Films
Authors: Cates J. C. , Qiu G. , Haftek E. , Alexander C. , Barnard J. A.
Published: September 2012

Magnetostriction and thin film stress have been studied in high moment single layer FeTaN films deposited by high rate reactive dc magnetron sputtering. Low Magnetostriction (Magnitude less than 1 × 10-6) can be obtained over a fairly large range of nitrogen flow rates during film deposition by vacuum annealing at 500°C. After annealing at 500°C for two hours, all films were found to be in a state of tensile stress. Stress versus temperature measurements up to 400°C show film stress in as-deposited films to be highly hysteretic during the first temperature cycle reflecting the films' processing history. Stress-temperature cycles on annealed samples indicate that extremely stable films are produced in an intermediate range of nitrogen content.
Ferrimagnetic Cobalt Ferrite Films Prepared by the Sol-Gel Process
Authors: Wong Eva M. , Zheng Haixing , Mackenzie John D. , Tsuchiya T.
Published: September 2012

Ferrimagnetic oxide films have been shown to have potential for use as Magneto-optical information storage Materials. Cobalt ferrite films are particularly interesting for magneto optical information storage due to their high magneto optical rotation [1]. In this work, synthesized soluble cobalt (II) and iron (III) Methoxyethoxides were mixed in stoichiometric ratios for use as Co and Fe precursors in the preparation of CoFe2O4ferrimagnetic films. The decomposition of the precursors was characterized by thermogravimetric analysis.

CoFe2O4 films were prepared by the dip coating technique using fused silica substrates. These films were then heat treated at temperatures ranging from 200°C to 600°C to study the transformation from an amorphous film to a crystalline film as determined by x-ray diffraction. The Magnetic hysteresis behavior of the films as a function of heat treating temperature and hence crystallinity was also studied. As a general trend, films having a greater degree of crystallinity exhibited larger values of saturation magnetization and remanent Magnetization. The amorphous film was found to exhibit the highest coercive field, but low values of saturation and remanent Magnetization. The effect of heat treating under the influence of a magnetic field of 1.88 kÖe was found to enhance crystallization only slightly and had very little effect on the magnetic properties of the film.
In Situ Analysis of magnetic and Structural Properties of Epitaxial and Polycrystalline Ni80Fe20 Thin Films
Authors: Hashim I. , Atwater H.A. , Watson Thomas J.
Published: September 2012

We have investigated structural and magnetic properties of epitaxial Ni80Fe20 films grown on relaxed epitaxial Cu/Si (001) films. The crystallographic texture of these films was analyzed in situ by reflection high energy electron diffraction (RHEED), and ex situ by x-ray diffraction and cross-sectional transmission electron Microscopy (XTEM). In particular, RHEED intensities were recorded during epitaxial growth, and intensity profiles across Bragg rods were used to calculate the surface lattice constant, and hence, find the critical epitaxial thickness for which Ni80Fe20 grows pseudomorphically on Cu (100). XTEM analysis indicated that the epitaxial films had atomically-abrupt interfaces which was not the case for polycrystalline Cu and Ni80Fe20 film interfaces. The Magnetic properties of these epitaxial films were Measured in situ using Magneto-optic Kerr effect magnetometry and were compared with those of polycrystalline films grown on SiO2/Si. Large Hc (∼ 35 Oe) was observed for epitaxial Ni80Fe20 films less than 3.0 nm thick whereas for increasing thickness, Hc decreased approximately monotonically to a few Oersteds. Correlations were made between magnetic properties of these epitaxial films, the strain in the film and the interface roughness obtained from XTEM analysis.
Epitaxial Growth of fee Fe and Cu Films on Diamond
Authors: Pappas D.P. , Glesener J.W. , Harris V.G. , Krebs J.J. , Idzerda Y.U. , Morrish A.A. , Prinz G.A.
Published: September 2012

The growth of iron and copper films and multilayers on the (100) face of diamond has been achieved and studied by reflection high energy electron diffraction (RHEED), extended x-ray absorption fine structure (EXAFS), ferromagnetic resonance (FMR), and SQUID Magnetometry. RHEED and AES studies show that 2–3 atomic layers (AL) of Fe on C (100) forms a continuous film. The films as deposited at room temperature are disordered, and after a 350° C anneal displays a face-centered cubic structure. Subsequent layers of Cu on this epitaxial Fe film grow as an oriented, single crystal fee film. FMR and SQUID signals have been observed from the Fe films, showing that they are ferromagnetic.
Magnetic Ordering of Mn Overlayers on Fe (100)
Authors: Walker T. G. , Hopster H.
Published: September 2012

Spin polarized electron energy loss spectroscopy (SPEELS) was used to probe the magnetic state of mn over layers on Fe (100). Nonzero exchange asymmetries are measured and found to oscillate with a two monolayer period as the mn overlayer thickness is varied, proving that the surface layer of the mn overlayers has a net magnetic moment and that these (100) Magnetic layers are aligned antiferromagnetically. The average exchange splitting of the mn surface layer is found to be 2.9 eV, indicating that the mn surface has a magnetic moment of the order 3 μg. In addition, oxidized mn overlayer surfaces have been studied, and the spectral features in the range 0 to 6 eV energy loss can be assigned to 3d-3d transitions of Mn2+. No indication of magnetic ordering of the MnO overlayer has been oserved.
Structural and Magnetic Properties of e-Beam Prepared CoxPt1-x Alloy Films
Authors: Harzer J.V. , Hillebrands B. , Pogosova I.S. , Herrmann M. , Güntherodt G. , Weller D.
Published: September 2012

We have investigated structural and magnetic properties of CoPt alloy films with strong perpendicular magnetic anisotropy in the thickness range between 100Å and 400A. From a detailed x-ray analysis we find highly (111) -textured CoPt Microcrystal-lites in all samples. STM studies reveal a granular topography with grain diameters of up to 250Å. Measurements of hysteresis loops yield a saturation field which increases with thickness, and which is consistent with a freely mobile domain Model. Brillouin light scattering measurements of the frequencies of the surface and standing spin wave modes yield a bulk exchange constant, which is strongly dependent on the Pt content.
Magnetoresistance and Structure of Granular Co/Ag Thin Films
Authors: Stearns Mary Beth , Cheng Yuanda
Published: September 2012

Several series of CoxAg1-x granular thin films (-3000Å) were fabricated by coevapora-tion of Co and Ag in a dual e-beam UHV deposition system at varying substrate temperatures. These films have low field magnetoresistance values as large as 31% at room temperature and 65% at liquid N2 temperature. The structure of the films was determined using magnetization measurements as well as x-ray and various electron microscopy techniques. The composition was determined using Rutherford backscattering spectroscopy. The Magnetoresistance was measured at both room and liquid N2 temperatures.

We deduce from the magnetization and RBS Measurements that the films consist of Co globules embedded in a Ag Matrix and that there is no appreciable mixing of the Co and Ag atoms in the films deposited at substrate temperatures ≥ 400°K. The size of the Co globules is seen to increase with increasing Co concentration and the maximum magnetoresistance occurs in those films having the smallest Ag thickness which provides magnetic isolation of the Co globules.

We suggest that the large magnetoresistance of these films arises from the same mechanism which causes the low field magnetoresistance in pure ferromagnets, namely, the scattering of the highly polarized d conduction electrons of the Co at magnetic boundaries. The large increase in the room temperature magnetoresistance of the CO/Ag films as compared to those of pure 3d ferromagnetic films is due to the distance between the magnetic boundaries being reduced to a few nanometers, because of the small size of the single domain Co globules, as compared to a few microns in 3d ferromagnets.
Giánt Mr in Granular Systems Prepared by Melt-Spinning and Sputtering
Authors: Dieny B. , Teixeira S.R. , Rodmacq B. , Chamberod A. , Genin J.B. , Auffret S. , Gerard P. , Redon O. , Pierre J. , Ferrer R. , Barbara B.
Published: September 2012

Wc report the observation of giant magnctorcsistance in granular systems prepared by either Melt-spinning or sputtering. For Melt-spun CoxCu1-x alloys, with x varying between 5 and 30%, Magnctoresitancc amplitudes of 20% in 50 kOc at 5 K were obtained, similar to those reported for the same alloys prepared by sputtering. For sputtered (Ni80Fe20)xAg1-x alloys, three different contributions to the magnetorcsisiancc have been clearly identified: The spin-valve (or giant) Magnctorcsistance, scattering on magnetic fluctuations, and anisotropie Magnetorcsistancc. These three contributions have their own dependences on the size of the magnetic particles, on the degree of intermixing between NiFe and Ag, and on the temperature. In the third scries of samples, sputtered (Co70Fe30)xAg1-x, very large magnctorcsistance amplitude has been observed (AR/R as high as 20% at room temperature in 10 kOc and 60% at 10 K).
Giant Magnetoresistance in Granular Ni81Fe19/Ag Formed from Annealed Multilayers
Authors: Bian X. , Zaluska A. , Altounian Z. , Ström-Olsen J.O. , Huai Y. , Cochrane R.W.
Published: September 2012

We have observed giant Magnetoresistance (GMR) in Ni81Fe19/Ag granular structures synthesized by the annealing of artificial multilayers made by sputtering. The size and morphology of the magnetic precipitates can be controlled by adjusting the magnetic layer thickness in the initial stage. Magnetoresistance as large as 30% was found at 4.2 K with a rather small saturation field. Giant Magnetoresistance in this alloy system essentially depends on the magnetic precipitate size, annealing temperature and the Ni81Fe19 concentration. The temperature dependence of the magnetoresistance in these films is discussed.