bluuebunny/crossref_metadata_2025_split huggingface dataset:
Orientational Dependence of Oscillatory Exchange Coupling
Authors: Johnson M.T. , Bloemen P.J.H. , Coehoorn R. , de Vries J.J. , McGee N.W.E. , Jungblut W. R. , Reinders A. , aan de Stegge J. 
Published: September 2012

ABSTRACTThe role of the interlayer Fermi surface in driving oscillatory exchange coupling of ferromagnetic layers has been critically tested in a series of MBE-grown coherent epitaxial sandwiches prepared on single-crystal substrates. The wedge-shaped Cu (or Cu-based) interlayers have been modified in a number of different ways, achieving orientational, compositional and structural alteration of the Cu Fermi surface. Observed phenomena include multiperiodic coupling oscillations in both the ferromagnetically and antiferromagnetically coupled regions of (lOO) -oriented Co/Cu/Co samples, extended oscillatory periods across CuNi alloy interlayers, and extremely short-period oscillations in a bcc (100) Fe/Cu/Fe system. These phenomena are straightforwardly explained in terms of calculated Fermi surface variations.
Phonon Spectra Dependence on Growth and Sample Treatment in β-FeSi2
Authors: Guizzetti G. , Marabelli F. , Patrini M. , Mo Y. , Onda N. , Von KÄnel H. 
Published: September 2012

ABSTRACTTransmittance, reflectance and Raman measurements have been performed from 50 to 700 cm−1 on different thin films of β-FeSi2 epitaxially grown by MBE on Si substrates. Vibrational spectra show much more structures than the five phonons usually observed in this material; the dependence on the crystalline orientation, the thickness, the growth and the annealing temperature has been studied.
Fe-Silicides Formed with Molecular Beam Epitaxy and Studied with Conversion Electron Mössbauer Spectroscopy
Authors: Degroote S. , Langelaar M.H. , Kobayashi T. , Dekoster J. , Wachter J. De , Moons R. , Niesen L. , Langouche G. 
Published: September 2012

ABSTRACTFe-sulicides were formed by annealing MBE-deposited thin 57Fe layers with thicknesses between 20 Å and 60 Å on (7x7) reconstructed Si(111) substrates. During the growth the substrate was held at room temperature. The silicide formation upon annealing in the temperature range of 200°C to 900°C was studied in-situ with RH-EED. Samples were studied with in-situ CEMS (Conversion Electron Mossbauer Spectroscopy) as well as with ex-situ CEMS after covering with Ag to prevent oxidation. RBS/Channeling was used to study the epitaxial quality and the structure of these layers.Using the 57Fe nuclear probe, it is shown that silicide formation occurs at the interface already at room temperature. Metastable silicides with cubic structure are observed in the low temperature annealing range, and characterized by their Mossbauer parameters. At higher temperatures stable ε-FeSi and β-FeSi2 are formed.
New Resistive Materials Based on Iron Disilicide Alloys
Authors: Engalychev A.E. , Fedorov M.I. , Kaliazin A.E. , Alekseeva G.T. , Ioffe A.F. 
Published: September 2012

ABSTRACTThe electrical conductivity of a number of the semiconducting alloys of iron disilicide with the iron group transition metals and some elements of Vb group have been investigated in detail. Wide temperature regions of linear temperature dependence of resistance were found. The temperature coefficient of resistance (TCR) in these regions is low enough. There is an opportunity of varying the resistivity of these alloys by means of modification of the alloy composition.
Effects of annealing and cobalt implantation on the optical properties of βFeSi2
Authors: Finney M S , Yang Z , Harry M A , Reeson K J , Homewood K P , Gwilliam R M , Sealy B J 
Published: September 2012

ABSTRACTIn this paper optical absorption and photoluminescence (PL) techniques are used to study the optical properties of βFeSi2 layers fabricated by Ion Beam Synthesis (IBS). The way in which the band-gap varies when a small dose of Co is added before Fe implantation is also investigated. Our results indicate that the band-gap for βFeSi2 is direct with a value of 0.87eV. When a sufficiently high dose (1 ×10 16cm2) of Co is implanted prior to Fe we see the appearance of an additional band-gap after annealing at 1173K which we attribute to the formation of a ternary CoxFeySiz phase. We also show that by placing the sample in a hydrogen plasma it is possible to raise the temperature at which PL occurs in βFeSi2 to σ 200K.
Evolution of Defect and Impurity Profile During High Dose Co Implantation into Si at Elevated Temperatures
Authors: Schippel S. , Witzmann A. 
Published: September 2012

ABSTRACT<111> -Si was implanted with 250 keV Co ions at a target temperature of 350°C. The ion dose was varied between 1 × 1014 cm−2 and 2 × 1017 cm−2. The evolution of the defect and impurity profile was investigated by Rutherford Backscattering Spectrometry (RBS), channeling and transmission electron microscopy (TEM).Up to a dose of 1 × 1015 Co cm−2 no defects can be detected. At higher Co doses, we find correlated defects in the center of the Co distribution and point defects in the region below. Moreover, damage accumulation at the surface is observed. The concentration of defects increases with increasing ion dose and reaches its level of saturation at a dose of 2 × 1016 cm−2.The Co profiles of samples implanted at 350°C differ considerably from the Gaussian shape. The near surface and the back flank are parts of Gaussian distributions. However, the standard deviation of the near surface flank is always smaller than that of the back flank. Moreover, the distributions show tails into the substrate at depths > 320 nm. This proves that radiation damage acts as an effective center for the nucleation of CoSi2.During annealing we find a redistribution of Co towards the defective regions for Co doses between 1 × 1016 cm−2 and 5 × 1016 cm−2.
Crystallographic Structure of Mesotaxial IrSi3 in Six
Authors: Hinneberg H.-J. , Sjoreen T. P. , Chisholm M. F. 
Published: September 2012

ABSTRACTA buried epitaxial IrSi3 layer has been produced in (111) oriented Si by high dose Ir+- implantation (1 MeV, 1.7× 1017 Ir+/cm2, 550°C) and subsequent annealing (5 h at 1100°C). Transmission electron microscopy and ion channeling show that the hexagonal IrSi3 prefers to form with its (2110) plane oriented parallel to Si(111). while its [0001] direction is parallel to either [112], [121], or [211]. Thus, the IrSi3 film is made up of three differently oriented crystals, each occupying about 1/3 of the silicide volume.A dose of 3.5× 1016 1r+/cm2 leads to the formation of a band of large, isolated precipitates. They have the same epitaxial relationship to Si, but the Si(111) plane is no longer the only one to which the (2110) of IrSi3 is parallel. Instead precipitates are also observed oriented parallel to (111), (111), and (111) in Si in roughly equal numbers. Consequently, there are now 12 possible orientations of lrSi3 crystals. We assume that strain relief and interface area minimization are the main factors suppressing the additional orientations in the continuous lrSi3 films formed by the coalescence of precipitates at higher doses.
Metal Vapour Vacuum Arc Ion Source to Synthesize Refractory Metal Silicides
Authors: Liu B.X. , Zhu D.H. , Lu H.B. , Tao K. 
Published: September 2012

ABSTRACTMetal Vapour Vacuum Arc (MEVVA) Ion Source was employed, for the first time, to synthesize metal silicides. Refractory metal silicides NbSi2, TaSi2, WSi2 and MoSi2; were successfully formed by implanting respective metal ions into Si(111) wafers. It was found that the high current density metal ion implantation not only provided the metal components but also caused a simultaneous annealing for various metal-silicide phases to grow. When the imp ytation was conducted at 40 kV, the Nb ion current density was up to 76 μA/cm at a dose of 4×1011/cm2, and the Ta, W and Mo ion current densities were up to 65 μA/cm2 at a dose of 5×1017 ions/cm2, hexagonal NbSi2, TaSi2, MoSi2 and WSi2 were formed. Post annealing transformed the WSi2 and MoSi2 phases from hexagonal to tetragonal structure, featuring lower resistance than that of the as-implanted ones.
The Influence of Implantation-Induced Non-Stoichionetry on the Epitaxial Recrystallization of CoSi2
Authors: Ridgway M.C. , Vantomme A. , Bavel A.-M. Van , Langouche G. 
Published: September 2012

ABSTRACTEpitaxial CoSi2 layers on Si substrates have been amorphized with Co and/or Si ion implantation. The influence of nonstoichiometry on the rate of solid-phase epitaxial growth (SPEG) of amorphized CoSi2 has been investigated with time-resolved reflectivity, Rutherford backscattering spectrometry and Mossbauer spectrometry, the latter with radioactive 57Co probes. A decrease in SPEG rate was apparent with an increase in nonstoichiometry. For a given ion dose, the decrease was greater following Co implantation. The means by which non-stoichiometry is accommodated in a crystalline CoSi2 lattice - either through phase separation or defect formation - has been considered. SPEG rate retardation was also evident in samples implanted with both Si and Co ions with a Si:Co dose ratio of 2:1. Additional mechanisms may thus also contribute to the observed SPEG rate reduction.
Electron Microscopy Evidence of Interfacial Steps Controlling the Kinetics of NiSi2 Formation
Authors: Hesse D. , Werner P. , Heydenreich J. , Mattheis R. 
Published: September 2012

ABSTRACTThe kinetics and phase formation sequence of thin-film solid-state reactions, including silicide forming reactions, have frequently been considered to be controlled by interfacial kinetic reaction barriers. These are purely phenomenological quantities which describe the finite rate of the interfacial reaction in terms of limited particle fluxes crossing the respective interfaces. No atomic mechanisms that might be responsible for the action of such barriers have so far been indicated, with the exception of Schmalzried's formulation. The latter says that the interfacial barrier is due to the limited relaxation time needed by the particles to rearrange into the proper sublattice after having crossed the interface. We present correlated kinetic and structural observations during the 2Ni + Si → NiSi2 reaction on the Si(111) surface and discuss them with the help of a model involving the formation and lateral propagation of interfacial steps of different height. The model allows us to explain the kinetic observations by reaction barriers formed as a result of the crystallographic boundary conditions of the reaction.
Characterization of Epitaxial CoSi2 Film Growth on Si(100) by Slow Positron Beam
Authors: Liu Ping , Lin Chenglu , Zhou Zuyao , Weng Huiming , Li Bingzong , Han Rongdian , Zou Shichang 
Published: September 2012

ABSTRACTA slow positron beam was used to investigate the solid state reaction of Co/Si and Co/Ti/Si. Variable-energy (0-20 keV) positrons were implanted into samples at different depths. The Doppler broadening of the annihilation -y-ray energy spectra, measured at a number of different incident positron energies were characterized a line-shape parameter “5”. It was found that the measured S parameters were sensitive to thin film reaction and crystalline characteristics. In particular, the S parameter of epitaxial CoSi2 formed by the ternary reaction was quit different from that of the polycrystalline CoSi2 formed by direct reaction of Co with Si.
Atomistic Aspects of Silicide Reactions Studied with STM
Authors: Bennett P. A. , Parikh S. A. , Lee M. Y. , Cahill David G. , Copel M. , Tromp R. M. 
Published: September 2012

ABSTRACTWe discuss atomistic aspects of the silicide contact reaction inferred primarily from STM observations of the prototype system Co/Si(1 11). For room temperature deposition and low coverage (0.01M1) we find that metal atoms exist as near-surface interstitials within the 7×7 reconstruction. Bond breaking associated with silicide formation occurs only at higher coverages. Deposition at 320C results in flat-topped triangular islands of epitaxial CoSi2 with a metastable 7-fold (111) interface, stabilized by the lateral silicon-silicide interface along the island edges. Some islands are covered with a 2×2 array of silicon adatoms. Very high temperature annealing (1200C) results in an “impurity stabilized 1×1” surface which is in fact a lattice gas of ring-clusters that appear like tiny donuts or bagels in empty states STM images. These structures phase-separate from the clean 7×7 structure upon cooling below 850C.
Nondestructive Study of Metal-Silicon Interfaces Using Soft X-Ray Emission Spectroscopy
Authors: Watabe H. , Iwami M. , Hirai M. , Kusaka M. , Nakamura H. , Miyashita H. 
Published: September 2012

ABSTRACTSi L2,3 valence band soft x-ray emission spectrum (SXES) due to an e ectron excitation for silicides shows a clear modification from that for Si single crystal. Using this fact in combination with the incident angle variation(IAV) device, a non-destructive in-depth analysis of a Au(thin film)-Si(lll) contact is successfully carried out. Also, the SXES method has clarified the fact that a fair amount of the Si-s valence band density of state (yB-DOS) is included in the upper part of the yB-DOS for a Au-Si alloy, or Au-silicide, due to the Au-Si bond formation, which is a clear contrast to proposals given so far.
Interfacial Structures of Nickel Silicides in the SiaNi/Sic System
Authors: Tseng Bae-Heng , Hsieh Chia-Dar , Wu Show-Gin 
Published: September 2012

ABSTRACTA laterally uniform formation of NiSi2 at low temperature had been reported for the SiaNi/Sic system. In this work, the interfacial structure of NiSi2 is studied by the high-resolution electron microscopy. We observe an amorphous layer (5–10 nm in thickness) between Sic and NiSi2 in a Sia(300nm)/Ni(5Onm)/Sic sample after annealing at 450°C. The NiSi2 phase in this sample has a polycrystalline structure. We also find that a contaminated amorphous-Si film can not promote a reaction with Ni. A SIMS depth profile shows that this amorphous-Si layer is high in oxygen and carbon. In this case, the silicide formation is similar to the Ni/Sic system.
Electrical Transport Properties of Cu3Ge Thin Films
Authors: Aboelfotoh M. O. 
Published: September 2012

ABSTRACTWe present results of electrical transport studies performed on thin films of ε1-Cu3Ge in the temperature range 4.2 – 300 K. It is found that ε1-Cu3Ge which has a long-range ordered monoclinic crystal structure, exhibits a remarkably low metallic resistivity of σ 6 μΩ cm at room temperature. The density of charge carriers, which are predominantly holes, is σ 8 × 1022/cm3 and is independent of temperature and film thickness. The Hall mobility at 4.2 K is σ 132 cm2/V s, considerably higher than in pure copper. The elastic mean free path is found to be σ 1200Å, which is surprisingly large for a metallic compound film. The results show that the residual resistivity is dominated by surface scattering rather than grain-boundary scattering. It is also found that by varying the Ge concentration from 0 to 40 at. % the resistivity exhibits anomalous behavior. This behavior is correlated with changes observed in the crystal structure of the thin-film alloys as the Ge concentration is increased. The resistivity remains close to that of the ε1-Cu3Ge phase over a range of Ge concentration which extends from 25 to 35 at. %
Schottky Barrier Heights of PT Silicides on SiGe
Authors: Jimenez J.R. , Xiao X. , Sturm J.C. , Pellegrini P.W. , Chi M. 
Published: September 2012

ABSTRACTSilicide/SiGe Schottky barriers are of importance for applications in infrared detectors and SiGe contacts, as well as for fundamental studies of metal-semiconductor interfaces. We have fabricated silicide/SiGe Schottky diodes by the reaction of evaporated Pt and Ir films on p-SiGe alloys with a thin Si capping layer. The onset of metal-SiGe reactions was controlled by the deposited metal thickness. The Schottky barrier heights were determined from internal photoemission. Pt-SiGe and Ir-SiGe reacted diodes have barrier heights that are higher than the corresponding silicide/p-Si diodes. PtSi/Si/SiGe diodes, on the other hand, have lower “barrier heights” that decrease with increasing Ge concentration. The smaller barrier heights in such silicide/Si/SiGe diodes are due to tunneling through the unconsumed Si layer. Equations are derived accounting for this tunneling contribution, and lead to an extracted “barrier height” that is the Si barrier height reduced by the Si/SiGe band offset. Highly bias-tunable barrier heights are obtained (e.g. 0.30 eV to 0.12 eV) by allowing the SiGe/Si band offset to extend higher in energy than the Schottky barrier, leading to a cut-off-wavelength-tunable silicide/SiGe/Si Schottky diode infrared detector.
Applications of CoSi2 to VLSI and ULSI
Authors: Murarka S. P. 
Published: September 2012

ABSTRACTSilicides have found application as high conductivity, high temperature, and corrosion resistance materials that form good electrical contacts to silicon and good low resistivity cladding on polysilicon films used as gate metal. Of various silicides investigated in past CoSi2 offers several advantages including lowest resistivity, self-aligned formation, low lattice mismatch with silicon, stability in presence of dopants and on SiO2, Si3N4, or Sioxynitrides, and reliability to process temperatures ≤900°C even when used in thicknesses as thin as 50-60 nm. Thus, CoSi2 has found an application in VLSI and ULSI. In this paper, the properties, formation and processing, reliability, and applicability of CoSi2 will be reviewed. It will be shown that CoSi2 is only silicide that offers properties and reliability for continued use in sub-0.25 pm VLSI and ULSI integrated circuits.
Titanium Germanosilicide: Phase Formation, Segregation, and Morphology
Authors: Aldrich D.B. , Chen Y.L. , Sayers D.E. , Nemanich R.J. 
Published: September 2012

ABSTRACTThe high temperature solid phase reaction of Ti with SixGe1−x produces a low resistivity titanium germanosilicide which is isomorphic with the C54 phase of TiSi2 and TiGe2. The composition of the final C54 Ti(SiyGe1−y)2 film is dependent on the composition of the initial Si-Ge alloy and on the annealing conditions. The intermediate phases of the Ti-Si and Ti-Ge reactions are C49 TiSi2 and Ti6Ge5 respectively. The reaction path of Ti - SixGe1−x shifts from that of Ti-Si to that of Ti-Ge as the SixGe1−x alloy composition changes (×=1→0). Phase separations were observed at low temperatures for Ti reactions with Si-Ge alloys and the C54 formation temperature was observed to decrease as the Si-Ge alloy composition approached Si.5Ge.5. Surface and interface morphologies were examined using SEM and TEM. The formation of smooth, large grain, low resistivity films has been observed for the reaction of Ti with low Ge content alloys (x≥0.7). As germanium content is increased the formation of faceted islands is observed. Reactions with high Ge content alloys (x≤0.3) produce films with morphologies similar to those of the Ti-Ge reaction.
Nonalloyed Ohmic Contacts to N-Si Using a Strained Si0.5Ge0.5 Buffer Layer
Authors: Liou Hsing-Kuen , Yang Edward S. , Tu K. N. 
Published: September 2012

ABSTRACTNonalloyed shallow ohmic contacts to n-Si have been fabricated by using an 80 Å thick strained Si0.5Ge0.5 buffer layer grown by molecular beam epitaxy. X-ray photoelectron spectroscopy was employed to investigate the Si 2p and Ge 3d core level binding energies of the strained and the relaxed Si0.5Ge0.5 and to determine their relative Fermi level positions. It was found that the surfaces of strained Si0.5Ge0.5 exhibit pinning very close to the conduction band. Rutherford backscattering and Auger depth profiling were employed to determine the contact reactions using Ti, W or Pt as contact metals. In the case of Pt, a 500 Å W diffusion barrier can protect the ohmic behavior up to 550 °C for 30 min. The specific contact resistance of the Pt/W/Si0.5Ge0.5/n-Si contact extracted from the D-type cross-bridge Kelvin resistor was 3.5x10-5 Ω·cm2.
The Fabrication of Self-Aligned Ohmic Cobalt Contacts to Relaxed, N-Type Si0.7Ge0.3
Authors: Watson G. Patrick , Monroe Don , Cheng J-Y , Fitzgerald Eugene A. , Xie Ya-Hong , Vandover R. Bruce 
Published: September 2012

ABSTRACTCo(SiGe)x contacts have been formed on low defect density, relaxed Si0.7Ge0.3 layers by conventional self-aligned contact processing techniques. Test structures measuring the contact metal sheet resistance indicate that the resistivity is high for anneal temperatures from 450°C to 750°C. The lowest sheet resistivity was 100 Ω/□, about 10 times the resistivity of a comparable amount of CoSi2. Contact resistivities, measured by the transmission line method, were as low as 2 × 10−5 Ω cm2. There is a large discrepancy between contact resistivities measured by transmission line and 4 point Kelvin test structures that may be due to the fabricated contact sizes.
Raman Scattering Study of Interface Reactions of Co/SiGe
Authors: Ying Hong , Wang Zhihai , Aldrich D. B. , Sayers D. E. , Nemanich R. J. 
Published: September 2012

ABSTRACTRaman scattering measurements are used to characterize Co/Si, Co/Ge and CO/Si0.8Ge0.2 thin film reactions. For Co/Si samples, the phase transitions Co--CoSi--CoSi2 are identified by Raman spectroscopy. For Co/Ge samples, Raman features associated with Co5Ge 7 and CoGe2 phases were observed. For CO/Si0.8Ge0.2 samples, only CoSi was identified along with Ge enriched SiGe alloy peaks. No features associated with CoGe or Co(SiGe) were found.
Solid State Amorphization in Silicide—Forming Systems
Authors: Chen L.J. , Hsieh W.Y. , Lin J.H. , Lee T.L. , Chen J.F. , Liang J.M. , Wang M.H. 
Published: September 2012

ABSTRACTSolid phase amorphization has been found to occur in all refractory metal and a number of rare—earth and platinum group metal thin film on silicon systems. For Ti/Si, Zr/Si, Hf/Si, V/Si, Nb/Si and Ta/Si systems, the growth of amorphous interlayer (a—interlayer) was found to follow a linear law in the initial stage. Si atom was found to be the dominant diffusing species in the solid phase amorphization in Ti/Si, Zr/Si and Hf/Si systems. For the Y/Si system, the stability of amorphous interlayer depends critically on the composition of the amorphous films.Auto–correlation function analysis was utilized to determine the structure of the amorphous interlayers. HRTEM in conjunction with the fast Fourier transform were applied to determine the first nucleated crystalline phase. Simultaneous presence of multiphases was observed to occur in a number of refractory metal/Si systems. Interesting electrical properties of amorphous interlayers were found for Ti/Si, Zr/Si and Hf/Si systems.
Silicides for Highly Integrated Memory and Logic Circuits
Authors: Winnerl Josef 
Published: September 2012

ABSTRACTState of the art DRAM and logic processes widely make use of silicides formed by refractory metals like Ta, Mo, W, Ti, Co, or others. The methods for silicide formation range from sputtering, reaction with predeposited metal, to selective CVD deposition.The most common application of silicides in state of the art CMOS processes is to use them as a conducting layer that can withstand high temperature processes and that has a significantly lower sheet resistivity than doped mono or poly crystalline silicon. Besides their role as a temperature stable conductor silicides have further interesting properties when using them as a diffusion source for impurities to generate shallow junctions, or as an alternative gate material with a work function in the middle of the silicon band gap.Based on the example of the self aligned silicidation with titanium silicide the limitations of the state of the art technology will be shown and requirements for future applications will be discussed.