bluuebunny/crossref_metadata_2025 huggingface dataset:
Heteroepitaxial CxSil−X/Si(100) Metastable Alloys
Authors: Posthill J.B. , Rudder R.A. , Hattangady S.V. , Fountain G.G. , Humphreys T.P. , Nemanich R.J. , Parikh N.R. , Markunas R.J.
Published: March 2011

Metastable CxSi1−epitaxial films have been grown on Si(100) by remote plasmaenhanced chemical vapor deposition. Carbon concentrations of ∼ 3 atomic percent have been achieved at a growth temperature of 725 °C. No evidence for the formation or precipitation of SiC was found using x-ray diffraction, Raman scattering spectroscopy, IR. reflectance, or transmission electron microscopy. IR reflectance data gives a preliminary indication that the carbon has been incorporated onto substitutional sites in the Si lattice.
Growth of Epitaxial Layers of GexSi1−x BY UHV/CVD
Authors: Racanelli Marco , Greve David W.
Published: March 2011

Undoped epitaxial layers of GexSi1−x have been grown on (100) silicon substrates using the UHV/CVD technique. Epitaxial films were obtained at growth temperatures between 577 and 665 C. The growth rate and germanium content of the layers has been determined as a function of the germane flow and the deposition temperature. A bake at 800 C was found to be highly beneficial in reducing the defect density and improving the film roughness.
Heteroepitaxy and Characterisation Of Ge-Rich SiGe Alloys on GaAs
Authors: Venkatasubramanian R. , Timmons M.L. , Mantini M. , Kao C.T. , Parikh N.I.
Published: March 2011

Growth of SiGe alloys on GaAs substrates at temperatures as low as 590 °C is described. The growth has been accomplished using the pyrolysis of disilane (Si2H6) and Germane (GeH4) at such temperatures. The layers were characterized electrically and show n-type conduction with a carrier concentration of ~ 1 × 1018 cm−3. The high quality of the SiGe layers are evident in the Rutherford backscattering (RBS) channeling results on SiGe/GaAs structures. A Xmin of 5.6% has been obtained for a Si0.05Ge0 95 layer on GaAs. Xmin increases with increasing silicon content in the SiGe layers. The SiGe alloy layers were studied by x-ray diffraction, and the composition was determined assuming coherent, but tetragonally-distorted growth of SiGe on GaAs. The distortion calculations, based on theoretical elastic-constants, were confirmed using Auger electron spectroscopy to check alloy composition.
Meso-Epitaxy: Epitaxial Growth Of Silicon Over Buried Single Crystal Cosi2 Layers.
Authors: Osenbach J. W. , White A. E. , Short K. T. , Praefcke H. C. , Kannon V. C.
Published: March 2011

Buried single-crystal layers of CoSi2 were formed in 150Ω-cm, p-type (100) silicon by high dose implantation of Co followed by furnace annealing. Subsequently, epitaxial silicon layers were grown over these buried CoSi2 layers using SiCl2H2 /HCI/H2. The RBS channel yield of the buried CoSi2 and the epitaxial Si layer is less than 4% indicating good crystallinity of the layer. The defect density in the epitaxial silicon layer as revealed by a dilute Schimmel etch, was in excess of 108 dislocations/cm2 which appear to originate from <111> CoSi2 facets. However, both the substrate/CoSi2 and the CoSi2/epi interface are single crystal as revealed by lattice fringes in TEM. To our knowledge, this is the first report of such a structure.
Formation of High Quality Si1−xGex/Si Heterostructures by Selective-Area Mbe Growth
Authors: Murakami Eiichi , Nishida Akio , Etoh Hiroyuki , Nakagawa Kiyokazu , Miyao Masanobu
Published: March 2011

Selective-area MBE growth of Si1−xGex film is examined using a Si substrate partially covered with SiO2 film. Elimination of misfit dislocations is observed by TEM. Two possible mechanisms in this elimination, limitation of the lateral extension of misfit dislocations, and partial relaxation of the strain at the SiO2 pattern edge, are discussed.
Columnar Epitaxy of Hexagonal and Orthorhombic Silicides on Si(111)
Authors: Fathauer R.W. , Nieh C.W. , Xiao Q.F. , Hashimoto Shin
Published: March 2011

Columnar grains of PtSi and CrSi2 surrounded by high-quality epitaxial silicon are obtained by ultra-high vacuum codeposition of Si and metal in an approximately 10:1 ratio on Si(111) substrates heated to 610-840°C. This result is similar to that found previously for CoSi2 (a nearly-lattice-matched cubic-fluorite crystal) on Si(111), in spite of the respective orthorhombic and hexagonal structures of PtSi and CrSi2. The PtSi grains are epitaxial and have one of three variants of the relation defined by PtSi(010)//Si(111), with PtSi[001]//Si<110>.
Structural Characterization of Ultrathin Epitaxial ErSi2−x on Si(111)
Authors: Kaatz F.H. , Spiegel J. Van der , Graham W.R.
Published: March 2011

The epitaxial structure of ErSi2−x on Si(1 11) has been investigated using Rutherford backscattering (RBS) and transmission electron microscopy (TEM). Films 10 nm. thick show channeling minimum yields of 4% after room temperature deposition and annealing to 800°C. Plan view electron microscopy on ultrathin layers 0.5 nm. to 10 nm. thick reveals the formation of a complex microstructure involving vacancy ordering in these films. This superlattice structure is interpreted by considering domain formation and twinning in the heteroepitaxial ErSi2−x.
Surface Phase Separation and Ordering in Compound Semiconductor Alloys
Authors: Mcdevitt T.L. , Mahajan S. , Laughlin D.E. , Bonner W.A. , Keramidas V.G.
Published: March 2011

The orientation dependence of phase separation has been examined in detail in InGaAsP layers grown by liquid phase epitaxy on (001), (110), (111)In and (123) InP substrates. It is shown that phase separation is two-dimensional in nature and does not occur along the growth direction for the cases examined. Further, phase separation takes place along the soft directions lying in the growth plane. These results very strongly suggest that phase separation evolves at the surface while the layer is growing.

CuPt-type ordering characteristics of InGaAsP layers are presented. In addition, the Influence of growth temperature and growth rate on domain sizes have been investigated in GaInP2 layers. A model has been proposed to rationalize the formation of domains and involves steps present on the surface. Results suggest that ordering like phase separation occurs at the surface while the layers is being deposited. It is inferred that the two microstructural features evolve concomitantly at the surface during layer growth.
Optical Investigations of Symmetry Breaking in GaInP2
Authors: Mascarenhas A. , Kurtz Sarah , Kibbler A. , Olsonsolar J.M.
Published: March 2011

We present experimental evidence for the spontaneous breaking of cubic symmetry in the band structure of films of Ga0 52 1n0 48P grown by organomeltallic vapor phase epitaxy on (100) GaAs substrates. We show how this effect is related to the spontaneous ordering of the alloy, and its correlation with the anomalous lowering of the band-gap observed in these films.
An Advanced Mechanical Dimpung Technique for the Preparation of TEM Specimens
Authors: Fischione Paul E. , Howe James M.
Published: March 2011

For materials that are conducive to pre-thinning by mechanical techniques, a combination of dimpling and ion milling is commonly employed to produce TEM specimens. In order to minimize artifacts induced by ion milling and to provide an increased electron-beam transparent area, new instrumentation for mechanical thinning has been developed. Examples illustrating the utilization of this instrument in the preparation of cross-sectional interfaces from layered samples are discussed.
A Streamlined Technique for Preparation of Transverse Specimens for Transmission Electron Microscopy
Authors: Shaapur F. , Park M.
Published: March 2011

A procedure for batch processing of up to four specimens for cross-sectional transmission electron microscopy (X-TEM) has been developed. The technique is essentially an extension of the standard multi-slice composite full disc sample preparation method. However, disc cutting and dimple grinding steps have been eliminated. The trimming, gluing, stacking, and sectioning of the wafers from the original sample material to produce composite transverse sections are identical to those of the standard scheme. Grinding and polishing of the sections are carried out in a batch mode which, in turn, reduces the overall processing time per specimen. The prepared composite foils are mounted on metallic disc grids which provide structural support during ion thinning and microscopy.
A Procedure for Cross Sectioning Specific Semiconductor Devices for Both SEM and TEM Analysis
Authors: Benedict J. P. , Anderson Ron , Klepeis S. J. , Chaker M.
Published: March 2011

The procedures described in this paper allow both SEM and TEM analysis to be performed on the same, device specific, semiconductor cross section. In order to accomplish this, a number of tools and fixtures have been constructed that allow the user to polish into the sample to a predetermined plane-of-polish, bisecting the device or feature of interest for SEM analysis. After SEM examination, the specimen is prepared for TEM analysis by first affixing a grid to the just-examined surface, inverting the specimen and parallel-polishing the backside of the specimen until the specimen's total thickness is in the 0.5 to 1.0μm range using the described tools. A subsequent one to ten minute ion milling step cleans the specimen. A very considerable positive side-effectof this method is the nearelimination of artifacts arisingfrom the use of strong chemicals and lengthy ion milling. The method has been extended to the preparation of plan-view device samples and non-semiconductor specimens.
Preparation of TEM Sections using Natural Lithography
Authors: Deckman H. W. , Dunsmuir J. H.
Published: March 2011

We have developed and used a simple lithographic technique that allows preparation of TEM sections from a variety of materials in 10–45 minutes. To obtain TEM sections, 50–5,000 Å diameter cylindrical post structures are microfabricated on the surface of the sample using colloidal particles as an etch mask. The technique simultaneously prepares 104 – 108 posts. This not only allows a statistical characterization of sample structure but also provides enough material for studies of the electronic, spectroscopic and chemical properties of edge sites exposed on the post surfaces. These lithographically prepared posts have been used to study the structure of materials as diverse as a layered transition metal chalcogenide catalysts, semi-insulating polysilicon, amorphous semiconductor superlattices, crystalline metallic and semiconductor superlattices, and molecular-scale microporous superlattices.
Preparation of a Prespecified Interfacial Region by Cross Section Sampling for HREM Investigations
Authors: Paul-Henri Albarede
Published: March 2011

Thin polysilicon layers are used in microelectronics as a first metal level. With careful annealing, a doped polysilicon layer can also act as a diffusion source for the underlying Si substrate. For such a case, the quality of the polysilicon to substrate Si interface plays an important role in the electrical and migratory properties of the final structure. Therefore, the interface must be observed very closely.

Arsenic doped polysilicon was deposited on a <001> oriented Si wafer. Cross-section TEM specimen preparation was performed by first cutting dices centered on the prespecified region of interest. The dices are bounded face to face, and then a parallel double face mechanical polishing of the section reduces the thickness of the cross-section to about 30 microns. An ion milling operation is used to finish the preparation. Localisation precision by this method is not better than 100 microns, but this can be improved to 10 microns by replacing one of the dices with a piece of glass to allow visualization of the surface during polishing.

The advantage of this method is that a large region can be observed, 1.5 mm long on each piece, with rather good localisation.

An application is the HREM imaging of a typical interfacial region. We could see an ultrathin (1nm) amorphous layer running along the interface between the Si and the polysilicon. Physical characterization (EDXS, EELS) was obtainable from this ultrathin layer.
Magnetic Recording Disk Specimen Preparation for Transmission Electron Microscopy
Authors: Parker Michael A. , Parker K. L. , Meininger M. , Bermea A.
Published: March 2011

Modifications to conventional techniques required to prepare specimens from magnetic recording disks are described. Both the preparation of through-foil and cross-section specimens are discussed. The differences between preparation techniques for particulate and thin film disks are elucidated. Micrographs of specimens prepared by various techniques from both types of disk technology are presented that show the relative merits of these methods.
Diffuse X-Ray Scattering for the Study of Defects in Silicon
Authors: Larson BC , Barhorst JF
Published: March 2011

X-ray diffuse scattering can be used to study the size, concentration, and nature of lattice defects and defect clusters in crystalline materials. The availability of analytical models and detailed numerical calculations for the “Huang” diffuse scattering close to Bragg reflections and the “asymptotic” diffuse scattering at somewhat larger distances from Bragg reflections has made it possible to carry out detailed analyses of the intensity and angular distribution of the diffuse scattering in terms of specific defect parameters. Accordingly, diffuse scattering has been used to study point defects, dislocation loops, and precipitates in metals, semiconductors, and insulators and has provided information on defect geometries, size distributions, and concentrations. In this paper, the theoretical framework necessary for the interpretation of the “Huang” and “asymptotic” diffuse scattering from defect clusters is presented and examples of diffuse scattering calculations for defects in silicon are given. Diffuse scattering from clustered defects in silicon is discussed in terms of the type of information available from this scattering and the relative merits of diffuse scattering as an investigative tool for defect clusters. Diffuse scattering analysis techniques for the determination of separate size distributions for vacancy and interstitial dislocation loops in silicon are presented and applied to diffuse scattering measurements on neutron irradiated silicon. Dislocation loop densities and sizes determined in the as-irradiated state and after thermal anneals are compared with electron microscopy results.
A Tentative Identification of the Nature of {113} Stacking Faults in Si – Model and Experiment
Authors: Tan T.Y. , Foell H. , Mader S. , Krakow W.
Published: March 2011

An atomic model with fully bonded interstitial atoms is proposed for the {113} stacking faults (SF). It is shown that the development of the {113} habit plane is a result of minimizing bond length changes. The fault may be represented by a partial dislocation and a partial will facilitate an unfaulting reaction to result in a edge dislocation. Lattice images were obtained for a {113} SF which showed that the model is essentially correct.
Formation and Effects of Secondary Defects in Ion implanted Silicon
Authors: Washburn Jack
Published: March 2011

The clustering of isolated interstitial silicon, implanted atoms, and vacant lattice sites produced by low temperature and room temperature ion implantation during subsequent annealing is reviewed. An electron microscope method for studying the kinetics of the amorphous to crystalline transformation in silicon is described. The technique is applied to measurement of the activation energy for interface migration and the formation of microtwins for different growth directions. A very brief review of the effects of laser annealing after ion implantation is included.
A Review of Ntd-Induced Defects in Silicon
Authors: Meese J. M.
Published: March 2011

Neutron transmutation doping (NTD) has become the preferred method of phosphorus doping of float zone silicon for the Si power device industry. This doping process is accomplished by thermal neutron irradiation in a nuclear reactor. One of the stable isotopes, 30Si, is transmuted to the desired dopant, 31p, by thermal neutron capture and beta decay. This transmuted product becomes electrically active only after suitable annealing of the accompanying radiation damage which is the result of a number of different displacement mechanisms. This paper will present a review of our present understanding of the production and annealing of these displacement defects.
Dislocation Defect States in Deformed Silicon
Authors: Patel J. R. , Kimerling L. C.
Published: March 2011

Transient junction capacitance measurements on deformed silicon reveal a variety of states after deformation. Upon annealing or following more homogeneous deformation the defect spectrum shows a single broad feature. A state at E(0.38) has been tentatively assigned to defect sites along the dislocation. A broad band of states at H(0.35) is postulated to represent states due to the reconstructed dislocation core.
Swirl Defects in As-Grown Silicon Crystals
Authors: de Kock A.J.R.
Published: March 2011

During melt-growth of macroscopically dislocation free bulk silicon crystals (floating-zone and Czochralski technique) microdefects can form due to the condensation of thermal point defects (self-interstitials, vacancies). The formation of these imperfections, generally referred to as “swirl defects”, is strongly affected by the growth conditions (e.g. the crystal pulling rate) and crystal purity. The various reported defect formation models will be discussed. Special attention will be paid to the effect of doping on swirl defect formation.
Oxygen, Oxidation Stacking Faults, and Related Phenomena in Silicon
Authors: Hu S. M.
Published: March 2011

Some salient features of the phenomena of oxidation stacking faults (OSF) and oxidation enhanced diffusion(OED) are summarized, and some theories of OSF growth are critiqued. Then a new theory is developed which shows the growth to be reaction controlled, and the retrogrowth to be naturally a regime in the entire OSF growth process. The theory has provided an estimated bound on the activation energy of self-diffusion in silicon. It is shown that the observed power law growth kinetics can be explained quite naturally by a bimolecular annihilation process of the excess self-interstitials. A possible physical model of such an annihilation process is discussed. A number of phenomena related to the nucleation of oxygen precipitates in silicon are reported. Then a model of nucleation is presented which is shown to be consistent with all observed phenomena.In this model, the homogeneous nucleation proceeds not merely via the agglomeration of oxygen atoms, but in combination with small vacancy clusters. Evidence from the OSF and OED phenomena, and the nucleation of oxygen precipitates thus necessitates the dualism of vacancies and interstitials as thermal defects in silicon at high temperatures.
Enhanced Diffusion and Formation of Defects During Thermal Oxidation
Authors: Narayan J. , Fletcher J. , Appleton B. R. , Christie W. H.
Published: March 2011

Enhanced diffusion of dopants and the formation of defects during thermal oxidation of silicon has been investigated using electron microscopy, Rutherford backscattering, and secondary ion mass spectrometry techniques. Enhanced diffusion of boron was clearly demonstrated in laser annealed specimens in which secondary defects were not present. In the presence of secondary defects, such as precipitates, enhanced diffusion of boron was not observed. The absence of enhanced diffusion during thermal oxidation was also observed for arsenic in silicon. The mechanisms associated with thermal–oxidation enhanced diffusion are discussed briefly.
Raman Scattering Characterization of Bonding Defects in Silicon
Authors: Tsu Raphael
Published: March 2011

Raman scattering is used for the characterization of defects in Si. Damage is produced in single crystal silicon by ion-implantation of As and Si. The phonon structure of the damaged layer is that of the typical amorphous Si. After irradiation by pulsed laser(10ns,532nm) at energy density of approximately 0.1J/cm2, a Raman peak appears at a frequency between 508 cm−1 and 517 cm−1 depending on implant dosage. The higher the implant dosage, the lower is the frequency. We explain this in terms of the residual bonding defects caused by the presence of extraneous atoms such as oxygen. On the other hand, irradiation at an energy density in excess of 0.5 J/cm2, a Raman peak appears at a frequency close to that of the single crystal except for small shifts due to Fano-shift. For implant dosage in excess of 4×1016 As/cm2 , we have found additional peaks at 222 cm−1 and 267 cm−1 which are close to the metallic arsenic modes indicating the presence of arsenic clusters.
Luminescence Properties of GaAs Epitaxial Layers Grown By Liquid Phase Epitaxy and Molecular Beam Epitaxy
Authors: Petroff P. M.
Published: March 2011

The luminescence properties of undoped GaAs-Ga1−x Alx As layers grown by liquid phase epitaxy (LPE) and molecular beam epitaxy (MBE) are compared for double heterostructure and multiquantum well (MQW) superlattices. Low temperature cathodoluminescence and scanning transmission electron microscopy are used to identify the main luminescence centers and in some instances establish their origin. The possible effects of the observed luminescence features on the degradation process in GaAs-Gal−x Alx As laser devices grown by MBE and LPE are also discussed.
The Interrelationship Between Structure and Properties in InP and InGaAsP Materials
Authors: Mahajan S.
Published: March 2011

Three examples pertaining to the influence of heavy doping on the microscopic perfection of as-grown InP crystals, thermal decomposition of InP crystals and epi-layers and optically induced degradation of InGaAsP epi-layers have been chosen to delineate some of the correlations observed between microstructure and properties in these materials. It
is shown that the macroscopic perfection can be significantly improved by highly doping with Zn, S, and Se. However, in the case of Zn, not all of the dopant atoms are in solid solution and some of them have clustered to form precipitates, whereas these features are not seen in highly S- and Se-doped crystals.

Thermal decomposition of epi-layers introduces areas which appear dark in a photoluminescence scan. It is argued that these regions evolve due to the out diffusion of P. In addition, when InP epi-layers are grown on thermally-decomposed substrates, dislocation density in the epi-layers is higher than that in the substrate. Arguments have been developed to rationalize these observations.

Non-luminescent regions develop in InGaAsP epilayers by optical pumping. These areas are associated with dislocation clusters which appear to evolve by glide of the existing dislocations.
Electronic Defects in Metalorganic GaAIAs
Authors: Johnson N. M. , Burnham R. D. , Fekete D. , Yingling R. D.
Published: March 2011

Electronic defect levels have been measured in n-type epitaxial films of Gal - XAIXAs (0≤X≤0.33) which were grown by metalorganic chemical vapor deposition. Electron traps were characterized by transient capacitance spectroscopy on Schottky-barrier diodes. The thermal activation energy for electron emission from the near-midgap defect level is found to be larger in Ga1 - XAIXAs than the value of 0.83 eV generally observed in GaAs.
Tem and Sem Studies of Defects in Gainas and Gainasp Epitaxial-Layer Device-Type Structures
Authors: Al-Jassim M.M. , Hockly M. , Booker G.R.
Published: March 2011

TEM and SEM studies have been carried out on a series of GaAs/GaInAs, InP/GaInAs and InP/GaInAsP device-type structures grown either by vapour phase epitaxy (VPE) or liquid phase epitaxy (LPE). By using the TEM high voltage electron microscope operating at 1000kV, a determination was made of the nature, origin and three-dimensional distribution of structural defects in these specimens (mainly dislocations and stacking faults). SEM EBIC and CL examinations were also performed to study the electrical and luminescent properties of these layers. The ultimate aim is to correlate structural information with electrical and luminescent properties, and with device performance.
Microstructure of Polycrystalline Sic Containing Excess Si after Neutron Irradiation
Authors: Harrison S.D. , Corelli J.C.
Published: March 2011

The microstructure of commercially available reactionbonded polycrystalline SiC containing 8–10 wt% excess silicon was studied after irradiation by reactor neutrons uitlizing transmission electron microscopy (TEM) and scanning electron microscopy (SEM). For TEM studies on samples irradiated below 473°K we observe dislocation tangles near grain boundaries or impurities plus isolated dislocations throughout the remainder of the grain, whereas for irradiation temperatures of ≈3730°K the material exhibits copious quantities of “black spot” defects (2–5nm size) and a lower concentration of tangles than 473°K irradiation. The SEM studies of surfaces of samples fractured at 1473°K indicate that the mode of fracture is predominantly transgranular.
Point Defects, Diffusion Mechanisms, and the Shrinkage and Growth of Extended Defects in Silicon
Authors: Gösele Ulrich , Frank Werner
Published: March 2011

The paper introduces the basic point-defect models proposed for silicon, which involve either vacancies or self-interstitials only, or both types of point defects simultaneously under thermal-equilibrium conditions. The growth and shrinkage kinetics of oxidation-induced stacking faults as well as oxidation-enhanced or -retarded diffusion phenomena are discussed within the frame work of these models. Whereas no unambiguous conclusions on the dominant diffusion mechanism can be drawn from the available oxidation-related experiments, recent investigations on so-called anomalous diffusion phenomena (e.g., the ‘emitter-push effect’) and on the diffusion of gold in silicon demonstrate Si self-interstitials to be the point defects governing self- and impurity diffusion. The possibility of a coexistence of vacancies and self-interstitials in thermal equilibrium is discussed in this context. The paper concludes with speculations on how carbon in conjunction with self-interstitials may influence the nucleation process of oxygen precipitates in silicon.
Processing Effects on the Electrical and Optical Properties of Sulfur-Related Defect Centers in Silicon and Similarities to the Oxygen Donor
Authors: Forman Richard A. , Larrabee Robert D. , Myers David R. , Phillips Willie E. , Thurber W. Robert
Published: March 2011

The properties of sulfur-related defects in silicon are shown to differ dramatically from those that would have been expected on the basis of effective mass theory for a simple substitutional double donor. The ratio of the densities of the sulfur states as measured by capacitance-voltage techniques has been observed to vary in specimens fabricated from the same starting resistivity. Optical absorption studies have shown that the deepest sulfur level has a manifold of ground states which anneal at unequal rates at 550°C. Deep-level measurements show that the thermal emission rate at a given temperature and the variety of effects produced depends on annealing history and total sulfur density. The variability of properties of samples of sulfur-doped silicon is similar to those found for the oxygen donors in silicon, thus suggesting a chemical trend for the column VI impurities in silicon.
Defect Characterization by Junction Spectroscopy
Authors: Kimerling L. C.
Published: March 2011

Junction spectroscopic techniques provide a unique tool for the study of imperfections in semiconductor materials. New, fundamental defect processes have been discovered and direct observations of the role of defects in device manufacture and operation have been made. The principles of application of capacitance transient spectroscopy, electroluminescence, and SEM-charge collection microscopy are briefly reviewed. Examples of singular accomplishments of these techniques are given, and directions of future research are outlined.
Free-Electron Interlayer States in Pure and Li-Intercalated Graphite
Authors: Posternak M. , Baldereschi A. , Freeman A.J. , Wimmer E. , Weinert M.
Published: March 2011

First–principle SCF–FLAPW calculations prove the existence in graphite of a new kind of electron states. They are interlayer states, resulting from the bonding combination of states bound to single graphite layers, and give rise to a still undetected energy band just above the Fermi energy. This band also occurs at slightly lower energy in Li intercalated graphite, and has been incorrectly interpreted as arising mainly from Li 2s orbitals.
Superconductivity in Graphite Intercalation Compounds
Authors: Iye Yasuhiro
Published: March 2011

Superconductivity in graphite intercalation compounds, C4nMHg (M:K, Rb, n=1,2) and C4KTl1.5 is studied in ambient as well as elevated pressures. It is argued that the major role in the superconductivity of this class of materials is played by electrons in the intercalant bands rather than those in the graphite bands. It is experimentally demonstrated that the two-dimensional anisotropy of the superconductivity is controlled by stage and pressure.
Anomalous Pressure Dependences of the Superconducting Transition Temperature of Graphite Intercalation Compounds
Authors: Delong L.E. , Yeh V. , Tondiglia V. , Eklund P.C. , Lambert S.E. , Maple M.B.
Published: March 2011

Measurements of the pressure (P) dependence of the superconducting transition temperature Tc of KHgC4, KHgC8, KTℓ1.5C4 and KC8 are reported. KC24 was found to be nonsuperconducting to a limiting temperature T ≈ 0.07 K for P ≤ 10 kbar, and RbC8 was found to be nonsuperconducting to T ≈ 1.30 K for P ≤ 22 kbar. The Tc of KHgC8 was found to monotonically decrease at a rate dTc/dP = −6.5 × 10−5 K/bar from a zero pressure Tc = 1.850 K. The Tc of KTℓ1.5C4 initially decreases at a rate dTc/dP≤ −4.5 × 10−5 K/bar from a zero pressure Tc = 2.54 K. KHgC4 displayed a broad zero pressure superconducting transition with an onset at T ≈ 1.42 K, followed by an abrupt narrowing of the transition and rapid decrease of Tc at a rate dTc/dP = −5 × 10−5 K/bar at p > 1 kbar. The Tc of KC8 was observed to jump from a zero pressure value of 0.13 K to a broad transition with an onset at ˜ 1.7 K for P > 2 kbar.
Commensurate-Incommensurate and Melting Transitions in Bromine-Intercalated Single Crystal Kish Graphite
Authors: Erbil A. , Kortan A.R. , Birgeneau R.J. , Dresselhaus M.S.
Published: March 2011

We summarize the results of an extensive x-ray scattering study of the phase transitions in intercalated graphite-Br2 compounds. The experiments are aimed at understanding the intraplanar and interplanar correlations of the intercalate bromine as a function of temperature. Using in-situ high resolution x-ray scattering techniques, we have studied stage-4 graphite-Br2 under equilibrium conditions, where the intercalant is in the commensurate phase, incommensurate phase, and fluid phase. We demonstrate that the transitions between these phases are model examples of phase transitions in quasi two-dimensional systems. The coherently ordered in-plane bromine regions exceed 10000 Å in size in both commensurate and incommensurate phases. A commensurateincommensurate transition in the 7–fold direction is observed from a centered (√3 × 7) phase to a stripe domain phase. The domain wall density exhibits a power-law behavior in temperature with an exponent of 0.50 ± 0.02. We have also observed power-law lineshapes for bromine superlattice peaks in the incommensurate phase due to the rigorous absence of true long range order. The intercalate layer appears to exhibit an anisotropic melting transition from an incommensurate solid to a novel fluid phase.
Phonon Dispersion of Transverse Basal Plane Modes in Alkali-Graphite Compounds
Authors: Kamitakahara W. A. , Zabel H. , Nicklow R. M.
Published: March 2011

Dispersion curves for low-frequency transverse modes propagating in the basal plane have been measured in the compounds KC8, KC24 and RbC24 by means of neutron inelastic scattering. The acoustic branches show at low q a behavior ω2= Aq2+Bq4 characteristic of layered materials. The optical branches are derived qualitatively from graphite-like optical branches hybridized with new alkali-like branches. In stage 2 compounds, the shear constant C44, which can be obtained by extrapolating the acoustic branch towards q=0, is appreciably smaller than in stage-1 compounds or in pure graphite. At low temperatures, it was noted in KC24 that a frequency gap in the acoustic branch opens up near q=0.6 A-1, corresponding to the Brillouin zone boundary of the low temperature alkali superstructure.
Intercalate Phonon Densities of States for Alkali-Graphite Compounds
Authors: Kamitakahara W. A. , Zabel H.
Published: March 2011

Neutron scattering methods have been used to determine the partial phonon densities of states gM(ν) for inplane vibrations of M atoms in MCx compounds, where M = K, Rb or Cs, and x = 8, 24, 36. Only modes with both phonon wave vectors and displacements in the basal plane are represented in gM(ν). Detailed measurements of the temperature dependence were made for RbC24 and KC24, in order to study the influence of the order-disorder transformations in these compounds. The results are interpreted in terms of different pictures of the disordered state.
Populations of Fluorine and Arsenic in AsF5-Graphite Intercalation Compounds
Authors: Sfihi H. , Facchini L. , Bouat J. , Bonnin D. , Legrand A.P. , Furdin G. , Billaud D.
Published: March 2011

19F nuclear magnetic resonance and As X-ray absorption results on AsF5-graphite intercalation compounds are discussed in terms of species of the commonly used oxidation reaction of the graphitic planes. Three fluorine populations and two oxidation states of the arsenic are clearly present, but they cannot be easily related to the oxidation reaction of the graphite planes.
57Fe Mössbauer Spectroscopic Study of the Geometrical Effects In the Catalytic Reactions with Intercalation Compounds
Authors: Vaishnava P.P. , Montano P.A.
Published: March 2011

In situ 57Fe Mössbauer spectra are reported for the first-, higher-stage ferric chloride, and a mixed ferric chloride-potassium chloride intercalated graphite catalysts under reduction and Fischer-Tropsch reaction conditions. The mass spectroscopic measurements reveal a different catalytic selectivity for the three catalysts. The first two catalysts predominantly possess a higher selectivity for methane, whereas the third catalyst has higher selectivity for the formation of propane. The differences are attributed to geometrical effects in the catalytic sites of the intercalated compounds.
Study of the Orientation of Molecules Intercalated in Graphite using Nuclear Photon Scattering
Authors: Moreh Raymond , Shahal Oded
Published: March 2011

A new technique utilizing nuclear resonance scattering of photons from isolated nuclear levels in the 6-9 MeV range is being used for studying the orientation of certain intercalant molecules with respect to the graphite (G) planes. This technique may be applied to intercalants containing 11B, 15N, 39K, 48Ti, 50Cr, 56Fe, 62Ni and 68Zn. As an example, the orientation of the HNO3 molecules intercalated in HOPG was studied by photon scattering from the 6.324 MeV level in 15N. Thus in C10 (HNO3) and C15(HNO3), the NO3 planes were found to be oriented at θ ˜ 90° relative to the G planes, while in the mixture of the ‘residue’ compounds C16(HNO3) and C24(HNO3), the NO3 planes were found to be nearly parallel, θ0 < 25°, relative to the G-planes.
Basic Thin Film Process for Perovskite Ferroelectric Materials
Authors: Adachi Hideaki , Wasa Kiyotaka
Published: March 2011

Thin film process for ferroelectric perovskite oxides has been investigated. Amorphous, polycrystal, and epitaxial thin films of Pb-based perovskite ferroelectrics were prepared by rf-magnetron sputtering, and their properties were discussed. Epitaxial PLZT thin films showed similar dielectric properties as PLZT bulk ceramics and also showed strong electrooptic effect. For further investigation, film preparation process was developed by multitarget sputtering and quaternary PLZT thin film with excellent epitaxial crystallinity was realized by using a graded composition layer.
Ferroelectric Thin Films Deposited by Laser Ablation
Authors: Ramkumar K. , Lee J. , Safari A. , Danforth S.C.
Published: March 2011

The deposition of thin films of ferroelectric materials by the laser ablation technique was investigated. The films were grown by ablation from a bulk target of lead zirconate titanate (PZT) exposed to laser pulses from CO2 amd KrF excimer lasers. The effects of deposition and annealing conditions on the structure and stoichiometry of the films were studied.
Processing Induced Strain Relaxation in BaTiO3 Films
Authors: Sanchez-Carambot E. , Martinez-Miranda L.J. , Smela E. , Shi Y. , Santlago-Aviles J.J.
Published: March 2011

The development of integrated electronic devices has resulted in an increased interest in the study of ferroelectric ceramic films on silicon prepared by diverse methods. Some of these studies aim at the development of films whose ferroelectric properties equal or approximate those of the bulk ceramic. It is therefore important to attain a better understanding of the microstructure of these films and the relationship between the microstructure and the different film preparation methods. This study examines the strain field in such a film as a function of annealing time. The technique chosen was grazing incidence x-ray scattering (GIXS), and the material, thin films of BaTiO3 deposited on silicon (111) single crystals by metallo-organic deposition (MOD). The BaTiO3 {110} and {101} reflections were monitored. A substantial relaxation of the d-spacing of planes parallel to the surface was measured after a 64 hour annealing. The d-spacing of planes perpendicular to the surface remained essentially unchanged.
Ten Analyses Of Sol-Gel Derived And Sputtered PZT Thin Films
Authors: Hsueh Cheng-Chen , MeCartney Martha L.
Published: March 2011

Ferroelectric PZT thin films were prepared by sol-gel methods and RF magnetron sputtering. Sputtered PZT fast fired at 650° for 30 minutes showed microporosity. For the sol-gel route, solution precursors had a significant effect on the microstructure of the crystalline PZT films. PZT thin films derived from metal-organic precursors dissolved in n-propanol were observed to have large and microporous spherulitic grains on the order of 2 μm and phase separation in acetic acid-catalyzed films. In contrast, PZT precursors originated from alcohol exchanges with 2-methoxyethanols resulted in dense films with fine grains of ∼0.2 μm and clear evidence of ferroelectric domains. The dense sol-gel films possessed superior dielectric and ferroelectric properties.
Electro-Optic and Non-Linear Optical Coefficients of (Pb, La)(Zr, Ti)O3, BaTiO3, (Sr, Ba)Nb2O6 and Ba2NaNb5O15 Thin Films
Authors: Wu A. Y. , Wang Feiling , Juang Ching-Bo , Bustamante Carlos
Published: March 2011

The electro-optic properties of sputter-deposited PLZT, BaTiO3, SBN, and BNN films on fused silica substrates have been studied using a confocal scanning optical polarization microscope. The Pockels, Kerr, and higher order electro-optic coefficients and their relations to the non-linear optical coefficients in the films are presented. The materials and physical properties of the films are discussed.
Characterization of Ferroelectric Thin Films by ESCA
Authors: Desu Seshu B. , Kwok Chi K.
Published: March 2011

Electron spectroscopy for chemical analysis (ESCA) is well suited for investigating the surfaces of ferroelectric films. More importantly, this technique is valuable for ferroelectric films because, reduction of ions, such as Pb2+, Bi3+, and Ti4+ by photon beam is much less likely than probing electron and ion beams which are used in other methods. In the present paper a brief description of the possibilities of ESCA for determining qualitative and quantitative surface composition, and thickness of extremely thin films was presented. Special emphasis was given to multicomponent films, such as lead zirconate titanate (PZT). Factors that lead to considerable difference in the composition of the surface were discussed. Different depth profiling techniques using ESCA were also presented.
Scaling Properties in the Electrical and Reliability Characteristics of Lead-Zirconate-Titanate (PZT) Ferroelectric Thin Film Capacitors
Authors: Sudhama C. , Carrano J. C. , Parker L. H. , Chikarmane V. , Lee J. C. , Tasch A. F. , Miller W. , Abt N. , Shepherd W. H.
Published: March 2011

This paper investigates the issues in the scaling of thin film PZT (Lead-Zirconate-Titanate) capacitors for DRAM (Dynamic Random Access Memories) applications. The test structures used were MIM (metal-insulator-metal) capacitors with platinum electrodes and PZT deposited using a sol-gel process. Charge storage density (Q'c), leakage current density (JL), unipolar switching time to 10% decay (ts), time dependent dielectric breakdown (TDDB) and electrical fatigue have been analyzed. Unipolar switching time has been modeled as an RC time constant, where C is electric-field dependent. Q'c at a given electric field appears to remain constant over the range of film thicknesses and electrode areas studied. Leakage current density and time-to-breakdown (tBD) for a given electric field degrade with decreasing film thickness. Unipolar stressing causes considerably less fatigue than bipolar stressing, and after 2 × 1011 cycles, a 400nm film still exhibits sufficient Q'c for DRAM operation.
Lead Zirconate Titanate Films Produced by ‘Facing Targets’ RF-Sputtering
Authors: Roy R. A. , Etzold K. F. , Cuomo J. J.
Published: March 2011

The growth of ferroelectric lead zirconate titanate (PZT) films by rf-sputtering using facing targets is described. This study has focused on producing thin (<500 nm) PZT films on a wide range of substrates including magnesium oxide, spinel, alumina, silicon oxide, and the respective substrates coated with platinum. Deposition was from two opposed targets separated by 10–15 cm, with the substrate plane normal to the targets and outside the cylinder defined by the two targets. This geometry was chosen to obtain compositional uniformity and avoid ion bombardment effects. The deposition temperatures ranged from RT to 700 °C and the process gas was a mixture of argon and oxygen. Effects of deposition conditions and post-deposition annealing on film composition, microstructure, and properties were evaluated using Rutherford backscattering spectroscopy (RBS), x-ray diffraction, optical and electron microscopy, and various electrical measurements. Optimization of process conditions is discussed in terms of phase purity, preferred orientation, and minimization of electrode interaction.
Physical and Electro-Optical Properties of Ion Beam Sputtered Thin Film PLZT Ceramic
Authors: Boyer L.L. , Wu A.Y. , Mcneil J.R.
Published: March 2011

High quality PLZT thin films have been deposited using ion beam sputtering. The deposited material has perovskite crystal structure tetragonal in phase with the c-axis predominantly normal to the surface. Material deposited at temperatures below 450°C has pyrochlore structure while that deposited above 650°C displays polycrystalline characteristics. The deposition rate was approximately 0.2–0.5 Å/sec yielding film thicknesses of ∼4500 Å. The surface morphology of the deposited films is of high quality with a RMS roughness 60% that of magnetron sputtered films.
High-Rate Etching of Mn-Zn Ferrite by Laser-Induced Chemical Reaction in CC12F2 Atmosphere
Authors: Lu Y. F. , Takai M. , Nagatomo S. , Namba S.
Published: March 2011

Maskless dry etching of Mn-Zn ferrite in dich1orodif1uoromethane (CC12F2) by Ar+-ion laser (514.5 nm-line) irradiation has been investigated to obtain high etching rates and aspect-ratios of etched grooves. The etching reaction was found to be thermochemical and caused by Cl radicals thermally decomposed from CCl2F2 gas. High etching rates of up to 360 μm/s, which is about one order of magnitude higher than that in a CCl4 gas and even higher than that in a H3PO4 solution, have been achieved. A high aspect-ratio of up to 12 was obtained. Definite gas pressure and dwell time are necessary to fabricate a smooth groove.
Effects of Processing Parameters on the Laser Deposition of High Temperature Superconducting Thin Films
Authors: Nogar N. S. , Castain R. , Dye R. C. , Foltyn S. , Muenchausen R. E. , Wu X. D.
Published: March 2011

Y2O3 pressed powders were ablated by pulses from a XeCl excimer laser, operating at 308 nm, 150 mj/pulse, ≈15 nsec/pulse and 20 Hz. Emission spectra from Y∗ and YO∗ were recorded as a function of ambient oxygen pressure in the range 10−5 − 4×10−1 Torr, at a laser fluence of ≈ 4 J/cm2. A kinetic model is developed to describe the results, and the application to production of laser-deposited high-temperature superconductor thin films is discussed.
Implantation of 1.5 MeV Ag+ Ions in Silica Glass
Authors: Fukumi K. , Chayahara A. , Hayakawa J. , Satou M.
Published: March 2011

Ag+ ions were implanted in silica glass at an acceleration energy of 1.5MeV. It is found that Ag atoms are present in both the metallic and ionic states. Ag atoms in the metallic state increase when the Ag atom concentration increases. It is shown that the structure of damaged glass recovers monotonically from the surface to the inside of the glass. The state of the Ag atoms does not depend on the glass structure damaged by ion implantation.
High Dose Ion Implantation for the Synthesis of Si1−xGex Alloys
Authors: Howard D. J. , Paine D. C. , Stoffel N. G.
Published: March 2011

High dose ion implantation followed by solid phase epitaxy has been investigated for use in the synthesis of defect-free graded alloys of Si1−xGex. Two implanted alloy systems were studied: (i) 200 keV 74Ge into <001> Si to form Si-rich alloys and (ii) 150 keV 29Si into <001> Ge to form Ge-rich alloys. After regrowth by solid phase epitaxy the Ge-rich alloys are strained in tension while the Si-rich alloys are in compression and, as a result, strain relaxation is anticipated above a critical dose. We report that solid phase epitaxy at 550°C following implantation of Si into <001> Ge at an energy of 150 keV allowed the defect-free regrowth of alloys with peak concentrations of 11 ± 2 at. % Si (fluence of 7.7 × l016/cm2). Ge was implanted at 200 keV into <001> Si to a peak concentration of 7 at. % (fluence of 3.6 × l016/cm2) and was regrown without the introduction of defects whereas samples implanted to a peak concentration of 13 at. % (fluence of 5.3 × l016/cm2) contained a high density of stacking faults. These experimental observations are compared to theoretical predictions that are based on the strain energy approach.
Characteristics of 56 Mev Oxygen Implantation into Si and III-V Semiconductors
Authors: Pearton S. J. , Jalali B. , Poate J. M. , Fox J. D. , Kemper K. W. , Magee C. W. , Jones K. S.
Published: March 2011

High energy (56 MeV) oxygen implants into Si, GaAs and InP give rise to sharp, non-Gaussian depth profiles with the distributions skewed towards greater depths. This skewness is probably the result of channeling, and it is a common feature of MeV implants into semiconductors. The ratio of the peak concentration in the depth profile to the concentration at the surface is ≥103 for each material, and the full width at half maximum of each profile is ∼2 μm. The experimental projected ranges for the oxygen are ∼31 μm in GaAs, ∼36 μm in InP and ∼46 μm in Si. These are ∼10% larger than the values predicted by the PRAL code. The photoluminescence intensity from the top 1 μm from the surface of both GaAs and InP is reduced by more than an order of magnitude for 56 MeV oxygen implants at a dose of 1.3 × 1015 cm−2, due to point defect introduction in this region. Potential applications for these high energy implants in electronic and photonic device fabrication will be discussed.