bluuebunny/crossref_metadata_2025 huggingface dataset:
Epitaxial CeO2 on Silicon Substrates and the Potential of Si/CeO2/Si for SOI Structures
Authors: Morshed A. H. , Liu S. X. , Leonard R. , Mcintosh F. G. , El-Masry N. A. , Bedair S. M.
Published: April 2011

CeO2 is nearly lattice matched to Si and has the CaF2 cubic structure thus it offers the potential for the epitaxial growth of an insulating film on Si. Laser ablation of a CeO2 target in an ultra high vacuum system was used for the deposition of single crystal CeO2. The effect of post growth thermal and rapid thermal annealing in O2, N2 and Ar atmosphere was found to have pronounced effects on the electrical properties measured by C-V and the optical properties measured by photoluminescence.

We report on our initial results for the growth of epitaxial Si on the deposited CeO2 using low pressure CVD. Both RHEED and TEM studies showed that single crystal epitaxial Si was deposited on CeO2. The details of the Si deposition on CeO2 films for potential of SOI (silicon on insulator) structures will be discussed.
Intrinsic Point Defects on a TiO2(110) Surface and Their Reaction with Oxygen: A Scanning Tunneling Microscopy Study
Authors: Kuhn Markus , Anderson J. F. , Lehman Jeremy , Mahmoud Talib , Diebold Ulrike
Published: April 2011

The interaction of molecular oxygen, at room temperature, with a reduced TiO2(110) surface has been studied in situ by scanning tunneling microscopy (STM). Oxygen vacancies (point defects) were created on a clean TiO2(110) surface by annealing in ultra-high vacuum and successfully imaged on the atomic scale. These point defect sites were stable under ultrahigh vacuum conditions. During exposure to molecular oxygen, new point defects appear at different locations on the surface although their overall number is reduced. A mechanism for this dynamic healing process is proposed.
Epitaxial Growth And Optical Properties of Sol-Gel (Pb,La)Ti03 Thin Films for Waveguides
Authors: Koo Junmo , Lee Changho , No Kwangsoo , Bae Byeong-Soo
Published: April 2011

Lead lanthanum titanate thin films have been prepared on MgO and sapphire substrates by sol-gel method. XRD analyses confirm that the PLT films fabricated on MgO(lOO) and c-plane sapphire substrates grow preferentially with (100) and (111) orientations, respectively. The PLT films with a high La content have a low refractive index due to the decrease of the refractive index anisotropy. The propagation losses in PLT films measured, using He-Ne laser light and the prism coupling method decrease as the La content increases. This is due to the reduction of the refractive index anisotropy and the surface scattering by the surface roughness as a function of La content in the film.
Microstructural Development Of thin CoCrTa Films on Cr Underlayers
Authors: Ross C.A. , Ross F.M.
Published: April 2011

The structure of 2.8 – 60nm thick films of CoCrTa sputtered onto a 50nm Cr underlayer at 250°C was studied using atomic resolution microscopy. The Cr grows with a (200) orientation and the CoCrTa grows epitaxially with the [0002] axis in the film plane. The thinnest films have a discontinuous microstructure with several CoCrTa nuclei forming on each Cr grain, with slight misalignment from the exact Pitsch-Schrader orientation relation. The CoCrTa grains coalesce as the film thickness exceeds lOnm and there is evidence for stacking faults at all film thicknesses. For most films the magnetic switching volumes are of similar size to the physical grain volume, suggesting that the entire grain volume participates in magnetic switching.
Unusual Magnetic Behaviour of BCT Fe Thin Films Evidenced by 57Fe Mössbauer Spectrometry
Authors: Andrieu S. , Bauer Ph. , Lemine O. M. , Snoeck E. , Piecuch M.
Published: April 2011

Unusual magnetic behaviours occur in thin Fe films grown on Ir(100) by Molecular Beam Epitaxy. Four different magnetic sites are actually observed in these layers by Conversion Electron Mössbauer Spectrometry. The magnetic relaxation phenomena found in the strained FCC structure together with spin wave softening observed in the strained BCC structure point to small magnetic correlations along the growth direction.
Magnetic Anisotropy in Single Crystal Terfenol-D Thin Films
Authors: Oderno V. , Dufour C. , Dumesnil K. , Mougin A. , Bauer Ph. , Mangin Ph. , Marchal G. , Patrat G.
Published: April 2011

Tb03.Dy0.7Fe2 (known as Terfenol-D) thin films have been epitaxially grown for the first time with [110] as the growth direction. X-Ray diffraction measurements evidence that the films are strained compared to the bulk alloy. Mössbauer spectroscopy and Kerr rotation measurements show that the easy magnetization direction varies from <116> at 4.2 K to around <133> at 300 K. This variation is different from the bulk case (for which the magnetization is along <100> at 4.2 K and along <111> at room temperature). This effect can be qualitatively understood if we consider the influence of the strains induced by epitaxy on the various energy terms which govern the direction of magnetization.
Step-Induced Magnetic Defects in Fe/Cr Systems
Authors: Freyss M. , Stoeffler D. , Dreysse H.
Published: April 2011

We present the results of calculations of the magnetic order in Fe/Cr systems with a mono-atomic step at the interface. The study of such a systems is of particular interest since it is believed that topological defects play an essential role in the exchange coupling mechanism in Fe/Cr multilayered systems. We show that assuming only collinear magnetism, an interfacial step creates a very extended magnetic defect in the Cr layer. On the other hand, when the local magnetic moments are allowed to rotate, the magnetic defect is very localized near the step and the presence of the step induces a non-collinear coupling between the Fe layers in Fe/Cr superlattices.
Magnetic anisotropy of Fe/Cu(100) over- and interlayers
Authors: Újfalussy B. , Szunyogh L. , Weinberger P.
Published: April 2011

The perpendicular magnetic anisotropy in Fe/Cu thin film over- and interlayers is investigated in terms of the fully relativistic spin-polarized band theory. The formation of the ground state is addressed and a layer-resolved analysis of the magnetic anisotropy energies for the Fe/Cu(100) and the Cu/Fe/Cu(100) system is presented both for ferromagnetic and anti-ferromagnetic cases.
Domain Topology of Micron-Scale, Ferromagnetic Pancakes
Authors: Bedrossian Peter J. , Gibbons Matthew R. , Cerjan Charles J.
Published: April 2011

Planar, micron-scale ellipses patterned from 700Å-thick Co films exhibit nearly-complete suppression of hysteresis when magnetized in-plane along their short axes. Using a combination of Magnetic Force Microscopy and Vibrating Sample Magnetometry, we find that the suppression of hysteresis is associated with the continuous deformation of a dipole field configuration. The presence of hysteresis for in-plane, long-axis magnetization is associated with transitions between topologically inequivalent configurations.
Magnetic Properties of Multilayered Co-Cu Granular Composites
Authors: Cabbibo A. , Caballero J.A. , Park Y.D. , Childress J.R.
Published: April 2011

The magnetic properties of granular CO25Cu75/CU multilayer films prepared by sputtering onto heated glass substrates have been investigated in the range of ultrathin alloy films (5–250Á) and Cu spacer thicknesses (0–50Å). Both the coercive field at 10K and the maximum superparamagnetic blocking temperature TB are found to be sensitive to finite-size effects in single-layer films, and to interactions between layers in multilayer films. Our results indicate that the magnetic properties of granular alloy layers can be engineered to a large extent by selectively modifying the local environment of the Co particles.
Residual Stresses in Ultrathin Metal Sublayers Within Au/Ni Multilayers
Authors: Labat S. , Gergaud P. , Thomas O. , Gilles B. , Marty A. , Lefebvre S.
Published: April 2011

Metallic Multilayers (MLs) have attracted a considerable interest during these last years because of their unusual properties. In small periods ML's (a few nm) the high density of interfaces give rise to structures very far from equilibrium. Au/Ni multilayers have been grown in the (111) orientation by M.B.E. on Si(100) via a Cu(100) buffer layer. Two different parameters have been studied: the Au:Ni ratio at constant (4 nm) superperiod and the superperiod at constant (1:1) Au:Ni ratio. The full strain state of Au and of Ni has been determined via x-ray diffraction measurements. The high lattice parameter misfit beween Au and Ni (14%) implies that all the layers are partially relaxed. Residual strains as high as several % are encountered. The residual strain in the Au layers is clearly correlated with their thickness. A residual stress as high as 3.9 GPa is determined in the thinner layers.
Magnetization on Vicinal Ferromagnetic Surfaces
Authors: Zhao D. , Liu Feng , Huber D.L. , Lagally M.G.
Published: April 2011

Using Ising model Monte Carlo simulations, we show a strong dependence of surface magnetization on surface miscut angle. For ferromagnetic surfaces, when surface spin exchange coupling is larger than that of the bulk, the surface magnetic ordering temperature decreases, toward the bulk Curie temperature, with increasing miscut angle; when surface spin exchange coupling is smaller than that of the bulk, a crossover behavior occurs: at low temperature, the surface magnetization decreases with increasing miscut angle; at high temperature, the reverse is true.
Anomalous Behavior in Spin Dependent Tunnel Junctions
Authors: Platt C. L. , Dieny B. , Berkowitz A.E.
Published: April 2011

Spin dependent tunneling has been investigated in tunnel junctions composed of a variety of materials. The best results thus far have been with either HfO2 or MgO as the barrier layer using CoFe, Fe, or Co as the magnetic electrodes. The maximum magnetoresistive (MR) response of these junctions has been at low temperatures on the order of 30% in HfO2 and 20% in MgO. We have also observed a variety of anomalous behavior in some of our tunnel junctions at low temperature. These include MR effects dependent on the angle of orientation of the tunnel junction in the applied magnetic field, transition fields greater than lOkOe, and negative MR effects on the order of 2%.
Noncollinear Phase of Magnetic Multilayers
Authors: Morosov A. I. , Sigov A. S.
Published: April 2011

There is considered the dependence of magnetic ordering type in multilayer structures on the magnitude of exchange interaction between magnetic layers and the interlayer surfaces roughness. With a simple example of the three-layered structure we found the areas of the existence of such states as: (i) domain structure, (ii) noncollinear ordering of homogeneous magnetic layers, (iii) collinear ferromagnetic phase, and (iiii) collinear antiferromagnetic phase.
Magnetic Field Sensors for Magnetic Position Sensing in Automotive Applications
Authors: Heremans Joseph P.
Published: April 2011

Magnetic position sensors are transducers whose output is an electrical signal that is a function of a mechanical motion. They consist of a permanent magnet, a magnetic field sensor, and a moving magnetic circuit. Being contactless, they do not wear out. Unlike optical systems, they are impervious to contamination. With the proliferation of microprocessor control in many on-board automotive applications, magnetic position sensing becomes a crucial function, found e.g. in cam and crankshaft sensors used for ignition timing and engine misfire detection, in brushless electrical motors, in wheel speed sensors and in other applications.

This paper first reviews the requirements put on the magnetic field sensors in these applications. Five main types of field sensors are used: Si Hall sensors with integrated amplifiers, GaAs Hall sensors, InSb-based magnetoresistors, anisotropie magnetoresistors (AMR), and metal-multilayer magnetoresistors (GMR). Magnetoresistors are almost always used as differential pairs, either in Wheatstone bridges or with matched constant current sources. The two characteristics of each type of field sensors that matter most are their sensitivity to magnetic field, and the smallest amount of field modulation they can detect, i.e. their resolution, which is mainly limited by the drift of the outputs with temperature. These parameters are measured and reported here on the 5 types of sensors; the work is an update of a 1993 review by the author.
Giant Hall Effect and Spin-Dependent Transport in Granular NiFe-SiO2 Films
Authors: Yan X. , Pakhomov A. B. , Jing X. N. , Wong S. K.
Published: April 2011

In granular NiFe-SiO2 films which display giant Hall effect, extraordinary Hall resistivity ρxys, normal Hall resistivity ρxyo, and magnetoresistivity δρ, were all found to follow power lav dependencies on resistivity ρ. Namely, -ρxys ∼ ρ0.81, -ρxyo ∼ ρ0.64 and -δρ ∼ ρ1.15. We propose that the presence of nanometer sized particles in the percolating conduction channels gives rise to I giant enhancement for both ordinary and extraordinary Hall effect in magnetic metal-insulator nanocomposite films. This physical picture describes qualitatively well the general features of GHE, and its correlation with resistivity and magnetoresistivity.
Influence of Dielectric Film Thickness on the Magnetic Properties of the Magneto-Optical Multilayer Films
Authors: Miao X.S. , Chan Y.C. , Huang Y.M. , Liu W.Z. , Lee Z.Y.
Published: April 2011

The magnetic interaction of magneto-optical multilayer films have been analyzed using the stress mechanism of coercivity and the single ion model of magnetic anisotropy. The relation between the magnetic properties of the multilayer films and the dielectric film thickness has been explained.
Chemical-Mechanical Polishing of Polymer Films: Comparison of Benzocyclobutene(BCB) and Parylene-N Films by XPS and AFM
Authors: Yang G.-R. , Zhao Y.-P. , Neirynck Jan M. , Murarka Shyam P. , Gutmann Ronald J.
Published: April 2011

The quality of benzocyclobutene (BCB) and Parylene-N (PA-N) films after chemical-mechanical polishing (CMP) is influenced by 3 factors: slurry composition, quality of the as-deposited film or post-deposition treated film, and polishing time. The quality of the films has been investigated by using X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). It is shown that the higher the quality of the as-deposited film (or post-deposition treated film), the higher the quality of the polished film. The polishing time has little effect on the surface characteristics of high quality PA-N films, however it has an effect on BCB film. This is attributed to the structure and thermal-stability and higher chemical resistance of PA-N. The RMS surface roughness measured by AFM, for as-deposited PA-N is 90Å. The roughness after CMP processes is greater than 200Å. The roughness for as-spin-coated and polished BCB film is 5A, and 20Å, respectively. The morphology of the PA-N film, either as-deposited or polished, is not as good as the BCB film. A slurry which is good for BCB polishing is not good for PA-N polishing, and vice versa. These results indicate that the nature of the polymer film, including its chemical structure as well as the quality of the as-deposited/post-deposition treated film, plays an important role in polymer CMP.
Low-k Dielectric Integration Cost Modeling
Authors: Korczynski Ed
Published: April 2011

The wide variety of low-k dielectric materials and processes for ULSI interconnection were sorted to create generic process flows. Average material and equipment costs were then used as inputs to a generic cost-per-wafer (CPW) model for dielectric deposition (not including the costs of dielectric CMP, metallization, or lithography). The model outputs are internally consistent, and useful for comparison of similar processes.
Adhesion of a-C:F during oxygen plasma annealing
Authors: Matsubara Y. , Endo K. , Tatsumi T. , Horiuchi T.
Published: April 2011

Fluorinated amorphous carbon (a-C:F) films sandwiched between layers of SiO2 have been proposed as an interlayer dielectric (ILD) structure in order to enhance resistance to oxygen plasma. This study describes adhesion failure mechanisms for the sandwiched fluorinated amorphous carbon film (a-C:F) structure during oxygen plasma annealing. We have found 3 failure modes: 1) capping SiO2 layer peels off, 2) thickness reduction of a-C:F by decomposition, and 3) etching phenomena at the interface between SiO2 and a-C:F by CFx outgassing from a-C:F. The outgassed CFx radicals were stored at the interfaces and the etching of SiO2 occurred during the subsequent 150°C oxygen plasma resist removal process. Thermal decomposition of a-C:F ILD sandwiched between layers of SiO2 was performed to determine the outgassed species, as well as the thickness reduction of a-C:F.
Physical Characterization of Photosensitive Polyimide
Authors: Zou Y.L. , Alford T.L. , Mayer J.W.
Published: April 2011

Polyimides prepared from oxydiphthalic anhydride and diamine precursors can be photosensitive. The thermal, mechanical, and dielectric properties of the polyimide films have been characterized with various techniques. The thermal decomposition temperature of the cured film is 520 °C, and the coefficient of thermal expansion is 20 × 10−6/°C. The polymer chemistry and processing conditions result in a low stress (<26 MPa) in the polyimide film as measured in situ during the curing and cooling cycles. Pads of 6 μm were patterned through the photosensitive polyimide at a sensitivity of 110 mJ/cm2 to i-line wavelength. The polyimide films exhibit anisotropy with an in-plane refractive index of 1.74 and an oul-of-plane index of 1.62 measured at 632.8 nm wavelength. This indicates a preferred orientation of polymer chains in the film plane. The estimated dielectric anisotropy should be considered a major factor for device design and optimization.
Adhesion Strength and Deformation Behavior of Al(Cu-Si)/BPDA-PDA Layered Structures
Authors: Abramowitz P. , Ogawa E. , Ho P. S. , Wetzel J.
Published: April 2011

The adhesion of Al(Cu-Si) line structures on thin films of BPDA-PDA with different surface preconditioning were examined by measuring the deformation energy of the metal and interface. The properties of BPDA-PDA/Al(Cu-Si) were examined with atomic force microscopy (AFM). Although different sputtering treatments profoundly affect the adhesive properties, the sputtering does not appreciably change the topology of the BPDA-PDA. We also found evidence that even though the thickness of the interface can be very small (3–5 nm), the polymer/metal interface can greatly affect the deformation behavior of the entire system.
Material and Interface Characterization of Cu99Ti1 Thin Films Metallized on Polyimide
Authors: Kondoh E. , Nguyen T.P.
Published: April 2011

Copper films with a small amount of an alloy element (1 wt % Ti) were metallized on polyimide. Plasma pre-treatment of the polyimide surface and post-metallization annealing were used to modify the interface. Interfaces and metal film layers were investigated; a drastic increase in adhesion strength, the suppression of Cu diffusion into polyimide, and the improvement of (111) texture were found. Composition analysis data taken from the interface indicated the accretion of nitrogen at the interface. The formation of Ti-related chemical bonds, suggested by X-ray photoelectron spectroscopy, can explain the above-mentioned experimental results.
The Preparation of Submicron Precision Cross Sections by Dimpling With A ‘Flatting Tool’
Authors: Humiston Helen L.
Published: April 2011

The complex materials systems in VLSI devices require specialized preparation techniques for TEM microstructural analysis. For this purpose, it is desirable to obtain electron transparency in all material layers from the oxides used in dielectrics to refractory metals such as tungsten. The primary advantage of dimpling these materials is that ideal specimens are obtained for low angle ion milling. By dimpling both sides of the cross section with a padded flatting tool, a thicker specimen of 130μm at the outer rim of the 3mm disc is produced that narrows to the 125nm thickness fringes in the center. These samples do not require a copper support grid, thereby allowing for a lower milling angle of 2.5 degrees on both sides of the specimen. This technique provides a cross section that is electron transparent in all layers without the loss of oxides due to differential thinning rates of various materials at higher milling angles.

It is generally thought that precision thinning through a submicron feature is not possible on the dimpler. However, a simple step-by-step procedure for this technique will be demonstrated and discussed.
Applications of Reactive Gas Plasma Cleaning Technology in Minimizing Contamination Of Specimens During Transmission and Analytical Electron Microscopy
Authors: Roberts S. P. , Zaluzec N. J. , Walck S. D. , Grant J. T.
Published: April 2011

The generation and usage of a reactive gas plasma for a wide range of applications has been cited since the early 1970's. More recently, the use of a plasma generating system has been applied to analytical transmission electron microscopy to minimize and, in some cases, eliminate the problems associated with various contamination sources, including the specimen holder and the specimen itself. Although the technology is well known, no definitive characterization of process parameters has been developed for specimen and specimen holder cleaning applications. An investigation of the effects that power levels and gas mixtures have upon contamination rates and removal were done using a Philips CM30T. Measurements of contamination rates both prior to and following plasma cleaning were done to characterize the effects of various parameter changes. Results of different process parameters and contamination rates will be reported.
The Effects of Gas Composition on the Ion Milling of Cross Sectional Tem Samples Containing Carbon Layers
Authors: Walck Scott D. , Scheltens Frank J. , Nainaparampil Josekutty J.
Published: April 2011

During conventional ion milling of carbon thin films on Si or SiC, the carbon has a much slower milling rate than the Si, SiC, and the epoxy resin. As a result, the substrates were thinned much more rapidly than the carbon films. A solution suggested by several subscribers to the Microscopy Society of America's Microscopy Listserver among others was to reactively ion mill the samples with a 20–25% oxygen-argon gas mixture. Is this the best inert gas to use? Neon has a mass that is between Si and C and therefore should impart a higher energy transfer to the C atoms than Ar. To determine whether the mass of the inert gas is important in balancing the milling rates, four gases were used to ion mill samples of a PLD DLC film with a nominal thickness of 0.5 μm. For improved adhesion of the films to the Si substrate, an initial 2 nm of Ti and a nominal 0.5 μm thick layer of TiC was grown using a combined PLD and magnetron sputtering technique prior to the PLD DLC.1,2 The gases were 100%Ar, 100%Ne, 75%Ar-25%O2, and 75%Ne-25%O2. Using the Tripod Polisher, the samples were polished flat using typical conditions and the surfaces examined by atomic force microscopy and compared. TEM samples prepared by single-sided dimpling prior to ion milling were prepared using the gas composition which gave the best results with respect to the AFM. A methodology is established for determining ion milling conditions for samples having layers of different compositions.
Cross-Sectional Tem Sample Preparation Method Using Fib Etching for Thin-Film Transistor
Authors: Tsujimoto K. , Tsuji S. , Takatsuji H. , Kuroda K. , Saka H. , Miura N.
Published: April 2011

A rapid and precise sample preparation method using focused ion beam (FIB) etching was developed for cross-sectional transmission electron microscopy (X-TEM) analysis of a thin-film transistor (TFT) fabricated on a glass substrate. Gallium (Ga) ions accelerated at 30 kV and at various incident beam angles were applied during FIB etching to create a uniform thin wall. We successfully prepared X-TEM specimens of long and fragile aluminum (Al) whiskers formed on thin Al films in TFT metallization, where a strong charge is built up during FIB etching. The effect of ion-beam-assisted tungsten deposition prior to FIB etching is discussed. A whisker having a length not exceeding approximately 10 #x00B5;m can be successfully etched to a thickness of 200 nm while keeping its original shape. The performance of this technique is demonstrated in applications to etching at other fragile locations related to TFTs.
Cross sectional Tem Sample Preparation Using E-Beam Lithography and Reactive ion Etching
Authors: Cho Hyun-Jin , Griffin Peter B. , Plummer James D.
Published: April 2011

A simple method to make cross sectional TEM samples of Si and GaAs semiconductor devices at specific device locations using electron beam (e-beam) lithography and reactive ion etching is described. The basic idea of this technique is to form pillar or line type patterns thin enough to be transparent to electron beams used in transmission electron microscopy. Since the entire process is conducted in the semiconductor fabrication facility, reliable samples were efficiently obtained within a short time without mechanical polishing or ion milling. High Resolution Electron Microscopy (HREM) images of SiGe and GaAs multilayer structures were obtained by this method. Using the alignment function of the e-beam lithography system, cross sectional TEM samples at specific locations of MOS transistors were obtained. The samples were thin enough to obtain HREM images of atomic level defects in the device.
Transmission Electron Microscopy Specimen Preparation of Ceramic Coatings on Ceramic Fibers
Authors: Cinibulk M. K. , Welch J. R. , Hay R. S.
Published: April 2011

A method of preparing transmission electron microscopy (TEM) specimens of coated ceramic fibers has been developed that produces large areas containing many electron transparent fibers, due to the minimal preferential milling of the epoxy matrix. Multiple individual fibers or tows are impregnated with a high-temperature epoxy and contained to assure a high fiber-to-epoxy volume ratio. The samples are then sectioned and mechanically thinned either parallel or normal to the fiber axes using a wedge polisher on diamond lapping films to achieve a thickness of less than 5 μm. The thinned sample is then ion-milled to electron transparency in less than 30 min, giving representative specimens of the coating, fiber, and coating-fiber interface. This technique is also well suited to preparing extremely flat specimens for both light microscopy and scanning electron microscopy analysis of thin coatings.
Two-View Small-Angle Wedge Sample Preparation By Hand Tools For Transmission Electron Microscopy Of Semiconductors And Related Materials
Authors: Suder Suli , Faunce C. A. , Donnelly S. E.
Published: April 2011

Various small-angle wedge two-view samples have been prepared by a small-angle cleavage technique using hand tools and examined by transmission electron microscopy. Cleaved wedges from the same material are mounted both as plan-view and cross-sectional samples on the same TEM specimen grid allowing convenient examination in both views. Samples of Si3N4, Zr, Co and TiN/CN/TiN films deposited on Si, and He ion implanted Si prepared by this technique are shown to be suitable for analysis in the TEM.
Two-Dimensional Profiling of Dopants in Semiconductor Devices Using Preferential Etching/Tem Method
Authors: Kimura H. , Shimizu K.
Published: April 2011

We present a sample preparation technique for using transmission electron microscopy (TEM) to profile the dopant in a specified doped region of a very large scale integrated (VLSI) devices. This technique is based on preferential etching of the doped region in silicon. Because the rate at which silicon is etched depends on the dopant concentration, the dopant distribution can be inferred by observing the thickness fringe. Using two-beam approximation and information on the dependence of the etching rate on the concentration, we calculated the intensity of the transmitted electron beam and found that the results agreed well with the observed fringes. In addition, by using a focused ion beam (FIB), we could also observe the dopant distribution in a specified source region of a VLSI device.
Xtem Sample Preparation for Failure Analysis in Semiconductor Devices Using High Energy Ion Beam Thinning
Authors: Bugiel E.
Published: April 2011

XTEM investigations are an important tool to characterize the geometry, structure and microchemical composition of semiconductor devices. Over the last 25 years, several thinning procedures have been used, based on Ar ions at about 5 kV. Common to all of them is that the thinning takes several hours, or the ion thinning has to be combined with awkward mechanical preparation steps, like dimpling.

The technique described below uses Ar ions up to 15 keV and with a total ion current of up to 0.2 mA. A maximum sputtering rate of 25 μm/h for Si is reached at an incidence angle of 6°. A low energy thinning step at 3.5 keV is used at the end to reduce the amorphization and heating of the thinnest regions. The combination of this fast ion thinning with simpler mechanical steps requiring only a final lapping step, without the need for dimpling and polishing, results in a yield of nearly 100% and a preparation time of about 3h.
Correlation Functions for Nanostructures Obtained by Nucleation and Growth Kinetics
Authors: Crespo D. , Garrido V.
Published: April 2011

Most of the physical properties of systems underlying first order phase transitions, I. e. the scattering properties, can be obtained from the spatial correlation functions. For the case of nucleation and growth kinetics it is possible to obtain all the correlation functions from the particle size distribution. In this paper we obtain the spatial correlation functions corresponding to several kinetics; in particular the correlation functions corresponding to the microstructure developed in partitioning transformations are obtained.
Evolution of γ′ Precipitation Kinetics and Morphology in a Ni- 13.36 at.% Al Alloy Aged Under Compression
Authors: Prikhodko S. V. , Nielsen R. T. , Ardell A. J.
Published: April 2011

The influence of an applied uniaxial compressive stress on the coarsening of γ′ (Ni3A1) precipitates at 640°C in a Ni-13.36 at. % Al alloy was studied experimentally. The investigation was done using cylindrical doubly-tapered monocrystalline specimens with axes of revolution parallel to [100]. At an applied load of 940 N the compressive stress varied from ∼30 to ∼130 MPa in any given specimen. Over this range of stresses the strain was primarily elastic. Dark-field transmission electron microscopy, coupled with image-analysis software, was used to characterize evolution of the γ′ precipitate morphology, and the kinetics of coarsening in (100) were investigated for aging times up to 504 h. We find, quite unexpectedly, that the relationship between the kinetics of coarsening and the applied stress is not monotonic. Instead, a maximum in the coarsening rate obtains at an intermediate stress, in the neighborhood of 55 ± 10 MPa. Theoretical work by Johnson predicts that for certain combinations of lattice and elastic-constant mismatch, an extremum of the solubility limit exists in elastically isotropic specimens aged under uniaxial stress. The theory is not sophisticated enough to enable a quantitative comparison with experimental results, but provides some rationale for our unexpected finding.
Vacancy Properties In 5d Bcc Transition Metals: Ab Initio Study At Finite Electron Temperature
Authors: Satta Alessandra , Willaimel F. , de Gironcoli Stefano
Published: April 2011

The self-diffusion constants for the monovacancy mechanism in the 5d transition-metals with bcc structure (β-Hf, Ta and W) are investigated by first-principles pseudopotential calculations within the framework of the Local Density Functional Theory. The formation and migration energies, calculated for relaxed configurations using supercells containing 27 and 54 atomic sites, are in quite good agreement with experimental data in Ta and W, with a discrepancy lower than 10 %. Preliminary results in β-Hf using smaller supercells suggest very large relaxation energies. The effect of finite electron-temperature is shown to be quite important, and very different from one element to the other: the electron contribution to the activation entropy is negative in Ta and positive in W, reaching respectively −2 kB and 2 kB at the melting temperature. Using simple estimates for the attempt frequencies and the vibrational formation entropies, the calculated self-diffusion coefficient is in exceptional agreement with experiments in W, and clearly reproduces an accelerated diffusivity in Ta.
Evolution of γ′ Precipitate in in-713C for Long Aging Treatments
Authors: Ges A. , Fornaro O. , Palacio H.
Published: April 2011

The strength of nickel-base superalloys hardened through precipitation is related to the volume fraction, particle size and distribution of the precipitate phase γ′: Ni3(Al,Ti). Such particles grow during the initial heat treatment and for long aging times, and it is very important to predict the kinetics growth owing to its technological application at high temperatures. In this work, we performed the analysis of the particle coarsening in IN-713C during long aging times at constant temperature (T=1223K), given an initial size, the volume fraction distribution of the γ′ precipitate phase, the evaluation of two different heat treatments through the microstructure analysis and γ′ morphology and tensile properties between 873–1123K. We found that for short aging times, t < 9×106s, the coarsening can be approximated by a linear volumetric growth as predicted by LSW theory. For a time greater than 9×106s the growth rate of γ′ precipitate shows an asymptotic behavior in both heat treatments.
The L12 to DO19 Phase Transformation In The Intermetallic Compound Fe3Ge
Authors: Chen Q. Z. , Ngan A. H. W. , Duggan B. J.
Published: April 2011

A large kinetics hysteresis is found to exist between the forward and backward reactions of the L12 ↔ DO19 transformation in Fe3Ge. The slow DO19 to L12 transformation leaves behind very stable twins and stacking fault debris. In-situ annealing experiments in the transmission electron microscope revealed that nucleation for the reverse L12 to DO19 reaction takes place efficiently at these defects.
AC Field Induced Polarization Disordering in The Ferroelectric Phase Of Modified Pzt Ceramics
Authors: Tan Q. , Viehland D.
Published: April 2011

Pronounced nonlinear enhancements in dielectric responses and decreases in phase transformation temperatures were induced under moderate ac fields and high field cycling for La modified lead zirconate titanate (PZT) ceramics. Polarization disordering could be inhibited by introducing acceptor dopants into La modified PZT compositions and by DC bias field. Analysis of the frequency dispersion revealed that the field driven transformation in lower La content PZT is a field assisted activation process, while the transformation in higher La content PZT relaxors is intrinsically a thermal activated process.
Effect of Phase Transformations on Hardness of Semiconductors
Authors: Galanov B. A. , Grigor'ev O. N. , Gogotsi Y. G.
Published: April 2011

Models that describe hardness of materials do not account for stress-induced phase transformations that occur under sharp indenters. However, experimental work shows that some materials can be transformed under the indenter into new, high-pressure phases with properties that differ significantly from those of the pristine material. In particular, semiconductors (Si, Ge and other) experience Herzfeld-Mott transition (metallization). Significant volume changes can accompany these transformations. In the present paper, Tanaka's model [1] has been modified to account for reversible phase transformations under contact loading.
Strained Ion Tracks in Amorphous Solids: Origin of Plastic Deformation
Authors: Trinkaus H. , Schober H. R.
Published: April 2011

Track formation in amorphous solids is treated in terms of viscoelastic shear stress relaxation in thermal spike regions which is followed by the freezing-in of the associated strain increment. The resulting strained tracks are considered to be the mesoscopic defects responsible for anisotropic creep and growth. A recently presented approximate quantitative approach to the problem is reviewed. In addition, a new set of constitutive equations describing the viscous flow in thermal spike regions is suggested and general solutions are discussed.
Disordering in the Ni-Al system under low dose ion-irradiation: a computer simulation study
Authors: Almazouzi A. , Alurralde M. , Spaczer M. , Victoria M.
Published: April 2011

Starting from the radiation damage cascades, as obtained using the binary collision approximation, we derive the spatial distribution of the energy deposited into the lattice by the primary knock-on atom (PKA). We follow the time evolution of the cascade core in two ordered intermetallics Ni3Al and NiAl, using the molecular dynamics (MD) method with the embedded potential and with the liquid droplet model (LDM) in which a simplified version of the heat equation is solved. Moreover, the MD was used to determine the evolution of the local structure and to identify the disordered zones. The LDM allows us, after a calibration with MD results, to estimate the dependence of the molten volume on the PKA energy up to 1 MeV. The results show good agreement with other published simulations and the available transmission electron microscopy (TEM) observation experiments.
Phase Transitions During Ion-Beam Irradiation of the Perovskite-structure Oxides
Authors: Meldrum A. , Boatner L. A. , Ewingt R. C.
Published: April 2011

Several perovskite-structure oxide compounds, including CaTiO3, SrTiO3, BaTiO3, KNbO3, and KTaO3 were irradiated by 800 keV Kr+ ions in order to investigate and compare their response to heavy-ion irradiation. The critical amorphization temperature Tc, above which amorphization could not be induced, was found to increase in the order SrTiO3 → CaTiO3 → BaTiO3 → KNbO3 → KTaO3. No single physical parameter explains the observed sequence, although Tc correlates well with the melting temperatures. The well-known solid state phase transformations in these materials did not have a significant effect on the dose required for amorphization. Domain boundaries were observed in the pristine samples; however, after only a low dose, the boundaries became poorly defined and, with increasing dose, eventually disappeared. Dislocation loops were observed to aggregate at the domain boundaries.
Radiation Damage of a Glass-Bonded Zeolite Waste Form Using Ion Irradiation
Authors: Storey B. G. , Allen T. R.
Published: April 2011

Glass-bonded zeolite is being considered as a candidate ceramic waste form for storing radioactive isotopes separated from spent nuclear fuel in the electrorefming process. To determine the stability of glass-bonded zeolite under irradiation, transmission electron microscope samples were irradiated using high energy helium, lead, and krypton. The major crystalline phase of the waste form, which retains alkaline and alkaline earth fission products, loses its long range order under both helium and krypton irradiation. The dose at which the long range crystalline structure is lost is about 0.8 dpa for helium and 0.1 dpa for krypton. Because the damage from lead is localized in such a small region of the sample, damage could not be recognized even at a peak damage of 50 dpa. Because the crystalline phase loses its long range structure due to irradiation, the effect on retention capacity needs to be further evaluated.
Temperature Dependence and Annealing Effects of Absorption Edges for Selenium Quantum Dots Formed By Ion Implantation In Silica Glass
Authors: Ueda A. , Wu M. , Mu R. , Tung Y.-S. , Henderson D. O. , Meldrum A. , Zuhr R. A. , Budai J. D. , White C. W. , Keay J. C. , Feldman L. C.
Published: April 2011

We have fabricated Se nanoparticles in silica substrates by ion implantation followed by thermal annealing up to 1000°C, and studied the Se nanoparticle formation by optical absorption spectroscopy, Rutherford backscattering spectrometry, X-ray diffraction, and transmission electron microscopy. The sample with the highest dose (1 × 1017 ions/cm2 ) showed the naonparticle formation during the ion implantation, while the lower dose samples (1 and 3 × 1016 ions/cm2) required thermal treatment to obtain nano-sized particles. The Se nanoparticles in silica were found to be amorphous. After thermal annealing, the particle sizes became larger than the exciton Bohr radius for bulk Se. Thus, the absorption edges for different doses approached the value of bulk after thermal annealing. The temperature dependent absorption spectra were also measured for this system in a temperature range from 15 to 300 K.
Initial Phase Formation During Interdiffusion
Authors: Perepezko J. H. , Park J. S. , Landry K. , Sieber H. , Bassani M. H. da Silva , Edelstein A. S.
Published: April 2011

In multiphase materials systems involved in coatings, composites or multilayered structures, diffusion treatments often results in the development of intermediate phases at the reaction interfaces. While diffusional growth of phases has received much attention, the initial phase evolution involves a nucleation stage as well. The development of metastable phases during solid state interdiffusion demonstrates that the nucleation reaction can be controlling in some cases. For alloy systems with extensive solubility, intermediate phase nucleation is proceeded by interdiffusional mixing in order to achieve the required supersaturation. This leads to the identification of a critical concentration gradient for the onset of phase nucleation.The concentration gradient and the relative magnitudes of the component diffusivities provide a basis for a phase selection strategy and the application of a kinetic bias to modify the phase selection. For multicomponent alloy systems, the identification of the operative diffusion pathway is central to the control of phase formation. Experimental access to the nucleation stage of reaction is facilitated in thin film multilayer samples where the results from systems with both extensive and limited solubility offer new insight into the phase formation kinetics.
Interface Morphological Stability of Unidirectionally Solidified RE123 Superconductor
Authors: Sumida M. , Shiohara Y. , Umeda T.
Published: April 2011

A simple model is proposed to analyze the interface stability of the RE123 superconductor in accordance with the constitutional supercooling criterion. As the single crystal growth of the 123 phase is largely dependent on the growth interface stability, a quantitative analysis has been required. From the numerical analysis for the case of peritectically solidified Sm123, it was clarified that the constitutional supercooling must exist in the liquid when the 123 growth interface comes close to a 211 particle. It could also predict that larger 211 particle radius, smaller volume fraction of the 211 particles, larger growth rate, or smaller imposed temperature gradient cause easy occurrence of the constitutional supercooling. The growth rate and a 211 particle radius are determining parameters. Further consideration of the nucleation at the L/211 interface just ahead of the 123 growth front could describe the 123 growth morphological transition from with the planar interface to the equiaxed blocky.
Interface Diffusion in Polysynthetically-Twinned Tiai
Authors: Luzzi D. E. , Imamura D. , Inui H. , George E. P. , Heatherly L. , Yasuda H. , Mori H. , Yamaguchi M.
Published: April 2011

The utility of polysynthetically-twinned (PST) TiAI, which contains a high density of parallel, atomically-flat interfaces within a set of identical crystallographic orientations, as a potential model system for a detailed investigation of interface diffusion is explored. Macroscopic PST crystals were grown in an optical float zone furnace. Thin films were cut from oriented crystals and polished with <112> directions normal to the film. After sputter cleaning, Ag was deposited on one side of the TiAI thin films. Auger spectra were obtained from these films over a wide range of sputter/anneal conditions. The Al and Ti concentrations were analyzed as well as the important impurity elements, S, Ar, C, N and O. Using the present data and existing knowledge of the microstructure and crystallography of PST TiAI, the potential of this material for providing a detailed understanding of the atomistic mechanisms of interface diffusion is analyzed.
Derivation of the Kinetics of Phase Transformations with Nucleation and Growth Mechanism
Authors: Yu G. , Lee S. T. , Lai J. K. L.
Published: April 2011

The kinetics of phase transformation which follows a nucleation-and-growth mechanism was studied by using probability theory. From the calculation of the survival probability for each individual site, the general equation for describing the transformation kinetics, in which the nucleation and growth rates are considered as a function of time and space, is derived. In comparison to the classical derivation by Avrami, the new derivation is logical and transparent. The extension of the treatment by using the definition of the multiple-survival probability leads to the exact solutions of the time dependent grain size distribution functions during transformation. A new understanding of fundamental relationships for the microstructural analysis can be achieved by comparing different kinds of size distribution functions. By applying the principles of the analytical treatment to the simulation, model systems of vast size can be handled for very complicated transformation process.
Lattice Location and Luminescence Behavior of Rare Earth Elements Implanted in GaN
Authors: Dalmer M. , Restle M. , Stötzler A. , Vetter U. , Hofsäss H. , Bremser M. D. , Ronning C. , Davis R. F. ,   Isolde
Published: April 2011

Single crystalline GaN-layers were implanted with radioactive 167Tm and 169yb ions, and their lattice sites were determined using the emission channeling technique. After the decay of 167Tm to 167Er, photoluminescence studies were performed. Upon room temperature implantation, rare earth atoms immediately occupy relaxed substitutional sites with an average relaxation of about 0.025 nm. Isochronal annealing treatments up to 800 °C and co-implantation of oxygen to a dose an order of magnitude greater than that of the Tm or Yb do not influence the rare earth lattice sites. A variety of different rare earth related luminescence lines are observed, and co-implantation of oxygen strongly changes the line intensities.
Characterizations of Mg Implanted GaN
Authors: Chi Gou-Chung , Pong B. J. , Pan C. J. , Teng Y. C. , Lee C. H.
Published: April 2011

With 150KeV Mg+ ion implantation, the optical and structural characteristics of GaN films were studied. Post-implant annealing up to 1000°C was performed in N2 ambient with a rapid thermal annealing (RTA) system, without an encapsulation layer. We observed a green band photoluminescence from Mg-implanted GaN. This green band photoluminescence should be associated with Mg induced defect-clustering in GaN. We also use the x-ray diffraction method to study the correlation between structure defects and implantation. We observed an extra shoulder peak at the small angle side of the GaN[0004] diffraction peak. The origin of this shoulder may be attributed to implanted magnesium induced GaN lattice strain.