bluuebunny/crossref_metadata_2025_split huggingface dataset:
A survey of new electron-optical materials characterisation techniques
Authors: Spence J.C.H. 
Published: June 2020

It is rare that the detection of a new signal from a solid-state system does not in time prove useful for materials characterisation. At the same time, the increasing number of detectors fitted to modem electron microscopes, their improved probe-forming capabilities and vacuum performance and the trend toward full digital control and data aquisition, together with the use of more self-explanatory human interfaces in software has greatly increased the number of useful signals and their combinations, making the modem electron microscope an extraordinarily powerful and versatile instrument for materials characterisation. We list below some of the more promising new ways in which the signals available from modem TEM/STEM and SEM instruments may be used in materials science.1. Backscattered channelling imaging. By detecting elastically back-scattered electrons using an energy filter, striking diffraction contrast images of line and planar defects may be obtained from bulk samples. A field-emission SEM instrument is required for this work, operating at about 50 kV.The spatial resolution achieved is about 10 nm, the images come from a depth of less than about 100 nm, and atomically clean surfaces are not required.
TEM Z-contrast imaging with wide-angle hollow-cone illumination
Authors: Bentley J. , Alexander K. B. , Wang Z. L. 
Published: June 2020

High resolution scanning transmission electron microscopy (STEM) images with contrast sensitive to atomic number (Z-contrast) have been obtained with the use of a high-angle annular detector. The equivalent conventional transmission electron microscopy (TEM) dark-field mode reciprocally related to Z-contrast STEM is wide-angle hollow-cone illumination with an on-axis objective aperture. There are two ways to obtain hollow cone illumination; with an annular condenser aperture or by conically scanning the beam tilt coils. As in the case of STEM Z-contrast imaging, resolution with hollow-cone illumination should theoretically be higher than for phase contrast imaging in the same instrument.Philips CM30/STEM, CM12/STEM, and EM400T/FEG/STEM instruments have been used to investigate this imaging technique. The conical illumination dark-field mode is standard on the CM series and was implemented with a hybrid diffraction unit on the EM400. Commercial (SPI Supplies #1780) copper annular apertures with inner and outer diameters of 600 and 900 μm, respectively, spot welded to suitable supports for use as condenser apertures, resulted in cone angles too small to give good Z-contrast in the microprobe mode, because there is still a large diffraction contrast contribution.
A new approach to study diffuse scattering
Authors: Zhu Yimei , Suenaga M. , Sabatini R.L. 
Published: June 2020

A new approach combining high resolution electron microscopy with computer imaging techniques is used to study streaking of electron diffuse scattering. It was found that this newly developed technique has many merits for studying modulated structures. It can form images directly from the weak diffuse scattering intensity representing a small area on the order of several nm and with less double diffraction effect as compared with the selected area diffraction (SAD). The diffractogram produced has no artifacts from a hard aperture and can show much more detail as compared with the optical diffraction technique.This technique is based on analyzing a HREM image intensity. Fig. 1 is an example of study involving tweed structure, which exhibits a roughly periodic cross-hatched contrast in morphology associated with streaks in diffraction in Fe doped YBa2Cu3O7 [see inset of Fig. 1(a)]. Since the streak is short and its intensity is weak, it is not possible to form a dark-field image from the streak in an electron microscope. Nevertheless, with this new technique, we can form an image by Fourier transforming the streak. Shown in Fig. 1(a) is a digitized image from a HREM micrograph negative using an Eikomix camera and the SEMPER program. The digitized image was then Fourier-transformed to form a diffractogram. By placing small windows around all fundamental spots including all streaks, a subsequent inverse transformation strongly suppressed the non-periodic noise in the image.
Imaging with plasmon energy loss electrons
Authors: Xiaofeng Duan , Anyan Du , Chu Y. M. 
Published: June 2020

Collision of electron with the specimen in electron microscope are either elastic or inelastic. There are mainly two types of characteristic energy loss: the plasmon energy loss and the inner shell ionization loss. In metals and semiconductors the plasmon energy loss Ep is proportional to , where Nf is the number of free electrons in unit volume. Normally Ep is 10 - 20 eV and the plasmon peak in EELS is well defined. In insulators, the plasmon peak usually has a broad maximum in the range 20-30eV. If the separation of plasmon peaks of species in a multi-phase sample is large enough, they can be distinguished by means of energy filtered imaging technique. In this paper we report two examples to illustrate the ability of this method in material science. The machine used is a TEM Opton CEM 902 at 80 kV.The first example is a-Si:H/C:H superlattice sample. Fig. 1a shows the CTEM image. Fig. 1b and 1c show the inelastic images. The energy window are set at about the plasmon energy loss of Si( E = 16 eV) and a-carbon( E=26 eV respectively. In Fig.1b the bright strips are a-Si layers.
Diffraction contrast of dislocations in icosahedral quasicrystals
Authors: Urban K. , Zhang Z. , Wollgarten M. , Gratias D. 
Published: June 2020

Recently dislocations have been observed by electron microscopy in the icosahedral quasicrystalline (IQ) phase of Al65Cu20Fe15. These dislocations exhibit diffraction contrast similar to that known for dislocations in conventional crystals. The contrast becomes extinct for certain diffraction vectors g. In the following the basis of electron diffraction contrast of dislocations in the IQ phase is described. Taking account of the six-dimensional nature of the Burgers vector a “strong” and a “weak” extinction condition are found.Dislocations in quasicrystals canot be described on the basis of simple shear or insertion of a lattice plane only. In order to achieve a complete characterization of these dislocations it is advantageous to make use of the one to one correspondence of the lattice geometry in our three-dimensional space (R3) and that in the six-dimensional reference space (R6) where full periodicity is recovered . Therefore the contrast extinction condition has to be written as gpbp + gobo = 0 (1). The diffraction vector g and the Burgers vector b decompose into two vectors gp, bp and go, bo in, respectively, the physical and the orthogonal three-dimensional sub-spaces of R6.
Characterization of the inverted tetrahedral twin particles in the heteroepitaxial KNbO3 thin films
Authors: Rou Shang H. , Hren John J. , Hren Philip D. , Graettingcr Thomas M. , Ameen Michael S. , Aucicllo Orlando , Kingon Angus I. 
Published: June 2020

Perovskite potassium niobate (KNbO3) possesses good electrooptic properties for modulated channel waveguide applications, Epitaxial KNbO3 thin films were deposited onto (100) MgO substrates using an ion beam sputtering technique equipped with a novel computer-controlled rotating target holder , Conventional transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM) were employed to perform defect structure and microstructure analysis. Special TEM sample preparation procedures have been developed, which will be reported elsewhere, Tetrahedral twin particles (TTP's) were observed in the epitaxial KNbO3 thin films. Since, the orientation difference between the TTP's and the matrix may affect the polarization switching properties, it is essential to understand their origin and eliminate them if possible.A selected area diffraction pattern of a KNbO3 thin film taken along the substrate (012) (figure 1) reveals twin and double diffraction spots. The mirror planes are determined to be of the {211} family. Figure 2(a) shows the electron diffraction pattern taken along the substrate (100). Twin spots coincide with some of the matrix spots indicating that the twin also maintains an epitaxial relationship with the MgO substrate. The orientation relationship between the twins and the matrix is [221]twin//[100]matrix.
A study on sink strength of dislocations through analyses of loop formation process under defect concentration gradient
Authors: Nakai Kiyomichi , Kinoshita Chiken 
Published: June 2020

The behavior of point defects around sinks has been greatly investigated for evaluating their bias effects on void formation and swelling. It is, however, laborious to estimate sink strength connected with the bias, because it depends greatly on the sink character. In the present paper the sink strength for interstitials is confirmed through analyses of nucleation and growth process of dislocation loops around characterized dislocations under electron irradiation.A Nb-40.0wt.%Zr alloy having the interface between bcc structures of βNb and βZr phases was irradiated with 1MeV electrons in the JEM-1000 high-voltage electron microscope at the HVEM Laboratory, Kyushu University.The orientation relationship between βNb and βZr phases follows the cube/cube, and the interfaces are. The interface dislocations run parallel to [111] and at a regular interval and respectively have Burgers vectors of b = 1/2 and 1/2[111]. Misfit between the phases as well as distance between interface dislocations are also confirmed by dark-field microscopy, trace analysis and electron diffraction.
On the interpretation of dislocation-loop growth during in-situ high-voltage Electron Microscopy
Authors: Holzäpfel E. , Phillipp F. , Wilkens M. 
Published: June 2020

During in-situ radiation damage experiments aiming on the investigation of vacancy-migration properties interstitial-type dislocation loops are used as probes monitoring the development of the point defect concentrations. The temperature dependence of the loop-growth rate v is analyzed in terms of reaction-rate theory yielding information on the vacancy migration enthalpy. The relation between v and the point-defect production rate P provides a critical test of such a treatment since it is sensitive to the defect reactions which are dominant. If mutual recombination of vacancies and interstitials is the dominant reaction, vαP0.5 holds. If, however, annihilation of the defects at unsaturable sinks determines the concentrations, a linear relationship vαP is expected.Detailed studies in pure bcc-metals yielded vαPx with 0.7≾×≾1.0 showing that besides recombination of vacancies and interstitials annihilation at sinks plays an important role in the concentration development which has properly to be incorporated into the rate equations.
Effects of krypton ion irradiation on the structure and morphology of germanium — An in situ TEM study
Authors: Wang L.M. , Birtcher R.C. 
Published: June 2020

Although it was initially thought that irradiation could not further damage an amorphous material, an anomalous ion-induced morphological instability on the surface of amorphous Ge has been reported previously by several authors. In this study, the structural and morphological changes of Ge were monitored during 1.5 MeV Kr ion irradiation by in situ TEM to obtain insight into the damage evolution in ion-irradiated Ge.The in situ study was performed on the HVEM-Tandem Accelerator Facility at Argonne National Laboratory. The facility consists of a modified Kratos/AEI EM7 high voltage electron microscope (HVEM) and a 2 MV tandem ion accelerator. The samples were jet-polished polycrystalline Ge (99.99999 at. % pure) TEM discs with grain size > 5 μm in dimension. The Kr ion irradiation was carried out at room temperature, and the electron energy of the HVEM was 300 kV. According to a TRIM computer simulation, over 99% of the Kr ions penetrate through the electron transparent areas of the Ge sample, and a dose of 1×1015 Kr/cm2 created an average of ∽4 displacements per atom and an average Kr concentration of ∽12 appm in the observation region of the sample.
Dynamic observation of dislocation generation in rapidly solidified titanium - 4 wt% cerium
Authors: Wittig J.E. 
Published: June 2020

Dynamic observation of dislocation generation and/or motion in the transmission electron microscope is possible for a variety of experimental conditions. In situ straining and heating experiments are traditional methods for observing dislocation interactions caused by deformation, phase transformations, and large differences in thermal expansion coefficients (e.g. metal matrix composites). In addition to external stimuli, the electron beam can also influence defect formation and movement. High voltage electron irradiation has become a standard technique to simulate radiation damage, and for the special case of CdTe, electron beam induced heating has been used to record movement of partial dislocations at lattice resolution.In the current study, the interaction of 200 kV electrons with Ce rich precipitates has been observed to induce dislocation generation and movement in Ti-4wt%Ce alloys. The microstructural condition required for this observation has only been achieved by rapid solidification of an undercooled liquid.
An environmental cell Transmission Electron Microscope
Authors: Dewald D.K. , Lee T.C. , Eades J.A. , Robertson I.M. , Bimbaum H.K. 
Published: June 2020

The ability to observe directly and at high spatial resolution the interactions between environments and materials affords the material scientist new and unique opportunities. This capability is realized in the Environmental Cell Transmission Electron Microscope Facility which has been installed as part of the Center for Microanalysis of Materials at the Materials Research Laboratory of the University of Illinois at Urbana-Champaign.The Facility is based on a JEOL 4000EX equipped with a specially designed pole piece. An aperture limited, differentially pumped, environmental cell has been installed in this pole piece. The system is shown schematically in Figures 1 and 2. Figure 1 is a plan view of a section through the objective lens pole-piece, with the microscope axis perpendicular to the plane of the paper, showing the cell enclosing the sample rod, the gas handling system and the location of the magnetically levitated Turbo-Molecular pumps. Figure 2 shows a cross-sectional view of the environmental cell and the gas handling system. As shown in Figure 2 the electron beam passes through a series of five apertures which allow the column vacuum to be maintained while the cell pressure is increased. The actual cell apertures are located at the apex of cones to minimize the gas path length, allow maximum tilt and still permit high- angle diffraction data to be obtained. Differential pumping of the cell is achieved by the four turbo- molecular pumps, the location of which can be seen in the Figures. With this arrangement the environmental cell is capable of supporting 400 torr of N2 gas which has no noticeable effect on the microscope operation. This allows the microscope to be operated with a LaB6 filament. The gas handling system was designed to handle a variety of environments including corrosive ones.
Surface nucleated half-loops in strained epilayers
Authors: Kvam Eric P. 
Published: June 2020

Mismatched epilayers, grown beyond some critical thickness, have commonly been observed to have arrays of misfit-relieving dislocations at the heterointerface. In diamond or sphalerite structures, these arrays are orthogonal <110> networks of long 60° type dislocations, which are glissile and have inclined Burgers vectors. Up to the point at which growth becomes three-dimensional (about 2% mismatch in the (In,Ga)As/GaAs system), internal defects act as the sources for the misfit dislocations. Examples of such sources include pre-existing threading dislocations, internal loops, precipitates, and mechanical damage.In higher mismatch two-dimensional growth, such as can be produced in the GeSi/Si(001) system, the density of epithreading dislocations suddenly increases as the length of interfacial misfit dislocations falls. Almost simultaneously, the misfit dislocation type changes from 60° to edge. While in-situ hot stage experiments have shown that 60° type dislocations become mobile at about the growth temperature of the epilayer, and have observable velocities from this temperature on up, our observations of edge dislocations in the same system have shown that velocities for edge dislocations are essentially nil (measurable limit <lnm/s) even at 750°C, some 200°C above the growth temperature.
Anisotropy of interfacial defects in the initial stage of MOVPE GaAs growth On Si
Authors: Vannuffel C. , Schiller C. , Chevalier J. P. 
Published: June 2020

Recently, interest has focused on the epitaxy of GaAs on Si as a promising material for electronic applications, potentially for integration of optoelectronic devices on silicon wafers. The essential problem concerns the 4% misfit between the two materials, and this must be accommodated by a network of interfacial dislocations with the lowest number of threading dislocations. It is thus important to understand the detailed mechanism of the formation of this network, in order to eventually reduce the dislocation density at the top of the layers.MOVPE growth is carried out on slightly misoriented, (3.5°) from (001) towards , Si substrates. Here we report on the effect of this misorientation on the interfacial defects, at a very early stage of growth. Only the first stage, of the well-known two step growth process, is thus considered. Previously, we showed that full substrate coverage occured for GaAs thicknesses of 5 nm in contrast to MBE growth, where substantially greater thicknesses are required.
Scanning-DLTS and TEM-investigations in Lec-GaAs: New arguments on the EL2-generation mechanism
Authors: Breitenstein O. , Fornari R. , Frigeri C. , Gleichmann R. , Heydenreich J. 
Published: June 2020

Scanning-DLTS (SDLTS) uses the focused electron beam of a SEM to locally excite deep levels in semiconductor space charge structures (Schottky-diodes or pn-junctions). This results in rf-capacitance changes of the sample, which are detected as a function of temperature by a specialized high-sensitive DLTS-spectrometer leading to a measure of the local concentration of energetically well-defined deep level defects. The detection limit of this technique, hitherto being around 1013cm-3 for a spatial resolution of a few microns, exceeds that of most of the other microanalytical tools by several orders of magnitude.LEC-GaAs crystals have been grown from melts with a Ga/As-fTaction from varying e.g. from 1.05 at the top to 1.35 at the bottom of the crystals. Thus, the decisive position-dependent parameter of the material was the melt-stoichiometry. TEM-investigations revealed the grown-in dislocations and of perfect (interstitial-type) discolation loops, both being decorated with As-rich precipitates(Fig. 1).
Cross-sectional observation of LSI by high resolution TEM
Authors: Song Minghui , Hashimoto Hatsujiro , Yokota Yasuhiro , Matsukawa Takayuki , Ajika Natsuo , Ogo Ikuo 
Published: June 2020

A high density A mega bits DRAM (dynamic random access memory) which was named as FASIC (folded bit line adaptive side wall isolated capacitor cell) was made and reported in 1986. The cell has been fabricated on P-type Si single crystal substrate as four layers (one poly-Si, two poly-silicides and one Al layer) and has a size of 2.6μm × 4.2μm (one million cells in 2.6mm × 4.2mm).Figure 1 shows a light micrograph of a part of FASIC DRAM 6-inch wafer. The unit chip of the circuit in the wafer which is a square of 15mm × 15mm are shown by a circle A. The region indicated by B is the circuit for testing the memory cells and the ones indicated by C and D have 2M and AM memories in 7.5mm × 5mm and 15mm x 5mm respectively. AA' and BB' show two directions rectangular each other. Figure 2 shows schematically the cross-section along AA' direction, which parallel to bit line (BL). The cross sections of word line (WL), A1 line contact and trench (capacitor) are shown. The word line is vertical to bit line and parallel to BB' direction shown in Figure 1.
Electron Microscopy investigations of buried Si3N4 isolation layers
Authors: Maksimov S.K. , Kukin V.N. 
Published: June 2020

Formation of buried Si3N4 layers obtained by using repeated cycles of implantation and annealing has been investigated. Structure investigations were made with the use of a CM30 Twin electron microscope (whose diaphragm is 0.18 nm-1 ). In HREM studies, axial micrographs in Si reflections of the 000, 111 and 220 types were employed. Two types of samples were used: "plane view" samples and those of a "cross section". Si3N4 precipitates were identified by application of the EELS method on the LN and Lsiedges.N+ - ions were implanted into silicon wafers (of p-type, (001), 10 Ω cm) at a room temperature- The dose pf ions implanted in each cycle was 5.1010 cm-2 . The total dose was 5.1017 cm-2 , The energy of ions - 150 keV, the current density of the ion beam 25 μA/cm-2 . Annealing in the atmosphere of nitrogen was made at 1100° C which lasted 2 hours after the first cycle of implantation; in the other cycles it lasted 0.5 hours at 850° C. After the operation of ion beam synthesis was completed a silicon epitaxial layer 0.8-1 μm thick was grown.
Study on microstructures of As+ implanted Ti-Si bilayers with micro-micro beam technique
Authors: Shao Beiling , Liu Ansheng , Yuan Jianming , Ding Furong 
Published: June 2020

A basic understanding of structures of Ti silicide—Si bilayers formed by ion implantation is of considerable interest because of the increasing application of MOS in VLSI. The aim of the present investigation is to explore the effect of ion implanting conditions on structures in Ti-Si bilayers. Rubloff et al. and Holloway et al. have studied Ti—Si interfaces and suggested that two processes may occur at Ti-Si interfaces, a reaction process other than silicide formation and a grain boundary diffusion process leading to localized silicide formation in the grain boundaries. The reaction processes in Ti—Si bilayers implanted by As+ ions were investigated in this work. An analytical electron microscope (JEOL 2000FX - LINK SYSTEM) with micro—micro beam (MMB) technique was employed.66nm Ti films were deposited onto P type <100> orientated Si substrates with a sputtering system at room temperature and the Ti-Si bilayers were implanted with 250 and 300 KeV and 1016 As+/cm2 respectively.
CBED study of strain in InGaAs/GaAs strained layer superlattices
Authors: Xie Q.H. , Fung K.K. 
Published: June 2020

In this paper, we have studied the strain in InGaAs/GaAs superlattices by using CBED. Some authors have started similar reseach in SLSs and epi-layers. Our samples are grown by MOVCVD on exact [001] GaAs substrates with alternate InGaAs layers and GaAs layers. Plan-viewed specimens are prepared by ion-milling from the back side. All our experiments are carried out in regions without dislocations, which can be considered as free superlattices. Phillips EM 430 is used to take the CBED ZAP at 100kV.Using CBED technique, we obtain distribution of intensity of sidebands in two kinds of SLSs InGaAs(100Å)/GaAs(200Å) (Sample A) and InGaAs(150Å)/GaAs(150Å)(Sample B) all with 6% In content. Intensity of HOLZ lines can be got by kinetic calculation because of large extinction distance of these reflections. ϕg is expressed as folows: