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Journal articles on the topic 'Atom channelling'

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Published: 10 December 2022

Last updated: 28 January 2023

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1

Otten, M. T., and P. R. Buseck. "Zone-axis ALCHEMI for the rapid assessment of site occupancies in garnets." Proceedings, annual meeting, Electron Microscopy Society of America 44 (August 1986): 706–7. http://dx.doi.org/10.1017/s0424820100144905.

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ALCHEMI (Atom Location by CHannelling-Enhanced Microanalysis) is a TEM technique for determining site occupancies in single crystals. The method uses the channelling of incident electrons along specific crystallographic planes. This channelling results in enhanced x-ray emission from the atoms on those planes, thereby providing the required site-occupancy information. ALCHEMI has been applied with success to spinel, olivine and feldspar. For the garnets, which form a large group of important minerals and synthetic compounds, the channelling effect is weaker, and significant results are more difficult to obtain. It was found, however, that the channelling effect is pronounced for low-index zone-axis orientations, yielding a method for assessing site occupancies that is rapid and easy to perform.

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2

Rossouw, Chris. "The Role of Simulation in ALCHEMI." Microscopy and Microanalysis 7, S2 (August 2001): 352–53. http://dx.doi.org/10.1017/s1431927600027835.

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Contrast in zone axis channelling patterns, formed by variations in characteristic X-ray emission rates as an electron beam is scanned in angle, is related to projected sublattice site symmetries of ionized atoms within the unit cell. Whereas overall Brillouin zone geometry is identical to that observed in large angle convergent beam patterns, this incoherent X-ray channelling contrast is related to ADF or BSE contrast by integration over thickness of the signal generated within the specimen. Contrast is thus relatively stable and easily interpretable.1 This is useful in separating the response of dilute atoms from abundant atomic species, since the specific channelling pattern of each atom has its own overall fingerprint. Correlation of patterns formed from Ta-doped TiAl with bright field LACBED is shown in Fig. 1 (clearly Ta occupies Ti sublattice sites). No simulation of channelling contrast is necessary if minority atomic species are distributed over sublattice sites in a way that can be reconstructed from a linear superposition of majority (or host) atom sites that form part of the regular lattice structure. The distribution over sublattice sites may be determined by any one of a variety of analysis methods.2,3

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3

SHINDO, Daisuke. "Atom location by channelling enhanced microanalysis." Nihon Kessho Gakkaishi 29, no. 4 (1987): 301–4. http://dx.doi.org/10.5940/jcrsj.29.301.

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4

Shindo, Daisuke. "Principle and application of ALCHEMI(atom location by channelling enhanced microanalysis)." Bulletin of the Japan Institute of Metals 29, no. 7 (1990): 511–18. http://dx.doi.org/10.2320/materia1962.29.511.

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5

Oxley, M. P., L. J. Allen, and C. J. Rossouw. "Correction terms and approximations for atom location by channelling enhanced microanalysis." Ultramicroscopy 80, no. 2 (October 1999): 109–24. http://dx.doi.org/10.1016/s0304-3991(99)00101-1.

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6

Sarosi, P. M., J. A. Hriljac, and I. P. Jones. "Atom location by channelling-enhanced microanalysis and the ordering of Ti2AlNb." Philosophical Magazine 83, no. 35 (December 2003): 4031–44. http://dx.doi.org/10.1080/14786430310001603472.

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7

Marceau, Ross K. W., Ivan Gutierrez-Urrutia, Michael Herbig, Katie L. Moore, Sergio Lozano-Perez, and Dierk Raabe. "Multi-Scale Correlative Microscopy Investigation of Both Structure and Chemistry of Deformation Twin Bundles in Fe–Mn–C Steel." Microscopy and Microanalysis 19, no. 6 (October 8, 2013): 1581–85. http://dx.doi.org/10.1017/s1431927613013494.

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AbstractA multi-scale investigation of twin bundles in Fe–22Mn–0.6C (wt%) twinning-induced plasticity steel after tensile deformation has been carried out by truly correlative means; using electron channelling contrast imaging combined with electron backscatter diffraction, high-resolution secondary ion mass spectrometry, scanning transmission electron microscopy, and atom probe tomography on the exact same region of interest in the sample. It was revealed that there was no significant segregation of Mn or C to the twin boundary interfaces.

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8

Van Dyck, D. "A Simple Real-Space Channelling Theory for Electron Diffraction and HREM." Proceedings, annual meeting, Electron Microscopy Society of America 48, no. 1 (August 12, 1990): 64–65. http://dx.doi.org/10.1017/s0424820100179075.

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The computation of the many beam dynamical electron diffraction amplitudes or high resolution images can only be done numerically by using rather sophisticated computer programs so that the physical insight in the diffraction progress is often lost. Furthermore, it is not likely that in this way the inverse problem can be solved exactly, i.e. to reconstruct the structure of the object from the knowledge of the wavefunction at its exit face, as is needed for a direct method [1]. For this purpose, analytical expressions for the electron wavefunction in real or reciprocal space are much more useful. However, the analytical expressions available at present are relatively poor approximations of the dynamical scattering which are only valid either for thin objects ((weak) phase object approximation, thick phase object approximation, kinematical theory) or when the number of beams is very limited (2 or 3). Both requirements are usually invalid for HREM of crystals. There is a need for an analytical expression of the dynamical electron wavefunction which applies for many beam diffraction in thicker crystals. It is well known that, when a crystal is viewed along a zone axis, i.e. parallel to the atom columns, the high resolution images often show a one-to-one correspondence with the configuration of columns provided the distance between the columns is large enough and the resolution of the instrument is sufficient. This is for instance the case in ordered alloys with a column structure [2,3]. From this, it can be suggested that, for a crystal viewed along a zone axis with sufficient separation between the columns, the wave function at the exit face does mainly depend on the projected structure, i.e. on the type of atom columns. Hence, the classical picture of electrons traversing the crystal as plane-like waves in the directions of the Bragg beams which historically stems from the X-ray diffraction picture, is in fact misleading.

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9

Oxley, M. P., and L. J. Allen. "ICSC: a program for calculating inelastic scattering cross sections for fast electrons incident on crystals." Journal of Applied Crystallography 36, no. 3 (May 20, 2003): 940–43. http://dx.doi.org/10.1107/s0021889803002875.

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A computer program which calculates inner-shell ionization and backscattering cross sections for fast electrons incident on a crystal is presented. The program calculates the inelastic scattering coefficients for inner-shell ionization, pertinent to electron energy loss spectroscopy and energy dispersive X-ray analysis, using recently presented parameterizations of the atomic scattering factors. Orientation-dependent cross sections, suitable for atom location by channelling enhanced microanalysis, may be calculated. Inelastic scattering coefficients that allow the calculation of orientation-dependent annular dark-field and Rutherford backscattering maps are calculated using an Einstein model. In all cases, absorption due to thermal diffuse scattering, also calculated using an Einstein model, can be included.

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10

Nakata, Y., T. Tadaki, and K. Shimizu. "Determination of the Atom Location of Ni in Cu-Al-Ni Alloys by the Channelling Enhanced Microanalysis Method." Materials Science Forum 56-58 (January 1991): 429–34. http://dx.doi.org/10.4028/www.scientific.net/msf.56-58.429.

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11

Horita, Z., H. Kuninaka, T. Sano, M. Nemoto, and J. C. H. Spence. "Delocalization corrections using a disordered structure for atom location by channelling-enhanced microanalysis in the Ni-Al system." Philosophical Magazine A 67, no. 2 (February 1993): 425–32. http://dx.doi.org/10.1080/01418619308207168.

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12

Tin, S., L. Zhang, A. P. Ofori, and Michael K. Miller. "Atomic Partitioning of Platinum and Ruthenium in Advanced Single Crystal Ni-Based Superalloys." Materials Science Forum 546-549 (May 2007): 1187–94. http://dx.doi.org/10.4028/www.scientific.net/msf.546-549.1187.

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The elemental partitioning characteristics of advanced single crystal Ni-base superalloys containing additions of both Pt and Ru have been investigated using atom probe tomography. Detailed microanalysis revealed Ru additions partitioned preferentially to the disordered matrix, whereas Pt additions tended to partition to the ordered intermetallic γ′ precipitates. The partitioning characteristics of three nominally similar alloys with systematic variations in the levels of Cr, Ru and Pt were investigated. For this particular set of experimental alloys, minor changes in the partitioning characteristics of the constituent elements could be attributed to additions of Cr and Ru. The preferential site occupancy of Pt within the L12 lattice was also statistically quantified with ALCHEMI (atomic site location by channelling enhanced microanalysis). In contrast to the atomic partitioning characteristics of Ru, Pt exhibited a tendency to occupy the Ni sublattice sites in the γ′ structure.

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13

Allen, L. J., and M. P. Oxley. "Teoretical Tools for Practical ALCHEMI." Microscopy and Microanalysis 7, S2 (August 2001): 348–49. http://dx.doi.org/10.1017/s1431927600027811.

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Precisely known atomic scattering factors are essential for accurate atom location by channelling enhanced microanalysis (ALCHEMI) based on inner-shell ionization.1 For ALCHEMI using energy dispersive x-ray analysis (EDX), first principles calculations of ionization cross sections, realistically modeling the “delocalization” of the ionization interaction, give excellent agreement with experiment.2 Such calculations are complex and computationally intensive. Hence, simple analytic forms are often assumed to describe the ionization potential. However such analytic forms require prior knowledge of the “delocalization” of the effective ionization interaction. Such an approach assumes that the precise shape of the ionization potential is not important but that at least the half width at half maximum (HWHM) should be accurately estimated, for example using estimates of the HWHM from root-mean-square impact parameters for ionization. However this is generally not a good approximation3 and we have provided more realistic estimates (Fig. 1).

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14

Nakata, Yoshiyuki, Tsugio Tadaki, and Ken’ichi Shimizu. "Atom Location of the Third Element in Ti–Ni–X Shape Memory Alloys Determined by the Electron Channelling Enhanced Microanalysis." Materials Transactions, JIM 32, no. 7 (1991): 580–86. http://dx.doi.org/10.2320/matertrans1989.32.580.

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15

Al-Khafaji, M. A., D. Cherns, C. J. Rossouw, and D. A. Woolf. "Interface atomic structure determination of an AI(001)/GaAs(001) bicrystal using higher-order Law zone analysis and atom location by channelling-enhanced microanalysis." Philosophical Magazine B 65, no. 3 (March 1992): 385–99. http://dx.doi.org/10.1080/13642819208207639.

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16

Cowley, J. M., and P. A. Crozier. "Surface resonance channelling in scanning reflection electron microscopy." Proceedings, annual meeting, Electron Microscopy Society of America 46 (1988): 692–93. http://dx.doi.org/10.1017/s0424820100105527.

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The phenomena of the channelling of electrons along planes or rows of atoms in the surface layers of crystals has been investigated recently in relation to microdiffraction and RHEED, REM, (reflection electron microscopy) and REELS (reflection electron energy loss spectroscopy) by using a conventional TEM in the reflection mode.The renewed interest in this phenomenon, known for many years, is the evidence from calculations of dynamical diffraction effect at surfaces that the electrons may be channelled along the topmost layers of atoms on a crystal surface and that the RHEED, REM and REELS signals may thus be sensitive to the structure and composition of the surface layer. These techniques may therefore provide a powerful new approach to the study of surfaces in which surface microanalysis and diffraction studies may be combined with nanometer-resolution imaging.An investigation has now been made of the analogous techniques which may be applied to the study of surfaces by use of a scanning transmission electron microscope.

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17

Yagi, Eiichi, Tadao Iwata, Teruo Urai, and Kiyoshi Ogiwara. "Channelling studies on the lattice location of B atoms in graphite." Journal of Nuclear Materials 334, no. 1 (August 2004): 9–12. http://dx.doi.org/10.1016/j.jnucmat.2004.04.321.

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18

Mason, D. R., C. P. Race, M. H. F. Foo, A. P. Horsfield, W. M. C. Foulkes, and A. P. Sutton. "Resonant charging and stopping power of slow channelling atoms in a crystalline metal." New Journal of Physics 14, no. 7 (July 4, 2012): 073009. http://dx.doi.org/10.1088/1367-2630/14/7/073009.

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19

Yagi, Eiichi. "Lattice location study on krypton atoms in aluminium by means of the channelling method." Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms 39, no. 1-4 (March 1989): 68–71. http://dx.doi.org/10.1016/0168-583x(89)90743-x.

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20

Yagi, Eiichi, Shiho Nakamura, Fumihisa Kano, Takane Kobayashi, Kenji Watanabe, Yuh Fukai, and Takehiko Matsumoto. "Hydrogen Trapping by Solute Atoms in Nb — Mo Alloys as Observed by the Channelling Method*." Zeitschrift für Physikalische Chemie 163, Part_1 (January 1989): 201–2. http://dx.doi.org/10.1524/zpch.1989.163.part_1.0201.

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21

Tsai, Feng, Shi-Yao Wang, and John M. Cowley. "Preliminary Study of Domain Boundaries in Barium Titanate with High Angle Annular Dark Field(HAADF) Imaging." Proceedings, annual meeting, Electron Microscopy Society of America 49 (August 1991): 940–41. http://dx.doi.org/10.1017/s0424820100089019.

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BaTiO3 have been studied for years by electron microscopists. Those studies have revealed the existence of 90° and 180° ferroelectric domain boundaries. The high angle annular dark field(HAADF) STEM technique is known to have strong sensitivity to atomic number Z. The signal is generated by the channelling of electrons along rows or planes and high angle scattering(mostly thermal diffuse scattering) from the atoms. Contrast in HAADF images can be given by crystal defects as a result of changes in channeling or changes in the high angle scattering process. This work reports a preliminary study of ferroelectric domain boundaries in BaTiO3 with HAADF imaging and a qualitative discussion of the observed domain wall contrast.

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22

YAGI, Eiichi, Takane KOBAYASHI, Kenji WATANABE, Yuh FUKAI, and Takehiko MATSUMOTO. "Trapping of hydrogen by solute atoms in Nb-Mo alloys as observed by the channelling method." Proceedings of the Japan Academy. Ser. B: Physical and Biological Sciences 65, no. 3 (1989): 38–41. http://dx.doi.org/10.2183/pjab.65.38.

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23

Takasuka, Eiryo, Kenji Kimura, Hiroyasu Kawauchi, and Michi-hiko Mannami. "A method of ion channelling to determine lattice site of atoms on crystal surface exposed to contaminating environment." Surface Science Letters 166, no. 2-3 (February 1986): A45—A46. http://dx.doi.org/10.1016/0167-2584(86)90921-7.

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24

Takasuka, Eiryo, Kenji Kimura, Hiroyasu Kawauchi, and Michi-hiko Mannami. "A method of ion channelling to determine lattice site of atoms on crystal surface exposed to contaminating environment." Surface Science 166, no. 2-3 (February 1986): 327–32. http://dx.doi.org/10.1016/0039-6028(86)90682-5.

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25

Nakata, Yoshiyuki, Tsugio Tadaki, and Ken’ichi Shimizu. "Site Determination of Ni Atoms in Cu–Al–Ni Shape Memory Alloys by Electron Channelling Enhanced Microanalysis." Materials Transactions, JIM 31, no. 7 (1990): 652–58. http://dx.doi.org/10.2320/matertrans1989.31.652.

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26

Shindo, Daisuke, Michio Kikuchi, Makoto Hirabayashi, Shuji Hanada, and Osamu Izumi. "Site Determination of Fe, Co and Cr Atoms Added in Ni₃Al by Electron Channelling Enhanced Microanalysis." Transactions of the Japan Institute of Metals 29, no. 12 (1988): 956–61. http://dx.doi.org/10.2320/matertrans1960.29.956.

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27

Umarov, F. F., A. M. Rasulov, and A. A. Dzhurakhalov. "THE COLLIDING PARTICLES MASS RATIO INFLUENCE ON PECULIARITIES OF LOW-ENERGY ION NEAR-SURFACE IMPLANTATION AT CHANNELING CONDITIONS." «Узбекский физический журнал» 20, no. 4 (July 21, 2018): 265–74. http://dx.doi.org/10.52304/.v20i4.102.

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In the present work the peculiarities of ion implantation and colliding particles mass ratio influence on the ranges, energy loss and profiles of distribution for 1−5 keV P+ ions channelling in Si(110) and SiC(110) at normal incidence, and 1 keV Be+ and Se+ ions in GaAs(100), as well as 5 keV Ar+ and Kr+ on Cu(001) surface at glancing incidence are carried out by computer simulation in binary collision approximation. It is shown that for paraxial part of a beam the main contribution to the total energy loss comes from inelastic ones. It has been established that the energy loss of ions transmitted through thin crystal and depth profile distributions depend on width of the channel and mass ratio of colliding atoms. It was shown that at grazing surface channeling conditions the main peak of the implanted depth distributions is considerably shallow, the range for Se+ ions is shallower and the half-width of profile for these ions is narrow than that for Be+ ions. The results allow one to select the optimum for implanted depth distributions with demanded shape at narrow near-surface area of crystals obtaining.

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28

Kijek, M. M., and D. W. Palmer. "Trapping of Interstitials and Vacancies at Solute Molybdenum Atoms in Iron/(0.3 at % Mo)Studied by the Ion-Channelling/Lattice-Location Technique." Materials Science Forum 15-18 (January 1987): 703–8. http://dx.doi.org/10.4028/www.scientific.net/msf.15-18.703.

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29

Sato, Kaoru. "Channelling Enhanced X-Ray Microanalysis of the Preferred Substitution of Ti, Cr and Co Atoms in Sendust (Fe-9.6wt.%Si-5.5wt.%Al) Alloys." Proceedings, annual meeting, Electron Microscopy Society of America 48, no. 2 (August 12, 1990): 470–71. http://dx.doi.org/10.1017/s0424820100135952.

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Sendust (Fe-9.6wt%Si-5.5wt%Al) is a well-known soft magnetic material. Attempts have been made recently to improve the corrosion resistance of this alloy by adding a fourth and/or a fifth element. Since the excellent magnetic properties of Sendust have been reported to be deeply related to its crystal structure, the DO3 structure, it is of vital importance to determine the crystallographic sites those additional elements occupy. In the present work I will report the results obtained for the site occupation of Ti, Cr and Co in Sendust alloys using the ALCHEMI method.Sendust containing 4.0%Cr, 3.0%Co+0.5%Nb and 2.0%Ti alloys were arc melted, then furnace-cooled from 1250°C. TEM specimens were prepared in a twin jet electropolisher using 5% perchrolic-acetic acid and the final thinning was done using an ion milling machine. The ALCHEMI experiment was performed in a Philips EM420T equipped with an EDAX 9900 system.All the specimens observed exhibited the diffraction spots which are associated with the DO3 structure (Fig. 1).

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30

Heath, D. F., and J. G. Rose. "[14C]bicarbonate fixation into glucose and other metabolites in the liver of the starved rat under halothane anaesthesia. Metabolic channelling of mitochondrial oxaloacetate." Biochemical Journal 227, no. 3 (May 1, 1985): 851–65. http://dx.doi.org/10.1042/bj2270851.

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Previous attempts to account for the labelling in vivo of liver metabolites associated with the citrate cycle and gluconeogenesis have foundered because proper allowance was not made for the heterogeneity of the liver. In the basal state (anaesthetized after 24h starvation) this heterogeneity is minimal, and we show that labelling by [14C]bicarbonate can be interpreted unambiguously. [14C]Bicarbonate was infused to an isotopic steady state, and measurements were made of specific radioactivities of blood bicarbonate, alanine, glycerol and lactate, of liver alanine and lactate, and of individual carbon atoms in blood glucose and liver aspartate, citrate and malate. (Existing methods for several of these measurements were extensively modified.) The results were combined with published rates of gluconeogenesis, uptake of gluconeogenic precursors by the liver, and citrate-cycle flux, all measured under similar conditions, and with estimates of other rates made from published data. To interpret the results, three ancillary measurements were made: the rate of CO2 exchange by phosphoenolpyruvate carboxykinase (PEPCK; EC 4.1.1.32) under conditions that simulated those in vivo; the 14C isotope effect in the pyruvate carboxylase (EC 6.4.1.1) reaction (14C/12C = 0.992 +/- 0.008; S.E.M., n = 8); the ratio of labelling by [2-14C]- to that by [1-14C]-pyruvate of liver glutamate 1.5 min after injection. This ratio, 3.38, is a measure of the disequilibrium in the mitochondria between malate and oxaloacetate. The data were analysed with due regard to experimental variance, uncertainties in values of fluxes measured in vitro, hepatic heterogeneity and renal glucose output. The following conclusions were reached. The results could not be explained if CO2 fixation was confined to pyruvate carboxylase and there was only one, well-mixed, pool of oxaloacetate in the mitochondria. Addition of the other carboxylation reactions, those of PEPCK, isocitrate dehydrogenase (EC 1.1.1.42) and malic enzyme (EC 1.1.1.40), was not enough. Incomplete mixing of mitochondrial oxaloacetate had to be assumed, i.e. that there was metabolic channelling of oxaloacetate formed from pyruvate towards gluconeogenesis. There was some evidence that malate exchange across the mitochondrial membrane might also be channelled, with incomplete mixing with that in the citrate cycle. Calculated rates of exchange of CO2 by PEPCK were in agreement with those measured in vitro, with little or no activation by Fe2+ ions.(ABSTRACT TRUNCATED AT 400 WORDS)

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31

Spence, J. C. H., R. J. Graham, and D. Shindo. "Cold Alchemi: Impurity Atom Site Location and the Temperature Dependance of Dechannelling." MRS Proceedings 62 (1985). http://dx.doi.org/10.1557/proc-62-153.

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ABSTRACTRecent applications of the “Atom Location by Channelling Enhanced Microanalysis” (ALCHEMI) are summarised. This is a quantitative method for determining the sites of impurity atoms in crystals using an electron microscope and X-ray analysis system. Since the fractional site occupancies are given in terms of measured X-ray counts alone, it involves no adjustable parameters. New experiments have been performed on the temperature dependence of characteristic X-ray production under channelling conditions for InP and GaAs. We conclude that low temperatures will give more accurate results for “ALCHEMI” in some materials due to the reduction in diffuse inelastic phonon scattering, and that the study of this temperature dependence may provide new information from small areas or particles on the correlations amongst atom motions due to thermal vibration.

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32

Jagelski, Jacek, L. Thome, and M. Kopcewicz. "Amorphization of Zr/Ni Bilayers by Ion-Beam-Mixing." MRS Proceedings 311 (1993). http://dx.doi.org/10.1557/proc-311-203.

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ABSTRACTThe amorphization process induced by ion-beam-imxing was studied for the Zr/Ni bilayer system by means of the RBS/channelling and CEMS techniques. The number of atoms mixed per one incident atom was found to be the same for σ100 K and 300 K irradiations, whereas it was increased by the factor of 2.5 for 500 K irradiation what indicates, that the change in the mixing mechanism occurred above room temperature. The results show that amorphization of the Zr/Ni system is controlled by the number of mixed atoms and depends on the irradiation temperature. A change in CEMS spectra was observed at σ770 K what suggests that recrystallization of the amorphous phase occurs at this temperature.

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33

"A Channelling Enhanced Microanalysis on Niobium Atom Location in an Al-43%Ti-2%Nb Intermetallic Compound." Journal of Electron Microscopy, 1986. http://dx.doi.org/10.1093/oxfordjournals.jmicro.a050595.

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34

Nejim, A., C. Jeynes, R. P. Webb, Neb Cowern, and C. J. Patel. "Influence of dynamic annealing on the depth distribution of germanium implanted in (100) silicon at elevated temperatures." MRS Proceedings 469 (1997). http://dx.doi.org/10.1557/proc-469-387.

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Abstract(100) silicon wafers were implanted at elevated temperatures up to 600°C with l×lO15-5×1015 Ge+/cm2 using 120 keV. The wafers were tilted by 5–7° and rotated by 5–15°. The implanted germanium profile was monitored as a function of implant temperature using RBS-channelling. Considerable profile broadening was seen together with apparent mass germanium migration away from the surface in samples implanted at 300°C and above. Control implants into hot and cold samples simultaneously rule out excess loss of germanium from the heated wafers. Channelling data indicate that while room temperature implants lead to amorphisation, with hot implants good quality layers are obtained in which the germanium atoms occupy substitutional sites. Hot implants into a sample previously implanted with germanium at room temperature does not lead to any redistribution in the original germanium profile. This result indicates that the apparent enhanced indiffusion of germanium is not a radiation assisted phenomenon and could be explained by a considerable channelling of the implanted germaniumatoms along the <100> direction.

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35

Maydell-Ondrusz, E. A., I. H. Wilson, and K. G. Stephens. "Disptacement of Arsenic from Substitutional Sites in Silicon by MEV HE+ Irradiation." MRS Proceedings 45 (1985). http://dx.doi.org/10.1557/proc-45-123.

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ABSTRACTCross-sections were determined for displacement of arsenic from substitutional sites in silicon by 1.5MeV He+ ions. Results are presented for channelled and random incidence on (111) and (100) silicon, doped by arsenic implantation and annealed by scanning electron beam irradiation. Layers doped during MBE growth were also studied for comparison.Inner L-shell ionisation of host atoms is proposed to explain the observed displacement cross-section and its variation with arsenic concentration. The results are used to indicate the limits for using Rutherford backscattering and channelling techniques to measure the substitutionality of dopants in single crystals.

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36

Cheung, W. Y., S. P. Wong, I. H. Wilson, and T. H. Zhang. "Characterization of GeSi Layer Formed by High Dose Ge Implantation into Si." MRS Proceedings 316 (1993). http://dx.doi.org/10.1557/proc-316-759.

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ABSTRACTHigh dose Ge implantation into p-type <100> Si wafers at 150 keV has been performed at doses of 3.6×1016, 6.7×1016 and 9.0×1016 cm-2. The Ge distribution and the crystal quality of the implanted layer before and after annealing at various temperatures have been studied by RBS and channelling experiments. It is found that for the medium and high dose samples before annealing, more than 90% of the Ge atoms are in interstitial sites and after annealing at 1000°C, more than 50% of the Ge atoms have become substitutional. The situation is better for the low dose sample where less than 70% of the Ge atoms are in interstitial sites before annealing and about 80% of them become substitutional after annealing at 1000°C. The ESR spectra of these samples are of lorentzian shape with a g-value of about 2.007 and a spin density of about 6×1016 cm-3. The ESR signals of these samples have been inferred to be mainly due to Si-dangling bonds in the GeSi alloy layer and can be eliminated by annealing at 1000°C for 10 minutes. Electrical characterization of the GeSi layer by spreading resistance profiling technique shows that the implantation damage has been extended deep into the substrate before annealing. After annealing at 1000°C, these defects are removed but the spreading resistance of the surface GeSi layer is found to remain higher than that of the substrate.

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37

"Rainbows from ellipsoidal water drops." Proceedings of the Royal Society of London. Series A: Mathematical and Physical Sciences 438, no. 1903 (August 8, 1992): 397–417. http://dx.doi.org/10.1098/rspa.1992.0115.

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New features of the primary rainbow have been revealed in recent experiments by Marston and co-workers in which light is incident on levitated water drops. The drops are oblate spheroids. This paper provides a treatment of the problem by geometrical optics, using the principles of catastrophe optics. It predicts analytically the axial ratios of the drops necessary to produce certain landmark features of the caustics, such as two hyperbolic umbilic foci on the equatorial plane, two kinds of lips events and two E 6 catastrophes. The sequence of caustics produced as the axial ratio of a water drop is changed is shown to be organized by two higher-order singularities which would correspond to drops of refractive index 2 and axial ratios of 1 and √⅔ respectively. The unfoldings of these two higher singularities explain qualitatively all the significant events for a water drop. They also lead to the prediction that two previously unsuspected hyperbolic umbilic foci will be formed in the vertical plane of symmetry when the spheroid is prolate with axial ratio 1.625. Rainbow scattering, that is, the formation of caustics, can occur whenever photons or other particles are scattered by atomic nuclei, atoms, molecules or crystals. Ion channelling through crystals, and the scattering of atoms and molecules by crystal surfaces are examples. The approach described here, of locating higher organizing centres, is equally applicable throughout this broader field.

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38

Elliman, R. G., and I. V. Mitchell. "Room Temperature Damage, Annealing and Dislocation Growth in Silicon." MRS Proceedings 373 (1994). http://dx.doi.org/10.1557/proc-373-469.

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AbstractThe concentration of residual defects produced by self ion implantation of silicon has been shown to be a sensitive function of implantation temperature at temperatures near room temperature. In this study samples were heated to temperatures of 20°C and 60°C and implanted with 540 keV Si ions to a fluence of 2x1015Si.cm-2 using a constant scanned ion flux of 0.2 μA.cm-2. The resultant primary defect concentrations, measured by Rutherford backscattering spectrometry and channelling (RBS-C), were 2.3±0.1x1022 cm-l and 1.8±0.2x1021 cm-3, respectively, i.e. a reduction by a factor of σ13 for a temperature increase of 40°C. Such differences were not evident in the concentration of secondary defects formed by annealing these samples at 900°C for 15 minutes: the defect concentrations were equal within the experimental uncertainties of the RBS-C and transmission electron microscopy (TEM) measurements. This result appears to lead to the surprising conclusion that the number of displaced atoms that survive high temperature annealing to form extended defects is largely independent of the dynamic annealing processes operating during implantation but depends instead on parameters which scale with the ion fluence.

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39

Lippold, G., K. Weinert, M. V. Yakushev, R. D. Pilkington, K. Otte, and W. Grill. "A Raman Scattering, Ion Channelling and Photoluminescence Study of Argon Ion Radiation Damage in Cu(Ga,In)Se2 - Dose Dependence and Dose Rate Effects." MRS Proceedings 540 (1998). http://dx.doi.org/10.1557/proc-540-85.

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AbstractThe ternary chalcopyrite semiconductor CuInSe2 and related ternary compounds are promising materials for the production of high-efficiency thin film solar cells. In this paper we study the dose dependence of ion radiation damage produced by 30 keV and 80 keV Ar ions in single crystals and polycrystalline films of Cu(In,Ga)Se 2 over a wide dose range from 1012 to 1017 cm-2, using Raman spectroscopy and ion channeling measurements. For the first time, we also report on the dose rate dependence with a variation of the beam current density in the range 0.44 to 44 µcm-2. Even for low damage levels no significant dependence of the defect concentration or damage mechanism on the dose rate could be observed. From phonon correlation length considerations we estimate defect densities. They are in agreement with ion channeling data obtained in the 1015 to 1016 dose range, where the breakdown of the lattice structure occurs. In this dose range, the defect density is close to the concentration of implanted atoms. We conclude, that this high impurity concentration is responsible for the amorphization.

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