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IBM Journal of Research and Development

Issue 3 • Date July 1964

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Displaying Results 1 - 25 of 27
  • Foreword

    Page(s): 214
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    Freely Available from IEEE
  • Crystal Chemistry and Band Structures of the Group V Semimetals and the IV–VI Semiconductors

    Page(s): 215 - 227
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    Some simple facts regarding crystal structures and semiconducting vs semimetallic behavior of the Group V elements and the related Group IV–VI compounds are summarized. The simple chemical interpretation of these facts (based on three perpendicular p-bonding orbitals) is reviewed. This picture is reinterpreted in terms of a simple pseudopotential band model, which provides a deeper basis for understanding the simple chemical notions. The results of various band structure calculations are presented in detail in order to make explicit the direct relation between band and bond pictures as well as between crystal structures and semimetallic vs semiconducting behavior. The calculations also provide information as to probable locations of valence and conduction band edges. View full abstract»

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  • The Effective g-factor of Holes in Bismuth

    Page(s): 228 - 231
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    Measurements have been made of the Shubnikov-de Haas effect in bismuth at 1.5°K and fields up to 88 kG. The effect consists of oscillations in the resistance as a function of magnetic field. The oscillations result from the quantization of the transverse energy of the carriers in a magnetic field. From the positions of the oscillations, one can obtain information concerning the band structure. In the present investigation, we have obtained values of the g-factors for holes in bismuth and have determined the variation of Fermi energy as a function of magnetic field. First an outline of the theory will be presented and then the results. View full abstract»

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  • High Field Galvanomagnetic Effects in Bismuth

    Page(s): 232
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    Spin splitting of the Landau levels due to the holes in bismuth has been observed in pulsed fields up to 175 kilogauss at 1.2°K. The effect was seen in Shubnikovde Haas oscillations. The oscillatory component of the transverse magnetoresistance R versus the magnetic field H is shown in Fig. 1 with J parallel to the bisectrix axis and H in the binary-trigonal plane. θ is the angle between H and the binary axis. The arrows show how rapidly the spin splitting of the levels increases as the field is tipped away from the binary axis. The oscillatory magnetoresistance when H is almost parallel to the trigonal axis is shown in Fig. 2. The splitting factor A (equal to the ratio of spin splitting to the Landau level separation) is nearly integral in this case. The double peak near 100 kilogauss is thought to be due to the super-position of an unsplit hole level and one of the last electron levels. This conclusion is supported by the temperature variation of the oscillations. The observation of the unsplit hole level suggests that the splitting factor is near two. View full abstract»

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  • Piezo-Resistance and Piezo-Hall Effect in Bismuth

    Page(s): 233
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    The electrical resistivity and Hall coefficient in single crystals of bismuth have been measured as a function of uniaxial stress along the trigonal axis at 4.2°, 77°, and 295°K. The data are analyzed in terms of a two band model to determine the deformation potential components E1 and E2 given by δE0 = E111+ ε22 )+ E2ε33, where E0 is the overlap energy. By combining the results of the present experiment with the measurements of the pressure dependence of the galvanomagnetic effects1 and the value E0 = 0.027 eV, we find E1 = −2.4eV and E2 = +2.5eV. View full abstract»

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  • Phonon Dispersion Curves in Bismuth

    Page(s): 234 - 240
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    Dispersion curves for phonons propagating in the trigonal direction in bismuth at room temperature and at 75°K have been obtained in a neutron inelastic scattering experiment. Observed frequencies (units 1013 rad/sec) at 75°K are as follows: at the zone center, ωTO = 1.40 ± 0.02, ωLO = 1.89 ± 0.02; at the zone boundary in the trigonal direction, ωTA = 0.73 ± 0.01, ωLA = 1.12 ± 0.02, ωTO = 1.91 ± 0.02, ωLO = 2.03 ± 0.02. At room temperature, the observed frequencies were about 1.5 percent lower. Data were also obtained for longitudinal phonons propagating in the binary direction at 75°K. It is interesting to note that the splitting between the zone boundary frequencies for the optical and acoustic branches for each polarization is quite large. This splitting is difficult to understand if bismuth is thought of as a slightly distorted simple cubic lattice. The experimental results may be qualitatively understood if bismuth is considered to be made up of a series of double layers normal to the trigonal axis. The atoms in each double layer form a crinkled hexagonal net with strong, probably covalent, bonds between atoms. The forces between atoms on adjacent double layers are relatively weak. This model is consistent with the easy cleavage of bismuth normal to the trigonal axis. Analysis of the trigonal dispersion curves in terms of a linear chain model indicates that there are significant forces connecting a given atom with atoms situated on the four planes on either side of it. View full abstract»

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  • Transport Properties and Band Structure in Bismuth, Antimony and their Alloys

    Page(s): 241 - 246
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    We shall interpret the galvanomagnetic properties of bismuth, antimony and the Bi-Sb alloy system in terms of bands of carriers known to exist in the pure semimetals. In our interpretation, the new carriers, presumed holes, observed by several investigators in antimony must have slightly warped oblate ellipsoidal energy surfaces to account for the galvanomagnetic data of Juretschke et al, rather than tilted ellipsoidal surfaces. These new holes, together with the well established holes in bismuth and the Shoenberg electrons in both bismuth and antimony, account for the anomalous Hall coefficients of antimony. Consideration of qualitative features of the nearly free electron model of Jones and Harrison suggests that a linear variation of the spatial potential upon alloying bismuth with antimony is sufficient to account for the considerable changes observed in the transport properties of the alloy system. This model also suggests that the conduction band minima in bismuth are located at different points in the Brillouin zone from those in antimony. Experimental support for these hypotheses is discussed. View full abstract»

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  • Cyclotron Resonance and the Fermi Surface of Antimony

    Page(s): 247 - 252
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    A new series of cyclotron resonance experiments has been made on antimony which gave extended information on electron and hole cyclotron masses. Experiments were carried out with the magnetic field in the principal crystal planes of antimony at 1.5°K and with 35 Gc/sec microwave radiation. The magnetic field of cyclotron resonance in certain regions was dependent upon the angle of tip of the magnetic field with respect to the metal surface. These effects were minimized by accurate alignment of the magnetic field along the sample surface. The carriers of two bands were observed. The cyclotron mass of one band, assumed to be the conduction band, was consistent with a tilted-ellipsoidal model for the energy surfaces. The cyclotron mass along the 1′ principal electron ellipsoid axis was measured from data in the binary-trigonal plane to be 0.215 m0. The conduction band ellipsoids were found to have a tilt angle of 36° and mass tensor components: m11=0.068 m0, m22=0.63 m0, m33=0.34 m0, |m23|=0.41 m0. The data indicated three sets of warped ellipsoids for the valence band. The warped ellipsoids were found to have a tilt angle of 4° and mass tensor components: m11=0.093 m0, m22=1.14 m0, m33=0.093 m0, and |m23|=0.082 m0. The cyclotron masses of holes and the measurement of cyclotron resonance at limiting points of the Fermi surface indicated that the hole surfaces probably are deformed from an ellipsoid. View full abstract»

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  • Growth and Transport Properties of Bi-Sb Single Crystal Alloys

    Page(s): 253 - 254
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    Since the details of this investigation are to be published elsewhere,1,2 it is our purpose to only briefly summarize the results here. View full abstract»

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  • Energy Band Structure of Graphite

    Page(s): 255 - 261
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    The energy band structure of graphite is described in the region of the Fermi surfaces by the Slonczewski-Weiss model. The electron and hole Fermi surfaces are highly elongated and are aligned along the six Brillouin zone edges which are parallel to the trigonal axis of the crystal. The energy is a non-parabolic function of wavenumber and the Fermi surfaces are not ellipsoids. Galvanomagnetic, de Haas-van Alphen, and other experiments have established that: the band overlap is about 0.03 to 0.04 eV, the carrier densities of electrons and holes are each about 3 × 1018 cm−3 at low temperatures, the effective masses perpendicular to the trigonal axis are about 0.04 m0 for electrons and 0.06 m0 for holes, and the length-to-width ratio of the Fermi surfaces is about 12. The only important effect not included in the Slonczewski-Weiss model is the correlation of electron motion due to the coulomb interaction. Though this effect is expected to be important a priori, it is not yet clear if it causes important discrepancies between the predictions of the model and the experimental results. View full abstract»

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  • The Fermi Surface of Graphite

    Page(s): 262 - 267
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    Recent magnetoreflection measurements in pyrolytic graphite have been interpreted using the magnetic energy levels obtained from the McClure-Inoue secular equation and the appropriate selection rules for interband transitions. Combining these results with those of the de Haas-van Alphen effect, the band parameters of the Slonczewski-Weiss model have been evaluated and the Fermi surface determined. The magnetoreflection experiment indicates considerable warping of the Fermi surface, particularly for holes. Further experiments to determine this warping more precisely are discussed. View full abstract»

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  • Change in Fermi Surfaces of Graphite by Dilute Acceptor Doping

    Page(s): 268 - 273
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    The effect of doping graphite single crystals with the acceptor boron was studied in the dilute range from ≲0.1 ppm to 0.5% by measurements of the Hall effect and de Haas-van Alphen effect. The transition from a mixed electron and hole conduction in the narrow band overlap region (0.035 eV) to that of a single hole conduction produces a peak in the Hall coefficient that shifts to a lower boron concentration with a decrease in temperature. The increase in hole concentration is accompanied by a rapid decrease in mobility, demonstrating the importance of collision broadening. Preliminary de Haas-van Alphen results tentatively identify the major electron and hole Fermi surfaces by means of the period shift with increasing acceptor concentration. A new, very small ellipsoid-like Fermi surface was discovered. It is aligned along the hexagonal axis, having an anisotropy ratio of 9 with orbital masses of about 0.0023 m0 for H ∥ C and 0.017 m0 for H ⊥ C. Analysis strongly indicates that this surface contains minority holes. Three of these surfaces are considered to be aligned symmetrically like “outriggers” about the major hole surface, producing a total of six in the Brillouin zone. A comparison is made with the cyclotron resonance results and a possible interpretation of these minority Fermi surfaces is presented using the Slonczewski-Weiss band model. View full abstract»

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  • STB Model and Transport Properties of Pyrolytic Graphites

    Page(s): 274 - 275
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    Structure and texture of pyrolytic graphites (PG) make it unlikely that the three dimensional electron-energy bands of ideal graphite would provide an adequate basis for a discussion of electron transport processes over a broad temperature range.1 We propose to demonstrate that a coherent description of PG layer-plane phenomena can be based on a parabolic two band system with cylindrical equal-energy surfaces, which are located around the vertical Brillouin zone edges. In this simple two-band model (STB model), band overlap and effective mass must be interpreted as phenomenological parameters to be derived from experiments on highly heat-treated pure PG; with p-type (boron doped) specimens, the objective is to describe the situation from the shift of the Fermi level, on the assumption that the presence of trapping centers would not inject major perturbations in the band structure. View full abstract»

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  • Alfvén Wave Propagation in Bismuth: Quantum Oscillations of the Fermi Surface

    Page(s): 276 - 283
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    Alfvén wave propagation in single crystal bismuth has been studied as a function of magnetic field to 105 kilogauss for frequencies between 13 and 18 kMc/sec. Small deviations from a linear dependence of wave velocity on magnetic field are found and are interpreted as quantum oscillations in the mass density of carriers. Theory and experiment are compared for the magnetic field along a bisectrix axis and along a two-fold axis. Good agreement is found for the first case, but significant discrepancies exist for the magnetic field along a two-fold axis. View full abstract»

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  • Infrared Reflectivity of Bismuth in the Quantum Limit

    Page(s): 284
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    The infrared reflectivity of Bi in a magnetic field has been investigated between 100 cm−1 and 400 cm−1 in the quantum limit (cyclotron energy comparable to Fermi energy). A sharp decrease in the reflectivity1 occurs at that field at which transitions first become possible between the lowest two Landau levels of the conduction band. Calculations1,2 of the position of the absorption edge using two-band models3,4 agree well with observations and make possible an accurate determination of the Fermi energy as well as cyclotron splittings away from kz = 0. In addition quantum effects strongly influence the position of the reflection minimum near the field-modified plasma frequency. The position of the minimum has been studied for electric fields polarized both perpendicular and parallel to the magnetic field, and comparison will be made with calculations based on two-band models. View full abstract»

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  • Acoustic Plasma Waves in Semimetals

    Page(s): 285 - 290
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    The acoustic plasma wave suffers severe Landau damping for equal-temperature carriers obeying Boltzmann statistics, but can be relatively weakly Landau damped in semimetals if in the propagation direction the Fermi velocities and masses of the two carriers are very unequal. Only the carriers with the smaller Fermi velocity are important in producing collision damping since the other carriers store no appreciable momentum. Some results for many-valley semimetals like bismuth are given, together with a discussion of the problem of exciting and detecting this essentially neutral and longitudinal wave. Experiments undertaken to detect the acoustic plasma wave by transmission through thin wafers of bismuth at 10 Gc/sec have been unsuccessful thus far, but have revealed the existence of a higher velocity wave of weak amplitude that has not yet been identified. A discussion is also given of some magnetic quantum effects that should be associated with the acoustic wave. View full abstract»

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  • Effect of the Self-Magnetic Field on Galvanomagnetic Effects in Bismuth

    Page(s): 291 - 294
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    The magnetoresistance and the Hall coefficient for pure bismuth at 77°K have been calculated to the second order in the self-magnetic field, i.e. current density. The calculations show that the observed dependence of the galvanomagnetic effects on the current density at high currents can be qualitatively explained by the self-magnetic field. However, to obtain quantitative agreement it is necessary to include the contribution of diffusion currents in the calculation. The theory for the self-magnetoresistance, including diffusion, has been carried out for the pre-pinch regime of currents. The resulting curve for the self-magnetoresistance agrees well with the observed one if the scattering times between ellipsoids are taken to be of order 10−9 sec (assuming that the diffusion effects are not dominated by the surface, i.e. that the surface-recombination velocity is sufficiently small). View full abstract»

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  • Non-Ohmic Conduction in Bismuth

    Page(s): 295 - 298
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    The experimentally determined I-V characteristics at large currents at 4.2°, 77°, and 300°K have been found to be nonlinear in both single crystal and wire samples of bismuth. A theory has been formulated which includes self-magnetoresistance, a redistribution of carriers (pinch) and bimolecular bulk and surface recombination. Very little information exists, either experimentally or theoretically, with regard to these recombination mechanisms. A program has been written to numerically solve the equations for various values of the electron-hole recombination time and surface velocity. It is found that the I–V characteristics are dominated by the self-magnetoresistance and vary only slightly for a wide range of the generation-recombination parameters. View full abstract»

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  • Linear and Nonlinear Methods in Pattern Classification

    Page(s): 299 - 307
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    The problem of pattern classification has two highly interactive aspects: (1) the selection of numerical measurements to ‘represent’ the patterns, and (2) the specification of an algorithm to identify patterns, based upon the numerical values of these measurements. The present paper presents the mathematical framework for one attack upon these problems and gives results obtained in some experiments in character recognition. View full abstract»

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  • Magnetically Controlled Variable Logic

    Page(s): 308 - 317
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    Magnetically controlled multipurpose logic provides a great flexibility and compactness. A matrix consisting of 2n saturable magnetic elements for n variable inputs is controlled by an adjacent magnetic pattern recorded on a magnetic medium, which determines the logical function to be performed. Since 22n magnetic patterns enable the performance of 22n logical functions, great flexibility of system operation is possible. The selection of the required magnetic materials is described. Application of the basic system to several special purpose machines is shown. In particular, the design of a computer using microprogramming techniques is described, and the application of this system to various serial and parallel computer operations is discussed. View full abstract»

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  • A New Digital Method of Bit Synchronization Derived from an Analog Theory

    Page(s): 318 - 328
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    This paper discusses a new method of bit synchronization derived from an analog theory to solve the problems involved in receiving a serial train of bits from a remote data communication source. Test results show that accurate frequency and phase information can be derived from the received serial data. The Analog Derived Clock to accomplish this bit synchronization is described, and applications in two-wire (half duplex operation) and four-wire (full duplex operation) communication systems are discussed. Speeds up to 2 Mc/sec using existing digital circuit technology were achieved. The special advantage of the Analog Derived Clock over present clocking techniques is an increase in speed and a reduction in circuitry. View full abstract»

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  • Simulation of a Hydraulic Actuator

    Page(s): 329 - 334
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    A simple mathematical model of a hydraulic actuator is formulated, and the differential equations describing the model are derived. Experimental data and a computational solution of the model are determined. Results correspond favorably with oscilloscope velocity traces; hence the model could serve a useful purpose in mechanical design. View full abstract»

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  • A Note on the Resonant Modes and Spatial Coherency of a Fabry-Perot Maser Interferometer

    Page(s): 335 - 337
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    This communication has considered the case of a Fabry-Perot cavity with light impinging on one end while the field distribution on the other end is observed. It has been shown that if one starts with a wave that can be expanded into the modes of the integral operator, and if the medium in the cavity is passive, more than one mode would be observed at the other end although the amplitude of the dominant mode can be much greater than that of the other modes. It was further shown that if there is present an active medium with sufficient gain there will be only a single mode, and the single mode is necessary and sufficient for complete spatial coherency. View full abstract»

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  • Analysis of a Nondegenerate Two-Photon Giant-Pulse Laser

    Page(s): 338 - 340
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    In a recent article1 to which we shall refer as [S&B], a two-photon laser was proposed and analyzed. This device consists of a cavity resonant at frequency vA and containing ions of type B with an inverted population NB/V between levels separated by an energy difference hvB such that vB = 2vA ; it is necessary that the system not lase at vB, which criterion can be satisfied by low reflectivity of the cavity at frequency vB, by strong parasitic absorption in the laser material near frequency vB, or preferably by a choice of ion such that the transition vB is highly forbidden to a single-quantum process. The authors of [S&B] thus show that a certain priming density of photons of frequency vA will provoke the simultaneous emission from the inverted population NB of pairs of photons vA at a rate exceeding the cavity loss,t he process diverging until the population inversion is eliminated. View full abstract»

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  • IBM Technical Papers Published Recently in Other Journals

    Page(s): 341 - 359
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    Freely Available from IEEE

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The IBM Journal of Research and Development is a peer-reviewed technical journal, published bimonthly, which features the work of authors in the science, technology and engineering of information systems.

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