Michael R. Scheuermann

Bio: Michael R. Scheuermann is an academic researcher from IBM. The author has contributed to research in topics: Equivalent circuit & Power integrity. The author has an hindex of 17, co-authored 48 publications receiving 1424 citations.

Direct measurement of the superconducting properties of single grain boundaries in Y 1 Ba 2 Cu 3 O 7 − δ

Abstract: We have made the first direct measurements of the critical current density of individual grain boundaries and their adjoining grains in ${\mathrm{Y}}_{1}$${\mathrm{Ba}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathrm{\ensuremath{\delta}}}$ superconducting films. The critical current of the boundary was always found to be less than either of the two grains. The magnetic field dependence of the critical current of the grain boundaries indicates that they are comprised of regions of weak and strong Josephson coupling. A single grain boundary was also used to build and operate a simple dc SQUID. Current-voltage curves of a grain-boundary junction n the finite voltage range show subgap structure.

Thin interface pellicle for dense arrays of electrical interconnects

Abstract: A thin interface pellicle probe for making temporary or permanent interconnections to pads or bumps on a semiconductor device wherein the pads or bumps may be arranged in high density patterns is described incorporating an electrode for each pad or bump wherein the electrode has a raised portion thereon for penetrating the surface of the pad or bump to create sidewalls to provide a clean contact surface and the electrode has a recessed surface to limit the penetration of the raised portion. The electrodes may be affixed to a thin flexible membrane to permit each contact to have independent movement over a limited distance and of a limited rotation. The invention overcomes the problem of making easily breakable electrical interconnections to high density arrays of pads or bumps on integrated circuit structures for testing, burn-in or package interconnect and testing applications.

Physical design of a fourth-generation POWER GHz microprocessor

Abstract: The fourth-generation POWER processor chip contains 170M transistors and includes 2 microprocessor cores, shared L2, directory for an off-chip L3, and all logic needed to interconnect multiple chips to form an SMP. It is implemented in a 0.18 /spl mu/m SOI technology, with 7 layers of Cu interconnect, and functions in systems at 1.1 GHz, and dissipates 115 W at 1.5 V.

Micropatterning of high-tc films with an excimer laser

Abstract: Micron‐wide lines of high Tc Y‐Ba‐Cu‐O have been successfully patterned by ablating the films with a pulsed excimer laser. The high Tc films are mounted onto a computer‐controlled stepping stage and irradiated with a demagnified image of a variable‐size rectangular aperture. This technique has been used for fabricating features ranging from several centimeters in length to submicron in width without any degradation in Tc. For example, a superconducting microstructure of Y‐Ba‐Cu‐O, nominally 1 μm wide and 2.5 μm long, with a Tc (R=0) of 88 K and a Jc of 5×104 A/cm2 at 4.2 K was fabricated.

A Scalable Multi- TeraOPS Deep Learning Processor Core for AI Trainina and Inference

Abstract: A multi-TOPS AI core is presented for acceleration of deep learning training and inference in systems from edge devices to data centers. With a programmable architecture and custom ISA, this engine achieves >90% sustained utilization across the range of neural network topologies by employing a dataflow architecture and an on-chip scratchpad hierarchy. Compute precision is optimized at 16b floating point (fp 16) for high model accuracy in training and inference as well as 1b/2b (bi-nary/ternary) integer for aggressive inference performance. At 1.5 GHz, the AI core prototype achieves 1.5 TFLOPS fp 16, 12 TOPS ternary, or 24 TOPS binary peak performance in 14nm CMOS.

Introduction to the cell multiprocessor

Abstract: This paper provides an introductory overview of the Cell multiprocessor. Cell represents a revolutionary extension of conventional microprocessor architecture and organization. The paper discusses the history of the project, the program objectives and challenges, the disign concept, the architecture and programming models, and the implementation.

The flux-line lattice in superconductors

Abstract: Magnetic flux can penetrate a type-II superconductor in the form of Abrikosov vortices (also called flux lines, flux tubes, or fluxons) each carrying a quantum of magnetic flux phi 0=h/2e. These tiny vortices of supercurrent tend to arrange themselves in a triangular flux-line lattice (FLL), which is more or less perturbed by material inhomogeneities that pin the flux lines, and in high-Tc superconductors (HTSCs) also by thermal fluctuations. Many properties of the FLL are well described by the phenomenological Ginzburg-Landau theory or by the electromagnetic London theory, which treats the vortex core as a singularity. In Nb alloys and HTSCs the FLL is very soft mainly because of the large magnetic penetration depth lambda . The shear modulus of the FLL is c66~1/ lambda 2, and the tilt modulus c44(k)~(1+k2 lambda 2)-1 is dispersive and becomes very small for short distortion wavelengths 2 pi /k<< lambda . This softness is enhanced further by the pronounced anisotropy and layered structure of HTSCs, which strongly increases the penetration depth for currents along the c axis of these (nearly uniaxial) crystals and may even cause a decoupling of two-dimensional vortex lattices in the Cu-O layers. Thermal fluctuations and softening may `melt` the FLL and cause thermally activated depinning of the flux lines or ofthe two-dimensional `pancake vortices` in the layers. Various phase transitions are predicted for the FLL in layered HTSCs. Although large pinning forces and high critical currents have been achieved, the small depinning energy so far prevents the application of HTSCs as conductors at high temperatures except in cases when the applied current and the surrounding magnetic field are small.

Artificial charge-modulationin atomic-scale perovskite titanate superlattices

Abstract: The nature and length scales of charge screening in complex oxides are fundamental to a wide range of systems, spanning ceramic voltage-dependent resistors (varistors), oxide tunnel junctions and charge ordering in mixed-valence compounds. There are wide variations in the degree of charge disproportionation, length scale, and orientation in the mixed-valence compounds: these have been the subject of intense theoretical study, but little is known about the microscopic electronic structure. Here we have fabricated an idealized structure to examine these issues by growing atomically abrupt layers of LaTi(3+)O(3) embedded in SrTi(4+)O(3). Using an atomic-scale electron beam, we have observed the spatial distribution of the extra electron on the titanium sites. This distribution results in metallic conductivity, even though the superlattice structure is based on two insulators. Despite the chemical abruptness of the interfaces, we find that a minimum thickness of five LaTiO(3) layers is required for the centre titanium site to recover bulk-like electronic properties. This represents a framework within which the short-length-scale electronic response can be probed and incorporated in thin-film oxide heterostructures.

The Flux-Line Lattice in Superconductors

Abstract: Magnetic flux can penetrate a type-II superconductor in form of Abrikosov vortices. These tend to arrange in a triangular flux-line lattice (FLL) which is more or less perturbed by material inhomogeneities that pin the flux lines, and in high-$T_c$ supercon- ductors (HTSC's) also by thermal fluctuations. Many properties of the FLL are well described by the phenomenological Ginzburg-Landau theory or by the electromagnetic London theory, which treats the vortex core as a singularity. In Nb alloys and HTSC's the FLL is very soft mainly because of the large magnetic penetration depth: The shear modulus of the FLL is thus small and the tilt modulus is dispersive and becomes very small for short distortion wavelength. This softness of the FLL is enhanced further by the pronounced anisotropy and layered structure of HTSC's, which strongly increases the penetration depth for currents along the c-axis of these uniaxial crystals and may even cause a decoupling of two-dimensional vortex lattices in the Cu-O layers. Thermal fluctuations and softening may melt the FLL and cause thermally activated depinning of the flux lines or of the 2D pancake vortices in the layers. Various phase transitions are predicted for the FLL in layered HTSC's. The linear and nonlinear magnetic response of HTSC's gives rise to interesting effects which strongly depend on the geometry of the experiment.

Tunnelling effects on surface bound states in unconventional superconductors

Abstract: Recent studies on high-Tc superconductors have aroused new interest in tunnelling effects in unconventional superconductors. Unlike in conventional s-wave superconductors, the d-wave pairing state in these materials has an internal phase of the pair potential. The internal phase as a function of the wavevector of the Cooper pairs has a large influence on the electric properties of tunnelling junctions. Important effects of the internal phase on the Josephson current were first predicted theoretically. The idea has been established through several experiments using high-Tc Josephson junctions, which detect ?-phase shift between the a- and b-axis directions and fractional flux quanta. These results give convincing evidence for d-wave symmetry in high-Tc superconductors. In addition, the existence of new interference effects in the quasiparticle states near surfaces and boundaries has been suggested through theoretical predictions. Experimentally, a large number of tunnelling spectroscopy data showed zero-bias conductance peaks (ZBCPs), the origin of which cannot be explained in terms of the classical concept that a tunnelling conductance spectrum is a phase-insensitive probe of the electronic states. It is clarified theoretically that the observed ZBCPs reflect the formation of zero-energy states on the surface due to the ?-phase shift of internal phase in the d-wave pairing symmetry. The formulation developed for tunnelling spectroscopy suggests that tunnelling spectroscopy is essentially phase sensitive. In addition, the formation of the bound states has been shown to have a serious influence on the electrical properties of Josephson junctions. Several anomalous properties including strong enhancement of the Josephson current in the low-temperature region have been predicted theoretically. In this report, recent developments in tunnelling effects on surface bound states in unconventional superconductors are reviewed.