A study of high-speed AD and DA converters using redundancy techniques Interim report, May 10, 1963 - May 9, 1964

High speed analog-to-digital converters compared using redundancy encoding technique

Vertical current induced domain wall motion in MgO-based magnetic tunnel junction with low current densities

Shifting electrically a magnetic domain wall (DW) by the spin transfer mechanism is one of the future ways foreseen for the switching of spintronic memories or registers. The classical geometries where the current is injected in the plane of the magnetic layers suffer from a poor efficiency of the intrinsic torques acting on the DWs. A way to circumvent this problem is to use vertical current injection. In that case, theoretical calculations attribute the microscopic origin of DW displacements to the out-of-plane (field-like) spin transfer torque. Here we report experiments in which we controllably displace a DW in the planar electrode of a magnetic tunnel junction by vertical current injection. Our measurements confirm the major role of the out-of-plane spin torque for DW motion, and allow to quantify this term precisely. The involved current densities are about 100 times smaller than the one commonly observed with in-plane currents. Step by step resistance switching of the magnetic tunnel junction opens a new way for the realization of spintronic memristive devices

Spiers Memorial Lecture: Molecular mechanics and molecular electronics

We describe our research into building integrated molecular electronics circuitry for a diverse set of functions, and with a focus on the fundamental scientific issues that surround this project. In particular, we discuss experiments aimed at understanding the function of bistable [2]rotaxane molecular electronic switches by correlating the switching kinetics and ground state thermodynamic properties of those switches in various environments, ranging from the solution phase to a Langmuir monolayer of the switching molecules sandwiched between two electrodes. We discuss various devices, low bit-density memory circuits, and ultra-high density memory circuits that utilize the electrochemical switching characteristics of these molecules in conjunction with novel patterning methods. We also discuss interconnect schemes that are capable of bridging the micrometre to submicrometre length scales of conventional patterning approaches to the near-molecular length scales of the ultra-dense memory circuits. Finally, we discuss some of the challenges associated with fabricated ultra-dense molecular electronic integrated circuits

Tunnel switch diode based on AlSb/GaSb heterojunctions

We report on tunnel switch diodes based on AlSb barriers and GaSb p–n junctions grown by molecular beam epitaxy. These were the devices with thyristor like switching in the GaSb/AlSb system. The characteristic "S" shaped current–voltage curve was found to occur for structures with AlSb barriers less than 300 Å thick. The switching voltage and current density exhibited less sensitivity to barrier and epilayer thickness than was predicted by the punch-through model. The results were correlated with drift diffusion simulations which have been modified to account for the presence of a tunneling contact

The Measurement of AM noise of Oscillators

The close-in AM noise is often neglected, under the assumption that it is a minor problem as compared to phase noise. With the progress of technology and of experimental science, this assumption is no longer true. Yet, information in the literature is scarce or absent. This report describes the measurement of the AM noise of rf/microwave sources in terms of Salpha(f), i.e., the power spectrum density of the fractional amplitude fluctuation alpha. The proposed schemes make use of commercial power detectors based on Schottky and tunnel diodes, in single-channel and correlation configuration. There follow the analysis of the front-end amplifier at the detector output, the analysis of the methods for the measurement of the power-detector noise, and a digression about the calibration procedures. The measurement methods are extended to the relative intensity noise (RIN) of optical beams, and to the AM noise of the rf/microwave modulation in photonic systems. Some rf/microwave synthesizers and oscillators have been measured, using correlation and moderate averaging. As an example, the flicker noise of a low-noise quartz oscillator (Wenzel 501-04623E) is Salpha = 1.15E-13/f, which is equivalent to an Allan deviation of sigma_alpha = 4E-7. The measurement systems described exhibit the world-record lowest background noise.Comment: 39 pages, 22 figures, 8 tables, 21 references, list of symbol