Michael Niemier

On-Chip Clocking for Nanomagnet Logic Devices

We report local control of nanomagnets that can be arranged to perform computation in a cellular automata-like architecture. This letter represents the first demonstration of deterministically placed quantum-dot cellular automata (QCA) devices (of any implementation), where devices are controlled by on-chip local fields.

Problems in designing with QCAs: Layout = Timing

SUMMARY The quantum cellular automata (QCA) is currently being investigated as an alternative to CMOS VLSI. While some simple logical circuits and devices have been studied, little if any work has been done in considering the architecture for systems of QCA devices. This work discusses the progress of one of the rst such eorts. Namely, the design of dataow components for a simple microprocessor being designed exclusively in QCA are discussed. Problems associated with initial designs and enumerated solutions to these problems (usually stemming from oorplanning techniques) are explained. Finally, areas of future research direction for circuit design in QCA are presented. Copyright ? 2001 John Wiley & Sons, Ltd.

Clocking structures and power analysis for nanomagnet-based logic devices

Logical devices made from nano-scale magnets have many potential advantages - systems should be non-volatile, dense, low power, radiation hard, and could have a natural interface to MRAM. Initial work includes experimental demonstrations of logic gates and wires and theoretical studies that consider their power dissipation. This paper looks at power dissipation too, but also considers the circuitry needed to drive a computation. Initial results are very encouraging and indicate that clocked magnetic logic could - in the worst case - match equivalent low power CMOS circuits and - in the best-case - potentially provide more than 2 orders of magnitude improvement when one considers energy per operation.

Exploring and exploiting wire-level pipelining in emerging technologies

Pipelining is a technique that has long since been considered fundamental by computer architects. However, the world of nanoelectronics is pushing the idea of pipelining to new and lower levels — particularly the device level. How this affects circuits and the relationship between their timing, architecture, and design will be studied in the context of an inherently self-latching nanotechnology termed Quantum Cellular Automata (QCA). Results indicate that this nanotechnology offers the potential for “free” multi-threading and “processing-in-wire”. All of this could be accomplished in a technology that could be almost three orders of magnitude denser than an equivalent design fabricated in a process at the end of the CMOS curve.

A design of and design tools for a novel quantum dot based microprocessor

Despite the seemingly endless upw ards spiral of modern VLSI technology, many experts are predicting a hard w all for CMOS in about a decade. Given this, researc hers con tin ue to look at alternative technologies, one of which is based on quan tumdots, called quan tumcellular automata (QCA). While the first such devices have been fabricated, little is kno wn about how to design complete systems of them. This paper summarizes one of the first such studies, namely an attempt to design a complete, albeit simple, CPU in the technology. T o design a theoretical QCA microprocessor, two things must be accomplished. First a device model of the processor must be constructed (i.e. the schematic itself). Second, methods for sim ulatingand testing QCA designs m ust be developed. This paper summarizes the beginnings of a simple QCA microprocessor (namely, its dataflow) and a QCA design and simulation tool.

Shape Engineering for Controlled Switching With Nanomagnet Logic

We demonstrate that in circuits and systems that comprised of nanoscale magnets, magnet-shape-dependent switching properties can be used to perform Boolean logic. More specifically, by making magnets with slanted edges, we can shift the energy barrier of the device (i.e., so that it is not at a maximum when a device is magnetized along its geometrically hard axis). In clocked systems, we can leverage this barrier shift to make and or or gates that are not majority based. Advantages include reduced gate footprint and interconnect overhead as we eliminate one gate input. In this paper, we report and discuss micromagnetic simulations that illustrate how magnet shape can facilitate nonmajority-gate-based, reduced footprint logic; preliminary fabrication and testing results that illustrate that shape engineering can induce energy barrier shifts; and additional micromagnetic simulations that show other ways in which we might leverage shape in circuits made from nanoscale magnets.

Eliminating wire crossings for molecular quantum-dot cellular automata implementation

When exploring computing elements made from technologies other than CMOS, it is imperative to investigate the effects of physical implementation constraints. This paper focuses on molecular quantum-dot cellular automata circuits. For these circuits, it is very difficult for chemists to fabricate wire crossings (at least in the near future). A novel technique is introduced to remove wire crossings in a given circuit to facilitate the self assembly of real circuits - thus providing meaningful and functional design targets for both physical and computer scientists. The technique eliminates all wire crossings with minimal logic gate/node duplications. Experimental results based on existing QCA circuits and other benchmarks are quite encouraging, and suggest that further investigation is needed.

Experimental Demonstration of Fanout for Nanomagnetic Logic

Nanomagnet logic (NML) shows great promise as an alternative to conventional digital architectures. We present the first experimental demonstration of fanout using magnetizations of nanomagnets in the NML scheme. Specifically, we show magnetic force microscopy images of functioning fanout circuits.

Fabricatable Interconnect and Molecular QCA Circuits

When exploring computing elements made from technologies other than complementary metal-oxide-semiconductor, it is imperative to investigate circuits and systems assuming realistic physical implementation constraints. This paper looks at molecular quantum-dot cellular automata (QCA) devices within this context. With molecular QCA, physical coplanar wire crossings may be very difficult to fabricate in the near to midterm. Here, we consider how this will affect interconnect. We introduce a novel technique to remove wire crossings in a given design in order to facilitate the self-assembly of real circuits - thus, providing meaningful and functional design targets for both physical and computer scientists. The proposed methodology eliminates all wire crossings with minimal logic gate/node duplications. Simulation results based on existing QCA circuits and other benchmarks are presented, and suggest that further investigation is needed.

Analog Circuit Design Using Tunnel-FETs

Tunnel-FET (TFET) is a major candidate for beyond-CMOS technologies. In this paper, the properties of the TFETs that affect analog circuit design are studied. To demonstrate how TFETs can enhance the performance or change the topology of the analog circuits, several building blocks such as operational transconductance amplifiers (OTAs), current mirrors, and track-and-hold circuits are examined. It is shown that TFETs are promising for low-power and low-voltage designs, wherein transistors are biased at low-to-moderate current densities. Comparing 14-nm III-V TFET-based OTAs with Si-MOSFET-based designs demonstrates up to 5 times reduction in the power dissipation of the amplifiers and more than an order of magnitude increase in their DC voltage gain. The challenges and opportunities that come with the special characteristics of TFETs, namely asymmetry, ambipolar behavior, negative differential resistance, and superlinear operation are discussed in detail.