/pdf/self-assembled-monolayers-of-thiolates-on-metals-as-a-form-1neb0hj3k4.pdf

Self-assembled monolayers of thiolates on metals as a form of nanotechnology.

▪ Abstract Solution phase syntheses and size-selective separation methods to prepare semiconductor and metal nanocrystals, tunable in size from ∼1 to 20 nm and monodisperse to ≤5%, are presented. Preparation of monodisperse samples enables systematic characterization of the structural, electronic, and optical properties of materials as they evolve from molecular to bulk in the nanometer size range. Sample uniformity makes it possible to manipulate nanocrystals into close-packed, glassy, and ordered nanocrystal assemblies (superlattices, colloidal crystals, supercrystals). Rigorous structural characterization is critical to understanding the electronic and optical properties of both nanocrystals and their assemblies. At inter-particle separations 5–100 A, dipole-dipole interactions lead to energy transfer between neighboring nanocrystals, and electronic tunneling between proximal nanocrystals gives rise to dark and photoconductivity. At separations <5 A, exchange interactions cause otherwise insulating ass...

Synthesis and Characterization of Monodisperse Nanocrystals and Close-Packed Nanocrystal Assemblies

The purpose of this article is to describe the basic physical processes involved in the nucleation and growth of thin films of materials on solid surfaces. In this introduction the three modes of crystal growth which are thought to occur on surfaces in the absence of interdiffusion are described, and the relationships between the thermodynamics of adsorption and the kinetics of crystal growth are explored in general terms. This is followed by a brief review of atomistic nucleation theory, explaining the relations of such theories to experimental observables. In the next three sections, recent experimental examples of these three growth modes are given, which are interpreted where possible in terms of nucleation and growth theory. The last section discusses observations on the shapes of growing crystallites and the relation of such observations to nucleation and surface diffusion processes.

https://iopscience.iop.org/article/10.1088/0034-4885/47/4/002/pdf

Nucleation and growth of thin films

The fabrication methods of the microelectronics industry have been refined to produce ever smaller devices, but will soon reach their fundamental limits. A promising alternative route to even smaller functional systems with nanometre dimensions is the autonomous ordering and assembly of atoms and molecules on atomically well-defined surfaces. This approach combines ease of fabrication with exquisite control over the shape, composition and mesoscale organization of the surface structures formed. Once the mechanisms controlling the self-ordering phenomena are fully understood, the self-assembly and growth processes can be steered to create a wide range of surface nanostructures from metallic, semiconducting and molecular materials.

/pdf/engineering-atomic-and-molecular-nanostructures-at-surfaces-2sqr7sjd15.pdf

Engineering atomic and molecular nanostructures at surfaces

“Spintronics,” in which both the spin and charge of electrons are used for logic and memory operations, promises an alternate route to traditional semiconductor electronics. A complete logic architecture can be constructed, which uses planar magnetic wires that are less than a micrometer in width. Logical NOT, logical AND, signal fan-out, and signal cross-over elements each have a simple geometric design, and they can be integrated together into one circuit. An additional element for data input allows information to be written to domain-wall logic circuits.

http://science.sciencemag.org/content/sci/309/5741/1688.full.pdf

Magnetic Domain-Wall Logic

Overcoming the IC power challenge requires signal energy recovery, which can be achieved utilizing adiabatic charging principles and logically reversible computing in the circuit design. This paper demonstrates the energy-efficiency of a Bennett-clocked adiabatic CMOS multiplier via a simulation model. The design is analyzed on the logic gate level to determine an estimate for the number of irreversible bit erasures occurring in a combinatorial implementation, showing considerable potential for minimizing the logical information loss.

/pdf/energy-recovery-and-logical-reversibility-in-adiabatic-cmos-i9fhj41pa9.pdf

Energy recovery and logical reversibility in adiabatic CMOS multiplier

Quantum-dot Cellular Automata (QCA) is a device architecture that uses the position of electrons in quantum-dot arrays to implement digital logic. We present the experimental demonstration of a two-stage QCA shift register and an analysis of errors encountered in its operation.

Experimental demonstration of a QCA shift register and analysis of errors

We examine transport through several quantum electron waveguide geometries. Reflection and mode-mixingin transmission through bends in quantum waveguides are calculated and the impact on interconnections betweendevices discussed. We calculate the current-voltage relationship for a constriction in a quantum waveguide for appliedvoltages beyond linear-response regime. Strong resonance effects in waveguide cavities are found to persist even whencavity geometry is non-abrupt. We demonstrate the existence of current vortices in resonant cavities. 1. Introduction There is ample experimental evidence that a two-dimensional electron gas (2DEG) , created at a heterojunction interface can be further confined electrostatically by depositing a metal gate pattern above the interface [1,2]. The electrons are apparently ballistic and coherent over regions as large as a micron or more. By lithographicallypatterning the metal gate, electrons can be confined to travel in narrow quantum channels which act much like

Quantum-electron waveguides: bends, constrictions, and cavities

The Landauer Principle connects the information theoretic notion of entropy to the physics of statistical mechanics. When a physical system performs a logical operation that erases or loses information, without a copy being preserved, it must transfer a minimum amount of heat, \(k_B T \log (2)\), to the environment. How can there be such a connection between the abstract idea of information and the concrete physical reality of heat? To address this question, we adopt the Jaynes approach of grounding statistical mechanics in the Shannon notion of entropy. Probability is a quantification of incomplete information. Entropy should not be conceived in terms of disorder, but rather as a measure on a probability distribution that characterizes the amount of missing information the distribution represents. The thermodynamic entropy is a special case of the Shannon entropy applied to a physical system in equilibrium with a heat bath so that its average energy is fixed. The thermal probability distribution is obtained by maximizing the Shannon entropy, subject to the physical constraints of the problem. It is then possible to naturally extend this description to include a physical memory device, which must be in a nonequilibrium long-lived metastable state. We can then explicitly demonstrate how the requirement for a fundamental minimum energy dissipation is tied to erasure of an unknown bit. Both classical and quantum cases are considered. We show that the classical thermodynamic entropy is in some situations best matched in quantum mechanics, not by the von Neumann entropy, but by a perhaps less familiar quantity—the quantum entropy of outcomes. The case of free expansion of an ideal quantum gas is examined in this context.

Craig S. Lent

Papers

Energy recovery and logical reversibility in adiabatic CMOS multiplier

Experimental demonstration of a QCA shift register and analysis of errors

Quantum-electron waveguides: bends, constrictions, and cavities

Information and Entropy in Physical Systems

Energy Limits in Computation