/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

Effect of continuum resonances on electronic transport in quantum wells

In this paper we present a method for numerically solving the Schrodinger equation for the problem of electron transmission through a quantum device defined on a two-dimensional domain. An important aspect of our formulation is the treatment of the boundary conditions at the contact–device interfaces, allowing the problem to be discretized on the device domain only. With the FEM aproach that we employ, the nature of the potential field does not effect the computational expense (for smoothly varying fields). We examine a sample problem of a symmetric cavity in a wave-guide structure.

The numerical simulation of electron transmission through a two-dimensional quantum device by the finite element method

Power dissipation is one of the most important factors limiting the development of integrated circuits. This work will explore the limits of energy dissipation in computation and show that there is no “Landauer Limit” at k B T ln2 as long as information is preserved. Experimental data is presented that demonstrates a dissipation of 0.04 k B T, well below k B T ln2. Simulation results for adiabatically clocked reversible circuits are presented showing dramatic reductions of power dissipation.

There is no Landauer Limit: Experimental tests of the Landauer principle

Devices based on the quantum-dot cellular automata (QCA) computational approach (Lent et al, 1993) use interacting quantum dots to encode and process binary information. In this transistorless approach to computation, logic levels are represented by the configurations of single electrons in coupled quantum-dot systems. In the last few years, significant progress has been made towards the realization of basic QCA elements. However, in these devices, power gain needed for the operation of large QCA arrays was not possible since the only source of energy was the signal input. Recent theoretical work (Lent and Tougaw, 1997) proposed clocked control of the QCA circuitry. Clocked controlled QCA systems have many advantages such as power gain, reduced power dissipation, and pipelined architectures. The original theoretical work applied only to semiconductor implementation of clocked QCA arrays, but recently a scheme for clocked control of metallic QCA cells was proposed (Toth and Lent, 1999; Korotkov and Likharev, 1998). Here an extra dot placed between the two dots of the QCA half-cell acts as a tunable barrier controlled by the clock signal. We present the experimental demonstration of a clocked QCA cell. The device consists of two capacitively coupled half-cells, where each half-cell consists of three micron-size Al islands separated by tunnel junctions, and four electrometers to measure the charge state of the half-cells. The half-cells are leadless, with no DC connection to the environment.

Experimental studies of clocked quantum-dot cellular automata devices

A coherence vector formalism is used to describe quantum computing with quantum-dot cellular automata, and the realizations of basic quantum gates are also discussed.

/pdf/quantum-computing-with-quantum-dot-cellular-automata-using-4mq7afne1k.pdf

Craig S. Lent

Papers

Effect of continuum resonances on electronic transport in quantum wells

The numerical simulation of electron transmission through a two-dimensional quantum device by the finite element method

There is no Landauer Limit: Experimental tests of the Landauer principle

Experimental studies of clocked quantum-dot cellular automata devices

Quantum computing with quantum-dot cellular automata using coherence vector formalism