/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

Standard CMOS technology discards all signal energy during every switching cycle, leading to heat generation that limits the operating speed and the achievable computing performance. Energy-recovery schemes avoid the heat generation, but are often burdened with the cost of significant increase in system complexity and the lack of automated design tools. In this paper, we propose to implement adiabatic CMOS circuits utilizing split-level rails and Bennett clocking, which enable energy-recovery in standard CMOS logic gates with only minor modifications. Using a pessimistic 32 nm bulk MOSFET technology model, a switching energy improvement factor of approximately 10X can be reached over standard CMOS, while we predict that emerging low-leakage transistor technologies potentially enable adiabatic energy improvements up to four orders-of–magnitude over the standard approach. The significant end-result of our method is that we can leverage the huge number of existing standard gate libraries and logic designs for energy-recovery circuits. We outline an approach to integrate the automatic generation of the adiabatic circuits into the standard circuit design flow, including standard gate logic synthesis and place-and-route.

/pdf/adiabatic-cmos-limits-of-reversible-energy-recovery-and-15yb3iqi70.pdf

Adiabatic CMOS: Limits of Reversible Energy Recovery and First Steps for Design Automation

/pdf/clocked-quantum-dot-cellular-automata-circuits-1two9c0zcp.pdf

Clocked Quantum-dot Cellular Automata circuits

Zhirnov, Cavin, and co-workers ZC presented in Ref. 1 an analysis of the fundamental limits of a binary switch, represented by a double well system, which purported to show that such a switch must dissipate kBT log 2 because the switching event must dissipate an energy equal to the barrier height. We showed in Ref. 2 that their argument was incorrect because by switching the system smoothly using the adiabatic paradigm of Landauer and Bennett, dissipation much lower than kBT log 2 could be achieved. The barrier height must indeed be much larger than kBT log 2 when the device holds a bit of information but can be lowered in the switching process in such a way that much less energy needs to be dissipated. ZC argued in Refs. 4 and 5 that the apparent energy saved by adiabatic switching would in fact be dissipated in the electrodes that create the adiabatically changing barriers. In an argument in Ref. 5, invoking “Cavin’s demon” to charge a capacitor, they claimed that even smoothly adiabatically charging and discharging the capacitance representing the barrier-created electrodes would inevitably dissipate more than kBT log 2 . Because Landauer’s principle LP clearly contradicts this, they argue in Ref. 5 that LP only applies to “hypothetical” systems that are “perfectly isolated from the external environment.” Our results in Ref. 6 show by direct measurement that a capacitor can in fact be charged and discharged adiabatically. The energy stored on the capacitor can be much larger than kBT log 2 while the dissipated energy is much less than kBT log 2 . This precisely contradicts the “Cavin’s demon” argument of Ref. 5 and supports LP. To argue as they do in their Comment that this is somehow off-point because it focuses on charging and discharging a capacitor is incorrect. We quote their paper third page as follows:

Response to “Comment on ‘Fundamental limits of energy dissipation in charge-based computing’ ” [Appl. Phys. Lett. 98, 096101 (2011)]

https://www3.nd.edu/~lent/pdf/nd/Temperature_dependence_of_the_locked_mode_in_a_single-electron_latch.pdf

Temperature dependence of the locked mode in a single-electron latch

We calculate the band structure of a long ballistic channel whose width is modulated periodically in the presence of a perpendicular magnetic field. The channel is narrowed on one side only, the other wall remaining straight. At zero magnetic field, the periodic modulation of the width produces miniband gaps. As the magnetic field is increased, the gaps disappear. The band structure at high fields consists of free‐electron‐like bands associated with magnetic edge states, and flatbands associated with localized Landau levels. The asymmetry in the walls causes electrons moving through the channel in one direction to have a different effective mass from electrons moving in the opposite direction.

Craig S. Lent

Papers

Adiabatic CMOS: Limits of Reversible Energy Recovery and First Steps for Design Automation

Clocked Quantum-dot Cellular Automata circuits

Response to “Comment on ‘Fundamental limits of energy dissipation in charge-based computing’ ” [Appl. Phys. Lett. 98, 096101 (2011)]

Temperature dependence of the locked mode in a single-electron latch

Bloch states of electrons in a corrugated quantum channel in a magnetic field