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The article looks at the application of a numerical code in the Thermoelectroelastic Simulation of semiconductor GaN-based electronic devices. Topics include GaN's piezoelectric properties, high electron mobility transistor (HEMT) structures, and radio frequency (RF) devices. Aluminium gallium nitride (AlGaN) is also discussed.

The aqueous self-assembly of methyl-terminated tri(oxyethylene)thiol-encapsulated gold nanoclusters of varying core size is demonstrated on micrometer scale Au/SiO2 interdigital electrodes. This self-assembly process consists of alternate exposures of the substrate to solutions of either an α,ω-dithiol or the gold nanoclusters, resulting in the deposition of these materials onto the electrode surface. A comparison of the procedure in both H2O and CHCl3 solvents shows that the assembly, as monitored by the electrical conductivity of the device, occurs more rapidly in the H2O system. This observation is complimented by XPS and UV/Vis measurements, which show that (1) the increased current is due to an increased amount of gold deposited on the surface under aqueous conditions and (2) the thiol exchange reaction occurs more rapidly in H2O in comparison to CHCl3.

A shadow mask technique employing V2O5 nanowires and ion-beam milling is used to define narrow lines of monolayer-encapsulated Au nanoclusters. When positioned between electrodes these lines are shown to be conducting and to have nonlinear I−V characteristics with nonzero threshold voltages consistent with Coulomb blockade.

A series of gold nanoclusters stabilized by ligands containing short ethylene oxide oligomers of fixed length were prepared and characterized. The thiols CH3(OCH2CH2)nSH (where n = 2, 3, and 4) were substituted onto the surface of 1.8-nm hexanethiol-capped gold clusters by a thiol-exchange reaction, and the resulting nanoclusters were characterized by NMR, FTIR, and UV/vis spectroscopies; TGA; and TEM analysis. A degree of ligand exchange greater than 99% was achieved, and the gold core diameter remained unchanged in the final material. Of particular interest, the cluster with n = 2 was water-insoluble, whereas those with n = 3 or 4 were water-soluble. The thin-film electrical conductivities of these clusters were compared with those of alkanethiol-capped clusters of similar chain lengths and found to be roughly 1 order of magnitude greater. In a chemical vapor sensor configuration, this series of clusters displayed strong electrical responses that showed a correlation between the length of the ethylene oxide ligand and the polarity of the vapor.

A class of "fully-Lagrangian" methods for solving systems of conservation equations is defined. The key step in formulating these methods is the definition of a new set of field variables for which Lagrangian discretization is trivial. Recently popular lattice-Boltzmann simulation schemes for solving such systems are shown to be a useful sub-class of these fully-Lagrangian methods in which (a) the conservation laws are satisfied at each grid point, (b) the Lagrangian variables are expanded perturbatively, and (c) discretization error is used to represent physics. Such schemes are typically derived using methods of kinetic theory. Our numerical analysis approach shows that the conventional physical derivation, while certainly valid and fruitful, is not essential, that it often confuses physics and numerics and that it can be unnecessarily constraining. For example, we show that lattice-Boltzmann-like methods can be non-perturbative and can be made higher-order, implicit and/or with non-uniform grids. Furthermore, our approach provides new perspective on the relationship between lattice-Boltzmann methods and finite-difference techniques. Among other things, we show that the lattice-Boltzmann schemes are only conditionally consistent and in some cases are identical to the well-known Dufort-Frankel method. Through this connection, the lattice-Boltzmann method provides a rational basis for understanding Dufort-Frankel and gives a pathway for its generalization. At the same time, that Dufort Frankel is no longer much used suggests that the lattice-Boltzmann approach might also share this fate. Copyright 1994, 1999 Academic Press

We present a theoretical study and discussion of computationally useful nanoelectronic circuits which use adaptive control methods both to achieve the circuit function and to compensate for unpredictable nonuniformities in the circuit environment. In the regime where the scaling of conventional digital electronics breaks down, nanoelectronic circuitry will be required to perform robustly in the presence of inevitable device–device interactions, sensitivity to circuit parameters of quantum devices, and deviations from ideal circuit design. To examine the role of adaption in addressing these issues, we focus on a specific class of scaleable circuit architectures composed of Coulombically interacting polarizable anisotropic quantum dots which include input polarization dots, output polarization dots, and an array of processing dots. We implement the adaptive control of these circuits by assuming that particular features of the processing dots such as energy barriers, charge, shape, or orientation can be experimentally modified. A method of adaptive feedback is used to modify the processing dots and produce desired correlations between the input and output dot polarizations as computed by the circuit. A variational quantum Monte Carlo method has been used to simulate the many-body response of model GaAs dot circuits in which the mutual orientation of the dots is adapted to successfully achieve different desired patterns of correlation. We demonstrate the robustness of the adaptive circuits for circuit nonuniformities and for sensitivity to circuit parameters due to quantum effects.

The possibility of using single-electron digital circuits (SEDCs) to achieve ultra-high performance digital signal processing is explored. SEDCs are highly-scalable Coulomb blockade-based circuits that operate in the discrete limit where bits are represented by single electrons. Such circuits are well-suited to implementing bit-level systolic processing algorithms because the local connectivity of systolic arrays translates into locally-interconnected hardware. By relieving interconnect bandwidth limitations this enables circuits that can fully exploit the extreme scaling possible with the single-electron devices. Errors associated with co-tunneling, thermal fluctuations, etc. are an important issue in single-electron circuits, especially for a digital application. The systolic arrays are, however, amenable to simple error-correction techniques which may make computing with these unreliable components possible. Nevertheless, it must be emphasized that realization of these complex circuits depends on tremendous advances in fabrication technology, particularly to meet their stringent uniformity requirements.

The article discusses the mobility enhancement in strained antimonide quantum wells. It mentions that designing circuits used for digital and mixed-signal applications, can minimize the power consumption. It further discusses a study conducted to investigate mobility enhancement by strain, through fabrication of transistors on both types of two heterostructures. Two figures depicting the study are also presented.