Showing papers by "Y. A. Chang published in 2002"
TL;DR: The features of PANDAT, a software package for multicomponent phase diagram calculation, and its calculation engine, PanEngine, are discussed.
Abstract: PANDAT is a software package for multicomponent phase diagram calculation. Given a set of thermodynamic parameters for all phases in a system and a set of user constraints, PANDAT automatically calculates the stable phase diagram without requiring either prior knowledge of the diagram or special user skills. The features of PANDAT are discussed and some application examples presented. In addition to PANDAT, its calculation engine, PanEngine, is also discussed.
346 citations
TL;DR: In this article, a new micromodel was developed to predict the microstructure and microsegregation in multicomponent alloys during dendritic solidification, which was directly coupled with phase diagram calculations using a user friendly and robust phase diagram calculation engine.
58 citations
TL;DR: In this article, a novel approach was used to characterize the site occupancies and point defect concentrations in the B2-ordered (Ni,Fe) single phase field over a wide range of composition and temperature.
55 citations
TL;DR: The growth of uniaxial structures occurs because the different crystal structures of ErSi2 and Si have a good lattice match along one Si crystallographic axis but a significant mismatch along the perpendicular Si axis as mentioned in this paper.
Abstract: Sub-monolayer amounts of Er deposited onto Si (001)react with the substrate to form epitaxial nanowires of crystalline ErSi2. The growth of uniaxial structures occurs because the different crystal structures of ErSi2 and Si have a good lattice match along one Si crystallographic axis but a significant mismatch along the perpendicular Si axis. The nucleation, growth, and subsequent evolution of ErSi2 nanowires were investigated as functions of erbium coverage on the Si (001) surface, annealing time, and annealing temperature. Low annealing temperatures (620 °C) and times (5 min) produced ErSi2 nanowires with widths of a few nanometers, heights less than one nanometer, and lengths of several hundred nanometers. For longer annealing times at low temperature, the surface roughened without significant ripening of the wires. Annealing at intermediate temperatures (∼700 °C) caused stacking faults to form along the long axis of the nanowires and their lengths to ripen. At high temperature (800 °C), the wires broke apart into short segments with stacking faults.
35 citations
TL;DR: A review of point defect and solute hardening in binary and ternary B2 intermetallics can be found in this article, where the authors used the ALCHEMI (atom location by channeling enhanced microanalysis) technique combined with vacancy measurements.
Abstract: This paper provides a review of recent progress on point defect and solute hardening in binary and ternary B2 intermetallics. As is the case for disordered metallic solutions, the presence of point defects and solute atoms in ordered intermetallic compounds results in solid solution hardening (SSH). However, factors unique to ordered systems are often responsible for unusual hardening effects. Binary compounds with identical crystal structures can exhibit significantly different hardness behavior. Ternary solute additions to ordered compounds can give rise to apparent solid solution softening as well as unexpectedly rapid hardening. These effects arise from the interaction of multiple defect types as well as the presence of multiple sublattice sites available for solute occupation. Therefore, before the SSH behavior of ordered intermetallics can be properly studied, it is necessary to develop an understanding of the types and quantities of the point defects which are present. Three recent studies by the authors are reviewed. Much of the work was done on NiAl and FeAl in binary form as well as with ternary additions. Defect concentrations over wide ranges in alloy composition and quenching temperature were determined using the ALCHEMI (atom location by channeling enhanced microanalysis) technique combined with vacancy measurements. Hardness values were also measured. It was found that most of the observed SSH effects could be rationalized on the basis of the measured point defect concentrations.
TL;DR: PdAl was selected as a reactive contact to n-(In0.52Al0.48)As with the intention of forming a thin, AlAs-enriched interlayer of graded (In1−xAlx)As semiconductor alloy, following rapid thermal annealing as discussed by the authors.
Abstract: PdAl was selected as a reactive contact to n-(In0.52Al0.48)As with the intention of forming a thin, AlAs-enriched interlayer of graded (In1−xAlx)As semiconductor alloy, following rapid thermal annealing. Selection of PdAl was based on the experimentally established existence of a quasi-reciprocal phase relationship. A Schottky barrier enhancement of 0.07 eV (measured by current-voltage (I-V)) and 0.09 eV (measured by capacitance-voltage (C-V)) was found following a 1-min anneal at 450°C. High-resolution transmission electron microscopy (HRTEM) examination showed the presence of an edge dislocation in the interlayer alloy, suggesting an enrichment of AlAs. Schottky barrier enhancement is in qualitative agreement with the prediction of the combined thermodynamic/kinetic model.