Ching-Yao Fong
Professor
Ph.D. - University of California, Berkeley, 1968
Theoretical condensed matter physics
My research interests can be classified into three main categories:
(A) Applying first-principles methods to explore structural, electronic and magnetic properties of novel materials, (B) Developing new first-principle algorithms to realistically study quantum structures, such as superlattices, and quantum dots, that are more powerful than existing methods, and (C) Applying a new empirical potential for silicon (Si), the Consorte-Fong potential, to carry out large scale molecular dynamics simulations involving Si atoms. Specifically,
For (A), the following areas of research are being carried out: (1) We design new materials by predicting their structural, electronic and magnetic properties for technological usages. We focus on transition metal compounds with a simple crystal structure, the zincblende structure. However, they possess half-metallic properties which are ideal for spintronic applications. It is very exciting to know that experimental evidence has shown the extreme reliability of our predictions. (2) We perform microscopic calculations on biological systems, especially on models of DNA, to study the proximity effects of foreign atoms near a DNA molecule and the effect of doping in DNA on the electronic properties of this most basic biological system. (3) We investigate microscopic processes for the growth of semiconductors. Surfactant mediated growth is one of the areas in experimental surface sciences still using much guesswork, i.e. by trial and error. Our objective is to formulate guidelines for the choice of surfactants on particular surfaces by first carrying out detailed first-principles calculations to identify the microscopic roles played by the surfactants. Then, we synthesize our results to form guidelines. (4) Molecular solids, like pentacene, are another extremely potential class of candidates for making future electronic devices. We are adding new algorithms to our existing first-principles codes to make them more powerful in treating these promising solids.
For (B), the so-called O(N) method is one of the goals in computational condensed matter physics and materials science to achieve, where N is the number electrons/unit-cell. Comparing to the usual diagonalization schemes to find eigenvalues with cpu in proportional to N3, the cpu of the O(N) method is proportional to N. There are many mathematical and programming issues involved.
For (C), there are still many unresolved puzzles in understanding Si surfaces. It is still difficult to treat surface problems in first-principles. On the other hand, all the existing empirical potentials of Si were determined from bulk properties with each Si atom having four neighbors. When these potentials were applied to Si surface problems, atoms with missing neighbors or with more than four neighbors are not properly characterized. The Consorte-Fong potential resolves this difficulty. We are now applying this potential to study diffusion processes of Si atoms on various Si surfaces, step formations and vibrational modes in Si samples with defects. These topics are directly related to the Si technologies but are remaining to be resolved.
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