Biomedical subjects

Yanfa Yan

Publications and source records attributed to Yanfa Yan.

2 recordsLinked to original sources

PubMed2006

Grain-boundary physics in polycrystalline CuInSe2 revisited: experiment and theory.

Current studies have attributed the remarkable performance of polycrystalline CuInSe2 (CIS) to anomalous grain-boundary (GB) physics in CIS. The recent theory predicts that GBs in CIS are hole barriers, which prevent GB electrons from recombining. We examine the atomic structure and chemical composition of (112) GBs in Cu(In,Ga)Se2 (CIGS) using high-resolution Z-contrast imaging and nanoprobe x-ray energy-dispersive spectroscopy. We show that the theoretically predicted Cu-vacancy rows are not observed in (112) GBs in CIGS. Our first-principles modeling further reveals that the (112) GBs in CIS do not act as hole barriers. Our results suggest that the superior performance of polycrystalline CIS should not be explained solely by the GB behaviors.

Journal Article↗

PubMed2004

Quasicrystals as cluster aggregates.

Quasicrystals are solids that exhibit symmetries long thought forbidden in nature. Since their discovery in a rapidly solidified Al-Mn alloy in 1984, the central issue in the field has been to understand why they form. Are they energetically stable compounds or stabilized by entropy? In recent years, major strides have been made in determining atomic structure, largely by direct imaging using advanced electron microscopy. One system is now known to be energetically stabilized, and quasicrystals are therefore firmly established as a new physical state of matter. They represent a unique packing of atomic clusters some tens of atoms in size, with substantial localized fluctuations, referred to as phasons. Understanding phasons may in future allow their unique macroscopic properties to be tailored for useful materials applications.

Crystallization↗