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SY Li

Publications and source records attributed to SY Li.

5 recordsLinked to original sources
PubMed2000

A practical simulated annealing program and its application to quantitative CBED pattern matching

A modified simulated annealing (SA) program is presented (source code available from the authors). The program was used for the refinement procedure in quantitative convergent beam diffraction (QCBED). Considering the practical situation in QCBED, three modifications have been made to the conventional SA algorithm. First, a most probable search boundary (MPB) was suggested, which guarantees the program to search mainly within the MPB, but allows it also to go out of the boundary sometimes. Secondly, the MPB was set to shrink during the minimization. This algorithm decreases the computing time significantly. Thirdly, a more meaningful stop criterion was adopted using the nominal physical precision of each refinement parameter. The feasibility and the efficiency of the modified program were tested using both calculated and experimental CBED patterns. The presented program is proved to be capable of high performance.

Journal Article↗
PubMed2000

Plan-view imaging of oxygen-induced reconstruction on Ag(110) surface. I. The possibility of imaging surface oxygen

Surface reconstruction on Ag(110) induced by oxygen adsorption was studied by the plan-view imaging technique of high-resolution electron microscopy (HREM). Systematic multislice simulations were carried out to find the optimal experimental conditions for imaging the surface oxygen. It was found theoretically that there exist a series of characteristic values of objective lens defoci and sample thicknesses under which the surface and the bulk can be imaged clearly and simultaneously. These optimal imaging conditions were used to interpret the experimental micrographs. While the basic features of the surface reconstruction of O/Ag(110) in the HREM images are consistent with those revealed by scanning tunnelling microscopy (STM), there are some new features that have not been reported with STM. These phenomena give some evidence to the existence of subsurface oxygen.

Journal Article↗
PubMed2000

Plan-view imaging of oxygen-induced reconstruction on Ag(110) surface. II. Effect of high-energy electron thinning

The feasibility and the limitation of the 'high-energy electron thinning' method for the production of surface-science-grade samples in situ in the electron microscope are studied. Exploiting the electron beam supplied by high-voltage electron gun in electron microscope, this method can be readily realized. An obvious advantage of this method is that we can monitor the sample surface concurrently. However, this sample preparation method depends strongly on the sample material and the local environment within the electron microscope. Factors relating to the electron thinning speed are briefly discussed.

Journal Article↗
PubMed2000

Measurement of Debye-Waller factors in Co3Ti by quantitative CBED

The Debye-Waller factors (DWFs) of Co and Ti atoms in Co3Ti have been obtained by quantitative convergent-beam electron diffraction (QCBED). They are B(Co) = 0.20-0.24 and BTi = 0.41-0.43 A2 in Co3Ti at room temperature. A modified simulated-annealing algorithm and its parallel algorithm were employed to obtain reliable results efficiently.

Journal Article↗