Structure Analysis Of Si Research Articles

Structure analysis of Si(100)2 × n surfaces by ion channeling and blocking spectroscopy

It was reported that phases of Si(100)2 × n structures (6 < n < 10) were formed on a clean surface by quenching at temperatures higher than 800 ° C. These results were explained by ordered phases of missing-dimer defects. On the other hand, it was found by our experiment that the Si(100)2 × n structures were induced by Ni contamination. Appearance of the 2 × n structures and variation of n were closely correlated with the surface Ni concentration which depended on quenching temperature and cooling rate. In the present experiment, variations of the surface Ni concentration with heat treatments are measured by He + ion channeling spectroscopy. The quantitative surface concentrations of Ni impurity in the Si(100)2 × n structures are estimated and the striking change in the Ni surface concentration caused by quenching from different temperatures is discussed.

Surface structure analysis of Si(111)√3 × √3-Bi by X-ray diffraction — Approach to the solution of the phase problem

Abstract X-ray intensity versus energy ( I - E ) curves of the integral-order rods have been observed for the Si(111) 3 × 3 −Bi structure under nearly normal incidence condition, and the 3-dimensional structure of the surface has been analyzed by utilizing the interference effect between the X-rays diffracted from the surface atoms and the bulk crystal around the Bragg points, which gives information on the positions of the surface atoms, especially of the heavy atoms with respect to the bulk crystal. Bi atoms, forming a trimer with an interatomic distance of 3.08±0.08 A , are bonded to the first-layer Si atoms by means of the dangling bonds, and the displacements of the first- and second-layer Si atoms from their ideal positions are less than 0.15 A. The spacing between the Bi layer and the ideal first Si layer is 2.68±0.02 A . A Si adatom layer making a honeycomb structure exists 0.80±0.20 A above the Bi layer. The model in which the center of the trimer is on the second-layer Si atoms rather than on the fourth-layer Si atoms is favored.

Structure analysis of Si(111)-7×7 reconstructed surface by transmission electron diffraction

Structure analysis of Si(111)-7×7 reconstructed surface by transmission electron diffraction

Structure analysis of Si(111)-7 × 7 reconstructed surface by transmission electron diffraction

The atomic structure of the 7 × 7 reconstructed Si(111) surface has been analysed by ultra-high vacuum (UHV) transmission electron diffraction (TED). A possible projected structure of the surface is deduced from the intensity distribution in TED patterns of normal electron incidence and from Patterson and Fourier syntheses of the intensities. A new three-dimensional structure model, the DAS model, is proposed: The model consists of 12 adatoms arranged locally in the 2 × 2 structure, a stacking fault layer and a layer with a vacancy at the corner and 9 dimers on the sides of each of the two triangular subcells of the 7 × 7 unit cell. The silicon layers in one subcell are stacked with the normal sequence, CcAaB + adatoms, while those in the other subcell are stacked with a faulted sequence, CcAa/C + adatoms. The model has only 19 dangling bonds, the smallest number among models so far proposed. Previously proposed models are tested quantitatively by the TED intensity. Advantages and limits of the TED analysis are discussed.

Structure analysis of Si(111)2©1 with low-energy electron diffraction

A structure analysis of the Si(111)2\textcopyright{}1 surface is performed using extensive new low-energy electron-diffraction data (12 beams). Although the $\ensuremath{\pi}$-bonded chain model in its original form shows gross disagreement with low-energy electron diffraction, a modification of that structure gives moderate agreement. The major modifications are a buckling in the outer chain and an overall compression.