Surface reconstruction in CaF2/Si(001) investigated by scanning tunneling microscopy

Touru Sumiya, Tadao Miura, Haruko Fujinuma, Shun Ichiro Tanaka

Research output: Contribution to journalArticlepeer-review

15 Citations (Scopus)

Abstract

Scanning tunneling microscopy (STM) has been used to study the initial growth stages of calcium fluoride (CaF2) on Si(001)-(2 × 1) surfaces in situ. At high coverage, the deposited CaF2 molecules nucleate into small hemispherical islands at room temperature, which are of the order of 1 to 3 nm in diameter and cover the Si(001) surface homogeneously. Annealing this surface at 520°C produces a drastic change in the surface morphology. Due to the increased mobility of the deposited CaF2 molecules, they rearrange into long and narrow islands typically of a few nm width and whose length is often more than four times the width. The long, narrow islands grow three-dimensionally, and their long axes are aligned along [110] or [110] of the substrate Si lattice. Increasing the substrate temperature to about 610°C induces a shape transition of the islands from long and narrow to two-dimensional layers. The STM image shows that the layers consist of rows aligned with respect to the underlying Si(001) lattice. Considering the coverage of the deposited CaF2 molecules, the row-like layers are not reconstructed Si(001) surfaces induced by CaF2 adsorption, but are layers that are formed initially in the CaF2 heteroepitaxial growth on a Si(001) surface. STM images clearly show that the terraces are completely covered with row-like layers at 670°C. The formation of the row-like layers can be attributed to the chemical reaction between CaF2 and Si. The perpendicular spacing between adjacent rows varies from 0.8 to 2.4 nm. Thus, it is suggested that the inhomogeneous row-like layers will prevent growth of CaF2 films with high crystalline quality on Si(001).

Original languageEnglish
Pages (from-to)192-204
Number of pages13
JournalSurface Science
Volume376
Issue number1-3
DOIs
Publication statusPublished - 1997 Apr 10
Externally publishedYes

Keywords

  • Calcium fluoride
  • Scanning tunneling microscopy
  • Semiconductor-insulator interfaces
  • Surface structure, morphology, roughness, and topography

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Surfaces, Coatings and Films
  • Materials Chemistry

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