Anisotropy of the electron spectra of the cleavage surface (100) of layered In₄Se₃ crystals

Chem. Met. Alloys 4 (2011) 63-66

https://doi.org/10.30970/cma4.0154

Pavlo V. GALIY, Taras M. NENCHUK, Ostap R. DVERIY, Yaroslav B. LOSOVYJ

It is shown from angle resolved ultraviolet photoemission spectroscopy that the ordered surfaces of the In₄Se₃ (100) system exhibit anisotropy of the electron spectra (i.e. discernable and significant valence band dispersion), both parallel and perpendicular to the cleavage plane. Parallel to the cleavage plane, the electron spectra differ along the crystallographic axes b and c. Band widths (extent of dispersion) of @ 1 eV are observed along the surface chain rows and about 0.5 eV perpendicular to the surface “furrows”. The downward dispersion (towards greater binding energy) of the band at the valence band maximum, away from the G point, can be understood since this band is dominated by In-s and Se-p_y bonds. The band widths of 0.3 to 0.4 eV perpendicular to the chain direction (G-Y) and 1.25 eV along the chain direction (G-X), for bands within the valence region, are in line with the expectations from the calculated band structure.

(a) Schematic crystal structure of In₄Se₃. The lattice constants of the crystal structure are: a = 15.296(1) Å, b = 12.308(1) Å, c = 4.0806(5) Å; space group Pnnm; the structure is dominated by (In₃)⁵⁺ multivalent clusters bonded to selenium through ionic covalent bonds. The cleavage direction is indicated by the triangle in the upper left; (b) STM image of a 30×30 nm² crystal fragment of the interlayer cleavage (100) surface of In₄Se₃, corresponding to the crystal structure (a) and 2D/3D In chain along the x direction (lattice spacing c) is indicated.

Keywords

Layered crystals / Angle resolved ultraviolet photoemission spectroscopy / Electron spectra / In₄Se₃